Androgen regulation controlled NOVA1 gene expression drives alternative gene splicing in prostate cancer

Abstract

Prostate cancer is a genetic disease that is known to be regulated by androgen hormones that primarily arises in epithelial cells of the prostate gland. While epithelial splicing regulatory proteins (ESRP1 and ESRP2) have been established to be key players in prostate cancer progression, particularly through their androgen-dependent regulation leading to alternative splicing events, the role of mesenchymal – specific RNA binding proteins has not largely been explored. This study focuses on NOVA1 gene, a mesenchymal RNA-binding protein, to determine its role in prostate cancer. The research objectives included assessing NOVA1 expression in various prostate cancer cell lines, analysing NOVA1 protein regulation under different androgen exposure conditions, and identifying cell lines with highest NOVA1 expression (PC3) and lowest NOVA1 expression (LNCaP) to understand its association with different prostate cancer phenotypes, particularly aggressive vs benign. Using a combination of lab techniques, I quantified NOVA1 levels and investigated its regulation mechanism. Additionally, RNA sequencing (RNAseq) was carried out following NOVA1 knockdown in PC3 cells to evaluate its impact on ESRP1 and ESRP2 target splicing events, with subsequent bioinformatic analysis approaches. My findings revealed that NOVA1 is inversely regulated by androgens in comparison to ESRP1 and ESRP2, with its expression significantly elevated in the highly aggressive PC3 prostate cancer cell line. Further a study by Zhang et al. in 2020, found high NOVA1 expression in neuroendocrine prostate cancer cell lines, known for their aggressive nature. NOVA1's influence on alternative splicing is diverse, mirroring ESRP1 and ESRP2's effects on certain events while exerting opposing effects on other events. NOVA1 has been predicted to have mesenchymal properties that contribute to cell mobility and tumour metastasis. These properties are supported by the differential expression analysis where several of the NOVA1 regulated genes associated with pathways such as EMT, G2M, and E2F signifying NOVA1 role in cell mobility, cell cycle regulation, and metastasis. In conclusion, NOVA1 emerges as a pivotal gene in prostate cancer, highlighting the critical role of mesenchymal RNA-binding proteins in the disease development. The regulatory connect between NOVA1 and ESRP1 and ESRP2 underscores the complexity of androgen-driven alternative splicing in prostate cancer. These findings point to NOVA1 as a potential target for therapeutic intervention, particularly in combating aggressive forms of the disease.