Enzyme deficiency and tumor suppressor genes: absence of 5'-deoxy-5'-methylthioadenosine phosphorylase in human tumors

Malignant transformation is due to mutations that modify the mechanisms regulating normal cellular growth and development. These alterations include the somatic activation of cancer-promoting genes1 (cellular oncogenes) and the germline or somatic inactivation of tumor suppressor genes, also known as antioncogenes or recessive oncogenes2. While the identification of oncogenes is facilitated by their ability to transform appropriate host cells3, the search for tumor suppressor genes is remarkably complicated by the lack of strong selection procedures.