Emerging Epigenetic Targets and Their Molecular Impact on Vascular Remodeling in Pulmonary Hypertension

Pulmonary Hypertension (PH) is a terminal disease characterized by severe pulmonary vascular remodeling. Unfortunately, targeted therapy to prevent disease progression is limited. Here, the vascular cell populations that contribute to the molecular and morphological changes of PH in conjunction with current animal models for studying vascular remodeling in PH will be examined. The status quo of epigenetic targeting for treating vascular remodeling in different PH subtypes will be dissected, while parallel epigenetic threads between pulmonary hypertension and pathogenic cancer provide insight into future therapeutic PH opportunities.

Altered Smooth Muscle Cell Histone Acetylome by the SPHK2/S1P Axis Promotes Pulmonary Hypertension

BACKGROUND

Epigenetic regulation of vascular remodeling in pulmonary hypertension (PH) is poorly understood. Transcription regulating, histone acetylation code alters chromatin accessibility to promote transcriptional activation. Our goal was to identify upstream mechanisms that disrupt epigenetic equilibrium in PH.

METHODS

Human pulmonary artery smooth muscle cells (PASMCs), human idiopathic pulmonary arterial hypertension (iPAH):human PASMCs, iPAH lung tissue, failed donor lung tissue, human pulmonary microvascular endothelial cells, iPAH:PASMC and non-iPAH:PASMC RNA-seq databases, NanoString nCounter, and cleavage under targets and release using nuclease were utilized to investigate histone acetylation, hyperacetylation targets, protein and gene expression, sphingolipid activation, cell proliferation, and gene target identification. SPHK2 (sphingosine kinase 2) knockout was compared with control C57BL/6NJ mice after 3 weeks of hypoxia and assessed for indices of PH.

RESULTS

We identified that Human PASMCs are vulnerable to the transcription-promoting epigenetic mediator histone acetylation resulting in alterations in transcription machinery and confirmed its pathological existence in PH:PASMC cells. We report that SPHK2 is elevated as much as 20-fold in iPAH lung tissue and is elevated in iPAH:PASMC cells. During PH pathogenesis, nuclear SPHK2 activates nuclear bioactive lipid S1P (sphingosine 1-phosphate) catalyzing enzyme and mediates transcription regulating histone H3K9 acetylation (acetyl histone H3 lysine 9 [Ac-H3K9]) through EMAP (endothelial monocyte activating polypeptide) II. In iPAH lungs, we identified a 4-fold elevation of the reversible epigenetic transcription modulator Ac-H3K9:H3 ratio. Loss of SPHK2 inhibited hypoxic-induced PH and Ac-H3K9 in mice. We discovered that pulmonary vascular endothelial cells are a priming factor of the EMAP II/SPHK2/S1P axis that alters the acetylome with a specificity for PASMC, through hyperacetylation of histone H3K9. Using cleavage under targets and release using nuclease, we further show that EMAP II-mediated SPHK2 has the potential to modify the local transcription machinery of pluripotency factor KLF4 (Krüppel-like factor 4) by hyperacetylating KLF4 Cis-regulatory elements while deletion and targeted inhibition of SPHK2 rescues transcription altering Ac-H3K9.

CONCLUSIONS

SPHK2 expression and its activation of the reversible histone H3K9 acetylation in human pulmonary artery smooth muscle cell represent new therapeutic targets that could mitigate PH vascular remodeling.

Enhancing gastric cancer conventional chemotherapy effects by triple angiokinase inhibitor nintedanib in preclinical models

Background

Gastric adenocarcinoma (GAC) is the fourth leading cause of cancer death worldwide. Systemic chemotherapy is a preferred treatment option for advanced and recurrent GAC, but response rates and survival prolongation remain limited. Tumor angiogenesis plays a critical role in GAC growth, invasion and metastasis. We investigated the antitumor efficacy of nintedanib, a potent triple angiokinase inhibitor for VEGFR-1/2/3, PDGFR-α/β and FGFR-1/2/3, alone or in combination with chemotherapy, in preclinical models of GAC.

Methods

Animal survival studies were performed in peritoneal dissemination xenografts in NOD/SCID mice using human GAC cell lines MKN-45 and KATO-III. Tumor growth inhibition studies were performed in subcutaneous xenografts in NOD/SCID mice using human GAC cell lines MKN-45 and SNU-5. The mechanistic evaluation involved Immunohistochemistry analyses in tumor tissues obtained from subcutaneous xenografts. In vitro cell viability assays were performed using a colorimetric WST-1 reagent.

Results

In MKN-45 GAC cell-derived peritoneal dissemination xenografts, animal survival was improved by nintedanib (33%), docetaxel (100%) and irinotecan (181%), while oxaliplatin, 5-FU and epirubicin had no effect. The addition of nintedanib to docetaxel (157%) or irinotecan (214%) led to a further extension in animal survival. In KATO-III GAC cell-derived xenografts carrying FGFR2 gene amplification, nintedanib extended survival by 209%. Again, the addition of nintedanib further enhanced the animal survival benefits of docetaxel (273%) and irinotecan (332%). In MKN-45 subcutaneous xenografts, nintedanib, epirubicin, docetaxel and irinotecan reduced tumor growth (range: 68-87%), while 5-FU and oxaliplatin had a smaller effect (40%). Nintedanib addition to all chemotherapeutics demonstrated a further reduction in tumor growth. Subcutaneous tumor analysis revealed that nintedanib attenuated tumor cell proliferation, reduced tumor vasculature and increased tumor cell death.

Conclusion

Nintedanib showed notable antitumor efficacy and significantly improved taxane or irinotecan chemotherapy responses. These findings indicate that nintedanib, alone and in combination with a taxane or irinotecan, has the potential for improving clinical GAC therapy.

Abstract 480: Enhancing chemotherapy response by telotristat ethyl, an inhibitor of tryptophan hydroxylase involved in serotonin synthesis, in cholangiocarcinoma

Objective: Cholangiocarcinoma (CCA) is a highly aggressive biliary tract cancer (BTC). CCAs are divided into three subtypes: intrahepatic (iCCA, 10-20%), perihilar (pCCA, 50-60%) or distal (dCCA, 20-30%). CCA has a very poor prognosis with a 5-year survival rate of 5-15%. The majority of CCA patients (~80%) present with unresectable disease where gemcitabine plus cisplatin (GemCis) is the standard treatment with a median survival of 14 months. Nanoparticle albumin-bound (nab) paclitaxel (NPT) is an approved treatment for breast cancer, NSCLC and pancreatic cancer that is under clinical investigation for several solid tumors including CCA. Increased accumulation and secretion of serotonin have been reported to support its oncogenic activity in CCA. Telotristat ethyl (TE) is an inhibitor of tryptophan hydroxylase 1 (TPH1) that mediates peripheral serotonin synthesis. We investigated the therapeutic efficacy of TE in combination with standard chemotherapies in preclinical models of CCA.

Methods: Tumor growth studies were performed in subcutaneous cell-derived xenografts (CDX) using human CCLP-1 cells (iCCA), TFK-1 cells (dCCA), SNU-1196 cells (pCCA) in NOD/SCID mice, and in patient-derived xenografts (PDX) in NSG mice. Animal survival studies were performed in peritoneal dissemination xenografts in NOD/SCID mice using iCCA CCLP-1 cells. Intratumoral proliferation and serotonin levels were determined by immunohistochemistry (IHC).

Results: In peritoneal dissemination xenografts, animal survival was markedly enhanced by NPT (60%), while TE (11%) or GemCis (9%) had a marginal effect. The combination of TE with GemCis (26%) or NPT (68%) exhibited a further increase in animal survival. In iCCA xenografts, tumor growth inhibition by TE was 53%, and NPT (69%) caused greater inhibition than GemCis (53%). In dCCA xenografts, tumor growth inhibition by TE was 51%, and NPT (56%) was more effective than GemCis (37%). In pCCA xenografts, tumor growth reduction by TE, NPT and GemCis was 41%, 67% and 58%. In all three cell-derived xenografts, TE combination with chemotherapy demonstrated an improved tumor growth inhibition effect (range: 67-90%). In PDX studies, TE markedly inhibited tumor growth (range: 40-73%), and GemCis caused a greater reduction (range: 80-86%) than NPT (57-76%). Again, an additive effect was observed with the combination of TE and chemotherapy. In all CDX and PDX subcutaneous tumors, reduction in tumor cell proliferation, measured by Ki67 staining, corresponded with tumor growth inhibition data. Further, decreased levels of serotonin were observed by TE treatment in all CDX and PDX tumors.

Conclusion: In several CCA preclinical models, TE exhibited marked antitumor efficacy and it enhanced GemCis or NPT chemotherapy response. Hence, combination therapies with TE have the potential to improve clinical CCA therapy.

Citation Format: Lily Darman, Margaret A. Schwarz, Roderich Schwarz, Niranjan Awasthi. Enhancing chemotherapy response by telotristat ethyl, an inhibitor of tryptophan hydroxylase involved in serotonin synthesis, in cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 480.

Augmenting Experimental Gastric Cancer Activity of Irinotecan through Liposomal Formulation and Antiangiogenic Combination Therapy

Gastric adenocarcinoma (GAC) is the third most common cause of cancer-related deaths worldwide. Combination chemotherapy remains the standard treatment for advanced GAC. Liposomal irinotecan (nal-IRI) has improved pharmacokinetics (PK) and drug biodistribution compared with irinotecan (IRI, CPT-11). Angiogenesis plays a crucial role in the progression and metastasis of GAC. We evaluated the antitumor efficacy of nal-IRI in combination with novel antiangiogenic agents in GAC mouse models. Animal survival studies were performed in peritoneal dissemination xenografts. Tumor growth and PK studies were performed in subcutaneous xenografts. Compared with controls, extension in animal survival by nal-IRI and IRI was >156% and >94%, respectively. The addition of nintedanib or DC101 extended nal-IRI response by 13% and 15%, and IRI response by 37% and 31% (MKN-45 xenografts); nal-IRI response by 11% and 3%, and IRI response by 16% and 40% (KATO-III xenografts). Retardation of tumor growth was greater with nal-IRI (92%) than IRI (71%). Nintedanib and DC101 addition tend to augment nal-IRI or IRI response in this model. The addition of antiangiogenic agents enhanced tumor cell proliferation inhibition effects of nal-IRI or IRI. The tumor vasculature was decreased by nintedanib (65%) and DC101 (58%), while nal-IRI and IRI alone showed no effect. PK characterization in GAC xenografts demonstrated that compared with IRI, nal-IRI treatment groups had higher retention, circulation time, and tumor levels of CPT-11 and its active metabolite SN-38. These findings indicate that nal-IRI, alone and in combination with antiangiogenic agents, has the potential for improving clinical GAC therapy.

Abstract 1052: Augmentation of standard chemotherapy response by inhibition of Aurora kinase A in preclinical models of pancreatic cancer

Background: The prognosis of pancreatic ductal adenocarcinoma (PDAC) is very poor with a 5-year survival rate of 8%. Current standard chemotherapeutic treatment nab-paclitaxel (NPT) plus gemcitabine (Gem) has been able to give an average prognosis of 8.5 months after detection. Aurora Kinase A (AURKA), an enzyme responsible for the regulation of cytokinesis, is mutated in over 55% of PDAC. Increased expression of AURKA inhibits metabolic stress-induced autophagy, thus promoting cell survival. Additionally, amplification of AURKA has been shown to lead to taxane resistance. Through inhibition of AURKA signaling with a small-molecule inhibitor alisertib (MLN8237, ALS), we evaluated an enhancement of NPT+Gem chemotherapy response in PDAC.

Methods: In vitro cell proliferation was evaluated in PDAC-associated cell lines by WST-1 assay. Protein expression was measured by Immunoblot analysis. Tumor growth and survival studies were performed using human PDAC cells AsPC-1 in NOD/SCID mice. Intratumoral mechanism of action was determined by IHC and Immunoblot analysis.

Results: In AsPC-1 subcutaneous xenografts, chemotherapy regimen (NPT+Gem) and alisertib inhibited tumor growth while their combination exhibited an additive effect. The increase in tumor size was 255 mm3 in controls, 105 mm3 after NPT+Gem, 133 mm3 after ALS and 38 mm3 after NPT+Gem+ALS treatment. In peritoneal dissemination xenografts, animal survival was 23 days in controls that was increased by NPT+Gem (41 days, 78% increase), ALS (25 days, 9% increase) and NPT+Gem+ALS exhibited an additive effect (49 days, 113% increase). NPT+Gem and ALS effect on tumor cell proliferation and apoptosis corresponded with subcutaneous tumor growth data. In vitro proliferation analysis of PDAC epithelial cells (AsPC-1, Panc-1), stromal cells and endothelial cells demonstrated that NPT+Gem and ALS inhibited cell proliferation and their combination treatment had an additive effect. Immunoblot analysis of PDAC cells showed increased levels of cleaved caspase-3 and cleaved PARP-1 in combination therapy pointing to increased levels of apoptosis with NPT+Gem+ALS treatment in all cell lines tested.

Conclusion: These findings demonstrate that nab-paclitaxel plus gemcitabine standard chemotherapy response can be enhanced through specific inhibition of aurora kinase A signaling by alisertib in PDAC. The data support the potential of this combinatorial therapeutic strategy for clinical PDAC therapy.

Citation Format: David Kronenberger, Margaret A. Schwarz, Md Sazzad Hassan, Urs von Holzen, Roderich E. Schwarz, Niranjan Awasthi. Augmentation of standard chemotherapy response by inhibition of Aurora kinase A in preclinical models of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1052.

Targeted FGFR/VEGFR/PDGFR inhibition with dovitinib enhances the effects of nab-paclitaxel in preclinical gastric cancer models

Standard chemotherapy regimens for gastric adenocarcinoma (GAC) have limited efficacy and considerable toxicity profiles. Nab-paclitaxel has shown promising antitumor benefits in previous GAC preclinical studies. Dovitinib inhibits members of the receptor tyrosine kinase family including FGFR, VEGFR and PDGFR, and has exhibited antitumor effects in many solid tumors including GAC. Based on the antimitotic, antistromal and EPR effects of nab-paclitaxel, we investigated augmentation of nab-paclitaxel response by dovitinib in multiple GAC preclinical models. In MKN-45 subcutaneous xenografts, inhibition in tumor growth by nab-paclitaxel and dovitinib was 75% and 76%, respectively. Dovitinib plus nab-paclitaxel had an additive effect on tumor growth inhibition and resulted in tumor regression (85% of its original value). Dovitinib monotherapy resulted in minimal improvement in animal survival (25 days) compared to control (23 days), while nab-paclitaxel monotherapy or dovitinib plus nab-paclitaxel combination therapy led to a clinically significant lifespan extension of 83% (42 days) and 187% (66 days), respectively. IHC analysis of subcutaneous tumors exhibited reduced tumor cell proliferation and tumor vasculature by dovitinib. In vitro studies demonstrated that dovitinib and nab-paclitaxel individually reduced tumor cell proliferation, with an additive effect from combination therapy. Immunoblot analyses of MKN-45 and KATO-III cells revealed that dovitinib decreased phospho-FGFR, phospho-AKT, phospho-ERK, phospho-p70S6K, phospho-4EBP1, Bcl-2 and increased cleaved PARP-1, cleaved-caspase-3, p27, Bax, Bim, with an additive effect from combination therapy. These results demonstrate that the FGFR/VEGFR/PDGFR inhibitor, dovitinib, has the potential to augment the antitumor effects of nab-paclitaxel, with implications for use in the advancement of clinical GAC therapy.

Therapeutic Potential of the Cyclin-Dependent Kinase Inhibitor Flavopiridol on c-Myc Overexpressing Esophageal Cancer

Tumors with elevated c-Myc expression often exhibit a highly aggressive phenotype, and c-Myc amplification has been shown to be frequent in esophageal cancer. Emerging data suggests that synthetic lethal interactions between c-Myc pathway activation and small molecules inhibition involved in cell cycle signaling can be therapeutically exploited to preferentially kill tumor cells. We therefore investigated whether exploiting elevated c-Myc expression is effective in treating esophageal cancer with the CDK inhibitor flavopiridol. We found frequent overexpression of c-Myc in human esophageal cancer cell lines and tissues. c-Myc overexpression correlated with accelerated esophageal cancer subcutaneous xenograft tumor growth. Esophageal cancer cells with elevated c-Myc expression were found preferentially more sensitive to induction of apoptosis by the CDK inhibition flavopiridol compared to esophageal cancer cells with lower c-Myc expression. In addition, we observed that flavopiridol alone or in combination with the chemotherapeutic agent nanoparticle albumin-bound paclitaxel (NPT) or in combinations with the targeted agent BMS-754807 significantly inhibited esophageal cancer cell proliferation and subcutaneous xenograft tumor growth while significantly enhancing overall mice survival. These results indicate that aggressive esophageal cancer cells with elevated c-Myc expression are sensitive to the CDK inhibitor flavopiridol, and that flavopiridol alone or in combination can be a potential therapy for c-Myc overexpressing esophageal cancer.

Abstract 1043: Enhancing cytotoxic chemotherapy effects by nintedanib in gastric cancer preclinical models

Background: Gastric adenocarcinoma (GAC) remains the 3rd most common cause of cancer mortality in the world. Systemic chemotherapy is a preferred treatment option for advanced and recurrent GAC, but response rates and survival extension remain limited. Tumor angiogenesis plays a critical role in GAC growth, invasion and metastasis. In this study, we determined the antitumor efficacy of nintedanib, a potent triple angiokinase inhibitor for VEGFR-1/2/3, PDGFR-α/β and FGFR-1/2/3, alone or in combination with chemotherapy, in preclinical models of GAC.

Methods: Animal survival and tumor growth studies were performed in 4-6 week-old female NOD/SCID mice with human GAC cell xenografts (MKN-45, KATO-III, SNU-5). The mechanistic evaluation involved Immunohistochemistry and Immunoblot analyses of subcutaneous tumors. In vitro cell viability assays were performed using colorimetric WST-1 reagent.

Results: In MKN-45 cell-derived peritoneal dissemination xenografts, animal survival was improved by nintedanib (33%), docetaxel (100%) or irinotecan (181%), while oxaliplatin, 5-FU and epirubicin had no effect. The addition of nintedanib to docetaxel (157%) or irinotecan (214%) led to a further extension in animal survival. In KATO-III cell-derived xenografts carrying FGFR2 gene amplification, nintedanib monotherapy extended survival much more (209%). Docetaxel and irinotecan effects were again further enhanced by nintedanib. In MKN-45 subcutaneous xenografts, nintedanib, epirubicin, docetaxel or irinotecan reduced tumor growth (range: 68-87%), while 5-FU and oxaliplatin had a smaller effect (40%). The addition of nintedanib to all chemotherapy groups demonstrated a further reduction in tumor growth. Subcutaneous tumor analysis revealed that nintedanib attenuated tumor cell proliferation, reduced tumor vasculature and increased tumor cell death. Nintedanib (10 μM) inhibited in vitro cell proliferation of mutationally different GAC cells by 25% (MKN-45), 75% (KATO-III) or 82% (SNU-5), and confirmed additive inhibitory effects in combinations with chemotherapy agents.

Conclusion: Nintedanib showed notable antitumor efficacy and significantly improved taxane or irinotecan chemotherapy responses. Combination regimens with nintedanib have the potential for improving clinical GAC therapy.

Citation Format: Niranjan Awasthi, Margaret A. Schwarz, Frank Hilberg, Roderich E. Schwarz. Enhancing cytotoxic chemotherapy effects by nintedanib in gastric cancer preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1043.

Abstract 975: Antitumor effect of cyclin- dependent kinase inhibitor flavopiridol in c-Myc overexpressing esophageal cancer

Tumors with elevated c-Myc expression often exhibit highly aggressive phenotype and c-Myc amplification has been shown to be frequent in esophageal cancer. Emerging data suggests that synthetic lethal interactions between c-Myc pathway activation and small molecules inhibition involved in cell cycle signaling can be therapeutically exploited to preferentially kill tumor cells. We therefore investigated whether exploiting a synthetic-lethal approach dependent on elevated c-Myc signaling is effective in treating esophageal cancer with a CDK inhibitor flavopiridol. We found frequent overexpression of c-Myc in esophageal cancer cell lines and tissues. c-Myc overexpression correlated with accelerated esophageal cancer subcutaneous xenograft tumor growth without association with improved overall survival in esophageal cancer patients. c-Myc expression was enhanced by Wnt signaling activator (6-bromoindirubin-3′ -oxime (BIO) or pcDNA3-cMyc and c-Myc expression was depleted by c-Myc siRNAs. Interestingly, esophageal cancer cells with elevated c-Myc expression were preferentially more sensitive to induction of apoptosis by CDK inhibition flavopiridol compared to esophageal cancer cells with lower c-Myc expression. In addition, we observed that flavopiridol alone or in combinations with chemotherapeutic agent nanoparticle albumin-bound paclitaxel (NPT) or in combinations with targeted agent BMS-754807 significantly inhibited esophageal cancer cell proliferation and subcutaneous xenograft tumor growth with significantly enhancing overall mice survival. These results indicate that aggressive esophageal cancer cells with elevated c-Myc expression are sensitive to CDK inhibitor flavopiridol and flavopiridol alone or in combination with cytotoxic or targeted agents can be a potential therapy for c-Myc overexpressing esophageal cancer.

Citation Format: Md Sazzad Hassan, Niranjan Awasthi, Jun Li, Margaret A. Schwarz, Urs von Holzen. Antitumor effect of cyclin- dependent kinase inhibitor flavopiridol in c-Myc overexpressing esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 975.

Targeted dual inhibition of c-Met/VEGFR2 signalling by foretinib improves antitumour effects of nanoparticle paclitaxel in gastric cancer models

Elevated expression of multiple growth factors and receptors including c‐Met and VEGFR has been reported in gastric adenocarcinoma (GAC) and thus provides a potentially useful therapeutic target. The therapeutic efficacy of foretinib, a c‐Met/VEGFR2 inhibitor, was determined in combination with nanoparticle paclitaxel (NPT) in GAC. Animal studies were conducted in NOD/SCID mice in subcutaneous and peritoneal dissemination xenografts. The mechanism of action was assessed by Immunohistochemical and Immunoblot analyses. In c‐Met overexpressing MKN‐45 cell‐derived xenografts, NPT and foretinib demonstrated inhibition in tumour growth, while NPT plus foretinib showed additive effects. In c‐Met low‐expressing SNU‐1 or patient‐derived xenografts, the foretinib effect was smaller, while NPT had a similar effect compared with MKN‐45, as NPT plus foretinib still exhibited an additive response. Median mice survival was markedly improved by NPT (83%), foretinib (100%) and NPT plus foretinib (230%) in peritoneal dissemination xenografts. Subcutaneous tumour analyses exhibited that foretinib increased cancer cell death and decreased cancer cell proliferation and tumour vasculature. NPT and foretinib suppressed the proliferation of GAC cells in vitro and had additive effects in combination. Further, foretinib caused a dramatic decrease in phosphorylated forms of c‐Met, ERK, AKT and p38. Foretinib led to a decrease in Bcl‐2, and an increase in p27, Bax, Bim, cleaved PARP‐1 and cleaved caspase‐3. Thus, these findings highlight the antitumour impact of simultaneous suppression of c‐Met and VEGFR2 signalling in GAC and its potential to enhance nanoparticle paclitaxel response. This therapeutic approach might lead to a clinically beneficial combination to increase GAC patients’ survival.

A shift from glycolytic and fatty acid derivatives toward one-carbon metabolites in the developing lung during transitions of the early postnatal period

During postnatal lung development, metabolic changes that coincide with stages of alveolar formation are poorly understood. Responding to developmental and environmental factors, metabolic changes can be rapidly and adaptively altered. The objective of the present study was to determine biological and technical determinants of metabolic changes during postnatal lung development. Over 118 metabolic features were identified by liquid chromatography with tandem mass spectrometry (LC-MS/MS, Sciex QTRAP 5500 Triple Quadrupole). Biological determinants of metabolic changes were the transition from the postnatal saccular to alveolar stages and exposure to 85% hyperoxia, an environmental insult. Technical determinants of metabolic identification were brevity and temperature of harvesting, both of which improved metabolic preservation within samples. Multivariate statistical analyses revealed the transition between stages of lung development as the period of major metabolic alteration. Of three distinctive groups that clustered by age, the saccular stage was identified by its enrichment of both glycolytic and fatty acid derivatives. The critical transition between stages of development were denoted by changes in amino acid derivatives. Of the amino acid derivatives that significantly changed, a majority were linked to metabolites of the one-carbon metabolic pathway. The enrichment of one-carbon metabolites was independent of age and environmental insult. Temperature was also found to significantly influence the metabolic levels within the postmortem sampled lung, which underscored the importance of methodology. Collectively, these data support not only distinctive stages of metabolic change but also highlight amino acid metabolism, in particular one-carbon metabolites as metabolic signatures of the early postnatal lung.

Abstract 553: Antitumor efficacy of a liposomal formulation of irinotecan in preclinical gastric cancer models: Augmenting its response by antiangiogenic agents

BACKGROUND: Gastric adenocarcinoma (GAC) remains the 3rd most common cause of cancer-related deaths worldwide. Systemic chemotherapy is commonly a fundamental treatment for metastatic GAC that usually leads to a modest patient benefit, resulting in a 5-year survival rate of 31%. A liposomal formulation of irinotecan (nal-IRI) has shown improved pharmacokinetic and drug biodistribution compared with free irinotecan (IRI) in preclinical studies. Angiogenesis plays a crucial role in the progression and metastasis of GAC. We evaluated the therapeutic efficacy of nal-IRI in combination with nintedanib, a tyrosine kinase inhibitor targeting FGFR, PDGFR and VEGFR, and DC101, a monoclonal antibody targeting VEGFR2 in preclinical models of GAC.

METHODS: In vitro cell proliferation was evaluated in three GAC cell lines (MKN-45, KATO-III and SNU-5) by WST-1 assay. Protein expression was measured by Western blot analysis in MKN-45 cell lysates. Animal survival studies were performed using two cell lines MKN-45 and KATO-III cells in peritoneal dissemination models in NOD/SCID mice (n=5-7). Tumor growth and pharmacokinetic studies were performed in GAC cell-derived xenografts. Mechanistic evaluation included IHC and Immunoblot analysis in tumor tissues.

RESULTS: Animal survival was increased by nal-IRI (>156%) and IRI (>94%) therapy compared with PBS-treated controls. Importantly, nal-IRI led to a >30% extension of animal survival compared with IRI. The addition of antiangiogenic agents nintedanib or DC101 led to a further improvement (range 3-40%) in animal survival caused by nal-IRI and IRI. In GAC cell-derived subcutaneous xenografts, compared to controls, nal-IRI demonstrated greater tumor growth inhibition (92%) than IRI (71%). Here, the combinations of nal-IRI or IRI with antiangiogenic agents exhibited an additive response. Ki67 staining of tumor sections revealed that nal-IRI was most effective in reducing intratumoral proliferation (by 58%), followed by IRI (39%), nintedanib (33%), and DC101 (25%). Combinations of nal-IRI or IRI with antiangiogenic agents demonstrated an additive effect in reducing tumor cell proliferation. As expected, tumor vasculature (assessed by endomucin staining) was reduced by nintedanib (65%) and DC101 (58%), while nal-IRI and IRI showed no effect. Pharmacokinetic studies revealed that nal-IRI increased the retention, circulation time and tumor levels of IRI and its active metabolite SN-38. The addition of nintedanib or DC101 had no effect on plasma or tumor levels of IRI or SN38. In in vitro cell viability assays in mutationally different GAC cells, SN-38 had a dose-dependent growth inhibitory effect that was more pronounced than single-agent IRI. Importantly, combinations of SN-38 or IRI with antiangiogenic agents demonstrated additive effects on cell proliferation inhibition.

CONCLUSION: nal-IRI showed greater antitumor efficacy than IRI, and its antitumor effects can be enhanced by antiangiogenic agents suggesting that this combination has potential for improving clinical GAC therapy.

Citation Format: Niranjan Awasthi, Margaret A. Schwarz, Changhua Zhang, Stephan Klinz, Florence Meyer-Losic, Benjamin Beaufils, Arunthathi Thiagalingam, Roderich E. Schwarz. Antitumor efficacy of a liposomal formulation of irinotecan in preclinical gastric cancer models: Augmenting its response by antiangiogenic agents [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 553.

Mechanistic regulation of SPHK1 expression and translocation by EMAP II in pulmonary smooth muscle cells

Phosphorylation of sphingosine by sphingosine kinase 1 (SPHK1) produces the bioactive sphingolipid sphingosine-1-phosphate (S1P), a microvascular and immuno-modulator associated with vascular remodeling in pulmonary arterial hypertension (PAH). The low intracellular concentration of S1P is under tight spatial-temporal control. Molecular mechanisms that mediate S1P burden and S1P regulation of vascular remodeling are poorly understood. Similarities between two early response pro-inflammatory cytokine gene transcript activation profiles, S1P and Endothelial Monocyte Activating Polypeptide II (EMAP II), suggested a strategic link between their signaling pathways. We determined that EMAP II triggers a bimodal phosphorylation, transcriptional regulation and membrane translocation of SPHK1 through a common upstream process in both macrophages and pulmonary artery smooth muscle cells (PASMCs). EMAP II initiates a dual function of ERK1/2: phosphorylation of SPHK1 and regulation of the transcription factor EGR1 that induces expression of SPHK1. Activated ERK1/2 induces a bimodal phosphorylation of SPHK1 which reciprocally increases S1P levels. This identified common upstream signaling mechanism between a protein and a bioactive lipid initiates cell specific downstream signaling representing a multifactorial mechanism that contributes to inflammation and PASMC proliferation which are cardinal histopathological phenotypes of PAH.

Influence of aminoacyl-tRNA synthetase complex-interacting multifunctional protein 1 on epithelial differentiation and organization during lung development

Proper development of the respiratory bronchiole and alveolar epithelium proceeds through coordinated cross talk between the interface of epithelium and neighboring mesenchyme. Signals that facilitate and coordinate the cross talk as the bronchial forming canalicular stage transitions to construction of air-exchanging capillary-alveoli niche in the alveolar stage are poorly understood. Expressed within this decisive region, levels of aminoacyl-tRNA synthetase complex-interacting multifunctional protein 1 (AIMP1) inversely correlate with the maturation of the lung. The present study addresses the role of AIMP1 in lung development through the generation and characterization of Aimp1^-/- mutant mice. Mating of Aimp1^+/- produced offspring in expected Mendelian ratios throughout embryonic development. However, newborn Aimp1^-/- pups exhibited neonatal lethality with mild cyanosis. Imaging both structure and ultrastructure of Aimp1^-/- lungs showed disorganized bronchial epithelium, decreased type I but not type II cell differentiation, increased distal vessels, and disruption of E-cadherin deposition in cell-cell junctions. Supporting the in vivo findings of disrupted epithelial cell-cell junctions, in vitro biochemical experiments show that a portion of AIMP1 binds to phosphoinositides, the lipid anchor of proteins that have a fundamental role in both cellular membrane and actin cytoskeleton organization; a dramatic disruption in F-actin cytoskeleton was observed in Aimp1^-/- mouse embryonic fibroblasts. Such observed structural defects may lead to disrupted cell-cell boundaries. Together, these results suggest a requirement of AIMP1 in epithelial cell differentiation in proper lung development.

Cell-Cell Communication Breakdown and Endothelial Dysfunction

Guided by organ-specific signals in both development and disease response, the heterogeneous endothelial cell population is a dynamic member of the vasculature. Functioning as the gatekeeper to fluid, inflammatory cells, oxygen, and nutrients, endothelial cell communication with its local environment is critical. Impairment of endothelial cell-cell communication not only disrupts this signaling process, but also contributes to pathologic disease progression. Expanding our understanding of those processes that mediate endothelial cell-cell communication is an important step in the approach to treatment of disease processes.

Combination effect of lapatinib with foretinib in HER2 and MET co-activated experimental esophageal adenocarcinoma

Recent studies have demonstrated that HER2 and MET receptor tyrosine kinases are co-overexpressed in a subset esophageal adenocarcinoma (EAC). We therefore studied the usefulness of combining HER2 and MET targeting by small-molecule inhibitors lapatinib and foretinib, respectively, both in in-vitro and in-vivo models of experimental EAC. We characterized MET and HER2 activation in a panel of human EAC cell lines, and the differential susceptibility of these EAC cell lines to single agent or combination of foretinib and lapatinib. We then explored the antitumor efficacy with survival advantage following foretinib and lapatinib monotherapy and in combination in murine subcutaneous xenograft and peritoneal metastatic survival models of human EAC. The OE33 EAC cell line with strong expression of phosphorylated both MET and HER2, demonstrated reduced sensitivity to foretinib and lapatinib when used as a single agent. The co-administration of foretinib and lapatinib effectively inhibited both MET and HER2 phosphorylation, enhanced inhibition of cell proliferation and xenograft tumor growth by inducing apoptosis, and significantly enhanced mouse overall survival, overcoming single agent resistance. In the OE19 EAC cell line with mainly HER2 phosphorylation, and the ESO51 EAC cell line with mainly MET phosphorylation, profound cell growth inhibition with induction of apoptosis was observed in response to single agent with lack of enhanced growth inhibition when the two agents were combined. These data suggest that combination therapy with foretinib and lapatinib should be tested as a treatment option for HER2 positive patients with MET-overexpressing EAC, and could be a novel treatment strategy for specific EAC patients.

A distinct transcriptional profile in response to endothelial monocyte activating polypeptide II is partially mediated by JAK-STAT3 in murine macrophages

Macrophages are important responders to environmental changes such as secreted factors. Among the secreted factors in injured tissues, the highly conserved endothelial monocyte activating polypeptide II (EMAP II) has been characterized to limit vessel formation, to be locally expressed near sites of injury labeling it a "find-me" signal, and to recruit macrophages and neutrophils. The molecular mechanisms mediated by EMAP II within macrophages once they are recruited are unknown. In this study, using a model of partially activated, recruited thioglycollate-elicited peritoneal macrophages, a transient, transcription profile of key functional genes in macrophages exposed to EMAP II was characterized. We found that EMAP II-mediated changes were elicited mainly through signal transducer and activator of transcription 3 (STAT3) as evidenced by increased Y705 phosphorylation and changes in activity and upstream of it, Janus associated kinase (JAK)1/2 upstream. Both inhibition of JAK1/2 and knockdown of Stat3 abrogated a subset of genes that are upregulated by EMAP II. Our results identify a rapid EMAP II-mediated STAT3 activation that coincides with altered pro- and anti-inflammatory gene expression in macrophages.

Abstract 293: Inhibition of BET proteins augments nab-paclitaxel-gemcitabine-based chemotherapy response in preclinical models of pancreatic cancer

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) often presents with metastatic activity, leading to an extremely poor prognosis. Nanoparticle albumin-bound paclitaxel (NPT) in combination with gemcitabine (NPT+GEM) is a standard treatment for PDAC patients, resulting in a survival of ~8.5 months. Bromodomain and extraterminal domain (BET) proteins are epigenetic regulators of gene expression and are involved in cancer pathogenesis. Targeted inhibition of BET protein is currently under investigation for several cancers. We hypothesize that BET protein pathway inhibition by iBet-762 will enhance nab-paclitaxel-gemcitabine-based standard chemotherapy response in PDAC.

METHODS: In vitro cell proliferation assays were performed using WST-1 reagent. Protein expressions were determined by Western Blot analysis. In vivo animal survival and tumor growth experiments were performed in NOD-SCID mice.

RESULTS: BET inhibitor (iBET-762) and standard chemotherapy (NPT+Gem) had a dose-dependent in vitro growth inhibitory effect on several PDAC cell lines tested. Inhibition in cell proliferation at 1 μM drug concentration in NPT+Gem, iBET-762 and NPT+Gem+iBet-762 treatment groups was 64%, 27%, 76% in AsPC-1; 43%, 13%, 69% in Panc-1; and 42%, 51%, 75% in MIA PaCa-2 cells. Immunoblot analysis demonstrated that iBET-762 decreased the expression of oncogenic proteins c-Myc, β-catenin, vimentin and phospho-AKT, while increasing the expression of apoptosis-related proteins such as cleaved PARP-1 and cleaved caspase-3 and cell cycle inhibitor proteins P21 and P27. In subcutaneous xenografts, compared to controls, NPT+Gem and iBet-762 decreased tumor growth by 72% and 57%, respectively (p<0.02). Importantly, the combination therapy group (NPT+Gem+iBet-762) had an additive effect on tumor growth inhibition (98%, p<0.0001). In a peritoneal dissemination model, median animal survival compared to controls (21 days) was increased by NPT+Gem (33 days, a 57% increase) and iBet-762 (30 days, a 43% increase) therapy. This was further increased in the combination therapy group NPT+Gem+iBET-762 (44 days, a 110% increase).

CONCLUSION: These findings demonstrate that nab-paclitaxel-gemcitabine-based standard chemotherapy response can be enhanced through specific inhibition of BET proteins by iBET-762 in preclinical models of PDAC. The data support the potential of this combinatorial therapeutic strategy for clinical PDAC therapy.

Citation Format: Niranjan Awasthi, Sandeep Singh, Ross D. McCauley, Johann RE Schwarz, Margaret A. Schwarz, Roderich E. Schwarz. Inhibition of BET proteins augments nab-paclitaxel-gemcitabine-based chemotherapy response in preclinical models of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 293.

Abstract 2208: Targeted inhibition of FGF/PDGF/VEGF signaling enhances nanoparticle taxane response in preclinical gastric cancer models

Background: Gastric adenocarcinoma (GAC) remains the third most common cause of cancer-related deaths worldwide. Most available systemic chemotherapy options for advanced GAC have limited efficacy. Nab-paclitaxel (NPT), a nanoparticle albumin-bound taxane formulation, has shown significant activity in preclinical GAC studies. Overexpression of multiple growth factors and their receptors such as FGF/FGFR, PDGF/PDGFR and VEGF/VEGFR, promote angiogenesis in several cancers including GAC that leads to tumor progression and metastasis. Dovitinib is a small molecule RTK inhibitor that potentially inhibits the activity of FGFR, PDGFR and VEGFR. We evaluated the antitumor efficacy of dovitinib and its ability to enhance nab-paclitaxel response in preclinical GAC models.

Methods: In vitro cell proliferation and protein expression were measured by WST-1 assay and Immunoblotting. In vivo tumor growth and animal survival studies were performed in NOD/SCID mice using human GAC MKN-45 cells.

Results: Nab-paclitaxel and dovitinib had in vitro growth inhibitory effect on several GAC associated cell lines tested, with additive effects in combination. Immunoblot analysis revealed that dovitinib treatment caused a decrease in the expression of phospho-FGFR, phospho-AKT, phospho-ERK; and an increase in the expression of apoptosis-related proteins cleaved PARP-1 and cleaved caspase-3. Nab-paclitaxel activity correlated with the increased expression of phospho-stathmin. In subcutaneous GAC xenografts, NPT and dovitinib demonstrated inhibition in tumor growth, while NPT+dovitinib had an additive effect. Net tumor growth was 533.7 mm3 in controls, 394.8 mm3 after oxaliplatin, 135.8 mm3 after NPT, 128 mm3 after dovitinib, 98.9 mm3 after oxaliplatin+dovitinib and -41.8 mm3 (tumor regression) after NPT+dovitinib. Tumor tissue analysis revealed that dovitinib reduced tumor vasculature, while nab-paclitaxel reduced tumor cell proliferation. In a peritoneal dissemination model, animal survival compared to controls (23 days) remained unchanged after monotherapy with oxaliplatin (24 days) or dovitinib (25 days) but increased significantly after NPT monotherapy (42 days, a 83% increase). Combination of dovitinib with NPT exhibited a further increase in animal survival (66 days, a 187% increase), while the combination of dovitinib with oxaliplatin had no survival benefit (25 days).

Conclusion: These findings demonstrate that the antitumor effect of nab-paclitaxel can be significantly enhanced by the FGFR/PDGFR/VEGFR pathway inhibitor dovitinib in preclinical GAC models. The data support the clinical relevance of this therapeutic combination for advanced GAC patients.

Citation Format: Niranjan Awasthi, Kate Crawford, Erin Bontrager, Sazzad Hassan, Urs von Holzen, Margaret A. Schwarz, Roderich E. Schwarz. Targeted inhibition of FGF/PDGF/VEGF signaling enhances nanoparticle taxane response in preclinical gastric cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2208.

Therapeutic efficacy of anti-MMP9 antibody in combination with nab-paclitaxel-based chemotherapy in pre-clinical models of pancreatic cancer

Matrix metalloproteinase 9 (MMP9) is involved in the proteolysis of extracellular proteins and plays a critical role in pancreatic ductal adenocarcinoma (PDAC) progression, invasion and metastasis. The therapeutic potential of an anti‐MMP9 antibody (αMMP9) was evaluated in combination with nab‐paclitaxel (NPT)‐based standard cytotoxic therapy in pre‐clinical models of PDAC. Tumour progression and survival studies were performed in NOD/SCID mice. The mechanistic evaluation involved RNA‐Seq, Luminex, IHC and Immunoblot analyses of tumour samples. Median animal survival compared to controls was significantly increased after 2‐week therapy with NPT (59%), Gem (29%) and NPT+Gem (76%). Addition of αMMP9 antibody exhibited further extension in survival: NPT+αMMP9 (76%), Gem+αMMP9 (47%) and NPT+Gem+αMMP9 (94%). Six‐week maintenance therapy revealed that median animal survival was significantly increased after NPT+Gem (186%) and further improved by the addition of αMMP9 antibody (218%). Qualitative assessment of mice exhibited that αMMP9 therapy led to a reduction in jaundice, bloody ascites and metastatic burden. Anti‐MMP9 antibody increased the levels of tumour‐associated IL‐28 (1.5‐fold) and decreased stromal markers (collagen I, αSMA) and the EMT marker vimentin. Subcutaneous tumours revealed low but detectable levels of MMP9 in all therapy groups but no difference in MMP9 expression. Anti‐MMP9 antibody monotherapy resulted in more gene expression changes in the mouse stroma compared to the human tumour compartment. These findings suggest that anti‐MMP9 antibody can exert specific stroma‐directed effects that could be exploited in combination with currently used cytotoxics to improve clinical PDAC therapy.

Pancreatic ductal adenocarcinoma cell secreted extracellular vesicles containing ceramide-1-phosphate promote pancreatic cancer stem cell motility

The high mortality rate associated with pancreatic ductal adenocarcinoma (PDAC) is in part due to lack of effective therapy for this highly chemoresistant tumor. Cancer stem cells, a subset of cancer cells responsible for tumor initiation and metastasis, are not targeted by conventional cytotoxic agents, which renders the identification of factors that facilitate cancer stem cell activation useful in defining targetable mechanisms. We determined that bioactive sphingolipid induced migration of pancreatic cancer stem cells (PCSC) and signaling was specific to ceramide-1-phosphate (C1P). Furthermore, PDAC cells were identified as a rich source of C1P. Importantly, PDAC cells express the C1P converting enzyme ceramide kinase (CerK), secrete C1P-containing extracellular vesicles that mediate PCSC migration, and when co-injected with PCSC reduce animal survival in a PDAC peritoneal dissemination model. Our findings suggest that PDAC secrete C1P-containing extracellular vesicles as a means of recruiting PCSC to sustain tumor growth therefore making C1P release a mechanism that could facilitate tumor progression.

Augmentation of Nab-Paclitaxel Chemotherapy Response by Mechanistically Diverse Antiangiogenic Agents in Preclinical Gastric Cancer Models

Gastric adenocarcinoma (GAC) remains the third most common cause of cancer-related deaths worldwide. Systemic chemotherapy is commonly recommended as a fundamental treatment for metastatic GAC; however, standard treatment has not been established yet. Angiogenesis plays a crucial role in the progression and metastasis of GAC. We evaluated therapeutic benefits of mechanistically diverse antiangiogenic agents in combination with nab-paclitaxel, a next-generation taxane, in preclinical models of GAC. Murine survival studies were performed in peritoneal dissemination models, whereas tumor growth studies were performed in subcutaneous GAC cell-derived or patient-derived xenografts. The mechanistic evaluation involved IHC and Immunoblot analysis in tumor samples. Nab-paclitaxel increased animal survival that was further improved by the addition of antiangiogenic agents ramucirumab (or its murine version DC101), cabozantinib and nintedanib. Nab-paclitaxel combination with nintedanib was most effective in improving animal survival, always greater than 300% over control. In cell-derived subcutaneous xenografts, nab-paclitaxel reduced tumor growth while all three antiangiogenic agents enhanced this effect, with nintedanib demonstrating the greatest inhibition. Furthermore, in GAC patient-derived xenografts the combination of nab-paclitaxel and nintedanib reduced tumor growth over single agents alone. Tumor tissue analysis revealed that ramucirumab and cabozantinib only reduced tumor vasculature, whereas nintedanib in addition significantly reduced tumor cell proliferation and increased apoptosis. Effects of nab-paclitaxel, a promising chemotherapeutic agent for GAC, can be enhanced by new-generation antiangiogenic agents, especially nintedanib. The data suggest that nab-paclitaxel combinations with multitargeted antiangiogenic agents carry promising potential for improving clinical GAC therapy. Mol Cancer Ther; 17(11); 2353-64. ©2018 AACR.

Abstract 5807: The dual c-Met/VEGFR2 inhibitor foretinib augments chemotherapy response in preclinical models of gastric cancer

BACKGROUND: Gastric adenocarcinoma (GAC) is the fourth most common malignant tumor in the world. Several growth factors and their receptors including c-Met and VEGFR, are overexpressed in GAC and thus provide a potentially effective therapeutic target. Foretinib is a novel small molecule inhibitor of the c-Met and VEGFR pathways. We evaluated the therapeutic efficacy of foretinib to enhance the antitumor response of nab-paclitaxel (NPT), a water-soluble albumin-bound formulation of paclitaxel, or oxaliplatin in preclinical models of GAC.

METHODS: Tumor growth experiments were performed in subcutaneous xenografts in NOD/SCID mice using 5x106 MKN-45 cells. Animal survival study was performed as peritoneal dissemination model in NOD/SCID mice using 10x106 MKN-45 cells. The mechanistic evaluation involved immunohistochemical and Immunoblot analyses.

RESULTS: In subcutaneous GAC xenografts, NPT and foretinib monotherapies demonstrated inhibition in tumor growth, while NPT plus foretinib combined showed additive effects. Net tumor growth in different therapy groups was 581.7 mm3 in controls, 397.9 mm3 after oxaliplatin, 229.9 mm3 after NPT, -82.6 mm3 (tumor regression) after foretinib, -74.1 mm3 after oxaliplatin+foretinib and -96.3 mm3 after NPT+foretinib. No significant change in body weight was observed for those mice treated with nab-paclitaxel, oxaliplatin or foretinib. In the GAC survival model, median animal survival compared to controls (23 days) remained unchanged after oxaliplatin therapy (24 days, p=ns) but increased after monotherapy with NPT (42 days, an 83% increase, p=0.0014) or foretinib (46 days, a 100% increase, p=0.0006). Importantly, a further increase in animal survival was observed in combination therapy groups: oxaliplatin+foretinib (55 days, a 139% increase, p=0.0006) and NPT+foretinib (76 days, 230% increase, p=0.0006). Effects of therapy on intratumoral proliferation and microvessel density corresponded with tumor growth inhibition data. In vitro studies demonstrated inhibition in the proliferation of GAC cells by both NPT and foretinib, with additive effects in combination. Immunoblot analysis revealed that foretinib pre-exposure blocked HGF-induced expression of phospho-c-Met. Furthermore, the foretinib treatment caused a decrease in phosphorylation of AKT, ERK, and PLC-γ in GAC cells, either alone or in combination with nab-paclitaxel.

CONCLUSION: These findings suggest that the antitumor effect of chemotherapy can be significantly enhanced by the c-Met/VEGFR pathway inhibitor foretinib, which might lead to clinically relevant therapeutic combinations to increase survival of GAC patients.

Citation Format: Niranjan Awasthi, Meghan Grojean, Sheena Monahan, Sazzad Hassan, Urs von Holzen, Margaret A. Schwarz, Roderich E. Schwarz. The dual c-Met/VEGFR2 inhibitor foretinib augments chemotherapy response in preclinical models of gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5807.

Abstract 4826: Synergistic effects of foretinib with lapatinib in MET and HER2 co-activated experimental esophageal adenocarcinoma

Introduction: Recent studies have demonstrated that HER2 and MET receptor tyrosine kinases are co-overexpressed in a subset esophageal adenocarcinoma (EAC). We therefore studied the usefulness of combining HER2 and MET targeting by small-molecule inhibitors foretinib and lapatinib both in-vitro and in-vivo models of experimental EAC.

Methods: In this study we first characterized MET and HER2 activation in a panel of human EAC cell lines and the differential susceptibility of these EAC cell lines to single agents or combinations of foretinib, a multi-kinase MET inhibitor, with HER2 targeted agent lapatinib. We evaluated the levels of phosphorylation status of MET and HER2 proteins using western blot in EAC cell lines. Foretinib and lapatinib, as single agent or in combination were tested for effect on cell growth as detected by WST-1 assay and on cell apoptosis as detected by western blot of cleavage of caspase 3 and poly ADP ribose polymerase (PARP). In addition, we explored the antitumor efficacy with survival advantage following foretinib and lapatinib mono and combination therapies for two weeks in murine subcutaneous xenograft and peritoneal metastatic survival models of human EAC.

Results: The OE33 EAC cell line with phosphorylation of both MET and HER2, demonstrated reduced sensitivity to foretinib and lapatinib when used as a single agent. The co-administration of foretinib and lapatinib effectively inhibited both MET and HER2 phosphorylation, synergistically inhibited cell growth and induced apoptosis, overcoming single agent resistance. In the OE19 EAC cell line with only HER2 phosphorylation and the ESO51 EAC cell line with only MET phosphorylation, profound cell growth inhibition with induction of apoptosis was observed in response to single agent foretinib and lapatinib, respectively, with lack of enhanced growth inhibition when the two drugs were combined. Foretinib in combination with lapatinib treatment resulted in significantly higher antitumor efficacy and survival benefit compared with foretinib or lapatinib treatment alone. In subcutaneous xenografts using OE33 cells, average net tumor growth after two weeks in different therapy groups was 247.83 mm3 in control, 216.71 mm3 after foretinib (p=0.49), 239.68 mm3 after lapatinib (p=0.74), and 108.06 mm3 after foretinib plus lapatinib (p=0.0011). In the OE33 survival model there was a significant increase in median animal survival after two weeks foretinib plus lapatinib treatment (71 days) compared to control (60 days, p=0.0021), to foretinib therapy (63 days, p=0.0019) or to lapatinib (61 days, p=0.0019) therapy.

Conclusion: These data suggest that combination therapy with foretinib and lapatinib should be tested as a treatment option for HER2 positive patients with MET-overexpressing EAC. Therefore, this combination therapy could be a novel treatment strategy for EAC with MET and HER co-activation.

Citation Format: Md Sazzad Hassan, Fiona Williams, Niranjan Awasthi, Margaret A. Schwarz, Roderich E. Schwarz, Urs von Holzen. Synergistic effects of foretinib with lapatinib in MET and HER2 co-activated experimental esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4826.

Abstract 4813: Enhancement of nab-paclitaxel response by inhibition of insulin-like growth factor (IGF) signaling in experimental esophageal adenocarcinoma

Introduction: Esophageal adenocarcinoma (EAC) is the fastest growing cancer in the western world and the overall 5 year survival rate of EAC is below 20 percent. Most patients with EAC present with locally advanced or widespread metastatic disease, where current treatment is largely ineffective. Therefore, new therapeutic approaches are urgently needed. Epidemiological studies have linked obesity with EAC. IGF signaling is an important mediator in obesity-associated EAC. Paclitaxel (PT) has been used in combination with carboplatin as a standard combination therapy for advanced EAC. PT required emulsification with solvents which has resulted in serious adverse effects in patients. Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is an albumin-stabilized, cremophor-free and water soluble nanoparticle formulation of PT. Nab-paclitaxel has recently shown greater efficacy over PT in EAC. Here we evaluated the improvement in nab-paclitaxel response by addition of BMS-754807, a small molecule inhibitor of IGF-1R/IR signaling, in experimental EAC.

Methods: We first evaluated the phosphorylation status of IGF-1R/IR protein by western blot in a panel of EAC cell lines. BMS-754807 and nab-paclitaxel, alone or in combination were tested for effects on cell growth detected by WST-1 assay and on cell apoptosis detected by western blot of cleavage of caspase 3 and PARP. We then explored the antitumor efficacy with survival advantage following BMS-754807 and nab-paclitaxel mono and combination therapies in murine subcutaneous xenograft and peritoneal metastatic survival models of human EAC.

Results: BMS-754807 dose dependently inhibited in-vitro cell proliferation of OE19 and FLO-1 EAC cell lines having strong tyrosine phosphorylation of IGF-1R/IR protein and interestingly the addition of IC25 dose of BMS-754807 significantly decreased the nab-paclitaxel IC50 in these EAC cells. In addition, co-administration of BMS-754807 and nab-paclitaxel effectively enhanced cleavage of caspase-3 and PARP in these EAC cells. In subcutaneous xenografts using OE19 cells, average net tumor growth after two weeks in different therapy groups was 558.67 mm3 in control, 208.47 mm3 after BMS-754807 (p=0.043), 104.60 mm3 after nab-paclitaxel (p=0.013), and 14.30 mm3 after BMS-754807 plus nab-paclitaxel (p=0.0005). In OE19 EAC survival model there was a significant increase in median animal survival after two weeks BMS-754807 plus nab-paclitaxel treatment (85 days) compared to control (47 days, p=0.0034), to BMS-754807 therapy (57 days, p=0.0021) or to nab-paclitaxel (68 days, p=0.0339) therapy.

Conclusion: Thus BMS-754807 with nab-paclitaxel treatment resulted in significantly higher antitumor efficacy and survival benefit. These results support the potential of BMS-754807 in combination with nab-paclitaxel as an effective option for EAC therapy.

Citation Format: Md Sazzad Hassan, Fiona Williams, Niranjan Awasthi, Margaret A. Schwarz, Roderich E. Schwarz, Urs von Holzen. Enhancement of nab-paclitaxel response by inhibition of insulin-like growth factor (IGF) signaling in experimental esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4813.

Abstract 4822: Anti-MMP9 antibody in combination with standard cytotoxic therapy in preclinical models of pancreatic cancer

BACKGROUND: Matrix metalloproteinase 9 (MMP9) is involved in the proteolysis of extracellular proteins and is reported to play a key role in development, invasion and metastasis of many cancers including pancreatic ductal adenocarcinoma (PDAC). Andecaliximab is a potent and highly selective monoclonal antibody inhibitor of MMP9 that has shown antitumor activity in combination with chemotherapy in gastric cancer. The therapeutic potential of targeted MMP9 inhibition in combination with cytotoxic therapy in preclinical models of PDAC was evaluated through the use of an αMMP9 antibody.

METHODS: Animal survival and qualitative analysis were performed in the peritoneal dissemination model in mice using 7.5x105 AsPC-1 cells. Tumor growth study was performed in subcutaneous xenografts in mice using 7.5x105 AsPC-1 cells. The mechanistic evaluation involved RNASeq, Luminex, IHC and Immunoblot analysis in tumor samples.

RESULTS: Median animal survival compared to controls (17 days) was increased after 2-week therapy with NPT (27 days, a 59% increase), Gem (22 days, +29%) and NPT+Gem (30 days, +76%). Addition of αMMP9 antibody increased survival as follows: NPT+MMP9 (30 days, +76%), Gem+MMP9 (25 days, +47%) and NPT+Gem+MMP9 (33 days, +94%). Evaluation of efficacy of maintenance therapy (6-weeks) revealed that median animal survival (controls: 22 days) was increased after NPT+Gem therapy (63 days, +186%) and further improved by addition of αMMP9 antibody (70 days, +218%). Qualitative assessment of mice after 2-week therapy revealed that αMMP9 therapy led to reduction in jaundice, bloody ascites and metastatic burden, both alone and in combination with NPT+Gem. Tumor lysates demonstrated changes in several proteins in chemotherapy groups including IP-10, MDC, PAI-1, GM-CSF, MIP-1b and IL-12b. αMMP9 therapy increased IL-28 (1.5 fold, p = 0.016). IHC analysis revealed decreased tumor microvessel density based on endomucin staining in αMMP9 therapy groups (59.9%, p<0.0001). Immunoblot analysis showed decreased vimentin expression in αMMP9 therapy groups (42.5%, p =0.03). In tumor growth study, NPT+Gem significantly decreased tumor growth (72%, p=0.0005) compared to controls. αMMP9 therapy caused a non-significant decrease in tumor growth (17%, p=0.24). Tumor tissues revealed low, but detectable levels of MMP9 mRNA in all therapy groups but no difference in MMP9 expression. αMMP9 monotherapy resulted in more gene expression changes in the mouse stromal than the human tumor compartment compared to other treatments. However, NPT+Gem+MMP9 combination therapy resulted in greater numbers of changes in gene expression compared to the other treatments in the tumor compartment.

CONCLUSION: These findings suggest that MMP9 inhibition can augment the effects of standard cytotoxic therapy and support the potential of this combination therapeutic strategy for clinical PDAC therapy.

Citation Format: Niranjan Awasthi, Amanda Mikels-Vigdal, Erin Stefanutti, Margaret A. Schwarz, Sheena Monahan, Victoria Smith, Roderich E. Schwarz. Anti-MMP9 antibody in combination with standard cytotoxic therapy in preclinical models of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4822.

Aminoacyl tRNA synthetase complex interacting multifunctional protein 1 simultaneously binds Glutamyl-Prolyl-tRNA synthetase and scaffold protein aminoacyl tRNA synthetase complex interacting multifunctional protein 3 of the multi-tRNA synthetase complex

Higher eukaryotes have developed extensive compartmentalization of amino acid (aa) - tRNA coupling through the formation of a multi-synthetase complex (MSC) that is composed of eight aa-tRNA synthetases (ARS) and three scaffold proteins: aminoacyl tRNA synthetase complex interacting multifunctional proteins (AIMP1, 2 and 3). Lower eukaryotes have a much smaller complex while yeast MSC consists of only two ARS (MetRS and GluRS) and one ARS cofactor 1 protein, Arc1p (Simos et al., 1996), the homolog of the mammalian AIMP1. Arc1p is reported to form a tripartite complex with GluRS and MetRS through association of the N-terminus GST-like domains (GST-L) of the three proteins (Koehler et al., 2013). Mammalian AIMP1 has no GST-L domain corresponding to Arc1p N-terminus. Instead, AIMP3, another scaffold protein of 18 kDa composed entirely of a GST-L domain, interacts with Methionyl-tRNA synthetase (MARS) (Quevillon et al., 1999) and Glutamyl-Prolyl-tRNA Synthetase (EPRS) (Cho et al., 2015). Here we report two new interactions between MSC members: AIMP1 binds to EPRS and AIMP1 binds to AIMP3. Interestingly, the interaction between AIMP1 and AIMP3 complex makes it the functional equivalent of a single Arc1p polypeptide in yeast. This interaction is not mapped to AIMP1 N-terminal coiled-coil domain, but rather requires an intact tertiary structure of the entire protein. Since AIMP1 also interacts with AIMP2, all three proteins appear to compose a core docking structure for the eight ARS in the MSC complex.

Abstract LB-B29: Combined inhibition of MAPK and PI3K signaling augments standard chemotherapy response in preclinical models of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal cancer with mortality closely paralleling incidence despite substantial advances in biological understanding of the disease. Nab-paclitaxel (NPT) plus Gemcitabine (Gem) represents the current standard for systemic therapy of advanced PDAC. More than 90% of PDACs harbor an activating mutation in the KRAS oncogene. Presently, no therapeutics exist that effectively target this oncogene, but alternative strategies focus on inhibition of downstream effectors of KRAS signaling pathways. The RAF-MEK-ERK (MAPK) and the AKT-PI3K signaling pathways are well-described mediators of KRAS induced transformation and tumorigenesis in several cancers including PDAC and represent potential targets for combination therapy. We evaluated combination treatment benefits of NPT+Gem with the MEK inhibitor trametinib (Tra) and the AKT inhibitor MK-2206 (MK) in preclinical models to evaluate their therapeutic potential against PDAC.

An animal survival study was performed in peritoneal dissemination model in NOD/SCID mice. Tumor growth inhibition studies were performed in subcutaneous PDAC cell-line-derived xenografts and PDAC patient-derived xenografts in mice. Intratumoral mechanism of action was determined by immunohistochemistry (IHC) and Immunoblot analysis.

Median animal survival in peritoneal dissemination PDAC xenografts in mice revealed that the median survival was 21 days in controls, which was significantly improved by the NPT+Gem combination (35 days, a 67% increase over controls). Median survival was further increased by addition of trametinib or MK-2206 to the NPT+Gem chemotherapy regimen: NPT+Gem+Tra (43 days, a 105% increase over controls), NPT+Gem+MK (39 days, a 86% increase over controls) and NPT+Gem+MK+Tra (48 days, a 129% increase over controls). In human subcutaneous xenografts using AsPC-1 PDAC cells, trametinib and MK-2206 were also able to enhance NPT+Gem effects. Compared to controls (100±34.8), the percent net local tumor growth in different therapy groups was 21.8±5.9 for NPT+Gem, 7.1±11.2 for NPT+Gem+Tra, 17.2±4.8 for NPT+Gem+MK and 5.7±9.1 for NPT+Gem+MK+Tra. Effects of therapy on intratumoral proliferation and apoptosis corresponded with tumor growth inhibition data. Furthermore, in vivo effects of trametinib and MK-2206 correlated with reduced expression of phospho-ERK and phospho-AKT in tumor samples. More importantly, in a recently completed patient-derived xenograft study, we observed that the addition of trametinib or MK-2206 again augmented the NPT+Gem tumor growth inhibition response. In this experiment, compared to controls (350 mm3), the net local tumor growth in different therapy groups was 145.4 mm3 for NPT+Gem, 122 mm3 for NPT+Gem+Tra, 20.4 mm3 for NPT+Gem+MK and -43.7 mm3 (tumor regression) for NPT+Gem+MK+Tra.

These findings from multiple preclinical model settings suggest that the effects of NPT+Gem can be enhanced through combined inhibition of MAPK and PI3K signaling, which supports the potential of these targets for clinical PDAC therapy.

Citation Format: Niranjan Awasthi, Sheena Monahan, Alexis Stefaniak, Margaret A. Schwarz, Roderich E. Schwarz. Combined inhibition of MAPK and PI3K signaling augments standard chemotherapy response in preclinical models of pancreatic cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-B29.

Inhibition of the MEK/ERK pathway augments nab-paclitaxel-based chemotherapy effects in preclinical models of pancreatic cancer

Nab-paclitaxel (NPT) combination with gemcitabine (Gem) represents the standard chemotherapy for pancreatic ductal adenocarcinoma (PDAC). Genetic alterations of the RAS/RAF/MEK/ERK (MAPK) signaling pathway yielding constitutive activation of the ERK cascade have been implicated as drivers of PDAC. Inhibition of downstream targets in the RAS-MAPK cascade such as MEK remains a promising therapeutic strategy. The efficacy of trametinib (Tra), a small molecule inhibitor of MEK1/2 kinase activity, in combination with nab-paclitaxel-based chemotherapy was evaluated in preclinical models of PDAC. The addition of trametinib to chemotherapy regimens showed a trend for an additive effect on tumor growth inhibition in subcutaneous AsPC-1 and Panc-1 PDAC xenografts. In a peritoneal dissemination model, median animal survival compared to controls (20 days) was increased after therapy with NPT (33 days, a 65% increase), Tra (31 days, a 55% increase), NPT+Tra (37 days, a 85% increase), NPT+Gem (39 days, a 95% increase) and NPT+Gem+Tra (49 days, a 145% increase). Effects of therapy on intratumoral proliferation and apoptosis corresponded with tumor growth inhibition. Trametinib effects were specifically accompanied by a decrease in phospho-ERK and an increase in cleaved caspase-3 and cleaved PARP-1 proteins. These findings suggest that the effects of nab-paclitaxel-based chemotherapy can be enhanced through specific inhibition of MEK1/2 kinase activity, and supports the clinical application of trametinib in combination with standard nab-paclitaxel-based chemotherapy in PDAC patients.

Abstract 4202: Trametinib, a MEK inhibitor, augments nab-paclitaxel based chemotherapy response in preclinical models of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is currently the third leading cause of cancer related deaths in the USA with a 5-year survival less than 6%. Nanoparticle albumin-bound paclitaxel (nab-paclitaxel, NPT) has demonstrated 8.5 months median survival in combination with gemcitabine, and now represents a standard of care for PDAC patients. Genetic alterations of the RAS/RAF/MEK/ERK (MAPK) signaling pathway yielding constitutive activation of the ERK cascade have been implicated in many human cancers. In PDAC, activating K-ras mutations occur at a frequency of 90%, rendering this a potential therapeutic target. Efforts to develop drugs that directly target mutant KRAS protein remain challenging due to target specificity issues. Alternative strategies therefore focus towards inhibition of downstream targets in the RAS-MAPK cascade such as MEK. Trametinib (Tra) is a potent and highly selective small molecule inhibitor of MEK1/2 kinase activity. We evaluated efficacy of trametinib to enhance antitumor response of nab-paclitaxel based chemotherapy regimens in preclinical models of PDAC using K-ras mutant cell lines.

In subcutaneous PDAC xenografts using AsPC-1 cells, net tumor growth in different therapy groups was 432.6 mm3 in controls, 105.3 mm3 after NPT (p=0.0023), 184 mm3 after Tra (p=0.0018), 81 mm3 after NPT+Tra (p=0.0003), 37.3 mm3 after NPT+Gem (p=0.0025) and -8.1 mm3 (tumor regression) after NPT+Gem+Tra (p<0.0001). In another subcutaneous PDAC xenografts using Panc-1 cells, net tumor growth in different therapy groups was: 274.1 mm3 in controls, 80.8 mm3 after NPT (p=0.0002), 150.6 mm3 after Tra (p=0.0047), 75.1 mm3 after NPT+Tra (p=0.0002), 48.4 mm3 after NPT+Gem (p=0.0004) and 3.8 mm3 after NPT+Gem+Tra (p<0.0001). In PDAC peritoneal dissemination model using AsPC-1 cells, median animal survival compared to controls (20 days) was increased after therapy with NPT (33 days, a 65% increase, p=0.0004), Tra (31 days, a 55% increase, p=0.0004), NPT+Tra (37 days, a 85% increase, p=0.0001), NPT+Gem (39 days, a 95% increase, p=0.0001) and NPT+Gem+Tra (49 days, a 145% increase, p<0.0001). Effects of therapy on intratumoral proliferation and apoptosis corresponded with tumor growth inhibition data. In vitro studies demonstrated inhibition in PDAC cell (AsPC-1, Panc-1, Mia PaCa-2, CFPAC) proliferation by NPT+Gem, Tra, and combination. Immunoblot analysis revealed that trametinib effects were specifically accompanied by decrease in phospho-ERK expression and increase in the expression of apoptosis-related cleaved caspase-3 and cleaved PARP-1 proteins. These findings suggest that the effects of nab-paclitaxel based chemotherapy regimens can be enhanced through specific inhibition of MEK1/2 kinase activity, which clinically could lead to improved PDAC therapy effects.

Citation Format: Niranjan Awasthi, Sheena Monahan, Alexis Stefaniak, Margaret A. Schwarz, Roderich E. Schwarz. Trametinib, a MEK inhibitor, augments nab-paclitaxel based chemotherapy response in preclinical models of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4202. doi:10.1158/1538-7445.AM2017-4202

Abstract 2040: Superior therapeutic efficacy of nanoparticle albumin-bound paclitaxel over cremophor-bound paclitaxel in experimental esophageal adenocarcinoma

Introduction: Esophageal adenocarcinoma (EAC) has become the dominant type of esophageal cancer in United States. EAC is the fastest growing cancer in the western world and the overall 5 year survival rate of EAC is below 20 percent. Most patients with EAC present with locally advanced or widespread metastatic disease, where current treatment is largely ineffective. Prognosis for EAC patients remains poor even with combination therapies due to high resistance to chemotherapy. Therefore, new therapeutic approaches are urgently needed. Paclitaxel (PTX) has been used in combination with carboplatin (CP) as a standard combination therapy for advanced EAC. PTX required emulsification with solvents to allow intravenous administration which has resulted in hypersensitivity reactions and potentially dramatic side effects in patients. Nanoparticle albumin-bound (nab) PTX is an albumin-stabilized, cremophor-free and water soluble nanoparticle formulation of PTX. Nab-PTX is a novel microtubule-inhibitory cytotoxic agent and the potential role of nab-PTX has not been tested yet in experimental EAC.

Methods: We explored the antiproliferative and antitumor efficacy with survival advantage following CP, PTX and nab-PTX as monotherapy and in combinations in in-vitro, and in murine subcutaneous xenograft and peritoneal metastatic survival models of human EAC.

Results: Nab-PTX inhibited in-vitro cell proliferation with significantly lower IC50 (0.25 µM in OE19 and 49 nM in OE33) than that of PTX (0.74 µM in OE19 and 98 nM in OE33) and CP (5.21 µM in OE19 and 1.05 µM in OE33) in OE19 and OE33 EAC cell lines. Nab-PTX treatment resulted in significantly higher antitumour efficacy and survival benefit compared with PTX or CP treatment. After two-week nab-PTX, PTX, CP, nab-PTX+CP or PTX+CP treatments, the average in-vivo local tumor growth inhibition rate was 73, 60, 35, 81 and 68 percent respectively (p=0.025). Nab-PTX treatment increased expression of the mitotic-spindle associated phospho-stathmin, decreased expression of proliferative marker Ki-67 and enhanced apoptosis as confirmed by increased expression of cleaved-PARP and cleaved caspase-3. There was an increase in median animal survival after nab-PTX treatment (65 days) compared to controls (46 days, p=0.0023), PTX (57 days, p=0.0034) or to CP therapy (53 days, p=0.0034).

Conclusion: In conclusion, the present study demonstrates that nab-PTX had stronger antiproliferative and antitumor activity in experimental EAC than the current standard chemotherapeutic agents. This strong antitumor activity supports the rationale for clinical evaluation of nab-PTX as promising microtubule-inhibitory agent in EAC.

Citation Format: Md Sazzad Hassan, Niranjan Awasthi, Roderich E. Schwarz, Margaret A. Schwarz, Urs von Holzen. Superior therapeutic efficacy of nanoparticle albumin-bound paclitaxel over cremophor-bound paclitaxel in experimental esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2040. doi:10.1158/1538-7445.AM2017-2040

α5β1 integrin mediates pulmonary epithelial cyst formation

BACKGROUND

Formation of the epithelial cyst involves the establishment of apical-basolateral polarity through a series of cellular interactions that are in part mediated by the extracellular matrix (ECM). We report that in a three-dimensional multi-cellular self-assembly model of lung development, α5 integrin regulates epithelial cyst formation through organization of soluble fibronectin matrix into insoluble fibrils through a process called fibrillogenesis.

RESULTS

Dissociated murine embryonic lung cells self-assemble into three-dimensional pulmonary bodies that are dependent on α5β1 integrin mediated fibrillogenesis for cell-cell mediated self-assembly: compaction and epithelial cyst formation. Knockdown of α5 integrin resulted in a significant increase in another mediator of fibrillogenesis, αV integrin. Compensatory increased expression of another mediator of fibrillogenesis, αV integrin, was not sufficient to normalize epithelial cyst formation. Loss of α5 integrin-mediated fibrillogenesis perturbed the ability of clustered epithelial cells to establish clear polarity, loss of epithelial cell pyramidal shape, and disrupted apical F-actin-rich deposition. Lack of rich central epithelial localization of F-actin cytoskeleton and Podocalyxin suggests that loss of α5 integrin-mediated fibrillogenesis interferes with the normal cytoskeleton organization that facilitates epithelial cysts polarization.

CONCLUSIONS

We conclude that lung epithelial cyst formation in development is mediated in part by α5β1 integrin dependent fibrillogenesis. Developmental Dynamics 246:475-484, 2016. © 2017 Wiley Periodicals, Inc.

Endothelial Monocyte-Activating Polypeptide II Mediates Macrophage Migration in the Development of Hyperoxia-Induced Lung Disease of Prematurity

Myeloid cells are key factors in the progression of bronchopulmonary dysplasia (BPD) pathogenesis. Endothelial monocyte-activating polypeptide II (EMAP II) mediates myeloid cell trafficking. The origin and physiological mechanism by which EMAP II affects pathogenesis in BPD is unknown. The objective was to determine the functional consequences of elevated EMAP II levels in the pathogenesis of murine BPD and to investigate EMAP II neutralization as a therapeutic strategy. Three neonatal mouse models were used: (1) BPD (hyperoxia), (2) EMAP II delivery, and (3) BPD with neutralizing EMAP II antibody treatments. Chemokinic function of EMAP II and its neutralization were assessed by migration in vitro and in vivo. We determined the location of EMAP II by immunohistochemistry, pulmonary proinflammatory and chemotactic gene expression by quantitative polymerase chain reaction and immunoblotting, lung outcome by pulmonary function testing and histological analysis, and right ventricular hypertrophy by Fulton's Index. In BPD, EMAP II initially is a bronchial club-cell-specific protein-derived factor that later is expressed in galectin-3⁺ macrophages as BPD progresses. Continuous elevated expression corroborates with baboon and human BPD. Prolonged elevation of EMAP II levels recruits galectin-3⁺ macrophages, which is followed by an inflammatory state that resembles a severe BPD phenotype characterized by decreased pulmonary compliance, arrested alveolar development, and signs of pulmonary hypertension. In vivo pharmacological EMAP II inhibition suppressed proinflammatory genes Tnfa, Il6, and Il1b and chemotactic genes Ccl2 and Ccl9 and reversed the severe BPD phenotype. EMAP II is sufficient to induce macrophage recruitment, worsens BPD progression, and represents a targetable mechanism of BPD development.

Augmentation of response to nab-paclitaxel by inhibition of insulin-like growth factor (IGF) signaling in preclinical pancreatic cancer models

Nab-paclitaxel has recently shown greater efficacy in pancreatic ductal adenocarcinoma (PDAC). Insulin like growth factor (IGF) signaling proteins are frequently overexpressed in PDAC and correlate with aggressive tumor phenotype and poor prognosis. We evaluated the improvement in nab-paclitaxel response by addition of BMS-754807, a small molecule inhibitor of IGF-1R/IR signaling, in preclinical PDAC models. In subcutaneous xenografts using AsPC-1 cells, average net tumor growth in different therapy groups was 248.3 mm3 in controls, 42.4 mm3 after nab-paclitaxel (p = 0.002), 93.3 mm3 after BMS-754807 (p = 0.01) and 1.9 mm3 after nab-paclitaxel plus BMS-754807 (p = 0.0002). In subcutaneous xenografts using Panc-1 cells, average net tumor growth in different therapy groups was: 294.3 mm3 in controls, 23.1 mm3 after nab-paclitaxel (p = 0.002), 118.2 mm3 after BMS-754807 (p = 0.02) and -87.4 mm3 (tumor regression) after nab-paclitaxel plus BMS-754807 (p = 0.0001). In peritoneal dissemination model using AsPC-1 cells, median animal survival was increased compared to controls (21 days) after therapy with nab-paclitaxel (40 days, a 90% increase, p = 0.002), BMS-754807 (27 days, a 29% increase, p = 0.01) and nab-paclitaxel plus BMS-754807 (47 days, a 124% increase, p = 0.005), respectively. Decrease in proliferation and increase in apoptosis by nab-paclitaxel and BMS-754807 therapy correlated with their in vivo antitumor activity. In vitro analysis revealed that the addition of IC25 dose of BMS-754807 decreased the nab-paclitaxel IC50 of PDAC cell lines. BMS-754807 therapy decreased phospho-IGF-1R/IR and phospho-AKT expression, and increased cleavage of caspase-3 and PARP-1. These results support the potential of BMS-754807 in combination with nab-paclitaxel as an effective targeting option for pancreatic cancer therapy.

Abstract 276: Enhancing standard chemotherapy response by targeted inhibition of MAPK signaling pathways in experimental pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has the worst prognosis of all solid tumors, with an overall survival rate of less than 6%. Gemcitabine (Gem) remained the standard of care agent over the past 16 years despite limited clinical benefits. Nab-paclitaxel (NPT), a water-soluble albumin-bound formulation of paclitaxel, has recently shown greater efficacy in advanced PDAC. Nab-paclitaxel combination with gemcitabine is now standard of care for advanced PDAC. More than 90% of PDAC tumors harbor an activating mutation in the KRAS oncogene. Since to date no therapeutics have effectively targeted this oncogene product, alternative strategies focus on inhibition of downstream effectors of KRAS signaling pathways. Trametinib (Tra) is a small molecule inhibitor of the RAF-MEK-ERK (MAPK) signaling pathway that is a well-described mediator of KRAS induced transformation and tumorigenesis. In the present preclinical study, we evaluated combination treatment benefits of the standard chemotherapeutics with trametinib to define a novel therapeutic strategy for PDAC.

Median animal survival over controls (20 days) in human intraperitoneal PDAC xenografts was significantly improved by NPT (33 days, a 65% increase, p = 0.0004), Gem (26 days, a 30% increase, p = 0.002), NPT+Gem (39 days, a 95% increase, p = 0.0001) and Tra (31 days, a 55% increase, p = 0.0004) therapy. Survival was further increased by addition of trametinib to chemotherapy: NPT+Tra (median: 37 days, a 85% increase, p = 0.0001), Gem+Tra (34 days, a 70% increase, p = 0.0001) and NPT+Gem+Tra (49 days, a 145% increase, p<0.0001). Treatment of subcutaneous tumor-bearing mice with chemotherapy and trametinib resulted in significant tumor growth inhibition. Net tumor growth in different therapy groups over two weeks varied between controls (432.6 mm3), NPT (105.3 mm3), Tra (184 mm3), NPT+Tra (81 mm3), NPT+Gem (37.3 mm3), and NPT+Gem+Tra (-8.1 mm3). Mean tumor weight (in g) in different therapy groups was as follows: controls 0.38±0.06, NPT 0.23±0.06, Tra 0.31±0.03, NPT+Tra 0.23±0.06, NPT+Gem 0.15±0.05 and NPT+Gem+Tra 0.11±0.05. In vitro studies demonstrated inhibition in PDAC cell (AsPC-1, Panc-1, Mia PaCa-2, CFPAC) proliferation by treatment with NPT+Gem, trametinib, and combination. Immunoblot analysis revealed that trametinib effects were accompanied by decrease in phospho-ERK expression and increase in the expression of apoptosis-related cleaved caspase-3 protein. These findings suggest that the effects of the standard chemotherapeutic regimens can be enhanced through specific inhibition of downstream components of the MAPK signaling pathway, which clinically could lead to improved PDAC therapy effects.

Citation Format: Niranjan Awasthi, Sheena Monahan, Margaret A. Schwarz, Roderich E. Schwarz. Enhancing standard chemotherapy response by targeted inhibition of MAPK signaling pathways in experimental pancreatic cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 276.

Abstract 1258: Therapeutic potential of the cyclin- dependent kinase inhibitor on c-Myc overexpressing esophageal adenocarcinoma

Introduction: Esophageal adenocarcinoma (EAC) is now the fastest growing cancer in the western world and most EAC patients present with widespread metastatic disease, where current treatment is largely ineffective. Therefore, new therapeutic approaches are urgently needed. The transcription factor proto-oncogene c-Myc is a potent activator of tumorigenesis. Tumors with elevated c-Myc expression often exhibit highly aggressive phenotype. c-Myc amplification has been shown to be frequent in esophageal adenocarcinoma and has been implicated in Barrett's carcinogenesis. Emerging data suggests that synthetic lethal interactions between c-Myc pathway activation and small molecules inhibition involved in cell cycle signaling can be therapeutically exploited to preferentially kill tumor cells. In this study, we therefore investigated whether exploiting a synthetic-lethal approach dependent on elevated c-Myc signaling is effective in treating esophageal cancer with a cyclin-dependent kinase (CDK) inhibitor flavopiridol. Methods: Western blot analysis was done to see the expression of c-Myc and apoptotic signaling pathways in a panel of nine esophageal cancer cell lines. c-Myc overexpression and knockdown were performed using both genetic and novel chemical approaches. Cell viability assays were performed in 96-well plates using the colorimetric WST-1 reagent. Esophageal cancer tumors growth was measured in xenograft and a novel peritoneal disseminated metastatic survival model of immunodeficient mice. Results: Western blot analysis revealed frequent overexpression of c-Myc in EAC cell lines. In this panel of esophageal cancer cell lines tested more than 70% of EAC cell lines showed overexpression of c-Myc. When we tested these cell lines for their ability to form xenograft tumor and peritoneal dissemination, c-Myc overexpression correlated with accelerated EAC tumor growth in xenograft and peritoneal disseminated metastatic survival model of NOD/SCID mice. The xenograft tumor growth rate and formation rate of peritoneal cancer after injection of 5 million cells were highest in OE19 EAC cell line which showed the highest c-Myc expression. In addition, median animal survival with peritoneal dissemination was lowest for OE19 (55 days) whereas OACM5.1 C EAC cell line which had the lowest c-Myc expression didn't form any peritoneal tumor. EAC cell lines with elevated c-Myc expression are preferentially more sensitive to induction of apoptosis by CDK inhibitor flavopiridol compared to EAC cell lines with lower c-Myc expression. When we tested the role of c-Myc expression by upregulation/downregulation in this apoptotic effect we found that this effect is very much dependent on c-Myc expression. Conclusion: These results indicate that CDK inhibitor alone or in combination with other cytotoxic or targeted agents can be a potential therapy for c-Myc overexpressing EAC.

Citation Format: Sazzad Hassan, Niranjan Awasthi, Margaret A. Schwarz, Roderich E. Schwarz, Urs V. Holzen. Therapeutic potential of the cyclin- dependent kinase inhibitor on c-Myc overexpressing esophageal adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1258.

MIF-CD74 signaling impedes microglial M1 polarization and facilitates brain tumorigenesis

Microglial cells in the brain tumor microenvironment are associated with enhanced glioma malignancy. They persist in an immunosuppressive M2 state at the peritumoral site and promote the growth of gliomas. Here, we investigated the underlying factors contributing to the abolished immune surveillance. We show that brain tumors escape pro-inflammatory M1 conversion of microglia via CD74 activation through the secretion of the cytokine macrophage migration inhibitory factor (MIF), which results in a M2 shift of microglial cells. Interruption of this glioma-microglial interaction through an antibody-neutralizing approach or small interfering RNA (siRNA)-mediated inhibition prolongs survival time in glioma-implanted mice by reinstating the microglial pro-inflammatory M1 function. We show that MIF-CD74 signaling inhibits interferon (IFN)-γ secretion in microglia through phosphorylation of microglial ERK1/2 (extracellular signal-regulated protein kinases 1 and 2). The inhibition of MIF signaling or its receptor CD74 promotes IFN-γ release and amplifies tumor death either through pharmacological inhibition or through siRNA-mediated knockdown. The reinstated IFN-γ secretion leads both to direct inhibition of glioma growth as well as inducing a M2 to M1 shift in glioma-associated microglia. Our data reveal that interference with the MIF signaling pathway represents a viable therapeutic option for the restoration of IFN-γ-driven immune surveillance.

Adding targeted inhibition of PI3K and MAPK signaling pathways to standard chemotherapy in experimental pancreatic cancer

278

Background: Treatment of pancreatic ductal adenocarcinoma (PDAC) remains a formidable challenge as gemcitabine (Gem) plus nab-paclitaxel (NPT) represent the current standard for systemic therapy of advanced PDAC. More than 90% of PDAC tumors harbor an activating mutation in the KRAS oncogene. Currently no therapeutics exist that can effectively target this oncogene product, but alternative strategies focus on inhibition of downstream effectors of KRAS signaling pathways. The RAF-MEK-ERK (MAPK) and the AKT-PI3K signaling pathways are well-described mediators of KRAS induced transformation and tumorigenesis and can be explored as targets for combination therapy. Methods: We evaluated combination treatment benefits of NPT+Gem with the MEK inhibitor trametinib (Tra) and the AKT inhibitor MK-2206 (MK) in experimental xenografts to test their therapeutic potential against PDAC. Results: Median animal survival in human intraperitoneal PDAC xenografts in mice revealed that the median survival was 21 days in controls; this was significantly improved by the NPT+Gem combination (35 days, a 67% increase over controls, p = 0.0007). Median survival was further increased by addition of MK-2206 or trametinib to NPT+Gem chemotherapy group: NPT+Gem+MK (39 days, a 86% increase over controls, p = 0.0003), NPT+Gem+Tra (43 days, a 105% increase over controls, p = 0.0003) and NPT+Gem+MK+Tra (48 days, a 129% increase over controls, p = 0.002). In human subcutaneous PDAC xenografts, MK-2206 or trametinib were able to enhance NPT+Gem effects. Compared to controls (100±34.8), the percent net local tumor growth in different therapy groups was: NPT+Gem 21.8±5.9 (p = 0.003), NPT+Gem+MK 17.2±4.8 (p = 0.002), NPT+Gem+Tra 7.1±11.2 (p = 0.002) and NPT+Gem+MK+Tra 5.7±9.1 (p = 0.001). In vivo effects of Tra and MK correlated with reduced expression of phospho-ERK and phospho-AKT in Western blots of tumor samples. Conclusions: These findings suggest that the effects of NPT+Gem can be enhanced through combined inhibition of MAPK and PI3K signaling pathways, which clinically could yield in improved antitumor results.

Abstract 3491: Enhancing nab-paclitaxel antitumor activity through addition of BMS-754807, a small-molecule inhibitor of IGF-1R/IR, in experimental pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the United States, and is expected to become the second-leading cause of cancer death by 2030. Gemcitabine, the standard of care agent over the past 16 years, has limited clinical benefits. Recently, nab-paclitaxel has shown greater efficacy against advanced PDAC in combination with gemcitabine. Our lab has demonstrated superior antitumor activity of nab-paclitaxel compared with gemcitabine or docetaxel in preclinical PDAC studies. Insulin like growth factor (IGF) signaling proteins are frequently overexpressed in PDAC and correlate with aggressive tumor phenotype and poor prognosis indicating that the IGF system is an important therapeutic target in PDAC patients. BMS-754807, a small molecule inhibitor of IGF-type 1 receptor (IGF-1R) and insulin receptor (IR), has shown efficacy in PDAC. We evaluated combination treatment benefits of nab-paclitaxel with BMS-754807 in experimental PDAC.

In vitro cell proliferation and protein expression were measured by WST-1 assay and immunoblotting. Heterotopic tumor growth and animal survival experiments were performed in murine xenografts.

In vitro analysis of four PDAC cell lines (AsPC-1, BxPC-3, MIA PaCa-2, Panc-1) revealed that single agent nab-paclitaxel and BMS-754807 both inhibited cell proliferation in a dose-dependent manner. To evaluate the combination treatment benefits of nab-paclitaxel and BMS-754807, the IC25 dose of BMS-754807 was combined with increasing doses of nab-paclitaxel. Addition of BMS-754807 decreased the nab-paclitaxel IC50 from 7.2 μM to 490 nM for AsPC-1, 430 nM to 50 nM for BxPC-3, 740 nM to 540 nM for MIA PaCa-2, and 690 nM to 280 nM for Panc-1 cell lines. These data suggest that BMS-754807 combines well with nab-paclitaxel and efficiently decreases the nab-paclitaxel IC50 in PDAC cell lines. In a heterotopic AsPC-1 PDAC model, relative to controls (100±21.3), percent net local tumor growth was 17.1±21.1 with nab-paclitaxel (p = 0.002), 37.6±16.2 with BMS-754807 (p = 0.01) and 0.76±9.1 with nab-paclitaxel plus BMS-754807 (p = 0.0002). In Panc-1 subcutaneous xenografts, compared with controls (100±31.5), percent net tumor growth was 7.8±27.2 with nab-paclitaxel (p = 0.002), 40.2±24.1 with BMS-754807 (p = 0.02) and -29.7±16.8 with nab-paclitaxel plus BMS-754807 (p = 0.0001). In an animal survival study, median animal survival was increased compared to controls (21 days) after nab-paclitaxel therapy (40 days, a 90% increase, p = 0.002), BMS-754807 therapy (27 days, a 29% increase, p = 0.01), and nab-paclitaxel plus BMS-754807 therapy (47 days, a 124% increase, p = 0.005).

These results highlight measurable antitumor activity of BMS-754807 in experimental PDAC and support the potential of BMS-754807 in combination with nab-paclitaxel as promising targeted therapy for clinical pancreatic cancer therapy.

Citation Format: Niranjan Awasthi, Margaret A. Schwarz, Roderich E. Schwarz. Enhancing nab-paclitaxel antitumor activity through addition of BMS-754807, a small-molecule inhibitor of IGF-1R/IR, in experimental pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3491. doi:10.1158/1538-7445.AM2015-3491

Adapted approach to profile genes while reconciling Vegf-a mRNA expression in the developing and injured lung

During lung development and injury, messenger RNA (mRNA) transcript levels of genes fluctuate over both space and time. Quantitative PCR (qPCR) is a highly sensitive, widely used technique to measure the mRNA levels. The sensitivity of this technique can be disadvantageous and errors amplified when each qPCR assay is not validated. In contrast to other organs, lungs have high RNase activity, resulting in less than optimal RNA integrity. We implemented a strategy to address these limitations in developing and injured lungs. Parameters were established and a filter designed that optimized amplicon length and included or excluded samples based on RNA integrity. This approach was illustrated and validated by measuring mRNA levels including Vegf-a in newborn mouse lungs that were injured by 85% oxygen (hyperoxia) for 12 days and compared with control (normoxia). We demonstrate that, in contrast to contradictory Vegf-a expression when normalized to the least suitable housekeeping genes, application of this filter and normalization to most suitable three housekeeping genes, Hprt, Eef2, and Rpl13a, gave reproducible Vegf-a expression, thus corroborating the sample filter. Accordingly, both short amplicon length and proper normalization to ranked, evaluated genes minimized erroneous fluctuation and qPCR amplification issues associated with nonideal RNA integrity in injured and developing lungs. Furthermore, our work uncovers how RNA integrity, purity, amplicon length, and discovery of stable candidate reference genes enhance precision of qPCR results and utilizes the advantages of qPCR in developmental studies.

The N terminus of pro-endothelial monocyte-activating polypeptide II (EMAP II) regulates its binding with the C terminus, arginyl-tRNA synthetase, and neurofilament light protein

Pro-endothelial monocyte-activating polypeptide II (EMAP II), one component of the multi-aminoacyl tRNA synthetase complex, plays multiple roles in physiological and pathological processes of protein translation, signal transduction, immunity, lung development, and tumor growth. Recent studies have determined that pro-EMAP II has an essential role in maintaining axon integrity in central and peripheral neural systems where deletion of the C terminus of pro-EMAP II has been reported in a consanguineous Israeli Bedouin kindred suffering from Pelizaeus-Merzbacher-like disease. We hypothesized that the N terminus of pro-EMAP II has an important role in the regulation of protein-protein interactions. Using a GFP reporter system, we defined a putative leucine zipper in the N terminus of human pro-EMAP II protein (amino acid residues 1-70) that can form specific strip-like punctate structures. Through GFP punctum analysis, we uncovered that the pro-EMAP II C terminus (amino acids 147-312) can repress GFP punctum formation. Pulldown assays confirmed that the binding between the pro-EMAP II N terminus and its C terminus is mediated by a putative leucine zipper. Furthermore, the pro-EMAP II 1-70 amino acid region was identified as the binding partner of arginyl-tRNA synthetase, a polypeptide of the multi-aminoacyl tRNA synthetase complex. We also determined that the punctate GFP pro-EMAP II 1-70 amino acid aggregate colocalizes and binds to the neurofilament light subunit protein that is associated with pathologic neurofilament network disorganization and degeneration of motor neurons. These findings indicate the structure and binding interaction of pro-EMAP II protein and suggest a role of this protein in pathological neurodegenerative diseases.

Nintedanib, a triple angiokinase inhibitor, enhances cytotoxic therapy response in pancreatic cancer

Angiogenesis remains a sensible target for pancreatic ductal adenocarcinoma (PDAC) therapy. VEGF, PDGF, FGF and their receptors are expressed at high levels and correlate with poor prognosis in human PDAC. Nintedanib is a triple angiokinase inhibitor that targets VEGFR1/2/3, FGFR1/2/3 and PDGFRα/β signaling. We investigated the antitumor activity of nintedanib alone or in combination with the cytotoxic agent gemcitabine in experimental PDAC. Nintedanib inhibited proliferation of cells from multiple lineages found in PDAC, with gemcitabine enhancing inhibitory effects. Nintedanib blocked PI3K/MAPK activity and induced apoptosis in vitro and in vivo. In a heterotopic model, net local tumor growth compared to controls (100%) was 60.8 ± 10.5% in the gemcitabine group, -2.1 ± 9.9% after nintedanib therapy and -12.4 ± 16% after gemcitabine plus nintedanib therapy. Effects of therapy on intratumoral proliferation, microvessel density and apoptosis corresponded with tumor growth inhibition data. In a PDAC survival model, median animal survival after gemcitabine, nintedanib and gemcitabine plus nintedanib was 25, 31 and 38 days, respectively, compared to 16 days in controls. The strong antitumor activity of nintedanib in experimental PDAC supports the potential of nintedanib-controlled mechanisms as targets for improved clinical PDAC therapy.

Blockade of EMAP II protects cardiac function after chronic myocardial infarction by inducing angiogenesis

Promoting angiogenesis is a key therapeutic target for protection from chronic ischemic cardiac injury. Endothelial-Monocyte-Activating-Polypeptide-II (EMAP II) protein, a tumor-derived cytokine having anti-angiogenic properties in cancer, is markedly elevated following myocardial ischemia. We examined whether neutralization of EMAP II induces angiogenesis and has beneficial effects on myocardial function and structure after chronic myocardial infarction (MI). EMAP II antibody (EMAP II AB), vehicle, or non-specific IgG (IgG) was injected ip at 30 min and 3, 6, and 9 days after permanent coronary artery occlusion in mice. EMAP II AB, compared with vehicle or non-specific antibody, significantly, p<0.05, improved the survival rate after MI, reduced scar size and attenuated the development of heart failure, i.e., left ventricular ejection fraction was significantly higher in EMAP II AB group, fibrosis was reduced by 24%, and importantly, more myocytes were alive in EMAP II AB group in the infarct area. In support of an angiogenic mechanism, capillary density (193/HPF vs. 172/HPF), doubling of the number of proliferating endothelial cells, and angiogenesis related biomarkers were upregulated in mice receiving EMAP II AB treatment as compared to IgG. Furthermore, EMAP II AB prevented EMAP II protein inhibition of in vitro tube formation in HUVECs. We conclude that blockade of EMAP II induces angiogenesis and improves cardiac function following chronic MI, resulting in reduced myocardial fibrosis and scar formation and increased capillary density and preserved viable myocytes in the infarct area.

Abstract 1025: Antitumor activity of nintedanib (BIBF 1120), a triple angiokinase inhibitor, in combination with gemcitabine in experimental pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths in the United States with extremely poor prognosis. Gemcitabine (Gem), the standard of care agent over the past 15 years, has limited clinical benefits. There is an urgent requirement for novel therapeutic strategies to improve overall survival of patients with pancreatic cancer. Angiogenesis, an essential process for tumor growth and metastasis, remains a sensible target for PDAC therapy. VEGF, PDGF, FGF and their receptors are all overexpressed and have been correlated with poor prognosis in human PDAC. Nintedanib (BIBF 1120, Nin) is a triple angiokinase inhibitor that targets VEGFR1/2/3, FGFR1/2/3 and PDGFRα/β signaling. Nintedanib is currently under clinical investigation for several solid tumors. The present study investigated the combination treatment benefits of gemcitabine and nintedanib in experimental PDAC. Cell proliferation, migration and protein expression were analyzed by WST-1 assay, wound healing assay and Western blotting. Tumor growth and animal survival experiments were performed in murine xenografts. Percent inhibition of cell proliferation in the Gem, Nin and Gem+Nin groups was 22%, 25% and 53% (AsPC-1 PDAC cells, Gem 50 nM, Nin 100 nM); 55%, 11% and 80% (endothelial cells HUVECs, Gem 100 nM, Nin 100 nM); 91%, 68% and 94% (fibroblast WI-38 cells, Gem 100 nM, Nin 100 nM). Nintedanib increased apoptosis, indicated by the cleavage of caspase-3 protein in all three cell-types tested. In PDAC cells, antitumor activity was accompanied by higher level of cell cycle inhibitor protein p27. Nintedanib (10 μM) inhibited in vitro wound closure by 84% in endothelial cells. In a heterotopic PDAC model, compared to the percent net local tumor growth in controls (100±29), a reduced growth of 60.8±10.5 (p=0.02) was observed in the Gem group, while a net reduction of -2.1±9.9 (p=0.0001) and -12.4±16.2 (p=0.0001) was observed in Nin and Gem+Nin groups, respectively. Compared with controls (16 days) in an AsPC-1 intraperitoneal model, median animal survival in Gem, Nin and Gem+Nin treatment groups was 25 days, 31 days and 38 days. The strong antitumor activity of nintedanib in experimental PDAC supports the potential of nintedanib-controlled mechanisms as targets for improved clinical PDAC therapy.

Citation Format: Niranjan Awasthi, Stefan Hinz, Rolf A. Brekken, Margaret A. Schwarz, Roderich E. Schwarz. Antitumor activity of nintedanib (BIBF 1120), a triple angiokinase inhibitor, in combination with gemcitabine in experimental pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1025. doi:10.1158/1538-7445.AM2014-1025

Ephrin-B2 reverse signaling increases α5β1 integrin-mediated fibronectin deposition and reduces distal lung compliance

Alveolar growth abnormalities and severe respiratory dysfunction are often fatal. Identifying mechanisms that control epithelial proliferation and enlarged, poorly septated airspaces is essential in developing new therapies for lung disease. The membrane-bound ligand ephrin-B2 is strongly expressed in lung epithelium, and yet in contrast to its known requirement for arteriogenesis, considerably less is known regarding the function of this protein in the epithelium. We hypothesize that the vascular mediator ephrin-B2 governs alveolar growth and mechanics beyond the confines of the endothelium. We used the in vivo manipulation of ephrin-B2 reverse signaling to determine the role of this vascular mediator in the pulmonary epithelium and distal lung mechanics. We determined that the ephrin-B2 gene (EfnB2) is strongly expressed in alveolar Type 2 cells throughout development and into adulthood. The role of ephrin-B2 reverse signaling in the lung was assessed in Efnb2(LacZ/6YFΔV) mutants that coexpress the intracellular truncated ephrin-B2-β-galactosidase fusion and an intracellular point mutant ephrin-B2 protein that is unable to become tyrosine-phosphorylated or to interact with either the SH2 or PDZ domain-containing downstream signaling proteins. In these viable mice, we observed pulmonary hypoplasia and altered pulmonary mechanics, as evidenced by a marked reduction in lung compliance. Associated with the reduction in lung compliance was a significant increase in insoluble fibronectin (FN) basement membrane matrix assembly with FN deposition, and a corresponding increase in the α5 integrin receptor required for FN fibrillogenesis. These experiments indicate that ephrin-B2 reverse signaling mediates distal alveolar formation, fibrillogenesis, and pulmonary compliance.

Vascular mediators in chronic lung disease of infancy: role of endothelial monocyte activating polypeptide II (EMAP II)

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of prematurity. Over the years, the BPD phenotype has evolved, but despite various advances in neonatal management approaches, the reduction in the BPD burden is minimal. With the advent of surfactant, glucocorticoids, and new ventilation strategies, BPD has evolved from a disease of structural injury into a new BPD, marked by an arrest in alveolar growth in the lungs of extremely premature infants. This deficient alveolar growth has been associated with a diminution of pulmonary vasculature. Several investigators have described the epithelial / vascular co-dependency and the significant role of crosstalk between vessel formation, alveologenesis, and lung dysplasia's; hence identification and study of factors that regulate pulmonary vascular emergence and inflammation has become crucial in devising effective therapeutic approaches for this debilitating condition. The potent antiangiogenic and proinflammatory protein Endothelial Monocyte Activating Polypeptide II (EMAP II) has been described as a mediator of pulmonary vascular and alveolar formation and its expression is inversely related to the periods of vascularization and alveolarization in the developing lung. Hence the study of EMAP II could play a vital role in studying and devising appropriate therapeutics for diseases of aberrant lung development, such as BPD. Herein, we review the vascular contribution to lung development and the implications that vascular mediators such as EMAP II have in distal lung formation during the vulnerable stage of alveolar genesis.