LAUSR

The incidence of melanoma is continuously growing worldwide, and an effective therapy for the metastatic disease still does not exist. Moreover, an intrinsic/extrinsic resistance to conventional chemotherapeutics, such as cisplatin (CPt), often arises in this tumor. The increased expression of a number of DNA repair genes, including the Excision Repair Cross-Complementation group 1 (ERCC1), has been related to the melanoma resistance to CPt. ERCC1 is a component of an important chemoresistance pathway [tyrosine-phosphatase dual-specificity phosphatase-6 (DUSP6)/extracellular signal-regulated kinase phosphorylation (p-ERK)/ERCC1]. New therapeutic strategies are under study, and one possibility is the administration of natural products combined with CPt therapy, in order to revert the CPt resistance. Many experimental in vitro and in vivo studies have contributed to support the antineoplastic properties of long-chain omega-3 polyunsaturated fatty acids (LC-omega-3 PUFA), especially docosahexaenoic acid (DHA), in tumor cells of different origin, including melanoma. In the present work the effects of CPt treatment combined with LC-omega-3 PUFA have been evaluated in highly metastatic murine (B16F10) and human (WM266-4) melanoma cell lines. Melanoma cells were exposed to increasing concentrations of CPt (1, 2.5 and 5 μM), alone or in combination with DHA (10 μM). Cell viability was analysed by the Trypan blue dye exclusion method 24, 48, and 72 h after treatment. The in vitro invasive ability of melanoma cells was assessed by the Wound Healing assay. The effects of increasing DHA concentrations combined or not with CPt on the expression of several proteins (ERCC1, pERK and DUSP6) related to CPt chemoresistance in melanoma cells were also analyzed by Western Bbotting. The data obtained demonstrated that the CPt/DHA combined treatment, performed by adding suboptimal concentrations of both the compounds, was significantly more efficient in inhibiting cell growth than the treatments with each of the two compounds administered alone. We confirmed that CPt was able to increase ERCC1 and decrease DUSP- 6 in a dose-dependent manner in both WM266-4 and B16F10 cell lines. Moreover, in the present work it was observed that DHA was able to revert the effects of CPt on ERCC1, DUSP6, and p-ERK expression. Similarly to what was observed with DHA, the LC-omega-3 PUFA eicosapentaenoic acid (EPA) exerted similar effects, even though at lower extent, on ERCC1, p-ERK, and DUSP6 expression in the same experimental conditions. Overall, the findings indicate that the combination of CPt with a dietary supplementation with LC-omega-3 PUFA could potentially represent a new, promising, complementary therapeutic strategy in order to overcome CPt resistance in melanoma. Moreover, the results suggest that the CPt/LC-omega-3 PUFA combination may allow the use of lower and suboptimal doses of CPt, thus probably reducing the undesirable side effects often accompanying the treatment with this antineoplastic drug. Citation Format: Renata O. Vasconcelos, Simona Serini, Ana Paula S. Votto, Gilma S. Trindade, Gabriella Calviello. Effect of long-chain omega-3 polyunsaturated fatty acids on cisplatin chemoresistance in murine and human melanoma cells [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; Sao Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A56.