Wednesday, February 21, 2007

Cancer Is A Stem Cell Issue

Stem cells are at the heart of some, if not all, cancers ScienceDaily 2/22/07 "Mounting evidence implicates a clutch of rogue stem cells brandishing ‘epigenetic’ marks as the main culprits in cancer. Wiping out tumours for good, some biologists believe, depends on uprooting these wayward stem cells... "To be successful in cancer therapy you need to target these stem cells: they are intrinsically resistant to chemotherapy.”...Polycomb proteins have emerged as key players in cancer pathogenesis. They are powerful epigenetic regulators that normally silence genes without altering the cell’s DNA. Compounds that regulate polycomb could result in novel anticancer drugs that shrink malignant tissue, and prevent cancer recurrence, a common problem with most chemotherapies...That tumours and stem cells have much in common has been known for many years. Both self-renew and both spawn many different types of cells. But only recently, new techniques have enabled biologists to identify stem cells buried in tumours...stem cells in cancerous tissues are locked in an immature state in which they carry on multiplying instead of maturing into specific tissues...Some resistant cancer cells don’t listen to the ‘stop’ signal any more,” he explains. That stop sign is delivered by the polycomb proteins. They silence several genes at once by affecting the way the DNA is compacted into chromatin fibres, without altering the DNA sequence. "

More at ScienceDaily. This is a huge story and we'll obviously be hearing much more on polycomb proteins and the search for agents that destroy rogue stem cells without destroying the crucially important normal stem cells that exist throughout our lives.

More on polycomb proteins here. Not many good links on these yet and Wiki only has a stub. This should change very soon. Interesting fact that the polycomb gene was discovered almost 61 years ago and only recently are we discovering the significance.

"Previous studies showed that the Polycomb proteins are essential for early development. If the genes that code for Polycomb proteins are lost in embryonic stem cells, the cells begin to develop in an uncontrolled fashion and lose their unique properties. Knowing that Polycomb is key to an embryonic stem cell's identity,...Polycomb, it turns out, represses entire networks of genes that are essential for later development, the same genes that begin to turn on as a stem cell starts to differentiate. That explains why embryonic stem cells immediately grow into specialized cells when Polycomb proteins are lost. "Polycomb is dynamic," says Jaenisch, "working with other molecules to silence genes and then gradually allowing them to activate during development. It is also the founding ingredient for development, so knowing how it works and which genes it interacts with will be invaluable for understanding these amazing cells." "We're continuing to map the regulatory network that controls stem-cell state and development," says Young. "We hope to use this map to guide the fate of cells so that they can be used to replace diseased or damaged cells.""

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