Prostate cancer: the clue to its origins?

Could scientists have discovered the clue to what makes prostate cancer grow? That's the suggestion being made by researchers at York University, who have found the cells that appear to "drive" prostate cancer by ordering surrounding cells to turn malignant, and have been able to grow these cells in the laboratory. This raises the possibility that pharmaceutical companies could develop treatments to kill the offending 'parent' cells.

The "parent" cells are actually stem cells. Healthy stem cells act as the building blocks of life, giving rise to a range of cells responsible for regenerating our organs, tissues and red blood cells. Now cancer specialists say that stem cells may play a leading role in prostate cancer, too.

This week scientists at the Yorkshire Cancer Research Unit, led by Professor Norman Maitland and Dr Anne Collins, both biologists, have reported that cancer stem cells work in a similar way to healthy stem cells. Writing in the American journal Cancer Research, they say that although only 0.1 per cent of the cells they took from prostate tumours were cancer stem cells, this small number had been able to direct other, lesser cells to develop into "colonies" of tumours four times their own number.

This is "groundbreaking" work, according to Jack Schalken, professor of experimental urology at Radboud University in the Netherlands. He says: "Identifying the cancer stem cell is the most important element: stem cells feed the whole repertoire of cancer cells that complete the tumour."

Hing Leung, professor of urological oncology at Newcastle University, says that the concept of cancer stem cells is "the equivalent of finding the engine room' that drives cancer to grow, spread and resist treatment such as chemotherapy and radiotherapy". He adds: "Finding such stem cells is like looking for a very small needle in a rapidly growing haystack. This study has identified the first hints' that such novel stem cells do exist in prostate cancer.

"This is likely to open up new avenues to understand better the underlying biology of cancer. It may also highlight drugable' targets for developing better medicine."

Professor Maitland explains that most cancer treatments try to kill off the bulk of tumour cells, leaving behind a stem cell population. But if you can kill the roots, "you kill the cancer for good".

Professor Schalken suggests that Professor Maitland's work will be the catalyst for treatments that may, in time, have a similar impact to the development of hormone therapy in the 1950s. Until then, the only treatment for prostate cancer was surgery.

Professor Maitland is cautious about when a treatment might become available but believes that cyclopamine, a drug undergoing human trials in the US, could be "a ready-made therapy" because it has been shown to reduce tumours, possibly by preventing stem cells from communicating with surrounding cells.

Until now the drug has been used blind, says Professor Maitland. Researchers have not been able to target it at the cancer stem cells, which can mean that it has the potential to kill the normal, healthy stem cells that renew our bodies. This is clearly a problem because without stem cells organs such as the liver would shrivel up.

Both professors are wary of raising false hopes, but Professor Maitland suggests that at a time when treatments are developed more and more quickly, an effective treatment could be only years away.

Chris Hiley, head of research at the Prostate Cancer Charity, says: "The research and discoveries in prostate cancer stem cells are exciting.

"There is usually the fear that scientists can overstate their findings, but Professor Maitland is a very measured researcher and is clued up about making his findings relevant for patients suffering with prostate cancer. It is very promising."