Using the mammosphere assay, which measures changes in CSC activity in vitro, we investigated the effect of FAK inhibition (VS4718) alone and in combination with standard adjuvant therapies across a panel of breast cancer cell lines; MCF7 (ER+/PR+/HER2−) VS4718 0.5 μM ± Tamoxifen 1 μm; BT474 (ER+/PR+/HER2+) and SKBr3 (ER−/PR−/HER2+) VS4718 0.5 μM ± 0.1 μM Lapatinib; MDA-MB-231 and SUM159 (ER−/PR−/HER2−) VS4718 0.5 μM ± 0.1 μM Paclitaxel. Here, PTK2 is linked to breast cancer.