Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study provides insights on why some prostate cancer becomes resistant to hormone withdrawl therapy

26.01.2005


A new study by scientists at Fred Hutchinson Cancer Research Center provides insight into why some men develop aggressive prostate cancer that becomes resistant to hormone-withdrawal therapy, a common form of treatment.



Researchers found that certain mutations in a protein called the androgen receptor cause advanced and invasive prostate cancer when put into otherwise healthy mice. The androgen receptor’s normal function is to control growth of the prostate gland in response to cues from male hormones called androgens, which have long been thought to stimulate prostate tumors.

Because similarly defective androgen receptors have been found in prostate-cancer patients whose disease is resistant to hormone withdrawal, the finding sheds light on why most men with advanced prostate cancer treated with hormone-withdrawal therapy fail to be cured. The work opens the door to discovery of new, more effective therapies, according to Norman Greenberg, Ph.D., a member of Fred Hutchinson’s Clinical Research Division.


The study is published in the Jan. 25, 2005 issue of the Proceedings of the National Academy of Sciences. The study was led by Dr. Guangzhou Han and colleagues.

Greenberg said that despite these and other earlier findings indicating a strong relationship between the androgen receptor and prostate cancer, no group had proved that it could be a key driver of disease. "Our study is the first to demonstrate that if the androgen receptor acquires certain mutations, it can cause prostate cancer in otherwise healthy mice," he said. "Because very similar mutations have been found in androgen receptors from prostate-cancer patients whose disease is resistant to hormone-withdrawal therapy, we think this is a very significant finding."

The results suggest that prostate-cancer prevention trials involving drugs that lower a man’s androgen levels should proceed cautiously, since complete androgen withdrawal seems to provide an environment that favors the development of the cancer-causing mutations. In addition, the work is the first to show that a class of proteins called steroid receptors, of which the androgen receptor is a member, can become cancer-causing genes known as oncogenes. The estrogen and progesterone receptors--two receptors that become defective in many breast cancers--are also members of this protein family.

The androgen receptor is a protein produced by prostate cells that binds to androgens, a family of chemically related hormones that includes testosterone. Although the binding of androgens to the receptor is important for healthy prostate development, the hormones may, under some conditions, stimulate the prostate-tumor cells to divide. For that reason, many men with advanced prostate cancer are treated with drugs that either block the production of androgens or the ability of the androgens to interact with their receptor.

About 90 percent of the time, prostate tumors shrink after hormone deprivation, but in most cases, it is believed that a small percentage of the tumor cells become resistant. Eventually, these resistant cells grow to become the predominant cancer, and no successful therapies have yet been developed for men with the hormone-withdrawal-resistant form of the disease.

In their study, researchers identified several mutations that impair the ability of the androgen receptor to interact with proteins called co-regulators. Co-regulators help the receptor to carry out its functions at the proper time; therefore, lack of interaction between the receptor and the appropriate co-regulators is thought to spur cancer development. Analogous mutant receptors also have been found in human prostate cancers.

Researchers wondered what would happen if they put the mutant receptors into otherwise healthy mice that also contained a normal version of the androgen receptor. They found that 100 percent of the time, the addition of one particular mutant receptor cause rapid development of a precancerous condition that progressed to advanced disease. In contrast, mice with extra copies of a normal receptor, as well as mice with the normal receptor and an unrelated type of mutant receptor, did not cause cancer.

"This demonstrates a causal role for certain androgen receptor mutations in prostate cancer," Greenberg said. Not all men with hormone-withdrawal-resistant disease develop such mutations, Greenberg said. Yet hormone-deprivation treatment can create a situation in some prostate tumors in which such mutations give a growth advantage to cancer cells.

Such mutant receptors might prove to be good drug targets, Greenberg said.

"These and other mutant forms of the receptor should be potential targets for new drugs that will be particularly effective in men whose cancers have these mutations and related events," he said. Because androgen deprivation has numerous side effects--including bone loss and sexual dysfunction--drugs that specifically attack the cancer-causing protein would be much more desirable than existing therapies. Drugs that effectively work against certain mutant proteins have been developed for other cancers, including Iressa for lung cancer and Gleevec for chronic myeloid leukemia.

Since the mutations Greenberg’s lab studied appear to affect one specific function of the androgen receptor, it may also be possible to develop drugs that target other proteins that collaborate with the androgen receptor in this pathway. Greenberg’s lab is now studying this pathway, with the hope of providing more insight into the drug discovery process.

Dean Forbes | EurekAlert!
Further information:
http://www.fhcrc.org

More articles from Health and Medicine:

nachricht Finnish research group discovers a new immune system regulator
23.02.2018 | University of Turku

nachricht Minimising risks of transplants
22.02.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>