Understanding why some mutations impair normal bodily functions and contribute to cancer may lead to new clinical laboratory diagnostics
New insight into the human genome may help explain the ageing process and provide clues to improving human longevity that can be useful to clinical laboratories and researchers developing cancer diagnostics. A recent study conducted at the Wellcome Sanger Institute in Cambridge, United Kingdom, suggests that the speed of DNA errors in genetic mutations may play a critical role in the lifespan and survival of a species.
To perform their research, the scientists analyzed genomes from the intestines of 16 mammalian species looking for genetic changes. Known as somatic mutations, these mutations are a natural process that occur in all cells during the life of an organism and are typically harmless. However, some somatic mutations can impair the normal function of a cell and even play a role in causing cancer.
“Aging is a complex process, the result of multiple forms of molecular damage in our cells and tissues. Somatic mutations have been speculated to contribute to ageing since the 1950s, but studying them had remained difficult,” said Inigo Martincorena, PhD (above), Group Leader, Sanger Institute and one of the authors of the study. Greater understanding of the role DNA mutations play in cancer could lead to new clinical laboratory tools and diagnostics. (Photo copyright: Wellcome Sanger Institute.)
Lifespans versus Body Mass
The mammalian subjects examined in the study incorporated a wide range of lifespans and body masses and included humans, giraffes, tigers, mice, and the highly cancer-resistant naked mole-rat. The average number of somatic mutations at the end of a lifespan was around 3,200 for all the species studied, despite vast differences in age and body mass. It appears that species with longer lifespans can slow down their rate of genetic mutations.
The average lifespan of the humans used for the study was 83.6 years and they had a somatic mutation rate of 47 per year. Mice examined for the research endured 796 of the mutations annually and only lived for 3.7 years.
Species with similar amounts of the mutations had comparable lifespans. For example, the small, naked mole-rats analyzed experienced 93 mutations per year and lived to be 25 years of age. On the other hand, much larger giraffes encountered 99 mutations each year and had a lifespan of 24 years.
“With the recent advances in DNA sequencing technologies, we can finally investigate the roles that somatic mutations play in ageing and in multiple diseases,” said Inigo Martincorena, PhD, Group Leader, Sanger Institute, one of the authors of the study in a press release. He added, “That this diverse range of mammals end their lives with a similar number of mutations in their cells is an exciting and intriguing discovery.”
The scientists analyzed the patterns of the mutations and found that the somatic mutations accumulated linearly over time. They also discovered that the mutations were caused by similar mechanisms and the number acquired were relatively similar across all the species, despite a difference in diet and life histories. For example, a giraffe is typically 40,000 times larger than a mouse, but both species accumulate a similar number of somatic mutations during their lifetimes.
“The fact that differences in somatic mutation rate seem to be explained by differences in lifespan, rather than body size, suggests that although adjusting the mutation rate sounds like an elegant way of controlling the incidence of cancer across species, evolution has not actually chosen this path,” said Adrian Baez-Ortega, PhD, postdoctoral researcher at the Sanger Institute and one of the paper’s authors, in the press release.
“It is quite possible that every time a species evolves a larger size than its ancestors—as in giraffes, elephants, and whales—evolution might come up with a different solution to this problem. We will need to study these species in greater detail to find out,” he speculated.
Why Some Species Live Longer than Others
The researchers also found that the rate of somatic mutations decreased as the lifespan of each species increased which suggests the mutations have a likely role in ageing. It appears that humans and animals perish after accumulating a similar number of these genetic mutations which implies that the speed of the mutations is vital in ascertaining lifespan and could explain why some species live substantially longer than others.
“To find a similar pattern of genetic changes in animals as different from one another as a mouse and a tiger was surprising. But the most exciting aspect of the study has to be finding that lifespan is inversely proportional to the somatic mutation rate,” said Alex Cagan, PhD, Postdoctoral Fellow at the Sanger Institute and one of the authors of the study in the press release.
“This suggests that somatic mutations may play a role in ageing, although alternative explanations may be possible. Over the next few years, it will be fascinating to extend these studies into even more diverse species, such as insects or plants,” he noted.
Benefit of Understanding Ageing and Death
The scientists believe this study may provide insight to understanding the ageing process and the inevitability and timing of death. They surmise that ageing is likely to be caused by the aggregation of multiple types of damage to the cells and tissues suffered throughout a lifetime, including somatic mutations.
Some companies that offer genetic tests claim their products can predict longevity, despite the lack of widely accepted evidence that such tests are accurate within an acceptable range. Further research is needed to confirm that the findings of the Wellcome Sanger Institute study are relevant to understand the ageing process.
If the results are validated, though, it is probable that new direct-to-consumer (DTC) genetic tests will be developed, which could be a new revenue source for clinical laboratories.
Citizens claiming racial diversity increased by 276% in the 2020 census, leading experts to wonder if racial diversity is increasing or if people are simply electing to identify as such and how this trend will affect healthcare
Once again, we see another unexpected consequence to expanded DNA testing done by consumers for their own interests and needs. As NPR recently reported in “The Census Has Revealed a More Multiracial US. One Reason? Cheaper DNA Tests,” the growing trend of ordering low-cost direct-to-consumer (DTC) genetic testing to identify cultural heritage (where a family came from) and genealogy (to connect with extant family members) has educated healthcare consumers more about their cultural roots.
Such knowledge, NPR speculates, is allowing people to complete their census survey with more accurate “heritage” classifications.
The last US census showed an interesting change compared to previous census surveys. More Americans identified themselves as racially diverse than in previous censuses. Scientists in multiple specialty areas—including demographics, sociology, genetics, and more—are asking why.
According to federal Census Bureau data, in the most recent census, people who identify as more than one race rose by 276%! Scientists are only just beginning to hypothesize the reasons for this increase, but three potential factors, NPR reported, have emerged:
More children are being born to parents who identify with racial groups that are different from one another.
People are reconsidering what they want the government to know about their identities, according to Duke University Press.
The increased incidence of DNA testing for cultural heritage may be an additional factor in the different ways people identified themselves during the census, driving its popularity, NPR noted. More people are purchasing at-home DNA tests to learn where their ancestors lived and came from, and their family’s genealogy.
“Exactly how big of an effect these tests had on census results is difficult to pin down,” NPR reported. “But many researchers agree that as the cost of at-home kits fell in recent years, they have helped shape an increasing share of the country’s ever-changing ideas about the social construct that is race.”
How the Census Alters Government Policy
Pew Research noted that, although only about 16% of Americans have taken an ancestry DNA test, the marketing efforts of “companies such as 23andMe and Ancestry.com, which operates the AncestryDNA service, should not be underestimated,” NPR reported. They have a wide reach, and those efforts could be impacting how people think about race and ethnic identity.
For most of human history, social experience and contemporary family history have been the drivers of how people identified themselves. However, low-cost DTC genetic testing may be changing that.
“The public has kind of taken in the notion that you can find out ‘who you are’ with a test that’s supposed to analyze your genes,” Jenifer Bratter, PhD (above), a Professor of Sociology at Rice University who studies multiracial identity, told NPR. “What that does for anyone who does work in racial identity and racial demography is cause us to think through how genetic ideas of race are in public circulation.” Desire by healthcare consumers to know their risk for chronic disease has already driven a marked increase in demand for low-cost DNA testing, which has also affected the types of test orders clinical laboratory are receiving from doctors. (Photo copyright: Rice University.)
One concern that sociologists and demographers have about this trend is that the US census is an important tool in policy, civil rights protections, and even how researchers measure things like healthcare access disparities.
“You’re going to have a lot more people who are not part of marginalized groups in terms of their social experiences claiming to be part of marginalized groups. When it comes to understanding discrimination or inequality, we’re going have very inaccurate estimates,” says Wendy Roth, PhD, Associate Professor of Sociology, University of Pennsylvania, told NPR.
They developed the “genetic options” theory, “to account for how genetic ancestry tests influence consumers’ ethnic and racial identities.” They wrote, “The rapid growth of genetic ancestry testing has brought concerns that these tests will transform consumers’ racial and ethnic identities, producing “geneticized” identities determined by genetic knowledge.”
However, a more healthcare-related motivation for taking a DTC DNA test is to learn about one’s potential risks for familial chronic health conditions, such as cancer, heart disease, and diabetes, etc.
“Whether that occurs through your primary care doctor, your large integrated health network, or your payor, I think there will be profound changes in society’s tolerance for using genetics for prevention,” he told GenomeWeb.
Regardless, as Dark Daily reported in 2020, sales of genetic tests from Ancestry and 23andMe show the market is cooling. Thus, with less than 20% of the population having taken DNA tests, and with sales slowing, genetics testing may not affect responses on the next US census, which is scheduled for April 1, 2030.
In the meantime, clinical laboratory managers should recognize how and why more consumers are interested in ordering their own medical laboratory tests and incorporate this trend into their lab’s strategic planning.
By offering DTC preventative gene sequencing, hospital leaders
hope to help physicians better predict cancer risk and provide more accurate
diagnoses
Two Boston health systems, Brigham and Women’s Hospital and Massachusetts General Hospital (MGH), are the latest to open preventative gene sequencing clinics and compete with consumer gene sequencing companies, such as 23andMe and Ancestry, as well as with other hospital systems that already provide similar services.
This may provide opportunities for clinical laboratories. However, some experts are concerned that genetic sequencing may not be equally available to patients of all socioeconomic classes. Nor is it clear how health systems plan to pay for the equipment and services, since health insurance companies continue to deny coverage for “elective” gene sequencing, or when there is not a “clear medical reason for it, such as for people with a long family history of cancer,” notes STAT.
Therefore, not everyone is convinced of the value of gene sequencing to either patients or hospitals, even though advocates tout gene sequencing as a key element of precision medicine.
Is Preventative Genetic Sequencing Ready for the Masses?
Brigham’s Preventive Genomics Clinic offers comprehensive DNA sequencing, interpretation, and risk reporting to both adults and children. And MGH “plans to launch its own clinic for adults that will offer elective sequencing at a similar price range as the Brigham,” STAT reported.
The Brigham and MGH already offer similar gene sequencing services as other large health systems, such as Mayo Clinic and University of California San Francisco (UCSF), which are primarily used for research and cancer diagnoses and range in price depending on the depth of the scan, interpretation of the results, and storage options.
However, some experts question whether offering the
technology to consumers for preventative purposes will benefit anyone other
than a small percentage of patients.
“It’s clearly not been demonstrated to be cost-effective to promote this on a societal basis,” Robert Green, MD, MPH, medical geneticist at Brigham and Women’s Hospital, and professor of genetics at Harvard, told STAT. “The question that’s hard to answer is whether there are long-term benefits that justify those healthcare costs—whether the sequencing itself, the physician visit, and any downstream testing that’s stimulated will be justified by the situations where you can find and prevent disease.”
Additionally, large medical centers typically charge more
for genomic scans than consumer companies such as 23andMe and Ancestry. Hospital-based
sequencing may be out of the reach of many consumers, and this concerns some
experts.
“The idea that genomic sequencing is only going to be
accessible by wealthy, well-educated patrons who can pay out of pocket is
anathema to the goals of the publicly funded Human Genome Project,” Jonathan
Berg, MD, PhD, Genetics Professor, University of North Carolina at Chapel
Hill, told Scientific
American.
And, according to the American Journal of Managed Care, “It’s estimated that by 2021, 100 million people will have used a direct-to-consumer (DTC) genetic test. As these tests continue to gain popularity, there is a need for educating consumers on their DTC testing results and validating these results with confirmatory testing in a medical-grade laboratory.”
This is why it’s critical that clinical laboratories and
anatomic pathology groups have a genetic testing and gene sequencing strategy,
as Dark
Daily reported.
David Bick, MD, Chief Medical Officer at the HudsonAlpha Institute for Biotechnology and Medical Director of the Smith Family Clinic for Genomic Medicine, told Scientific American, “there’s just more and more interest from patients and families not only because of 23andMe and the like, but because there’s just this understanding that if you can find out information about your health before you become sick, then really our opportunity as physicians to do something to help you is much greater.”
In an article he penned for Medium, Robert Green, MD, MPH (shown above counseling a patient), medical geneticist at Brigham and Women’s Hospital and professor of genetics at Harvard, wrote, “The ultimate aim of our Genomes2People Research Program is to contribute to the transformation of medicine from reactive to proactive, from treatment-oriented to preventive. We are trying to help build the evidence base that will justify societal decision to make these technologies and services accessible to anyone who wants them, regardless of means, education or race and ethnicity.” (Photo copyright: Wall Street Journal.)
Is Preventative Genomics Elitist?
As large medical centers penetrate the consumer genetic
testing market some experts express concerns. In a paper he wrote for Medium,
titled, “Is Preventive Genomics Elitist?” Green asked, “Is a service like this
further widening the inequities in our healthcare system?”
Green reported that while building the Preventive Genomics Clinic at Brigham, “we … struggled with the reality that there is no health insurance coverage for preventive genomic testing, and our patients must therefore pay out of pocket. This is a troubling feature for a clinic at Brigham and Women’s Hospital, which is known for its ties to communities in Boston with diverse ethnic and socioeconomic backgrounds.”
Most of Brigham’s early genetics patients would likely be “well-off,
well-educated, and largely white,” Green wrote. “This represents the profile of
typical early adopters in genetic medicine, and in technology writ large. It
does not, however, represent the Clinic’s ultimate target audience.”
More Data for Clinical Laboratories
Nevertheless, preventive genomics programs offered by large
health systems will likely grow as primary care doctors and others see evidence
of value.
Therefore, medical laboratories that process genetic
sequencing data may soon be working with growing data sets as more people reach
out to healthcare systems for comprehensive DNA sequencing and reporting.
