Bioactive Sphingolipids as Major Regulators of Coronary Artery Disease

Atherosclerosis is the deposition of plaque in the main arteries. It is an inflammatory condition involving the accumulation of macrophages and various lipids (low-density lipoprotein [LDL] cholesterol, ceramide, S1P). Moreover, endothelial cells, macrophages, leukocytes, and smooth muscle cells are the major players in the atherogenic process. Sphingolipids are now emerging as important regulators in various pathophysiological processes, including the atherogenic process. Various sphingolipids exist, such as the ceramides, ceramide-1-phosphate, sphingosine, sphinganine, sphingosine-1-phosphate (S1P), sphingomyelin, and hundreds of glycosphingolipids. Among these, ceramides, glycosphingolipids, and S1P play important roles in the atherogenic processes. The atherosclerotic plaque consists of higher amounts of ceramide, glycosphingolipids, and sphingomyelin. The inhibition of the de novo ceramide biosynthesis reduces the development of atherosclerosis. S1P regulates atherogenesis via binding to the S1P receptor (S1PR). Among the five S1PRs (S1PR1-5), S1PR1 and S1PR3 mainly exert anti-atherosclerotic properties. This review mainly focuses on the effects of ceramide and S1P via the S1PR in the development of atherosclerosis. Moreover, it discusses the recent findings and potential therapeutic implications in atherosclerosis.

Bioactive Sphingolipids as Major Regulators of Coronary Artery Disease

Atherosclerosis is the deposition of plaque in the main arteries. It is an inflammatory condition involving the accumulation of macrophages and various lipids (low-density lipoprotein [LDL] cholesterol, ceramide, S1P). Moreover, endothelial cells, macrophages, leukocytes, and smooth muscle cells are the major players in the atherogenic process. Sphingolipids are now emerging as important regulators in various pathophysiological processes, including the atherogenic process. Various sphingolipids exist, such as the ceramides, ceramide-1-phosphate, sphingosine, sphinganine, sphingosine-1-phosphate (S1P), sphingomyelin, and hundreds of glycosphingolipids. Among these, ceramides, glycosphingolipids, and S1P play important roles in the atherogenic processes. The atherosclerotic plaque consists of higher amounts of ceramide, glycosphingolipids, and sphingomyelin. The inhibition of the de novo ceramide biosynthesis reduces the development of atherosclerosis. S1P regulates atherogenesis via binding to the S1P receptor (S1PR). Among the five S1PRs (S1PR1-5), S1PR1 and S1PR3 mainly exert anti-atherosclerotic properties. This review mainly focuses on the effects of ceramide and S1P via the S1PR in the development of atherosclerosis. Moreover, it discusses the recent findings and potential therapeutic implications in atherosclerosis.

Amplification of the UQCRFS1 Gene in Gastric Cancers

PURPOSE: The specific aim of this study is to unravel a DNA copy number alterations, and to search for novel genes that are associated with the development of Korean gastric cancer. MATERIALS AND METHODS: We investigated a DNA copy number changes in 23 gastric adenocarcinomas by array-comparative genomic hybridization and quantitative real-time polymerase chain reaction analyses. Besides, the expression of UQCRFS1, which shows amplification in array-CGH, was examined in 186 gastric cancer tissues by an immunohistochemistry, and in 9 gastric cancer cell lines, as well as 24 gastric cancer tissues by immunoblotting. RESULTS: We found common gains at 48 different loci, and a common loss at 19 different loci. Amplification of UQCRFS1 gene at 19q12 was found in 5 (21.7%) of the 23 gastric cancers in an array-comparative genomic hybridization and DNA copy number were increased in 5 (20.0%) out of the 25 gastric cancer in quantitative real-time polymerase chain reaction. In immunohistochemistry, the overexpression of the protein was detected in 105 (56.5%) out of the 186 gastric cancer tissues. Statistically, there was no significant relationship between the overexpression of UQCRFS1 and clinicopathologic parameters (P>0.05). In parallel, the overexpression of UQCRFS1 protein was confirmed in 6 (66.7%) of the 9 gastric cancer cell lines, and 12 (50.0%) of the 24 gastric cancer tissues by immunoblotting. CONCLUSIONS: These results suggest that the overexpression of UQCRFS1 gene may contribute to the development and/or progression of gastric cancer, and further supported that mitochondrial change may serve as a potential cancer biomarker.

Growth Differentiation Factor 5 (GDF5) Core Promoter Polymorphism Is Not Associated with Susceptibility to Osteoarthritis of the Knee in the Korean Population

BACKGROUND: Osteoarthritis (OA) is a common disease characterized by degenerating joint cartilage in the knee, hip, and hand. A functional single nucleotide polymorphism (SNP) +104T/C; rs143383 in the 5' untranslated region of the growth differentiation factor 5 (GDF5) gene was recently associated with susceptibility to OA in the Japanese and Chinese populations. METHODS: To investigate whether this association is present in the Korean population, the frequency of the polymorphism was investigated in 276 patients with knee OA and 298 healthy subjects as controls. Polymorphism analysis was performed by amplifying the core promoter region of the GDF5 gene and digesting it with the BsiEI restriction enzyme. RESULTS: The frequency of the TT, CT, and CC genotypes was 54.3% (150/276), 41.7% (115/276), and 4.0% (11/276), respectively, in patients with OA, and 53.4% (159/298), 37.9% (113/298), and 8.7% (26/298), respectively, in healthy controls. No significant differences in genotypic or allelic frequencies of the +104T/C SNP of the GDF5 gene were observed between patients with OA and controls. Also, no significant differences in allelic and genotypic frequencies were found when the individuals were stratified by age and gender. CONCLUSIONS: The results suggest that the +104T/C; rs143383 GDF5 core promoter polymorphism is not a risk factor for OA in the Korean population.

Genetic and Expression Analysis of the SIRT1 Gene in Gastric Cancers

PURPOSE: Silent mating-type information regulation 2 homologue 1 (SIRT1) is a nicotinamide adenine dinucleotide-dependent deacetylase. SIRT1 plays an important role in the regulation of cell death/survival and stress response in mammals. The aim of this study was to investigate whether the SIRT1 gene is involved in the development or progression of gastric cancers. MATERIALS AND METHODS: SIRT1 and p53 genes in 86 gastric cancers were examined for genetic alterations by PCR-single strand conformation polymorphism sequencing, as well as SIRT1 protein expression in 170 gastric cancers by immunohistochemistry. RESULTS: In the genetic analysis, we found SIRT1 and p53 mutations in two and 12 cases, respectively. Two missense mutations, c.599 C>T (T200I) and c.1258 G>A (E420K), were detected in the SIRT1 gene coding region. The SIRT1 and p53 mutation were found in mutually exclusive gastric cancers. The immunohistochemistry revealed that SIRT1 overexpression was found in 95 (55.9%) of 170 gastric cancers. Altered SIRT1 expression was not statistically associated with clinicopathological parameters, including tumor differentiation, location, lymph node metastasis, or p53 expression. Two cases with an SIRT1 mutation showed increased SIRT1 expression. CONCLUSIONS: These results suggest that genetic alterations and overexpression of the SIRT1 gene may contribute to gastric cancer development.

An Association of C/T Polymorphism in the TFF1 Gene and the Susceptibility to Gastric Cancer

PURPOSE: This study investigated whether a single nucleotide polymorphism (SNP) located at position -2 in the Kozak sequence of the TFF1 gene is associated with H. pylori infection and the development of gastric cancer in Koreans. MATERIALS AND METHODS: We enrolled 167 patients with gastric cancer from January 2000 to December 2003 and also 299 healthy controls during the same period. The genotype of the TFF1 SNP was analyzed by polymerase chain reaction-restriction fragment length polymorphism and single strand conformation polymorphism. We also examined the H. pylori infection by Giemsa staining. RESULTS: No significant difference in the allele or the TFF1 SNP genotype frequency was observed between the patients with gastric cancer and the control subjects (P=0.595 and P=0.715, respectively). When stratified by the histological subtype of gastric cancer and the age of the patients, the risk was not statistically significant between the two study groups (P=0.088 and P=0.551, respectively). H. pylori infection was detected in 39 cases and it was not associated with the TFF1 genotype. CONCLUSION: These findings suggest that this TFF1 gene polymorphism is not associated with H. pylori infection and gastric cancer in Koreans and so it doesn't contribute to the susceptibility to gastric cancer in Koreans.

Expression Pattern of EphB2 in Gastric Cancer

PURPOSE: The EphB2 receptor, a member of the receptor tyrosine kinase family, is a target gene of the Wnt signaling pathway and may achieve a tumor suppressor function through regulation of cell growth and migration. Our aim was to determine whether an altered expression of EphB2 might be associated with gastric cancer development and, if so, to determine to which pathologic parameter it is linked. MATERIALS AND METHODS: For the construction of the gastric cancer tissue microarray, 83 paraffin-embedded tissues containing gastric cancer areas were cored 3 times and transferred to the recipient master block. The expression patterns of EphB2 were examined on tissue microarray slides by using immunohistochemistry and were compared using pathologic parameters, including histological type, depth of invasion, lymph node metastatsis, and peritoneal dissemination. RESULTS: The EphB2 protein was expressed in the normal gastric mucosal epithelium, especially in the bottom of the mucosa. We found loss of EphB2 expression in 30 (36.1%) of the 83 gastric cancer tissues. Statistically, loss of EphB2 expression was more common in gastric cancer with lymph-node metastasis. There was no significant correlation between EphB2 expression and depth of invasion, histologic type, or peritoneal dissemination. CONCLUSION: Our findings suggest that loss of EphB2 expression may represent a critical step in gastric carcinogenesis.

Genetic and expression analysis of the KCNRG gene in hepatocellular carcinomas

The potassium channels are ubiquitous multisubunit membrane proteins, and potassium-dependent alterations in the membrane potential play an important role in the proliferation of many types of cells. This study analyzed the mutation, allelic loss and expression patterns of the KCNRG gene in 77 HCCs in order to determine if the KCNRG gene, which encodes the potassium channel regulating protein, is involved in the tumorigenesis of hepatocellular carcinoma (HCC). One KCNRG missense mutation, CGT->CAT (Arg->His) was found at codon 92 within the T1 domain. Hep3B hepatoma cells were transfected with the wild- or mutant-KCNRG to determine the effect of this mutation in KCNRG. Interestingly, the suppressive cell growth activity of the mutant-type KCNRG was significantly lower than that of the wild-type KCNRG. In addition, allelic loss was detected in 17 out of 64 (26.5%) informative HCC cases, and all were hepatitis B virus (HBV)-positive. Moreover, the allelic loss was closely related to an intrahepatic metastasis (P=0.0247), higher grade (P=0.0078) and clinical stage (P=0.0071). Expression analysis revealed 22 tumor tissues to have a loss of expression of the KCNRG transcript. These results suggest that genetic alterations and the expression of KCNRG might play an important role in the development and/or progression of a subset of HCCs.

Hypermethylation of the RUNX3 gene in hepatocellular carcinoma

Methylation events play a critical role in various cellular processes including regulation of gene transcription and proliferation. Recently, RUNX3 gene, one of TGF-beta-Smads signaling transduction pathway genes, showed strong tumor-suppressor activity by regulation of epithelial proliferation and apoptosis. To elucidate the potential etiological role of the RUNX3 gene in the development of hepatocellular carcinoma (HCC), we have analyzed the methylation status of 5' CpG island of the RUNX3 gene in a series of 73 HCC tissues and 11 liver cell lines. Expectedly, promoter methylation of RUNX3 gene was found in 2 (2.7%) of 73 corresponding normal liver, whereas 30 (41.1%) of 73 HCCs and 4 (40%) of 10 liver cancer cell lines showed hypermethylation of the gene, respectively. There was no significant difference between promoter hypermethylaion and clinicopathologic parameters of primary HCC samples, including histologic grade, microvascular invasion, and clinical stage. Interestingly, demethylating agent 5-aza-2-deoxycytidine induced reactivation and more potent expression of RUNX3 gene in HCC cell lines. Our findings indicate that promoter hypermethylation of RUNX3 gene may occur as an early event in the development of HCC and that methylation may be a major mechanism for inactivation of RUNX3 gene in HCC.

Expression Pattern of KLF4 in Korean Gastric Cancers

PURPOSE: KLF4, a member of the KLF family, is a zinc finger tumor suppressor protein that is critical for gastric epithelial homeostasis. Our aim was to determine whether the altered expression of KLF4 might be associated with gastric cancer development and, if so, to determine to which pathologic parameter it is linked. MATERIALS AND METHODS: For the construction of the gastric cancer tissue microarray, 84 paraffin-embedded tissues containing gastric cancer areas were cored 3 times and transferred to the recipient master block. The expression pattern of KLF4 was examined on tissue microarray slides by using immunohistochemistry and was compared with pathologic parameters, including histologic type, depth of invasion, lymph node metastasis, and peritoneal dissemination. RESULTS: The KLF4 protein was expressed in cytoplasm and nucleus of superficial and foveolar epithelial cells in the normal gastric mucosa. We found markedly reduced or loss of KLF4 expression in 43 (51.2%) of the 84 gastric cancer tissues. There was no significant correlation between KLF4 expression and pathologic parameters, including histologic type, depth of invasion, lymph node metastasis and peritoneal dissemination. CONCLUSION: Our findings suggest that altered expression of KLF4 may contribute to abnormal regulation of gastrointestinal epithelial cell growth and differentiation and to the development of Korean gastric cancer, as an early event.