Figure 8

Ganetespib potentiates the anti-cancer effects of lapatinib in ErbB2⁺ breast cancer cells. (a) BT474 and SKBR3 cells were treated with ganetespib (0 or 5 nM) and lapatinib (0, 15.6, 31.25, 62.5, 125, 250, or 500 nM) for 5 days, followed by an MTT assay to assess cell viability. (b) BT474 and SKBR3 cells were treated with ganetespib alone (25 or 50 nM), lapatinib alone (100 or 125 nM), or ganetespib + lapatinib for 24 hours. Then, cells were Annexin V/PI-stained and analyzed with flow cytometry. The percentages of cells in early (Annexin V⁺/PI⁻) and late (Annexin V⁺/PI⁺) stages of apoptosis are graphed in the panels to the right of the representative dot plots. (c) BT474 cells were treated with ganetespib (50 nM) +/− lapatinib (250 nM) for 16 hours, and SKBR3 cells were treated ganetespib (50 nM) +/− lapatinib (500 nM) for 16 hours. Then, Western blot analysis was performed to detect the expression and activation/phosphorylation of the indicated markers. Cropped Western blot images are shown at the target molecular weights for the indicated markers. (d) BT474 and SKBR3 cells were treated with a series of increasing doses of ganetespib and lapatinib for 5 days. Then the viable fraction of each cell line (fraction affected; FA) was determined with an MTT assay. The Combination Index (CI) was calculated using CompuSyn software and graphed for each cell line. Dose combinations with a CI < 1.0 are highlighted in red. All values are presented as the means ± S.E. (*P ≤ 0.05; **P ≤ 0.01 as compared to the corresponding untreated controls).