Development of Acquired Resistance in Alpelisib-treated Gastric Cancer Cells With PIK3CA Mutations and Overcoming Strategies.

Background/aim: Alpelisib has shown promise in preclinical studies for treating PIK3CA-mutant gastric cancer (GC), and its combination with chemotherapy has progressed to clinical trials. However, acquired resistance to alpelisib remains a significant challenge. This study aimed to elucidate the mechanisms underlying acquired alpelisib resistance and propose potential therapeutic strategies to overcome it.

Materials and methods: Acquired alpelisib-resistant GC cell lines were developed by prolonged drug exposure. Mechanistic studies included whole-exome sequencing, western blotting, immunoprecipitation, Cdc42 and Rac1 activity assays, caspase-3/7 assays, colony formation assays, and sphere formation assays to investigate resistance pathways and therapeutic interventions.

Results: Two GC cell lines with acquired resistance to alpelisib, SNU601-R and AGS-R, were successfully developed from SNU601 and AGS. Both acquired alpelisib-resistant cell lines exhibited PTEN functional loss, leading to activation of SRC, STAT1, AKT, and PRAS40 signaling pathways. Combination treatments with pan-PI3K inhibitors or AKT inhibitors successfully overcame resistance. Among these, the combination of capivasertib, an AKT inhibitor, with SN38 demonstrated superior cytotoxic effects. Furthermore, the combination of capivasertib and SN38 significantly reduced the colony forming ability and sphere formation compared to each treatment alone in SNU601-R and AGS-R cells.

Conclusion: In alpelisib-treated GC cells with PIK3CA mutations, PTEN functional loss and changes in the associated signaling pathway were identified as important mechanisms of acquired alpelisib resistance. The combination of capivasertib and SN38 effectively overcomes acquired resistance to alpelisib in PIK3CA-mutant GC, providing a preclinical rationale for future clinical trials targeting acquired alpelisib-resistant GC with PIK3CA mutations.