Transforming growth factor-beta1 and myeloid-derived suppressor cells: A cancerous partnership

Abstract

Transforming growth factor-beta1 (TGF-beta 1) plays a crucial role in tumor progression. It can inhibit early cancer stages but promotes tumor growth and development at the late stages of tumorigenesis. TGF-beta 1 has a potent immunosuppressive function within the tumor microenvironment that largely contributes to tumor cells' immune escape and reduction in cancer immunotherapy responses. Likewise, myeloid-derived suppressor cells (MDSCs) have been postulated as leading tumor promoters and a hallmark of cancer immune evasion mechanisms. This review attempts to analyze the prominent roles of both TGF-beta 1 and MDSCs and their interplay in cancer immunity. Furthermore, therapies against either TGF-beta 1 or MDSCs, and their potential synergistic combination with immunotherapies are discussed. Simultaneous TGF-beta 1 and MDSCs inhibition suggest a potential improvement in immunotherapy or subverted tumor immune resistance.