A cell-based assay for screening spindle checkpoint inhibitors.

In eukaryotes, the spindle checkpoint acts as a surveillance mechanism that ensures faithful chromosome segregation. The spindle checkpoint prevents premature separation of sister chromatids and the onset of anaphase until every chromosome is properly attached to the mitotic spindle. Tumorigenesis might result from generation of aneuploidy by dysfunction of the spindle checkpoint. Differences of the checkpoint system in normal cells versus tumor cells might provide a new opportunity in cancer drug development; therefore, efforts to identify the spindle checkpoint inhibitors have been fostered. Based on spindle checkpoint inhibitors being able to induce cells to exit mitotic arrest caused by microtubule drug treatment, we developed a cell-based assay to screen compounds that were potential spindle checkpoint inhibitors. This assay was validated with a known spindle checkpoint inhibitor and was easy to adapt to a large-scale screening. It also had the advantages of being high in sensitivity and low in cost.

Praziquantel synergistically enhances paclitaxel efficacy to inhibit cancer cell growth.

The major challenges we are facing in cancer therapy with paclitaxel (PTX) are the drug resistance and severe side effects. Massive efforts have been made to overcome these clinical challenges by combining PTX with other drugs. In this study, we reported the first preclinical data that praziquantel (PZQ), an anti-parasite agent, could greatly enhance the anticancer efficacy of PTX in various cancer cell lines, including PTX-resistant cell lines. Based on the combination index value, we demonstrated that PZQ synergistically enhanced PTX-induced cell growth inhibition. The co-treatment of PZQ and PTX also induced significant mitotic arrest and activated the apoptotic cascade. Moreover, PZQ combined with PTX resulted in a more pronounced inhibition of tumor growth compared with either drug alone in a mouse xenograft model. We tried to investigate the possible mechanisms of this synergistic efficacy induced by PZQ and PTX, and we found that the co-treatment of the two drugs could markedly decrease expression of X-linked inhibitor of apoptosis protein (XIAP), an anti-apoptotic protein. Our data further demonstrated that down-regulation of XIAP was required for the synergistic interaction between PZQ and PTX. Together, this study suggested that the combination of PZQ and PTX may represent a novel and effective anticancer strategy for optimizing PTX therapy.