Activation of Oncogenes by Chemical Carcinogens

Increasing evidence suggests that a small set of cellular genes appear to be targets for genetic alterations that contribute to the neoplastic transformation of cells. These genes, termed protooncogenes, appear to play a crucial role in normal cellular growth or differentiation since they are highly conserved in nature, being detected in species as divergent as yeast, Drosophila, and humans. Recent identification of a number of these genes as encoding for putative growth factors (sis,hst, int-2), growth factor receptors (neu, erb B, fms), proteins involved in the regulation of transmembrane signal transduction (ras), nuclear regulatory proteins (myc, myb, fos, jun), tyrosine kinases (src) and serine/threonine kinases (raf, mos) has served to substantiate this idea.