摘要
Carcinogenesis is a multi-stage process.This process may involve both genetic and epi-genetic events. Analyses of the involvement ofgenetic events (mutations in the global sensewhich include point mutations, deletions, trans-locations and rearrangements of genetic mate-rial) in carcinogenesis have implicated twomajor classes of genes, oncogenes and onco-suppressor genes. Oncogenes, a term first usedby Huebner and Todaro, are derived by muta-tion of normal cellular genes, protooncogenes.More than 40 oncogenes have now been isolatedand found to encode proteins with diverse bio-chemical functions.