Increased intracellular glycerophosphoinositol is a biochemical marker for transformation by membrane-associated and cytoplasmic oncogenes.

Transformation of rodent fibroblasts by cytoplasmic (mos, raf) and membrane-associated (ras, src, met, trk), but not nuclear (myc, fos) oncogenes results specifically in a very significant elevation of intracellular levels of glycerophosphoinositol (GPI). This elevation is specifically associated with the transformed state of the cells and not merely with their active state of proliferation. The basal phospholipase A2 (PLA2) activity of the same cells is also significantly stimulated in vivo. Our results are consistent with the notion that the elevated levels of GPI result from deacylation of lysophosphatidylinositol released by the enhanced PLA2 activity. GPI is a water-soluble, easily detectable metabolite which may constitute a convenient biochemical marker for malignant transformation by this particular group of oncogenes.