Cytogenetic and molecular biological studies have demonstrated deletion of sequences that map to the short arm of chromosome 8 (8p) in tumors from several organ systems, including sequences that map within or near 8p22 in human prostate tumors. Recent studies in our laboratory have suggested that deletion of sequences on 8p may be concurrent with alterations in dosage for chromosome 8. In order to further investigate this finding, the present study has applied fluorescence in situ hybridization (FISH) techniques to determine the status of chromosome 8 in prostate tumors that have undergone deletion of sequences at 8p22. Dosage of 8p22 sequences was assayed utilizing unique sequence cosmid DNA probes by FISH and confirmed by amplification of microsatellite sequences by polymerase chain reaction (PCR). Chromosome 8 dosage was assayed by FISH utilizing both unique sequence cosmid probe DNA (specific to the 8q13.1-q13.3 chromosomal region) and pericentromeric probe DNA. FISH analysis of 10 specimens of normal or benign prostatic hyperplasia tissues paired with 9 tumor and one prostatic intraepithelial neoplasia tissues from the same patients for dosage at 8p, 8cen, and 8q, and PCR analysis for dosage at 8p, demonstrated that (a) FISH provided a more precise means of evaluating allelic loss than PCR in prostate tissue; (b) 8p22 sequence losses occurred frequently in prostate tumors; (c) 8p22 sequence losses were most often detected in the absence of 8cen or 8q sequence dosage alterations, although they were sometimes accompanied by gain or loss of 8cen or 8q sequences; and (d) the pattern of 8p22 sequence losses was most often widespread rather than focal. This study is the first to describe FISH analysis of interphase nuclei within tissue sections using cosmid probe DNAs.

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This work was supported in part by an institutional grant from the American Cancer Society, a grant from the Department of Veterans Affairs (J. A. M.), and funds from the Departments of Urology and Pathology, Wayne State University School of Medicine.

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