Keisuke Ishii

Large-scale search of SNPs for type 2 DM susceptibility genes in a Japanese population☆

The etiology of type 2 diabetes (DM) is polygenic. We investigated here genes and polymorphisms that associate with DM in the Japanese population. Single-nucleotide polymorphisms (SNPs) of 398 derived from 120 candidate genes were examined for association with DM in a population-based case-control study. The study group consisted of 148 cases and 227 controls recruited from Funagata, Japan. No evident subpopulation structure was detected for the tested population. The association tests were conducted with standard allele positivity tables (chi(2) tests) between SNP genotype frequency and case-control status. The independent association of the SNPs from serum triglyceride levels and body mass index was examined by multiple logistic regression analysis. A value of P<0.01 was accepted as statistically significant. Six genes (met proto-oncogene, ATP-binding cassette transporter A1, fatty acid binding protein 2, LDL receptor defect C complementing, aldolase B, and sulfonylurea receptor) were shown to be associated with DM.

Large-scale investigation of genomic markers for severe periodontitis

The purpose of the present study was to investigate the genomic markers for periodontitis, using large-scale single-nucleotide polymorphism (SNP) association studies comparing healthy volunteers and patients with periodontitis. Genomic DNA was obtained from 19 healthy volunteers and 22 patients with severe periodontitis, all of whom were Japanese. The subjects were genotyped at 637 SNPs in 244 genes on a large scale, using the TaqMan polymerase chain reaction (PCR) system. Statistically significant differences in allele and genotype frequencies were analyzed with Fisher’s exact test. We found statistically significant differences (P < 0.01) between the healthy volunteers and patients with severe periodontitis in the following genes; gonadotropin-releasing hormone 1 (GNRH1), phosphatidylinositol 3-kinase regulatory 1 (PIK3R1), dipeptidylpeptidase 4 (DPP4), fibrinogen-like 2 (FGL2), and calcitonin receptor (CALCR). These results suggest that SNPs in the GNRH1, PIK3R1, DPP4, FGL2, and CALCR genes are genomic markers for severe periodontitis. Our findings indicate the necessity of analyzing SNPs in genes on a large scale (i.e., genome-wide approach), to identify genomic markers for periodontitis.

Identification and Characterization of the X-Dimer of Human P-Cadherin: Implications for Homophilic Cell Adhesion

Cell adhesion mediated by cadherins depends critically on the homophilic trans-dimerization of cadherin monomers from apposing cells, generating the so-called strand-swap dimer (ss-dimer). Recent evidence indicates that the ss-dimer is preceded by an intermediate species known as the X-dimer. Until now, the stabilized form of the X-dimer had only been observed in E-cadherin among the classical type I cadherins. Herein, we report the isolation and characterization of the analogous X-dimer of human P-cadherin. Small-angle X-ray scattering (SAXS) and site-directed mutagenesis data indicates that the overall architecture of the X-dimer of human P-cadherin is similar to that of E-cadherin. The X-dimerization is triggered by Ca(2+) and governed by specific protein-protein interactions. The attachment of three molecules of Ca(2+) with high affinity (Kd = 9 μM) stabilizes the monomeric conformation of P-cadherin (ΔTm = 17 °C). The Ca(2+)-stabilized monomer subsequently dimerizes in the X-configuration by establishing protein-protein interactions that require the first two extracellular domains of the cadherin. The homophilic X-dimerization is very specific, as the presence of the highly homologous E-cadherin does not interfere with the self-recognition of P-cadherin. These data suggest that the X-dimer could play a key role in the specific cell-cell adhesion mediated by human P-cadherin.

Abstract 2428: PPMX-2017: Antibody against CDH3 with potent efficacy against lung cancer

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Cadherin 3/P-cadherin (CDH3) is a member of cadherin family proteins involved in the cell-cell adhesion. Based on a genome-wide cDNA microarray analysis of pancreatic cancer, we found that CDH3 is overexpressed in pancreatic cancer. We also confirmed by our immunohistochemistry study that CDH3 protein was expressed highly in pancreatic, lung, colon and other types of cancer tissues but not in normal tissues. Since CDH3 is a transmembrane glycoprotein and overexpressed in cancer tissues, it is an attractive therapeutic target for various kinds of cancer. In this present study, we generated a series of monoclonal antibodies against CDH3 and evaluated their anti-tumor effect both in vitro and in vivo. PPMX2017, an antibody from the series, is an anti-human CDH3 specific mouse IgG2a antibody. The in vitro studies demonstrated that PPMX2017 elicited strong antibody dependent cellular cytotoxicity (ADCC) activity on CDH3-positive cancer cell lines (lung cancer: NCI-H358 and A431, pancreatic cancer: KLM1 and Bxpc3.). Furthermore, PPMX2017 showed a significant antitumor effect in a therapeutic xenograft model of lung cancer where NCI-H358 cell-generated tumors grew to 70∼90 mm3 before administration of this antibody. PPMX2017 suppressed tumor growth by 60∼80% compared with control IgG in a dose range of 0.3mg∼5mg/kg. These findings show that CDH3 is a potential target for cancer therapy and PPMX2017 is a candidate for the development of antibody therapeutics. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2428.