THE "NEW" PROSTATE CANCER INFOLINK

On Tuesday this week we reported on a study suggesting that some prostate cancers might be caused by the XMRV virus. Now comes a study suggesting that specific types of stems cells may be implicated in the development of some prostate cancers.

As with many science reports of this type — based on animal studies to date — there are an awful lot of “ifs” to this report, but data published in Nature by Wang et al. do seem to support the possibility that a “luminal” epithelial stem cell is a cell of origin for prostate cancers of some types. The type of cell in question is known as a “castration-resistant Nkx3-1-expressing” cell or a CARN cell. What Wang et al. actually demonstrated in their studies is that a known regulator of prostate epithelial differentiation, the Nkx3-1 gene, marks a stem cell population that functions during prostate regeneration. And to date they have only shown this in mice, not in man.

So — first of all — what is a “luminal” epithelial cell?

The epithelium is a type of tissue that lines the cavities and surfaces of structures throughout the body. It lies above the connective tissues and comes in many different types. Your skin, for example, is largely comprised of epithelial cells of various types. The prostate contains epithelial tissue and therefore epithelial cells. “Luminal” cells are normally found in the “luminal” layer of the epithelium, which is just one of several layers. Another is the “basal” layer which is made up of basal epithelial cells.

So …  we have known for a long time that cancers of the prostate occur in the luminal layer of epithelial cells, but most  tumors were believed to originate from basal rather than luminal stem cells. This led to a question. If stem cells were implicated in the growth of cancerous tumors, as growing evidence suggests, how did the cancer move from the basal layer to the luminal layer?

What this study has shown is that, at least in certain types of mice, there is a  second type of stem cell population that is luminal rather than basal. These stem cells can become cancerous if the action of a particular tumor-suppressing gene is lost. And we already knew that this tumor-suppressing gene is often mutated in human prostate cancers. What the researchers will need to show next is that the same kinds of stem cells are found in human prostate glands. If that proves to be the case, we may have considerable cause to believe that at least some types of prostate cancer do originate in the luminal layer of prostate epithelial cells.

What’s the “take away” from all of this?

We are getting closer to understanding how different types of prostate cancer are triggered at the very beginning. It is becoming increasingly clear that there may be several types of trigger that may then lead to different types of prostate cancer. Dr. Simon of the Prostate Cancer Foundation believes there may, in fact, be as many as 17 different types of prostate cancer. If we can work out how prostate cancers start, it ought to become a great deal easier to work out how to identify them early on and prevent them from progressing years before they become clinically important — but we still have a long, long way to go.

Filed under: Prevention Tagged: | cause, origin, stem cells