Mary-Claire King had been handed a dose of scepticism from fellow researchers when she first set out to establish a genetic link to breast cancer more than four decades ago. When King began her research in 1974, most in the field were of the opinion that cancer was viral. Now a professor at the University of Washington, Kind persisted due to a "significant amount of statistical data" generated from around the world in the 1920's indicating that daughters of women whom died of breast cancer were more likely to develop and die from the disease themselves.
“The major challenge was that the technology at that time did not exist. It was caused by viruses. That’s true. But not all cancers are caused by viruses, and some cancers as we now know are in part a consequence of inherited mutation.”
King, who earned a bachelor's degree in mathematics at Carleton College in Minnesota later receiving her PhD in genetics from the University of California, Berkeley, using mathematics to see if there was a genetic model to test her own hypothesis.
King went on to study 1,500 families which were affected by breast cancer using a mathematical approach. She predicted clusters of cases could be best explained by the presence of a disease-linked gene in about 4% of families. She also predicted that risk of breast cancer among women carrying gene mutations was around 80% by age, the risk fell to 8% among women without them proving breast cancer risks are higher for women carrying gene mutations.
Yet still, scepticism pursued. Due to teh scepticism, King set out to show the existence of a breat cancer gene by locating it using linkage analysis. In 1990, the gene was mapped as human chromosome 17.
Now the American Cancer Society professor in the departments of medicine and genome sciences at the University of Washington, King explained her reasons for focusing on breast cancer:
It was therefore necessary to develop the technology – that is, to sequence the genomic regions – to learn the sequence of BRCA1. First, women can now learn, while they are still healthy, if they carry a mutation in BRCA1 or one of its sister genes, and if so, can take measures to prevent ovarian and breast cancer. Second, the discoveries of BRCA1 and BRCA2 enabled the development of chemotherapy targeted specifically to tumours.
Under the current international recommendations, women of age 40 or those whom have finished having children should have their ovaries as well as fallopian tubes removed to help reduce the risks of ovarian and breast cancer.
King believes 15% of breast cancer cases involving Chinese women were inherited, comparable to the numbers of their Western counterparts. An improved nutrition ensures women enter puberty at an earlier age, whilst better education is tied to many postponing having children.
Breast cancer is now increasing very rapidly in China and in Hong Kong. This is not for genetic reasons. This is because the principal risk factors for breast cancer are now much more prevalent in China than they were in my generation.
King also gave time to young girls looking to get into mathematics and science:
Give young girls confidence in themselves. Schools and teachers are important, but fathers and mothers are extremely important for a girl to have confidence that she can do mathematics while she’s still very small. Every game he would make up problems and he would teach me the answers and say, ‘That was very good. I will give you a harder problem’,” she said. “So I grew up always assuming that this was something that you did with your dad.