DR2 Blocker Thioridazine: A Promising Candidate Drug For Ovarian Cancer Therapy

Objective: Dopamine receptor 2(DR2) may be a biomarker for cancers. Ovarian cancer over-expressed DR2 as well. Blocking DR2 may be a novel treatment strategy for ovarian cancer. Thioridazine, a DR2 blocker, has antineoplastic activity in a variety of cancer cells. In view of the need for new treatment agent in ovarian cancer, we endeavour to determine the potential effects of thioridazine on the proliferation, apoptosis and autophagy of ovarian cancer cells.Method: After being treated with thioridazine, the proliferation, apoptosis rate, cellur ROS, nuclear DNA damage, and the location of LC3 were detected by CCK-8 assay, the flow cytometry, DCFH-DA staining, comet assay, and the immunofluorescence assay. The expression of proteins as DR2, Cleaved Caspase-3, LC3, P62, Nrf2/p-Nrf2, HO-1, were assessed by Western blotting.Results:The proliferation of SKOV3 and A2780 were suppressed by thioridazine in a dose dependent manner(p<0.05). The flow cytometry demonstrated a higher percentage of apoptotic cells after 24-h thioridazine treatment(p<0.05). The expression level of cleaved Caspase-3(a marker of apoptosis) was increased after 24-h treatment. The ROS level and comet formation rate(SKOV3: 8.33±1.53% vs 30.33±3.21% p<0.05; A2780: 5.67±2.08% p<0.05) were increased after thioridazine treatment. The expression of p-Nrf2, a pivotal transcriptional factor of cellular responses to oxidative stress, and its downstream targets HO-1, NQO1 and HIF-1α were decreased. The expression of VEGF, a pivotal enabling factor for tumor angiogenesis, was reduced. LC3-Ⅱ was significantly up-regulated in a doseand time-dependent manner in both cell lines after thioridazine treatement. Using 3-MA to inhibit autophagy leaded to an increased apoptosis rate(p<0.05). The activity of ERK and AKT was detected with western blot, phosphorylation AKT was down-regulated, while the phosphorylation of ERK was up-regulated. Consistent with the expression of phosphorylation of ERK, the phosphorylation of P38 was increased. The phosphorylation of JNK, however, had not been detected.Conclusion: Thioridazine treatment leaded to apoptosis, which may attribute to increased level of ROS, the unbalance of antioxidant stress systems and DNA damage. Additionally, thioridazine may via AKT/ERK signal path induced the autophagy, which may be a pro-survival mechanism in thioridazine- induced cytotoxicity in ovarian cancer cells. The present study demonstrated that the DR2 blocker thioridazine possesses anti-ovarian cancer ability in vitro, suggesting that thioridazine may be used as a potential drug in ovarian cancer therapy.