Interaction between the Androgen Receptor and RNase L Mediates a Cross-talk between the Interferon and Androgen Signaling Pathways

Abstract

Signaling by androgens and interferons (IFN) plays an important role in prostate cancer initiation and progression. Using microarray analysis, we describe here a functional cross-talk between dihydrotestosterone and interferon signaling. Glutathione S-transferase pull-down and co-immunoprecipitation experiments reveal that the androgen receptor and the interferon-activated RNase L interact with each other in a ligand-dependent manner. Furthermore, overexpression of wild type RNase L confers IFN sensitivity to a dihydrotestosterone-inducible reporter gene, whereas R462Q-mutated RNase L does not. Based on our data we hypothesize that in 22RV1 cells, activated androgen receptor (AR) contributes to the insensitivity to IFN of the cell. Accordingly, we show that AR knockdown restores responsiveness to IFN␥. Our findings support a model in which both the activation of AR and the down-regulation of IFN signaling can synergize to promote cell survival and suppress apoptosis. This model provides the molecular basis to understand how mutated RNase L can lead to early onset PCa and illustrates how inflammatory cytokines and nuclear hormone signaling contribute to tumor development.Tumors are increasingly regarded as neoplastic organs with a specific microenvironment that comprises cells of different origins. The contribution of tumor-associated fibroblasts and endothelial cells to tumor growth is now well established (1). The role of inflammatory cells has received renewed attention with two recent reports that describe the interplay between tumor cells and tumor associated immune cells (2,3).In contrast to the contribution of inflammatory cytokines and immunoglobulins to tumor growth, T-cell-produced interferons have be shown to act as tumor suppressive cytokines (4). The recent identification of the interferonactivated ribonuclease RNase L as a candidate for the hereditary prostate cancer allele HPC1 further emphasized the role of interferon signaling in preventing tumor progression (5). Activated by 2Ј-5Ј oligoadenylates, RNase L acts as an IFN 2 -inducible tumor suppressor that stimulates apoptosis in prostate cells (6, 7).Endocrine signaling through nuclear receptors is required for the progression of a number of tumors (8). Androgen signaling affects normal prostate development and maintenance as well as prostate cancer progression. Accordingly, androgen blockade is the major therapeutic approach for prostate cancer. Up-regulation of the androgen receptor activity correlates with PCa progression and resistance from hormone blockade therapies (9, 10). Furthermore, dihydrotestosterone (DHT) has been shown to affect proliferation of breast tumor derived cells (11,12). The role of androgen receptor signaling in cancer is not fully understood. Several lines of evidence suggest that AR could promote PCa progression by inhibiting apoptosis or by promoting cell survival or proliferation (13).We describe here an intracellular cross talk between interferon and androgen signaling pathways. RNA microarrays analysis revealed that...

Androgen‐mediated cholesterol metabolism in LNCaP and PC‐3 cell lines is regulated through two different isoforms of acyl‐coenzyme A: Cholesterol Acyltransferase (ACAT)

“…There is evidence of a crosstalk between androgen and interferon signaling [45]. There are several reports on cells treated with androgens, including R1881 which show that IFN-gdependent genes are induced by the androgen treatment [46,47].…”

RNase L: Its biological roles and regulation

“…The results outline a novel role for RNase L as a regulator of translation. Another report argues that interaction between the androgen receptor and RNase L mediates a cross-talk between the IFN and androgen signaling pathways (11).…”

Identification of Anabolic Selective Androgen Receptor Modulators with Reduced Activities in Reproductive Tissues and Sebaceous Glands

“…Transactivation assays in 96-well plates used transient transfection of a modified mouse mammary tumor virus long terminal repeat promoter upstream of luciferase (MMTV-LUC) (35). This MMTV has two direct repeat copies of a consensus glucocorticoid receptor (GR) response element between positions Ϫ88 and Ϫ190; these sequences are also recognized by AR (33,36). Potencies of compounds were determined by calculating the inflection points of the sigmoidal dose response curves.…”

“…Transrepression was assessed using the pGL2 luciferase reporter containing the human matrix metalloprotease-1 (MMP-1) promoter fragment (-179 to ϩ63) (37). The reporter was transfected with rhesus AR (rhAR) into 22RV1 prostate cancer cells (33,35), and activated by pretreatment with 100 nM 12-O-tetradecanoylphorbol-13-acetate. Repression was evaluated by measuring luciferase activity.…”

“…Binding and Transcription Assays-Binding and transactivation assays were performed with human breast carcinoma cell line MDA-MB-453, which expresses endogenous AR (32)(33)(34). AR binding assays were conducted with lysates from MDA-MB-453 cells or to the ligand binding domain of rhesus monkey (rhARLBD) fused in-frame to glutathione S-transferase (GST) and expressed in yeast (35).…”