Huntington’s Disease Protects Against Cancer
Before the diagnosis of the PolyQ disease, Ji and colleagues reported, the risk of cancer was even lower.
On the other hand, cancer incidence and risk in the unaffected parents were not significantly different from those in the general population, they found.
The implication, Ji and colleagues concluded, is that “a common mechanism in patients with PolyQ diseases ... protects against the development of cancer.”
PolyQ diseases belong to a group of rare neurodegenerative disorders that are characterised by the expansion of certain amino acid sequence repeats (Cystosine-Adenine-Guanine or CAG) in specific genes.
In these diseases, polyglutamine-containing proteins accumulate in the cytoplasm, nucleus, or both, and interact with numerous transcription factors, which impedes the activity of many genes. Eventually, accumulation leads to dysfunction of the cellular machinery and to cell death. The authors postulate that this same mechanism could possibly reduce the development of cancer in these patients.
The authors conclude: “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.”
Expansion of the polyglutamine tracts seems “likely” to be the cause, they argued, adding that more research to tease out the mechanism seems warranted.
They cautioned that they were unable specifically to identify patients with the six types of spinocerebellar ataxia because diagnostic codes are not available. On the other hand, the six types account for 60% of all hereditary ataxia and the results for that condition did not change when recessive cases were excluded.
They also noted that diagnostic codes were changed during the study period, which might have led to some inconsistency in the records.
The study had support from the Swedish Cancer Society and the Swedish Council for Working Life and Social Research. The journal said the authors declared they had no conflicts.
Primary source: The Lancet Oncology
Source reference: Ji J, et al “Cancer incidence in patients with polyglutamine diseases: a population-based study in Sweden” Lancet Oncol 2012; DOI: 10.1016/S1470-2045(12)70132-8.