USP43 promotes gemcitabine resistance by regulating cholesterol homeostasis through E2F1 stabilization in bladder cancer

Gemcitabine (GEM) is a standard treatment for bladder cancer (BLCA), but resistance to this chemotherapy often reduces its efficacy. Thus, to uncover the molecular mechanisms of this resistance is essential to reverse GEM resistance. To explore the role of the USP43/E2F1/NSDHL pathway in GEM resistance in BLCA, we employed integrated analytical approaches including gene expression profiling, biochemical assays, xenograft models, among others. We discovered that the oncogene E2F1, which is highly expressed in GEM-resistant BLCA cells, plays a significant role in promoting resistance to the drug. We found that E2F1 enhances GEM resistance by activating NSDHL, an enzyme crucial for cholesterol biosynthesis, leading to increased cholesterol levels. We also identified USP43 as the deubiquitinase that stabilizes E2F1, contributing to its increased expression in response to GEM. Our study indicates the USP43/E2F1/NSDHL pathway as a key mechanism in cholesterol-mediated GEM resistance in BLCA, providing novel insights for therapeutic intervention to counteract chemoresistance.