Targeting the PI3K signaling pathway in KRAS mutant colon cancer.

Metastatic colorectal cancer (CRC) patients with v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations are resistant to monoclonal antibody that targets the epidermal growth factor receptor such as cetuximab. BKM120 targets phosphatidylinositide-3-kinase (PIK3CA), but it is unknown whether BKM120 can reverse cetuximab resistance in KRAS mutant CRC. Human CRC cell lines with KRAS mutations (DLD-1, HCT116, and LoVo) were used to test the effect of cetuximab, BKM120, and cetuximab plus BKM120 on cell proliferation in vitro and in vivo. BKM120 reduced cell proliferation in a concentration-dependent manner in the LoVo (PI3KCA wild type) as well as the HCT116 and DLD1 cells (that carry a PI3KCA mutation). BKM120 only inhibited ERK phosphorylation in LoVo cells (PIK3CA wild type), but not in DLD1 or HCT116 cells at a concentration of 1 μmol/L. Treatment with cetuximab and BKM120 significantly reduced the growth of xenograft tumors originating from KRAS mutant cells compared with cetuximab alone (P = 0.034). BKM120 may overcome cetuximab resistance in colon cancer cells with KRAS mutation.