[Mechanisms of hereditary tumorigenesis]

Hereditary cancers have been shown to develop through at least two mechanisms. Development of retinoblastoma and Wilms' tumor is usually not accompanied by other hereditary symptoms. Although they are inherited autosomal dominantly, gene mutations in recessive tumor suppressor genes were found to be responsible for these tumors. The other mechanism is the enhanced mutation in the cancer-prone hereditary diseases, such as xeroderma pigmentosum, Bloom's syndrome, etc. In xeroderma pigmentosum, for example, defects in DNA repair has been shown to enhance the frequency of mutation in the oncogenes and tumor suppressor genes. Recently, another repair-related mechanism, involving the mismatch repair, was found to be involved in the hereditary nonpolyposis colon cancer.