An acquired resistance to platinum-based drugs has emerged as a significant impediment to effective ovarian cancer therapy. The present study explored the anticancer mechanisms of triptolide (TPL) in SKOV3PT platinum-resistant human ovarian cancer cells and observed that TPL activated caspase 3 and induced the dose-dependent apoptosis of the SKOV3PT cells. Furthermore, TPL inhibited complex I of the mitochondrial respiratory chain (MRC) followed by an increase of reactive oxygen species (ROS), which further inhibited nuclear factor (NF)-κB activation and resulted in the downregulation of anti-apoptotic proteins, Bcl-2 and X-linked inhibitor of apoptosis protein (XIAP). Notably, the pre-treatment with N-acetyl-L-cysteine (NAC) abolished the TPL-induced ROS generation, NF-κB inhibition and cell apoptosis, but did not affect the inhibitory effect of TPL on complex I activity. These results suggested that TPL negatively regulated the NF-κB pathway through mitochondria-derived ROS accumulation, promoting the apoptosis of the SKOV3PT cells. Furthermore, TPL synergistically enhanced the cytotoxicity of cisplatin against platinum-resistant ovarian cancer cells. Collectively, these findings suggest that TPL is able to overcome chemoresistance and that it may be an effective treatment for platinum-resistant ovarian cancer, either alone or as an adjuvant therapy.

Peritoneal metastasis is the most frequent cause of death in patients with advanced gastric carcinoma (GC). The phosphatase of regenerating liver-3 (PRL-3) is recognized as an oncogene and plays an important role in GC peritoneal metastasis. However, the mechanism of how PRL-3 regulates GC invasion and metastasis is unknown. In the present study, we found that PRL-3 presented with high expression in GC with peritoneal metastasis, but phosphatase and tensin homologue (PTEN) was weakly expressed. The p-PTEN/PTEN ratio was also higher in GC with peritoneal metastasis than that in the normal gastric tissues. We also found the same phenomenon when comparing the gastric mucosa cell line with the GC cell lines. After constructing a wild-type and a mutant-type plasmid without enzyme activity and transfecting them into GC SGC7901 cells, we showed that only PRL-3 had enzyme activity to downregulate PTEN and cause PTEN phosphorylation. The results also showed that PRL-3 increased the expression levels of MMP-2/MMP-9 and promoted the migration and invasion of the SGC7901 cells. Knockdown of PRL-3 decreased the expression levels of MMP-2/MMP-9 significantly, which further inhibited the migration and invasion of the GC cells. PRL-3 also increased the expression ratio of p-Akt/Akt, which indicated that PRL-3 may mediate the PI3K/Akt pathway to promote GC metastasis. When we transfected the PTEN siRNA plasmid into the PRL-3 stable low expression GC cells, the expression of p-Akt, MMP-2 and MMP-9 was reversed. In conclusion, our results provide a bridge between PRL-3 and PTEN; PRL-3 decreased the expression of PTEN as well as increased the level of PTEN phosphorylation and inactivated it, consequently activating the PI3K/Akt signaling pathway, and upregulating MMP-2/MMP-9 expression to promote GC cell peritoneal metastasis.