TRPM‐2 gene expression in normal rat ventral prostate following castration and exposure to diethylstilbestrol, flutamide, MK‐906 (finasteride), and coumarin

Abstract

TRPM-2, not normally expressed in the rat ventral prostate, has been identified as an important genetic marker of castration-induced apoptotic cell death. It is not known whether other agents capable of causing growth inhibition of the rat ventral prostate also induce TRPM-2 expression. To investigate this further, 270 mature Sprague-Dawley rats were randomized into one of six groups: control, castration, diethylstilbestrol (DES), flutamide, MK-906 (finasteride), or coumarin. Five rats per group were sacrificed on days 1, 3, 5, 7, 10, and 21. Serum testosterone, body weights, and prostate weights were determined at each time point. The ventral prostate was removed and cellular RNA extracted. Northern blot analysis using cDNA probes for TRPM-2 and gamma-actin were performed at each time point. Only DES significantly decreased rat weights. DES and castration reduced serum testosterone to undetectable levels by the next day. Flutamide caused a 3.0- to 4.5-fold increase in serum testosterone above control. Coumarin and MK-906 did not affect serum testosterone levels. DES and castration reduced prostate weights to 20% and 6% of control, respectively, while inducing TRPM-2 expression to a maximum on day 5 of the experiment. DES induced TRPM-2 expression over a longer duration than did castration, suggesting that more than just the decrease of serum testosterone to castrate levels plays a role in the expression of TRPM-2. MK-906, coumarin, and flutamide reduced prostatic weights to a lesser extent (50%, 63%, 71% of control, respectively), but these agents did not induce TRPM-2 expression at any time during the experiment. TRPM-2 expression in the rat ventral prostate does not correlate simply with catabolic effects on the prostate.

Relative potency of testosterone and dihydrotestosterone in preventing atrophy and apoptosis in the prostate of the castrated rat.

“…Expression of TRPM-2 increases with androgen withdrawal (13,14) and has been used extensively as a marker of apoptotic activity in the prostate (13,(15)(16)(17). TRPM-2 mRNA for the intraprostatic dose responses was quantified using slot blots (Fig.…”

“…The effect on the prostate of finasteride and other 5␣-reductase inhibitors is a high degree of cell atrophy with minimal evidence of cell loss. Finasteride administration does not result in upregulation of TRPM-2 mRNA in the prostates of treated rats (6,7,16), although there was an increase in TRPM-2 protein using another 5␣-reductase inhibitor (3). Inhibition of apoptosis occurs at an intraprostatic testosterone concentration ‫ف(‬ 10 ng/g tissue) approximately half that seen with finasteride treatment and a DHT concentration half that of a normal intact rat.…”

Nuclear clusterin/XIP8, an x-ray-induced Ku70-binding protein that signals cell death

“…The association between Ku70 and CLU͞XIP8 may correlate with the pathophysiology of CLU͞XIP8-related diseases and provides a useful clinical or environmental marker of IR, renal, or heart injury. The association of clu͞xip8 expression with apoptosis (i.e., TRPM-2, a marker for apoptosis) was first made when clu͞xip8 was identified and cloned as the major mRNA species induced during regression of the rat ventral prostate after castration (23). The association of this protein with apoptosis was confirmed in many other biological systems (19,22).…”

Roles of clusterin in progression, chemoresistance and metastasis of human ovarian cancer

“…26 However, different opinions of the possible pro-and antiapoptotic activities for this protein and the ability of alternative splicing of its transcript to code for different isoforms prompted a meticulous series of different isoforms studies to assess the precise impact of CLU on apoptosis. Here, comparing with wild-type parental SKOV3 cells, SKOV3-CLU F and SKOV3-CLU T , in which the CLU protein constantly localized in the cytoplasm, showed no obvious changes in cellular growth.…”