PIK3CA and colorectal carcinoma: Furthermore, it has been shown that PIK3CA mutations (E545K, E542K and E545D on exon 9; H1047R and H1047L on exon 20) could mediate resistance to standard chemotherapy (FOLFOX and FOLFORI) by inducing phosphorylation of PKB and expression CRC stem cell markers (LGR5) via sustained PI3K signalling, thereby promoting cancer cell survival and proliferation (Wang et al., 2018).