Unknown,Transcriptomics,Genomics,Proteomics

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Apoptosis-regulated low avidity cancer-specific CD8+ T cells can be rescued to eliminate HER-2/neu expressing tumors by costimulatory agonists in tolerized mice

ABSTRACT: A major barrier of vaccines as cancer treatment is their failure to activate and maintain a complete cancer-specific CD8+ effector T cell repertoire. Low avidity T cells are more likely to escape clonal deletion in the thymus when compared to higher avidity T cells, and therefore comprise the major population of effector T cells available for activation in cancer patients. However, low avidity T cells fail to traffic into the tumor microenvironment and function in eradicating tumor under optimal vaccination conditions as opposed to higher avidity T cells that escape clonal deletion and do function in tumor killing. We utilized high and low avidity TCR transgenic CD8+ T cells specific for the immunodominant epitope of HER-2/neu (RNEU420-429) to identify signaling pathways responsible for the inferior activity of low avidity T cells. Adoptive transfer of these cells into tumor-bearing vaccinated mice identified members of apoptosis pathways as being upregulated in low avidity T cells. The increased expression of pro-apoptotic proteins by low avidity T cells promoted their own cell death and also that of other tumor-specific CD8+ T cells within their local environment. Importantly, this pro-apoptotic effect was overcome using a strong costimulatory signal that prevents activation-induced cell death and enables low avidity T cells to traffic into the tumor and assist in tumor clearance. These findings identify new therapeutic opportunities for activating the most potent anticancer T cell responses. High and low avidity T cells were isolated from TCR transgenic mice and adoptively transferred into Cy-treated, vaccinated, neu-N mice. Three days after adoptive transfer T cells were isolated from the tumor draining nodes and RNA was extracted for gene expression analysis.

ORGANISM(S): Mus musculus

SUBMITTER: Elizabeth Jaffee

PROVIDER: E-GEOD-54020 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The goal of this study was to examine differences in gene expression of tumor specific CD8 T cells in an in vivo tumor mouse model after inhibition of galectin-3 protein expression by genetic knockout. Galectin-3 is thought to modulate CD8 T cell response by cross-linking cell surface glycoproteins Galectin-3 is a 31 kD carbohydrate-binding lectin that is over-expressed by many human malignancies. It also modulates T cell responses through a diverse array of mechanisms including induction of apoptosis, TCR cross linking in CD8+ T cells, and T cell receptor (TCR) down regulation in CD4+ T cells. We found that patients responding to a granulocyte-macrophage colony-stimulating factor (GM-CSF) secreting allogeneic pancreatic tumor vaccine developed post immunization antibody responses to galectin-3 on a proteomic screen. We used the HER-2/neu (neu-N) transgenic mouse model to study galectin-3 binding on adoptively transferred high avidity neu-specific CD8+ T cells derived from TCR transgenic mice. Here, we show that galectin-3 binds preferentially to activated antigen-committed CD8+ T cells only in the tumor microenvironment (TME). Galectin-3 deficient mice exhibit improved CD8+ T cell effector function and increased expression of several inflammatory genes when compared with wild type (WT) mice. We also show that galectin-3 binds to LAG-3, and LAG-3 expression is necessary for galectin-3 mediated suppression of CD8+ T cells in vitro. Lastly, galectin-3 deficient mice have significantly elevated levels of circulating plasmacytoid dendritic cells (pDCs), which are superior to conventional dendritic cells (cDCs) in activating CD8+ T cells. Binding of galectin-3 to cell-surface glycoproteins on immune cells suppresses a pro-inflammatory immune response. Thus, inhibiting galectin-3 in conjunction with CD8+ T cell directed immunotherapies should enhance the tumor specific immune response. 3 different experimental groups were studied. Galectin-3 WT CD8 T cells adoptively transferred into Galectin-3 WT mice, galectin-3 WT CD8 T cells transferred into galectin-3 KO mice, and finally galectin-3 KO CD8 T cells transferred into galectin-3 KO mice. Galectin-3 WT CD8 T cells transferred into Galectin-3 WT mice were used as the reference group. Four biological replicates were submitted for each group, and adoptively transfered CD8 T cells were isolated 5 days post-adoptive transfer into tumor-bearing mice treated with a whole cell GM-CSF secreting vaccine. Cells were purified by cell sorting on the Thy1.2 surface marker.

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Apoptosis-regulated low avidity cancer-specific CD8+ T cells can be rescued to eliminate HER-2/neu expressing tumors by costimulatory agonists in tolerized mice

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