Effects of Obesity on Cancer Progression by Affecting the Immune System

The prevalence of obesity has been increasing in the last few decades, and it is regarded as one of the major health problems in the world. The rising prevalence of obesity in children and adults is a result of eating disorders and the changes related to the modern lifestyle. Obesity alters the adipocytes’ substance secretion, which affects the function of the immune system and leads to obesity-induced inflammation and the development of obesity-related cancers. Altered chemokines, adipokines, and conditions like insulin resistance are most likely related to the impaired immune system in the obesity state. The impaired secretion of adipokines, such as increased leptin and reduction in adiponectin, affects innate immune system antitumor responses after long-term exposure. In addition, changes in chemokines and, consequently, the promotion of insulin resistance create an immunosuppressive environment that debilitates the host to fight against tumor growth, progression, and metastasis. Accordingly, it may increase cancer susceptibility in obese individuals. Thereby, it can be concluded that treatment of obesity will greatly affect the improvement of immune system function and, as a result, may possibly reduce the risk of cancer. The aim of this study is to review the pathways resulting in impaired immune system and inflammation and their link to cancer progression in obesity. Several hypotheses have been proposed to have a critical contribution to the development of obesity-related cancers, such as the function of cytokines, insulin resistance, and NF-κB and senescence changes in obesity. These hypotheses will be discussed later in this article.