Epithelial-mesenchymal transition and immunosuppression: Two sides of the same coin

Epithelial-mesenchymal transition has long been studied as a physiologic process that is critical for embryonic development, wound healing, and cancer progression. Activation of the EMT program confers on cancer cells many cellular traits associated with high-grade malignancies. These include invasion, motility, the acquisition of stem cell-like features, and resistance to multiple therapies. An emerging frontier of the EMT program, is its ability to regulate the activity of immune cells within tumors and drive resistance to immune checkpoint blockade therapies. In this review, we provide an overview of the mechanistic underpinnings of EMT-driven immunosuppression on specific subsets of innate and adaptive immune cells present within primary tumors. We also provide an insight into the role of various EMT-transcription factors in regulating the expression of cancer cell-intrinsic immunosuppressive and immunoevasive factors. Additionally, we review the consequences of EMT-driven immunosuppression on distinct steps of the invasion-metastasis cascade. Finally, we summarize studies that document EMT-driven immunosuppression in multiple cancer types.