Fig. 1: pTyr397FAK expression is higher in triple negative cell lines and ALDH⁺ cells. FAK inhibition in combination with adjuvant therapies reduces CSC activity.

a Representative Western blot demonstrating baseline expression of pTyr397FAK, FAK, and GAPDH in breast cell lines including invasive carcinoma cell lines reflecting all molecular phenotypes. b Illustrative plot of relative density of pTyr397FAK to FAK, with relative density of pTyr397FAK to FAK measured and corrected for GAPDH. pTyr397FAK expression in normal ductal cell line MCF10a used as comparison. One-way ANOVA with post hoc Dunnett’s test (n = 2 for MCF10a and DCIS.com and n = 3 for IDC cell lines). c Representative Western blot demonstrating pTyr397FAK expression in ALDH⁺ and ALDH⁻ MDA-MB-231 cells with illustrative plot of relative densities shown in (d) (n = 3). e ALDH⁺ cells have increased primary MFE compared to ALDH⁻ expressing cells. Both D&E analysed using unpaired two tailed t-test. f FAK inhibition with VS4718 0.5 μM reduced primary MFE as a single agent therapy across all cell lines. This was evaluated alongside 1 μM of Tamoxifen in MCF7, 0.1 μM of Lapatinib in BT474 and SKBr3 cells and 0.1 μM Paclitaxel in MDA-MB-231 and SUM159 cells. Each experiment had a minimum of five biological repeats and six technical replicates. g FAK inhibition reduced mammosphere self-renewal in SKBr3 and SUM159 cells when used as monotherapy and in MDA-MB-231 cells when combined with Paclitaxel. All error bars are mean + SEM. Two-way ANOVA with post hoc Tukey’s test (ns not significant, *p < 0.05, **p < 0.01, ***p < 0.001, ***p < 0.0001).