Mary-Claire King and the secrets written in our DNA

When Mary-Claire King began her work in the 1970s, she wasn’t setting out to change the lives of millions of women. She was simply trying to solve a mystery. Why did breast cancer seem to strike generation after generation in some families, almost as if it were an heirloom no one wanted to inherit?

At a time when the prevailing belief was that cancer came from the environment, for example diet or exposure to certain chemicals. But King felt there was something deeper threading these stories together.

For nearly 20 years, she followed that instinct with stubborn determination. While raising a daughter as a single mother and navigating a male-dominated scientific world, she sifted through data from families devastated by breast cancer. Each pattern she uncovered brought her closer to a revelation that many doubted could exist.

While pancreatic cancer is the eighth most commonly diagnosed cancer in Australia, it’s estimated that it will be the third most common cause of death from cancer in 2025.

Finally, in 1990, King identified a gene on chromosome 17 that carried a terrible secret. A mutation in that gene, later named BRCA1, dramatically increased a woman’s chance of developing breast and ovarian cancers.

Her discovery reshaped medicine. But for Ashkenazi Jewish women, it presented something even more personal. Because of centuries of shared ancestry, three specific BRCA mutations were found to be far more common in Ashkenazi communities than anywhere else. What had once seemed like an inexplicable pattern of mothers, daughters, sisters and aunts diagnosed far too young suddenly had an explanation. King’s work gave those stories names, numbers and, most importantly, options.

But the narrative did not end with breast or ovarian cancer. As research continued, another shadow emerged. BRCA mutations, particularly BRCA2, were found to heighten the risk of pancreatic cancer — one of the most silent and devastating cancers. Among Ashkenazi Jews, that risk can be up to ten times higher than in the general population; even BRCA1 can double it.

In Australia, the statistics are sobering. Around 4,825 new cases of pancreatic cancer are estimated for 2025, and about 4,039 are estimated to die from it in that same year.

Survival remains low, with only about 14% of diagnosed individuals living five years or more. Importantly, while pancreatic cancer is the eighth most commonly diagnosed cancer in Australia, it’s estimated that it will be the third most common cause of death from cancer in 2025.

And alarmingly, there is no early detection test.

Which is why awareness has become an act of protection.

November marks Pancreatic Cancer Awareness Month, with World Pancreatic Cancer Day on November 20 inviting people worldwide to greet the organ most of us forget — “Hello Pancreas” — and acknowledge its quiet, essential work regulating digestion and blood sugar.

But the narrative did not end with breast or ovarian cancer. As research continued, another shadow emerged. BRCA mutations, particularly BRCA2, were found to heighten the risk of pancreatic cancer — one of the most silent and devastating cancers.

For the Ashkenazi community, King’s legacy now stretches further than even she imagined. Her discovery not only offers clarity about breast and ovarian cancer but casts crucial light on pancreatic cancer risk too, helping families understand how heritage and biology intertwine.

And for the many Ashkenazi Jews each year whose diagnoses intersect with this gene, Mary-Claire King’s determination may be the reason their stories do not end where they once might have.