Takashi Ichikura

Expression of cyclooxygenase-2 protein in gastric adenocarcinoma

Epidemiological studies have suggested that the regular use of nonsteroidal antiinflammatory drugs, which inhibit cyclooxygenase (COX), reduces the risk of colon cancer. The inducible COX‐2 isoform has been reported to be upregulated in colorectal carcinomas and may play a role in colorectal carcinogenesis. The purpose of this study was to investigate the expression of COX‐2 protein in human gastric adenocarcinomas.

Sentinel node concept in gastric carcinoma.

To assess the applicability of thesentinel node concept to gastric carcinoma. The location of metastaticlymph nodes was analyzed retrospectively in 119 patients with gastriccarcinoma in whom metastasis was limited to one or two nodes.Intraoperative lymphatic mapping was attempted in 62 patients usingindocyanine green injected endoscopically into the gastric submucosaadjacent to the tumor. Metastatic lymph nodes were distributed beyondthe perigastric area in 4% of patients with a single node involved.The positive node was located along the greater curvature in 21% ofthe patients with a tumor on the lesser curvature. Two patients had ametastatic node totally occupied by cancer tissue. In 16% of patientswith two nodes involved, a positive node was located on both the lesserand greater curvatures. Lymphatic mapping was successful in allsubjects. A larger number and wider distribution of green-stained nodeswere observed in patients injected with 8 ml of indocyanine greensolution than in those injected with 4 ml. No metastasis was observedin any nodes in 47 (96%) of the 49 patients who had no metastasis ingreen nodes. In one patient showing metastasis in non-green nodeswithout metastasis in green nodes, the positive nodes were totallyoccupied by cancer tissue. Our results showed the complexity oflymphatic streams within and from the stomach. Lymphatic mapping usingindocyanine green can be a tool for identifying sentinel nodes ingastric carcinoma although lymph nodes occupied by cancer tissue maynot be detected by this technique.

Screening of DNA copy‐number aberrations in gastric cancer cell lines by array‐based comparative genomic hybridization

We performed genome‐wide screening for deoxyribonucleic acid copy‐number aberrations in 31 gastric cancer (GC) cell lines by using custom‐made comparative genomic hybridization (CGH)‐array. Copy‐number gains were frequently detected at 1q, 3q, 5p, 7p, 7q, 8q, 11q, 17q, 20p, 20q, Xp and Xq, and losses at 3p, 4p, 4q, 8p, 9p, 18p and 18q. With respect to histological subtypes, copy‐number gains at 1p, 16p, 20p, 20q and 22q, and losses at 8p, 10p, 10q and 18q were significantly frequent in cell lines derived from tumors of the well‐differentiated type, whereas copy‐number gains at 1q, 7p, 7q, Xp and Xq were frequent in the undifferentiated type. Homozygous deletions were seen at five loci, whereas high‐level amplifications were detected in 15 of the 31 GC cell lines; these had occurred at 24 loci, including the segment containing CDK6 (7q21.2). Amplification of that gene had never been reported in GC before. Immunohistochemical studies showed increased levels of CDK6 protein in 54 of the 292 primary GC samples we examined (18.5%). Cytoplasmic localization of CDK6, as well as CDK6 over‐expression, was more frequent in well‐differentiated GC than in undifferentiated tumors. Nuclear expression of CDK6 was more frequent in early stage GC than in advanced tumors, suggesting that nuclear localization of CDK6 is likely to be a prognostic factor for GC. Taken together, our data indicate that CDK6 might be involved in the pathogenesis of GC and, more generally, that CGH‐arrays have a powerful potential for identifying novel cancer‐related genetic changes in a variety of tumors. (Cancer Sci 2005; 96: 100–110)

Expression of cyclooxygenase-2 in human gastric adenomas and adenocarcinomas.

The increased expression of cyclooxygenase (COX)‐2 has been implicated in the development and progression of colorectal cancer. We sought to determine the involvement of COX‐2 in human gastric cancer.

Limited Gastrectomy With Dissection of Sentinel Node Stations for Early Gastric Cancer With Negative Sentinel Node Biopsy

Objective:To evaluate the early results of sentinel node (SN)-navigated limited surgery for early gastric cancer. Summary Background Data:False-negative results of SN biopsy cannot be ignored in gastric cancer surgery. Previous studies suggest that dissection of lymph node stations where SNs belong (SN stations) may minimize the possibility of leaving metastasis behind in SN-navigated surgery. Methods:Patients with T1N0M0 gastric cancer <4 cm were informed about the SN-navigated limited surgery from 2003 to 2008. SNs were identified using radioisotope and dye methods. When the SN biopsy by frozen section was negative, limited gastrectomy with dissection of SN stations was performed. Patients with SN stations limited to either the lesser or greater curvature underwent a wedge resection unless it would cause a strong deformity of the stomach. A sleeve gastrectomy was performed in other cases. Results:Six of the 60 enrolled patients chose a standard gastrectomy. Sixteen patients were excluded after laparotomy due to a T2–T3 tumor or tumor location. Three patients with positive SN biopsy underwent D2 gastrectomy, and 35 with negative SN biopsy underwent limited gastrectomy with dissection of SN stations; wedge resection in 8 and sleeve gastrectomy in 27. There were no operative mortalities or morbidities. All patients undergoing the limited surgery had no lymph node metastasis by postoperative pathology, and survived without any recurrence. The average area of the resected stomach for limited surgery was significantly smaller than that for standard procedures (92 ± 50 vs. 189 ± 64 cm2, P < 0.001). Conclusions:SN-navigated limited gastrectomy with dissection of SN stations for T1N0M0 gastric cancer was considered safe and acceptable although long-term follow-up is mandatory.

ADAM23, a possible tumor suppressor gene, is frequently silenced in gastric cancers by homozygous deletion or aberrant promoter hypermethylation

Array-based comparative genomic hybridization (CGH-array) has a powerful potential for high-throughput identification of genetic aberrations in cell genomes. We identified a homozygous loss of ADAM23 (2q33.3) in the course of a program to screen a panel of gastric cancer (GC) cell lines (1/32, 3.1%) for genomic copy-number aberrations using our custom-made CGH-array. Infrequent homozygous deletion of ADAM23 was also seen in primary gastric tumors (1/39, 2.6%). ADAM23 mRNA was expressed in normal stomach tissue, but not in the majority of GC cell lines without homozygous deletion of this gene. Expression of ADAM23 mRNA was restored to gene-silenced GC cells after treatment with 5-aza 2′-deoxycytidine. The methylation status of the ADAM23 CpG island, which showed promoter activity, correlated inversely with its expression. Methylation of this CpG island was observed both in GC cell lines and in primary GC tissues; in primary tumors with a hypermethylated CpG island, expression of ADAM23 was lower than in adjacent noncancerous tissues. Moreover, restoration of ADAM23 in GC cells reduced their numbers in colony-formation assays. These results suggest that genetic or epigenetic silencing by hypermethylation of the ADAM23 CpG-rich promoter region leads to loss of ADAM23 function, which may be a factor in gastric carcinogenesis.

Helicobacter pylori Augments Growth of Gastric Cancers via the Lipopolysaccharide-Toll-like Receptor 4 Pathway whereas Its Lipopolysaccharide Attenuates Antitumor Activities of Human Mononuclear Cells

Purpose:Helicobacter pylori is reportedly involved in the development of gastric cancer. We investigated the mechanisms by which H. pylori affects gastric cancer growth and antitumor immunities in the host, focusing on H. pylori–derived lipopolysaccharide (LPS). Experimental Design:H. pylori and four gastric cancer cell lines (MKN28, MKN45, NUGC3, and KATOIII) were used. We examined the effect of H. pylori or its LPS stimulation on cancer growth and the involvement of the H. pylori LPS-toll-like receptor 4 (TLR4) pathway. We also examined the cytotoxicities of H. pylori/LPS–stimulated human mononuclear cells (MNC) against gastric cancer cells and the effect of H. pylori LPS stimulation on cytokine production by MNC. Results:H. pylori, as well as its LPS, augmented the growth of gastric cancers, all of which expressed TLR4. Neutralization of TLR4 almost completely abrogated the H. pylori–induced proliferative activity of cancer cells. Escherichia coli LPS also augmented cancer growth via the LPS-TLR4 pathway. However, only H. pylori–derived LPS attenuated the cytotoxicity of MNC against gastric cancer cells. Stimulation with H. pylori/LPS also down-regulated perforin production in cancer cell–cocultured CD56+ natural killer cells. H. pylori LPS induced neither interleukin-12 nor IFN-γ production by MNC, although E. coli LPS did induce production of both significantly. Nevertheless, interleukin-12 stimulation restored the IFN-γ–producing capacity of H. pylori LPS–stimulated MNC. Conclusion:H. pylori augmented the growth of gastric cancers via the LPS-TLR4 pathway, whereas it attenuated the antitumor activity and IFN-γ–mediated cellular immunity of MNC. H. pylori infection might thereby promote proliferation and progression of gastric cancers.

A proposal for diagnostically meaningful criteria to classify increased epidermal growth factor receptor and c-erbB-2 gene copy numbers in gastric carcinoma, based on correlation of fluorescence in situ hybridization and immunohistochemical measurements

Amplification of the epidermal growth factor receptor (EGFR) and/or c-erbB-2 oncogenes and overexpression of their proteins are detected in 30% of gastric carcinomas, but there are few reports regarding the correlation between gene amplification and protein overexpression. We examined the correlation between amplification of the EGFR and c-erbB-2 genes, detected using fluorescence in situ hybridization, and overexpression of their proteins, detected using immunohistochemistry, in formalin-fixed tissue sections of 54 surgically resected gastric carcinomas. A mean EGFR copy number per nucleus of four or more and an EGFR/chromosome 7 centromere (CEP7) ratio of 1.7 or more were each detected in 4 specimens (7%). The sensitivity and specificity of both criteria for EGFR protein overexpression were 75% and 92%, respectively. A mean c-erbB-2 copy number per nucleus of 7.0 or more and a c-erbB-2/chromosome 17 centromere (CEP17) ratio of 2.0 or more were detected in six (11%) and eight (15%) specimens, respectively. The sensitivity and specificity of the former criterion to c-erbB-2 overexpression were 83% and 98%, respectively, while those of the latter were 63% and 98%. A mean EGFR gene copy number of 4.0 or more and/or an EGFR/CEP7 ratio of 1.7 and a mean c-erbB-2 gene copy number of 7.0 or more and/or a c-erbB-2/CEP17 ratio of 2.0 or more would be useful in defining increased EGFR and c-erbB-2 gene copy numbers, respectively, in gastric carcinomas.

Impact of Postoperative Infection on Long-Term Survival After Potentially Curative Resection for Gastric Cancer

We focused on the impact of postoperative infection on long-term survival after potentially curative resection for gastric cancer. Postoperative surgical and medical complications have been implicated as a negative predictor of long-term outcome in various malignancies. However, there have been no published reports assessing the impact of complications arising from postoperative infection on survival in gastric cancer. We studied a population of 1,332 patients who underwent curative resection for gastric cancer. These patients were divided into two groups based on the occurrence (141 patients, 10.6%) or absence (1,191 patients, 89.4%) of postoperative complications due to infection. We investigated the demographic and clinicopathological features of each patient with and without postoperative complications from infection, and thereby the impact of postoperative infection on long-term survival. Patients with postoperative infection had significantly higher frequency of males, upper side tumor location, and total gastrectomy as a surgical procedure, more advanced stage of gastric cancer, and greater age compared with those without postoperative infection. Patients with complications due to postoperative infection had significantly more unfavorable outcome compared with those patients without postoperative infection. Multivariate analysis demonstrated that age, preoperative comorbidity, blood transfusion, tumor depth, nodal involvement, and postoperative infection correlated with overall survival. We conclude that postoperative complications from infection are a predictor of adverse clinical outcome in patients with gastric cancer. However, further immunological study and prospective trials are necessary to confirm the biological significance of these findings.

SKI and MEL1 Cooperate to Inhibit Transforming Growth Factor-β Signal in Gastric Cancer Cells

Chromosomal amplification occurs frequently in solid tumors and is associated with poor prognosis. Several reports demonstrated the cooperative effects of oncogenic factors in the same amplicon during cancer development. However, the functional correlation between the factors remains unclear. Transforming growth factor (TGF)-β signaling plays important roles in cytostasis and normal epithelium differentiation, and alterations in TGF-β signaling have been identified in many malignancies. Here, we demonstrated that transcriptional co-repressors of TGF-β signaling, SKI and MDS1/EVI1-like gene 1 (MEL1), were aberrantly expressed in MKN28 gastric cancer cells by chromosomal co-amplification of 1p36.32. SKI and MEL1 knockdown synergistically restored TGF-β responsiveness in MKN28 cells and reduced tumor growth in vivo. MEL1 interacted with SKI and inhibited TGF-β signaling by stabilizing the inactive Smad3-SKI complex on the promoter of TGF-β target genes. These findings reveal a novel mechanism where distinct transcriptional co-repressors are co-amplified and functionally interact, and provide molecular targets for gastric cancer treatment.