The Expression of Phospholipase C in Malignant Lymphomas

Abstract

Phosphatidylinositol-specific phospholipase C(PLC) plays a central role in transmembrane signal transduction pathways in response to the interaction between various ligands and cell-surface receptors in most eukaryotic cells. Triggered PLC catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate to yield the intracellular second messengers, diacylglycerol and inositol 1,4,5-trisphosphate. It has been found that PLC-gl is overexpressed in some cancer cells including breast, liver, and colorectal cancer, but data on the expression of PLC isozymes other than g1 have not been reported. Furthermore, there have been no reports on the expression of PLC in lymphomas. In this study, we examined the patterns of PLC isozymes expression in normal lymph node and lymph node samples from 15 patients with malignant lymphoma by western blot analysis and immunohistochemistry. The levels of PLC-131 expression were found to be similar between tumor samples and normal lymph node. PLC-132 was found to be overexpressed in 12 lymphoma samples showing, marked increase in 4 and slightly increased patterns in 8. PLC-b3 was abnormally expressed quantitatively and qualitatively in all the lymph nodes from lymphoma patients compared to the normal lymph node. PLC-33 showed a strong overexpression pattern in the lymphoma tissues, and the mobility of this protein was slightly retarded in all samples on the SDS/polyacrylamide gel. There were no detectable changes in PLC-g1 or d1 expression, but PLC-g2 overexpression was observed in 10 of 15 lymphoma samples. The fact that lymphoma tissues showed an overexpression of PLC-b2, -b3, and -g2 indicates that the alteration of the signal transduction pathway is associated with the pathogenesis of lymphoma.