Immunological milieu in the peritoneal cavity at laparotomy for gastric cancer

AIM： To investigate the immunological repertoire in the peritoneal cavity of gastric cancer patients. METHODS： The peritoneal cavity is a compartment in which immunological host-tumor interactions can occur. However, the role of lymphocytes in the peri- toneal cavity of gastric cancer patients is unclear. We observed 64 patients who underwent gastrectomy for gastric cancer and 11 patients who underwent lapa-roscopic cholecystectomy for gallstones and acted as controls. Lymphocytes isolated from both peripheral blood and peritoneal lavage were analyzed for surface markers of lymphocytes and their cytokine production by flow cytometry. CD4＋CD25h＋gh T cells isolated from the patient＇s peripheral blood were co-cultivated for 4 d with the intra-peritoneal lymphocytes, and a cytokine assay was performed. RESULTS： At gastrectomy, CCR7-CD45RA- CD8＋ effector memory T cells were observed in the peritoneal cavity. The frequency of CD4＋ CD25 h＋ghT ceils in both the peripheral blood and peritoneal cavity was elevated in patients at advanced stage [control vs stage IV in the peripheral blood： 6.89 （3.39-10.4） vs 15.34 （11.37-19.31）, P 〈 0.05, control vs stage IV in the peri- toneal cavity： 8.65 （5.28-12.0） vs 19.56 （14.81-24.32）, P 〈 0.05]. On the other hand, the suppression was restored with CD4＋ CD25h＋QhT cells from their own pe- ripheral blood. This study is the first to analyze lympho- cyte and cytokine production in the peritoneal cavity in patients with gastric cancer. Immune regulation at ad- vanced stage is reversible at the point of gastrectomy. CONCLUSION： The immunological milieu in the peri- toneal cavity of patients with advanced gastric cancer elicited a Th2 response even at gastrectomy, but this response was reversible.

A novel animal model for in vivo study of liver cancer metastasis

AIM:To establish an animal model with human hepatocyte-repopulated liver for the study of liver cancer metastasis.METHODS:Cell transplantation into mouse livers was conducted using alpha-fetoprotein(AFP)-producing hu-man gastric cancer cells(h-GCCs) and h-hepatocytes as donor cells in a transgenic mouse line expressing urokinase-type plasminogen activator(uPA) driven by the albumin enhancer/promoter crossed with a severe combined immunodeficient(SCID) mouse line(uPA/SCID mice).Host mice were divided into two groups(A and B).Group A mice were transplanted with h-GCCs alone,and group B mice were transplanted with h-GCCs and h-hepatocytes together.The replacement index(RI),which is the ratio of transplanted h-GCCs and h-hepatocytes that occupy the examined area of a histological section,was estimated by measuring h-AFP and h-albumin concentrations in sera,respectively,as well as by immunohistochemical analyses of h-AFP and human cytokeratin 18 in histological sections.RESULTS:The h-GCCs successfully engrafted,repopulated,and colonized the livers of mice in group A(RI = 22.0% ± 2.6%).These mice had moderately differentiated adenocarcinomatous lesions with disrupted glandular structures,which is a characteristics feature of gastric cancers.The serum h-AFP level reached 211.0 ± 142.2 g/mL(range,7.1-324.2 g/mL).In group B mice,the h-GCCs and h-hepatocytes independently engrafted,repopulated the host liver,and developed colonies(RI = 12.0% ± 6.8% and 66.0% ± 12.3%,respectively).h-GCC colonies also showed typical adenocarcinomatous glandular structures around the h-hepatocyte-colonies.These mice survived for the full 56 day-study and did not exhibit any metastasis of h-GCCs in the extrahepatic regions during the observational period.The mice with an h-hepatocyte-repopulated liver possessed metastasized h-GCCs and therefore could be a useful humanized liver animal model for studying liver cancer metastasis in vivo.CONCLUSION:A novel animal model of human liver cancer metastasis was established using the uPA/SCID mouse line.This model could be useful for in vivo testing of anti-cancer drugs and for studying the mechanisms of human liver cancer metastasis.