The Confounders of Cancer Immunotherapy: Roles of Lifestyle, Metabolic Disorders and Sociological Factors

SIMPLE SUMMARY: The human immune system is robustly equipped to keep unnatural cell growth in check in the body to suppress cancer progression. However, the cells and molecules of the immune system responsible for preventing cancer growth are often severely compromised in patients harboring this disease. Therefore, to elicit a functional immune response against cancer, scientists have developed antibodies, known as checkpoint inhibitors (CPI), which unleash the compromised immune cells and potentiate them with cancer killing ability. Although CPI revolutionized the treatment of certain cancers, many patients do not respond to the CPI and the treatment outcome varies disproportionately between cancer types. This review elaborates on how lifestyle, metabolic and sociological factors play a role in determining the outcome of CPI treatment. We also discuss potential ways to enhance CPI efficacy by mitigating the effect of these confounding variables. ABSTRACT: Checkpoint blockade immunotherapy (CPI) is an effective treatment option for many types of cancers. Irrespective of its wide clinical implications, the overall efficacy remains unpredictable and even poor in certain pathologies such as breast cancer. Thus, it is imperative to understand the role of factors affecting its responsiveness. In this review, we provide an overview on the involvement of sociological factors, lifestyles and metabolic disorders in modulating the CPI response in patients from multiple malignancies. Lifestyle habits including exercise, and diet promoted therapeutic responsiveness while alcohol consumption mitigated the CPI effect by decreasing mutational burden and hampering antigen presentation by dendritic cells. Metabolic disorder such as obesity was recognized to enhance the PD-1 expression while diabetes and hypertension were consequences of CPI therapy rather than causes. Among the sociologic factors, sex and race positively influenced the CPI effectiveness on account of increased effector T cell activity and increased PD-1 expression while ageing impaired CPI responsiveness by decreasing functional T cell and increased toxicity. The combined effect of these factors was observed for obesity and gender, in which obese males had the most significant effect of CPI. Therefore these variables should be carefully considered before treating patients with CPI for optimal treatment outcome.