Overexpression of phosphoinositide-specific phospholipase Cgamma in NIH 3T3 cells promotes transformation and tumorigenicity.

Phosphoinositide-specific phospholipase Cg (PLCg) is a key regulatory enzyme that binds to the phosphoryl-tyrosine residues in the cytoplasmic domain of certain activated receptors and catalyses the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] forming IP3 and diacylglycerol (DAG) in response to several mitogenic factors. Previously, we determined that microinjected PLCg induces DNA synthesis in G0-arrested NIH 3T3 cells, suggesting the possibility that PLCg may have an oncogenic potential. In this report, we demonstrate that overexpression of PLCg in NIH 3T3 cells results in altered growth properties and cellular transformation. The PLCg/3T3 transfectants do not require serum growth factors to proliferate, display anchorage-independent growth in soft agar and induce tumors when transplanted into nude mice. These findings suggest that overexpression of PLCg facilitates the transformation of NIH 3T3 cells. Furthermore, PLCg expression and activity have been shown to be elevated in many human tumors. Thus, PLCg signaling may contribute to the promotion and/or progression of human cancers.