Gene Therapy Trial Termed A Success

A U.S. trial evaluating the safety of using a gene vector to deliver a corrective gene to patients with a common hereditary disorder has been completed.

The experimental gene therapy to combat alpha-1 antitrypsin deficiency -- a common hereditary disorder that causes lung and liver disease -- has caused no harmful effects in the 12 patients and shows signs of being effective, University of Florida researchers said.

"The primary end point in the trial was to see whether it was safe to give patients this gene transfer vector ...," said Terence Flotte, a pediatrician, geneticist and microbiologist with the University of Florida 's College of Medicine.

"We found that we can use this agent safely and we also saw evidence in the patients' blood that the higher doses successfully introduced the vector DNA," said Flotte. "In one patient we saw evidence for a very brief period that some of the alpha-1 protein was being produced but not at a high enough level to be beneficial."

The findings appear online in the journal Human Gene Therapy.

Scientists Discover Way To Block Growth Of Prostate Cancer Cells

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 Symposium on Molecular Targets and Cancer Therapeutics in Prague on 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."

Malaria Drug Regains It's Punch

A crucial malaria drug that lost it's punch in most countries because of germ resistance now appears to be highly effective again in one African nation - a startling shift with implications for other tough bugs.

It appears to be the first time a drug widely used against a killer disease has regained effectiveness after a break in use. " We didn't expect to see this," said researcher Chistopher Plowe of the University of Maryland School of Medicine. "I'm not aware of any case where a drug wasn't working clinically and was withdrawn and now is 100 percent effective again." The drug, chloroquine, was for many years the standard for treating malaria because it is very cheap, effective and safe. But in 1993, doctors stopped using it in the African nation of Malawi, because it was no longer effective in fighting most malaria cases. However, in recent years, researchers saw signs of genetic shifts in malaria that suggested it might again be vulnerable to chloroquine.

Kinky DNA At The Nanoscale

Scientists have answered a long-standing molecular stumper regarding DNA: How can parts of such a rigid molecule bend and coil without requiring large amounts of force? According to a team of researchers from the United States and the Netherlands, led by a physicist from the University of Pennsylvania, DNA is much more flexible than previously believed when examined over extremely small lengths. They used a technique called atomic force microscopy to determine the amount of energy necessary to bend DNA over nano-size lengths (about a million times smaller than a printed letter).

The findings, which appear in the November issue of the journal Nature Nanotechnology, illustrate how molecular properties often appear different when viewed at different degrees of magnification.

"DNA is not a passive molecule. It constantly needs to bend, forming loops and kinks, as other molecules interact with it," said Philip Nelson, a professor in Penn's Department of Physics and Astronomy in the School of Arts and Sciences. "But when people looked at long chunks of DNA, it always seemed to behave like a stiff elastic rod."

For example, DNA must wrap itself around proteins, forming tiny molecular structures called nucleosomes, which help regulate how genes are read. The formation of tight DNA loops also plays a key role in switching some genes off. According to Nelson, such processes were considered a minor mystery of nature, in part because researchers didn't have the tools of nanotechnology to examine molecules in such fine detail.

"Common sense and physics seemed to tell us that DNA just shouldn't spontaneously bend into such tight structures, yet it does," Nelson said. "In the conventional view of a DNA molecule, wrapping DNA into a nucleosome would be like bending a yardstick around a baseball."

To study DNA on the needed short length scales, Nelson and his colleagues used a technique called high-resolution atomic force microscopy to obtain a direct measurement of the energy it would take to bend lengths of DNA just a few nanometers long. The technique involves dragging an extremely sharp tip across the contours of the molecule in order to create a picture of its structure.

With this tool, Nelson and his colleagues measured the energies required to make various bends in DNA at lengths of five to 50 nanometers - about a thousand times smaller than the diameter of a typical human cell.

''We found that DNA has different apparent properties when probed at short lengths than the entire molecule does when taken as a whole," Nelson said. ''Its resistance to large-angle bends at this scale is much smaller than previously suspected."

Nelson is also a member of Penn's Nano-Bio Interface Center, which explores how the fields of nanotechnology, biology and medicine all intersect.

"The nanoscale just happens to also be the scale at which cell biology operates," Nelson said. "We're entering an era when we are able to use the tools of nanotechnology to answer fundamental puzzles of biology."