Featured Research

from universities, journals, and other organizations

Gene Helps Protect Tumor Suppressor In Breast Cancer

Date:
April 13, 2009
Source:
University of Texas M. D. Anderson Cancer Center
Summary:
Scientists have discovered a gene that protects PTEN, a major tumor-suppressor that is reduced but rarely mutated in about half of all breast cancers.

Scientists at The University of Texas M. D. Anderson Cancer Center have discovered a gene that protects PTEN, a major tumor-suppressor that is reduced but rarely mutated in about half of all breast cancers.

The gene Rak helps protect and regulate PTEN, which also is important in several other types of cancer, the team reports in the April edition of Cancer Cell. Causes for diminished PTEN protein levels in breast cancer absent a mutation of the PTEN gene have eluded researchers, who knew for several years that a piece of the puzzle was missing.

"We've clearly discovered the missing link that explains how Rak can stabilize PTEN protein to prevent breast cancer development," said lead author Shiaw-Yih Lin, Ph.D., an assistant professor in the Department of Systems Biology at M. D. Anderson. "Our research explains why PTEN is defective in breast cancer and provides important clues for the development of effective therapy in Rak- or PTEN-defective breast cancers."

In addition to breast cancer, PTEN frequently is mutated or inactivated in glioblastoma, melanoma, and cancers of the prostate and endometrium. The severity of PTEN irregularities strongly correlates with the tumor stage and grade. For example, complete loss of PTEN expression is found more frequently in metastatic cancer than in primary tumors.

In the laboratory, researchers found Rak can stabilize PTEN protein and function as a tumor suppressor gene to prevent breast cancer development.

To examine the correlation between Rak and PTEN protein expression, researchers analyzed cells from 42 breast cancers. Rak expression showed a strong positive correlation with PTEN.

They also investigated the effect of Rak expression by injecting mice with cells that over-expressed Rak. All the mice injected with Rak-overexpressing cells remained tumor free, whereas all the control mice developed tumors.

"To further assess whether Rak is a bona fide breast tumor suppressor gene, we sought to determine if loss of Rak expression would transform normal mammary epithelial cells," Lin said. "We injected control cells or cells in which Rak was compromised into the mammary glands of healthy mice and monitored tumor growth. Notably, all the mice injected with Rak-knockdown cells, but none of the mice injected with control cells, developed tumors."

Recent studies have shown that the PTEN protein is destroyed when it is bound by the enzyme NEDD4-1, which attaches targeting molecules called ubiquitins that mark PTEN for destruction by the ubiquitin proteasome complex.

Lin and colleagues showed that Rak saves PTEN from degradation by attaching a phosphate group to the protein, blocking NEDD4-1 from binding to PTEN.

Although this study demonstrates a PTEN-dependent function of Rak, Lin says much research remains ahead on yet-unidentified PTEN-independent functions of Rak in tumor suppression.

"Recently, we found that Rak can prevent spontaneous DNA damage and has a critical role in suppressing cancer stem cells," he said. "So, we will expand our research efforts toward determining how Rak helps to maintain genomic integrity."

This work was supported in part by a grant from the National Cancer Institute.

In addition to Lin, other authors on the study included Eun-Kyoung Yim, Ph.D., Guang Peng, M.D., Ph.D., Hui Dai, M.D., Ruozhen Hu, M.S., Yiling Lu, M.D., and Gordon Mills, M.D., Ph.D. of the Department of Systems Biology at M. D. Anderson; Kaiyi Li, Ph.D. of the Department of Surgery at Baylor College of Medicine, Funda Meric-Bernstam, M.D. of the Department of Surgical Oncology at M. D. Anderson; Bryan Hennessy, M.D. of the Department of Gynecologic Medical Oncology at M. D. Anderson; and Rolf Craven, Ph.D. of the Department of Molecular and Biomedical Pharmacology at the University of Kentucky, Lexington.


Story Source:

The above story is based on materials provided by University of Texas M. D. Anderson Cancer Center. Note: Materials may be edited for content and length.


Cite This Page:

University of Texas M. D. Anderson Cancer Center. "Gene Helps Protect Tumor Suppressor In Breast Cancer." ScienceDaily. ScienceDaily, 13 April 2009. <www.sciencedaily.com/releases/2009/04/090406132054.htm>.
University of Texas M. D. Anderson Cancer Center. (2009, April 13). Gene Helps Protect Tumor Suppressor In Breast Cancer. ScienceDaily. Retrieved October 2, 2014 from www.sciencedaily.com/releases/2009/04/090406132054.htm
University of Texas M. D. Anderson Cancer Center. "Gene Helps Protect Tumor Suppressor In Breast Cancer." ScienceDaily. www.sciencedaily.com/releases/2009/04/090406132054.htm (accessed October 2, 2014).

Share This



More Health & Medicine News

Thursday, October 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Pregnancy Spacing Could Have Big Impact On Autism Risks

Pregnancy Spacing Could Have Big Impact On Autism Risks

Newsy (Oct. 1, 2014) A new study says children born less than one year and more than five years after a sibling can have an increased risk for autism. Video provided by Newsy
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com
Insertable Cardiac Monitor

Insertable Cardiac Monitor

Ivanhoe (Oct. 1, 2014) A heart monitor the size of a paperclip that can save your life. The “Reveal Linq” allows a doctor to monitor patients with A-Fib on a continuous basis for up to 3 years! Video provided by Ivanhoe
Powered by NewsLook.com
Attacking Superbugs

Attacking Superbugs

Ivanhoe (Oct. 1, 2014) Two weapons hospitals can use to attack superbugs. Scientists in Ireland created a new gel resistant to superbugs, and a robot that can disinfect a room in minutes. Video provided by Ivanhoe
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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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