Could this really be true? Is there actually a correlation between sleep and cancer? It almost seems as if society attributes everything to cancer, and we have heard so many claims, whether true or not— that hair-dye, teeth-whitening, diet soda, cell phones, plastic water bottles, and even burnt toast cause cancer. I thought it would be best to refer to scientific literature and to verify the statement made in the news article, before jumping onto the ‘cancer scare’ bandwagon.
One study, published in Circadian Disruption Accelerated Tumor Growth and Angio/Stromagenesis through a Wnt Signaling Pathway, seems to prove the existing link between sleep and cancer. The experiment implanted human edipermoid and prostate cancer cell tumors into mice, in which one group of mice, the L/L, was exposed to “24-hour periods of light,” and the other group, the L/D, was exposed to “12-hour light/dark cycles” [2]. After just 21 days, scientists found tumor growth in the L/L mice to be significantly greater than that in L/D mice. L/L mice tumors also exhibited high “microvessel density,” the epitome of angiogenesis (a hallmark of cancer) [2]. Moreover, upregulation of certain secretory proteins was seen in L/L tumors—the expression of the WNT10A gene was 9 times higher in L/L than in L/D tumors [2]! These results show that “abnormal circadian rhythms induce…tumor growth” and WNT10A to be a probable responsible gene [2].
A comparison of the relative tumor sizes found on L/D and L/L mice after 21 days [2]For some background information, WNT10A is located on Chromosome 2, position 35. It is responsible for secreting proteins that “regulate cell fate and patterning during embryogenesis” [3]. WNT10A is “implicated in oncogenesis,”and its mutation can lead to ectodermal dysplasia anhidrotic, odonto-onycho-dermal dysplasia, and Schopf-Schulz-Passarge syndrome [3].
As of now, a “precise molecular mechanism played by circadian rhythms in tumor progression is not known;” however, I felt that the results of this study were quite legitimate [2]. While further research is necessary, it is worthwhile to consider the implications of this specific study and what they mean for us. Many of us may not work night shifts in hospitals or factories, but as college students, we frequently sleep late and pull all-nighters. What does this disruption of our circadian systems entail for us? Mice saw tumor growth in just 21 days, but what about humans? It could be that we do not experience side effects immediately, but there is no guarantee for years to come. Moreover, could tumor growth result from being exposed to light 24-hours of the day as the L/L mice? For those who have regular sleep schedules but never turn off the lights at night (like me), is this behavior equally harmful to circadian disruption?
Numerous studies have already been done, and are continuing to be done, about circadian disruption and its link to cancer. For those interested, here are some more articles that discuss the topic:
Shift Work, Light at Night, and the Risk of Breast Cancer
Circadian Rhythm and Its Role in Malignancy
Melatonin as a Biomarker of Circadian Dysregulation
I thought it would be interesting to look up WNT10A on COSMIC to see what kind of mutations could occur in the gene and perhaps which mutations are unique to which types of cancer. Unfortunately, I could not find any information on the database.
[1] Schmid, R. (2011, April 16). Odd Work Schedules Pose Risk to Health. ABC News. Retrieved from http://abcnews.go.com/
[2]Yasuniwa, Y., Izumi, H., Wang, K., Shimajiri, S., Sasaguri, Y., Kawai, K., … Kohno, K. (2010). Circadian Dysregulation Accelerated Tumor Growth and Angio/Stromagenesis through a Wnt Signaling Pathway. Plus One, 5, 1-12
[3]U.S. National Library of Medicine (2011). WNT10A. Retrieved from Genetics Home Reference: http://ghr.nlm.nih.gov/gene/WNT10A
