KRT8 and breast cancer: Pik3caH1047R overexpression was also used to determine lineage effects in mammary tumours by specifically targeting the mutation to either basal (LGR5 positive) or luminal (keratin 8 positive) lineage restricted cells (using Lgr5-CreERT2 and K8-CreERT2, respectively) resulting in heterogeneous, multi-lineage mammary tumours.