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 stimulationon 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^stimulatedhumanmononuclear 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-g production by MNC, although E. coli LPS did induce production of both significantly. Nevertheless, interleukin-12 stimulation restored the IFN-g^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-g^mediated cellular immunity of MNC. H. pylori infection might thereby promote proliferation and progression of gastric cancers.

BACKGROUND Interleukin‐18 (IL‐18), a recently described cytokine produced mainly by macrophages, stimulates interferon‐γ (IFN‐γ) production by natural killer cells and T cells. Although it has been reported that serum IL‐18 levels are higher in patients with advanced tuberculosis and acute graft‐versus‐host disease compared with normal controls, the authors found no reports regarding serum IL‐18 levels in patients with malignant solid tumors. The purpose of this study was to determine serum IL‐18 levels and their clinical significance in patients with gastric carcinoma. METHODS Peripheral blood samples were obtained from 94 patients with gastric carcinoma who underwent curative surgery and from 50 healthy volunteers. The serum IL‐18 level, the IFN‐γ, level, and the Helicobacter pylori (HP) serology status were determined in each sample with an enzyme‐linked immunosorbent assay. RESULTS The mean serum IL‐18 level for all patients was significantly higher compared with the mean level in healthy volunteers (P < 0.01). IFN‐γ titers were below the level of detection in all samples tested. When the patients were subdivided into groups, it was found that the serum IL‐18 level in patients with Stage II and III disease was significantly higher compared with the level found in healthy volunteers (P < 0.01). The serum IL‐18 level decreased after patients underwent surgical resection. However, there was no significant difference in the serum IL‐18 level between healthy controls and patients with Stage I or IV disease. Patients with IL‐18 levels ≥ 310 pg/mL (i.e., equal to or greater than the mean levels ± 1 standard deviation in the healthy volunteers) experienced a significantly lower survival rate compared with patients who had IL‐18 levels < 310 pg/mL after undergoing surgery (P < 0.05) despite a lack of any discernible difference in clinicopathologic factors between the two groups. The serum IL‐18 level was identified as an independent postoperative prognostic factor in multivariate survival analysis using a Cox proportional hazards model (hazard ratio, 4.89; P = 0.01). There was no significant correlation between HP serology status and serum IL‐18 levels. CONCLUSIONS The preoperative serum IL‐18 level may represent a significant postoperative prognostic determinant in patients with gastric carcinoma. Its function in the host immune system remains to be elucidated. Cancer 2001;92:2050–5. © 2001 American Cancer Society.

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The level of serum CCL5, a C-C chemokine, is reportedly correlated with tumor progression in several cancers. We herein investigated the mechanisms by which CCL5 might contribute to tumor progression in gastric cancer. Serum CCL5 levels significantly correlated with tumor progression and prognosis in patients with gastric cancer. Immunohistochemistry showed that tumor-infiltrating lymphocytes expressed CCL5, while the tumor cells expressed the CCL5 receptors. Fluorescent double staining showed that tumor-infiltrating CD41 cells rather than CD81 cells preferentially expressed CCL5. Using gastric cancer cell lines (MKN45, KATO III), we examined CCL5 production by coculturing whole peripheral blood mononuclear cells (PBMCs), CD41 cells, or CD81 cells, with tumor cells. CD41 cells cocultured with tumor cells remarkably enhanced CCL5 production in a direct cell-cell contact manner over other cocultured PBMCs, including CD81 cells. Gastric cancer cell lines expressed CCL5 receptors and augmented their proliferation in response to CCL5 stimulation. Furthermore, we examined the effect of CCL5-treated cancer cells on the cocultured PBMCs, focusing on the CD41/CD81 proportion and apoptosis. Coculture of CCL5-treated gastric cancer cells with PBMCs resulted in a significant decrease in the proportion of CD81 cells but not CD41 cells, suggesting Fas-FasL-mediated apoptosis in CD81 cells. In immunodeficient mice coinjected with KATO III and PBMCs, neutralization of CCL5 significantly suppressed tumor progression, resulting in a favorable outcome. In conclusion, gastric cancer cells might thus induce CD41 T cells to secrete CCL5 and exploit it for their progression, as well as to aid in the prevention of CD81 T cell-involved tumor elimination.

The classification of lymph node metastasis based on the number of positive nodes has been adopted in the International Union Against Cancer/American Joint Committee on Cancer (UICC/AJCC) TNM classification of gastric carcinoma. However, the N classification (for condition of the regional lymph nodes) would be underestimated when the number of examined nodes were too small. To determine the minimum number of lymph nodes to examine for a correct classification, we analyzed 926 patients undergoing curative resection for gastric carcinoma. The number of metastatic lymph nodes correlated significantly with the number of examined lymph nodes. The pN0 patients with 10 to 14 examined nodes showed a significantly higher survival rate than did those with 5 to 9 examined nodes, and they had as good a prognosis as those with 15 or more examined nodes. In the pN1 and pN2 categories, patients with 29 or fewer examined nodes tended toward lower survival rates than did patients with 30 or more examined nodes. Among the patients who were classified as stage IA, the survival rate for those with 5 to 9 examined nodes was significantly lower than that for patients with 30 or more examined nodes. Among the patients classified as stage III, those with 10 to 19 examined nodes and those with 20 to 29 examined nodes had lower survival rates than did patients with 30 or more examined nodes. In conclusion, the minimum number of lymph nodes examined for a correct pN0 classification can be reduced from 15 to 10. For pN1-3 classifications, 20 or more nodes should be examined, and examining 30 or more lymph nodes may be desirable.