Haploinsufficiency of 8p22 may influence cancer-specific survival in prostate cancer

Although Knudson's two-hit hypothesis with functional loss of a tumor suppressor gene has been widely accepted, accumulating evidence suggests that several genes are regulated by the quantity of their product in a dose-dependent manner (gene dosage effect). The study was designed to identify the influence of gene dosage effect of 8p22 on patient prognosis. With a median age of 71 years, 40 patients with prostate cancer (11 organ-confined, 13 capsular penetrating, and 16 nodal and/or distant metastatic) were followed for a median of 68.5 months. A fluorescence in situ hybridization (FISH) technique was applied using a region-specific cosmid probe combined with centromeric probe. Allelic losses of 8p22, 8p21.3, 8p21.1∼2, and 8p12 were found in 23, 22, 14, and 9 patients, respectively. A Cox proportional hazard model revealed that decreased fraction (i.e., the fraction of nuclei with a lesser number of cosmid signals than of centromeric probe signals) of 8p22 proved to be the sole independent prognostic factor predicting cancer-specific death, as well as disease progression-but allelic loss of 8p22 was not predictive. Cytogenetic estimation of 8p22 by FISH can yield quantitative evaluation of relevant gene dosage, which may become a useful biomolecular marker predicting poor patient prognosis.