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Scientists discover way to block growth of prostate cancer cells
November 08, 2006Prague, Czech Republic: Scientists have discovered for the first time a specific biochemical pathway by which the sex hormone, androgen, increases levels of harmful chemicals called reactive oxygen species (ROS) in the prostate gland that play a role in the development of prostate cancer.
They found that a drug that blocks this pathway significantly prolonged survival and inhibited tumour development in mice that were genetically engineered to spontaneously develop prostate cancer and die of the disease. The hope is that this drug could be used eventually to treat men at high risk of developing prostate cancer and to prevent recurrences in men already treated for primary tumours.
Dr Hirak Basu told a news briefing at the EORTC-NCI-AACR [1] Symposium on Molecular Targets and Cancer Therapeutics in Prague today (Wednesday 8 November): "Previous work has demonstrated that androgen treatment increased reactive oxygen species levels in androgen-dependent prostate cancer cells, but, until now, the pathway involved was unknown."
Dr Basu is an associate scientist and principal investigator in the Prostate Cancer Group at the Paul P. Carbone Comprehensive Cancer Center, Madison, WI, USA. He and his collaborators at the centre found that levels of a key enzyme, spermidine/spermine acetyl transferase (SSAT), which starts oxidation of polyamines, rose markedly when prostate cancer cells were treated with androgen. Polyamines are small molecules produced in large quantity by the prostate gland and are secreted in the seminal fluid. Oxidation of polyamines generates a large amount of the ROS, hydrogen peroxide. Peroxide causes oxidative stress, a condition in which cells produce an excess of oxygen-free radicals, which are known to play a key role in cell signalling and prostate cancer development.
"These results demonstrate that polyamine oxidation is one of the major causes of androgen-induced oxidative stress in prostate cancer cells," said Dr Basu. "The discovery of this pathway is a major step forward in understanding the role of androgen in prostate cancer development.
"Many scientists in the polyamine field have worked towards increasing, rather than decreasing, oxidative stress in order to destroy established tumours. However, no one that I know has tried to reduce oxidative stress by blocking polyamine oxidation to prevent prostate tumours, and this is what we set out to do."
Having discovered the role played by polyamine oxidation, the researchers with the help of their collaborators at Wayne State University, Detroit, MI, USA, synthesised a molecule called MDL 72,527 (MDL), which was previously known to be an inhibitor of acetyl polyamine oxidase (APAO). APAO catalyses the oxidation of acetyl polyamines produced by SSAT - the process that results in the generation of ROS. MDL can, therefore, block androgen-induced ROS production in prostate cancer cells.
They injected MDL into the genetically engineered mice and found that it inhibited polyamine oxidation and reduced oxidative stress in the prostate glands of the animals. The treatment significantly increased overall survival and delayed time to prostate tumour development. In repeat experiments, between 50-60% of mice treated with MDL survived ten to twelve weeks longer than the untreated control group.
"To the best of our knowledge, this is the first report of a specific enzyme inhibitor MDL that blocks androgen-induced oxidative stress in the prostate and prevents spontaneous prostate tumour development," said Dr Basu.
More tests have to be carried out, but the researchers, working with the world-renowned prostate cancer clinician Dr George Wilding (a co-author of the paper), hope that phase I clinical trials of MDL might be able to start in 12-18 months.
Dr Basu said: "After surgery and radiotherapy for the primary tumour, breast cancer patients can be treated with several drugs such as tamoxifen and aromatase inhibitors that prevent or delay breast cancer recurrence. No such treatment exists for prostate cancer patients. After treatment of their primary tumours, prostate cancer in men is managed by watchful observation only. The immediate goal of our research is to develop agents such as MDL to fill this unmet medical need. If MDL, or any of the other agents that we are working with, can be expanded further to treat all high-risk men, we will be delighted.\\\
European Organisation for Research and Treatment of Cancer
Dr Basu is an associate scientist and principal investigator in the Prostate Cancer Group at the Paul P. Carbone Comprehensive Cancer Center, Madison, WI, USA. He and his collaborators at the centre found that levels of a key enzyme, spermidine/spermine acetyl transferase (SSAT), which starts oxidation of polyamines, rose markedly when prostate cancer cells were treated with androgen. Polyamines are small molecules produced in large quantity by the prostate gland and are secreted in the seminal fluid. Oxidation of polyamines generates a large amount of the ROS, hydrogen peroxide. Peroxide causes oxidative stress, a condition in which cells produce an excess of oxygen-free radicals, which are known to play a key role in cell signalling and prostate cancer development.
"These results demonstrate that polyamine oxidation is one of the major causes of androgen-induced oxidative stress in prostate cancer cells," said Dr Basu. "The discovery of this pathway is a major step forward in understanding the role of androgen in prostate cancer development.
"Many scientists in the polyamine field have worked towards increasing, rather than decreasing, oxidative stress in order to destroy established tumours. However, no one that I know has tried to reduce oxidative stress by blocking polyamine oxidation to prevent prostate tumours, and this is what we set out to do."
Having discovered the role played by polyamine oxidation, the researchers with the help of their collaborators at Wayne State University, Detroit, MI, USA, synthesised a molecule called MDL 72,527 (MDL), which was previously known to be an inhibitor of acetyl polyamine oxidase (APAO). APAO catalyses the oxidation of acetyl polyamines produced by SSAT - the process that results in the generation of ROS. MDL can, therefore, block androgen-induced ROS production in prostate cancer cells.
They injected MDL into the genetically engineered mice and found that it inhibited polyamine oxidation and reduced oxidative stress in the prostate glands of the animals. The treatment significantly increased overall survival and delayed time to prostate tumour development. In repeat experiments, between 50-60% of mice treated with MDL survived ten to twelve weeks longer than the untreated control group.
"To the best of our knowledge, this is the first report of a specific enzyme inhibitor MDL that blocks androgen-induced oxidative stress in the prostate and prevents spontaneous prostate tumour development," said Dr Basu.
More tests have to be carried out, but the researchers, working with the world-renowned prostate cancer clinician Dr George Wilding (a co-author of the paper), hope that phase I clinical trials of MDL might be able to start in 12-18 months.
Dr Basu said: "After surgery and radiotherapy for the primary tumour, breast cancer patients can be treated with several drugs such as tamoxifen and aromatase inhibitors that prevent or delay breast cancer recurrence. No such treatment exists for prostate cancer patients. After treatment of their primary tumours, prostate cancer in men is managed by watchful observation only. The immediate goal of our research is to develop agents such as MDL to fill this unmet medical need. If MDL, or any of the other agents that we are working with, can be expanded further to treat all high-risk men, we will be delighted.\\\
European Organisation for Research and Treatment of Cancer
Prostate Cancer Current Events and Prostate Cancer News RSSCarnegie Mellon researchers link health-care debate to risk of dying in US and Europe
The current health care debate in the United States is complicated. Trade-offs between heath care expenditures, lifestyle choices and life expectancy have been suggested but seldom clearly demonstrated.
New finding suggests prostate biopsy is not always necessary
Researchers at Wake Forest University School of Medicine and the University of Wisconsin-Madison have discovered that some elevated prostate-specific antigen (PSA) levels in men may be caused by a hormone normally occurring in the body, and are not necessarily a predictor of the need for a prostate biopsy.
Does prostate-specific antigen velocity help in early detection prostate cancer?
The November issue of European Urology, the official journal of the European Association of Urology, features an article focussing on prostate specific antigen (PSA) velocity and early cancer detection. It has been suggested that changes in PSA over time aid prostate cancer detection.
New Synthetic Molecules Trigger Immune Response to HIV and Prostate Cancer
Researchers at Yale University have developed synthetic molecules capable of enhancing the body's immune response to HIV and HIV-infected cells, as well as to prostate cancer cells. Their findings, published online in the Journal of the American Chemical Society, could lead to novel therapeutic approaches for these diseases.
Chemo-radiation before prostate removal may prevent cancer recurrence
Researchers in the Oregon Health & Science University Knight Cancer Institute and the Portland Veterans Affairs Medical Center have found a combination of radiation therapy and chemotherapy given before prostate removal is safe and may have the potential to reduce cancer recurrence and improve patient survival.
Blood vessels might predict prostate cancer behavior
A diagnosis of prostate cancer raises the question for patients and their physicians as to how the tumor will behave. Will it grow quickly and aggressively and require continuous treatment, or slowly, allowing therapy and its risks to be safely delayed?
Short-term hormone therapy and intermediate dose radiation increases survivial for early stage prostate cancer
Short-term hormone therapy given prior to and during intermediate dose radiation treatment for men with early stage prostate cancer increases their chance of living longer, compared to those who receive the same radiation alone.
Task force develops new radiation guidelines for brachytherapy
Radiation dose delivered to the prostate and nearby organs in every brachytherapy procedure should be carefully analyzed using post-implant CT or MRI and uniformly documented in every patient.
1 disease, not 1 demographic
The Asian continent has nearly four billion people living in 47 different countries, and each of these groups has their own unique set of health issues. But when they come to the United States, they're often lumped into one large demographic: "Asian/Pacific Islander."
Cancer survivors may not be getting the help they need to stop smoking
More than a quarter of cancer survivors who still smoke have not been advised to quit smoking by their health care providers in the last year, according to a study published by researchers at Fox Chase Cancer Center in the current issue of the Journal of General Internal Medicine.
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