Androgen receptor drives polyamine synthesis creating a vulnerability for prostate cancer
The androgen receptor (AR) enacts metabolic effects of the anabolic steroid testosterone, but how AR-directed metabolic changes affect prostate cancer progression is not well understood. Here, we show that the AR increases de novo polyamine synthesis by direct transcriptional regulation of ornithine decarboxylase (ODC) expression across cell types, including prostate cancer cells. Likewise, androgen treatment of prostate cancer models increased intracellular and secreted polyamines, a process that was critical for tumor development as both genetic and pharmacologic inhibition of AR-induced polyamine synthesis enhanced growth inhibition of prostate cancer by supraphysiological androgens. This polyamine reduction lessened negative feedback regulation of S-adenosylmethionine synthase 1 (AMD1), enhancing its utilization of S-adenosylmethionine (SAM), which reduced global protein methylation patterns and expression of the protooncogene MYC. The ODC inhibitor difluoromethylornithine (DFMO) was effective in reduction of polyamines in patients with metastatic CRPC even despite treatment with bipolar androgen therapy, supporting further study of this therapy combination. Thus, the AR is a critical regulator of polyamine synthesis, which may constitute a vulnerability in prostate cancer treated with bipolar androgen therapy. Overall design: LNCaP cell line was obtained from American Type Culture Collection (ATCC) and grown in RPMI 1640 (Gibco; 11835-055) supplemented with 10% fetal bovine serum (Corning), sodium lactate 1.6mM, sodium pyruvate 0.5mM, L-alanine 0.43mM, 1% pen-strep (Gibco). The vector pCDH-puro-cMyc vector (Addgene; 46970, J Wang laboratory) and pCDH-EF1-FHC empty vector control (Addgene, 64874, R Wood laboratory) were transfected into 293T cells (ATCC) along with pMD2.G (Addgene; 12259) and psPAX2 (Addgene; 12260) packaging vectors using lipofectamine (Invitrogen) to produce cMyc-puro, control-puro, and Tet-On-shAR-puro lentivirus particles. Two days after transduction with indicated virus, vector-expressing cells were selected with puromycin 1ug/ml for 72 hours. Cells were maintained at 37 °C in 5% CO2. They regularly tested negative for mycoplasma contamination using MycSensor PCR Assay kit (Agilent Technologies). R1881, DFMO, Putrescine and vehicle control were supplemented into the media of duplicate cultures and RNA obtained from the cells as processed as indicated.