Figure 5. HSP90 inhibition increased BIM, decreases Mcl-1 and restores apoptosis in vemurafenib-resistant melanoma cell lines.
A: (Left) Western blot showing that XL888 (48 hrs, 300nM) decreases BIM phosphorylation (Ser69) and increases BIM expression. (Right) Quantitative RT-PCR experiment showing that treatment with XL888 (300 nM, 48 hrs) increases the expression of BIM at the mRNA level. B: siRNA knockdown of BIM significantly decreases XL888 (300 nM, 48hrs) mediated apoptosis in two vemurafenib resistant melanoma cell lines (M229R and 1205LuR). C: (Left) Western blot of Mcl-1 expression in vemurafenib resistant melanoma cell lines treated with XL888 (300 nM) for 48 hrs. (Right) Quantitative RT-PCR showing that XL888 (300 nM, 48hrs) treatment downregulates Mcl-1 expression at the mRNA level. D: Induction of Mcl-1 reduces the magnitude of XL888 induced apoptosis. Western blot shows the induction of Mcl-1 following doxycycline treatment. Induction of Mcl-1 (DOX+XL) significantly reduces the level of XL888-induced apoptosis compared to XL888 (XL: 300nM, 72 hrs) alone. *P<0.05