Should you get sequenced? Not all bad genes predict disease
For NBC News chief medical editor Dr. Nancy Snyderman, having a “boring genome,” is a good problem to have. Snyderman revealed a snapshot of her genetic code on TODAY Wednesday, after having two types of genetic testing.
The first, a whole genome sequencing test by Illumina, costs about $5,000. She now has the complete results from it stored on her iPad. "What’s fascinating ... is that this is me, right here on a tablet,” Snyderman said. “And as we learn more about what genes underlie specific diseases, I’ll have this as a reference.”
She also took the commercial test 23andMe, which costs about $99 and reveals a limited amount of information. Snyderman recruited her parents, siblings and children to get genotyped by the 23andMe DNA test.
Her experiment is an example of how scientists are increasingly integrating genome sequencing into the practice of medicine.
The human genome is the blueprint or map of a person’s unique combination of three million base pairs of DNA, the building blocks of every cell in the human body. In April 2003 scientists accomplished a milestone by completing The Human Genome Project. The map has laid the foundation for a decade of significant strides in genetic research, propelling this sophisticated science beyond the lab and into the doctor’s office.
The initial human genome project cost billions of dollars, but today private DNA sequencing companies like Illumina can sequence someone's entire genome for around $5,000. The data reveals mutations for conditions and diseases for which there are known genetic markers.
“The price has come down by over a factor of a thousand over the last five or six years,“ says company CEO Jay Flatley. He expects the price of sequencing to continue to drop as use of genome sequencing becomes more widespread.
How does it work? Each human cell contains two sets of the chromosomes that carry DNA - one inherited from the mother and another from the father. Cells in the blood or taken from a cheek swab can provide a good sample. According to Illumina’s website, patients typically get results back in fewer than 90 days.
Who should get sequenced?
Not every physician excited by genetic medicine is ready for genome sequencing to go mainstream. “I don’t think people who are healthy should generally get sequenced at this juncture,” says Scripps Health cardiologist Dr. Eric Topol. “But if you have a new diagnosis of cancer, that’s a really good time to get sequenced to get the right therapies matching up with the root cause.”
Scientists hope that a greater understanding of the genetic underpinnings of disease can lead to earlier diagnosis and better treatment.
Dr. Robert Green is a medical geneticist at Brigham and Women’s Hospital and Harvard Medical School. Like Topol, he’s optimistic about genetic medicine but says he wants to move the ball forward in a responsible way.
“As we roll out genomic medicine we are fighting against this society-wide misconception that having the bad gene means you’re going to get the disease. That’s only true in a very few cases,” Green said.
In April, Green and colleagues advised the American College of Medical Genetics and Genomics on which genetic risk factors that turn up on genetic tests should be reported to doctors who treat patients. They came up with 24 disease categories that mostly include genes that predispose to either cancer or heart conditions that have known medical treatments.
Green says more studies are needed that follow patients to see whether they benefit from genomic medicine. He is the principal investigator of a NIH funded research project called MedSeq which is analyzing the use of whole-genome sequencing in the practice of medicine. His team asks: how does genetic information get used by doctors, how do doctors deal with the risk information they receive and how do the patients deal with it?
“What we really don’t know yet is whether the predictive aspects of the genome are going to turn out to be beneficial or potentially harmful,” Green says.
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According to a recent survey conducted by 23andMe, 90 percent of Americans believe that knowing their personal genetic information could be helpful in managing their health.
“It’s important for you to actually own your own data and be able to give it to your physician, give it to your insurance company, give it to others as you want,” says 23andMe CEO Anne Wojcicki, whose husband is Google cofounder Sergey Brin. "But it’s important for you to own it first.”
Rather than sequencing entire genomes, her company analyzes segments of DNA in saliva samples to look for known genetic markers of disease. The test includes approximately 250 reports about drug reactions, inherited traits and ancestry. It can detect genetic mutations for cystic fibrosis, sickle cell anemia, Tay-Sachs disease, and even BRCA1 and BRCA2 – two important mutations that increase the chance of developing breast and ovarian cancer. Snyderman tested negative for BRCA1 and BRCA2, but 23andMe doesnt' test for all the cancer-causing mutations in BRCA.
While “it doesn’t mean there won’t be breast cancer in this family – the real strong genetic hits for [the disease] … we didn’t get," Snyderman says.
People have to give extra consent to see the results for Alzheimer’s and Parkinson’s Disease because of the impact it can have on a person to know he or she may develop an incurable disease. It is also a reminder of the importance of discussing findings with a health professional. Wojcicki told NBC News, “Fundamentally you need to take that data and either go to a genetic counselor or go to your physician.”
For 23andMe customer Jim Shuma, the information from his genetic testing proved invaluable. The 33 year-old software engineer lost his father to heart disease at the age of 51. After his father’s death, Shuma ordered a 23andMe kit and learned he had a mutation in a gene that helps control production of a type of cholesterol called lipoprotein A (LPA).
Armed with this information along with his family history, Shuma convinced his cardiologist to run a unique blood test for LPA. An LPA level above 75 is considered dangerous. Shuma’s LPA was 384. “I wouldn’t have had a clue what to do about this if I didn’t have 23andMe to say where the problem is,” Shuma says.
Shuma’s physicians immediately suggested cholesterol-lowering drugs. Within a month, his LPA levels were cut in half, putting him at a much lower risk of heart disease. Shuma says he had lived a healthful lifestyle with good nutrition and plenty of exercise, but that his 23andMe results make him feel like he dodged a bullet. "Everyone ought to know where the deck is stacked against them," he says.
Kerri Zimmer and Nikita Japra contributed to this reporting.