Glycosylation regulates the stability of c-MYC

Tumorigenesis is characterised by changes in transcriptional regulation and the androgen receptor (AR) has been identified as a key driver in prostate cancer. In this study, we show that the hexosamine biosynthetic pathway (HBP) genes are overexpressed in clinical prostate cancer and androgen-regulated in cell-lines. HBP senses metabolic status of the cell and produces an essential substrate for O-GlcNAc transferase (OGT), which regulates target proteins via glycosylation. Using immunohistochemistry, we found that OGT is up-regulated in the protein level in prostate cancer (n=1987) and its expression correlates with high Gleason Score, pT and pN stages and biochemical recurrence (for all, p<0.0001). Both a small molecule inhibitor and siRNAs targeting OGT decreased prostate cancer cell growth. Microarray profiling revealed that the principal effects of the OGT inhibitor in prostate cancer cells are on cell cycle progression and DNA replication. We identified MYC as a candidate upstream regulator of these genes and found that OGT inhibitor caused a dose-dependent loss of c-MYC protein but not mRNA in cell lines. Finally, we observed a statistically significant co-expression between c-MYC and OGT in human prostate cancer samples (n=1306, p=0.0012). Total RNA was extracted and experiment has three biological replicates for each condition, conditions are: 12 hours ST045849, 24 hours ST045849, 12 hours vehicle, 24 hours vehicle, 12 hours siOGT, 24 hours siOGT, 12 hours scrambled, 24 hours scrambled