Scientists in the United States, working with mice, have found a new type of stem cell in the prostate gland and shown that mutations in it can cause cancer, a study released Wednesday says.
The discovery boosts evidence that cancers can be caused by modifications in stem cells, the dynamic precursor cells that develop into and replenish the body's specific tissues, it says.
It also appears to resolve a mystery about the origin of prostate cancer, and could open new pathways for treatment of the deadly disease.
"This is a new stem cell in the prostate, and our research shows that it can serve as a cell of origin for prostate cancer," said Cory Abate-Shen, a professor at the Columbia University College of Physicians and Surgeons and New York and a co-author of the study.
Prostate cancer is the second most common cancer among men, claiming half a million lives each year worldwide, according to the World Health Organisation (WHO).
The new stem cell, known by the acronym of CARN, is found inside a type of tissue called the epithelium, which is also present in other parts of the body.
More specifically, they are located in a region called the luminal layer, where cancers of the prostate are known to occur.
But until now, the only stem cell found in the epithelium were in the so-called basal layer.
Hence the conundrum: if stem cells were implicated in the growth of cancerous tumours, as growing evidence suggests, how the cancer moved from one layer to the next remained unexplained.
To see if mutant versions of the newly-found cell can cause tumours, scientists deleted a cancer suppressor gene called Pten in laboratory mice.
"Pten is a very critical gene for cancer. It is a major tumour suppressor and is especially important for prostate cancer" in humans, Abate-Shen told AFP.
Male mice with the mutant version of the luminal stem cells all developed tumours, but "control" mice whose Pten gene had not been suppressed were all healthy.
The study, led by Abate-Shen's husband, Michael Shen, of Columbia Medical Center, is published in the British-based journal Nature.
The findings should help scientists better understand the link between stem and cancer cells, the authors said.
"Alterations in most cells in a tissue may not be a problem for carcinogenesis," or the rise of cancer, said Abate-Shen.
"But if those alterations occur in stem cells, then they give rise to tumours because those are the cells that proliferate and give rise to the rest of the cells."
The researchers cautioned against drawing hasty conclusions for humans on the basis of mouse models. It is unclear whether CARNs exist in the human prostate and if, so, whether they unleash cancer.
The next step is to compare normal and cancerous cases in mice, and then relate those findings to human cancer, said Abate-Shen.
The main function of the prostate gland is the secretion of a slightly alkaline fluid that helps semen neutralise the acidity of the vaginal tract, prolonging the lifespan of sperm as they seek an egg to fertilise.