Immunomodulation and anti-inflammatory roles of polyphenols as anticancer agents

Cancers are the largest cause of mortality and morbidity in industrialized countries. Several new concepts have emerged in relation to mechanisms that contribute to the regulation of carcinogenesis processes and associated inflammatory effects such as the modulation of innate immune cells and adaptive immune cells that could infiltrate the tumor. In the tumor microenvironment, there is a delicate balance between antitumor immunity and tumor-originated proinflammatory activity, which weaken antitumor immunity. Consequently; modulation of immune cells and inflammatory processes represent attractive targets for therapeutic intervention in malignant diseases with the goal to restore the sensitivity of cancer cells to chemotherapies and to overcome resistance to current cytotoxic therapies. Numerous studies have reported interesting properties of dietary polyphenols in anticancer strategies notably by their pleiotropic properties on cancer cells, immune cells and inflammation. This review is dedicated to the current knowledge of the mechanisms of polyphenols (resveratrol, curcumin, genistein and epigallocatechin) against cancers through a modulation of the immune system and the pro-inflammatory mediator production. We describe the effects of polyphenols on the adaptative and innate immune cells that could infiltrate the tumor. Reduction of chronic inflammation or its downstream consequences may represent a key mechanism in the fight of cancer development and polyphenols could reduce various pro-inflammatory substance productions through targeting signal transduction or through antioxidant effects. Lastly, we analyze key molecular links between inflammation and tumor progression through nuclear factors such as NFκB or microRNAs.