Abstract

&NA; Colorectal cancer (CRC) is one of the leading causes of cancer‐related morbidity and mortality worldwide. Accumulating evidence suggests that mitochondrial dynamics are closely implicated in carcinogenesis including CRC. Paris Saponin II (PSII), a major steroidal saponin extracted from Rhizoma Paris polyphylla, has emerged as a potential anticancer agent. However, the effects of PSII on CRC and its underlying mechanisms remain unknown. In the present study, we found PSII induced apoptosis and inhibited colony formation in HT 29 and HCT 116 cells, and cell cycle arrest in G1 phase. PSII inhibited the phosphorylation of ERK1/2 and mitochondrial translocation of dynamin‐related protein 1 (Drp1) by dephosphorylating Drp1 at Ser616, leading to the suppression of mitochondrial fission. PSII also suppressed NF‐&kgr;B activation as a result of the inhibition of IKK&bgr; and p65 translocation. Drp1 knockdown remarkably downregulated the nuclear expression of p65 and its target genes cyclin D1 and c‐Myc in HCT 116 cell, confirming the link between mitochondrial fission and NF‐&kgr;B pathway. Silencing of Drp 1 enhanced the inhibitory effects of PSII on p65 phosphorylation and the expressions of cyclin D1 and c‐Myc, revealing that the inhibitory effects of PSII on cyclin D1 and c‐Myc were relevant in the suppression of Drp1 and NF‐&kgr;B activation. An in vivo study demonstrated PSII remarkably decreased the xenograft tumor size and suppressed the phosphorylation of ERK1/2 and Drp1 at Ser616. Taken together, our results suggested that PSII could inhibit colorectal carcinogenesis, at least in part, by regulating mitochondrial fission and NF‐&kgr;B pathway.