lb-100 and Ovarian-Neoplasms

Ovarian cancer is a gynecological malignancy with high mortality. Adjuvant therapy such as chemoradiotherapy inevitably leads to side effects and drug resistance. In recent years, traditional Chinese medicine has been widely studied for its safety, effectiveness, and unique pharmacological effects. Polyphyllin VII is an important component of Rhizoma paridis saponins, and has cytotoxic effects on many types of cancer cells. The aim of the present study was to evaluate the anti‑tumor activity of polyphyllin VII in human ovarian cancer cells. Recent studies found that polyphyllin VII induces mitochondrial pathway apoptosis by increasing mitochondrial division, but the specific mechanism was unclear. The results of this study revealed that polyphyllin VII could effectively induce mitochondrial dysfunction, including increased mitochondrial division and reactive oxygen species (ROS) production. Notably, the mitochondrial location of dynamin‑related protein 1 (DRP1) plays an important role in its function. In addition, polyphyllin VII enhanced the mitochondrial localization of DRP1 which is mediated by increased protein phosphatase 2A (PP2A) activity, and decreased AKT activity. A specific PP2A inhibitor, LB100, attenuated mitochondrial division and apoptosis in cells caused by polyphyllin VII, confirming the function of the PP2A/AKT pathway in polyphyllin VII treatment. Additionally, xenotransplantation experiments have also confirmed the anti‑tumor effect of polyphyllin VII in vivo. Therefore, interference of the mitochondrial translocation of DRP1 through PP2A/AKT pathway may be an attractive and effective therapeutic approach by polyphyllin VII in ovarian cancer. This may provide new strategies for polyphyllin VII in the clinical treatment of ovarian cancer.

Topics: Animals; Apoptosis; Cell Fractionation; Cell Line, Tumor; Dynamins; Female; Humans; Mice; Mitochondria; Ovarian Neoplasms; Piperazines; Protein Phosphatase 2; Proto-Oncogene Proteins c-akt; Saponins; Signal Transduction; Xenograft Model Antitumor Assays

Despite early positive response to platinum-based chemotherapy, the majority of ovarian carcinomas develop resistance and progress to fatal disease. Protein phosphatase 2A (PP2A) is a ubiquitous phosphatase involved in the regulation of DNA-damage response (DDR) and cell-cycle checkpoint pathways. Recent studies have shown that LB100, a small-molecule inhibitor of PP2A, sensitizes cancer cells to radiation-mediated DNA damage. We hypothesized that LB100 could sensitize ovarian cancer cells to cisplatin treatment. We performed in vitro studies in SKOV-3, OVCAR-8, and PEO1, -4, and -6 ovarian cancer lines to assess cytotoxicity potentiation, cell-death mechanism(s), cell-cycle regulation, and DDR signaling. In vivo studies were conducted in an intraperitoneal metastatic mouse model using SKOV-3/f-Luc cells. LB100 sensitized ovarian carcinoma lines to cisplatin-mediated cell death. Sensitization via LB100 was mediated by abrogation of cell-cycle arrest induced by cisplatin. Loss of the cisplatin-induced checkpoint correlated with decreased Wee1 expression, increased cdc2 activation, and increased mitotic entry (p-histone H3). LB100 also induced constitutive hyperphosphorylation of DDR proteins (BRCA1, Chk2, and γH2AX), altered the chronology and persistence of JNK activation, and modulated the expression of 14-3-3 binding sites. In vivo, cisplatin sensitization via LB100 significantly enhanced tumor growth inhibition and prevented disease progression after treatment cessation. Our results suggest that LB100 sensitizes ovarian cancer cells to cisplatin in vitro and in vivo by modulation of the DDR pathway and cell-cycle checkpoint abrogation.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Bridged Bicyclo Compounds, Heterocyclic; Cell Cycle; Cell Line, Tumor; Cisplatin; Drug Synergism; Female; Gene Expression Regulation, Neoplastic; Humans; Mice; Ovarian Neoplasms; Piperazines; Protein Phosphatase 2; Signal Transduction; Treatment Outcome; Xenograft Model Antitumor Assays