Gene expression levels of ß4-galactosyltransferase 5 correlate with the tumorigenic potentials of B16-F10 mouse melanoma cells.

Our previous studies showed that mouse ß4-galactosyltransferase 5 (ß4GalT5) is a lactosylceramide (Lac-Cer) synthase, and that its gene expression increases by 2- to 3-fold upon malignant transformation of cells. In the present study, we examined whether or not the tumorigenic and metastatic potentials of B16-F10 mouse melanoma cells can be suppressed by reducing the expression of the ß4GalT5 gene. We isolated a stable clone named E5 whose ß4GalT5 gene expression level was reduced to 35% that of a control clone C1 by transfection of its antisense cDNA. Thin-layer chromatography analysis of glycosphingolipids showed that the amounts of Lac-Cer and ganglioside GM3 are significantly less in clone E5 than in clone C1. Clone C1 and E5 cells were each transplanted subcutaneously or injected intravenously into C57BL/6 mice, and the sizes of tumors and numbers of colonies formed in the lungs were determined. The average tumor size and average number of colonies formed with clone E5 were decreased to 44 and 49%, respectively, of those formed with clone C1. Furthermore, the numbers and sizes of colonies formed in the soft agarose gels, and the volumes of tumors formed in athymic mice with fibroblasts from wild type, heterozygous and homozygous ß4GalT5-knockout mouse embryos upon transformation with the polyoma virus oncogene correlated with the ß4GalT5 gene dosage. These results strongly indicate that the amounts of Lac-Cer synthesized by ß4GalT5 correlate with the tumorigenic potentials of malignantly transformed cells.

Protein kinase C theta plays a fundamental role in different types of chronic colitis.

BACKGROUND & AIMS: Dysregulated host/microbial interactions induce the development of colitis by activating deleterious acquired immune responses. Activation of CD4(+) T cells is mainly induced through signaling machinery associated with immunologic synapse (IS). A key molecule associated with the IS is protein kinase C (PKC) theta. However, the role of PKCtheta in the pathogenesis of colitis has not fully been defined. METHODS: The role of PKCtheta for the acquired-immune responses involved in the development of different types of colitis (CD45RB model, T-cell receptor [TCR] alpha knockout [KO] mice and interleukin [IL]-2KO mice) was examined by generating double KO mice and by utilizing cell transfer approaches. RESULTS: Adoptive transfer of PKCtheta-deficient naïve CD4(+) T cells failed to induce T helper cell (Th) 1-mediated colitis in the immune-deficient host (CD45RB model). Development of Th2-mediated colitis in TCRalphaKO mice was also inhibited by the absence of PKCtheta. In IL-2KO mice, which develop colitis because of dysregulated T-cell homeostasis, deficiency of PKCtheta in CD4(+) T cells failed to induce the development of severe colitis. Interestingly, absence of PKCtheta led to a remarkable decrease in the proliferation, but not apoptosis, of colonic memory CD4(+) T cells. This impaired proliferation resulted in a marked decrease in the colonic CD4(+) T cells that are capable of producing IL-17. In addition, deficiency of PKCtheta inhibited the production of Th2 cytokines by colonic CD4(+) T cells. CONCLUSIONS: PKCtheta serves as a common and fundamental signaling molecule in the development of different types of colitis and may represent an attractive target for treating inflammatory bowel disease.

Dependence of intestinal granuloma formation on unique myeloid DC-like cells.

Granulomas represent a localized inflammatory reaction that is characteristically observed in many inflammatory conditions. However, the mechanisms of granuloma formation have not been fully defined. Herein we demonstrate, by using experimental models of intestinal inflammation, that a unique CD11c+ DC-like cell subset that exhibits phenotypic and functional features of immature myeloid DCs and is characterized by the expression of a macrophage marker (F4/80) produces large amounts of IL-23 and directly induces the development of granulomas under a Th1-predominant intestinal inflammatory condition. Importantly, both IL-4 and IgG contribute to the suppression of F4/80+ DC-like cell-mediated granuloma formation by regulating the function and differentiation of this cell subset. In addition, enteric flora is required for the F4/80+ DC-like cell-mediated granuloma formation. Collectively, our data provide what we believe are novel insights into the involvement of F4/80+ DC-like cells in intestinal granuloma formation and demonstrate the role of host (IL-4 and IgG) and environmental (enteric flora) factors that regulate this function.