Possible contribution of chronic inflammation in the induction of cancer in rheumatic diseases.

Several chronic inflammatory conditions and autoimmune diseases involving different organs and tissues have been found at risk of progression to cancer. A wide array of proinflammatory cytokines, prostaglandins, nitric oxide products, and matricellular proteins are closely involved in premalignant and malignant transition of cells almost always in a background of chronic inflammation. Interestingly, epigenetic perturbations (i.e. miRNA aberrations, altered DNA methylation) together with important steroid hormone metabolic changes (i.e. oestrogens), or the altered vitamin D concentrations that may unbalance the immune / inflammatory response, have been found linked to the risk and severity in several chronic inflammatory conditions, as well as in cancer. In particular, it is evident, that not only the parent oestrogen but also oestrogen metabolites should be taken into account when this process is evaluated, specially the formation of catecholoestrogen metabolites, that are capable of forming either stable or depurinating DNA adducts, which can cause extensive DNA damage. It is interesting that today the successful treatment of several chronic immune/inflammatory rheumatic diseases is obtained also by using medications initially developed for their use in oncology. The circadian increase of growth factors, specially during the late night, in both chronic inflammation and in cancer patients, as well as the presence of oestrogen-regulated circadian mechanisms, suggests further important links.