Corporate Banner
Satellite Banner
Scientific Community
Become a Member | Sign in
Home>News>This Article

Fast Way to Measure DNA Repair

Published: Tuesday, April 22, 2014
Last Updated: Thursday, April 24, 2014
Bookmark and Share
Test analyzing cells’ ability to fix different kinds of broken DNA could help doctors predict cancer risk.

Our DNA is under constant attack from many sources, including environmental pollutants, ultraviolet light, and radiation. Fortunately, cells have several major DNA repair systems that can fix this damage, which may lead to cancer and other diseases if not mended.

The effectiveness of these repair systems varies greatly from person to person; scientists believe that this variability may explain why some people get cancer while others exposed to similar DNA-damaging agents do not. A team of MIT researchers has now developed a test that can rapidly assess several of these repair systems, which could help determine individuals’ risk of developing cancer and help doctors predict how a given patient will respond to chemotherapy drugs.

The new test, described in the Proceedings of the National Academy of Sciences the week of April 21, can analyze four types of DNA repair capacity simultaneously, in less than 24 hours. Previous tests have been able to evaluate only one system at a time.

“All of the repair pathways work differently, and the existing technology to measure each of those pathways is very different for each one. It takes expertise, it’s time-consuming, and it’s labor-intensive,” says Zachary Nagel, an MIT postdoc and lead author of the PNAS paper. “What we wanted to do was come up with one way of measuring all DNA repair pathways at the same time so you have a single readout that’s easy to measure.”

The research team, led by professor Leona Samson, used this approach to measure DNA repair in a type of immortalized human blood cells called lymphoblastoid cells, taken from 24 healthy people. They found a huge range of variability, especially in one repair system where some people’s cells were more than 10 times more efficient than others.

“None of the cells came out looking the same. They each have their own spectrum of what they can repair well and what they don’t repair well. It’s like a fingerprint for each person,” says Samson, who is the Uncas and Helen Whitaker Professor, an American Cancer Society Professor, and a member of MIT’s departments of biological engineering and of biology, Center for Environmental Health Sciences, and Koch Institute for Integrative Cancer Research.
Measuring repair

With the new test, the MIT team can measure how well cells repair the most common DNA lesions, including single-strand breaks, double-strand breaks, mismatches, and the introduction of alkyl groups caused by pollutants such as fuel exhaust and tobacco smoke.

To achieve this, the researchers created five different circular pieces of DNA, four of which carry a specific type of DNA damage, also called DNA lesions. Each of these circular DNA strands, or plasmids, also carries a gene for a different colored fluorescent protein. In some cases, the DNA lesions prevent those genes from being expressed, so when the DNA is successfully repaired, the cell begins to produce the fluorescent protein. In others, repairing the DNA lesion turns the fluorescent gene off.

By introducing these plasmids into cells and reading the fluorescent output, scientists can determine how efficiently each kind of lesion has been repaired. In theory, more than five plasmids could go into each cell, but the researchers limited each experiment to five reporter plasmids to avoid potential overlap among colors. To overcome that limitation, the researchers are also developing an alternative tactic that involves sequencing the messenger RNA produced by cells when they copy the plasmid genes, instead of measuring fluorescence.

In this paper, the researchers tested the sequencing approach with just one type of DNA repair, but it could allow for unlimited tests at one time, and the researchers could customize the target DNA sequence to reveal information about which type of lesion the plasmid carries, as well as information about which patient’s cells are being tested. This would provide the ability for many different patient samples to be tested in the same batch, making the test more cost-effective.
Making predictions

Previous studies have found that many different types of DNA repair capacity can vary greatly among apparently healthy individuals. Some of these differences have been linked with cancer vulnerability; for example, a genetic defect in a type of DNA repair called nucleotide excision repair often leads to a condition called xeroderma pigmentosum, in which DNA damage caused by ultraviolet light goes unrepaired and leads to skin cancer.

Scientists have also identified links between DNA repair and neurological, developmental, and immunological disorders, but useful predictive DNA-repair-based tests have not been developed, largely because it has been impossible to rapidly analyze several different types of DNA repair capacity at once.

Samson’s lab is now working on adapting the new test so it can be used with blood samples taken from patients, allowing researchers to identify people who are at higher risk and potentially enabling prevention or earlier diagnosis of diseases linked to DNA repair. Such a test could also be used to predict patients’ response to chemotherapy drugs, which often work by damaging cancer cells’ DNA, or to determine how much radiation treatment a patient can tolerate.

The researchers also believe this test could be exploited to screen for new drugs that inhibit or enhance DNA repair. Inhibitors could be targeted to tumors to make them more susceptible to chemotherapy, while enhancers could help protect people who have been accidentally exposed to DNA-damaging agents, such as radiation.

Another important application for this test could be studying fundamental biological processes such as how cells recruit backup repair systems to fill in when another pathway is overwhelmed, says Samuel Wilson, a principal investigator at the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health (NIH).

“There’s an opportunity to use these multiplexed plasmids in biological assays where several repair pathways can be probed at the same time, offering a very advanced tool to allow us to make much better interpretations about the repair status of a cell,” says Wilson, who was not part of the research team.

Graduate students Carrie Margulies and Isaac Chaim; technical assistants Siobhan McRee and Patrizia Mazzucato; and research scientists Vincent Butty, Anwaar Ahmad, Ryan Abo, and Anthony Forget also contributed to the research, which was funded by the NIH and NIEHS.

Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,600+ scientific posters on ePosters
  • More than 3,800+ scientific videos on LabTube
  • 35 community eNewsletters

Sign In

Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Scientific News
Chromosomal Chaos
Penn study forms basis for future precision medicine approaches for Sezary syndrome
Genetic Defences of Bacteria Don’t Aid Antibiotic Resistance
Genetic responses to the stresses caused by antibiotics don’t help bacteria to evolve a resistance to the medications, according to a new study by Oxford University researchers.
Tolerant Immune System Increases Cancer Risk
Researchers have found that individuals with high immunoCRIT ratios may have an increased risk of developing certain cancers.
Developing a Gel that Mimics Human Breast for Cancer Research
Scientists at the Universities of Manchester and Nottingham have been funded to develop a gel that will match many of the biological structures of human breast tissue, to advance cancer research and reduce animal testing.
Lung Repair and Regeneration Gene Discovered
New role for hedgehog gene offers better understanding of lung disease.
3 Ways Viruses Have Changed Science for the Better
Viruses are really good at what they do, and we’ve been able to harness their skills to learn about – and potentially improve – human health in several ways.
Mixed Up Cell Transportation Key Piece of ALS and Dementia Puzzle
Researchers from the University of Toronto are one step closer to solving this incredibly complex puzzle, offering hope for treatment.
New Gene Therapy for Vision Loss From a Mitochondrial Disease
NIH-funded study shows success in targeting mitochondrial DNA in mice.
Five New Genetic Variants Linked to Brain Cancer Identified
The biggest ever study of DNA from people with glioma – the most common form of brain cancer – has discovered five new genetic variants associated with the disease.
Predictive Model for Breast Cancer Progression
Biomedical engineers have demonstrated a proof-of-principle technique that could give women and their oncologists more personalized information to help them choose options for treating breast cancer.
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,600+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
3,800+ scientific videos