Jan 20, 2009 - SNPWatch

SNPwatch: One Variation, Many Cancers

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

Each type of cancer has its own idiosyncrasies, but when it comes down to it, they all have one thing in common: failure to control cellular growth. So it’s somewhat surprising that when genome-wide association studies have looked for single common variations associated with the risks for multiple types of cancer, they have for the most part identified only SNPs that are peculiar to just one form of the disease.

A new study published online Sunday in Nature Genetics may signal a change in this trend. A team of researchers led by Thorunn Rafnar and Patrick Sulem of deCODE Genetics in Iceland describes how a SNP they originally found to be associated with the risk for developing basal cell carcinoma (BCC), a type of skin cancer, is also linked to increased odds for four other cancers.

In a study of more than 33,800 cancer patients and 45,800 controls, the scientists found that the C version of rs401681 is associated with increased odds of lung, bladder, prostate and cervical cancer, in addition to the previously found association with BCC. This variation decreases the odds of cutaneous melanoma, another type of skin cancer.

(23andMe customers can check their data for this SNP, rs401681, using the Browse Raw Data feature. A table at the end of this post provides details about its effect on different cancers).

The C version of rs401681 was also marginally, although not significantly, associated with increased odds of endometrial cancer and decreased odds of colorectal cancer.

There was no association of the SNP with cancer of the breast, kidney, stomach, thyroid, ovary or pancreas, nor with lymphoma, multiple myeloma or squamous cell carcinoma (a third type of skin cancer). The authors say that further investigation in even larger samples will be needed to determine if there truly is no association, or if they just haven’t picked it up yet.

An association was also found between rs2736098, a nearby SNP, and four of the five cancers that were associated with rs401681. 23andMe does not currently provide data for rs2736098.

Both SNPs are near a gene involved in maintaining the protective stretches of DNA attached to the ends of chromosomes called telomeres. The authors suggest that these SNPs, or other nearby variations, may lead to shortened telomeres, which are associated with several types of cancer.

Telomere length is determined in part by genetics, but environmental factors such as smoking and radiation can also shorten them. The authors note “four of the five cancers associated with the risk variants are cancer types that have strong environmental contributions to risk — smoking and occupational exposures for lung and bladder cancer, UV irradiation for BCC and infection with human papillomavirus for cervical cancer.” More research could help explain the exact relationship between the genetic variations found in this study and the environmental causes of these cancers.

Cancer Type Effect per C
Basal Cell Carcinoma 1.25
Lung Cancer 1.15
Bladder Cancer 1.12
Prostate Cancer 1.07
Cervical Cancer 1.31
Cutaneous Melanoma 0.88

*Effect is the increase or decrease in odds compared with someone with two copies of the T version of rs401681.

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