Huntington's disease reduces cancer risk

A study by Swedish researchers published Online First in The Lancet Oncology suggests that people with Huntington's disease or other diseases known as polyglutamine (polyQ) diseases have a lower risk of developing cancer, due to a common genetic mechanism. Polyglutamine (polyQ) disease is a rare neuro-degenerative disorder, in which the expansion of certain sequence, such as Cystosine-Adenine-Guanine or CAG, is repeated in particular genes. The polyG group consists of nine identified diseases, including spinobulbar muscular atrophy (SBMA), Huntington's disease (HD), dentatorubral and pallidoluysian atrophy, as well as six types of spinocerebellar ataxia. Patients with polyQ diseases all have a progressive degeneration of a population of neurons within the central nervous system that affect the person's motor control. All PolyQ diseases possess proteins that contain polyglutamine, which accumulate in the cytoplasm and/or nucleus, interacting with several transcription factors that impede the activity of numerous genes. This accumulation ultimately leads to dysfunction of the cellular machinery and cell death. Dr Jianguang Ji from the Lund University and Skåne University Hospital in Malmö, Sweden, and his team believe that the same mechanism could potentially reduce the development of cancer in patients with a polyG disease and decided to analyze data from the Swedish cancer registry from January 1969 to December 2008. They identified 1,510 patients with HD, of which 91 patients (6%) were diagnosed with cancer, 471 patients with SBMA, of which 34 patients or 7% were diagnosed with cancer, and 3,425 with hereditary ataxia (HA, analyzed as a surrogate of spinocerebellar ataxia) of which 421 or 12% of patients were diagnosed with cancer. In comparison with the general population, the likelihood of being diagnosed with cancer was 53% lower in HD patients, 35% lower in SBMA patients, and 23% lower in HA patients, with the risk of cancer being even lower prior to being diagnosed with a polyQ disease. The risk of cancer in healthy parents of polyQ disease patients was comparable with that of the general population. In a concluding statement the researchers state: "Our findings suggest a common mechanism in patients with polyQ diseases that protects against the development of cancer, and expansion of the polyglutamine tracts seems likely... Future studies should investigate the specific biological mechanisms underlying the reduced cancer risk in patients with polyQ diseases."