Possible role of phospholipase C in the regulation of cell division in normal and neoplastic cells.

It is proposed that a phosphatidylinositol-specific phospholipase C (PLC) enzyme may be present in abnormally high concentrations in certain cancer cells, and that the elevated activity may explain many, if not all, of the neoplastic characteristics of the cancer cells. There have thus far, been two reports in which PLC activity has been found to be elevated several fold in neoplastic cells. The products of the action of PLC on the phosphoinositides, including diglycerides and inositol phosphates, have been shown to activate the process of cell division by elevating the intracellular concentration of calcium ions and by stimulating the activity of protein kinase C. An elevated content of PLC in at least certain neoplastic cells could thus explain uncontrolled proliferative processes in those cells.