Overexpression of c-Myc antagonises transcriptional output of the androgen receptor in prostate cancer [expression]. Homo sapiens

Prostate cancer is the most common non-cutaneous cancer in men. The androgen receptor (AR) a ligand-activated transcription factor, constitutes the main drug target for advanced cases of the disease. However, a variety of other transcription factors and signalling networks have been shown to be altered in patients and to influence AR activity. The oncogenic transcription factor c-Myc has been studied extensively in multiple malignancies, but its impact on AR activity in prostate cancer remains elusive. In this study we assessed the impact of clinically relevant levels of c-Myc overexpression on AR activity and transcriptional output. We found that c-Myc and the AR share a substantial amount of binding sites, which exhibit enhancer-like characteristics. Interestingly, c-Myc overexpression altered global AR chromatin occupancy and antagonised a subset of androgen-induced genes. Furthermore, c-Myc overexpression modified histone marks, most notably H3K4me1 and H3K27me3. Lastly, we validated the antagonistic relationship between c-Myc and two AR target genes, KLK3 and GNMT, in patient samples. Overall design: Total RNA of three biological replicates for each condition was extracted using the RNeasy kit (Qiagen), conditions are: 5 h vehicle, 5h R1881, 5 h Doxycycline, 5h R17881+Dox, 12 h vehicle, 12h R1881, 12 h Doxycyline and 12h R1881+Dox