Bruceine A Inhibits Cell Proliferation by Targeting the USP13/PARP1 Signalling Pathway in Multiple Myeloma

Multiple myeloma (MM) is an incurable hematologic malignancy, driving significant interest in the discovery of novel therapeutic strategies. Bruceine A (BA), a tetracyclic triterpene quassinoid derived from Brucea javanica, has shown anticancer properties by modulating multiple intracellular signalling pathways and exhibiting various biological effects. However, the specific pharmacological mechanisms by which it combats MM remain unclear. In this study, we identified USP13 as a potential target of BA. We observed a significant increase in USP13 expression in patients with MM, which was strongly associated with a poorer prognosis. Furthermore, enhanced USP13 expression can stimulate MM cell proliferation both in vitro and in vivo. Mass spectrometry analysis, combined with co-immunoprecipitation and in vitro ubiquitination experiments, revealed PARP1 as a critical downstream target of USP13. USP13 can stabilize PARP1 protein through deubiquitination, promoting PARP1-mediated DNA damage repair (DDR) and facilitating MM progression. Notably, we utilized MM cell lines, an MM Patient-Derived Tumour Xenograft model, and a 5TMM3VT mouse model to determine the anticancer effects of BA on MM progression, revealing its potential to target USP13/PARP1 signalling and disrupt DDR in MM cells. In conclusion, these findings suggest that BA inhibiting USP13/PARP1-mediated DDR might be a promising therapeutic strategy for MM.