2‐Chloroethyl‐3‐sarcosinamide‐1‐nitrosourea (SarCNU) inhibits prostate carcinoma cell growth via p53‐dependent and p53‐independent pathways

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Abstract
BACKGROUND Prostate carcinoma is the most commonly occurring malignancy in men. Although 2‐chloroethyl‐3‐sarcosinamide‐1‐nitrosourea (SarCNU), an analog of the chloroethylnitrosoureas, has been used in the treatment of advanced solid tumors, the molecular mechanisms underlying the antineoplastic activity of this agent are not well understood. In the current study, the authors sought to investigate the effects of SarCNU on prostate carcinoma cell growth in vivo and in vitro. METHODS Male SCID mice underwent subcutaneous implantation (on both flanks) of human CWR‐22 and CWR‐22R prostate carcinoma xenografts. Mice were treated with either vehicle or 60 or 80 mg SarCNU per kg body weight for 5 days, with tumor growth being assessed every 3 days. Animals were sacrificed 21 days after the final injection, and tumors subsequently were collected, weighed, and processed for analysis. Immunohistochemical analyses were performed to obtain data on the localization of p53 and p21Cip1/Waf1. Cell counting, terminal deoxynucleotidyltransferase–mediated deoxyuridine triphosphate nick end‐labeling (TUNEL) assays, cell cycle analyses, Western blotting, and in vitro kinase assays were performed to determine the effects of SarCNU on growth, apoptosis, cell cycle arrest, cell cycle–regulated protein levels, and Cdc‐2 activity, respectively. RESULTS SarCNU reduced tumor incidence and inhibited the growth of CWR‐22 and CWR‐22R xenografts. In addition, treatment with this agent led to increases in p21Cip1/Waf1 levels and p53 phosphorylation at Ser15. In vitro administration of SarCNU to cells with wild‐type p53 (LNCaP and primary CWR‐22 cells) and cells with mutant p53 (PC‐3 cells) resulted in G2/M arrest and the reduction of cellular Cdc‐2 activity. Up‐regulation of p53 levels, p53 phosphorylation at Ser15, and p21Cip1/Waf1 levels in primary CWR‐22 and LNCaP cells, as well as up‐regulation of Cdc‐2 phosphorylation at Tyr15 in PC‐3 cells, was detected. CONCLUSIONS SarCNU induced G2/M arrest in prostate carcinoma cells via p53‐dependent up‐regulation of p21Cip1/Waf1 and p53‐independent phosphorylation of Cdc‐2 at Tyr15. These findings suggest a potential role for SarCNU in the treatment of prostate malignancies. Cancer 2004. © 2004 American Cancer Society.