Polymorphisms in RAS Guanyl-releasing Protein 3 are Associated with Chronic Liver Disease and Hepatocellular Carcinoma in a Korean Population

RAS guanyl-releasing protein 3 (RasGRP3), a member of the Ras subfamily of GTPases, functions as a guanosine triphosphate (GTP)/guanosine diphosphate (GDP)-regulated switch that cycles between inactive GDP- and active GTP-bound states during signal transduction. Various growth factors enhance hepatocellular carcinoma (HCC) proliferation via activation of the Ras/Raf-1/ extracellular signal-regulated kinase (ERK) pathway, which depends on RasGRP3 activation. We investigated the relationship between polymorphisms in RasGRP3 and progression of hepatitis B virus (HBV)-infected HCC in a Korean population. Nineteen RasGRP3 SNPs were genotyped in 206 patients with chronic liver disease (CLD) and 86 patients with HCC. Our results revealed that the T allele of the rs7597095 SNP and the C allele of the rs7592762 SNP increased susceptibility to HCC (OR=1.55, p=0.04 and OR=1.81~2.61, p=0.01~0.03, respectively). Moreover, patients who possessed the haplotype (ht) 1 ( A-T-C-G) or diplotype (dt) 1 ( ht1/ht1) variations had increased susceptibility to HCC (OR=1.79 ~2.78, p=0.01~0.03). In addition, we identified an association between haplotype1 (ht1) and the age of HCC onset; the age of HCC onset are earlier in ht1 +/+ than ht1 +/- or ht1 -/- (HR=0.42~0.66, p=0.006~0.015). Thus, our data suggest that RasGRP3 SNPs are significantly associated with an increased risk of developing HCC.

Inositol 5'-phosphatase, SHIP1 interacts with phospholipase C-gamma1 and modulates EGF-induced PLC activity

Phospholipase C-gamma1, containing two SH2 and one SH3 domains which participate in the interaction between signaling molecules, plays a significant role in the growth factor-induced signal transduction. However, the role of the SH domains in the growth factor-induced PLC-gamma1 regulation is unclear. By peptide-mass fingerprinting analysis, we have identified SHIP1 as the binding protein for the SH3 domain of PLC-gamma1. SHIP1 was co-immunoprecipitated with PLC-gamma1 and potentiated EGF-induced PLC-gamma1 activation. However, inositol 5'-phosphatase activity of SHIP1 was not required for the potentiation of EGF-induced PLC-gamma1 activation. Taken together, these results suggest that SHIP1 may function as an adaptor protein which can potentiate EGF-induced PLC-gamma1 activation without regards to its inositol 5'-phosphatase activity.

Effect of Phospholipase C-gamma1 Overexpression on the Protein Level of Waf1, PCNA, and Cyclin B1 Following Ultraviolet C Irradiation / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: It has been demonstrated that PLC-gamma1 is overexpressed in many tumor cells, and that overexpression of Phospholipase C (PLC)-gamma1 is associated with tumor progression. In order to understand the effect of the PLC-gamma1 overexpression on the regulation of cell cycle regulators following DNA damage, we analyzed the expression level of PCNA, cyclin B1, and p21 Waf1 after ultraviolet C (UVC) irradiation in PLC-gamma1-transfected PC12 cells. MATERIALS AND METHODS: PC12 and 3Y1 cells, transfected with empty vector or rat PLC-gamma1 cDNA, were used for this study. Following UVC irradiation, cell cycle progression was analyzed by flow cytometry and protein expression was detected by Western blotting. RESULTS: Waf1 protein was markedly down-regulated, whereas PCNA and cyclin B1 was up-regulated in PLC-gamma1 overexpressed-cells as compared to the vector transfected-cells. When the cells were irradiated with UVC, PCNA was slightly increased within 3-hours of the UV irradiation and then was markedly decreased in Vector/ PC12 cells, while it remained high until 37 hour after UVC in PLC-gamma1/PC12 cells. In contrast, cyclin B1 was gradually decreased following UVC irradiation in both cells. CONCLUSION: The overexpression of PLC-gamma1 affects the expression level of PCNA after UVC irradiation. We proposed that the overexpression of PLC-gamma1 may contribute to the UV-induced genomic instability by up-regulating the expression of PCNA.

Expression of PLC- 1 in Human Middle Ear Cholesteatoma / 대한이비인후과학회지

BACKGROUND: EGF and TGF-gamma are believed to mediate their pleiotrophic actions by binding to and activating cell surface receptors with an intrinsic protein-tyrosine kinase. Protein-tyrosine kinase phosphorylation has been considered involved in intrinsic signal transduction, proliferation and transformation of the cells. Phospholipase C-gamma1 is well characterized substrate for tyrosine kinase. OBJECTIVE: The purpose of this study is to elucidate the distribution of PLC-gamma1 in normal meatal skin and cholesteatoma matrix. MATERIALS AND METHODS: 8 cholesteatoma specimens were obtained from operated patients for immunohistochemistry and western blot analysis. RESULTS: On immunohistochemistry, PLC-gamma1 was detected only in basal layer of the deep meatal skin, but was readily detectable in both the basal and suprabasal layer in cholesteatoma matrix. By western blot analysis, considerable higher levels of PLC-gamma1 protein were detectable in cholesteatoma matrix compared with the deep meatal skin. CONCLUSION: Overexpression of PLC-gamma1 in cholesteatoma suggests a possible derangement of enhanced growth signal transduction in keratinocytes.

Alteration of Phospholipase C Activity in Human Gastric Cancer Tissues

Phospholipase C (PLC) plays a pivotal role in transmembrane signal transduction pathway for cellular proliferation differentiation and growth. Thus far, there have been few reports in which PLC activity was investigated in human malignant neoplastic tissues. In the present study, we evaluated PLC activity in 23 human gastric cancer tissues and normal mucosal tissues to investigate whether alteration of PLC activity is associated with gastric cancer. The amount of [14C] diacylglycerol, one of the earliest products of inositol phospholipid hydrolysis by PLC, was measured by thin layer chromatography. Also, expression of PLC-gamma1, which is one of the most important PLC isozymes,was examined by immunohistochemistry using specific monoclonal antibody directed against PLC-gamma1. The results are summarized as follows. PLC activity in all 23 gastric cancer tissues (1.35+/-1.04 units/mg of protein) was significantly higher than normal mucosal tissues (0.28+/-0.21 units/mg of protein) (P0.05). PLC-gamma1 immunoreactivity was detected in all of 23 cases studied. The intensity and extent of PLC-gamma1 immunoreactivity was not correlated with PLC enzyme activity, although stronger intensity was demonstrated in malignant cells in comparison to normal gland epithelial cells. The present study provides the first evidence of significant elevation of PLC activity in human stomach cancer tissues. Our results strongly suggest that PLC might be involved in tumorigenesis and/or progression(uncontrolled continuous cycling of cells) of human gastric cancer. Further studies are needed to elucidate the role of elevated PLC activity in cancer tissues.