A New Field Could Hold the Key to Treating Both Cancer and Aging

Epigenetic therapeutics could revolutionize medicine in the coming decades. (© kentoh/Adobe)

(© kentoh/Adobe)

How exactly does your DNA make you who you are?

It's because of epigenetics that identical twins can actually look different and develop different diseases.

Just as software developers don't write apps out of ones and zeros, the interesting parts of the human genome aren't written merely in As, Ts, Cs and Gs. Yes, these are the fundamental letters that make up our DNA and encode the proteins that make our cells function, but the story doesn't end there.

Our cells possess amazing abilities, like eating invading bacteria or patching over a wound, and these abilities require the coordinated action of hundreds, if not thousands, of proteins. Epigenetics, the study of gene expression, examines how multiple genes work at once to make these biological processes happen.

It's because of epigenetics that identical twins – who possess identical DNA -- can actually look different and develop different diseases. Their environments may influence the expression of their genes in unique ways. For example, a research study in mice found that maternal exposure to a chemical called bisphenol A (BPA) resulted in drastic differences between genetically identical offspring. BPA exposure increased the likelihood that a certain gene was turned on, which led to the birth of yellow mice who were prone to obesity. Their genetically identical siblings who were not exposed to BPA were thinner and born with brown fur.

These three mice are genetically identical. Epigenetic differences, however, result in vastly different phenotypes.

(© 1994 Nature Publishing Group, Duhl, D.)

This famous mouse experiment is just one example of how epigenetics may transform medicine in the coming years. By studying the way genes are turned on and off, and maybe even making those changes ourselves, scientists are beginning to approach diseases like cancer in a completely new way.

With few exceptions, most of the 1 trillion cells that make up your body contain the same DNA instructions as all the others. How does each cell in your body know what it is and what it has to do? One of the answers appears to lie in epigenetic regulation. Just as everyone at a company may have access to all the same files on the office Dropbox, the accountants will put different files on their desktop than the lawyers do.

Our cells prioritize DNA sequences in the same way, even storing entire chromosomes that aren't needed along the wall of the nucleus, while keeping important pieces of DNA in the center, where it is most accessible to be read and used. One of the ways our cells prioritize certain DNA sequences is through methylation, a process that inactivates large regions of genes without editing the underlying "file" itself.

As we learn more about epigenetics, we gain more opportunities to develop therapeutics for a broad range of human conditions, from cancer to metabolic disorders. Though there have not been any clinical applications of epigenetics to immune or metabolic diseases yet, cancer is one of the leading areas, with promising initial successes.

One of the challenges of cancer treatments is that different patients may respond positively or negatively to the same treatment. With knowledge of epigenetics, however, doctors could conduct diagnostic tests to identify a patient's specific epigenetic profile and determine the best treatment for him or her. Already, commercial kits are available that help doctors screen glioma patients for an epigenetic biomarker called MGMT, because patients with this biomarker have shown high rates of success with certain kinds of treatments.

Other epigenetic advances go beyond personalized screening to treatments targeting the mechanism of disease. Some epigenetic drugs turn on genes that help suppress tumors, while others turn on genes that reveal the identity of tumor cells to the immune system, allowing it to attack cancerous cells.

Direct, targeted control of your epigenome could allow doctors to reprogram cancerous or aging cells.

The study of epigenetics has also been fundamental to the field of aging research. The older you get, the more methylation marks your DNA carries, and this has led to the distinction between biological aging, or the state of your cells, and chronological aging, or how old you actually are.

Just as our DNA can get miscopied and accumulate mutations, errors in DNA methylation can lead to so-called "epimutations". One of the big hypotheses in aging research today is that the accumulation of these random epimutations over time is responsible for what we perceive as aging.

Studies thus far have been correlative - looking at several hundred sites of epigenetic modifications in a person's cell, scientists can now roughly discern the age of that person. The next set of advances in the field will come from learning what these epigenetic changes individually do by themselves, and if certain methylations are correlated with cellular aging. General diagnostic terms like "aging" could be replaced with "abnormal methylation at these specific locations," which would also open the door to new therapeutic targets.

Direct, targeted control of your epigenome could allow doctors to reprogram cancerous or aging cells. While this type of genetic surgery is not feasible just yet, current research is bringing that possibility closer. The Cas9 protein of genome-editing CRISPR/Cas9 fame has been fused with epigenome modifying enzymes to target epigenetic modifications to specific DNA sequences.

A therapeutic of this type could theoretically undo a harmful DNA methylation, but would also be competing with the cell's native machinery responsible for controlling this process. One potential approach around this problem involves making beneficial synthetic changes to the epigenome that our cells do not have the capacity to undo.

Also fueling this frontier is a new approach to understanding disease itself. Scientists and doctors are now moving beyond the "one defective gene = one disease" paradigm. Because lots of diseases are caused by multiple genes going haywire, epigenetic therapies could hold the key to new types of treatments by targeting multiple defective genes at once.

Scientists are still discovering which epigenetic modifications are responsible for particular diseases, and engineers are building new tools for epigenome editing. Given the proliferation of work in these fields within the last 10 years, we may see epigenetic therapeutics emerging within the next couple of decades.

Timothy Chang And Lorena Lyon
Timothy Chang is a postdoctoral research fellow at Harvard Medical School. He received his Ph.D. in Bioengineering from the Georgia Institute of Technology in 2017, and B.S. in Chemical Biological Engineering from the Massachusetts Institute of Technology in 2012. Lorena Lyon is currently a digital production assistant at NOVA (PBS). She was formerly a research assistant at Harvard Medical School and graduated from Harvard College in 2018 with a degree in Human Developmental and Regenerative Biology. She is interested in work that meshes science and media. Tweet @renatyger.
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Kidney transplant patient Robert Waddell, center, with his wife and children after being off immunosuppresants; photo aken last summer in Perdido Key, FL. Left to right: Christian, Bailey, Rob, Karen (wife), Robby and Casey.

Photo courtesy Rob Waddell

Rob Waddell dreaded getting a kidney transplant. He suffers from a genetic condition called polycystic kidney disease that causes the uncontrolled growth of cysts that gradually choke off kidney function. The inherited defect has haunted his family for generations, killing his great grandmother, grandmother, and numerous cousins, aunts and uncles.

But he saw how difficult it was for his mother and sister, who also suffer from this condition, to live with the side effects of the drugs they needed to take to prevent organ rejection, which can cause diabetes, high blood pressure and cancer, and even kidney failure because of their toxicity. Many of his relatives followed the same course, says Waddell: "They were all on dialysis, then a transplant and ended up usually dying from cancers caused by the medications."

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Linda Marsa
Linda Marsa is a contributing editor at Discover, a former Los Angeles Times reporter and author of Fevered: Why a Hotter Planet Will Harm Our Health and How We Can Save Ourselves (Rodale, 2013), which the New York Times called “gripping to read.” Her work has been anthologized in The Best American Science Writing, and she has written for numerous publications, including Newsweek, U.S. News & World Report, Nautilus, Men’s Journal, Playboy, Pacific Standard and Aeon.

The White House in Washington, D.C.


This article is part of the magazine, "The Future of Science In America: The Election Issue," co-published by LeapsMag, the Aspen Institute Science & Society Program, and GOOD.

We invited Nobel Prize, National Medal of Science, and Breakthrough Prize Laureates working in America to offer advice to the next President on how to prioritize science and medicine in the next four years. Almost universally, these 28 letters underscore the importance of government support for basic or fundamental research to fuel long-term solutions to challenges like infectious diseases, climate change, and environmental preservation.

Many of these scientists are immigrants to the United States and emphasize how they moved to this country for its educational and scientific opportunities, which recently have been threatened by changes in visa policies for students and researchers from overseas. Many respondents emphasize the importance of training opportunities for scientists from diverse backgrounds to ensure that America can continue to have one of the strongest, most creative scientific workforces in the world.

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Aaron F. Mertz
Aaron F. Mertz, Ph.D., is a biophysicist, science advocate, and the founding Director of the Aspen Institute Science & Society Program, launched in 2019 to help foster a diverse scientific workforce whose contributions extend beyond the laboratory and to generate greater public appreciation for science as a vital tool to address global challenges. He completed postdoctoral training in cell biology at Rockefeller University, a doctorate in physics at Yale University, a master’s degree in the history of science at the University of Oxford as a Rhodes Scholar, and a bachelor’s degree in physics at Washington University in St. Louis.