binimetinib and Pancreatic-Neoplasms

Our increasing knowledge of the mechanisms behind the progression of pancreatic cancer (PC) has not yet translated into effective treatments. Many promising drugs have failed in the clinic, highlighting the need for better preclinical models to assess drug efficacy and characterize mechanisms of resistance. Using different experimental models, including patient-derived xenografts (PDXs), we gauged the efficacy of therapies aimed at two hallmark lesions of PCs: activation of signaling pathways by oncogenic KRAS and inactivation of tumor-suppressor genes. Although the drug targeting inactivation of tumor suppressors by DNA methylation had little effect, the inhibition of Mek, a K-Ras effector, in combination with the standard of care (chemotherapy consisting of gemcitabine/Nab-paclitaxel), reduced the growth of three out of five PC-PDXs and impaired metastasis. The two least responding PC-PDXs were composed of genetically diverse cells, which displayed sensitivities to the Mek inhibitor differing by >10-fold. Unexpectedly, our analysis of this genetic diversity unveiled different KRAS mutations. As mutation in KRAS occurs early during progression, this heterogeneity may reflect the simultaneous appearance of different malignant cellular clones or, alternatively, that cells containing two mutations of KRAS are selected during tumor evolution. In vitro and in vivo analyses indicated that the intratumoral heterogeneity, along with the selective pressure imposed by the Mek inhibitor, resulted in rapid selection of resistant cells. Together with the gemcitabine/Nab-paclitaxel backbone, Mek inhibition could be effective in treatment of PC. However, resistance because of intratumoral heterogeneity is likely to develop frequently, pointing to the necessity of identifying the factors and mechanisms of resistance to further develop this therapy.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; Cell Line, Tumor; Cell Proliferation; Deoxycytidine; DNA Methylation; DNA, Neoplasm; Drug Resistance, Neoplasm; Female; Gemcitabine; Genetic Heterogeneity; Humans; Mice, Inbred BALB C; Mice, Inbred NOD; Mice, SCID; Mitogen-Activated Protein Kinase Kinases; Mutation; Paclitaxel; Pancreatic Neoplasms; Protein Kinase Inhibitors; Proto-Oncogene Proteins p21(ras); Xenograft Model Antitumor Assays

To study the molecular mechanism regulating sensitivity to MEK inhibition in pancreatic cancer cell lines.. A growth inhibition assay determined sensitivity to MEK162 in a panel of 29 pancreatic cancer cell lines. For the same panel, KRAS mutational status and copy-number variation (CNV) was determine using PCR, array CGH and FISH. Two sensitive and two resistant cell lines were further interrogated for difference in baseline and MEK162-induced gene expression, as well as signal transduction using microarray and western blotting. Cell cycle and apoptosis analysis was measured by flow cytometry.. We report a strong correlation between both specific KRAS mutational subtype and CNV, and sensitivity to MEK inhibition. Cell lines with a KRAS (V12) mutation and KRAS gains or loss (n=7) are ∼10 times more resistant than those having neither a KRAS (V12) mutation nor KRAS CNV (n=14). Significant differences in baseline and MEK162-induced gene expression exist between the sensitive and resistant lines, especially in genes involved in RAS, EGF receptor and PI3K pathways. This was further supported by difference in signal transduction. MEK 162 blocked ERK1/2, as well as inhibited PI3K and S6 and increased p27KIP1 levels in the sensitive lines.. Given the potency of MEK162, it may be a promising new therapy for patients with pancreatic cancer and KRAS mutational subtypes, and CNV may serve as important biomarkers for selecting patients that benefit from MEK-targeting based on these preclinical data.

Topics: Apoptosis; Benzimidazoles; Blotting, Western; Cell Cycle; Cell Proliferation; DNA Copy Number Variations; Humans; In Situ Hybridization, Fluorescence; In Vitro Techniques; MAP Kinase Kinase 1; Mutation; Pancreatic Neoplasms; Proto-Oncogene Proteins; Proto-Oncogene Proteins p21(ras); ras Proteins; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Tumor Cells, Cultured