Vitamin K epoxide reductase regulation of androgen receptor activity

// Ben Yi Tew 1 , Teresa B. Hong 2 , Maya Otto-Duessel 1 , Catherine Elix 1 , Egbert Castro 1 , Miaoling He 1 , Xiwei Wu 3 , Sumanta K. Pal 4 , Markus Kalkum 2 , Jeremy O. Jones 1 1 Department of Cancer Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA, USA 2 Department of Molecular Immunology, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA, USA 3 Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA, USA 4 Department of Medical Oncology, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA, USA Correspondence to: Jeremy O. Jones, email: jjones@coh.org Keywords: prostate cancer, vitamin K epoxide reductase, warfarin, androgen receptor, PPAR Received: July 04, 2016      Accepted: January 04, 2017      Published: January 13, 2017 ABSTRACT Long-term use of warfarin has been shown to be associated with a reduced risk of prostate cancer. Warfarin belongs to the vitamin K antagonist class of anticoagulants, which inhibit vitamin K epoxide reductase (VKOR). The vitamin K cycle is primarily known for its role in γ-carboxylation, a rare post-translational modification important in blood coagulation. Here we show that warfarin inhibits the transcriptional activity of the androgen receptor (AR), an important driver of prostate cancer development and progression. Warfarin treatment or knockdown of its target VKOR inhibits the activity of AR both in cell lines and in mouse prostate tissue. We demonstrate that AR can be γ-carboxylated, and mapped the γ-carboxylation to glutamate residue 2 (E2) using mass spectrometry. However, mutation of E2 and other glutamates on AR failed to suppress the effects of warfarin on AR suggesting that inhibition of AR is γ-carboxylation independent. To identify pathways upstream of AR signaling that are affected by warfarin, we performed RNA-seq on prostates of warfarin-treated mice. We found that warfarin inhibited peroxisome proliferator-activated receptor gamma (PPARγ) signaling, which in turn, inhibited AR signaling. Although warfarin is unfit for use as a chemopreventative due to its anticoagulatory effects, our data suggest that its ability to reduce prostate cancer risk is independent of its anticoagulation properties. Furthermore, our data show that warfarin inhibits PPARγ and AR signaling, which suggests that inhibition of these pathways could be used to reduce the risk of developing prostate cancer.