ABSTRACT
Regulatory T (Treg) cells are important to induce and maintain immunological self-tolerance. Although the progress accomplished in understanding the functional mechanism of Treg cells, intracellular molecules that control the mechanisms of their suppressive capacity are still on investigation. The present study showed that peroxisome proliferator-activated receptor-alpha deficiency impaired the suppressive activity of Treg cells on CD4+CD25- and CD8+ T cell proliferation. In Treg cells, PPARα gene deletion also induced a decrease of migratory abilities, and downregulated the expression of chemokine receptors (CCR-4, CCR-8 and CXCR-4) and p27KIP1 mRNA. Treg cells from PPARα-/- mice also lost their anergic property. Since low Treg activity, as observed in PPARα-/- mice, is known to be associated with the inhibition of tumor growth, we inoculated these mice with B16 melanoma cells and assessed tumor proliferation. In PPARα-/- mice, cancer growth was significantly curtailed, and it was correlated with high expression of granzyme B and perforin mRNA in tumor bed. Degranulation of cytolytic molecules by CD8+ T cells, assessed by a perforin-release marker CD107a expression, was higher in PPARα-/- mice than that in wild-type mice. Tumor-infiltrating lymphocytes (TIL) in melanoma tumors in PPARα-/- mice exhibited high pro-inflammatory Th1 phenotype. Consistently, adoptive transfer into lymphopenic RAG2-/- mice of total PPARα-/-splenic T cells inhibited more the growth rate of B16 tumor than the wild type splenic T cells. Our findings suggest that PPARα deficiency, by diminishing Treg cell functions and upregulating pro-inflammatory T cell phenotype, exerts an in vivo anti-cancer properties.
Subject(s)
Melanoma, Experimental/genetics , PPAR alpha/genetics , T-Lymphocytes, Regulatory/metabolism , Tumor Burden/genetics , Animals , Cell Line, Tumor , Cell Movement/genetics , Cell Proliferation/genetics , Cells, Cultured , Clonal Anergy/genetics , DNA-Binding Proteins/deficiency , DNA-Binding Proteins/genetics , Gene Expression Regulation, Neoplastic , Immunotherapy, Adoptive/methods , Male , Melanoma, Experimental/pathology , Melanoma, Experimental/therapy , Mice, Inbred C57BL , Mice, Knockout , PPAR alpha/deficiency , Receptors, Chemokine/genetics , Receptors, Chemokine/metabolism , Reverse Transcriptase Polymerase Chain Reaction , T-Lymphocyte Subsets/metabolismABSTRACT
To investigate the effect of nitric oxide on tumor development, we established a rat tumor xenograft model in zebrafish embryos. The injected tumor cells formed masses in which nitric oxide production could be detected by the use of the cell-permeant DAF-FM-DA (diaminofluorophore 4-amino-5-methylamino-2'-7'-difluorofluorescein diacetate) and DAR-4M-AM (diaminorhodamine-4M). This method revealed that nitric oxide production could be co-localized with the tumor xenograft in 46% of the embryos. In 85% of these embryos, tumors were vascularized and blood vessels were observed on day 4 post injection. Furthermore, we demonstrated by qRT-PCR that the transplanted glioma cells highly expressed Nos2, Vegfa and Cyclin D1 mRNA. In the xenografted embryos we also found increased zebrafish vegfa expression. Glioma and zebrafish derived Vegfa and tumor Cyclin D1 expression could be down regulated by the nitric oxide scavenger 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide or CPTIO. We conclude that even if there is a heterogeneous nitric oxide production by the xenografted glioma cells that impacts Vegfa and Cyclin D1 expression levels, our results suggest that reduction of nitric oxide levels by nitric oxide scavenging could be an efficient approach to treat glioma.
Subject(s)
Gene Expression Regulation, Neoplastic/physiology , Glioma/metabolism , Nitric Oxide/metabolism , Vascular Endothelial Growth Factor A/metabolism , Analysis of Variance , Animals , Benzoates/pharmacology , Cyclin D1/metabolism , Flow Cytometry , Heterografts , Histological Techniques , Imidazoles/pharmacology , Rats , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , ZebrafishABSTRACT
Nonaspanins constitute a family of proteins, also called TM9SF, characterized by a large non-cytoplasmic domain and nine putative transmembrane domains. This family is highly conserved through evolution and comprises three members in Saccharomyces cerevisiae, Dictyostelium discoideum, and Drosophila melanogaster, and four members are reported in mammals (TM9SF1-TM9SF4). Genetic studies in Dictyostelium and Drosophila have shown that TM9SF members are required for adhesion and phagocytosis in innate immune response, furthermore, human TM9SF1 plays a role in the regulation of autophagy and human TM9SF4 in tumor cannibalism. Here we report that the zebrafish genome encodes five members of this family, TM9SF1-TM9SF5, which show high level of sequence conservation with the previously reported members. Expression analysis in zebrafish showed that all members are maternally expressed and continue to be present throughout embryogenesis to adults. Gene expression could not be regulated by pathogen-associated molecular patterns such as LPS, CpG, or Poly I:C. By bioinformatic analyses of 80 TM9SF protein sequences from yeast, plants, and animals, we confirmed a very conserved protein structure. An evolutionary conserved immunoreceptor tyrosine-based inhibition motif has been detected in the cytoplasmic domain between transmembrane domain (TM) 7 and TM8 in TM9SF1, TM9SF2, TM9SF4 and TM9SF5, and at the extreme C-terminal end of TM9SF4. Finally, a conserved TRAF2 binding domain could also be predicted in the cytoplasmic regions of TM9SF2, TM9SF3, TM9SF4, and TM9SF5. This confirms the hypothesis that TM9SF proteins may play a regulatory role in a specific and ancient cellular mechanism that is involved in innate immunity.
