azd-6244 and Carcinoma--Neuroendocrine

Clinical trials using kinase inhibitors have demonstrated transient partial responses and disease control in patients with progressive medullary thyroid cancer (MTC). The goal of this study was to identify potential combinatorial strategies to improve on these results using sorafenib, a multikinase inhibitor with activity in MTC, as a base compound to explore signaling that might predict synergystic interactions. Two human MTC cell lines, TT and MZ-CRC-1, which harbor endogenous C634W or M918T RET mutations, respectively, were exposed to sorafenib, everolimus, and AZD6244 alone and in combination. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrasodium bromide (MTT) and poly (ADP-ribose) polymerase (PARP) cleavage assays were performed to measure cell survival and apoptosis. Western blots were performed to confirm activity of the compounds and to determine possible mechanisms of resistance and predictors of synergy. As a solitary agent, sorafenib was the most active compound on MTT assay. Western blots confirmed that sorafenib, everolimus, and AZD6244 inhibited their anticipated targets. At concentrations below its IC(50), sorafenib-treated TT and MZ-CRC-1 cells demonstrated transient inhibition and then re-activation of Erk over 6 h. In concordance, synergistic effects were only identified using sorafenib in combination with the Mek inhibitor AZD6244 (P<0.001 for each cell line). Cells treated with everolimus demonstrated activation of Akt and Ret via TORC2 complex-dependent and TORC2 complex-independent mechanisms respectively. Everolimus was neither additive nor syngergistic in combination with sorafenib or AZD6244. In conclusion, sorafenib combined with a Mek inhibitor demonstrated synergy in MTC cells in vitro. Mechanisms of resistance to everolimus in MTC cells likely involved TORC2-dependent and TORC2-independent pathways.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Benzenesulfonates; Benzimidazoles; Carcinoma; Carcinoma, Neuroendocrine; Cell Line, Tumor; Cell Survival; Drug Synergism; Everolimus; Extracellular Signal-Regulated MAP Kinases; Humans; MAP Kinase Signaling System; Niacinamide; Phenylurea Compounds; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-ret; Pyridines; Sirolimus; Sorafenib; Thyroid Neoplasms; TOR Serine-Threonine Kinases

We hypothesized that autophagy inhibition would enhance the anticancer efficacy of ret protooncogene-targeted therapy in medullary thyroid cancer.. Medullary thyroid cancer-1.1 and TT cells were treated with sunitinib or sorafenib in the presence or absence of everolimus, trehalose, or small interfering RNA directed against autophagy protein 5.. Sunitinib and sorafenib each robustly induced light chain 3-II expression, indicating autophagy activation. Autophagy protein 5 silencing diminished the antiproliferative effects of sunitinib and sorafenib by 44% (P < .05) and 41% (P < .05), respectively, in medullary thyroid cancer-1.1 cells and by 43% (P < .01) and 39% (P < .05), respectively, in TT cells. In contrast, everolimus increased the antiproliferative effects of sunitinib and sorafenib by 24% (P < .01) and 27% (P < .01), respectively, in medullary thyroid cancer-1.1 cells and by 20% (P < .05) and 23% (P < .05), respectively, in TT cells. Trehalose increased the antiproliferative effects of sunitinib and sorafenib by 26% (P < .01) and 27% (P < .01), respectively, in medullary thyroid cancer-1.1 cells and by 28% (P < .05) and 29% (P < .05), respectively, in TT cells. Autophagy protein 5 silencing abrogated both everolimus- and trehalose-induced increases in tyrosine kinase inhibitor efficacy.. Loss (gain) of autophagy diminishes (improves) the efficacy of sunitinib and sorafenib. Our findings suggest that autophagic activation should be combined with targeted ret protooncogene therapy for patients with advanced medullary thyroid cancer.

Topics: Antineoplastic Agents; Autophagy; Benzenesulfonates; Benzimidazoles; Carcinoma, Neuroendocrine; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Drug Synergism; Everolimus; Humans; Immunosuppressive Agents; Indoles; Niacinamide; Phenylurea Compounds; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-ret; Pyridines; Pyrroles; Sirolimus; Sorafenib; Sunitinib; Thyroid Neoplasms