Figure 6. HSP90 inhibition is more effective at restoring the apoptotic response than combined MEK+PI3K inhibition.

A: Immunofluorescence staining of 1205LuR and M229R cells for BIM and FOXO3a following treatment with either vehicle, XL888 (300nM), AZD6244 (3µM), GDC-0941 (3µM) and the combination of AZD6244 + GDC-0941 (each at 3µM). B: XL888 is more effective than MEK+PI3K inhibitors at increasing BIM and decreasing Mcl-1 mRNA expression in 1205LuR and M229R cell lines. Cells were treated with vehicle, XL888, AZD6244, GDC-0941 and the combination of AZD6244 + GDC-0941 (as above) and Quantitative RT-PCR was performed on BIM and Mcl-1. C: XL888 is more effective than MEK+PI3K inhibitors at increasing BIM and decreasing Mcl-1 protein expression in 1205LuR and M229R cell lines. Cells were treated with vehicle, XL888, AZD6244, GDC-0941 and the combination of AZD6244 + GDC-0941 as above and Western blotting was performed for BIM and Mcl-1. D: XL888 is more effective at inducing apoptosis of melanoma cell lines where resistance is mediated through COT and PDGFRβ expression and in 2 models where the resistance mechanism is unknown. Cells were treated with XL888, AZD6244, GDC-0941 and AZD6244 + GDC-0941 as described above for 72 or 144 hrs. Apoptosis was measured by Annexin-V staining and flow cytometry.