Gene Chips Used to Identify Third Form of Pediatric Leukemia

Gene Chips Used to Identify Third Form of Pediatric Leukemia

BOSTON—A rare pediatric leukemia, previously thought to be a subset
of acute lymphoblastic leukemia (ALL), is actually a distinct form of the
disease, according to investigators who used gene chips to create and contrast
genetic profiles of cancer cells.

Scott Armstrong, MD, PhD, of Dana-Farber Cancer Institute, and his
colleagues call the disease mixed-lineage leukemia (MLL) for a chromosomal translocation of the MLL gene.

Different Gene Expression Pattern

They reported in the January 2002 issue of Nature Genetics that the
condition has a dramatically different pattern of gene expression from that of
both ALL and acute myelogenous leukemia (AML), in addition to the
distinguishing chromosomal translocation.

MLL affects infants in their first year; fewer than 100 babies annually are
affected in the United States. It is especially aggressive, with recurrences
leading to fatalities in about 60% of cases.

By 1999, a number of pediatric oncology groups had noticed that cells with
the MLL translocation were more sensitive to cytarabine than other ALL cells,
said Dr. Armstrong, who is also instructor in pediatric oncology, Harvard
Medical School. The groups began experimenting with more intensive therapy than
is standard for ALL, but have yet to determine whether outcomes are improved.

"You probably should think of treating MLL patients with hybrid therapy
for ALL and AML," Dr. Armstrong told ONI. "We’re treating patients
with a backbone of ALL therapy, but with much more cytarabine than normally
would be used to treat ALL."


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