Relationship between left ventricular global longitudinal strain, infarct size and left ventricular function in patients with acute myocardial infarction in a stem cell therapy study

Introduction

It is critically important to determine the accuracy, and relationships between, non-invasive imaging modalities, such as two-dimensional echocardiography (TTE), gated single-photon emission computed tomography (SPECT) and cardiac magnetic resonance imaging (cMRI) in patients with recent acute myocardial infarction (AMI) because these are used as clinical trial endpoints. Modest improvements in the left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV) and infarct zone size (IS) have been reported in AMI stem cells therapy trials (SCT).

Purpose

The aim of the study was to evaluate left-ventricular global longitudinal strain (GLS) in patients with AMI enrolled to SCT and assess its relation with infarct zone, LVEF and LVEDV using multimodality imaging including TTE, cMRI and SPECT.

Methods

Twenty-eight patients (21 male, 7 female, mean age 60.0±8.7 years) with first AMI, 2–5 days after left anterior descending percutaneous coronary intervention (PCI) and IS ≥10% were enrolled. GLS was evaluated with two-dimensional speckle tracking echocardiography (aCMQ, Philips Epiq 7). Infarct zone was measured using SPECT (E.CAM, Siemens) and gadolinium-enhanced cMRI (Siemens Magnetom Sonata 1.5T). LVEF and LVEDV were assessed with TTE (Auto-ROI, Philips), SPECT (GSQUAN, Siemens) and cMRI (MASS Medis). Measurements were obtained independently by blinded analysts.

Results

Mean GLS was −11.0±2.5% and showed a positive correlation with infarct zone by SPECT and MRI, negative with TTE-LVEF and cMRI-LVEF (Figure 1) and borderline with SPECT-LVEF (r=−0.35, p=0.08). There was no correlation between GLS and TTE-LVEDV (r=−0.25, p=0.25); SPECT-LVEDV (r=−0.38, p=0.077) and MRI-LVEDV (r=−0.20, p=0.365).

Patients in the third and fourth GLS quartile had a smaller IS measured by MRI and a trend toward a smaller infarct zone by SPECT (table 1). Patients in the GLS fourth quartile had higher TTE-LVEF and a trend toward higher cMRI-LVEF compared with other quartiles.

LVEF measured with TTE and cMRI was higher compared with SPECT-LVEF (+2.6±6.8%, p=0.006 and +4.2±7.8%, p=0.030, respectively) with no difference between TTE-LVEF and MRI-LVEF (p=0.823) (Table 1).

LVEDV evaluated by SPECT and MRI was higher compared with TTE-LVEDV (+48.3±24.9 ml, +47.7±29.5 ml, both p<0.001) with no difference between SPECT-LVEDV and MRI-LVEDV (p=0.984)

Conclusions

In patients with anterior wall AMI, 2–5 days after PCI, GLS showed a good correlation with infarct zone quantified by SPECT and MRI and with LVEF measured with TTE and cMRI. GLS might thus be a valuable tool in the evaluation of myocardial injury in SCT.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): STRATEGMED 265761 “CIRCULATE” National Centre for Research and Development/Poland/ZDS/00564 Jagiellonian University Medical College Table 1Figure 1

Distinct Biomarker Profiles and TCR Sequence Diversity Characterize the Response to PD-L1 Blockade in a Mouse Melanoma Model

Only a subset of patients responds to immune checkpoint blockade (ICB) in melanoma. A preclinical model recapitulating the clinical activity of ICB would provide a valuable platform for mechanistic studies. We used melanoma tumors arising from an Hgf^tg;Cdk4^R24C/R24C genetically engineered mouse (GEM) model to evaluate the efficacy of an anti-mouse PD-L1 antibody similar to the anti-human PD-L1 antibodies durvalumab and atezolizumab. Consistent with clinical observations for ICB in melanoma, anti-PD-L1 treatment elicited complete and durable response in a subset of melanoma-bearing mice. We also observed tumor growth delay or regression followed by recurrence. For early treatment assessment, we analyzed gene expression profiles, T-cell infiltration, and T-cell receptor (TCR) signatures in regressing tumors compared with tumors exhibiting no response to anti-PD-L1 treatment. We found that CD8⁺ T-cell tumor infiltration corresponded to response to treatment, and that anti-PD-L1 gene signature response indicated an increase in antigen processing and presentation, cytokine-cytokine receptor interaction, and natural killer cell-mediated cytotoxicity. TCR sequence data suggest that an anti-PD-L1-mediated melanoma regression response requires not only an expansion of the TCR repertoire that is unique to individual mice, but also tumor access to the appropriate TCRs. Thus, this melanoma model recapitulated the variable response to ICB observed in patients and exhibited biomarkers that differentiate between early response and resistance to treatment, providing a valuable platform for prediction of successful immunotherapy. IMPLICATIONS: Our melanoma model recapitulates the variable response to anti-PD-L1 observed in patients and exhibits biomarkers that characterize early antibody response, including expansion of the TCR repertoire.

Multimodel preclinical platform predicts clinical response of melanoma to immunotherapy

Although immunotherapy has revolutionized cancer treatment, only a subset of patients demonstrate durable clinical benefit. Definitive predictive biomarkers and targets to overcome resistance remain unidentified, underscoring the urgency to develop reliable immunocompetent models for mechanistic assessment. Here we characterize a panel of syngeneic mouse models, representing a variety of molecular and phenotypic subtypes of human melanomas and exhibiting their diverse range of responses to immune checkpoint blockade (ICB). Comparative analysis of genomic, transcriptomic and tumor-infiltrating immune cell profiles demonstrated alignment with clinical observations and validated the correlation of T cell dysfunction and exclusion programs with resistance. Notably, genome-wide expression analysis uncovered a melanocytic plasticity signature predictive of patient outcome in response to ICB, suggesting that the multipotency and differentiation status of melanoma can determine ICB benefit. Our comparative preclinical platform recapitulates melanoma clinical behavior and can be employed to identify mechanisms and treatment strategies to improve patient care.

Abstract A162: Continuous treatment with rociletinib in EGFR transgenic mice results in acquired resistance to both rociletinib and osimertinib and intra-“patient” tumor heterogeneity

Activating mutations in EGFR are key drivers in a subset of non-small cell lung cancer (NSCLC) patients, as well as effective predictors of response to first-generation reversible EGFR tyrosine kinase inhibitor (TKI) therapy. However, resistance develops in many patients due to acquisition of a T790M mutation in EGFR. Rociletinib and osimertinib target the T790M mutation, and have been evaluated in previously treated EGFR mutant lung cancer patients. Osimertinib recently received FDA approval for treatment of patients with EGFR T790M mutation-positive NSCLC whose disease has progressed on or after EGFR TKI therapy. However, there is limited information on the mechanisms of resistance to these drugs, as well as limited in vivo models for acquired resistance to examine signaling pathways and/or possible treatments to abrogate resistance. We treated an EGFR-L858R-T790M transgenic lung adenocarcinoma mouse model daily with rociletinib to examine sensitivity and acquired resistance. Rociletinib exhibited potent antitumor activity as a single agent, resulting in complete tumor regression and suppression of phospho-EGFR. Despite the success of treatment, after long-term dosing (4-5 months) tumors acquired resistance to the drug, as evidenced by tumor regrowth on MRI. DNA from multiple tumor samples representing four individual drug-resistant mice was sequenced, and several novel mutations in EGFR were observed that may account for the resistant outgrowth of tumors in these mice. These included an insertion and a deletion mutation as well as missense mutations. Interestingly, in some cases different mutations arose in individual tumor nodules within the same mouse, suggesting that each tumor is an individual resistant clone. All mutations were located in the kinase domain of EGFR. For example, a de novo G796C mutation was one of the potential mechanisms of resistance to rociletinib found in two isolated nodules from one mouse lung. A mutation at the same amino acid has been found in a lung cancer patient after treatment with osimertinib; moreover, this mutation was found in a cell line mutagenesis screen to study the resistance to different EGFR TKIs. We generated Ba/F3 cell lines carrying each de novo identified EGFR mutation (along with the activating L858R and T790M mutations) and compared the potency of EGFR TKIs to cell lines carrying only the activating mutations. The cells that expressed putative acquired resistance mutations proved to be resistant to both rociletinib and osimertinib in vitro, suggesting that these mutations indeed mediated acquired resistance in vivo. Tumor nodules from drug-resistant transgenic mice were transplanted into recipient mice and expanded for further evaluation. Mice with transplanted resistant tumors did not respond to rociletinib or osimertinib treatment. Pathway analysis showed that phospho-EGFR was no longer suppressed in drug-resistant tumors carrying a deletion mutation, confirming that novel mutations result in drug resistance. We discovered that resistance to third-generation EGFR inhibitors may occur through novel mutations in EGFR. Heterogeneity of mutations in different nodules within the same lung is akin to intra-patient heterogeneity and highlights the utility of mouse models for examining acquired resistance to drugs.

Citation Format: Rajaa El Meskini, Anthony Iacovelli, Alan Kulaga, Michelle Gumprecht, Myla Spencer, Lilia Ileva, Andrew Simmons, Zoë Weaver Ohler. Continuous treatment with rociletinib in EGFR transgenic mice results in acquired resistance to both rociletinib and osimertinib and intra-“patient” tumor heterogeneity [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 A162.

Abstract 1479: Preclinical model of human melanoma for evaluation of targeted drug treatment and for immunotherapy validation

Malignant melanoma accounts for less than 5% of skin cancer cases, yet it represents 75% of deaths from skin cancer. The high mortality rate is due to the malignant, metastatic nature of the disease and resistance to chemotherapeutic treatments. Most mouse melanoma models have not fully recapitulated the histopathology of the disease and its metastatic nature. At NCI's Center for Advanced Preclinical Research (CAPR), we have adapted the HGF/SF; CDK4R24C transgenic mouse model to an optimized allograft transplant model for preclinical therapeutic studies in primary and metastatic melanoma. This genetically engineered mouse-derived Allograft (GDA) model recapitulates the features of the original GEM, including the epithelioid histopathology and key marker expression of human melanoma. It is an efficient and tractable tool for monitoring of both tumor growth and therapeutic responses in primary and metastatic melanoma in the context of a normal immune system. Additionally, aberrant expression of c-Met and upregulation of the downstream signaling pathway in HGF-GDA tumors is relevant for targeted therapeutics in melanoma. Thus, the model is a useful platform for evaluating therapies that target tumor cells and/or immunomodulatory pathways in intervention or adjuvant settings. Although drugs such as the c-Met inhibitor crizotinib and the MEK inhibitor trametinib were potent in cell culture, PD analyses of short-term (4-6 hour) treatment with small molecule therapies indicated that treatment incompletely suppresses the pathway in vivo compared to the corresponding primary cell line, and does not inhibit tumor growth. Therefore the HGF-GDA can be exploited to examine combination treatments that either prevent feedback activation of downstream pathway nodes in vivo, or modify alternate pathways, such as immunomodulatory targets. Hence, we are currently exploring rational combinations of oncogene-targeted therapy with immune-targeted therapy, for example, combined trametinib and anti-CTLA4 antibody treatment. In the HGF-GDA, complete response was observed in a subgroup of mice treated with anti-CTLA-4, i.e. established tumors fully regressed, yet the durable response and increased survival time (based on tumor volume) was not enhanced by concurrent treatment with trametinib. Future treatment studies will involve alternative regimens. Additionally, since metastasis, not the primary tumor, leads to progression of melanoma in patients, we have characterized a primary tumor resection model in which only metastatic disease is treated. Lung metastases develop after resection of the HGF-GDA primary tumor, which

may be treated in an intervention or adjuvant setting. Therefore we evaluated the effect on survival of the same combination therapy (trametinib and anti-CTLA-4) we previously used to treat the primary tumor, but as adjuvant treatment for the metastatic melanoma model.

Citation Format: Rajaa El Meskini, Michelle Gumprecht, Alan Kulaga, Anthony Iacovelli, Terry Van Dyke, Chi-Ping Day, Glenn Merlino, Zoe Weaver Ohler. Preclinical model of human melanoma for evaluation of targeted drug treatment and for immunotherapy validation. [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 1479.

Abstract B03: Synergistic control of GBM growth by MEK and PI3kinase signaling in a RAS-driven preclinical orthotopic model for human glioblastoma multiforme

PI3K, RTK/RAS, and Rb signaling are commonly altered in human GBM. We utilized a genetically engineered mouse (GEM) model for GBM, designated “TRP,” that expresses GFAP-T121 to suppress Rb (T), the KrasG12D mutation (R), and is heterozygous for a PTEN null allele (P), to develop an efficient and tractable orthotopic mouse model for GBM treatment preclinical evaluation. The orthotopic brain tumors presented linear foci of necrosis with peudopalisading by neoplastic cells described in human GBM, and were highly proliferative, invasive, and vascular. Immunohistochemistry analysis of TRP orthotopic tumors identified markers characteristic of human GBM, and tumor progression was readily examined by serial MRI.

Both PI3K and MAPK pathway inhibitors inhibited growth of TRP GEM-derived primary tumor cells, but did not result in significant apoptosis. However, when GBM derived cells were treated with a combination of pathway inhibitors such as BKM120 (a pan-PI3K inhibitor currently in clinical trials for solid tumors) and PD0325901 (a MEK inhibitor), potency was enhanced with a substantial increase in cell death. Analysis of downstream targets revealed a synergistic effect on target downregulation in the PI3K pathway. In the orthotopic GBM model, the PI3K/MAPK targeted combination delayed tumor growth by increasing GBM cell apoptosis and resulted in significantly increased survival. Taken together, our results validate this new orthotopic model for the assessment of targeted therapeutic regimens for human GBM, and show that the feedback loops and incomplete pathway suppression, observed in vivo with targeted single agents, can be overcome with a combination treatment strategy.

Citation Format: Rajaa El Meskini, Anthony Iacovelli, Alan Kulaga, Michelle Gumprecht, Philip Martin, Maureen Baran, Deborah Householder, Terry van Dyke, Zoe Weaver Ohler. Synergistic control of GBM growth by MEK and PI3kinase signaling in a RAS-driven preclinical orthotopic model for human glioblastoma multiforme. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B03. doi: 10.1158/1557-3125.RASONC14-B03

A preclinical orthotopic model for glioblastoma recapitulates key features of human tumors and demonstrates sensitivity to a combination of MEK and PI3K pathway inhibitors

Current therapies for glioblastoma multiforme (GBM), the highest grade malignant brain tumor, are mostly ineffective, and better preclinical model systems are needed to increase the successful translation of drug discovery efforts into the clinic. Previous work describes a genetically engineered mouse (GEM) model that contains perturbations in the most frequently dysregulated networks in GBM (driven by RB, KRAS and/or PI3K signaling and PTEN) that induce development of Grade IV astrocytoma with properties of the human disease. Here, we developed and characterized an orthotopic mouse model derived from the GEM that retains the features of the GEM model in an immunocompetent background; however, this model is also tractable and efficient for preclinical evaluation of candidate therapeutic regimens. Orthotopic brain tumors are highly proliferative, invasive and vascular, and express histology markers characteristic of human GBM. Primary tumor cells were examined for sensitivity to chemotherapeutics and targeted drugs. PI3K and MAPK pathway inhibitors, when used as single agents, inhibited cell proliferation but did not result in significant apoptosis. However, in combination, these inhibitors resulted in a substantial increase in cell death. Moreover, these findings translated into the in vivo orthotopic model: PI3K or MAPK inhibitor treatment regimens resulted in incomplete pathway suppression and feedback loops, whereas dual treatment delayed tumor growth through increased apoptosis and decreased tumor cell proliferation. Analysis of downstream pathway components revealed a cooperative effect on target downregulation. These concordant results, together with the morphologic similarities to the human GBM disease characteristics of the model, validate it as a new platform for the evaluation of GBM treatment.

Abstract 3137: Combined inhibition of MEK and PI3 kinase signaling results in improved survival in a preclinical orthotopic model for human glioblastoma multiforme

Glioblastoma multiforme (GBM; astrocytoma grade IV) is the most frequent and aggressive brain tumor for which no effective therapy is currently available. It has been shown that PI3K, RTK/RAS, and Rb signaling are commonly altered in human GBM. We utilized a genetically engineered mouse (GEM) model for GBM, designated

“TRP,” that expresses GFAP-T121 (T; for Rb suppression), the KrasG12D mutation (R), and is heterozygous for a PTEN null allele (P), to develop an orthotopic mouse model for the preclinical evaluation of potential therapeutics for GBM treatment. Although the de novo TRP brain tumor GEM model recapitulates features of human GBM including tissue invasion, pseudopalisading necrosis and dense vascularization, the latency to tumorigenesis (4-6 months) makes its use as a preclinical model for drug screening challenging. Therefore we isolated primary GBM cells from TRP GEMs and injected cells intracranially (IC) into syngeneic mouse brains. Recipient mice developed grade IV astrocytomas and recapitulated TRP GEM tumor histopathology. The orthotopic tumors presented linear foci of necrosis with peudopalisading by neoplastic cells that are hallmarks of human GBM, and were highly proliferative, invasive, and vascular. In addition, immunohistochemistry analysis of TRP orthotopic tumors identified markers characteristic of human GBM, and tumor progression was readily examined by serial MRI.

We used primary tumor cells derived from the TRP model in cell proliferation assays and found that PI3K and MAPK pathway inhibitors used as single agents inhibited cell growth alone, but did not result in significant apoptosis. However, when cells were treated with a combination of agents such as BKM120 (a pan-PI3K inhibitor currently in clinical trials for solid tumors) and PD0325901 (a MEK inhibitor), potency was enhanced and there was a substantial increase in cell death. Analysis of downstream targets revealed a synergistic effect on target downregulation in the PI3K pathway. The drug combination was also evaluated in vivo in the orthotopic model. We found that it delayed tumor growth by increasing GBM cell apoptosis, resulting in significantly increased survival. Our results show that combined targeting of the PI3K and MAPK pathways can have a synergistic effect in glioblastoma, and that our primary cells were a valuable tool to predict the in vivo outcome. We also validated this new orthotopic model of GBM and showed that it is tractable for the assessment of potential therapeutic regimens for human GBM.

Citation Format: Rajaa El Meskini, Anthony Iacovelli, Alan Kulaga, Michelle Gumprecht, Philip Martin, Maureen Baran, Deborah Householder, Terry Van Dyke, Zoe Weaver Ohler. Combined inhibition of MEK and PI3 kinase signaling results in improved survival in a preclinical orthotopic model for human glioblastoma multiforme. [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 3137. doi:10.1158/1538-7445.AM2014-3137

Abstract C11: Combined inhibition of MEK and PI3 kinase signaling results in improved survival in a preclinical orthotopic model for human glioblastoma multiforme

Glioblastoma multiforme (GBM; astrocytoma grade IV) is the most frequent and aggressive brain tumor for which no effective therapy is currently available. It has been shown that PI3K, RTK/RAS, and Rb signaling are commonly altered in human GBM. We utilized a genetically engineered mouse (GEM) model for GBM, designated “TRP,” that expresses GFAP-T121 (T; for Rb suppression), the KrasG12D mutation (R), and is heterozygous for a PTEN null allele (P), to develop an orthotopic mouse model for the preclinical evaluation of potential therapeutics for GBM treatment. Although the de novo TRP brain tumor GEM model recapitulates features of human GBM including tissue invasion, pseudopalisading necrosis, and dense vascularization, the latency to tumorigenesis (4-6 months) makes its use as a preclinical model for drug screening challenging. Therefore we isolated primary GBM cells from TRP GEMs and injected cells intracranially (IC) into syngeneic mouse brains. Recipient mice developed grade IV astrocytomas and recapitulated TRP GEM tumor histopathology. The orthotopic tumors presented linear foci of necrosis with peudopalisading by neoplastic cells that are hallmarks of human GBM, and were highly proliferative, invasive, and vascular. In addition, immunohistochemistry analysis of TRP orthotopic tumors identified markers characteristic of human GBM, and tumor progression was readily examined by serial MRI. We used primary tumor cells derived from the TRP model in cell proliferation assays and found that PI3K and MAPK pathway inhibitors used as single agents inhibited cell growth alone, but did not result in significant apoptosis. However, when cells were treated with a combination of agents such as BKM120 (a pan-PI3K inhibitor currently in clinical trials for solid tumors) and PD0325901 (a MEK inhibitor), potency was enhanced and there was a substantial increase in cell death. Analysis of downstream targets revealed a synergistic effect on target downregulation in the PI3K pathway. The drug combination was also evaluated in vivo in the orthotopic model. We found that it delayed tumor growth by increasing GBM cell apoptosis, resulting in significantly increased survival. Our results show that combined targeting of the PI3K and MAPK pathways can have a synergistic effect in glioblastoma, and that our primary cells were a valuable tool to predict the in vivo outcome. We also validated this new orthotopic model of GBM and showed that it is tractable for the assessment of potential therapeutic regimens for human GBM.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C11.

Citation Format: Rajaa El Meskini, Anthony Iacovelli, Alan Kulaga, Michelle Gumprecht, Philip L. Martin, Maureen L. Baran, Deborah B. Householder, Terry Van Dyke, Zoe Weaver Ohler. Combined inhibition of MEK and PI3 kinase signaling results in improved survival in a preclinical orthotopic model for human glioblastoma multiforme. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C11.

Temporal molecular and biological assessment of an erlotinib-resistant lung adenocarcinoma model reveals markers of tumor progression and treatment response

Patients with lung cancer with activating mutations in the EGF receptor (EGFR) kinase, who are treated long-term with tyrosine kinase inhibitors (TKI), often develop secondary mutations in EGFR associated with resistance. Mice engineered to develop lung adenocarcinomas driven by the human EGFR T790M resistance mutation are similarly resistant to the EGFR TKI erlotinib. By tumor volume endpoint analysis, these mouse tumors respond to BIBW 2992 (an irreversible EGFR/HER2 TKI) and rapamycin combination therapy. To correlate EGFR-driven changes in the lung with response to drug treatment, we conducted an integrative analysis of global transcriptome and metabolite profiling compared with quantitative imaging and histopathology at several time points during tumor progression and treatment. Responses to single-drug treatments were temporary, whereas combination therapy elicited a sustained response. During tumor development, metabolomic signatures indicated a shift to high anabolic activity and suppression of antitumor programs with 11 metabolites consistently present in both lung tissue and blood. Combination drug treatment reversed many of the molecular changes found in tumored lung. Data integration linking cancer signaling networks with metabolic activity identified key pathways such as glutamine and glutathione metabolism that signified response to single or dual treatments. Results from combination drug treatment suggest that metabolic transcriptional control through C-MYC and SREBP, as well as ELK1, NRF1, and NRF2, depends on both EGFR and mTORC1 signaling. Our findings establish the importance of kinetic therapeutic studies in preclinical assessment and provide in vivo evidence that TKI-mediated antiproliferative effects also manifest in specific metabolic regulation.

Abstract A42: Sensitivity and resistance to a p-AKT inhibitor in an erlotinib-sensitive model for lung cancer

Activating mutations in EGFR, such as the L858R mutation, are effective predictors of response to EGFR tyrosine kinase inhibitor (TKI) therapy. While most patients initially respond to EGFR TKIs, the majority relapse within 6-12 months, underscoring the importance of identifying therapies that enhance and prolong EGFR TKI activity in patients. Agents targeting additional nodes in the EGFR pathway have the potential to overcome such resistance but single-agent activity must be understood first. We utilized mice engineered to develop erlotinib-sensitive lung adenocarcinomas driven by the human EGFR L858R mutation to evaluate the efficacy of a p-AKT inhibitor, MK-2206, currently in clinical trials for a variety of solid tumor malignancies. MK-2206 concentration and target activity were assessed in short-term PK/PD studies in both the lungs and blood of tumor-bearing mice. MK-2206 was then evaluated in an efficacy study using a twice-weekly dosing regimen, both as a single agent and in combination with other TKIs. MK-2206 alone resulted in tumor regression or tumor growth inhibition in ∼50% of the mice, but exhibited greater efficacy in combination with other upstream pathway inhibitors. Temporal evaluation of tumor growth inhibition indicated that MK-2206 was most effective at early time points and did not produce a sustained pathway and growth response as treatment continued. Analysis of gene expression changes in mice treated with MK-2006 alone vs. MK-2206 in combination with EGFR TKIs highlighted the pathways perturbed by both drugs.

Abstract 4322: A preclinical orthotopic mouse model for human GBM: Recapitulation of features of GEM model of origin and potency of PI3K inhibitors

Glioblastoma (GBM; grade IV) is the most frequent and aggressive brain tumor for which no effective therapy is currently available. It has been shown that PI3 kinase, involving both PI3 kinase – Ras activation and PTEN inhibition, and RB signaling are commonly altered in human GBM. We utilized a GEM model expressing GFAP-T121, KrasG12D and heterozygous mutant in PTEN +/- (TRP+/-) to develop an orthotopic mouse model for the preclinical evaluation of potential therapeutics for GBM treatment. The TRP+/- GEM model recapitulates features of human GBM including tissue invasion, pseudopalisading necrosis and dense vascularisation, however the latency to tumorigenesis (4-6 months) makes its use as a preclinical model for drug screening challenging. Therefore we isolated primary tumor cells from induced TRP+/- GEMs with Grade III or Grade IV astrocytoma and injected cells intracranially (IC) into syngeneic mouse brains. Primary cells induced grade IV tumors and recapitulated TRP+/- GEM tumor histopathology. Highly proliferative, invasive, and vascular, the orthotopic grade IV tumors presented linear foci of necrosis with peudopalisading by neoplastic cells that is characteristic of human GBM. Immunohistochemistry characterization of TRP+/- orthotopic tumors revealed similar T121, GFAP and PTEN expression profile to TRP+/- GEM grade IV tumors. Other cellular markers known to be expressed in neuronal progenitors, glial cells or found to be associated with human GBM aggressiveness were assessed in the orthotopic mouse model GBM tumors in comparison with the TRP+/- GEM model. By adjusting the number of primary cells IC injected, the time period of tumor growth and assessment by MRI was increased from 3 weeks to 6 weeks allowing reasonable time for tumor growth assessment, before potential drug efficacy testing. We used primary cells of grade IV tumor origin from TRP+/- GEM to evaluate the effect of PI3 kinase pathway inhibition on cell proliferation. BEZ235, PI103 and PIK75, compounds that target the PI3 kinase pathway, are effective inhibitors of primary tumor cell proliferation with an EC50 in the 10-100 nM range. MK2206, an Akt inhibitor, was found to be a potential inhibitor of tumor cell proliferation. Although MAPK pathway activation through RB inactivation has been found to be key in triggering cell proliferation in TRP+/- GEM model, MEK inhibitors, namely AZD6244, PD0325901 and UO126 did not have a strong effect on cell proliferation. In vitro inhibition of cell proliferation assays and target validation in TRP+/- GEM primary cells are useful tools to choose compounds for orthotopic mouse efficacy studies. Preliminary in vivo mouse pharmacokinetic studies are underway to insure potential drug distribution in the brain tissue. Using the orthotopic model, we found that PI3 kinase inhibitors may be effective against brain tumors in the mouse orthotopic model for human GBM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4322. doi:10.1158/1538-7445.AM2011-4322

The spectrum of neuroendocrine differentiation among gastrointestinal carcinoids: importance of histologic grading, MIB-1, p53, and bcl-2 immunoreactivity

CONTEXT

The advent of panneuroendocrine markers has helped to better depict the heterogeneity of gastrointestinal carcinoids. Consequently, it has been proposed that these tumors constitute a histologic spectrum that includes well-, moderately, and poorly differentiated carcinoids. However, the reproducibility of this grading system and its prognostic importance have sometimes been called into question.

OBJECTIVE

To investigate the potential utility of cell proliferation and oncoprotein markers in augmenting the histologic classification.

DESIGN AND SETTING

Retrospective study; tertiary care teaching hospital.

METHODS

Fifty-eight patients with 41 well-differentiated, 12 moderately differentiated and 5 poorly differentiated carcinoids from various topographic sites of the gastrointestinal tract were selected and immunostained for panneuroendocrine markers, MIB-1, p53, and bcl-2.

MAIN OUTCOME MEASURES

Degree of association between histologic grading, MIB-1, p53, and bcl-2 immunoreactivity and carcinoid metastatic behavior.

RESULTS

The group comprised 30 males and 28 females whose mean age was 52.7 years (range, 14-81). Mean follow-up time was 85.8 months. All 58 patients tested positive for chromogranin A and/or synaptophysin. The group was divided into nonmetastatic (42/58, or 72.4%) and metastatic (16/58, or 27.6%) cases. Histologic grading tended to be associated with metastatic spread, but this occurrence of metastases did not attain statistical significance (P =.08). Positivity for MIB-1 (P =.004) and p53 (P =.04) was significantly associated with metastatic behavior, whereas bcl-2 was not (P = 0. 63).

CONCLUSIONS

Although an organoid pattern and neuroendocrine immunophenotype help to define the spectrum of gastrotestinal carcinoids, this study suggests that the histologic grading of these tumors has some limitations with respect to predicting metastatic behavior. However, MIB-1 and p53 can compliment histologic grading as prognostic indicators in this regard while bcl-2 appears to be less useful.

Granulomatous appendicitis in acute myeloblastic leukemia: expanding the clinicopathologic spectrum of invasive candidiasis

The incidence of systemic candidiasis appears to be on the rise, and unusual or hitherto undocumented clinicopathologic features of invasive candidiasis continue to be described. This report adds further to this spectrum by describing granulomatous appendicitis due to invasive candidiasis. The patient was a 23-year-old woman with acute promyelocytic leukemia. Her other risk factors included the use of aggressive chemotherapy, immunosuppressives, broadspectrum antibiotics, and invasive instrumentation. In view of the acquired immunodeficiency syndrome epidemic, as well as the improved survival of patients with prolonged neutropenia owing to better intensive care units, there is reason to believe that other as yet undocumented clinicopathologic manifestations of invasive candidiasis or other opportunistic infections may come to light.

Self-injection with olive oil. A cause of lipoid pneumonia

A 48-year-old man with unipolar depression and a psychosexual problem concerning his body image was injecting his scrotum repeatedly with olive oil to increase the size of his genitals. He developed respiratory failure following accidental intravenous injection of olive oil and was found to have lipogranulomatous lesions in the lung and the scrotum.

Ascorbate uptake by ROS 17/2.8 osteoblast-like cells: substrate specificity and sensitivity to transport inhibitors

Ascorbate (reduced vitamin C) is required for bone formation. We have shown previously that both the osteoblast-like cell line ROS 17/2.8 and primary cultures of rat calvarial cells possess a saturable, Na(+)-dependent uptake system for L-ascorbate (J Membr Biol 111:83-91, 1989). The purpose of the present study was to investigate the specificity of this transport system for organic anions and its sensitivity to transport inhibitors. Initial rates of ascorbate uptake were measured by incubating ROS 17/2.8 cells with [L-14C]ascorbate at 37 degrees C. Uptake of [L-14C]ascorbate (5 microM) was inhibited 98 +/- 1% by coincubation with unlabeled L-ascorbate (3 mM) and 48 +/- 4% by salicylate (3 mM), but it was not affected by 3 mM formate, lactate, pyruvate, gluconate, oxalate, malonate, or succinate. Uptake of the radiolabeled vitamin also was not affected by acute (1 minute) exposure of the cells to the Na+ transport inhibitors amiloride and ouabain or the glucose transport inhibitor cytochalasin B. In contrast, anion transport inhibitors rapidly (less than 1 minute) and reversibly blocked [L-14C]ascorbate uptake. In order of potency, these drugs were 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) approximately equal to sulfinpyrazone greater than furosemide approximately equal to 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS). These findings indicate that the ascorbate transporter is relatively specific for the ascorbate anion, since other organic anions (with the exception of salicylate) did not compete with ascorbate for uptake. Rapid and reversible inhibition by the impermeant antagonists DIDS and SITS suggests that they interact directly with the ascorbate transporter, consistent with location of the transport system in the plasma membrane.

Substrate regulation of ascorbate transport activity in astrocytes

Astrocytes possess a concentrative L-ascorbate (vitamin C) uptake mechanism involving a Na(+)-dependent L-ascorbate transporter located in the plasma membrane. The present experiments examined the effects of deprivation and supplementation of extracellular L-ascorbate on the activity of this transport system. Initial rates of L-ascorbate uptake were measured by incubating primary cultures of rat astrocytes with L-[14C]ascorbate for 1 min at 37 degrees C. We observed that the apparent maximal rate of uptake (Vmax) increased rapidly (less than 1 h) when cultured cells were deprived of L-ascorbate. In contrast, there was no change in the apparent affinity of the transport system for L-[14C]ascorbate. The increase in Vmax was reversed by addition of L-ascorbate, but not D-isoascorbate, to the medium. The effects of external ascorbate on ascorbate transport activity were specific in that preincubation of cultures with L-ascorbate did not affect uptake of 2-deoxy-D-[3H(G)]glucose. We conclude that the astroglial ascorbate transport system is modulated by changes in substrate availability. Regulation of transport activity may play a role in intracellular ascorbate homeostasis by compensating for regional differences and temporal fluctuations in external ascorbate levels.