Loss of dihydrotestosterone-inactivation activity promotes prostate cancer castration resistance detectable by functional imaging

Abstract

Edited by Xiao-Fan WangAndrogens such as testosterone and dihydrotestosterone are a critical driver of prostate cancer progression. Cancer resistance to androgen deprivation therapies ensues when tumors engage metabolic processes that produce sustained androgen levels in the tissue. However, the molecular mechanisms involved in this resistance process are unclear, and functional imaging modalities that predict impending resistance are lacking. Here, using the human LNCaP and C4-2 cell line models of prostate cancer, we show that castration treatment-sensitive prostate cancer cells that normally have an intact glucuronidation pathway that rapidly conjugates and inactivates dihydrotestosterone and thereby limits androgen signaling, become glucuronidation deficient and resistant to androgen deprivation. Mechanistically, using CRISPR/Cas9-mediated gene ablation, we found that loss of UDP glucuronosyltransferase family 2 member B15 (UGT2B15) and UGT2B17 is sufficient to restore free dihydrotestosterone, sustained androgen signaling, and development of castration resistance. Furthermore, loss of glucuronidation enzymatic activity was also detectable with a nonsteroid glucuronidation substrate. Of note, glucuronidation-incompetent cells and the resultant loss of intracellular conjugated dihydrotestosterone were detectable in vivo by 18 F-dihydrotestosterone PET. Together, these findings couple a mechanism with a functional imaging modality to identify impending castration resistance in prostate cancers.The long-standing standard treatment for advanced prostate cancer is androgen deprivation therapy by way of medical or surgical castration (1). Therapeutic responses usually occur and tumors eventually develop resistance as castration-resistant prostate cancer (CRPC) 2 (2, 3). This resistant state is frequently first heralded by a rising prostate-specific antigen (PSA), which is an androgen-responsive gene and is indicative of a reinstatement of androgen receptor (AR) stimulation (4). CRPC is also accompanied by tumors developing the metabolic capability of regenerating their own potent androgens, i.e. testosterone and/or dihydrotestosterone (DHT), from extragonadal precursor steroids (5-7). The role and requirement for extragonadal androgen synthesis in advanced prostate cancer was recently bolstered by a profound prolongation of survival in clinical trials of patients treated upfront with extragonadal androgen synthesis inhibition in addition to castration (8,9).The metabolic mechanisms that enable sustained tissue concentrations of potent androgens in CRPC that occurs alongside the absence of gonadal testosterone in circulation remain poorly understood. Furthermore, imaging for prostate cancer is very limited and mainly focused on tumor localization. There is a complete absence of functional imaging approaches that are informative of the metabolic state of the disease that provides information on tumor susceptibility to systemic therapies in the clinical standard of care.Glucuronidation is a major mechanism of androgen...

Emerging roles for UDP-glucuronosyltransferases in drug resistance and cancer progression

“…76 The somatic loss of UGT2B17 in tumour cells is associated with the development of a castration-resistant phenotype in vitro and in xenograft mouse models, consistent with the importance of this pathway in ligand-dependent pre-androgen receptor control of androgen metabolism. 79 Indeed, inherited or acquired loss or inhibition of the UGT androgen inactivation pathway increases exposure to local androgens, enhances androgen receptor activation and promotes cancer-cell proliferation. 80 However, there is accumulating evidence that UGT overexpression could function as an independent prognostic factor associated with the progression of prostate cancer.…”

Identification of transcription factor co-regulators that drive prostate cancer progression

“…AR target genes notably associated with energy production were repressed, including the putative tumor suppressor hydroxyprostaglandin dehydrogenase ( HPGD ) 75 , as well as Acyl-CoA synthetase long chain family member 3 (ACSL3) 76 and Alpha-2-glycoprotein 1, zinc-binding ( AZGP1 ) 77 . Up-regulated peroxisome genes included retinoic acid anabolizing enzyme, Dehydrogenase/Reductase 3 ( DHRS3 ) 78 , and the steroid catabolizing enzyme UDP Glucuronosyltransferase Family 2 Member B17 ( UGT2B17 ) 79 . These changes in hallmark gene sets suggests that altered PGC1α disrupts the energetic utilization of the cell and distorts AR signaling.…”

Intracrinology-revisited and prostate cancer

“…However, in a castrate environment these cells may become glucuronidation deficient and resistant to androgen deprivation. Using CRISPR/Cas9mediated gene ablation, loss of UDP glucuronosyltransferase family 2 member B15α(UGT2B15) and UGT2B17 was sufficient to restore free 5α-DHT, sustain androgen signaling, and lead to the development of castration resistance (41). However paradoxically, several studies show that these enzymes are elevated in CRPC and may represent adaptive changes to make the tumor independent of AR ligands (42)(43)(44).…”