A FISH study of trisomies 7 and 8 in prostate cancer

Abstract

Trisomies are products of chromosomal nondisjunction, which in turn is a manifestation of genetic instability, which has been implicated in the genesis and progression of many cancers. Specifically, we reported extensively on abnormal chromosome 8 copy number, which appears to be an ubiquitous phenomenon in many cancers. In addition to trisomy 8, trisomy 7 was also explored. In the present retrospective study, fluorescent in situ hybridization (FISH) using chromosome 7 and chromosome 8 enumeration probes (Vysis, Downer's Grove, IL) was performed on formalin-fixed, paraffin embedded materials for the purpose of studying chromosomes 7 and 8 aneuploidies. Out of a total of 56 cases studied, 33 (59%) was found to be trisomic for chromosome 7, and 4 (7%) was found to be trisomic for chromosome 8. A tumor was scored trisomic if ≥ 15% of the cells had three signals. Of the trisomic 7 cases, 4 were also trisomic for chromosome 8, and 29 were disomic for chromosome 8. Of the trisomic 8 cases, all 4 were also trisomic for chromosome 7 and none were disomic for chromosome 7. One trisomic 7 and trisomic 8 case was found to be also trisomic for chromosome 17. These data will be compared with other cytogenetic and clinicopathologic information on this cohort of patients. Thus, a subset of prostate cancer clearly exists which is characterized by chromosome 8 trisomy, which has been reported in many other cancers. However, in the present study, the small subset of trisomic 8 tumors significantly overlaps the much larger subset with abnormal chromosome 7 number. The study is ongoing. (This research was partially funded by Vysis, Inc., Downers Grove, IL).