Down Syndrome Mutation Helps Leukemia Survival

Gene Creates Leukemia Risk, Yet Boosts Chemo's Effectiveness

By Jeanie Lerche Davis
WebMD Health News

Feb. 1, 2005 -- Children with Down syndrome are more likely to get leukemia. But they also respond better to treatment. Now scientists know why.

For children with Down syndrome, leukemia treatment is more successful than for other kids. It's likely due to a genetic mutation found only in Down syndrome children, new research shows. However, the same mutation also increases the kids' leukemia risk.

The study appears in this week's edition of the Journal of the National Cancer Institute.

Children's cancer researchers have consistently reported the pattern. A specific type of acute myeloid leukemia (AML) called acute megakaryocytic leukemia (AMkL) is the most common type of AML in young children with Down syndrome.

Following chemotherapy treatments, Down syndrome kids fare better than other kids treated for AMkL.

The Down syndrome children have substantially higher survival rates and lower relapse rates than the other kids, writes lead researcher Yubin Ge, MD, with the Experimental and Clinical Therapeutics Program at the Barbara Ann Karmanos Cancer Institute in Detroit.

Recent studies have identified a genetic mutation in virtually all Down syndrome children who have AMkL. Non-Down syndrome kids with AML don't have this mutation. The mutation, known as the 40-kDa GATA1 protein, may be responsible for the survival difference, he writes.

Ge and his colleagues investigated this mutation in a series of laboratory experiments. They found that the GATA1 mutation seems to contribute to the Down syndrome kids' greater sensitivity to a specific cancer fighting drug, called cytosine arabinoside, which is used in treating AMkL.

Cells with the normal GATA1 protein were 8 to 17 times less sensitive to the chemotherapy drug, reports Ge. They were also 15 to 25 times less sensitive to gemcitabine, another leukemia drug.

Tests of cells taken from 16 newly diagnosed Down syndrome children (including 12 AMkL patients) and 56 non-Down syndrome children with AML showed that 14 of 16 Down syndrome kids had the GATA1 mutation.

This GATA1 mutation is a double-edged sword. It may increase a child's risk for leukemia, but it may also contribute to the high survival and low relapse rates of this unique group of Down syndrome patients, writes Ge.

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