Comparative genomic hybridization, allelic imbalance, and fluorescence in situ hybridization on chromosome 8 in prostate cancer

Abstract

Due to problems with primary tumor cell culture, conventional cytogenetics has yielded little insightful information on chromosomal alterations in prostate cancer. The primary aim of this study was to define the ability of comparative genomic hybridization (CGH) to detect and map genetic deletions in prostate tumors. A secondary aim was to apply multiple assays to individual tumors as a means of deciphering the mechanisms of genetic alterations in prostate cancer. CGH results were compared with allelic imbalance measurements at 29 distinct loci on chromosome 8 in 18 specimens (17 malignant and 1 benign). CGH detected no changes in cases where all informative PCR/RFLP loci were retained and detected all p arm deletions consisting of at least two loci. We estimate that in this study, the smallest deletions detected by CGH were approximately 20-30 cM. Physical mapping of subchromosomal arm deletions by CGH correlated well with allelic imbalance mapping by PCR/RFLP: The data agreed at 88% of loci on 8p and 92% of loci on 8q. Fluorescence in situ hybridization (FISH) with multiple centromere probes and DNA content flow cytometry (FCM) also was performed on selected specimens. FISH revealed two cases of chromosome 8 aneusomy. In these two cases and three others, CGH showed simultaneous p arm deletion and q arm gain, suggesting isochromosome 8q formation. Together, these data suggested that, simple chromosomal aberrations were responsible for allelic losses on 8p and allelic gains on 8q in a significant number of prostate tumors. We also used CGH to examine relative DNA sequence copy number throughout the genome. Changes frequently associated with 8p loss include gains of 8q and losses of 13q, 16p, 16q, 17p, 17q, 20q, and Y. Cases with 8p loss exhibited five times the number of alterations as did cases without 8p loss.

Identification of two distinct deleted regions on chromosome 13 in prostate cancer

“…We have found 50% of prostate tumors showing LOH at one or more 13q markers and no correlation between 13q LOH and DNA ploidy, indicating 13q deletion to be an early, non-random, and independent chromosomal alteration. The frequently deleted region on 13q in these 36 prostate cancers was in agreement with the lost region detected by previous CGH analyses (Cher et al, 1994;Visakorpi et al, 1995). However, in the LOH mapping (Figure 2), two independent smallest regions of overlapping deletions were further de®ned.…”

Molecular cytogenetics of bone and soft tissue tumors

“…The CGH technique provides informa tion not only on the overall ocurrence of amplifications, but also on the extent of the regions affected [51,[53][54][55], The results obtained are instrum ental in the ultimate id en ti fication and isolation of the genes involved.…”

“…glioma [53,63], nor has it previously been associated w ith the developm ent of hum an sarcomas. Conceivably, the Iq21-q22 region may harbor a gene(s) im portant for h u m an bone and soft tissue tum or initiation and/or progression.…”

Loss of p53 and c-myc Overrepresentation in Stage T2-3N1-3M0 Prostate Cancer are Potential Markers for Cancer Progression

“…For example, frequent allelic loss of the LPL gene (8p22) in prostate cancer suggests that a tumor suppressor gene (or genes) is located in this region (7)(8)(9)(10)(11). Likewise, the c-myc gene (8q24) is commonly overrepresented or amplified in advanced and recurrent prostate cancer, suggesting that amplification of this oncogene (or a neighboring gene) may be critical for the progression of this cancer (12)(13)(14). We have recently shown that concurrent overrepresentation of c-myc and loss of LPL independently predicts a poor overall survival and progression-free survival in men with stage pT 3 N 0 M 0 prostate cancer (15).…”