MAPK3 and melanoma: The protein levels of all four members of the fibroblast growth factor receptors superfamily, FGFR1-4, and their activation by phosphorylation at Tyr653/654, as well as downstream activation of ERK1/2 by phosphorylation at ERK1/2-Thr202/Tyr202, were investigated in A375 melanoma cells incubated for 24–72 h, with CPL304110 in the presence or absence of 1,25(OH)2D3.