To evaluate if the reduction in growth and proliferation during FAK inhibitor treatment corresponded with a decreased CSC activity, we isolated tumour cells from treated PDX tumours and measured ex vivo mammosphere forming ability (representative photomicrographs Fig. 6c–e), ALDH+ CSC population (Supplementary Fig. 1a–f) and tumour initiating capacity. This evidence concerns the gene PTK2 and neoplasm.