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Cancer and the Immune System continued
Chronic inflammation is a feature of many chronic diseases, including cancer [9‐11] and the inflammatory cells involved are major components in the environment
surrounding tumours [7, 12]. Additionally, this chronic inflammation can ‘tire’ the immune system, which means that it is weaker to fight other diseases [13, 14],
especially in those patients who have had their immune system further weakened by chemotherapy or radiotherapy [15].
Chronic, low‐grade inflammation increases the susceptibility to cancer, and arises due to chronic conditions such as obesity [16] and inappropriate lifestyle habits
such as diet, sedentary behaviour and smoking [1, 17].
Inflammation has potential involvement in every stage of cancerous growth, mediated by its constituent immune effector cells, which include: cytokines, growth
factors and reactive oxygen species, amongst others [18]. Tumour associated macrophages are predominant secretors of these inflammatory mediators, in
particular, cytokines and nitric oxide synthases, which promote angiogenesis (the formation of new blood vessels, which supply the tumour with oxygen) [19] and
tumour growth [20]. Inducible nitric oxide synthase (iNOS) is found at higher levels at the early stages of carcinogenesis, alongside cyclooxygenase‐2 (COX‐2),
another player in the promotion of tumour growth [21]
