PD16, a steroidal saponin, induces apoptosis in colorectal cancer via inhibiting the AKT/GSK3β signaling pathway.

Colorectal cancer (CRC) is a common malignancy with high morbidity and mortality globally. PD16, a novel steroidal saponin from Paris delavayi Franchet, shows cytotoxicity against HepG2 and U87MG cells, but its anti-CRC effects and related molecular mechanisms remain unknown. Our study revealed that PD16 significantly suppressed the growth of HCT116 and HT-29 CRC cells, without noticeable toxic effects on the non-cancerous NCM460 cells. Moreover, PD16 treatment reduced colony formation ability, impaired migration and invasion, and caused arrest of cells predominantly in the G0/G1 phase. PD16 promoted apoptosis, evidenced by elevated expression levels of cleaved caspase-9, cleaved caspase-3, cleaved PARP, and Bax, along with decreased expression of Bcl-2. Mechanistically, PD16 exposure weakened the phosphorylation of AKT and GSK3β. Additionally, combination treatment with the AKT inhibitor MK-2206 enhanced PD16-induced apoptotic effects and further suppressed AKT/GSK3β signaling. Molecular docking demonstrated PD16 had a good binding effect with AKT and GSK3β. In xenograft mouse models, PD16 markedly inhibited CRC tumor growth with concomitant downregulation of the AKT/GSK3β pathway, without major organ toxicity. Collectively, these findings provide the first evidence that PD16 exerts pro-apoptotic effects in CRC cells through the AKT/GSK3β pathway inhibition, thereby confirming it as a valuable novel therapeutic candidate for CRC.