1810011o10 Rik Inhibits the Antitumor Effect of Intratumoral CD8+ T Cells through Suppression of Notch2 Pathway in a Murine Hepatocellular Carcinoma Model

The mechanisms by which tumor-responsive CD8+ T cells are regulated are important for understanding the tumor immunity and for developing new therapeutic strategies. In current study we identified the expression of 1810011o10 Rik, which is the homologue of human TC1, in intratumoral activated CD8+ T cells in a murine hepatocellular carcinoma (HCC) implantation model. To investigate the role of 1810011o10 Rik in the regulation of anti-tumor activity of CD8+ T cells, normal CD8+ T cells were transduced with 1810011o10 Rik-expressing lentiviruses. Although 1810011o10 Rik overexpression did not influence agonistic antibody-induced CD8+ T cell activation in vitro, it inhibited the cytotoxic efficacy of CD8+ T cells on HCC cells in vivo. 1810011o10 Rik-overexpression impeded CD8+ T cell-mediated HCC cell apoptosis and favored tumor cell growth in vivo. Further investigation revealed that 1810011o10 Rik blocked the nuclear translocation of Notch2 intracellular domain which is crucial for CD8+ T cell activity. Furthermore, a brief in vitro experiment suggested that both antigen presenting cells and TGF-β might be necessary for the up-regulation of Rik expression in activated CD8+ T cells. In general, our study disclosed a novel mechanism underlying the negative regulation of anti-tumor CD8+ T cells during HCC progression.