Reshaping the immune microenvironment and reversing immunosenescence by natural products: Prospects for immunotherapy in gastric cancer.

Gastric cancer (GC) represents a global health-care challenge. Recent progress in immunotherapy has elicited attracted considerable attention as a viable treatment option through modulating the host immune system and unleashing pre-existing immunity, which has profoundly revolutionized oncology, especially GC. Nonetheless, low clinical response and intrinsic and acquired resistance remain persistently challenging. The microenvironment of GC comprising multifarious stromal cell types has remarkable immunosuppressive elements that may impact the efficacy of immunotherapy. Immunosenescence is increasingly regarded as a factor that contributes to cancer development, remodels the tumor microenvironment and affects the efficacy of immunotherapy. Natural products are at the forefront of traditional medicine. Senotherapeutics is a class of drugs and natural products capable of delaying, preventing, or reversing the senescence process (i.e., senolytics) or suppressing senescence-associated secretory phenotype (i.e., senomorphics). Emerging evidence supports that natural products can improve the efficacy of existing immunotherapy and expand their indications in GC mainly based upon remodeling the immunosuppressive microenvironment and reversing immunosenescence. The review provides an integrated review of previously reported and ongoing clinical trials with immunotherapeutic regimens in GC and discusses current challenges. Next, we focus on natural compounds that exert anti-GC functions and possess immunomodulatory properties. More attention is paid to the potential of these natural compounds in modulating the immune microenvironment and immunosenescence. Lastly, we discuss the nanomedicine that can overcome the deficiencies of natural products. Altogether, our review suggests the enormous potential of natural compounds in GC immunotherapy, and provides an important direction for future research.