Aberrant Sodium Current Contributes To Constitutive Mtor Activity In Malignant Melanoma Cells

Transformation from disciplined melanocytes to untamed melanoma cells remains an enigma. Our previous studies have demonstrated that melanoma cells are more resistant to oxidative stress and melanoma cells exhibit constitutive mTOR activity. Surprisingly, further studies have failed to present the expression and activity of EGFR using conventional anti-EGFR antibodies. We hypothesized that constitutive mTOR activity in melanoma cells may be due to mutated EGFR variants and membrane channel activities. Using patch clamping technique, we have shown that melanoma cells (WM 266-4) but not human skin melanocytes exhibit Na+ current which is blocked by TTX. Interestingly, mTOR inhibitor, rapamycin, blocks Na+ current. Western blot and confocal microscopy data further revealed that Na+/Ca2+ exchanger blocker KB-R7943 (KBR), and L-type Ca2+ channel blocker Nifedipine (NIF) inhibits mTOR activity in melanoma cells in a dose dependent manner. To further characterize Na+ channels, we used commercially available channel antibodies. Western blot analysis data showed that melanoma cells but not human melanocytes express Na+ v1.5 and Na+ v1.6 and NCX3. Functional studies also indicated that KBR and NIF inhibit melanoma cell proliferation and migration. Taken all together, our data suggest that aberrant Na+ current contributes to constitutive mTOR activity in melanoma cells and channel blockers may be potential for the treatment of melanoma. Citation Format: Benjamin Gallant, Nicole Lizza, Ryan Garrity, Audrey Madigan, Zachary Jost, Alfredo Gonzalez, Jeanine Justiniano, An Xie, Yinsheng Wan. Aberrant sodium current contributes to constitutive mTOR activity in malignant melanoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 234A.