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The loss or mutational inactivation of the RB1 tumor suppressor gene has been implicated in the development of a diverse group of human malignancies. However, the contribution of the RB1 gene alteration to human prostatic carcinogenesis has been poorly understood. Thus far, deletion of the promoter sequence and exon 21 from one primary tumor specimen and the alterations found in the cell line DU-145, are the only cases of RB1 mutations reported in human carcinoma of the prostate. This study was designed to determine whether alterations in the structure or expression of the RB1 gene occur in human prostate carcinoma, and to determine the nature of these changes and the frequency with which they occur. One hundred twelve primary prostate tumor tissues and four metastatic lesions were obtained immediately after surgical resection. The RB1 gene was characterized in 68 tumor DNA samples using Southern analysis and the PG3.8M or H3-8 probes. Band profiles were analyzed by scanning densitometry. Sixty-three tumor DNA samples were analyzed for defects in the RB1 promoter using polymerase chain reaction (PCR) and heteroduplex analysis. Alterations in the expression of exons 1-27 were analyzed in 79 primary and four metastatic tumor RNAs using RT-PCR. Three of 68 tumors were identified to have gross rearrangement of the RB1 gene or deletion of one allele. One of four stage D tumor specimens showed truncated RT-PCR products indicating an internal deletion of RB1 transcripts. In all, 14 of 83 (17%) specimens displayed abnormally low levels of RB1 mRNA expression. Furthermore, these alterations of RB1 expression showed a correlation with increasing tumor stage and grade. These results suggest alterations of RB1 mRNA expression occur more frequently in higher stages and grades of prostate cancer and, thus, may be contributing to the malignant progression of a subset of human prostate cancer.

The human sex-region Y (SRY) gene maps to Yp 11.3 and encodes a protein that shares significant sequence homology with a conserved DNA binding motif found in the nonhistone high-mobility group (HMG) proteins. In the mouse, Sry is required for normal testicular development and is expressed in the developing male gonadal ridge as well as in the adult testis. In man, SRY expression has been observed in the adult testis, but not in other adult male tissues. We have analyzed samples from human prostate adenocarcinoma and benign prostatic hypertrophy (BPH) for the expression of the SRY gene. We found expression of SRY in 60% of malignant prostate tumors and in three of six samples of BPH. We did not find expression in male or female colon mucosa, or in tissue from a cystic ovary. Malignant and atrophic testicular tissue both contained SRY transcript and served as positive controls in these experiments. We also found SRY transcript in the DU-145 prostate adenocarcinoma cell line. Interestingly, SRY expression is absent in the Tera-2 teratocarcinoma cell line. The potential for the SRY gene product to bind HMG core response elements in vitro suggests that SRY could participate in the cascade of gene regulatory events that result in aberrant cell growth or malignancy. © 1993 Wiley-Liss, Inc.