Melanoma cells express ICOS ligand to promote the activation and expansion of T-regulatory cells.

Martin-Orozco, Natalia; Li, Yufeng; Wang, Yijun; Liu, Shijuan; Hwu, Patrick; Liu, Yong-Jun; Dong, Chen; Radvanyi, Laszlo · Cancer Res · 2010

basic_science · Level V

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Abstract

CD4(+)CD25(+)Foxp3(+) T-regulatory cells (Tregs) accumulate in tumors; however, little is known about how the tumor environment influences this process. Here we show that human melanomas express inducible T-cell costimulator ligand (ICOS-L/B7H) that can provide costimulation through ICOS for the expansion of activated Tregs maintaining high Foxp3 and CD25 expression as well as a suppressive function. Thus, ICOS-L expression by melanoma tumor cells may directly drive Treg activation and expansion in the tumor microenvironment as another mechanism of immune evasion.

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