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Leukemia mutation gene identified

9/14/2010, 5 p.m.

LOS ANGELES - Researchers at Childrens Hospital Los Angeles announced the identification of a mutated gene which plays a role in the development of B-precursor leukemia, the most common form of childhood cancer.

The study was led by Dr. Fatih M. Uckun, leader of the Developmental Therapeutics Program at the Institute of Pediatric Clinical Research at Childrens Hospital Los Angeles, and published online in Proceedings of the National Academy of Sciences, the Academy's official journal.

The mutated gene, CD22, leads to development of B-precursor leukemia in children, especially in infants, according to Uckun.

B-precursor leukemia, also known as ALL, is a type of leukemia where an abundance of immature white blood cells appear in the blood and bone marrow.

The disease historically had a high mortality rate with nearly 80 percent of children failing to survive long term, but with better treatment and early diagnosis those numbers have been reversed with nearly 80 percent surviving long term, Uckun said.

In the study, scientists looked at leukemia cells from 17 children with ALL and identified a "previously unknown gene expression signature'' associated with mutations of the CD22 gene, Uckun said.

"The physiologic function of normal CD22 is to regulate immune responses and prevent inappropriately strong or prolonged stimulations of our immune system,'' "This receptor is completely defective in infant leukemia cells, causing signaling pathways to remain in "overdrive," which contributes to the aggressive nature of infant leukemia cells,"Uckun stated.

This finding represents the first discovery of a specific CD22 defect in a human cancer, Uckun said.

"... Better understanding of the biological basis of ALL could lead to the development of ... more effective treatment programs for poor risk groups of children with ALL, particularly infants,'' said Dr. Stuart Siegel, director of the Childrens Center for Cancer and Blood Diseases at Childrens Hospital Los Angeles.

Researchers hope identification of the defective gene will enable them to refine diagnostic techniques to better identify families who may be at risk for ALL.