Cytoplasmic translocation of Cx32 mediates cisplatin resistance in ovarian cancer cells / 中国药理学与毒理学杂志

ABSTRACT

OBJECTIVE To investigate the underlying mechanism of drug resistance to cisplatin and increasing the sensitivity to therapeutic drugs are key steps towards the improved treatment of patients with ovarian cancer. Gap junction (GJ) and connexin (Cx) are closely related to tumor formation, but the relationship between cisplatin resistance and GJ or Cx are undetermined. METHODS We established the cisplatin-resistant human ovarian cancer cell line A2780-CDDP over an 11-month period, with the concentration of cisplatin gradually increasing from 0.5 g·L-1 to 16 g·L-1. To explore the effect of GJ in the process of cisplatin resistance, we investigated GJ using a parachute dyecoupling assay in A2780- RI(1.2), A2780- RI(1.7), A2780- RI(2.9), A2780- RI(4.3) and A2780- CDDP cells. We further explored whether the Cxs responsible for GJ were related to cisplatin resistance. In A2780- RI(1.2), A2780-RI(1.7), A2780-RI(2.9), A2780-RI(4.3) and A2780-CDDP, we used q-PCR to analyze the levels of Cx43, Cx40, Cx37, and Cx32. To confirm the effect of Cx32 on cisplatin resistance, we knocked down Cx32 in A2780-CDDP cells with siRNA-Cx32. As GJ was decreased whereas Cx32 expression was elevated during the cisplatin resistance process, it drove us to explore the underlying mechanism. To resolve this issue, we extracted membrane-bound and cytoplasmic proteins from A2780 and A2780-CDDP cells. RESULTS Here we showed that cisplatin resistance was correlated to the loss of GJ and the upregulation of Cx32 expression. Enhancing GJ in A2780-CDDP cells could increase the apoptotic response to cisplatin treatment. Furthermore, although Cx32 expression was increased in A2780-CDDP cells, it was more localized to the cytoplasm rather than in the membrane, and knockdown of Cx32 in A2780-CDDP cells sensitized them to cisplatin treatment. CONCLUSION In summary, Cx32 is involved in cisplatin resistance, and cytoplasmic Cx32 plays an important role in chemoresistance.