A NEW SOURCE OF ISLETS FROM A SURPRISING SOURCE

October 1, 2002

UCSF, Diabetes Center - All cells in the body are capable of dividing numerous

times, producing two cells from one in a process called mitosis. However, each

cell also has an internal clock that tells it when it should stop dividing.

These clocks are small pieces of DNA at the end of chromosomes known as

" telomeres. " Each time a cell divides, its telomeres get shorter - when the

telomeres become too short, it is a signal that the cell should stop dividing.

This is a significant roadblock in developing new sources of islets in the

laboratory. Starting with cells isolated from a human pancreas, the trick is to

get them to differentiate and divide into fully- functioning islet cells.

However, each division will shorten the telomeres a little more, effectively

pushing the cells closer and closer to the " stop dividing " signal and limiting

the number of islets that can be grown.

Dr. McMahon, PhD, thinks he may just have a way around this internal

clock. And the source of his optimism comes from a rather surprising place:

cancer cells.

How can cancer cells help? One of the hallmarks of cancer cells is their

immortality - they can divide forever. In fact, it is now known that cancer

cells have high levels of a specialized enzyme called " telomerase " that replaces

the ends of the telomeres so that they never shorten enough to relay their stop

dividing signal. Hence, one cancer cell could potentially divide forever - which

is just the situation we need to develop a new source of islets.

Building on the pioneering work of UCSF's own Dr. Blackburn, Dr.

McMahon hopes that stem cells identified from duct cells located within the

human pancreas can be coaxed into becoming insulin-producing cells, while at the

same time immortalized with telomerase. The resulting cells would then look and

act like insulin producing beta cells, however, they would be able to divide

continuously, creating a limitless source of new, laboratory grown islet cells

suitable for transplantation.

This new collaboration comes as a direct result of the new Islet and Cellular

Transplantation Facility. Dr. McMahon, a highly regarded professor in UCSF's

Comprehensive Cancer Center and Cancer Research Institute, will study unused or

unsuitable portions of pancreases destined for islet transplants - not a single

piece of a donor pancreas will be wasted! eUpdate will keep you posted on the

progress of Dr. McMahon's research and all the other developments in and around

the new Islet and Cellular Transplantation Facility.

Mark E. Armstrong

NW Rep, PAI

casca@...

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