BRAF and melanoma: Since pS6 expression can predict responsiveness to BRAF and MEK inhibitors in BRAF-mutant melanoma cells (25, 26), we also investigated pS6 expression after 1 or 24 h treatment with selumetinib, ZSTK474 and BEZ235 alone and in combination with three cell lines that were highly sensitive to selumetinib and vemurafenib (NZM3, NZM11, and NZM20) and three cell lines that were less sensitive (NZM6, NZM7, and NZM12).