The genetic basis of cancer.

Cancer is essentially a genetic disease resulting from congenital or acquired alterations in some cells of the patient. Such changes may occur in particular oncogenes and are responsible for the tumour phenotype of the affected population of cells. Oncogenes function by continuous positive action in the mitogenic pathway, and may become activated by point mutations, chromosomal rearrangements, gene amplification or viral insertion events. In contrast, unaltered tumour-suppressor genes are responsible for suppressing the neoplastic phenotype, and their inactivation by deletion or mutation permits cancerous development in the affected cells. The genetic model of carcinogenesis is thus based on the idea that mutations at the DNA level create a functional imbalance between the oncogenes and the tumour-suppressor genes, resulting in uncontrolled clonal proliferation. It is likely that the clinical importance of these recent findings will soon be realised and utilised in the development of therapies and diagnostic procedures that will directly benefit the patient.