[Malignant testicular tumors: cytogenetic and molecular biology principles].

The common cytogenetic finding characteristic of human malignant testicular germ-cell tumors is the presence of an isochromosome of the short arm of chromosome 12, i(12p), suggesting alterations in the proto-oncogenes (e.g., c-Ki-ras2) or putative tumor suppressor genes (TSG) that are localized here. However, to date there is no proof for such alterations. Conversely, alterations in expression of the retinoblastoma gene, a classical TSG, have been reported for the majority of testicular tumors. Other molecular genetic alterations have been described, affecting genes that are involved in the normal regulation of spermiogenesis, such as the c-kit gene product and its ligand SCF, as well as hst1, which is normally expressed in embryonal tissues only. The well-documented sensitivity of testicular tumors to chemotherapeutic agents may be caused by decreased activity of the glutathione S-transferase detoxification enzymes, as well as alterations of the expression of this gene family.