Patients with Huntington’s disease have a considerably lower risk of developing cancer, researchers from Lund University, and Skåne University Hospital, Malmö, Sweden, reported in the journal Lancet Oncology. The same applies to other polyQ (polyglutamine) diseases, the authors added.
PolyQ disorders are a group of uncommon neurogeneretative disorders, characterized by the expansion of CAG (Cystosine-Adenine-Guanine) repeats in specific genes – they are inherited neurodegenerative diseases caused by polyQ expansion in the mutant proteins.
The nine diseases that have been identified include:
- Huntington’s disease (HD)
- Pallidoluysian atrophy
- Spinobulbar muscular atrophy (SBMA)
- 6 types of spinocerebellar ataxia
Huntington’s disease is neurodegenerative genetic disorder. Patients’ muscle coordination is affected; there are also cognitive decline and psychiatric problems. Signs and symptoms become more apparent during mid-adulthood. Neurologists say Huntington’s disease is the most common genetic cause of chorea – abnormal involuntary writhing movements. The disease used to be called Huntington’s chorea.
All polyQ disorders present with progressively worsening degeneration of a group of neurons in the CNS (central nervous system) that regulate motor control.
In polyQ disorders, proteins that contain polyglutamine build up in the cytoplasm, nucleus or both, and interfere with the workings of several transcription factors, and undermine the activity of a number of genes. The build-up eventually leads to dysfunction of the cellular machinery, and ultimately, the death of cells. The researchers assume that this same mechanism may block the development of cancer in patients with polyQ disorders.
Dr Jianguang Ji and team gathered data from the Swedish cancer registry.
The researchers found that from the beginning of January, 1969, to December 2008:
- 1,510 individuals had Huntington’s disease
- 471 had spinobulbar muscular atrophy
- 3,425 had hereditary ataxia (analyzed as a surrogate of spinocerebellar ataxia)
- 91 Huntington’s disease patients had a cancer diagnosis – 6% of them
- 34 spinobulbar muscular atrophy patients had a cancer diagnosis – 7% of them
- 421 hereditary ataxia had a cancer diagnosis – 12% of them
- Huntington’s disease patients had a 53% lower chance of developing cancer compared to the general population
- Spinobulbar muscular atrophy patients had a 35% lower chance of developing cancer
- Hereditary ataxia patients had a 23% lower chance of developing cancer
- Among healthy parents with offspring with polyQ diseases, cancer risk was similar to that found in the general population
The researchers concluded:
“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.”
Written by Christian Nordqvist