Expression of phospholiapse C isozymes in human lung cancer tissues / 결핵

BACKGROUND: Phospholipase C (PLC) plays an important role in cellular signal transduction and is thought to be critical in cellular growth, differentiation and transformation of certain malignancies. Two second messengers produced from the enzymatic action of PLC are diacylglycerol(DAG) and lnositol 1, 4, 5-trisphosphate(IP3). These two second messengers are important in down stream signal activation of protein kinase C and intracelluar calcium elevation. In addition, functional domains of the PLC isozymes, such as Src homology 2(SH2) domain, Src homology 3(SH3) domain, and pleckstrin homology(PH) domain play crucial roles in protein translocation, lipid membrane modification and intracellular memrane trafficking which occur during various mitogenic processes. We have previously reported the presence of PLC-γ1, γ2, β1, β3, and δ1 isozymes in normal human lung tissue and tyrosine-kinase-independent activation of phospholipase C-γisozymes by tau protein and AHNAK. We had also found that the expression of AHNAK protein was markedly increased in various histologic types of lung cancer tissues as compared to the normal lungs. However, the report concerning expression of various PLC isozymes in lung cancers and other lung diseases is lacking. Therefore, in this study we examined the expression of PLC isozymes in the paired surgical specimens taken from lung cancer patients. METHODS: Surgically resected lung cancer tissue samples taken from thirty seven patients and their paired normal control lungs from the same patients. The expression of various PLC isozymes were studied. Western bolt analysis of the tissue extracts for the PLC isozymes and immunohistochemistry was performed on typical samples for localization of the isozyme. RESULTS: In 16 of 18 squamous cell carcinomas, the expression of PLC-γ1 was increased. PLC-γ1 was also found to be increased in all of 15 adenocarcinoma patients. In most of the non-small cell lung cancer tissues we had examined, expression of PLC-δ1 was decreased. However, the expression of PLC-δ1 was markedly increased in 3 adenocarcinomas and 3 squamous carcinomas. Although the numbers were small, in all 4 cases of small cell lung cancer tissues, the expression of PLC-δ1 was nearly absent. CONCLUSION: We found increased expression of PLC-γ1 isozyme in lung cancer tissues. Results of this study, taken together with our earlier findings of AHNAK protein-a putative PLD-γ, activator-over-expression, and the changes observed in PLC-δ1 in primary human lung cancers may provide a possible insight into the derranged calcium-inositol signaling pathways leading to the lung malignancies.

Increased Expression of Phospholipase C-gamma1 Activator Protein, AHNAK in Human Lung Cancer Tissues / 결핵

BACKGROUND: Phospholipase C(PLC) plays a central role in cellular signal transduction and is important in cellular growth, differentiation and transformation. There are currently ten known mammalian isozymes of PLC reported to this date. Hydrolysis of phosphatidylinositol 4,5-bisphosphate(PIP2) by PLC produces two important second messengers, inositol 1,4,5-trisphosphate(IP3) and diacylglycerol. PLC-gamma1, previously, was known to be activated mainly through growth factor receptor tyrosine kinase. Other mechanisms of activating PLC-gamma1 have been reported such as activation through tau protein in the presence of arachidonic acid in bovine brain and activation by IP3, phosphatidic acid, etc. Very recently, another PLC-gamma1 activator protein such as tau has been found in bovine lung tissue, which now is considered to be AHNAK protein. But there has been no report concerning AHNAK and its associated disease to this date. In this study, we examined the expression of the PLC-gamma1 activator, AHNAK, in lung cancer specimens and their paired normal. METHODS: From surgically resected human lung cancer tissues taken from twenty-eight patients and their paired normal counterparts, we evaluated expression level of AHNAK protein using immunoblot analysis of total tissue extract. Immunohistochemical stain was performed with primary antibody against AHNAK protein. RESULTS: Twenty-two among twenty-eight lung cancer tissues showed over expression of AHNAK protein(eight of fourteen squamous cell lung cancers, all of fourteen adenocarcinomal). the resulting bands were multiple ranging from 70 to 200 kDa in molecular weight and each band was indistinct and formed a smear, reflecting mobility shift mainly due to proteolysis during extraction process. On immunohistochemistry, lung cancer tissues showed a very heavy, dense staining with anti-AHNAK protein antibody as compared to the surrounding normal lung tissue, coresponding well with the results of the western blot. CONCLUSION: The overexpression of PLC-gamma1 activator protein, AHNAK in lung cancer may provide evidence that the AHNAK protein and PLC-gamma1 act in concerted manner in carcinogenesis.