Nrf1 and Nrf2 transcription factors regulate androgen receptor transactivation in prostate cancer cells.
Despite androgen deprivation therapy (ADT), persistent androgen receptor (AR) signaling enables outgrowth of castration resistant prostate cancer (CRPC). In prostate cancer (PCa) cells, ADT may enhance AR activity through induction of oxidative stress. Herein, we investigated the roles of Nrf1 and Nrf2, transcription factors that regulate antioxidant gene expression, on hormone-mediated AR transactivation using a syngeneic in vitro model of androgen dependent (LNCaP) and castration resistant (C4-2B) PCa cells. Dihydrotestosterone (DHT) stimulated transactivation of the androgen response element (ARE) was significantly greater in C4-2B cells than in LNCaP cells. DHT-induced AR transactivation was coupled with higher nuclear translocation of p65-Nrf1 in C4-2B cells, as compared to LNCaP cells. Conversely, DHT stimulation suppressed total Nrf2 levels in C4-2B cells but elevated total Nrf2 levels in LNCaP cells. Interestingly, siRNA mediated silencing of Nrf1 attenuated AR transactivation while p65-Nrf1 overexpression enhanced AR transactivation. Subsequent studies showed that Nrf1 physically interacts with AR and enhances AR's DNA-binding activity, suggesting that the p65-Nrf1 isoform is a potential AR coactivator. In contrast, Nrf2 suppressed AR-mediated transactivation by stimulating the nuclear accumulation of the p120-Nrf1 which suppressed AR transactivation. Quantitative RT-PCR studies further validated the inductive effects of p65-Nrf1 isoform on the androgen regulated genes, PSA and TMPRSS2. Therefore, our findings implicate differential roles of Nrf1 and Nrf2 in regulating AR transactivation in PCa cells. Our findings also indicate that the DHT-stimulated increase in p65-Nrf1 and the simultaneous suppression of both Nrf2 and p120-Nrf1 ultimately facilitates AR transactivation in CRPC cells.
Department of Pharmacology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America ; Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
Michelle A
MA
Schultz
Department of Urology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America.
Sharika S
SS
Hagan
Department of Urology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America.
Amrita
A
Datta
Laboratory of Cell Biochemistry and Gene Regulation, University of Chongqing, Chongqing, China.
Yiguo
Y
Zhang
Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
Michael L
ML
Freeman
Department of Urology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America.
Suresh C
SC
Sikka
Department of Urology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America.
Asim B
AB
Abdel-Mageed
Department of Pharmacology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America.
Debasis
D
Mondal
D000704:Analysis of Variance; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers / Q000235:genetics; D013196:Dihydrotestosterone / Q000494:pharmacology; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D015151:Immunoblotting; D008156:Luciferases; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D051266:Nuclear Respiratory Factor 1 / Q000378:metabolism*; D064129:Prostatic Neoplasms, Castration-Resistant / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D011944:Receptors, Androgen / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology*
D017931:DNA Primers; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; C495633:NRF1 protein, human; D051266:Nuclear Respiratory Factor 1; D011944:Receptors, Androgen; D013196:Dihydrotestosterone; D008156:Luciferases