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. Author manuscript; available in PMC: 2018 Jul 1.
Published in final edited form as: Cancer Treat Rev. 2017 Jun 1;58:22–33. doi: 10.1016/j.ctrv.2017.05.006

Fig. 3.

Fig. 3

Mechanisms of tumor immune escape. ‘Hot’ tumors (A) may escape through up-regulation of immune checkpoint molecules and Tregs, secretion of immunosuppressive factors, indoleamine-2,3-dioxygenase (IDO), or T-cell anergy. (B) Tumor intrinsic mechanism of escape in “cold tumors” by downregulation of MHC molecules, attraction of M2 tumor-associated macrophages (TAMs), alteration of the tumor microenvironment, discouraging T-cell homing either by subduing inflammation, or suppressing release of T-cell chemokines, or releasing inhibitory cytokines to impair the recruitment of immune cells to the tumor microenvironment, or by dysregulating oncogene pathways including PI3 kinase/PTEN/AKT, p53 and STAT3 signaling.