Abstract B21: Endoplasmic reticulum stress conditioned melanoma cell lines to chemotherapy-induced cell death.

Abstract

Abstract Melanoma is among the most aggressive malignancies with increasing worldwide incidence and there is no effective treatment for the metastatic disease. The absence of an effective therapy may be due to adaptation and selection of melanoma cells to endoplasmic reticulum (ER) stress (Hersey P and Zhang XD). We showed that GADD153, one of the components of the ER stress-mediated apoptosis pathway, was mostly excluded from the nucleus of primary and metastatic melanoma cells compared with nevus cells. These data suggest that the unexpected GADD153 cellular localization could be involved in melanoma cell adaption to ER stress, since GADD153 accumulates in the nucleus during ER stress. Unfolded protein response (UPR) signaling induced in response to ER stress is a dual process that acts inducing a protective response to restore ER homeostasis or cell death in a severe or persistent ER stress induction. We investigated if induction of ER stress was a potential strategy to chemosensitize melanoma cells to genotoxic drugs by surpassing the adaptive levels to ER stress. We first treated human melanoma cells (SBCl2, Skmel28 and Mel85) with tunicamycin (TUN), an ER stress inducer before cis-diamminedichloroplatinum(II)(CDDP) treatment. CDDP is a low cost chemotherapeutic drug currently used in Brazil as a second line for melanoma treatment, especially in youngsters. We demonstrated an >50% increase in the percentage of cells in cell death process with TUN/CDDP treatment when compared to CDDP only. UPR markers, GRP78 and GADD153, were induced by TUN. One of the cellular mechanisms that are regulated by ER stress is autophagy. Accordingly, we observed an increase in the acidic vesicular organelles, assessed by acridine orange staining, in response to combined treatment. Autophagy inhibition with 3-Methyladenine increased TUN/CDDP induced-cell death, suggesting that autophagy plays a protective role in this response. Reactive oxygen species were involved in TUN and CDDP response, but more prominently in combined treatment response. However, the oxidative stress inhibition with N-acetylcysteine did not alter the sensitization effect of TUN pretreatment. We also tested temozolomide (TMZ), an equivalent drug to the active form of dacarbazine, the first line treatment of melanoma. The same sensitization capacity was observed in cells pretreated with TUN and further treated with TMZ. These results indicate that tumor cells could be preconditioned to cell death if exposed to a first ER stressor, such as TUN, which would compromise an effective adaptive response to a cell death inducer, as CDDP and TMZ. This combined approach may be a promising strategy for melanoma therapy. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B21. Citation Format: Renata F. Saito, Andréia H. Otake, Margarita M. Cortes, Roger Chammas. Endoplasmic reticulum stress conditioned melanoma cell lines to chemotherapy-induced cell death. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B21.