Featured Research

from universities, journals, and other organizations

Cancer: Some cells don't know when to stop

Date:
November 19, 2012
Source:
University of Southern California
Summary:
Certain mutated cells keep trying to replicate their DNA -- with disastrous results -- even after medications rob them of the raw materials to do so, according to new research.

New imaging techniques allowed scientists to see for the first time that while chemotherapy drugs shut down the DNA replication process of most cancer cells, so-called “checkpoint mutants” just keep chugging along, unwinding the DNA and creating damaged DNA strands that can result in the kind of abnormalities seen in cancer cells.
Credit: Image courtesy of University of Southern California

Certain mutated cells keep trying to replicate their DNA -- with disastrous results -- even after medications rob them of the raw materials to do so, according to new research from USC.

New imaging techniques allowed scientists to see for the first time that while chemotherapy drugs shut down the DNA replication process of most cancer cells, so-called "checkpoint mutants" just keep chugging along, unwinding the DNA and creating damaged DNA strands that can result in the kind of abnormalities seen in cancer cells.

"Older methods suggested that these checkpoint mutants stopped replicating and that the replication machinery simply fell apart to cause DNA damage," said Susan Forsburg, professor of molecular biology at the USC Dornsife College of Letters, Arts and Sciences. "Our new technique suggests that replication processes continue and actively contribute to the damage."

Forsburg is the corresponding author on a paper about the discovery that was published online in Molecular & Cellular Biology in October. She collaborated with lead author Sarah Sabatinos, a postdoctoral research associate at USC, and Marc Green, a research technician.

The team used a common chemotherapy drug to put stress on fission yeast cells while they were going through the DNA replication process. The drug starves cells for nucleotides, which are the molecules that cells use to build DNA strands.

Previous studies showed that normal cells recognize the loss of nucleotides and stop trying to replicate their DNA -- similar to how a driver who runs low on gas stops before he runs the engine dry.

What the researchers found is that the checkpoint mutants ignore this signal. Using the metaphor above, the driver of the car can't take his foot off of the accelerator and keeps going until his engine sputters to a stop. While this won't necessarily damage a car engine, it's catastrophic for DNA.

These mutant cells keep trying to replicate their DNA, unwinding the strands, until the DNA strands reach a "collapse point" where they break -- arguably the worst kind of damage that can be done to a cell.

"We predict that this is a source of increased cancer risk in human cells that harbor checkpoint mutations," Sabatinos said. "Replication-fork instability or collapse may occur at a low frequency in these mutated cells without drug treatment, leading to more frequent DNA changes down the road."

The next step will be to determine what happens to the small fraction of mutant cells that survive this treatment.

"By bringing to bear a sophisticated combination of genetic tools, drug treatment and state-of-the-art imaging, Susan Forsburg and her co-workers have elicited a fresh perspective on a long-standing problem," said Michael Reddy, who oversees DNA replication grants at the National Institutes of Health's National Institute of General Medical Sciences, which funded the work.

"Their fundamentally revised scenario of the dynamics of fork collapse is likely to lead to invaluable insights as to how checkpoint-defective human cancer cells preserve their DNA, thereby resisting chemotherapy," he said.


Story Source:

The above story is based on materials provided by University of Southern California. Note: Materials may be edited for content and length.


Journal Reference:

  1. S. A. Sabatinos, M. D. Green, S. L. Forsburg. Continued DNA synthesis in replication checkpoint mutants leads to fork collapse. Molecular and Cellular Biology, 2012; DOI: 10.1128/MCB.01060-12

Cite This Page:

University of Southern California. "Cancer: Some cells don't know when to stop." ScienceDaily. ScienceDaily, 19 November 2012. <www.sciencedaily.com/releases/2012/11/121119171403.htm>.
University of Southern California. (2012, November 19). Cancer: Some cells don't know when to stop. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2012/11/121119171403.htm
University of Southern California. "Cancer: Some cells don't know when to stop." ScienceDaily. www.sciencedaily.com/releases/2012/11/121119171403.htm (accessed August 1, 2014).

Share This




More Health & Medicine News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

House Republicans Vote to Sue Obama Over Healthcare Law

House Republicans Vote to Sue Obama Over Healthcare Law

Reuters - US Online Video (July 31, 2014) The Republican-led House of Representatives votes to sue President Obama, accusing him of overstepping his executive authority in making changes to the Affordable Care Act. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Despite Health Questions, E-Cigs Are Beneficial: Study

Despite Health Questions, E-Cigs Are Beneficial: Study

Newsy (July 31, 2014) Citing 81 previous studies, new research out of London suggests the benefits of smoking e-cigarettes instead of regular ones outweighs the risks. Video provided by Newsy
Powered by NewsLook.com
Dangerous Bacteria Kills One in Florida

Dangerous Bacteria Kills One in Florida

AP (July 31, 2014) Sarasota County, Florida health officials have issued a warning against eating raw oysters and exposing open wounds to coastal and inland waters after a dangerous bacteria killed one person and made another sick. (July 31) Video provided by AP
Powered by NewsLook.com
Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins