Fig. 4. Controversial role of Tc17 cells in the tumor microenvironment.

Tc17 cells in the tumor microenvironment play distinct roles in tumor growth depending on their origin. ① In vitro-generated Tc17 cells are converted to effector Tc1 cells and repress tumor cell growth. On the other hand, Tc17 cells generated in vivo have been shown to exhibit pro-tumorigenic effects. ② Tc17 cells induced in the tumor microenvironment followed by CD4 depletion to recruit infiltrating myeloid cells and accelerate the exhaustion of effector Tc1 cells. ③ Tc17 cells from cancer patients presented with a terminally exhausted phenotype, which resulted in impaired antitumor immune responses.