Paradoxical roles of the immune system during cancer development

Abstract

Adaptive and innate immune cells regulate tissue homeostasis and efficient wound healing. Altered interactions between adaptive and innate immune cells can lead to chronic inflammatory disorders. In cancers, an abundance of infiltrating innate immune cells, such as macrophages, mast cells and neutrophils, correlates with increased angiogenesis and/or poor prognosis. In cancers, an abundance of infiltrating lymphocytes correlates with favourable prognosis. Chronic inflammatory conditions enhance a predisposition to cancer development. Long-term usage of non-steroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors reduces cancer incidence. Polymorphisms in genes that regulate immune balance influence cancer risk. Immune status in humans and in mouse models affects the risk of cancer development in an aetiology-dependent manner. Genetic elimination or depletion of immune cells alters cancer progression in experimental models. Activation of antitumour adaptive immune responses can suppress tumour growth.