By Lisa Rapaport
(Reuters Health) – Variations in a gene involved in so-called
circadian rhythms that control everything from cell division to
sleep may also promote the spread of breast cancer to other
organs, a new study suggests.
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.
“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.