Robert C. Green Chicago Tribune
When actor Chris Hemsworth, aka Thor, God of Thunder, agreed to host a National Geographic series about extending human lifespans, he didn’t expect to discover his own genetic risk. But that’s what happened when Hemsworth revealed on an episode of “Limitless” that he carries a common change in the APOE gene associated with an increased risk of Alzheimer’s disease.
Hemsworth almost chose to keep his discovery private, but ultimately decided to go public, a decision reminiscent of actress Angelina Jolie, who in 2013 revealed she carried a change in the gene called BRCA1 that confers high risk. for breast and ovaries. cancer. Jolie, another actor whose roles have included on-screen superheroes, chose to have harm-reduction surgeries and inspired many to undergo similar tests, and his example sparked wide discussion. on the power of genes to offer predictions about future cancer risk.
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Today, the complementary experiences of these two actors offer a chance to clarify some key principles around genetic testing for the public.
Genetics is not a crystal ball
Most genetic changes, including those discovered in Jolie and Hemsworth, do not guarantee that the individual will develop the disease.
For example, with the BRCA1 gene change she had, Jolie’s risk of breast cancer before surgery went from a lifetime risk of 13% to between 55% and 72%. With his changes to the APOE gene, Hemsworth’s risk of developing Alzheimer’s disease is higher than most, but by some estimates it’s still only 30-55%, so there’s still room for improvement. good chance he avoids this spell. Most genetic information helps estimate risk, but does not signal a predetermined outcome.
Treatable and incurable conditions
Some people want to “know it all”, but others only want to know genetic risk information if you can “do something about it”, by which they usually mean medical intervention to prevent or slow the disease by question.
In 2013, I helped create an official list of what are now 78 genes for “treatable” conditions that has become the basis for many screening programs using genetics. The APOE gene for Alzheimer’s disease risk is not on this list, but the BRCA1 gene is. So if people want to know their risk for treatable cancers, treatable heart disease, and other treatable possibilities, but prefer to avoid knowing their risk for incurable diseases like Alzheimer’s, this is an easy option.
Surprisingly, many people want to know their genetic status for incurable diseases like Alzheimer’s to plan their lives or to be on the front line for new clinical trials or treatments that may emerge in the future. The discovery of a personal genetic risk is less painful than one imagines and has the gift of galvanizing both passion and progress.
Popular direct-to-consumer genetic testing companies such as Ancestry or 23andMe are to be commended for demystifying and democratizing genetics using microchip technology that can detect some DNA changes but not others.
For example, 23andMe screens for the three most common genetic changes in breast and ovarian cancer, which have undoubtedly saved lives; but it does not report more than a thousand other such changes in the same genes. Newer gene sequencing technologies are more expensive but can read every letter of one or more genes, allowing the detection of many more people with changes that put them at risk for inherited forms of cancer and heart disease.
Genetic risk and longevity
The quest for greater longevity is making its way into our culture. Ironically, Hemsworth’s experience with genetics in the context of the National Geographic show “Limitless,” a show that highlights the physical challenges to fighting aging, reminds us of the underappreciated fact that all anti-ageing efforts -age must be anchored first in the prevention of premature diseases and avoidable death.
We have estimated that well over 2.5% of Americans carry genetic markers for elevated risks of cancer and treatable heart disease that are easily detectable by cost-effective medical sequencing. Yet physicians and healthcare systems have been slow to embrace preventive genomics because physicians are unsure about ordering and interpreting such tests and most proactive genetic testing is not yet reimbursed by health insurance. .
Hemsworth and Jolie play heroes in movies, but it takes exceptional courage in the real world to share their own health issues. Their generosity is accelerating awareness and acceptance of a future where we do not wait to respond to the ravages of so many diseases but rather anticipate, predict and prevent them through genomics.
Dr. Robert C. Green is a medical geneticist, physician-scientist, and professor of medicine at Harvard Medical School. He directs the Preventive Genomics Clinic at Mass General Brigham and the Precision Population Health Initiative at Ariadne Labs.