EphrinB2 Inhibition and Pembrolizumab in Metastatic Urothelial Carcinoma

PURPOSE

Patients with metastatic urothelial carcinoma have poor prognosis after failure of standard first-line chemotherapy. Immune check point programmed death 1-programmed death ligand 1 antibodies have low response rates and thus there exists a major unmet need.

MATERIALS AND METHODS

In this phase II trial, patients with metastatic urothelial carcinoma that recurred or progressed after platinum-based chemotherapy received soluble EphB4-human serum albumin (sEphB4-HSA) in combination with pembrolizumab. The primary end points were tolerability and overall survival (OS). The secondary end points were progression-free survival (PFS), objective response rate (ORR), duration of response, and toxicity. The expression of sEphB4-HSA target EphrinB2 was correlated with outcomes.

RESULTS

Seventy patients were enrolled. The median follow up was 22.9 months (range, 1.3-54.7). The regimen had acceptable toxicity. In the intent-to-treat analysis (N = 70), the median OS was 14.6 months (95% CI, 9.2 to 21.5). Twenty-six (37%) patients had an objective response (95% CI, 26 to 48). The median PFS was 4.1 (95% CI, 1.5 to 5.7) months. Forty-six (66%) patients expressed EphrinB2, and among them, the median OS was 21.5 months (95% CI, 12.4 to not reached), the ORR was 52% (95% CI, 37 to 67), including a complete response rate of 24% (11 of 46; 95% CI, 12 to 36). The median PFS was 5.7 (95% CI, 2.7 to 27.9) months. Response was maintained at 6, 12, and 24 months in 88%, 74%, and 69% of the patients, respectively.

CONCLUSION

The combination of sEphB4-HSA and pembrolizumab appears synergistic with improved OS and ORR compared with historical data for programmed death 1/programmed death ligand 1 monotherapy.

Mistaking a Tumour for an Infection - Acrometastasis of the Finger from Endocervical Adenosquamous Carcinoma: A Case Report

Acrometastasis is rare with a very low incidence of all bone metastasis. It can present with swelling, pain and warmth with erythema that may mimic an infection especially in the distal phalanx. Due to its rarity and subtle clinical presentation, it can be misdiagnosed as an infection causing the treatment to be delayed. We report a 42-year-old female with an acrometastasis to the distal phalanx of the left middle finger which we mistook as an infection thus delaying her treatment. It was a terminal presentation of her endocervical adenosquamous carcinoma. We would like to highlight that acrometastasis has an indistinct presentation and in cases where the lesion does not respond to treatment, acrometastasis should be included as one of the differential diagnoses. Thus, physicians need to have a high level of suspicion in patients with a primary malignant tumour.

Diagnosis of osteoarticular tuberculosis by immuno-PCR assay based on mycobacterial antigen 85 complex detection

Diagnosis of osteoarticular tuberculosis (OATB) exhibits serious challenges owing to paucibacillary nature of specimens and localization of disease at sites that are difficult to access. We recently developed indirect immuno-PCR (I-PCR) and real-time I-PCR (RT-I-PCR) assays for the detection of mycobacterial antigen 85 complex (Ag85) in OATB patients. Detection limits for the purified Ag85 protein were found to be 1 and 41 fg ml^-1 by I-PCR and RT-I-PCR, respectively, which were at least 10⁵ -fold lower than respective ELISA. While spiking synovial fluids of non-TB control subjects with the purified Ag85 protein, LODs of 100 and 120 fg ml^-1 were obtained by I-PCR and RT-I-PCR, respectively, thus demonstrating the sample matrix effect. Sensitivities of 87·5 and 70·5% were observed in bodily fluids of confirmed (n = 8) and clinically suspected (n = 51) OATB cases, respectively, by I-PCR, with a specificity of 93·9% (n = 33). Markedly, the sensitivities obtained by I-PCR/RT-I-PCR were significantly higher (P < 0·05-0·01) than ELISA and GeneXpert assay (n = 30). However, no substantial difference in sensitivity was observed between the I-PCR and RT-I-PCR assays. After further improving the accuracy of I-PCR, this test may lead to development of an attractive diagnostic kit.

PD-1 Blockade on Tumor Microenvironment-Resident ILC2s Promotes TNF-α Production and Restricts Progression of Metastatic Melanoma

While pulmonary ILC2s represent one of the major tissue-resident innate lymphoid cell populations at steady state and are key drivers of cytokine secretion in their occupational niche, their role in pulmonary cancer progression remains unclear. As the programmed cell death protein-1 (PD-1) plays a major role in cancer immunotherapy and immunoregulatory properties, here we investigate the specific effect of PD-1 inhibition on ILC2s during pulmonary B16 melanoma cancer metastasis. We demonstrate that PD-1 inhibition on ILC2s suppresses B16 tumor growth. Further, PD-1 inhibition upregulates pulmonary ILC2-derived TNF-α production, a cytotoxic cytokine that directly induces cell death in B16 cells, independent of adaptive immunity. Together, these results highlight the importance of ILC2s and their anti-tumor role in pulmonary B16 cancer progression during PD-1 inhibitory immunotherapy.

Quantitative Tyrosine Phosphoproteome Profiling of AXL Receptor Tyrosine Kinase Signaling Network

Simple Summary

AXL is a receptor tyrosine kinase belonging to the TAM (Tyro3, Axl and Mer) family. The AXL protein plays an important role in promoting cancer development, such as proliferation, migration, invasion and survival of cancer cells. In this study, we used mass spectrometry-based proteomics to quantify the cancer signaling regulated by AXL activation. Our study identified more than 1000 phosphotyrosine sites and discovered that activation of AXL can upregulate multiple cancer-promoting and cell migration/invasion-related signaling pathways. We also observed significant crosstalk as evidenced by rapid phosphorylation of multiple receptor tyrosine kinases and protein tyrosine phosphatases, including PTPN11 and PTPRA, upon GAS6 stimulation. These discoveries should serve as a potentially useful resource for studying AXL functions as well as for the development of effective therapeutic options to target AXL.

Abstract

Overexpression and amplification of AXL receptor tyrosine kinase (RTK) has been found in several hematologic and solid malignancies. Activation of AXL can enhance tumor-promoting processes such as cancer cell proliferation, migration, invasion and survival. Despite the important role of AXL in cancer development, a deep and quantitative mapping of its temporal dynamic signaling transduction has not yet been reported. Here, we used a TMT labeling-based quantitative proteomics approach to characterize the temporal dynamics of the phosphotyrosine proteome induced by AXL activation. We identified >1100 phosphotyrosine sites and observed a widespread upregulation of tyrosine phosphorylation induced by GAS6 stimulation. We also detected several tyrosine sites whose phosphorylation levels were reduced upon AXL activation. Gene set enrichment-based pathway analysis indicated the activation of several cancer-promoting and cell migration/invasion-related signaling pathways, including RAS, EGFR, focal adhesion, VEGFR and cytoskeletal rearrangement pathways. We also observed a rapid induction of phosphorylation of protein tyrosine phosphatases, including PTPN11 and PTPRA, upon GAS6 stimulation. The novel molecules downstream of AXL identified in this study along with the detailed global quantitative map elucidating the temporal dynamics of AXL activation should not only help understand the oncogenic role of AXL, but also aid in developing therapeutic options to effectively target AXL.

Phase II trial of soluble EphB4-albumin in combination with PD-1 antibody (pembrolizumab) in relapsed/refractory head neck squamous cell carcinoma

6016

Background: EphB4 receptor tyrosine kinase and its ligand EphrinB2 are highly induced in head neck squamous cell carcinoma (HN SCC) tumor cells and vessels, particularly in HPV negative tumors. Each are predictors for poor survival with worse prognosis when both are induced. EphB4 provides tumor cell survival and EphrinB2 inhibits immune cell invasion. Soluble EphB4-Alb blocks bidirectional signaling, enhances immune cell recruitment alone and when combined with PD-1 antibody. Methods: A phase II trial of sEphB4-Alb combined with pembrolizumab accrued HN SCC patients after failure of one or more prior regimens. IHC positivity for p16 was used as a surrogate for HPV infection. Treatment regimen was sEphB4-Alb 10 mg/kg weekly IV infusion with pembrolizumab 200 mg IV infusion every three weeks. Study endpoints were toxicity, overall response rates (ORR) and overall survival (OS). Response to therapy was based on RECIST 1.1 criteria. Patient tumor samples were collected at baseline with a 2nd biopsy at week 8 on therapy, for tissue analysis of PD-L1, EphrinB2 and other biomarkers. Results: Twenty-four patients were accrued to the phase II trial combination of sEphB4-Alb and pembrolizumab. Age, sex, prior treatment, HPV status, and response data are summarized in the table below. The most common toxicity was hypertension with 8 patients experiencing grade 3 HTN. No grade 4 or above toxicities were observed. Among HPV negative cases, partial and complete responses were observed in 6 of 14 patients (43%) with complete response (CR) observed in 3 of 6 responders. Additionally, rapid response was observed in 3 of 14 HPV negative patients. Response was associated with increase in immune markers on 2nd biopsy. Median overall and progression-free survival in all patients was 12.6 months and 8.6 months, respectively. Conclusions: 1. sEphB4-Alb was well tolerated in combination with PD-1 antibody. 2. sEphB4-Alb was associated with increased immune response to tumor, when combined with PD-1 antibody. 3. sEphB4-Alb appears to have substantial activity (including complete remission) when combined with PD-1 antibody in relapsed/refractory HPV negative HN SCC. Clinical trial information: NCT03049618. [Table: see text]

Tetraspanin18 regulates angiogenesis through VEGFR2 and Notch pathways

The VEGF pathway is critically required for vasculogenesis, the formation of the primary vascular network. It is also required for angiogenesis resulting in sprouting and pruning of vessels to generate mature arborizing structures. The Notch pathway is essential for arterial–venous specification and the maturation of nascent vessels. We have determined that Tspan18, a member of the Tetraspanin family, is expressed in developing vessels but not in mature vasculature in zebrafish and mouse wound healing. Moreover, reduction at Tspan18 level resulted in aberrant vascular patterning, impaired vessel stability and defective arterial–venous specification. Tspan18 deficiency reduced VEGF, VEGFR2, Notch3 and EphrinB2, and increased EphB4, VEGFR3, Semaphorin3, Neuropilin and PlexinD1 expression. Furthermore, vascular defects of Tspan18 deficiency could be rescued by ectopic expression of VEGFR2 and Notch, but not by knockdown of Semaphorin or Plexin. Functional studies showed that knockdown of Tspan18 led to reduced endothelial cell migration, invasion and tube formation. Tspan18 has dynamic expression, regulates vascular development and maturation in the embryo with re-expression in adult life in wound healing.

Summary: Tspan18 is a transmembrane protein with highly restricted expression in endothelial cells and a critical regulator of VEGF and Notch pathways. It regulates artery–vein specification, vessel patterning and vessel stability.

A Novel DNA Methylation Signature as an Independent Prognostic Factor in Muscle-Invasive Bladder Cancer

Background

Muscle-invasive bladder cancer (MIBC) accounts for approximately 20% of all urothelial bladder carcinomas (UBC) at time of diagnosis, and up to 30% of patients with non-muscle invasive UBC will progress to MIBC over time. An increasing body of evidence has revealed a strong correlation between aberrant DNA methylation and tumorigenesis in MIBC.

Results

Using The Cancer Genome Atlas (TCGA) molecular data for 413 patients, we described a DNA methylation-based signature as a prognostic factor for overall survival (OS) in MIBC patients. By using a least absolute shrinkage and selection operator (LASSO) model, differentially methylated regions were first identified using multiple criteria followed by survival and LASSO analyses to identify DNA methylation probes related to OS and build a classifier to stratify patients with MIBC. The prognostic value of the classifier, referred to as risk score (RS), was validated in a held-out testing set from the TCGA MIBC cohort. Finally, receiver operating characteristic (ROC) analysis was used to compare the prognostic accuracy of the models built with RS alone, RS plus clinicopathologic features, and clinicopathologic features alone. We found that our seven-probe classifier-based RS stratifies patients into high- and low-risk groups for overall survival (OS) in the testing set (n = 137) (AUC at 3 years, 0.65; AUC at 5 years, 0.65). In addition, RS significantly improved the prognostic model when it was combined with clinical information including age, smoking status, Tumor (T) stage, and Lymph node metastasis (N) stage.

Conclusions

The DNA methylation-based RS can be a useful tool to predict the accuracy of preoperative and/or post-cystectomy models of OS in MIBC patients.

Delta-like ligand 4-mediated Notch signaling controls proliferation of second heart field progenitor cells by regulating Fgf8 expression

The role played by the Notch pathway in cardiac progenitor cell biology remains to be elucidated. Delta-like ligand 4 (Dll4), the arterial-specific Notch ligand, is expressed by second heart field (SHF) progenitors at time-points that are crucial in SHF biology. Dll4-mediated Notch signaling is required for maintaining an adequate pool of SHF progenitors, such that Dll4 knockout results in a reduction in proliferation and an increase in apoptosis. A reduced SHF progenitor pool leads to an underdeveloped right ventricle (RV) and outflow tract (OFT). In its most severe form, there is severe RV hypoplasia and poorly developed OFT resulting in early embryonic lethality. In its milder form, the OFT is foreshortened and misaligned, resulting in a double outlet right ventricle. Dll4-mediated Notch signaling maintains Fgf8 expression by transcriptional regulation at the promoter level. Combined heterozygous knockout of Dll4 and Fgf8 demonstrates genetic synergy in OFT alignment. Exogenous supplemental Fgf8 rescues proliferation in Dll4 mutants in ex-vivo culture. Our results establish a novel role for Dll4-mediated Notch signaling in SHF biology. More broadly, our model provides a platform for understanding oligogenic inheritance that results in clinically relevant OFT malformations.

A phase Ib study of sEphB4-HSA combined with first-line chemotherapy in patients (pts) with advanced pancreatic (PC) and biliary cancers (BC)

4640

Background: EphB4, a receptor kinase expressed in most epithelial tumors, binds EphrinB2 to affect cancer cell growth, apoptosis and angiogenesis. EphB4 overexpression is associated with advanced stage and shorter survival in multiple cancers. sEphB4-HSA, the albumin-bound extracellular fragment of EphB4, is a first-in-class inhibitor which blocks EphB4-EphrinB2 bidirectional signaling and results in downstream suppression of KRAS, PI3K, and promotes recruitment of CD3 and CD8 T cells into the tumor. The RP2D of sEphB4-HSA is 10 mg/Kg IV q week. Here, we report on sEphB4-HSA in combination with standard first-line chemotherapy. Methods: Pts with advanced PC or BC and no prior therapy for metastatic disease were eligible and enrolled into separate cohorts. Pts with PC received gemcitabine 1,000 mg/m2 + nab-paclitaxel 125 mg/m2 on Days 1, 8, 15 of a 28-day cycle. Pts with BC received gemcitabine 1,000 mg/m2 + cisplatin 25 mg/m2 on Days 1, 8 of a 21-day cycle. sEphB4-HSA 10 mg/kg IV was given weekly starting in Cycle 2. Response was assessed every 2 cycles. Primary endpoint was safety and tolerability; secondary endpoints were objective response rate (ORR) by RECIST 1.1, PFS, OS. Expression of EphrinB2 and EphB4 in tumor was examined by IHC and classified as 1+ (weak staining); 2+ (moderate staining); 3+ (strong, uniform staining). Results: A total of 44 pts with advanced PC (n = 21) and BC (n = 23; 70% gallbladder cancer) were enrolled. Median age 66 yrs; ECOG 1 (70%), 52% male. Median number of cycles received were 5 (PC) and 7 (BC). Median PFS was 5.6 mo in PC and 5.8 mo in BC (95% CI: 3.1-8.1 [PC]; 2.7-7.0 [BC]). Median OS was 7.9 mo in PC and 9.1 mo in BC (95% CI: 6.5-15.0 [PC]; 5.4-15.0 [BC]). In response evaluable pts (20 PC, 22 BC), ORR was 40% in PC (95% CI: 21%, 63%) and 23% in BC (95% CI: 9%, 45%). Stable disease was noted in 48% of PC and 61% of BC pts. The most common grade 3 or 4 treatment-related AEs in ≥10% of pts in both cohorts combined were hypertension (n = 16; 36%), neutropenia (n = 15; 34%), anemia (n = 14; 32%), thrombocytopenia (n = 7, 16%), fatigue (n = 7, 16%). In the PC cohort, there was an association between EphB4 expression and objective response (p = 0.009). Conclusions: sEphB4-HSA has a manageable safety profile in combination with chemotherapy in pts with PC and BC. Clinical activity is manifested by a high disease control rate in both cohorts and a promising RR in PC. Additional biomarker analyses will be presented. Future studies combining chemoimmunotherapy with sEphB4-HSA in pancreatic cancer are planned. Clinical trial information: NCT02495896 .

Programmed Death 1 and Programmed Death Ligand 1 Inhibitors in Advanced and Recurrent Urothelial Carcinoma: Meta-analysis of Single-Agent Studies

We performed a systematic review and meta-analysis on the response rates of patients with treatment-refractory urothelial carcinoma treated with programmed cell death 1 (PD-1) and programmed death ligand 1 (PD-L1) inhibitors. We reviewed the literature for prospective studies evaluating PD-1/PD-L1 inhibitors in refractory urothelial carcinoma patients, which formed the basis for US Food and Drug Administration approval of 5 different antagonistic antibodies targeting PD-1 or PD-L1 (atezolizumab, durvalumab, avelumab, nivolumab, and pembrolizumab). We considered studies examining PD-1/PD-L1-treated patients, which we identified using the following key terms in the Pubmed, Scopus, Web of Science, ClinicalTrial.gov, and Cochrane Library databases. Eligible studies had ≥ 20 patients each and reported response rates, duration of response, and overall survival (OS). We performed fixed and random-effects meta-analyses to model the point estimates for objective response rate and complete response. The median progression-free survival (PFS) and OS for studies reporting these statistics were evaluated. We found 10 eligible studies that met our inclusion criteria, providing extractable numerators and denominators for response rates, PFS, and OS for 1934 patients with metastatic urothelial carcinoma. The objective response rate was 18% (95% confidence interval, 15-22) for second-line or later therapies. The random-effects estimate for complete response was 4% (95% confidence interval, 3-5), including all disease locations and all PD-1 and PD-L1 inhibitors. Median OS and PFS were < 13 months and 3 months, respectively, across all studies, irrespective of PD-L1 expression. We found that the estimated response rates of agents included in this meta-analysis seem to be more favorable than other salvage therapies.

EPHB4 inhibition activates ER stress to promote immunogenic cell death of prostate cancer cells

The EPHB4 receptor is implicated in the development of several epithelial tumors and is a promising therapeutic target, including in prostate tumors in which EPHB4 is overexpressed and promotes tumorigenicity. Here, we show that high expression of EPHB4 correlated with poor survival in prostate cancer patients and EPHB4 inhibition induced cell death in both hormone sensitive and castration-resistant prostate cancer cells. EPHB4 inhibition reduced expression of the glucose transporter, GLUT3, impaired glucose uptake, and reduced cellular ATP levels. This was associated with the activation of endoplasmic reticulum stress and tumor cell death with features of immunogenic cell death (ICD), including phosphorylation of eIF2α, increased cell surface calreticulin levels, and release of HMGB1 and ATP. The changes in tumor cell metabolism after EPHB4 inhibition were associated with MYC downregulation, likely mediated by the SRC/p38 MAPK/4EBP1 signaling cascade, known to impair cap-dependent translation. Together, our study indicates a role for EPHB4 inhibition in the induction of immunogenic cell death with implication for prostate cancer therapy.

GRP78 regulates CD44v membrane homeostasis and cell spreading in tamoxifen-resistant breast cancer

GRP78 conducts protein folding and quality control in the ER and shows elevated expression and cell surface translocation in advanced tumors. However, the underlying mechanisms enabling GRP78 to exert novel signaling functions at cell surface are just emerging. CD44 is a transmembrane protein and an important regulator of cancer metastasis, and isoform switch of CD44 through incorporating additional variable exons to the extracellular juxtamembrane region is frequently observed during cancer progression. Using super-resolution dual-color single-particle tracking, we report that GRP78 interacts with CD44v in plasma membrane nanodomains of breast cancer cells. We further show that targeting cell surface GRP78 by the antibodies can effectively reduce cell surface expression of CD44v and cell spreading of tamoxifen-resistant breast cancer cells. Our results uncover new functions of GRP78 as an interacting partner of CD44v and as a regulator of CD44v membrane homeostasis and cell spreading. This study also provides new insights into anti-CD44 therapy in tamoxifen-resistant breast cancer.

EphB4-EphrinB2 receptor-ligand pair as a novel target in prostate cancer (PC)

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Background: Studies have shown that EphB4 (B4), a receptor kinase, is upregulated in PC. The ligand for B4, EphrinB2 (B2) has not been studied in PC thus far. In our PTEN null mouse PC model, B4 and B2 are both upregulated in PC, but not in normal prostate. Furthermore, Soluble B4-albumin (sB4) decoy receptor blocks B4-B2 bidirectional signaling, inhibits PI3K/AKT signaling and is currently in phase II clinical trials in multiple tumor types. We thus studied B2 expression in human PCs and normal tissues. Methods: B2 levels were studied in 180 clinically localized human PCs and normal prostates. Tissue staining was performed with specific monoclonal antibody, using LEICA platform. B2 expressions in tumor vessel, tumor cell and stromal cells were scored by a pathologist. In addition, a CRPC patient was treated with sB4 under an IND approved by the FDA and IRB. The patient’s prostate cancer was diagnosed in 2014, Gleason’s score 4+3, treated with radical prostatectomy (pT3bN0) with subsequent metastases bone/bone marrow and progression on sipuleucel T, enzalutamide, abiraterone, docetaxel, cabazitaxel, and carboplatin. Tumor and blood samples were obtained and analyzed after informed consent. Results: B2 was not expressed in any of the 40 normal prostate gland or normal vessels in bladder, pancreas, small intestine, liver, adrenal glands, skeletal muscle, and bone marrow tissues. B2 was expressed 50% of the human prostate cancer tissues, being positive in tumor cells and negative in vascular and stromal cells. Expression was correlated with Gleason score (p = 0.003). B2 was also upregulated in PC cell lines that are characterized for genomic, and epigenomic alterations to study mechanisms of B2 induction. Metastatic tumor tissue from the CRPC patient showed high elevation of B2. After a 4-week course of sB4, PSA level declined by 45% (from 2284 to 1257). PI3K and AR levels in tumor tissue declined compared to baseline. PI3K/AKT/pS6 and AR levels in tumor tissue ex-vivo studies were also reduced with sB4 exposure. Conclusions: B2 is expressed in half of PCs and our experiments suggest a significant role for the EphB4-EphrinB2 pair through regulation of PI3K and AR signaling. Given the central role of AR in PC, sB4 may offer a novel approach to targeting AR.

Carbohydrate restriction for glycaemic control in Type 2 diabetes: a systematic review and meta-analysis

AIM

To conduct a systematic review and meta-analysis to evaluate the effect of carbohydrate restriction on glycaemic control in Type 2 diabetes.

METHODS

We searched Medline, EMBASE and CINAHL for the period between 1976 and April 2018. We included randomized controlled trials comparing carbohydrate restriction with a control diet which aimed to maintain or increase carbohydrate intake, and that reported HbA_1c as an outcome and reported the amount of carbohydrate consumed during or at the end of the study, with outcomes reported at ≥3 months.

RESULTS

We identified 1402 randomized controlled trials, 25 of which met the inclusion criteria, incorporating 2132 participants for the main outcome. Definitions of low carbohydrate varied among the studies. The pooled effect estimate from meta-analysis was a weighted mean difference of -0.09% [95% CI -0.27, 0.08 (P = 0.30); I² 72% (P <0.001)], suggesting no effect on HbA_1c of restricting the quantity of carbohydrate. A subgroup analysis of diets containing 50-130 g carbohydrate resulted in a pooled effect estimate of -0.49% [95% CI -0.75, -0.23 (P <0.001); I² 0% (P = 0.56)], suggesting a clinically and statistically significant effect on HbA_1c in favour of low-carbohydrate diets in studies of ≤6 months' duration.

CONCLUSIONS

There was no overall pooled effect on HbA_1c in favour of restricting carbohydrate; however, restriction of carbohydrate to 50-130 g per day had beneficial effects on HbA_1c in trials up to 6 months. Future randomized controlled trials should be of >12 months' duration, assess pre-study carbohydrate intake, use recognized definitions of low-carbohydrate diets and examine reasons for non-adherence to prescribed diets in greater detail.

A first-in-human phase I study of sEphB4-HSA (sEphB4) with expansion in hepatocellular (HCC) and cholangiocarcinoma (CCA)

285

Background: EphrinB4, a receptor kinase, is associated with stage and survival in epithelial cancers. sEphB4 is a fusion protein of soluble EphB4 and albumin. sEphB4 binds to EphrinB2, a protein expressed in tumor cells and vessels, and blocks bidirectional signaling. sEphB4 downregulates the PI3K/AKT/mTOR pathway, inhibits angiogenesis, and promotes recruitment of cytotoxic T cells and NK cells. MTD was not reached during dose escalation. The RP2D was 10 mg/Kg weekly. Here we report the results of the expansion cohorts in HCC and CCA. Methods: The study evaluated the safety, PK, PD and efficacy of sEphB4 in pts with advanced solid tumors in a 3+3 design with expansion at the RP2D in 7 solid tumors including HCC and CCA. Pts received sEphB4 10 mg/kg IV weekly in 28-day cycles. Eligibility included ECOG 0-1, Child-Pugh score ≤ 7, platelets > 50,000, AST/ALT ≤ 3xULN, serum bilirubin ≤ 1.5mg/dL and no uncontrolled hypertension. Results: 29 pts were treated: 17 HCC and 12 biliary cancers (8 CCA and 4 gallbladder). Median age was 63(25-77). ECOG PS was 1 in 76%. Median prior regimens were 1 (0-6) for HCC and 2 (1-3) for biliary cancers. 2 HCC pts had prior liver transplantation, 9 had prior anti PD-1 therapy and 2 had Child-Pugh score of B7. Median number of cycles was 4 (1-21) in HCC and 2 (1-17) in CCA. No grade 4 treatment-related adverse events (TRAE). Grade 3 TRAE were hypertension (41%) and fatigue, headache, neutropenia all in 1 pt each. Disease progression was the most common reason for treatment discontinuation. Median PFS in months was 5.0 (3.0-7.5) in HCC and 3.0 (1.6-9.2) in CCA. Median OS in months was 27.1 (4.4-27.1) in HCC and 12.0 (3.0-28.2) in CCA. Disease control rate was 70% in HCC and 42% in CCA including 1 PR in HCC. In HCC pts, 5/5 with 3+ EphrinB2 expression in tumor had PR or SD ≥ 6 months. Only 1/4 pts with ≤2+ expression had SD ≥ 4 months. 3/3 pts with HCC showed an increase in T cell infiltration, and decrease in pS6 (PI3K pathway activity) on post-treatment biopsy. Conclusions: sEphB4 has a manageable safety profile with preliminary evidence of anti-tumor activity in pretreated pts with HCC and biliary cancers. Several trials combining sEphB4-HSA with cytotoxic chemotherapy or immunotherapy are ongoing. Clinical trial information: NCT01642342.

Prevalence and molecular epidemiology of porcine cysticercosis in naturally infected pigs (Sus scrofa) in Punjab, India

Porcine cysticercosis is a serious zoonosis in resource-poor countries. Despite the evidence showing that the disease is endemic in the Punjab region of India, molecular characterisation of Taenia solium cysticercosis from naturally infected pigs has not been carried out. The authors examined a total of 519 pigs slaughtered in small slaughter shops (shops that sell meat from animals that are slaughtered on the premises as the customer waits) in the urban slums of Punjab state in northern India. The expected polymerase chain reaction products with molecular sizes of 286 bp, 420 bp, 1150 bp and 333 bp corresponding to the targeted large subunit ribosomal RNA (rRNA), cytochrome oxidase 1, internal transcribed spacer 1, and diagnostic antigen Ts14 genes, respectively, were amplified from the cysts collected from all 22 infected carcasses. The detection limits for the respective primers (except those targeting the Ts14 gene) were estimated. The analytical sensitivities of both the TBR and JB primers (targeting the rRNA and cytochrome oxidase genes, respectively) were found to be higher (10 pg) than that of the internal transcribed spacer 1 gene (1 ng) primers. Ten representative samples from cytochrome oxidase 1 gene amplified products were sequenced in both directions for phylogenetic analysis. Sequencing demonstrated that all cysticerci were of the Asian genotype of T. solium and not of the African/Latin American genotype or T. asiatica. The results confirm the presence of T. solium porcine cysticercosis in Punjab state and there is therefore an urgent need for science-based policies for prevention and control of this serious zoonosis.

Global phosphotyrosine survey in triple-negative breast cancer reveals activation of multiple tyrosine kinase signaling pathways

Breast cancer is the most prevalent cancer in women worldwide. About 15-20% of all breast cancers are triple negative breast cancer (TNBC) and are often highly aggressive when compared to other subtypes of breast cancers. To better characterize the biology that underlies the TNBC phenotype, we profiled the phosphotyrosine proteome of a panel of twenty-six TNBC cell lines using quantitative high resolution Fourier transform mass spectrometry. A heterogeneous pattern of tyrosine kinase activation was observed based on 1,789 tyrosine-phosphorylated peptides identified from 969 proteins. One of the tyrosine kinases, AXL, was found to be activated in a majority of aggressive TNBC cell lines and was accompanied by a higher level of AXL expression. High levels of AXL expression are correlated with a significant decrease in patient survival. Treatment of cells bearing activated AXL with a humanized AXL antibody inhibited cell proliferation and migration in vitro, and tumor growth in mice. Overall, our global phosphoproteomic analysis provided new insights into the heterogeneity in the activation status of tyrosine kinase pathways in TNBCs. Our approach presents an effective means of identifying important novel biomarkers and targets for therapy such as AXL in TNBC.

PET Imaging of Dll4 Expression in Glioblastoma and Colorectal Cancer Xenografts Using (64)Cu-Labeled Monoclonal Antibody 61B

Delta-like ligand 4 (Dll4) expressed in tumor cells plays a key role to promote tumor growth of numerous cancer types. Based on a novel antihuman Dll4 monoclonal antibody (61B), we developed a (64)Cu-labeled probe for positron emission tomography (PET) imaging of tumor Dll4 expression. In this study, 61B was conjugated with the (64)Cu-chelator DOTA through lysine on the antibody. Human IgG (hIgG)-DOTA, which did not bind to Dll4, was also prepared as a control. The Dll4 binding activity of the probes was evaluated through the bead-based binding assay with Dll4-alkaline phosphatase. The resulting PET probes were evaluated in U87MG glioblastoma and HT29 colorectal cancer xenografts in athymic nude mice. Our results demonstrated that the 61B-DOTA retained (77.2 ± 3.7) % Dll4 binding activity of the unmodified 61B, which is significantly higher than that of hIgG-DOTA (0.06 ± 0.03) %. Confocal microscopy analysis confirmed that 61B-Cy5.5, but not IgG-Cy5.5, predominantly located within the U87MG and HT29 cells cytoplasm. U87MG cells showed higher 61B-Cy5.5 binding as compared to HT29 cells. In U87MG xenografts, 61B-DOTA-(64)Cu demonstrated remarkable tumor accumulation (10.5 ± 1.7 and 10.2 ± 1.2%ID/g at 24 and 48 h postinjection, respectively). In HT29 xenografts, tumor accumulation of 61B-DOTA-(64)Cu was significantly lower than that of U87MG (7.3 ± 1.3 and 6.6 ± 1.3%ID/g at 24 and 48 h postinjection, respectively). The tumor accumulation of 61B-DOTA-(64)Cu was significantly higher than that of hIgG-DOTA-(64)Cu in both xenografts models. Immunofluorescence staining of the tumor tissues further confirmed that tumor accumulation of 61B-Cy5.5 was correlated well with in vivo PET imaging data using 61B-DOTA-(64)Cu. In conclusion, 61B-DOTA-(64)Cu PET probe was successfully synthesized and demonstrated prominent tumor uptake by targeting Dll4. 61B-DOTA-(64)Cu has great potential to be used for noninvasive Dll4 imaging, which could be valuable for tumor detection, Dll4 expression level evaluation, and Dll4-based treatment monitoring.

Abstract 2090: GLI3 repressor levels determine Hedgehog pathway activity and predict response to Smoothened antagonist in acute myeloid leukemia

The Hedgehog (Hh) signaling pathway is activated in most hematological and solid cancers and is a promising target for therapeutic development. Deletions in the receptor Patched (PTCH) or activating mutations in the upstream positive regulator Smoothened (SMO) have been reported in a few cancers such as basal cell carcinoma and medulloblastoma, but are largely absent in most tumor types; therefore, the mechanism of pathway activation in most cancers remains unknown. In normal tissues, Hh pathway activation via PTCH/SMO causes an increase in the downstream activating transcription factor GLI1 and a decrease in the transcriptional repressor GLI3R. We confirm that the Hh pathway is active in acute myeloid leukemia (AML) and is required for cell survival, however, this activity is largely independent of the upstream activator SMO. Using siRNA knock down of GLI1, GLI3 and SMO in AML cell lines, Gli3 conditional knock out mice, and primary AML samples, we are able to show that loss of the GLI3R repressor function is sufficient to activate Hh target gene expression independent of ligand binding, and GLI3R levels correlate inversely with GLI1 levels. Importantly, we show that GLI3R is required for the therapeutic effect of SMO antagonists in AML samples and restoration of GLI3R restores sensitivity to SMO antagonists in AML cell lines. Epigenetic and gene expression analysis of the TCGA AML data set reveals that the GLI3 expression is silenced in most AML patient samples. We demonstrate in vitro and in patients that treatment with hypomethylating agents restores GLI3R levels and sensitivity to SMO antagonists in AML. In a transgenic mouse model of myeloproliferative disease (vav-Jak2V617F, gift of Joe Zhao, OUHSC) effective treatment with SMO antagonists are associated with increases in GLI3R but no changes in GLI1. Finally we show that GLI3R can directly repress expression of AKT and in vivo responses to SMO antagonists are correlated with changes in AKT expression, independent of GLI1 levels. In summary, this study provides the first evidence that GLI3R plays an essential role in SMO independent Hh signaling in AML, and suggests that GLI3R could serve as a potential biomarker for patient selection in SMO antagonist clinical trials. Furthermore, these data provide important mechanistic data to support rational combinations of hypomethylating agents with SMO antagonists in clinical trials.

Citation Format: Parvesh Chaudhry, Mohan Singh, Tim Triche, Aparna Jorapur, Parkash S. Gill, Akil Merchant. GLI3 repressor levels determine Hedgehog pathway activity and predict response to Smoothened antagonist in acute myeloid leukemia. [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 2090. doi:10.1158/1538-7445.AM2015-2090

Abstract 407: Modulation of Delta-Like Ligand-4 Signaling Improves Myocardial Revascularization Following Coronary Ischemia

Delta-like ligand-4 (DLL4) is an arterial-specific Notch ligand and balanced signaling by DLL4 is required for functional neovascularization. We hypothesized that modest inhibition of DLL4 signaling improves myocardial revascularization following coronary ischemia. Myocardial infarction was induced by ligation of mid-left anterior descending (LAD) artery via rapid left thoracotomy in 6-8 week-old male mice with inducible endothelial-specific knockout or overexpression of DLL4. DLL4 silencing in homozygous mice on the day of or 5 days prior to LAD ligation resulted in significant reduction in revascularization. At four weeks, explanted hearts showed 1.8-fold fewer vessels in LAD territory, 3-fold greater myocardial hypoxia, 1.7-fold larger fibrotic scar and 17% increased perfusion defect in the left ventricle (LV) by scintigraphy. CT angiography confirmed fewer collateral vessels. Echocardiography showed increased LV dilation (37% higher end-diastolic volume) and 12% greater reduction in ejection fraction (EF) compared to baseline (all p<0.001). Overexpression of DLL4 showed a similarly worse outcome. Conversely, partial DLL4 knockout in heterozygous animals resulted in improved outcomes in all parameters. For translational application, animals were systemically administered 1.5mg/kg or 3mg/kg DLL4-Fc intraperitoneally three times a week beginning the day of ligation. RT-PCR analysis of downstream molecules confirmed that systemic DLL4-Fc partially inhibits Notch signaling in endothelial cells in the ischemic LV. When LAD was ligated very proximally, DLL4-Fc improved survival. With mid-LAD ligation, DLL4-Fc induced a dose-dependent increase in number of CD 31-positive vessels and by CT angiography. There was a dose-dependent reduction in hypoxic myocardial area, scar burden, and scintigraphic perfusion defect. DLL4-Fc treated mice had lower end-diastolic LV volume and preserved or improved EF. In an ischemia-reperfusion model, DLL4-Fc increased the number of vessels in the ischemic zone. Our data suggests that balanced DLL4 signaling is crucially required for myocardial angiogenic recovery following coronary ischemia. Modulation of DLL4 signaling has translational therapeutic potential.

Novel EPHB4 Receptor Tyrosine Kinase Mutations and Kinomic Pathway Analysis in Lung Cancer

Lung cancer outcomes remain poor despite the identification of several potential therapeutic targets. The EPHB4 receptor tyrosine kinase (RTK) has recently emerged as an oncogenic factor in many cancers, including lung cancer. Mutations of EPHB4 in lung cancers have previously been identified, though their significance remains unknown. Here, we report the identification of novel EPHB4 mutations that lead to putative structural alterations as well as increased cellular proliferation and motility. We also conducted a bioinformatic analysis of these mutations to demonstrate that they are mutually exclusive from other common RTK variants in lung cancer, that they correspond to analogous sites of other RTKs’ variations in cancers, and that they are predicted to be oncogenic based on biochemical, evolutionary, and domain-function constraints. Finally, we show that EPHB4 mutations can induce broad changes in the kinome signature of lung cancer cells. Taken together, these data illuminate the role of EPHB4 in lung cancer and further identify EPHB4 as a potentially important therapeutic target.

Small-Animal PET Imaging of Pancreatic Cancer Xenografts Using a 64Cu-Labeled Monoclonal Antibody, MAb159

Overexpression of the GRP78 receptor on cell surfaces has been linked with tumor growth, metastasis, and resistance to therapy. We developed a (64)Cu-labeled probe for PET imaging of tumor GRP78 expression based on a novel anti-GRP78 monoclonal antibody, MAb159.

METHODS

MAb159 was conjugated with the (64)Cu-chelator DOTA through lysines on the antibody. DOTA-human IgG was also prepared as a control that did not bind to GRP78. The resulting PET probes were evaluated in BXPC3 pancreatic cancer xenografts in athymic nude mice.

RESULTS

The radiotracer was synthesized with a specific activity of 0.8 MBq/μg of antibody. In BXPC3 xenografts, (64)Cu-DOTA-MAb159 demonstrated prominent tumor accumulation (4.3 ± 1.2, 15.4 ± 2.6, and 18.3 ± 1.0 percentage injected dose per gram at 1, 17, and 48 after injection, respectively). In contrast, (64)Cu-DOTA-human IgG had low BXPC3 tumor accumulation (4.8 ± 0.5, 7.5 ± 0.7, and 4.6 ± 0.8 percentage injected dose per gram at 1, 17, and 48 h after injection, respectively).

CONCLUSION

We demonstrated that GRP78 can serve as a valid target for pancreatic cancer imaging. The success of this approach will be valuable for evaluating disease course and therapeutic efficacy at the earliest stages of anti-GRP78 treatment. Moreover, these newly developed probes may have important applications in other types of cancer overexpressing GRP78.

AXL Is a Logical Molecular Target in Head and Neck Squamous Cell Carcinoma

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) represents the eighth most common malignancy worldwide. Standard-of-care treatments for patients with HNSCC include surgery, radiation, and chemotherapy. In addition, the anti-EGFR monoclonal antibody cetuximab is often used in combination with these treatment modalities. Despite clinical success with these therapeutics, HNSCC remains a difficult malignancy to treat. Thus, identification of new molecular targets is critical.

EXPERIMENTAL DESIGN

In the current study, the receptor tyrosine kinase AXL was investigated as a molecular target in HNSCC using established cell lines, HNSCC patient-derived xenografts (PDX), and human tumors. HNSCC dependency on AXL was evaluated with both anti-AXL siRNAs and the small-molecule AXL inhibitor R428. Furthermore, AXL inhibition was evaluated with standard-of-care treatment regimens used in HNSCC.

RESULTS

AXL was found to be highly overexpressed in several models of HNSCC, where AXL was significantly associated with higher pathologic grade, presence of distant metastases, and shorter relapse-free survival in patients with HNSCC. Further investigations indicated that HNSCC cells were reliant on AXL for cellular proliferation, migration, and invasion. In addition, targeting AXL increased HNSCC cell line sensitivity to chemotherapy, cetuximab, and radiation. Moreover, radiation-resistant HNSCC cell line xenografts and PDXs expressed elevated levels of both total and activated AXL, indicating a role for AXL in radiation resistance.

CONCLUSIONS

This study provides evidence for the role of AXL in HNSCC pathogenesis and supports further preclinical and clinical evaluation of anti-AXL therapeutics for the treatment of patients with HNSCC.

Axl-targeted cancer imaging with humanized antibody h173

PURPOSE

The tyrosine kinase receptor Axl is overexpressed in various types of cancer and correlated with cancer malignancy. Selective Axl blockade reduces tumor growth and metastasis. The purpose of this study was to examine whether the humanized anti-Axl antibody humanized 173 (h173) labeled with near-infrared fluorescence (NIRF) dye Cy5.5 could be applied as a molecular imaging probe for NIRF imaging of Axl expression in tumor models.

PROCEDURES

NIRF dye Cy5.5 was conjugated to h173 or human normal immunoglobulin G (hIgG) control through amino groups. The resulting probes were evaluated in both A549 (Axl positive) and NCI-H249 (Axl negative) lung cancer xenografts through in vivo NIRF imaging. Ex vivo imaging and probe distribution assay were also carried out to confirm the in vivo imaging results.

RESULTS

After conjugation, binding activity of h173-Cy5.5 was determined to be 97.75 % ± 2.09 % of the unmodified h173. In vitro fluorescence-activated cell sorting (FACS) and fluorescence microscopy analysis validated the specific binding of h173 toward Axl-positive A549 cells. h173-Cy5.5 was then applied to image Axl expression in vivo. In A549 (Axl positive) cancer xenografts, the tumor uptake of h173-Cy5.5 was significantly higher than that of the hIgG-Cy5.5 control (P < 0.05) at late time points (1, 2, 3, 4, and 7 days). On the contrary, in NCI-H249 (Axl negative) cancer xenografts, the tumor uptake of both hIgG-Cy5.5 and h173-Cy5.5 was low and showed no significant difference (P > 0.05) at all time points examined. Ex vivo imaging and immunofluorescence staining analysis further validated the in vivo imaging results.

CONCLUSIONS

Collectively, all in vitro, in vivo, and ex vivo data suggested that h173-Cy5.5 could serve as a valid probe for Axl-targeted cancer imaging, which could therefore aid in tumor diagnosis, prognosis, and treatment monitoring.

Expression of the EPHB4 receptor tyrosine kinase in head and neck and renal malignancies--implications for solid tumors and potential for therapeutic inhibition

Solid malignancies are often characterized by overexpression of various receptor tyrosine kinases (RTKs) against which many targeted therapies are currently in use and in active development. EPHB4 has recently emerged as a frequently overexpressed RTK in many types of cancer. Here, we demonstrate expression patterns of EPHB4 in two solid malignancies: squamous cell carcinoma of the head and neck (HNSCC) and renal cell carcinoma (RCC), by immunohistochemical analysis. We demonstrate the first association between EPHB4 expression and progression of HNSCC from normal tissue to dysplasia and to cancer. Interestingly, most RCC subtypes exhibited expression patterns that were opposite from that found in HNSCC, possibly owing to their unique biology and high degree of organ and tumor vasculature. Taken together, these results suggest a possible role for EPHB4 as a therapeutic target in these malignancies.

Abstract 1758: Targeting EphB4 with a novel antibody in acute leukemia

Introduction: EphB4, a receptor tyrosine kinase, binds to ephrinB2, a cell surface ligand, resulting in bidirectional signaling through both receptor and ligand. EphB4 stimulates cell proliferation and migration through the phosphatidylinositol 3-kinase (PI3K) and Akt signaling pathway. MAb131 is a novel anti-EphB4 monoclonal antibody that induces degradation of EphB4 through receptor endocytosis. We investigated the use of MAb131 as a therapeutic agent for acute leukemia.

Methods: Peripheral blood or bone marrow specimens from patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) were obtained after informed consent. EphB4 and ephrinB2 expression in cells were profiled using flow cytometry. Cell lines and patient samples were treated with MAb131 at 0, 10 and 100ug/ml concentrations. Blocking experiment was performed with 200ug/ml sEphB4-HSA in combination with 10ug/ml MAb131. Downregulation of EphB4 was evaluated by flow cytometry. Phosphorylated AKT (pAKT) levels were measured by Western blot. Cell viability was measured by trypan blue exclusion.

Results: EphB4 was highly expressed on the cell surface in the majority of leukemia cell lines of both myeloid (K562, Molm14, U937) and lymphoid (REH, RS4;11, Jurkat) origin; only one leukemia cell line evaluated, KG-1, did not express EphB4. In contrast, none of the lymphoma cell lines (BJAB, Ramos, Namwala) expressed EphB4. Of 9 AML patient samples evaluated, 4 expressed high levels of EphB4, and 5 expressed low levels of EphB4. Of 7 ALL patient samples evaluated, 2 expressed high levels of EphB4, 3 had low expression and 2 did not express EphB4. None of the cells showed robust expression of ephrinB2. Treatment of ALL and AML cell lines with MAb131 induced downregulation of EphB4, decreased levels of pAKT, and &gt;90% cell death after 72h. Primary AML and ALL samples also showed downregulation of surface EphB4 and increased cell death with MAb131 treatment. A decoy receptor comprised of the soluble extracellular domain of EphB4 fused to albumin (sEphB4-HSA) was used to block MAb131 binding to EphB4 and confirm specificity of MAb131 activity.

Conclusion: We present the first report that EphB4 signaling is active in acute leukemia and can be targeted therapeutically. MAb131, a novel anti-EphB4 antibody, has potent anti-leukemic activity as a single agent in vitro and is likely to sensitize leukemia to cytotoxic chemotherapy through downregulation of AKT signaling. Based on these results, clinical studies exploring the efficacy of EphB4/ephrinB2 antagonists in patients with acute leukemia should be pursued.

Citation Format: Miriam Y. Kim, Aparna Jorapur, Amy R. McManus, Ren Liu, Valery Krasnoperov, Kranthi Naga, Parkash S. Gill, Akil Merchant. Targeting EphB4 with a novel antibody in acute leukemia. [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 1758. doi:10.1158/1538-7445.AM2014-1758

The differential expression of EphB2 and EphB4 receptor kinases in normal bladder and in transitional cell carcinoma of the bladder

Effective treatment of transitional cell carcinoma (TCC) of the bladder requires early diagnosis. Identifying novel molecular markers in TCC would guide the development of diagnostic and therapeutic targets. Ephrins mediate signals via tyrosine kinase activity that modulates diverse physiologic and developmental processes, and ephrins are increasingly implicated in carcinogenesis. The aim of our study was to examine the differential regulation of EphB4 and EphB2 in normal bladder and in TCC of the bladder in 40 patients undergoing radical cystectomy for curative intent. Immunostaining and Western blotting revealed that normal urothelium expresses EphB2 (20 of 24 cases, 83% of the time) not EphB4 (0 of 24 cases, 0%). In sharp contrast, TCC specimens show loss of EphB2 expression (0 of 34 cases, 0%) and gain of EphB4 expression (32 of 34, 94%). Furthermore, EphB4 signal strength statistically correlated with higher tumor stage, and trended toward the presence of carcinoma in situ (CIS). These results are confirmed by analysis of normal urothelial and tumor cell lines. EphB2 is not a survival factor in normal urothelium, while EphB4 is a survival factor in TCC. Treatment of bladder tumor xenograft with an EphB4 inhibitor sEphB4-HSA leads to 62% tumor regression and complete remission when combined with Bevacizumab. Furthermore, tissue analysis revealed that sEphB4-HSA led to increased apoptosis, decreased proliferation, and reduced vessel density, implicating direct tumor cell targeting as well as anti-angiogenesis effect. In summary loss of EphB2 and gain of EphB4 expression represents an inflection point in the development, growth and possibly progression of TCC. Therapeutic compounds targeting EphB4 have potential for diagnosing and treating TCC.

AXL mediates resistance to cetuximab therapy

The EGFR antibody cetuximab is used to treat numerous cancers, but intrinsic and acquired resistance to this agent is a common clinical outcome. In this study, we show that overexpression of the oncogenic receptor tyrosine kinase AXL is sufficient to mediate acquired resistance to cetuximab in models of non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC), where AXL was overexpressed, activated, and tightly associated with EGFR expression in cells resistant to cetuximab (Ctx(R) cells). Using RNAi methods and novel AXL-targeting agents, we found that AXL activation stimulated cell proliferation, EGFR activation, and MAPK signaling in Ctx(R) cells. Notably, EGFR directly regulated the expression of AXL mRNA through MAPK signaling and the transcription factor c-Jun in Ctx(R) cells, creating a positive feedback loop that maintained EGFR activation by AXL. Cetuximab-sensitive parental cells were rendered resistant to cetuximab by stable overexpression of AXL or stimulation with EGFR ligands, the latter of which increased AXL activity and association with the EGFR. In tumor xenograft models, the development of resistance following prolonged treatment with cetuximab was associated with AXL hyperactivation and EGFR association. Furthermore, in an examination of patient-derived xenografts established from surgically resected HNSCCs, AXL was overexpressed and activated in tumors that displayed intrinsic resistance to cetuximab. Collectively, our results identify AXL as a key mediator of cetuximab resistance, providing a rationale for clinical evaluation of AXL-targeting drugs to treat cetuximab-resistant cancers. Cancer Res; 74(18); 5152-64. ©2014 AACR.

Design, synthesis, and validation of Axl-targeted monoclonal antibody probe for microPET imaging in human lung cancer xenograft

Accumulating experimental evidence indicates that overexpression of the oncogenic receptor tyrosine kinase, Axl, plays a key role in the tumorigenesis and metastasis of various types of cancer. The objective of this study is to design a novel imaging probe based on the monoclonal antibody, h173, for microPET imaging of Axl expression in human lung cancer. A bifunctional chelator, DOTA, was conjugated to h173, followed by radiolabeling with (64)Cu. The binding of DOTA-h173 to the Axl receptor was first evaluated by a cell uptake assay and flow cytometry analysis using human lung cancer cell lines. The probe (64)Cu-DOTA-h173 was further evaluated by microPET imaging, and ex vivo histology studies in the Axl-positive A549 tumors. In vitro cellular study showed that Axl probe, (64)Cu-DOTA-h173, was highly immuno-reactive with A549 cells. Western blot analysis confirmed that Axl is highly expressed in the A549 cell line. For microPET imaging, the A549 xenografts demonstrated a significantly higher (64)Cu-DOTA-h173 uptake compared to the NCI-H249 xenograft (a negative control model). Furthermore, (64)Cu-DOTA-h173 uptake in A549 is significantly higher than that of (64)Cu-DOTA-hIgG. Immuno-fluorescence staining was consistent with the in vivo micro-PET imaging results. In conclusion, (64)Cu-DOTA-h173 could be potentially used as a probe for noninvasive imaging of Axl expression, which could collect important information regarding tumor response to Axl-targeted therapeutic interventions.

Hepatitis C, a silent threat to the community of Haryana, India: a community-based study

BACKGROUND

Hepatitis C is a global public health problem. As many as 12 million people may be chronically infected in India and most are unaware of it.

AIMS

To determine the incidence of hepatitis C in the Ratia block of the Fatehabad district, Haryana, India.

METHOD

This cross-sectional study was carried out by house-tohouse visits over 2 weeks. After obtaining written consent, a blood sample was drawn from suspected cases by a laboratory technician maintaining all necessary safety precautions and sterilization.

RESULTS

Of the samples, 1,630 (22.3 per cent) were found to be positive for hepatitis C by ELISA, 253 (15.5 per cent) patients were previously hepatitis C positive, and adults (21-60 years) were affected maximally (70.0 per cent).

CONCLUSION

The study emphasises the need for public awareness campaigns at various levels and prevention of HCV infection. It also suggests the need to develop and strengthen evaluation methodology for the Integrated Disease Surveillance Project (IDSP).

EphB4-targeted imaging with antibody h131, h131-F(ab')2 and h131-Fab

Accumulating evidence suggests that overexpression of the tyrosine kinase receptor EphB4, a mediator of vascular development, is a novel target for tumor diagnosis, prognosis and therapy. Noninvasive imaging of EphB4 expression could therefore be valuable for evaluating disease course and therapeutic efficacy at the earliest stages of anti-EphB4 treatment. In this study, we systematically investigated the use of anti-EphB4 antibody h131 (150 kDa) and its fragments (h131-F(ab')2, 110 kDa; h131-Fab, 50 kDa) for near-infrared fluorescence (NIRF) imaging of EphB4 expression in vivo. h131-F(ab')2 and h131-Fab were produced through pepsin and papain digestion of h131 respectively, whose purity was confirmed by FPLC and SDS-PAGE. After conjugation with Cy5.5, in vivo characteristics of h131, h131-F(ab')2 and h131-Fab were evaluated in EphB4-positive HT29 tumor model. Although h131-Cy5.5 demonstrated highest tumor uptake among these probes, its optimal tumor uptake level was obtained at 2 days post injection (p.i.). For h131-Fab-Cy5.5, maximum tumor uptake was achieved at 4 h p.i. However, no significant difference was observed between h131-Fab-Cy5.5 and hIgG-Fab-Cy5.5, indicating the tumor accumulation was mainly caused by passive targeting. In contrast, h131-F(ab')2-Cy5.5 demonstrated prominent tumor uptake at 6 h p.i. The target specificity was confirmed by hIgG-F(ab')2-Cy5.5 control and immunofluorescent staining. Collectively, h131-F(ab')2 exhibited prominent and specific tumor uptake at early time points, which suggests it is a promising agent for EphB4-targeted imaging.

Monoclonal antibody against cell surface GRP78 as a novel agent in suppressing PI3K/AKT signaling, tumor growth, and metastasis

PURPOSE

The ER chaperone GRP78 translocates to the surface of tumor cells and promotes survival, metastasis, and resistance to therapy. An oncogenic function of cell surface GRP78 has been attributed to the activation of the phosphoinositide 3-kinase (PI3K) pathway. We intend to use a novel anti-GRP78 monoclonal antibody (MAb159) to attenuate PI3K signaling and inhibit tumor growth and metastasis.

EXPERIMENTAL DESIGN

MAb159 was characterized biochemically. Antitumor activity was tested in cancer cell culture, tumor xenograft models, tumor metastasis models, and spontaneous tumor models. Cancer cells and tumor tissues were analyzed for PI3K activity. MAb159 was humanized and validated for diagnostic and therapeutic application.

RESULTS

MAb159 specifically recognized surface GRP78, triggered GRP78 endocytosis, and localized to tumors but not to normal organs in vivo. MAb159 inhibited tumor cell proliferation and enhanced tumor cell death both in vitro and in vivo. In MAb159-treated tumors, PI3K signaling was inhibited without compensatory MAPK pathway activation. Furthermore, MAb159 halted or reversed tumor progression in the spontaneous PTEN-loss-driven prostate and leukemia tumor models, and inhibited tumor growth and metastasis in xenograft models. Humanized MAb159, which retains high affinity, tumor specific localization, and the antitumor activity, was nontoxic in mice, and had desirable pharmacokinetics.

CONCLUSIONS

GRP78-specific antibody MAb159 modulates the PI3K pathway and inhibits tumor growth and metastasis. Humanized MAb159 will enter human trials shortly.

The EphB4 receptor tyrosine kinase promotes lung cancer growth: a potential novel therapeutic target

Despite progress in locoregional and systemic therapies, patient survival from lung cancer remains a challenge. Receptor tyrosine kinases are frequently implicated in lung cancer pathogenesis, and some tyrosine kinase inhibition strategies have been effective clinically. The EphB4 receptor tyrosine kinase has recently emerged as a potential target in several other cancers. We sought to systematically study the role of EphB4 in lung cancer. Here, we demonstrate that EphB4 is overexpressed 3-fold in lung tumors compared to paired normal tissues and frequently exhibits gene copy number increases in lung cancer. We also show that overexpression of EphB4 promotes cellular proliferation, colony formation, and motility, while EphB4 inhibition reduces cellular viability in vitro, halts the growth of established tumors in mouse xenograft models when used as a single-target strategy, and causes near-complete regression of established tumors when used in combination with paclitaxel. Taken together, these data suggest an important role for EphB4 as a potential novel therapeutic target in lung cancer. Clinical trials investigating the efficacy of anti-EphB4 therapies as well as combination therapy involving EphB4 inhibition may be warranted.

EphB4 as a therapeutic target in mesothelioma

Background

Malignant pleural mesothelioma (MPM) often develops decades following exposure to asbestos. Current best therapy produces a response in only half of patients, and the median survival with this therapy remains under a year. A search for novel targets and therapeutics is underway, and recently identified targets include VEGF, Notch, and EphB4-Ephrin-B2. Each of these targets has dual activity, promoting tumor cell growth as well as tumor angiogenesis.

Methods

We investigated EphB4 expression in 39 human mesothelioma tissues by immunohistochemistry. Xenograft tumors established with human mesothelioma cells were treated with an EphB4 inhibitor (monomeric soluble EphB4 fused to human serum albumin, or sEphB4-HSA). The combinatorial effect of sEphB4-HSA and biologic agent was also studied.

Results

EphB4 was overexpressed in 72% of mesothelioma tissues evaluated, with 85% of epithelioid and 38% of sarcomatoid subtypes demonstrating overexpression. The EphB4 inhibitor sEphB4-HSA was highly active as a single agent to inhibit tumor growth, accompanied by tumor cell apoptosis and inhibition of PI3K and Src signaling. Combination of sEphB4-HSA and the anti-VEGF antibody (Bevacizumab) was superior to each agent alone and led to complete tumor regression.

Conclusion

EphB4 is a potential therapeutic target in mesothelioma. Clinical investigation of sEphB4-HSA as a single agent and in combination with VEGF inhibitors is warranted.

PET imaging of colorectal and breast cancer by targeting EphB4 receptor with 64Cu-labeled hAb47 and hAb131 antibodies

Accumulating evidence suggests that ephrin type B receptor 4 (EphB4) plays a key role in the progression of numerous cancer types. In this study, we developed a series of (64)Cu-labeled antibodies for PET imaging of tumor EphB4 expression.

METHODS

Anti-EphB4 antibodies (hAb47 and hAb131) were conjugated with the (64)Cu-chelator DOTA through lysine, cysteine, or oligosaccharide on the antibody. DOTA-human IgG (hIgG) was also prepared as a control, which did not bind to EphB4. The EphB4 binding activity of these probes was evaluated through the bead-based binding assay with EphB4-alkaline phosphatase. The resulting PET probes were further evaluated in both HT29 (colorectal cancer) and MDA-MB-231 (breast cancer) xenografts.

RESULTS

All 3 conjugation methods retained most of the EphB4 binding activity of the antibodies (83.85% ± 3.82%, 76.25% ± 5.90%, 98.93% ± 3.75%, and 82.09% ± 4.14% for DOTA-Lys-hAb47, DOTA-Cys-hAb47, DOTA-Sug-hAb47, and DOTA-Lys-hAb131, respectively). Although DOTA-Sug-hAb47 demonstrated the highest receptor binding activity based on a EphB4 binding assay, the corresponding PET probe was trapped in the liver quickly in vivo. In HT29 xenografts, both (64)Cu-DOTA-Lys-hAb47 and (64)Cu-DOTA-Cys-hAb47 demonstrated prominent tumor accumulation, which reached a maximum at 48 h after injection (18.13 ± 1.73 percentage injected dose [%ID]/g and 11.81 ± 2.05 %ID/g, respectively). In contrast, (64)Cu-DOTA-Lys-hIgG had a low tumor accumulation, thus demonstrating the target specificity of EphB4-antibody-based probes. Moreover, (64)Cu-DOTA-Lys-hAb131 (29.48 ± 2.60 %ID/g) demonstrated significantly higher HT29 tumor accumulation than (64)Cu-DOTA-Lys-hAb47. (64)Cu-DOTA-Lys-hAb131 was also found to specifically accumulate in the MDA-MB-231 tumor model (12.96 ± 2.31 %ID/g).

CONCLUSION

We have demonstrated that EphB4 can serve as a valid target for colorectal and breast cancer imaging. This approach would be valuable for evaluating disease course and therapeutic efficacy at the earliest stages of anti-EphB4 treatment. Moreover, these newly developed probes may have important applications in other cancer types overexpressing EphB4.

Abstract 4087: Androgen receptor splice variants in mouse prostate cancer cell lines: altered distribution in lines derived from castration-resistant tumors relative to those primary tumors

Prostate cancer is sensitive to androgen deprivation at the primary androgen-dependent growth stage (ADCa). However, it invariably acquires resistance to androgen withdrawal leading to the recurrence of the castration-resistant prostate cancer (CRPC). Androgen receptor (AR) activity that is necessary for the normal prostate development remains active through both phases of the disease. Even at castrate levels of androgen AR remains functional, possibly through several non-mutually exclusive mechanisms including expression of constitutively active AR variants (ARVs). The full-length of AR (ARFL) is a 110 KDa nuclear hormone receptor composed of an N-terminal domain (NTD, exon1), DNA-binding domain (DBD, exon 2 and 3), a hinge region (exon 4), and the C-terminal ligand binding domain (LBD, exon 4-8). To date up to 15 different ARVs lacking LBD have been identified in human prostate cancer cell lines or specimens. It is thought that the altered biological properties of these ARVs may be, in part, correlated to the development of castration resistance. ARVs remain understudied in mouse prostate cancer cell lines; detection of only two ARVs was reported in a mouse cell line. A better definition of ARVs in distinct phases of this cancer in an appropriate mouse model should be valuable for insights into the role of ARVs in therapy and disease progression.

To this end, by using cell lines established from the conditional Pten deletion mouse model of prostate adenocarcinoma, we detected low molecular weight AR protein species (∼50 kDa - 80 kDa) besides the presence of the 110 kDa full-length. We performed 3’RACE and subsequent Sanger sequencing on cell lines derived from both ADCa (E-series) and CRPC stages (cE-series) and identified three different ARVs which we named as mARV-abc. Structurally, mARVa is analogous to the previously reported mAR-V4 and the human ARV567es which only lacks LBD domain retaining exon 1-4 followed by the inclusion of a cryptic exon 4 from intron 4 at the 3’-terminal sequence. More interestingly, we identified two novel ARV isoforms (mARV-b and -c) which merely contains the NTD encoded by exon 1 before the addition of specific sequences from different positions of intron 1. Although these mARVs occur in all the murine cell lines tested, their proportion appears to vary with respect to the stage of the disease from which the cell lines originated. In cE-series established from a CRPC tumor, novel ARVb and ARVc are more abundant than that in E-series from an ADCa tumor; in parallel, ARVa displays an opposite expression profile. These new findings together with the results of ongoing experiments, including the single cell expression analysis and on their biological activities of the splice variants will be discussed.

Citation Format: Mengmeng Liang, Helty A. Adisetiyo, Xiuqing Li, Ren Liu, Parkash S. Gill, Pradip Roy-Burman. Androgen receptor splice variants in mouse prostate cancer cell lines: altered distribution in lines derived from castration-resistant tumors relative to those primary tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4087. doi:10.1158/1538-7445.AM2013-4087

Abstract 4356: EphB4 as a novel therapeutic target for head-neck SCC

Introduction: Receptor tyrosine kinase EphB4 and its cognate trans-membrane ligand EphrinB2 regulate venous-artery determination and are critically required for fusion of vein and arterial compartments, as well as vessel maturation in development and in pathological angiogenesis. Aberrant induction of EphB4 in certain tumors and pro-tumor cell survival function independent of its role in tumor angiogenesis have been reported. We have studied the expression and function of EphB4 in head neck squamous cell cancer.

Methods: EphB4 expression in 78 freshly frozen head/neck squamous cell carcinoma tumor samples were studied by immunostaining, western blot analysis, gene copy number, and correlated with stage. Head/neck tumor cell lines also were studied for expression and significance of EphB4 expression on survival by knock down studies using EphB4 lentiviral shRNA. Inhibition of EphB4 activation using decoy soluble EphB4 receptor fused in frame at the C-terminus with human albumin (sEphB4-HSA) was evaluated for in vivo studies of human tumor xenografts.

Results: EphB4 was expressed in all human tumor tissues, and the levels correlated directly with stage. High EphB4 also predicted shortened survival. EphB4 protein levels varied in tumor cell lines, and loss of cell viability with EphB4 shRNA knock down was highest in cell lines with highest EphB4 levels (range 25-78%). Tumor xenografts in sEphB4-HSA treated mice were reduced over 80% compared to the control PBS treatment. Tissue analysis revealed reduction in tumor vessel density, reduced recruitment of pericytes, and decreased perfusion of the tumor vessels. sEphB4-HSA treatment also decreased tumor tissue PI3K activity manifested by reduced phosphorylated AKT and S6 level. Tumor cell death by apoptosis was widespread consistent with combined anti-angiogenic activity and direct tumor cell toxicity.

Conclusion: EphB4 receptor tyrosine kinase is highly expressed in head/neck squamous cell cancer. EphB4 provides survival signal to the tumor cells directly. Decoy EphB4 inhibitor sEphB4-HSA is highly potent in in vivo tumor xenograft models. sEphB4-HSA is thus a candidate for investigation in human trials and the clinical trials are underway.

Citation Format: Ren Liu, Hai-yun Yen, Rizwan Masood, Uttam Sinha, Anthony El-Khoueiry, Stephen Liu, Barbara Gitlitz, Parkash S. Gill. EphB4 as a novel therapeutic target for head-neck SCC. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4356. doi:10.1158/1538-7445.AM2013-4356

Targeting the EphB4 receptor for cancer diagnosis and therapy monitoring

Accumulating evidence suggests that EphB4 plays key roles in cancer progression in numerous cancer types. In fact, therapies focusing on EphB4 have become potentially important components of various cancer treatment strategies. However, tumor sensitivity to EphB4 suppression may not be uniform for different cancers. In this study, we developed near-infrared fluorescence (NIRF) probes for EphB4 targeted imaging, based on EphB4-specific humanized monoclonal antibody hAb47. NIRF dye Cy5.5 was introduced to hAb47 either through the reaction with amino groups (named hAb47-Cy5.5) or sulfhydryl groups (named hAb47-Cy5.5-Mal). The resulting probes were evaluated in both HT-29 xenograft and the mAb131 (anti-EphB4) treated models. Although these methods lead to modifications of both the heavy chain and light chain of the antibody, the majority of the EphB4 binding affinity was maintained (81.62 ± 2.08% for hAb47-Cy5.5 and 77.14 ± 2.46% for hAb47-Cy5.5-Mal, respectively). hAb47-Cy5.5 was then chosen for in vivo NIRF imaging of EphB4 expression. In HT29 colorectal tumor xenografts, hAb47-Cy5.5 demonstrated significantly higher tumor uptake compared with that of the hIgG-Cy5.5 control, which was further confirmed by immunofluorescent staining. Moreover, hAb47-Cy5.5 successfully imaged the decreased EphB4 expression (confirmed by Western blot) in EphB4-targeted immunotherapy using another EphB4-specific antibody, mAb131. Collectively, hAb47-Cy5.5 could be used as a specific NIRF contrast agent for noninvasive imaging of EphB4 expression, which may predict whether an individual tumor would likely respond to EphB4 targeted interventions, as well as monitor the therapeutic response.

Monocyte-derived and CD34+/KDR+ endothelial progenitor cells in heart failure

BACKGROUND

Endothelial progenitor cells (EPCs) are known to be altered in heart failure (HF), but monocyte-derived EPCs in HF have not been assessed. We aimed to characterize monocyte-derived EPCs in systolic HF.

METHODS AND RESULTS

We recruited 128 subjects with systolic HF: 50 South Asian (SA), 50 white, and 28 African-Caribbean (AC), for interethnic comparisons. Additionally, SAs with HF were compared with 40 SAs with coronary artery disease (CAD) without HF (disease controls [DCs]) and 40 SA healthy controls (HCs). Counts of CD34(+) and kinase domain receptor (KDR)(+) monocytes attributed to specific monocyte subsets (CD14(++) /CD16(-) [Mon1], CD14(++)/CD16(+) [Mon2], and CD14(+)/CD16(++) [Mon3]) and monocyte expression of vascular endothelial growth factor (VEGF) receptor 1 were analyzed by flow cytometry. We also enumerated CD34(+)/KDR(+) EPCs derived from mononuclear cells ('classic' EPC definition).

RESULTS

SAs with HF had significantly reduced counts of CD34(+) monocytes, attributed to the Mon1 and Mon2 subsets. KDR(+) Mon1 counts were 4.5-fold increased in DCs as compared with HCs, but significantly reduced in HF subjects vs. DCs. VEGF receptor type 1 expression on Mon1 and Mon2 cells was significantly reduced in HF patients as compared with DCs. Also, CD34(+)/KDR(+) EPC numbers were reduced in HF subjects. Whites had significantly fewer KDR(+) Mon3 cells than ACs, but significantly more CD34(+) Mon2 cells than SAs and ACs. VEGF receptor type 1 expression by Mon1 cells was predictive for left ventricular ejection fraction after adjustment for ethnicity (β = - 0.25. P = 0.039). CD34(+) Mon2 counts correlated with measures of microvascular endothelial function, and were predictive of the future risk of hospital admission.

CONCLUSIONS

Circulating counts of monocyte-derived EPCs are significantly altered in HF, with significant ethnic differences in the levels of monocyte-derived EPCs.

Low-dosage inhibition of Dll4 signaling promotes wound healing by inducing functional neo-angiogenesis

Recent findings regarding Dll4 function in physiological and pathological conditions indicate that this Notch ligand may constitute an important therapeutic target. Dll4 appears to be a major anti-angiogenic agent, occupying a central role in various angiogenic pathways. The first trials of anti-Dll4 therapy in mice demonstrated a paradoxical effect, as it reduced tumor perfusion and growth despite leading to an increase in vascular density. This is seen as the result of insufficient maturation of the newly formed vasculature causing a circulatory defect and increased tumor hypoxia. As Dll4 function is known to be closely dependent on expression levels, we envisioned that the therapeutic anti-Dll4 dosage could be modulated to result in the increase of adequately functional blood vessels. This would be useful in conditions where vascular function is a limiting factor for recovery, like wound healing and tissue hypoxia, especially in diabetic patients. Our experimental results in mice confirmed this possibility, revealing that low dosage inhibition of Dll4/Notch signaling causes improved vascular function and accelerated wound healing.

Systolic heart failure in South Asians

Heart failure (HF) is a common condition leading to an unfavourable prognosis and impaired quality of life. In this review, we provide an overview of published literature on possible epidemiological and pathophysiological differences between patients with systolic HF of South Asian origin and those from other ethnic groups (mainly White). Systolic HF tends to manifest earlier among South Asians and with frequent hospital admissions. However, survival for such patients appears to be significantly better compared with the White group, which might be associated with different patterns of HF. For example, this could be attributed to a lower prevalence of left ventricular systolic dysfunction in South Asian subjects. Indeed, the high prevalence of hypertension and diabetes among South Asians may predispose to diastolic HF with preserved systolic function. In addition, because of underrepresentation of South Asians in clinical trials, there are little data on optimal management of this ethnic group.

Abstract LB-285: Blocking Dll4/Notch signaling inhibits development of chronic colitis-associated colorectal cancer in mice

Colorectal cancer (CRC) is one of the most frequent cancers worldwide, often developing as a complication of inflammatory bowel diseases. The Notch pathway plays a central role in intestinal homeostasia and its deregulation contributes to tumor development. Inhibition of Notch signaling through the Dll4 ligand shows anti-tumor activity against a variety of human and rodent tumors grafted in mice.

The aim of this work was to analyze Dll4 expression in both normal intestine and intestinal tumors, and determine the effect of Dll4 inhibition by using Dll4 heterozygous mice or administering a pharmacological inhibitor (soluble Dll4-Fc) in the mouse model of chemically induced colo-rectal cancer (CRC). To induce chronic colitis and CRC we combined the administration of azoxymethane, and repeated cycles of the proinflammatory dextran sodium sulfate in the drinking water, as previously described (Neufert et al. Nat Protoc 2: 1998) in either Dll4+/− mice or wild type mice treated with sDll4-Fc at a dose of 5mg/Kg/day, IP, 3x/wk from week 10 of AOM plus DSS treatment to week 14.

Dll4 expression was detected in the vascular endothelium as well as in both absorptive and secretive epithelium of the normal intestine and colorectal (CR) polyps. Both genetical (Dll4 allelic deletion, Dll4+/−) and pharmacological inhibition by the soluble extracellular domain of Dll4 (Dll4-Fc) led to significant reductions in the average number (12.5-fold in mutants, 3.7-fold in Dll4-Fc treated), average volume (1.6-fold in mutants, 2.3-fold in Dll4-Fc treated) and overall burden (15.2-fold in mutants, 6.3-fold in Dll4-Fc treated) of CR polyps, by inducing intratumoral apoptosis and disrupting proper tumor angiogenesis., leading to the formation of immature and non-functional blood vessels. Dll4 heterozygous mutants shown a 42.5% increase in tumor vascular density and a 13.9 % decrease in smooth muscle cell vascular recruitment, displaying increased vascular permeability and reduce vascular perfusion. Dll4-Fc treated mice displayed more proeminent vascular disruption, with a 127.5% increase in tumor vascular density and a 53.2% decrease in smooth muscle cell vascular recruitment, showing extensive vascular extravasation and poor perfusion of the tumor blood vessels.

In conclusion, Dll4Fc administration in chronic colitis-related CRC appears to constitute a promising therapeutical approach, capable of inhibiting the tumorigenic events as well as targeting the tumour vasculature and preventing tumor development.

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 LB-285. doi:10.1158/1538-7445.AM2011-LB-285