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

NIH Study Uncovers New Mechanism of Action for Class of Chemotherapy Drugs

Published: Friday, November 02, 2012
Last Updated: Friday, November 02, 2012
Bookmark and Share
National Institutes of Health (NIH) researchers have discovered a significant new mechanism of action for a class of chemotherapy drugs known as poly (ADP-ribose) polymerase inhibitors, or PARP inhibitors.

They have also identified differences in the toxic capabilities of three drugs in this class which are currently being tested in clinical trials. The study, by scientists at the National Cancer Institute (NCI), part of NIH, and their colleagues, appeared in Cancer Research, Nov 1, 2012.

In recent years, drugs classified as PARP inhibitors have been shown to be promising anticancer agents for breast and ovarian cancer. Members of the PARP family of proteins are involved in a number of critical cellular processes, including DNA damage repair and programmed cell death. Prior to this study, PARP inhibitors were thought to work primarily by blocking PARP enzyme activity, thus preventing the repair of DNA damage and ultimately causing cell death.

In this study, scientists established that PARP inhibitors have an additional mode of action: localizing PARP proteins at sites of DNA damage, which has relevance to their anti-tumor activity. The trapped PARP protein–DNA complexes are highly toxic to cells because they block DNA replication. When the researchers tested three PARP inhibitors for their differential ability to trap PARP proteins on damaged DNA, they found that the trapping potency of the inhibitors varied widely.

"Critical to our research is that, while PARP inhibitors had been assumed to be of equivalent potency based on the degree to which they elicit PARP inhibition, we now know that they are not equivalent with respect to their potency to trap PARP," said Yves Pommier, M.D., Ph.D., NCI Center for Cancer Research. "Our findings suggest that PARP inhibitors should be categorized according to their potency to trap PARP, in addition to their enzyme inhibition abilities."

The PARP family of proteins in humans includes PARP1 and PARP2, which are DNA binding and repair proteins. When activated by DNA damage, these proteins recruit other proteins that do the actual work of repairing DNA. Under normal conditions, PARP1 and PARP2 are released from DNA once the repair process is underway. However, as this study shows, when they are bound to PARP inhibitors, PARP1 and PARP2 become trapped on DNA. The researchers showed that trapped PARP–DNA complexes are more toxic to cells than the unrepaired single-strand DNA breaks that accumulate in the absence of PARP activity, indicating that PARP inhibitors act as PARP poisons.

In collaboration with James Doroshow, M.D., deputy director for clinical and translational research at NCI, the investigators used PARP assays (ways of measuring PARP activity in cells and tissues) to compare three PARP inhibitor compounds that are currently in clinical testing: MK-4827, olaparib, and veliparib.

The scientists found that the three PARP inhibitors differed in their ability to inhibit PARP enzyme activity, with olaparib being the most potent inhibitor, followed by veliparib and then MK-4827. However, in terms of toxicity, MK-4827 was the most potent, followed by olaparib and then veliparib. Moreover, PARP1 complexes with MK-4827 and olaparib were shown to be more tightly bound to DNA than complexes with veliparib.

These findings suggest that there may be two classes of PARP inhibitors, catalytic inhibitors that act mainly to inhibit PARP enzyme activity and do not trap PARP proteins on DNA, and dual inhibitors that both block PARP enzyme activity and act as PARP poison.

"Our findings suggest that clinicians who use PARP inhibitors in clinical trials should carefully choose their drug, because we now suspect results may differ, depending upon the PARP inhibitor used," said Junko Murai, M.D., Ph.D., NCI Center for Cancer Research. "As a next step, we are working to categorize other leading PARP inhibitors based upon both PARP trapping and PARP inhibition."


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 2,400+ scientific posters on ePosters
  • More than 3,700+ 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 TechnologyNetworks.com 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.

Related Content

Young South African Women can Adhere to Daily PrEP Regimen as HIV Prevention
NIH-funded study finds men in Bangkok, Harlem also successful in taking daily dose.
Saturday, July 25, 2015
Study Shows Promise of Precision Medicine for Most Common Type of Lymphoma
The study appeared online July 20, 2015, in Nature Medicine.
Tuesday, July 21, 2015
HIV Control Through Treatment Durably Prevents Heterosexual Transmission of Virus
NIH-funded trial proves suppressive antiretroviral therapy for HIV-infected people effective in protecting uninfected partners.
Tuesday, July 21, 2015
Early Antiretroviral Therapy Prevents Non-AIDS Outcomes in HIV-infected People
NIH-supported findings illustrate manifold benefit of therapy.
Tuesday, July 21, 2015
NIH-funded Vaccine for West Nile Virus Enters Human Clinical Trials
Enrollment is expected to be completed by December 2015.
Tuesday, July 07, 2015
In Blinding Eye Disease, Trash-Collecting Cells Go Awry, Accelerate Damage
NIH research points to microglia as potential therapeutic target in retinitis pigmentosa.
Friday, July 03, 2015
Boys More Likely to Have Antipsychotics Prescribed, Regardless of Age
NIH-funded study is the first look at antipsychotic prescriptions patterns in the U.S.
Thursday, July 02, 2015
New Medication for Alcohol Use Disorder
NIH begins clinical trial investigating a potential treatment for alcohol use disorder.
Friday, June 26, 2015
NIH Begins Clinical Trial of New Medication for Alcohol Use Disorder
Clinical trial will evaluate the safety and effectiveness of gabapentin enacarbil in treating alcohol use disorder.
Friday, June 26, 2015
Study of Ebola Survivors Opens in Liberia
Trial to examine long-term health effects of Ebola virus disease.
Friday, June 19, 2015
NIH Names Walter J. Koroshetz, M.D. Director of the NINDS
Dr. Collins recognized Dr. Koroshetz’ role in the creation of the StrokeNet.
Saturday, June 13, 2015
NCI-MATCH Trial will Link Targeted Cancer Drugs to Gene Abnormalities
Precision medicine trial will open to patient enrollment in July.
Tuesday, June 09, 2015
Linking Targeted Cancer Drugs to Gene Abnormalities
Investigators at the NIH have announced a series of clinical trials that will study drugs or drug combinations that target specific genetic mutations.
Wednesday, June 03, 2015
Starting Antiretroviral Treatment Early Improves Outcomes for HIV-infected Individuals
NIH-funded trial results likely will impact global treatment guidelines.
Thursday, May 28, 2015
Two Treatments Yield Similar Results for Children After Cardiac Arrest
NIH-funded research finds therapeutic hypothermia no more effective than normal temperature control.
Friday, May 08, 2015
Scientific News
Young South African Women can Adhere to Daily PrEP Regimen as HIV Prevention
NIH-funded study finds men in Bangkok, Harlem also successful in taking daily dose.
Researchers Find Key Player in Diabetic Kidney Disease Through Power of Metabolomics
Discovery could lead to new and better diagnostic marker for chronic kidney disease.
Immunotherapy Shows Promise for Myeloma
A strategy, which uses patients’ own immune cells, genetically engineered to target tumors, has shown significant success against multiple myeloma, a cancer of the plasma cells that is largely incurable.
Santhera Announces First Patient Dosing with Omigapil in CMD
Company announces full patient recruitment of CALLISTO study.
Study Shows Promise of Precision Medicine for Most Common Type of Lymphoma
The study appeared online July 20, 2015, in Nature Medicine.
HIV Control Through Treatment Durably Prevents Heterosexual Transmission of Virus
NIH-funded trial proves suppressive antiretroviral therapy for HIV-infected people effective in protecting uninfected partners.
Adaptimmune's Novel Cancer Therapeutics Show Positive Clinical Trial Results
The company has announced that positive data from its Phase I/II study of its affinity enhanced T-cell receptor (TCR) therapeutic targeting the NY-ESO-1 cancer antigen in patients with multiple myeloma has been published.
Early Antiretroviral Therapy Prevents Non-AIDS Outcomes in HIV-infected People
NIH-supported findings illustrate manifold benefit of therapy.
Adaptimmune’s NY-ESO-1 TCR-engineered T-Cells Demonstrate Durable Persistence
Study has been published in Nature Medicine.
First Made-in-Singapore Cancer Drug Enters Clinical Testing
The drug prevents cancer progression and paves the way for new advancements in cancer therapeutics.
Scroll Up
Scroll Down
SELECTBIO

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
2,400+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
3,700+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FREE!