What Is CRISPR?

It might sound like something you’d find in the grocery store between the potato chips and cheese puffs, but CRISPR is state-of-the-art medicine. It might one day help cure conditions from cystic fibrosis to lung cancer.

CRISPR isn’t a drug. It’s a technique. The goal is to cut out and fix glitches in your genes that threaten your health. Although it’s not the first gene-editing method scientists have tried, it’s the simplest, fastest, and most accurate. And that makes it a game-changer.

'CRISPR' Defined

CRISPR is short for “clustered regularly interspaced short palindromic repeat.” It’s a bit of DNA that scientists first noticed it in bacteria’s immune systems. That inspired the gene-editing technique that everyone now calls CRISPR.

Those bacteria use CRISPR like a “Most Wanted” list. When a virus attacks, the bacteria memorize the virus’s DNA and file its profile in their CRISPR. If that same virus attacks again later on, the bacteria pull up its file in CRISPR and copy it. That copy acts like an assassin: It hunts down the virus and cuts its DNA to destroy it.

Now, researchers use the same CRISPR strategy to take on threats like diseases. CRISPR can turn genes on or off, or make them work in a different way, to protect your health.

For example, think of someone who was born with a gene mistake that gave them a rare illness. Or a gene change that happens later in life and puts you at risk for cancer. Scientists want to be able to load those flaws into CRISPR, cut out the DNA flaw, and fix it.

How? The basic idea would be to take some cells from a patient, edit them using CRISPR and grow more of them, and then inject them back into the patient. It sounds like a simple idea, but doing it on a large scale is hard. Scientists have also worked on other gene-editing techniques besides CRISPR.

How Might It Help With Cancer?

There are lots of types of cancer, and they all are linked to problems in genes. So CRISPR holds promise, though there are no treatments or cures yet.

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Much of the research so far focuses on immunotherapy, which taps your body’s immune system to fight cancer. There are different ways to do this, such as:

Attacking the cancer. Some scientists have used CRISPR to supercharge the immune system’s T cells. In lab tests, CRISPR researchers edited T cells so they would recognize cancer. The edited T cells then killed cancer cells.

Turning off cancer’s defenses. T cells aren’t supposed to attack normal cells. Healthy cells use certain proteins, including one called PD-1, as a sign for T cells to avoid. It’s like saying, “Everything’s OK here. No T cells needed.”

But some cancer cells have PD-1, even though they’re not healthy. It’s like having a fake ID that keeps T cells away and lets the cancer grow. In an experiment, scientists used CRISPR to turn off the gene that makes PD-1. And just like that, T cells attacked cancer cells.

Slowing down cancer. Another lab used CRISPR to change genes in cancer cells. By doing that, they slowed down how fast the cancer could spread.

That’s just a small sampling of studies. It’s a long road from lab tests to safe, effective treatments. Small trials with people are just getting started, and it may take years before it’s widely available.

The first trial in people is underway in China. It’s focusing on an aggressive form of non-small-cell lung cancer. That trial will take until April 2018.

The first CRISPR trial to be approved in the U.S hasn’t started yet. Doctors at the University of Pennsylvania will include 18 people with various cancers. The researchers will take a sample of the patients’ T cells, use CRISPR to make three edits, and inject the edited T cells back into the patients. The goal of that trial is to see if the process is safe, not how well it works as a treatment.

Can It Help With Other Diseases?

Scientists are studying CRISPR for many conditions, including high cholesterol, HIV, and Huntington’s disease. Researchers have also used CRISPR to cure muscular dystrophy in mice.

Most likely, the first disease CRISPR helps cure will be caused by just one flaw in a single gene, like sickle cell disease. There aren’t a lot of those conditions -- many diseases involve a lot of genes -- but they might be the easiest to tackle.

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What Are the Risks?

When you’re talking about changing DNA, which is the genetic coding that affects everything from your eye color to your odds of having a heart attack, it raises big questions. Those issues include the ethics of tweaking DNA and what could go wrong.

There are some strict limits already. For instance, editing DNA in sperm or eggs (also called “germline cells”) would create changes that would get passed on to the next generation. That would have far-reaching effects. So that kind of research is banned in more than 40 countries, including the U.S.

CRISPR is effective, but it’s not perfect. There’s a chance that it could accidentally edit very similar DNA that’s not its target. And because even a minor change in DNA can have big impacts, researchers need to use a lot of caution.

Scientists don’t yet know what all CRISPR’s side effects may be. But its revolutionary potential means that you’ll probably see CRISPR in the news for a long time to come.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on September 02, 2017

Sources

SOURCES:

Harvard Health Publications, Harvard Medical School: “Whatever Happened to CRISPR?”

U.S. National Library of Medicine: “Gene editing using CRISPR-Cas9 for Treatment of Lung Cancer,” “Treatment of Dyslipidemia Using CRISPR/Cas9 Genome Editing.”

NIH, U.S. National Library of Medicine, Genetics Home Reference: “What is a gene?” “Is eye color determined by genetics?”

NIH, National Cancer Institute: “Researchers Use CRISPR Gene-Editing Tool to Help Turn Immune Cells against Tumors.”

Harvard University, The Graduate School of Arts and Sciences: “CRISPR: A game-changing genetic engineering technique,” “Is Genetic Surgery in My Future?: A conversation with Dr. John Doench about CRISPR and genome editing.”

American Heart Association: “Understand Your Risks to Prevent a Heart Attack.”

Cancer Research UK: “9 burning questions about CRISPR genome editing answered.”

Canadian Cancer Society: “CRISPR gene-editing trial tests new way to treat cancer.”

Cardiff University: “T-cell Modulation Group.”

University of Rochester Medical Center: “Study: A New Way to Slow Cancer Cell Growth.”

The Journal of Clinical Investigation: “CRISPR/Cas9-mediated gene editing ameliorates neurotoxicity in mouse model of Huntington’s disease.”

YourGenome.org: “What is CRISPR-Cas9?”

Center for Genetics and Society: “About Human Germline Gene Editing.”

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