AAP
May 1, 2008
A tiny protein found in sunflower seeds is showing potential as a new therapy to stop aggressive prostate cancer tumours spreading to the bone.
Australian scientists have developed a novel way of preventing enzymes from breaking down the connective tissue around tumours that allow cancer cells to migrate to other parts of the body.
The preliminary breakthrough has so far only been demonstrated in the test tube, but if current trials on mice are successful, a new human therapy will be available targeting prostate cancer spread.
"The dream end-product is having a drug which could be produced in sunflower seeds and given as a simple dietary supplement for people with prostate cancer," said study leader Dr Jonathan Harris, of the Queensland University of Technology.
The research team investigated the mini-protein as a potential treatment of prostate cancer, in particular for those patients who relapse.
"The best thing to do in those cases is block the disease spreading to other organs, particularly the spine, which is very debilitating," Dr Harris said.
"It is not the prostate tumour that kills you. It is when the cancer cells escape from the prostate, so we want to prevent that."
The spread is largely caused by enzymes called proteases which break down the connective tissue around tumours, allowing the cancer cells to migrate.
In test tube-based trials the researchers discovered the sunflower mini-protein, known as the protease inhibitor, was able to block these enzymes.
They then re-engineered the molecule so it blocks only the proteases produced in the cancer and leave other "good" proteases unharmed.
"We are extremely happy because now we can carry out trials in mouse-models of prostate cancer, and if we have positive results we could get a pharmaceutical industry partner interested in the work," Dr Harris said.
Cancer Council Australia chief executive Professor Ian Olver said new targeted therapies for prostate cancer we much needed.
"Because prostate cancer is driven by the male hormone, it can be quite well contained for a few years by giving anti-hormone drugs, but eventually it becomes insensitive to it," Prof Olver said.
"After this there is really only chemotherapy, so it's exciting to have a specifically-targeted therapy for relapse possibly on the horizon.
About 14,000 new cases of prostate cancer are diagnosed in Australia each year, and about 3,000 men die from the disease each year.
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