EFFECT OF INTERLEUKINS ON UGT2B15 AND UGT2B17 STEROID URIDINE DIPHOSPHATE-GLUCURONOSYLTRANSFERASE EXPRESSION AND ACTIVITY IN THE LNCAP CELL-LINE

Cytokines are known to modulate the level of both phase 1 and phase 2 drug-metabolizing enzymes in hepatocytes. Although the effects of cyto kines on cytochrome P450 (CYP450) enzymes are well understood, there i s limited knowledge on how cytokines may affect steroid UDP-glucuronos yltransferase (UGT) phase 2 enzyme activity and expression in differen t cell types, including hepatocytes and steroid target cells. LNCaP ce lls, which is a human prostate cancer cell line, is a good model to st udy the effect of cytokines in steroid target cells because it is know n to express steroidogenic enzymes, including UGT2B15 and UGT2B17, whi ch are widely expressed steroid UGT enzymes known to conjugate androge ns. In this study, we examined the possible interaction among interleu kin-1 alpha (IL-1 alpha), IL-4, IL-6, and steroid UGT enzymes (UGT2B15 and UGT2B17). Treatment of LNCaP cells with IL-1 alpha led to a dose- dependent inhibition of dihydrotestosterone (DHT) glucuronidation. IL- 1 alpha decreased both UGT activity and LNCaP cell proliferation in th e absence and presence of DHT (0.5 nM); a maximal inhibition of 70% wa s observed. IL-6 inhibited LNCaP cell proliferation as well as the DHT -induced proliferation of these cells. However, neither IL-4 nor IL-6 significantly affected the formation of DHT glucuronide. Ribonuclease protection and Western blot analyses demonstrated a specific reduction of UGT2B17 transcript and protein levels in IL-lcr-treated LNCaP cell s. The level of UGT2B15 was not affected by cytokine treatments, indic ating a differential regulation between these two UGT enzymes. Transfe ction experiments performed with the UGT2B17 gene promoter region indi cates that the regulation occurs at the transcription level via putati ve cis-acting elements. This study indicates that cell proliferation a nd UGT expression in steroid-responsive cancer cells are differentiall y regulated depending on the cytokines present in the cell microenviro nment.