Purpose The notch pathway is overexpressed in pancreatic adenocarcinoma. RO4929097, an oral inhibitor of the γ-secretase enzyme has been safely given as a single agent in patients with advanced solid tumors. We aimed to evaluate the efficacy of RO4929097 in patients with pancreatic adenocarcinoma (PDA). Methods A two-stage, single-arm Phase II trial was conducted in patients with previously treated metastatic PDA. RO4929097 was administered at a dose of 20 mg daily on days 1-3, 8-10 and 15-17 of 21-day cycles. The primary endpoint was survival at 6 months. Secondary endpoints included overall survival (OS), response rate, toxicities, pharmacokinetic and pharmacodynamic analyses. Results Eighteen patients were recruited, 17 in the first stage and one in the 2nd stage. It was decided to stop further enrollment after RO4929097 was discontinued by the sponsor and was no longer a development candidate. Three (25%) of 12 evaluable patients achieved stable disease. The six-month survival rate was 27.8% (95 % CI 9.7–53.5). The median OS was 4.1 months (95 % CI 2.7–5.8 months) and median progression-free survival was 1.5 months (95 % CI 1.3–1.6 months). Pharmacokinetic properties of RO4929097 in patients (n=5) with PDA was similar to that previously reported in other patient populations. There was a trend towards a decrease in HeyL (p = 0.08) gene expression in three patients following study drug administration. Conclusions RO4929097 was well-tolerated in patients with previously treated PDA. Development of RO4929097 has been discontinued, but development of other notch-targeting agents in pancreatic cancer is continuing.

Anti-angiogenic therapy is commonly used for the treatment of CRC. Although patients derive some clinical benefit, treatment resistance inevitably occurs. The MET signaling pathway has been proposed to be a major contributor of resistance to anti-angiogenic therapy. MET is upregulated in response to VEGF pathway inhibition and plays an essential role in tumorigenesis and progression of tumors. In this study we set out to determine the efficacy of cabozantinib in a preclinical CRC PDTX model. We demonstrate potent inhibitory effects on tumor growth in 80% of tumors treated. The greatest antitumor effects were observed in tumors that possess a mutation in the PIK3CA gene. The underlying antitumor mechanisms of cabozantinib consisted of inhibition of angiogenesis and Akt activation and significantly decreased expression of genes involved in the PI3K pathway. These findings support further evaluation of cabozantinib in patients with CRC. PIK3CA mutation as a predictive biomarker of sensitivity is intriguing and warrants further elucidation. A clinical trial of cabozantinib in refractory metastatic CRC is being activated.

Background:Dysregulation of the Notch pathway has been identified to play an important role in the development and progression of colorectal cancer (CRC). In this study, we used a patient-derived CRC explant model to investigate the efficacy of the clinical γ-secretase inhibitor (GSI) PF-03084014.Methods:A total of 16 CRC explants were treated with PF-03084014. Knockdown of RBPjκ gene was used to determine the specificity of PF-03084014. Evaluation of the Notch and Wnt pathways in CRC explant tumours was performed by gene array and immunoblotting.Results:We identified a subset of CRC tumours that exhibited elevations of the Notch and Wnt pathways sensitive to PF-03084014. Treatment with the GSI resulted in a significant reduction in cleaved Notch, Axin2 (Wnt-dependent gene) and active β-catenin. In addition, knockdown of the RBPjκ gene showed that PF-03084014 has specificity for the Notch pathway in an HCT116 cell line xenograft model. Finally, an increase in apoptosis was observed in CRC001- and CRC021-sensitive tumours.Conclusion:This study provides evidence that inhibition of γ-secretase may be beneficial in a subset of patients with elevated levels of the Wnt and Notch pathways.

Dysregulation of the Notch1 receptor has been shown to facilitate the development and progression of colorectal cancer (CRC) and has been identified as an independent predictor of disease progression and worse survival. Although mutations in the NOTCH1 receptor have not been described in CRC, we have previously discovered a NOTCH1 gene copy number gain in a portion of CRC tumor samples. Here, we demonstrated that a NOTCH1 gene copy number gain is significantly associated with worse survival and a high percentage of gene duplication in a cohort of patients with advanced CRC. In our CRC patient-derived tumor xenograft (PDTX) model, tumors harboring a NOTCH1 gain exhibited significant elevation of the Notch1 receptor, JAG1 ligand and cleaved Notch1 activity. In addition, a significant association was identified between a gain in NOTCH1 gene copy number and sensitivity to a Notch1-targeting antibody. These findings suggest that patients with metastatic CRC that harbor a gain in NOTCH1 gene copy number have worse survival and that targeting this patient population with a Notch1 antibody may yield improved outcomes.

The Notch signaling pathway has been shown to be upregulated in colorectal cancer (CRC) and important for the self-renewal of cancer stem cells. In this study, we evaluated the efficacy of PF-03084014, a γ-secretase inhibitor, in combination with irinotecan to identify the effects of treatment on tumor recurrence and the tumor-initiating population in our CRC preclinical explant model. The combination of PF-03084014 and irinotecan had the greatest effect at reducing tumor growth on four CRC tumors when compared with treatment with PF-03084014 or irinotecan alone. The combination significantly reduced tumor recurrence in two CRC explants (CRC001 and CRC036) after treatment was discontinued. Both of these tumors exhibited elevated baseline levels of Notch pathway activation as well as an increase in NOTCH1 gene copy number when compared with the two CRC explants (CRC026 and CRC027) where tumors reappeared quickly after termination of treatment. Isolation and injection of aldehyde dehydrogenase (ALDH+ and ALDH−) cells in an in vivo explant model demonstrated that the ALDH+ cell population were tumorigenic. Evaluation of the ALDH+ cells after 28 days of treatment showed that the combination reduced the ALDH+ population in the tumors that did not regrow. Furthermore, ALDH+ cells from CRC001 and CRC027 were injected in vivo and treated immediately for 28 days. Two months after treatment, tumors were evident in the combination treatment group for CRC027 but not for CRC036. These results indicate the combination of PF-03084014 and irinotecan may be effective in reducing tumor recurrence in CRC patients whose tumors exhibit elevated levels of the Notch pathway.

Irinotecan, a standard of care therapy for CRC, elicits cytotoxic effects by generating double strand breaks resulting in DNA damage. The activation of the ATM pathway plays a fundamental role in regulating the cellular response and repair to DNA damage. The objective of this preclinical study was to determine whether ATM inhibition would enhance sensitivity to irinotecan treatment. Treatment effects of AZ31, irinotecan or AZ31 + irinotecan were investigated in CRC cell lines and CRC patient derived xenografts. Activation of ATM and downstream targets p-RAD50 and p-H2AX were evaluated by immunohistochemistry. Combinational effects were demonstrated in 4 out of 8 CRC explants. Interestingly, each of the combinational sensitive CRC PDX models were shown to be more resistant to irinotecan single agent therapy. Treatment with irinotecan significantly elevated the ATM pathway evident by an increase in the activation of H2AX and RAD50. Combinational therapy reduced the activation of H2AX and RAD50 when compared to irinotecan alone in the combination sensitive CRC098. AZ31 + irinotecan was effective at reducing tumor growth in tumors that exhibited resistance to irinotecan in our CRC PDX model. These findings support further investigation of this combinational therapy for the treatment of CRC patients.

Purpose Dysregulation of the phosphoinositide 3-kinase (PI3K) and Src signaling pathways commonly occur in colorectal cancer. Mutations in the PIK3CA gene are associated with an increase in severity of disease and worse clinical outcomes. Elevated levels of Src have been identified in premalignant lesions and are suggested to play a central role in tumor progression. Because these pathways appear to enhance tumor growth and metastasis, molecularly targeted agents for both pathways are currently being evaluated in early-phase clinical trials. Experimental Design We used colorectal cancer cell lines and a patient-derived explant model to investigate the efficacy of saracatinib. Mutations in the PIK3CA were evaluated to examine the association between mutations in the PIK3CA gene and sensitivity to saracatinib. Results We have identified a subset of patients with a PIK3CA (exon 9 and 20) mutation with increased sensitivity to saracatinib. A novel 3′ untranslated region (UTR) mutation was also shown to be associated with increased sensitivity to saracatinib and have a reduced affinity for miR-520a and miR-525a. Importantly, we show that Src inhibition reduces the interaction between Src and p85, subsequently decreasing Akt-dependent signaling. Conclusion These results indicate that a personalized approach in targeting Src in PIK3CA-mutant patients with colorectal cancers may prove effective in a subset of patients with this genetic alteration.

Antiangiogenic therapy used in treatment of metastatic colorectal cancer (mCRC) inevitably succumbs to treatment resistance. Upregulation of MET may play an essential role to acquired anti-VEGF resistance. We previously reported that cabozantinib (XL184), an inhibitor of receptor tyrosine kinases (RTK) including MET, AXL, and VEGFR2, had potent antitumor effects in mCRC patient-derived tumor explant models. In this study, we examined the mechanisms of cabozantinib sensitivity, using regorafenib as a control. The tumor growth inhibition index (TGII) was used to compare treatment effects of cabozantinib 30 mg/kg daily versus regorafenib 10 mg/kg daily for a maximum of 28 days in 10 PDX mouse models. angiogenesis and glucose uptake were assessed using dynamic contrast-enhanced (DCE)-MRI and [F]-FDG-PET imaging, respectively. RNA-Seq, RTK assay, and immunoblotting analysis were used to evaluate gene pathway regulation and Analysis of TGII demonstrated significant antitumor effects with cabozantinib compared with regorafenib (average TGII 3.202 vs. 48.48, respectively; = 0.007). Cabozantinib significantly reduced vascularity and glucose uptake compared with baseline. Gene pathway analysis showed that cabozantinib significantly decreased protein activity involved in glycolysis and upregulated proteins involved in autophagy compared with control, whereas regorafenib did not. The combination of two separate antiautophagy agents, SBI-0206965 and chloroquine, plus cabozantinib increased apoptosis Cabozantinib demonstrated significant antitumor activity, reduction in tumor vascularity, increased autophagy, and altered cell metabolism compared with regorafenib. Our findings support further evaluation of cabozantinib and combinational approaches targeting autophagy in colorectal cancer. .