An elaborate circuitry of biochemical reactions mediates the proliferation and differentiation of mammalian cells.

     We have gained access to this circuitry through the study of genes implicated in the genesis of human cancer, "proto-oncogenes", which suffer genetic damage in cancer cells leading to an unwanted gain of function.

Proto-oncogenes serve as accelerators leading the cell into relentless cell division. Many of the proteins encoded by proto-oncogenes serve as relays in the biochemical pathways that transmit signals from the surface of the cell to the nucleus. Several of the genes encode protein kinases that phosphorylate proteins on tyrosine residues.

The understanding of how these molecules participate in various signal transduction pathways to control such biological processes as cellular proliferation and differentiation are essential for us to fully understand the biochemical maladies of cancer.