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Cancer Res. 2004 Oct 15;64(20):7399-404.
PAX5 expression in acute leukemias:
higher B-lineage specificity than CD79a and
selective association with t(8;21)-acute myelogenous
leukemia.
Tiacci E, Pileri S, Orleth A, Pacini R, Tabarrini
A, Frenguelli F, Liso A, Diverio D, Lo-Coco F,
Falini B.
Institutes of Hematology and Internal Medicine,
University of Perugia, Perugia, Italy.
The transcription factor PAX5
plays a key role in the commitment of hematopoietic
precursors to the B-cell lineage, but its expression
in acute leukemias has not been thoroughly
investigated. Hereby, we analyzed routine biopsies
from 360 acute leukemias of lymphoid (ALLs) and
myeloid (AMLs) origin with a specific anti-PAX5
monoclonal antibody. Blasts from 150 B-cell ALLs
showed strong PAX5 nuclear expression, paralleling
that of CD79a in the cytoplasm. Conversely, PAX5 was
not detected in 50 T-cell ALLs, including 20 cases
aberrantly coexpressing CD79a. Among 160
cytogenetically/molecularly characterized AMLs, PAX5
was selectively detected in 15 of 42 cases bearing
the t(8;21)/AML1-ETO rearrangement. Real-time
reverse transcription-PCR studies in t(8;21)-AML
showed a similar up-regulation of PAX5 transcript in
all of the 8 tested samples (including 4 cases that
were negative at anti-PAX5 immunostaining),
suggesting that PAX5 is expressed in t(8;21)-AML
more widely than shown by immunohistochemistry.
Interestingly, PAX5(+) t(8;21)-AML also expressed
CD79a and/or CD19 (major transcriptional targets of
PAX5 in B-cells) in 10 of 12 evaluable cases. Our
results indicate that PAX5 is a more specific marker
than CD79a for B-cell ALL diagnosis. Moreover, among
AMLs, PAX5 expression selectively clusters with
t(8;21), allowing its immunohistochemical
recognition in a proportion of cases, and likely
explaining a peculiar biological feature of this
subset of myeloid leukemias, i.e. the aberrant
expression of B-cell genes.
PMID: 15492262 [PubMed - indexed for
MEDLINE]