Fig. 2: SRC kinase inhibition sensitizes BRAFV600E CRC cell lines to vemurafenib.
a, Cell viability assays evaluating WiDr cells treated with vemurafenib plus a panel of kinase inhibitors selected on the basis of the results in Fig. 1b. The size of each bubble indicates the magnitude of the change in kinase activity induced by vemurafenib treatment (Fig. 1b), with color signifying increased (yellow) or decreased (blue) activity; (y axis, log2 scale). rs is the Spearman’s rho correlation, and the P value is from a two-tailed t test. Drug combinations were tested in n = 89 independent experiments. b, Shift in vemurafenib sensitivity, measured by cell viability assay (left) and calculation of the CI (right), upon treatment of BRAFV600E CRC or melanoma (MEL) cell lines with vemurafenib together with a SRC inhibitor (dasatinib (DAS), saracatinib (SAR) or bosutinib (BOS)) or an EGFR inhibitor (gefitinib) for 3 d. CI scores are averaged from individual experimental CIs calculated at 1×GI50, 2×GI50 and 0.5×GI50 concentrations of each drug (n ≥ 3 independent experiments). c, Colony formation assays in which BRAFV600E CRC or melanoma (Mel888) cells were treated with an increasing concentration of vemurafenib alone (control, CON) or with a fixed dose of dasatinib. Data are representative of n = 2 independent repeats. d, Western blots showing knockdown of SRC in BRAFV600E CRC cell lines stably transfected with a control shRNA (shCON) or two different SRC-targeting shRNAs (shSRC). HSP90 serves as a loading control. Molecular weight/size markers are indicated on the right (kDa). The experiment was repeated three independent times with similar results. e, Bar graphs representing the fold change (log2 scale) ± standard error for change in sensitivity to vemurafenib with knockdown of SRC in 3-day cell viability assays. Top, CI, Bliss model score; colors as in b (n = 3 independent experiments per cell line). f, Colony formation in BRAFV600E CRC cells treated with an increasing concentration of vemurafenib with or without SRC knockdown. Data are representative of n = 2 independent repeats.
