Hereditary/familial versus sporadic prostate cancer: few indisputable genetic differences and many similar clinicopathological features.

摘要

Genetic factors and their interactions with environmental conditions and internal microenvironment influence the prostate cancer (PC) development, so that gene expression couldn't strictly occur on the basis of reductionist determinisms of DNA causality but should also conform to multifactorial and stochastic events, moreover, considering the pre-RNA alternative splicing-mediated multi-protein assemblying mechanisms. Nevertheless, after age and ethnic background, the strongest epidemiological risk factor for PC is a positive family history. However, apart from RNaseL-, ElaC2-, MSR1-genes, there are not other identified high-risk genetic variants which might be considered responsible for hereditary PC, moreover suggesting that familial PC is a genetically heterogeneous disease, many gene loci rather than a specific major susceptibility gene predisposing to it. Gene-environment interactions play a crucial role in cancer development especially when low penetrance genes, such as in case of genetic polymorphisms, are the major players. Several epidemiological studies show, in some families, a possible, either syncronous or metachronous, association of other tumors (breast, brain, gastrointestinal tumors, lymphomas) with PC, thus suggesting a common genetic background. As far as the role of androgen metabolism and androgen receptor (AR)-related genes in the development of familial PC is concerned, a small number of either guanine-guanine-cytosine (< 16) or cytosine-adenine-guanine (< 18) repeats appears to increase the AR activity, resulting in a raising PC risk. Regarding the expression of both androgen and estrogen receptor-related genes in sporadic and hereditary PC, the immunohistochemistry findings show that the percentage of AR-positive cancer cells is higher in hereditary PC than in sporadic forms, whereas the mean number of estrogen-alpha-receptor-positive stromal cells is higher in sporadic PC rather than in that hereditary. As for 5-alpha-steroid-reductase-2 gene, the dinucleotide thymine-adenine repeated 18 times on the last exon, confers an increased PC predisposition, as it is mainly shown in African-American populations. Also VDR gene, that is a component of ligand (steroid)-dependent nuclear transcription factor superfamily, shows various polymorphisms which appear to be associated with PC risk. Except an earlier age of onset, no anatomo-clinical and tumor progression peculiarities between hereditary and sporadic PC have been generally identified. Indeed, tumor progression and metastasis, both in hereditary and sporadic PC, are mainly influenced by a variety of biochemical and immune-mediated tumor microenvironmental conditions rather than by the hereditary genetic factors, thus gene expression associated with invasive ability representing a newly acquired genetic variant rather than a selection of pre-existent gene abnormalities in PC cells. It's questionable whether genetic testing of unaffected men of hereditary PC families might be actually useful. Nevertheless a suitable counselling must be proposed. Family history and/or gene profiling-guided preventive strategies for men at high risk of familial PC, range from dietary to drug measures. Cancer chemopreventive approaches may include 5-alpha-reductase inhibitors, histone deacetylase inhibitors, antioxidans, non-steroidal anti-inflammatory drugs, cholesterol-lowering statins, vitamin D analogues.