Although targeted therapy strategies are currently lacking for patients whose melanomas are BRAF wild-type, some therapeutic efficacy was noted in a phase I clinical trial of the AKT inhibitor MK-2206 in combination with Carboplatin (C) and Paclitaxel (P). In the present study we addressed the mechanism underlying the responses to MK-2206 + CP in BRAF wild-type melanoma. As single agents, MK-2206, carboplatin and paclitaxel had only limited cytotoxic activity in both 2D and 3D cell culture and induced very little apoptosis. Prolonged treatment (>9 days) with the AKT inhibitor in combination with C+P led to significant levels of cell death in 4 3D spheroid culture models of BRAF-wild type melanoma. In contrast, treatment with single agent MK-2206 or C+P alone induced little cell death. To investigate the mechanism of interaction between these three compounds we focused upon autophagy induction. It was noted that significant levels of autophagy, as demonstrated by increased LC3-II staining, p62 expression and increased acridine orange staining, were induced following up to 6 days of treatment with the combination. In this context autophagy was protective, with levels of cell death induced by the combination significantly enhanced following treatment with the autophagy inhibitor chloroquine. The protective autophagy induced by MK-2206 + CP was only transient, with diminished levels of autophagy being observed by 9 days. The observed reduction in autophagic flux was associated with marked increases in cell death. In summary it appears that chronic insult with MK-2206 and CP pushes autophagy to its limit, relinquishing its protective role and enhancing sensitivity of the cells to therapy-induced apoptosis. These studies form the basis for a phase II trial evaluating MK-2206 in combination with chemotherapy, as well as autophagy inhibitors, in patients whose melanomas are BRAF-wild type.

Citation Format: Vito W. Rebecca, Renato R. Massaro, Silvya S. Maria-Engler, Jane L. Messina, Geoffrey T. Gibney, Vernon K. Sondak, Ragini Kudchadkar, Keiran S. Smalley. Exhaustion of autophagy-mediated cell survival underlies the pre-clinical and clinical activity of chemotherapy combined with the AKT inhibitor MK-2206 in BRAF wild-type melanoma. [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 1659. doi:10.1158/1538-7445.AM2013-1659