Exogenous growth factors bFGF, EGF and HGF do not influence viability and phenotype of (V600E)BRAF melanoma cells and their response to vemurafenib and trametinib in vitro

It has been shown that the response of (V600E)BRAF melanoma cells to targeted therapeutics is affected by growth factors. We have investigated the influence of three different growth factors, bFGF, EGF and HGF used either alone or in combination, on the response of (V600E)BRAF melanoma cell populations established from surgical specimens to vemurafenib and trametinib, targeting (V600E)BRAF and MEK1/2, respectively. We report that proliferation and phenotype of (V600E)BRAF melanoma cell populations were not detectably influenced by exogenous growth factors. Neither cell distribution in cell cycle and CCND1 expression nor activity of signaling pathways crucial for melanoma development and maintenance, including the RAF/MEK/ERK pathway, WNT/β-catenin pathway and NF-κB signaling, were affected by the presence of different growth factors. We furthermore show that vemurafenib and trametinib abrogated the activity of ERK1/2, arrested cells in G(0)/G(1) cell cycle phase, triggered apoptosis, induced changes in the expression of CXCL8, CCND1 and CTGF and the frequency of Ki-67(high) and CD271(high) cells. These effects were, however, similar in the presence of different growth factors. Interestingly, comparable results were also obtained for melanoma cells grown without exogenous growth factors bFGF, EGF and HGF for a period as long as 4 months prior the drug treatment. We conclude that the composition or lack of exogenous growth factors bFGF, EGF and HGF do not markedly influence viability and phenotype of (V600E)BRAF melanoma cells and their response to vemurafenib and trametinib in vitro. Our results question the necessity of these growth factors in the medium that is used for culturing (V600E)BRAF melanoma cells.