Purpose: Carboplatin is a first-line treatment for ovarian cancer. However, most patients develop resistance and undergo disease recurrence. This study aims to explore the relationship between the expression of X-linked inhibitor of apoptosis protein (XIAP) and carboplatin sensitivity in ovarian cancer. Patients and methods: We examined the expression of XIAP in ovarian cancer by immunochemistry. Next, we investigated the role of XIAP in regulating carboplatin sensitivity in ovarian cancer ES2 and 3AO cells through Cell Counting Kit-8 cell viability assay and fluorescein isothiocyanate-Annexin V/propidium iodide apoptosis assay. Expression of apoptotic effectors was measured by Western blot. Results: The immunochemistry results showed that high XIAP expression levels inversely correlated with carboplatin response (P=0.03) and progression-free survival (P=0.0068) in patients with ovarian cancer. Knockdown of XIAP repressed the cell viabilities in the carboplatin-treated cells and increased carboplatin-induced caspase activation. In summary, our data show that XIAP mediates carboplatin sensitivity of ovarian cancer. Conclusion: In summary, our data show that XIAP mediates carboplatin sensitivity of ovarian cancer and XIAP may be a novel target for the treatment of carboplatin-resistant ovarian cancer.

Breast cancer is the most prevalent malignancy in women, which remains untreatable once metastatic. The treatment of advanced breast cancer is restricted due to chemotherapy resistance. We previously investigated anti-cancer potential of a tumor selective oncolytic adenovirus along with cisplatin in three lung cancer cells; A549, H292, and H661, and found it very efficient. To our surprise, this virotherapy showed remarkable cytotoxicity to chemo-resistant cancer cells. Here, we extended our investigation by using two breast cancer cells and their resistant sublines to further validate CRAd’s anti-resistance properties. Results of in vitro and in vivo analyses recapitulated the similar anti-tumor potential of CRAd. Based on the molecular analysis through qPCR and western blotting, we suggest upregulation of coxsackievirus-adenovirus receptor (CAR) as a selective vulnerability of chemotherapy-resistant tumors. CAR knockdown and overexpression experiments established its important involvement in the success of CRAd-induced tumor inhibition. Additionally, through transwell migration assay we demonstrate that CRAd might have anti-metastatic properties. Mechanistic analysis show that CRAd pre-treatment could reverse epithelial to mesenchymal transition in breast cancer cells, which needs further verification. These insights may prove to be a timely opportunity for the application of CRAd in recurrent drug-resistant cancers.