Abstract A134: Eeyarestatin I sensitizes melanoma cells to cisplatin-induced cell death

Abstract

Abstract Melanoma is the most deadly form of skin cancer with a high metastatic potential. Initial stages of the disease can be surgically treated, but the treatment options for advanced stages are very limited. Although progress has been made with the development of some target- and immune-therapy, improving melanoma patients' outcomes, the cost of these therapies is reaching prohibiting values. Not all melanoma patients, mainly those treated in public health systems, have access to these new therapies. Indeed, they are treated with conventional chemotherapy, such as dacarbazine or cisplatin, which promotes very low therapeutic responses. In light of this, we sought to investigate in the present work an alternative to improve the response of conventional chemotherapy to treat melanomas. A previous proteomic study from our group revealed that human melanoma cells treated with cisplatin accumulated the endoplasmic reticulum (ER) chaperone GRP78, an important sensor of ER stress and regulator of unfolded protein response (UPR). UPR signaling is activated in response to ER stress, inducing survival pathways to restore ER homeostasis or activating cell death pathways under severe or persistent ER stress conditions. Adaptation and selection of melanoma cells to ER stress can be one of the drivers of chemoresistance in melanoma. To investigate ER stress adaptation, we assessed in the current work the transcription factor CHOP, which mediates UPR-induced apoptosis. Using a TMA (tissue microarray) platform, we observed the nuclear exclusion of CHOP in primary and metastatic human melanomas when compared to nevus tissues. In the face of these results, we hypothesized that by inducing more ER stress we could surpass the adaptive levels of ER stress, favoring nuclear CHOP accumulation, culminating in the sensitization of melanoma cells to cisplatin. To induce ER stress, we tested an ERAD (ER-associated degradation) inhibitor that blocks the exit of unfolded proteins from ER to degradation in the cytosol, eeyarestatin I (EerI). We observed that treatment of the human melanoma cells CHL-01 with EerI favored the accumulation of GRP78 in the cytosol and CHOP in the nucleus. Notably, the combination of EerI and cisplatin resulted in a significant increase in cell death as compared to single treatments. Our results suggest that approaches to surpass adaptive levels to ER stress, such as EerI treatment, are a promising strategy to chemosensitize melanoma cells. Supported by FAPESP (1998/14247-6); (Redoxoma, CNPq 573530/2008-4) and FAPESP (2010/08284-0). Citation Format: Renata de Freitas Saito, Andréia Hanada Otake, Margarita M. Cortez, Robbert J. Gillies, Roger Chammas. Eeyarestatin I sensitizes melanoma cells to cisplatin-induced cell death [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A134.