Immunohistochemical and molecular biological study on expression of diacylglycrol kinase in human origined malignant tumor cells from head and neck

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Diacylglycerol (DG) is one of the important second messengers, which serves as an activator of protein kinase C (PKC). DG kinase (DGK) phosphorylates DG to generate phosphatidic acid, thus DGK is considered to be a regulator of PKC activity through attenuation of DG. Recent studies have revealed molecular structures of several DGK isozymes from mammalian species, and showed that most of the isozymes are expressed ih the brain in various amounts. Five DGK isozyme cDNA have been cloned from rat brain library (DGKα, -β, -γ, -ζ, -ι) in Department of Anatomy and cell biology, Yamagata University School of medicine. mRNA expressions of DGK isozymes in rat brain have been studied by in situ hybridization histochemistry, but their mRNA expressions in human malignant tumor cells, especially epithelial cells, have not been examined. In this study, we examined the mRNA expression of DGK isozymes in human squamous cell carcinoma cell lines. To study the localization and functional role of DGKζ, we generated the specific antibody against rat DGKζ and examined the specificity of the antibody. Furthermore, human malignant tumor cell has been cultured with DGK inhibitors and it was revealed that DGK inhibitor might suppress cell growth. It shows that DGK may have some relations to the molecular mechanism of cell growth.