A newly identified type of stem cell may cause some cases of prostate cancer, research on mice suggests.

对老鼠的研究显示，一种新被发现的干细胞可能引起前列腺癌。

Prostate epithelial stem cells (green) may trigger cancer

The cells, found among those which line the inner cavity（洞，腔） of the prostate gland¹（前列腺）, can produce copies of themselves, and other, more mature cell types.

But researchers showed that when the cells were deliberately² mutated（变异，突变） by switching off a tumour³ suppressor gene⁴ they rapidly formed tumours⁵.

The Columbia University study appears in the journal Nature.

Prostate cancer is the most common cancer in men in the UK.

Each year around 34,000 men are diagnosed with the disease, and around 10,000 die from it.

Stem cells, the body's master cells which can form many different types of tissue, have previously⁶ been implicated⁷（纠缠，暗示） in other forms of cancer, such as leukaemia（白血球过多症）.

Their possible role in prostate cancer has been the subject of speculation⁸ for many years.

The cells have a long lifespan in the prostate and exist to generate new tissue, so in theory if they mutate and start to grow in an unregulated way they have the potential to be very damaging.

The newly identified cells - a type of luminal（内腔的，细胞腔的） epithelial（上皮的） stem cell - do not rely on androgens（雄激素） - the male sex hormones⁹ that control prostate growth - to thrive.

Drug resistance

This may give a clue as to why prostate cancer often becomes resistant¹⁰ to treatments designed to regulate these androgens in the later stages of the disease.

However, researcher Dr Michael Shen stressed more work was needed to establish whether the cells existed in humans, and could trigger cancer.

He said: "While there does appear to be increasing evidence suggesting that normal stem cells may serve as an origin for cancer, the 'cancer stem cell' model remains¹¹ far from proven, especially in solid tumours such as prostate.

"In principle, therapies directed at putative¹²（假定的） cancer stem cells may be beneficial, but this field is still at a very early stage."

Dr Helen Rippon, of The Prostate Cancer Charity, said: "It will be some time before we know if or how these findings apply to humans.

"However, understanding the very earliest stages of prostate cancer development and the cells involved is critical if we are to develop better ways to detect and treat the disease."

Dr Owen Sansom, a stem cell researcher from Cancer Research UK's Beatson Institute for Cancer Research, said the study raised the possibility of developing new treatments to tackle（处理，抓住） prostate cancer that was resistant to hormone-based therapy.

Sex disease link

In a separate study, a team from Harvard School of Public Health has found a strong association between a common sexually transmitted infection, Trichomonas vaginalis（阴道毛滴虫）, and advanced lethal¹³ prostate cancer.

The National Cancer Institute study suggests the infection could be a source of inflammation（红肿，炎症） which might trigger the cancer.

Trichomonas vaginalis infects an estimated 174 million people globally each year, but in up to three-quarters of infected men it produces no obvious symptoms.

Researchers analysed blood samples from 673 men with prostate cancer, comparing them with a similar number of samples from men who were free from the disease.

They found Trichomonas vaginalis infection was associated with a more than two-fold increase in the risk of prostate cancer that was advanced stage at diagnosis¹⁴, and a nearly three-fold increase in prostate cancer that would result in death.