Posted Wednesday, August 10, 2011 --- 4:20 p.m.

NEW YORK (AP) -- Scientists are reporting the first clear success with a new approach for treating leukemia.

It involves turning the patients' own blood cells into assassins that hunt and destroy cancer cells.

It's only been done in three patients so far. Two of them appear to be cancer-free up to a year later, and a third is improving but still has some cancer.

A gene therapy expert at the University of Pennsylvania, Dr. Carl June, says, "We were surprised it worked as well as it did."

He says researchers still need to see how long the remissions last.

June says researchers at Penn want to test the gene therapy technique in pancreatic and ovarian cancer, while other institutions are looking at prostate and brain cancer.

The study is published today in two journals (New England Journal of Medicine and Science Translational Medicine.)

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