In luciferase reporter assay examining the effect of BRAF V600E on TERT promoter activities in K1 cells harboring BRAF V600E (Fig. 2b), TERT promoter was far more active when harboring the C228T or C250T mutation than the wild-type; treatment with PLX4032 dramatically reduced the activities of the mutated TERT promoter and has limited effect on the wild-type TERT promoter. To further confirm the role of BRAF V600E in TERT expression, we stably knocked down BRAF in BCPAP, K1 and A375 cells, resulting in significantly reduced expression of TERT in all these cells (Fig. 2c, d). The somehow less pronounced decrease in TERT protein (Fig. 2c) than the decrease in TERT mRNA (Fig. 2d) in the BCPAP cell suggests that the protein translational synthesis system in this cell likely had a good efficiency at low levels of RNA. In contrast, BRAF V600E knock-in activated the MAKP pathway (Fig. 2e, f) and increased the activities of TERT promoter, especially the mutant types (Fig. 2g). These results again demonstrated a TERT promoter mutation-dependent activation of the TERT gene by the BRAF V600E/MAPK pathway.