Down-regulation of HECTD3 by HER2 inhibition makes serous ovarian cancer cells sensitive to platinum treatment.

Resistance to platinum-based chemotherapy is a major cause of treatment failure in patients with epithelial ovarian cancer and predicts a poor prognosis. Previously, we found that HECTD3 confers cancer cell resistance to apoptosis. However, the significance of HECTD3 expression in ovarian cancer and its regulatory mechanisms were unknown. Here, we found that HECTD3 depletion promotes carboplatin-induced apoptosis in both an ovarian cancer cell model and a xenograft mouse model. Moreover, high HECTD3 expression is significantly associated with poor platinum response and prognosis in ovarian cancer patients. We further demonstrated that HER2 can up-regulate HECTD3 expression through activating STAT3. Furthermore, HER2 inhibitors, such as lapatinib, down-regulate HECTD3 expression and thus promote the chemosensitivity of ovarian cancer cells to carboplatin. Lapatinib combined with carboplatin also significantly inhibits serous ovarian carcinoma growth compared with each drug alone in a xenograft mouse model. HECTD3 may be considered a promising molecular predictor of platinum chemosensitivity and prognosis for serous ovarian cancer. Through decreasing HECTD3, lapatinib possesses significantly increased anti-tumor activity when combined with carboplatin compared with each agent alone, which provides an optional therapeutic regimen for serous ovarian cancer.