Collectively, these observations suggest that the inhibition of HER2 phosphorylation by AG825, resulting in cessation of the trans phosphorylation of HER3, and thus complete blockage of HER2 signalling through AKT, might be the predominant factor contributing to the reduction of BC T-ICs seen in SP and tumour repopulation assays. The gene discussed is ERBB2; the disease is breast cancer.