HUS1 as a Potential Therapeutic Target in Urothelial Cancer.

Platinum-based chemotherapy is the standard of care with concern to first-line systemic therapy for metastatic disease in urothelial cancer (UC). Resistance to chemotherapy despite an initial response is linked with the ability to remove platinum-based DNA adducts and to repair chemotherapy-induced DNA lesions by various DNA repair proteins. The Rad9-Rad1-HUS1 complex that is loaded onto DNA at sites of damage is involved in checkpoint activation as well as DNA repair. Here, we addressed for the first time the potential influence of HUS1 expression in urothelial carcinogenesis (using two human basal urothelial cancer cell lines UM-UC-3 and HT1197) and its role as a potential therapeutic target for predicting responses to platinum-based chemotherapy. Specific inhibition of HUS1 expression in both cell lines was achieved by specific siRNA and validated by Western blot. In order to define the possible importance of HUS1 in the regulation of cellular proliferation, parental and resistant cells were treated with increasing concentrations of either control or HUS1 siRNA. HUS1 protein expression was observed in both human basal urothelial cancer cell lines UM-UC-3 and HT1197. In cisplatin-sensitive cells, knock-down of HUS1 inhibited cellular proliferation in the presence of cisplatin. On the contrary, knock-down of HUS1 in resistant cells did not result in a re-sensitization to cisplatin. Finally, RNAseq data from the Cancer Genome Atlas provided evidence that HUS1 expression is a significant prognostic factor for poor survival in UC patients. In summary, HUS1 may acts as an oncogene in UC and might be a key determinant of the cellular response to cisplatin-based chemotherapy.