In experimental and epidemiological studies, chronic inflammation is an important factor in tumour development. Chronic inflammation can result from viral or bacterial infections, autoimmune disease, and inflammatory conditions of unknown origin. It is known that mutations in key inflammatory control genes are associated with a higher risk of cancer progression. Inflammatory markers are associated with worse recovery prospects in cancer patients. Inflammation seems to be closely related to the development of cancer. Since leukocyte activity involves the production of proteins (cytokines and chemokines) that alter the behaviour of target cells, it stimulates blood vessel growth (angiogenesis) and tissue remodelling. Immune cells can also cause DNA mutations by generating oxygen free radicals. Inflammatory cytokines activate specific transcription factor NF-kB, and activation of NF-kB has been shown to lead to more aggressive tumour manifestations, including resistance to normal growth control mechanisms, anxiogenic capacity and metastasis. Tumour-associated macrophages (TAM) are also associated with inflammatory pathways. TAM has been observed to produce pro-angiogenic factors and generate new blood vessels early in tumour development. TAM further increasing the growth rate of tumour cells, and cause dissolution of the connective tissue surrounding the tumour, tumour growth and spread to make 71.
Several types of cancer associated with chronic inflammatory conditions include: colon and inflammatory bowel disease, liver cancer and hepatitis C, bladder or colon cancer and schistosomiasis (chronic parasitic infection), gastric cancer and Helicobacter pylori infection 72.