UDP-glucuronosyltransferase 2B15 (UGT2B15) and UGT2B17 Enzymes Are Major Determinants of the Androgen Response in Prostate Cancer LNCaP Cells

Abstract

Uridine diphosphate-glucuronosyltransferase 2 (UGT2)B15 and B17 enzymes conjugate dihydrotestosterone (DHT) and its metabolites androstane-3␣,17␤-diol (3␣-DIOL) and androsterone (ADT). The presence of UGT2B15/B17 in the epithelial cells of the human prostate has been clearly demonstrated, and significant 3␣-DIOL glucuronide and ADT-glucuronide concentrations have been detected in this tissue. The human androgen-dependent cancer cell line, LNCaP, expresses UGT2B15 and -B17 and is also capable of conjugating androgens. To assess the impact of these two genes in the inactivation of androgens in LNCaP cells, their expression was inhibited using RNA interference. The efficient inhibitory effects of a UGT2B15/B17 small interfering RNA (siRNA) probe was established by the 70% reduction of these UGT mRNA levels, which was further confirmed at the protein levels. The glucuronidation of dihydrotestosterone (DHT), 3␣-DIOL, and ADT by LNCaP cell homogenates was reduced by more than 75% in UGT2B15/B17 siRNA-transfected LNCaP cells when compared with cells transfected with a nontarget probe. In UGT2B15/B17-deficient LNCaP cells, we observe a stronger response to DHT than in control cells, as determined by cell proliferation and expression of eight known androgen-sensitive genes. As expected, the amounts of DHT in cell culture media from control cells were significantly lower than that from UGT2B15/B17 siRNA-treated cells, which was caused by a higher conversion to its corresponding glucuronide derivative. Taken together these data support the idea that UGT2B15 and -B17 are critical enzymes for the local inactivation of androgens and that glucuronidation is a major determinant of androgen action in prostate cells.Production and secretion of testosterone by the testis has long been considered one of the major factors influencing androgen function in androgen target tissues, namely, the prostate. Thus, circulating testosterone taken up from the circulation is converted by 5␣-reductase to dihydrotestosterone (DHT), 4 the natural androgen receptor agonist (1). There is clear evidence now that adrenal steroid precursors, namely dehydroepiandrosterone and its sulfate, are converted to testosterone in several tissues (2, 3). The observation that the DHT concentration in prostate is only decreased by 50% in castrated patients treated for prostate cancer further support the role of adrenal steroid precursors as a source of androgens (4 -6). These findings of local transformation of circulating steroids into bioactive testosterone and DHT have been integrated in the process called "intracrinology," where several steroidogenic enzymes, including 3␣-hydroxysteroid dehydrogenase-⌬4 -5 isomerase (3␣-HSD type 1), 17␤-HSDs, and 5␣-reductase, contribute to the formation of DHT (2, 7). Growing evidence indicates that tissue DHT concentrations are also modulated by 3␣-hydroxysteroid dehydrogenase (3␣-HSD) type 3 and 17␤-HSD type 7, which form inactive androstane-3␣,17␤-diol (3␣-DIOL) and androsterone (ADT) (8, 9). Although extremely important in...

Androgen receptor mediates the expression of UDP‐glucuronosyltransferase 2 B15 and B17 genes

“…These two enzymes are critical for the inactivation of DHT and its metabolites 3α-DIOL and ADT. Glucuronidation is a significant mediator of the androgen response in prostate cells [17]. It has been intriguing to observe that androgens rapidly down-regulate the glucuronidation activity and the expression of UGT2B15 and B17 in LNCaP cells, perhaps as a means of facilitating their biological activities [18][19][20].…”

“…UGT2B15 and B17 are critical enzymes for the local inactivation of androgens. Knocking down UGT2B15 and B17 expression efficiently reduced the glucuronidation of DHT, 3α-DIOL and ADT, and subsequently altered the expression of androgen dependent genes [17].…”

Association of Uridine Diphosphate-Glucuronosyltransferase 2B Gene Variants with Serum Glucuronide Levels and Prostate Cancer Risk

“…, and UGT2B15 enzymes in the liver, skin, and prostate tissue (Turgeon et al, 2001;Chouinard et al, 2007;Valentini et al, 2007). Narrow black arrows indicate reversible catabolism of DHT; thick black arrows indicate irreversible production of testosterone-and DHT-G; gray arrows (on left and right) indicate irreversible production of ADT-G; and parallel black outlined arrows indicate irreversible production of AAG.…”

Calcitrol (1α,25-dihydroxyvitamin D3) inhibits androgen glucuronidation in prostate cancer cells

“…The formation of glucuronide conjugates was analyzed by high-performance liquid chromatography using identification by mass spectrometry as already reported (28,29).…”

“…Glucuronidation assays were conducted using 20 Ag total protein from homogenized LNCaP cells as described previously (28). The formation of glucuronide conjugates was analyzed by high-performance liquid chromatography using identification by mass spectrometry as already reported (28,29).…”