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 In mouse studies, researchers showed how having slightly different
versions of gene called Arntl2 can aid the spread of cancer cells.
When they analyzed the genes of breast cancer patients, they also
found that at least one version of Arntl2 was indeed linked to how
long the women survived disease-free.
“Our results suggest that there is a link between inherited factors
that may influence how well circadian rhythms may be regulated and
the probability that breast cancer will spread,” said senior study
author Kent Hunter, a researcher at the National Cancer Institute in
Bethesda, Maryland.
The activity of Arntl2, which regulates when and if certain other
genes are activated, can affect whether a common, hard-to-treat type
of malignancy known as estrogen receptor negative breast cancer will
spread, becoming more lethal, Hunter and his colleagues write in the
journal PLOS Genetics.
When breast cancer doesn’t spread, 99 percent of women survive at
least five years after their diagnosis, the authors note. But when
it does spread, or metastasize, five-year survival odds plummet to
26 percent.
With estrogen receptor negative tumors, hormone therapy is unlikely
to work, leaving women with fewer treatment options than they might
have with other types of breast cancer.
The study found that one particular version of Arntl2 was associated
with a 29 percent lower risk of death for women who had it. That
could guide treatment of women with this or other inherited versions
of the gene, and it also makes the gene a potential target for new
drug development, the researchers note.
This and other “clock genes” have previously been linked to cancer
risk, and so have sleep patterns, which are also regulated by
circadian rhythms in the body.
“We know that regular sleep is an important part of our circadian
rhythm, and we know that much of our health, particularly with
regard to DNA repair when we talk about cancer, is regulated by our
circadian rhythm,” said Cheryl Thompson, a researcher at Case
Western Reserve University who wasn’t involved in the study.
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“There is still more work to be done to see if sleeping longer or
getting better quality sleep can decrease your risk of getting
cancer, or likelihood of getting an aggressive cancer,” Thompson
added by email.
Women, of course, can’t control whether they will inherit a genetic
variation in the Arntl2 gene, noted Amanda Phipps, an epidemiology
researcher at the University of Washington who wasn’t involved in
the study.
“However, beyond this study, there is increasing evidence to support
the health benefits of good quality sleep,” Phipps said by email.
“In our own research, we recently found that breast cancer survival
was poorest among women who reported, before their breast cancer
diagnosis, that they typically received less than 6 hours of sleep
per night.”
In terms of cancer prevention, women are traditionally advised to
focus on lifestyle factors such as eating well and getting enough
exercise, and avoiding smoking or too much alcohol, Phipps added.
“However, with growing recognition as to the health implications of
poor quality and insufficient sleep, it is plausible that cancer
prevention efforts could expand to encompass recommendations for
healthy sleep,” Phipps said.
SOURCE: http://bit.ly/2dcRp94 and http://bit.ly/2cUG4g2 PLOS
Genetics, online September 22, 2016.
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