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Erectile dysfunction drugs allowed more chemotherapy to reach brain tumors in laboratory study
July 29, 2008In a study using laboratory animals, researchers found that medications commonly prescribed for erectile dysfunction opened a mechanism called the blood-brain tumor barrier and increased delivery of cancer-fighting drugs to malignant brain tumors.
The experiments were conducted at Cedars-Sinai Medical Center's Maxine Dunitz Neurosurgical Institute and published in Brain Research.
Viagra (sildenafil) and Levitra (vardenafil) are known as PDE5 inhibitors because they block an enzyme, phosphodiesterase5, which interrupts a series of biochemical events that cause the decreased blood flow of erectile dysfunction. This laboratory rat study, published online ahead of print in the journal, found that similar biochemical interactions in the small vessels of the brain play a major role in the blood-brain tumor barrier, which impedes delivery of anti-tumor drugs into brain tumors. PDE5 inhibitors were found to open the barrier and increase drug transport in this early animal study.
Although the normal blood-brain barrier, which regulates access to the brain from the bloodstream, shares many characteristics with the blood-brain tumor barrier, the signaling mechanism blocked by PDE5 inhibitors is unique to the blood-brain tumor barrier. This allows the PDE5 inhibitors to selectively increase drug transport to malignant brain tumors without affecting normal brain tissue.
According to the researchers, these findings may have significant implications in improving drug delivery to brain tumors in patients.
"This is the first study to show that oral administration of PDE5 inhibitors increases the rate of transport of compounds across the blood-brain tumor barrier and improves the effectiveness of the anti-tumor drug adriamycin in the treatment of brain tumors in a rat model. We chose adriamycin for this study because it is one of the most effective drugs against brain tumor cell lines in the laboratory but it has very little effect in animals and humans because it is unable to cross the blood-brain tumor barrier. The combination of vardenafil and adriamycin resulted in longer survival and smaller tumor size," said neurosurgeon Keith L. Black, M.D., chairman of the Department of Neurosurgery at Cedars-Sinai Medical Center and director of the Maxine Dunitz Neurosurgical Institute.
Black, the article's first and corresponding author, has been recognized for his earlier groundbreaking work to break through the blood-brain tumor barrier with natural and synthetic bradykinin, a peptide that temporarily opens the barrier and increases anti-cancer drug delivery into certain tumors by more than 1,000 percent. In 2000, he received the Javits Neuroscience Investigator Award from the National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health, for his blood-brain barrier research.
In the current studies, the blood-brain tumor barrier-opening effects of PDE5 lasted considerably longer than those of bradykinin and allowed greater transport across the barrier into tumor tissues. Because vardenafil was found to be more effective than sildenafil in increasing blood-brain tumor barrier permeability and transport, vardenafil was used in a survival study of 29 tumor-bearing rats. Those treated with saline (control) survived 32 days on average while those treated with vardenafil alone survived about 35 days and those treated with adriamycin alone survived about 42 days. When vardenafil was combined with adriamycin, rats survived an average 53 days.
Although the researchers exposed the laboratory animals to doses of sildenafil and vardenafil that are comparable to the dose range approved for erectile dysfunction in humans, there were no detectable side effects in the rats, and neither drug increased transport of tracers into normal brain tissue.
Cedars-Sinai Medical Center
Although the normal blood-brain barrier, which regulates access to the brain from the bloodstream, shares many characteristics with the blood-brain tumor barrier, the signaling mechanism blocked by PDE5 inhibitors is unique to the blood-brain tumor barrier. This allows the PDE5 inhibitors to selectively increase drug transport to malignant brain tumors without affecting normal brain tissue.
According to the researchers, these findings may have significant implications in improving drug delivery to brain tumors in patients.
"This is the first study to show that oral administration of PDE5 inhibitors increases the rate of transport of compounds across the blood-brain tumor barrier and improves the effectiveness of the anti-tumor drug adriamycin in the treatment of brain tumors in a rat model. We chose adriamycin for this study because it is one of the most effective drugs against brain tumor cell lines in the laboratory but it has very little effect in animals and humans because it is unable to cross the blood-brain tumor barrier. The combination of vardenafil and adriamycin resulted in longer survival and smaller tumor size," said neurosurgeon Keith L. Black, M.D., chairman of the Department of Neurosurgery at Cedars-Sinai Medical Center and director of the Maxine Dunitz Neurosurgical Institute.
Black, the article's first and corresponding author, has been recognized for his earlier groundbreaking work to break through the blood-brain tumor barrier with natural and synthetic bradykinin, a peptide that temporarily opens the barrier and increases anti-cancer drug delivery into certain tumors by more than 1,000 percent. In 2000, he received the Javits Neuroscience Investigator Award from the National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health, for his blood-brain barrier research.
In the current studies, the blood-brain tumor barrier-opening effects of PDE5 lasted considerably longer than those of bradykinin and allowed greater transport across the barrier into tumor tissues. Because vardenafil was found to be more effective than sildenafil in increasing blood-brain tumor barrier permeability and transport, vardenafil was used in a survival study of 29 tumor-bearing rats. Those treated with saline (control) survived 32 days on average while those treated with vardenafil alone survived about 35 days and those treated with adriamycin alone survived about 42 days. When vardenafil was combined with adriamycin, rats survived an average 53 days.
Although the researchers exposed the laboratory animals to doses of sildenafil and vardenafil that are comparable to the dose range approved for erectile dysfunction in humans, there were no detectable side effects in the rats, and neither drug increased transport of tracers into normal brain tissue.
Cedars-Sinai Medical Center
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Adult survivors of childhood cancer are 20 to 25 percent more likely to never marry compared with siblings and the general population, Yale School of Medicine researchers report in a new study published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
Brain tumors in childhood leave a lasting mark on cognition, life status
Brain tumors in childhood cast a long shadow on survivors. The first study of the lasting impact of these tumors -- the most common solid malignancies in childhood -- shows that survivors have ongoing cognitive problems.
Angiochem crosses BBB, shows safety, efficacy in phase 1/2 brain cancer studies
Angiochem, Inc. a clinical-stage biotechnology company developing drugs that are uniquely capable of crossing the blood-brain barrier to treat brain diseases, announced today that its lead drug candidate, ANG1005, has demonstrated a favorable safety and efficacy profile in more than 100 patients with brain cancer from two separate Phase 1 /2 clinical studies in patients with progressive gliomas, including recurrent glioblastoma, and in patients with progressive brain metastases.
Researchers report benefits of new standard treatment study for rare pediatric brain cancer
A team of researchers led by The University of Texas M. D. Anderson Cancer Center unveiled results today from the largest-ever collaborative study addressing the treatment of a rare pediatric brain tumor.
Unequal access: Hispanic children rarely get top-notch care for brain tumors
Hispanic children diagnosed with brain tumors get high-quality treatment at hospitals that specialize in neurosurgery far less often than other children with the same condition, potentially compromising their immediate prognosis and long-term survival, according to research from Johns Hopkins published in October's Pediatrics.
tudy: The new buzz on detecting tinnitus
It's a ringing, a buzzing, a hissing or a clicking - and the patient is the only one who can hear it. Complicating matters, physicians can rarely pinpoint the source of tinnitus, a chronic ringing of the head or ears that can be as quiet as a whisper or as loud as a jackhammer.
New Approach for the Treatment of Malignant Brain Tumors
Initial chemotherapy alone after surgery is just as successful as initial radiation therapy for patients from whom a very malignant brain tumor (anaplastic glioma) was removed. With this treatment, the patients survive on average > 30 months without a recurrence.
Weizmann Institute Scientists Discover A New Protein Partnership That Leads to Pediatric Tumor Regression
Why are some pediatric cancers able to spontaneously regress? Prof. Michael Fainzilber and his team of the Weizmann Institute's Biological Chemistry Department seem to have unexpectedly found part of the answer.
Why don't brain tumors respond to medication?
Malignant brain tumors often fail to respond to promising new medication. Researchers in Heidelberg have discovered a mechanism and a tumor marker for the development of this resistance.
NIH researchers identify key factor that stimulates brain cancer cells to spread
Researchers funded by the National Institutes of Health have found that the activity of a protein in brain cells helps stimulate the spread of an aggressive brain cancer called glioblastoma multiforme (GBM).
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