SOX4 regulates invasion of bladder cancer cells via repression of WNT5a.

Abstract

Sry-Related HMG-BOX-4 (SOX4) is a developmental transcription factor that is overexpressed in as many as 23% of bladder cancer patients; however, the role of SOX4 in bladder cancer tumorigenesis is not yet well understood. Given the many roles of SOX4 in embryonic development and the context-dependent regulation of gene expression, in this study, we sought to determine the role of SOX4 in bladder cancer and to identify SOX4-regulated genes that may contribute to tumorigenesis. For this purpose, we employed a CRISPR interference (CRISPRi) method to transcriptionally repress SOX4 expression in T24 bladder cancer cell lines, 'rescued' these cell lines with the lentiviral-mediated expression of SOX4, and performed whole genome expression profiling. The cells in which SOX4 was knocked down (T24-SOX4-KD) exhibited decreased invasive capabilities, but no changes in migration or proliferation, whereas rescue experiments with SOX4 lentiviral vector restored the invasive phenotype. Gene expression profiling revealed 173 high confidence SOX4-regulated genes, including WNT5a as a potential target of repression by SOX4. Treatment of the T24-SOX4-KD cells with a WNT5a antagonist restored the invasive phenotype observed in the T24-scramble control cells and the SOX4 lentiviral-rescued cells. High WNT5a expression was associated with a decreased invasion and WNT5a expression inversely correlated with SOX4 expression, suggesting that SOX4 can negatively regulate WNT5a levels either directly or indirectly and that WNT5a likely plays a protective role against invasion in bladder cancer cells.