Glutamine Transporters are Targets of Multiple Oncogenic Signaling Pathways in Prostate Cancer

Despite the known importance of androgen receptor (AR) signaling in prostate cancer, the processes downstream of AR that drive disease development and progression remain poorly understood. This knowledge gap has thus limited the ability to treat cancer. Here, it is demonstrated that androgens increase the metabolism of glutamine in prostate cancer cells. This metabolism was required for maximal cell growth under conditions of serum starvation. Mechanistically, AR signaling promoted glutamine metabolism by increasing the expression of the glutamine transporters SLC1A4 and SLC1A5 , genes commonly overexpressed in prostate cancer. Correspondingly, gene expression signatures of AR activity correlated with SLC1A4 and SLC1A5 mRNA levels in clinical cohorts. Interestingly, MYC, a canonical oncogene in prostate cancer and previously described master regulator of glutamine metabolism, was only a context-dependent regulator of SLC1A4 and SLC1A5 levels, being unable to regulate either transporter in PTEN wild-type cells. In contrast, rapamycin was able to decrease the androgen-mediated expression of SLC1A4 and SLC1A5 independent of PTEN status, indicating that mTOR complex 1 (mTORC1) was needed for maximal AR-mediated glutamine uptake and prostate cancer cell growth. Taken together, these data indicate that three well-established oncogenic drivers (AR, MYC, and mTOR) function by converging to collectively increase the expression of glutamine transporters, thereby promoting glutamine uptake and subsequent prostate cancer cell growth. Implications: AR, MYC, and mTOR converge to increase glutamine uptake and metabolism in prostate cancer through increasing the levels of glutamine transporters. Mol Cancer Res; 15(8); 1017–28. ©2017 AACR .