Ovarian carcinoma-infiltrating regulatory T cells were more potent suppressors of CD8+ T cell inflammation than their peripheral counterparts, a function dependent on TIM3 expression

Ovarian carcinoma is one of the most severe cancers in women, with a high relapse rate and limited secondary treatment options. To assist research in novel treatment technologies, including CD8(+) T cell-base immunotherapy, we examined the effect of tumor-infiltrating regulatory T cells (Tregs) in inhibiting CD8(+) T cell inflammation. We found that compared to their peripheral blood counterparts, tumor-infiltrating Tregs exhibited more potent inhibitory function, which was associated with higher interleukin 10 (IL-10) production in tumor-infiltrating Tregs. Blockade of T cell immunoglobulin mucin 3 (TIM3), a regulatory molecule overrepresented on tumor-infiltrating Tregs, had significantly reverted Treg-mediated suppression. Moreover, expression of TIM3 on tumor-infiltrating Tregs was directly correlated with tumor size. Together, our results demonstrated that ovarian tumor-infiltrating Treg cells were more immunosuppressive than their peripheral blood counterparts in a TIM3-dependent fashion.