Squalene monooxygenase facilitates bladder cancer development in part by regulating PCNA.

Bladder cancer (BC) is one of the most common cancers worldwide. Although the treatment and survival rate of BC are being improved, the risk factors and the underlying mechanisms causing BC are incompletely understood. Squalene monooxygenase (SQLE) has been associated with the occurrence and development of multiple cancers but whether it contributes to BC development is unclear. In this study, we performed bioinformatics analysis on paired BC and adjacent non-cancerous tissues and found that SQLE expression is significantly upregulated in BC samples. Knockdown of SQLE impairs viability, induces apoptosis, and inhibits the migration and invasion of BC cells. RNA-seq data reveals that SQLE deficiency leads to dysregulated expression of genes regulating proliferation, migration, and apoptosis. Mass spectrometry-directed interactome screening identifies proliferating cell nuclear antigen (PCNA) as an SQLE-interacting protein and overexpression of PCNA partially rescues the impaired viability, migration, and invasion of BC cells caused by SQLE knockdown. In addition, we performed xenograft assays and confirmed that SQLE deficiency inhibits BC growth in vivo. In conclusion, these data suggest that SQLE promotes BC development and SQLE inhibition may be therapeutically useful in BC treatment.