PD-L1 and TGF-β cooperatively regulate tumor immune escape: mechanisms and advances in dual-targeting therapy

While programmed cell death ligand 1 (PD-L1) inhibitors have yielded breakthroughs in tumor therapy, their efficacy is constrained by the heterogeneity of the tumor microenvironment and multiple immunosuppressive pathways. In recent years, research has revealed that transforming growth factor-β (TGF-β) synergistically drives tumor cell immune escape with PD-L1 via pathways such as metabolic reprogramming, epithelial-mesenchymal transition, and SOX family factors. Currently, various PD-L1/TGF-β bispecific antibodies (bsAbs) have exhibited promising therapeutic potential in early-phase clinical trials, yet they still confront challenges related to toxicity and drug resistance. This article systematically reviews the mechanisms by which PD-L1 and TGF-β synergistically regulate tumor immune escape, summarizes the clinical research progress of bsAbs, and discusses strategies for novel drug design and biomarker development, with the aim of offering new insights for the development of combined tumor immunotherapy strategies.