T-bet and Tumor Immunity

描述(申请人提供)：原发肿瘤的局部进展由1型免疫反应外部控制，特别是通过细胞因子IFNGamma，其分泌高度依赖于辅助T细胞。T-box转录因子T-bet(Tbx21)在1型辅助性T细胞的发育过程中起着关键作用，对干扰素的产生也是必不可少的。我们最近发表的证据表明，T-bet通路在转基因小鼠前列腺癌模型中在转移性疾病的发展中发挥着显著的抑制作用。我们在这一资助期的总体目标是探索T-bet对抗肿瘤的细胞和分子机制。我们将使用前列腺癌的TRAMP转基因模型和一组基因突变的T-bet小鼠来确定T-bet在先天性和获得性免疫系统中表达细胞类型在抗癌免疫中的作用。然而，考虑到Th1细胞在肿瘤免疫中的重要性，我们将把主要精力放在这种细胞类型上，因为我们对标志性Th细胞中的T-bet功能还有很多不了解的地方。Th1细胞向炎症部位的迁移及其与内皮细胞的黏附对炎症和肿瘤免疫至关重要。我们有初步数据表明，T-bet缺陷的Th1细胞在体外和体内迁移和黏附内皮的能力受损，可能是通过调节T细胞中尚未识别的控制肿瘤细胞迁移的基因来实现的。我们在高表达T-bet的人Th细胞中的基因表达分析发现了一系列由T-bet控制的黏附/归巢受体，我们在小鼠中发现了三个靶基因：MlP1pha、TIM3和CXCR3。我们计划进一步探索T-bet-/-Th1细胞体内T细胞迁移的缺陷，并通过与麻省理工学院的Richard Young博士合作，对人和小鼠T-bet启动子结合位点进行全面扫描，结合基因表达分析，寻找更多的T-bet靶基因。我们最近在T-bet蛋白中发现了一个残基，它的突变完全取消了Th1细胞中的T-bet功能，机制尚不清楚，但可能是通过调控T-bet同源二聚体和异源二聚体的形成，以及尚未确定的蛋白质。我们发现其中一种蛋白质是Th2特异性转录因子GATA-3。我们还发现，TCR信号导致T细胞激酶ITK在第525位发生T-bet酪氨酸磷酸化。我们还不知道这种磷酸化事件在T细胞中的功能，也不知道T-bet是否在其他类型的细胞如树突状细胞中被酪氨酸磷酸化，这些问题我们将进行探索。

DESCRIPTION (provided by applicant): The local progression of primary tumors is extrinsically controlled by type 1 immune responses, particularly via the cytokine IFNgamma, whose secretion is highly dependent on helper T cells. The T-box transcription factor T-bet (Tbx21) plays a critical role in the development of type 1 helper T cells and is essential for the production of IFN?. We have recently published evidence that the T-bet pathway in an autochthonous transgenic mouse prostate adenocarcinoma model exerts a significant suppressor function in the development of metastatic disease. Our overall goal for this funding period is to explore the cellular and molecular mechanisms by which T-bet functions to combat tumors. We will use the TRAMP transgenic model of prostate cancer and a panel of genetic mutant T-bet mice to determine the contributions of T-bet expressing cell types in both the innate and adaptive immune systems in immunity against cancer. However, given the known importance of the Th1 cell in tumor immunity, we will focus most of our efforts on this cell type because there is much we still do not understand about T-bet function in the signature Th cell. The migration of Th1 cells to inflamed sites and their adherence to endothelium is critical to inflammation and to tumor immunity. We have preliminary data that T-bet deficient Th1 cells have an impaired capacity in vitro and in vivo to migrate to and adhere to endothelium presumably by regulating yet to be identified genes in T cells that govern tumor cell migration. Our gene expression analyses in T-bet overexpressing human Th cells identified a series of adhesion/homing receptors controlled by T-bet and three target genes we have identified in the mouse are MlP1alpha, Tim3 and CXCR3. We plan to further explore the defects in T cell migration in T-bet-/- Th1 cells in vivo and to search for additional T-bet target genes by performing a comprehensive scan of human and mouse T-bet promoter binding sites coupled with gene expression analysis in collaboration with Dr. Richard Young at MIT. We recently identified single residues in the T-bet protein whose mutation completely abolishes T-bet function in Th1 cells by unknown mechanisms but perhaps through governing T-bet homodimer and heterodimer formation with proteins yet to be identified. We have discovered that one such protein is the Th2-specific transcription factor GATA-3. We have also discovered that TCR signaling results in T-bet tyrosine phosphorylation at residue 525 by the T cell kinase, Itk. We do not know the function of this phosphorylation event yet in T cells nor do we know whether T-bet is tyrosine phosphorylated in other cell types such as dendritic cells, questions we will explore.