Application of Traditional Chinese Medicine in Inhibiting the PD-1/PD-L1 Pathway in the Treatment of Gastric and Colon Cancers

Immune checkpoint regulation is a negative feedback regulatory mechanism in the body, and sequential death receptor-1 (PD-1) and programmed death receptor ligand-1 (PD-L1) are known as immune checkpoints. The PD-1/PD-L1 pathway inhibits the activity of effector T cells through a negative regulatory mechanism to avoid excessive response-induced body damage. PD-L1 is highly expressed in many tumor tissues, and high PD-L1 expression can ultimately lead to tumor immune escape. Therefore, immune checkpoint blockade with inhibition of negative immune regulation therapy has become a cutting-edge hot spot for antitumor therapy, with the main target molecules being PD-1 and PD-L1. Recent years have seen promising progress in the study of traditional Chinese medicines and their effects on gastric and colon cancers, particularly in relation to the PD-1/PD-L1 pathway mechanisms. This review specifically examines the modulation of the PD-L1 pathway by certain traditional Chinese medicines in gastric and colon cancers, aiming to provide insights for the development of innovative drugs for these types of digestive cancers.