AsianScientist (Feb. 18, 2020) – Characterized by uncontrolled cell growth, cancer is one of the leading causes of death worldwide. Globally, one in five men and one in six women will develop cancer in their lifetime; lung cancer is most commonly diagnosed in men, while breast cancer is most common in women.
Predicting an individual’s cancer risk can go a long way towards detecting cancer early. At the Genome Institute of Singapore, Dr. Li Jingmei has spent the last ten years unravelling the genetics of breast cancer with the goal of improving how the risk score for breast cancer is calculated.
“Genetic markers for breast cancer can predict a woman’s future risk of developing the disease. It’s similar to knowing whether a person has a high genetic risk for high blood pressure. Clinicians can then direct the person to take measures to avoid disease onset, or detect the disease at an earlier stage where the patient will have a better chance of survival,” Li explained.
Currently, rare genetic variants in two genes—BRCA1 and BRCA2—are regarded as highly predictive of breast cancer risk. Li however noted that the relative rarity of these variants means that screening for them only benefits a small subset of women. She proposes that common variants of genes other than BRCA1 and BRCA2 matter as well in the calculation of breast cancer risk.
When screened for singly, common variants of a single gene are poor indicators of breast cancer risk. However, in a study conducted on 5,099 breast cancer patients, Li demonstrated that she could classify patients according to their risk profile by using 162 common variants analyzed in tandem. This is known as a polygenic risk score.
“For rare variants, you either have it or you don’t. But when you sum up the additive effects of multiple common variants, it’s no longer a ‘yes-or-no’ answer,” she quipped, adding that this finer-grained classification method could improve cancer detection.
In the study, she reported that a higher polygenic risk score was associated with less aggressive tumor characteristics, such as tumors being small in size and expressing markers that respond to hormonal treatments.
Importantly, her findings suggest that women with high polygenic risk scores are more likely to develop breast cancer, and that the cancer is likely to be detected by routine screening. Her research could therefore help refine and update official recommendations for how often women should get themselves checked for breast cancer.
Li also pointed out that genetic variation is not the only determining factor of an individual’s breast cancer risk. Epigenetics—the modification of gene expression independent of changes to the genetic code itself—can also influence the likelihood of a person contracting the disease.
“So my hope is that by combining [the polygenic risk score] with epigenetics data which incorporate effects of lifestyle and the environment, we can detect cancer early in a larger population and save lives,” she said.
Copyright: Asian Scientist Magazine.
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