The antiandrogen cyproterone acetate induces synthesis of transforming growth factor ?1 in the parenchymal cells of the liver accompanied by an enhanced sensitivity to undergo apoptosis and necrosis without inflammation

Abstract

Recently, cases of liver damage and liver tumors have been reported after treatment of prostate cancer patients with the antiandrogen cyproterone acetate (CPA). In rat liver, CPA initiates a wave of DNA synthesis that is accompanied by apoptosis. In apoptotic hepatocytes, a latent form of transforming growth factor beta 1 (TGF-beta 1) is detectable by immunohistochemistry. Injection of a single dose of TGF-beta 1 induces apoptosis in the liver of animals pretreated with CPA but has an insignificant effect in untreated animals. In this study, we show by Northern analysis that there is increased expression of TGF-beta 1 in the liver after CPA treatment. Detection of TGF-beta 1 with in situ hybridization showed that TGF-beta 1 was synthesized in the parenchymal cells. Time course and dose-response experiments performed 48 hours after the last application of CPA showed that apoptotic nuclei with chromatin condensed at the nuclear periphery (AN) were already visible 2 hours after injection (0.13%), and apoptotic bodies (ABs) increased 2 to 9 hours after the injection (from 1.28% to 6.67%) after 25 micrograms TGF-beta 1/kg. At 4.5 hours after injection, an induction of apoptosis could be detected with 0.25 microgram TGF-beta 1/kg and after the maximum dose (250 micrograms TGF-beta 1/kg) ANs (0.24%) and ABs (16.74%) were homogeneously distributed throughout the liver lobe. Irrespective of the dose or time after injection of TGF-beta 1, 82% of the ABs were localized within hepatocytes. Liver enzymes were detected in high amounts in the serum (eightfold elevation of glutamate dehydrogenase, fivefold elevation of alanine transaminase [ALT]) 7 hours after the first visible sign of apoptosis. After an additional 20 hours, the liver contained many necrotic figures. These results suggest that the combination of TGF-beta 1 expression coupled with a strikingly enhanced sensitivity to the induction of apoptosis could be responsible both for the liver damage and the development of liver tumors observed after treatment with CPA.

Levels of transforming growth factor β and transforming growth factor β receptors in rat liver during growth, regression by apoptosis and neoplasia

“…29 In situ hybridization studies demonstrated that 7 hours after the last CPA treatment a high percentage of hepatocytes expressed TGF-β 1 mRNA around the central venules, whereas 41 hours later, TGF-β 1 producing hepatocytes showed no preferential localization. 32 Almost all hepatocytes preparing for apoptosis showed positive immunostaining for the TGF-β 1 precursor protein. 31 Subsequently, also in primary hepatocyte cultures, latent TGF-β 1 was predominantly found in hepatocytes which displayed an apoptotic morphology.…”

“…46 Previously 2,500 ng or 25,000 ng of active TGF-β 1 /100 g of body weight were administered iv 48 hours after CPA withdrawal. 22,32 Assuming at least 83% uptake into the liver and a liver weight of 6 g/100 g body weight, 1 g of liver tissue was loaded with at least 350 ng or 3,500 ng of exogenous TGF-β 1 . That resulted in 2.7-or 11-fold elevated apoptotic activity, 48 hours after CPA withdrawal.…”

“…31 In situ hybridization revealed that 7 and 41 hours after the last CPA treatment, a considerable percentage of hepatocytes express TGF-β 1 mRNA. 32 TGF-β is synthesized not only in the liver but also in many extrahepatic tissues, including blood platelets, in relatively large amounts. 33 Also carcinoma of various organs produce and release TGF-β protein to the serum in an endocrine fashion resulting in high plasma concentrations.…”

Hepatocyte death following transforming growth factor-β1 addition

“…Initial observations have indicated that within 2 h following injection of a single dose of 25 pg TGF-plkg body weight, all stages of apoptosis were visible (Oberhammer et al, 1996). In our earlier studies on cell death in primary rat hepatocytes, we found that apoptosis was maximal within 30-48 h after addition of TGF-P1 (Oberhammer et al, 1991(Oberhammer et al, , 1992.…”

“…In studies to be reported elsewhere, Northern blot analysis demonstrated that treatment of the liver with the anti-hormone alone was sufficient to induce expression of TGF-p1 mRNA. In situ hybridization hrther revealed that TGF-pl was synthesized by the parenchymal cells with a high percentage of hepatocytes expressing TGF-p1 mRNA (Oberhammer et al, 1996). It is well established that TGF-p1 is able to inhibit epithelial growth in vivo.…”