Birth of cloned mule offers clues in the hunt for prostate cancer treatment

A baby mule called Idaho Gem has made history by being the first clone of an equine animal to be successfully born.

A baby mule called Idaho Gem has made history by being the first clone of an equine animal to be successfully born.

The four-week-old cloned mule - a cross between a male donkey and a female horse - is also unique as the first clone of a sterile, hybrid animal.

Idaho was one of 14 successful pregnancies out of 113 attempts at transferring cloned embryos into surrogate mothers - two other mares are expected to deliver twins of Idaho in June and August.

Scientists cloned Idaho from the brother of a world champion racing mule called Taz. His birth on 4 May is revealed today in the journal Science.

Instead of taking cells directly from Taz, scientists took cells from a 45-day-old foetus - the naturally conceived offspring of Taz's parents - and used these cells for the cloning process. Researchers wanted to use young cells rather than ones from an adult animal.

Cloning horses and donkeys has proved difficult but in theri work the scientists have also developed a technique that they believe will aid the treat-ment of prostate cancer in humans. Prostate cancer is unheard of among stallions and scientists think this has something to do with the low levels of calcium in the cells of horses. Dr Gordon Woods, professor of veterinary science at the University of Idaho, said the successful cloning came about after boosting the levels of calcium in the growth medium of the cloned embryos. "We increased the calcium in the medium holding the embryos and saw a seven-fold increase in our week-two pregnancy rates," Professor Woods said.

Calcium, or more correctly the difference in calcium between the outside and the inside of cells in humans and horses, could explain the differences in cancer rates, he added. "The mortality rate for horses with metastatic [spreading] cancer is 8 per cent for all cancers and zero per cent for prostate cancer," he said.

"By comparison, the mortality rate in humans is approximately 24 per cent for all cancers, of which 13 to 14 per cent are for prostate cancer."

The scientists believe drugs that can interfere with calcium levels could help to stem the spread of cancer in humans by making them behave more like the cells of horses, which are less active than their human equivalents. "There are electrifying similarities between cancer metastasis and embryo division. We've identified a suppresser of intracellular calcium and believe its deficiency is the root cause of abnormally high intracellular calcium," Professor Woods said.