Differential expression levels of the heat shock protein 27 isoforms in
pediatric normal, nonleukemic and common acute lymphoblastic leukemia B-
cell precursors
PS Madsen, P Hokland, N Clausen, J Ellegaard and M Hokland
University Department of Medicine and Hematology, Aarhus Amtssygehus,
Denmark.
Heat shock protein 27 (hsp27) may function as a regulator of microfilament
dynamics and may participate in signal transduction pathways of different
cell growth regulators, with the mitogen- activated protein
kinase-activated protein (MAPKAP) kinase 2 being a major enzyme responsible
for its phosphorylation. Using two-dimensional gel electrophoresis, we have
compared the expression levels of two hsp27 isoelectric variants (hsp27
isoforms) M2 (molecular weight, 26 kD; isoelectric point, 6.02) and M3
(molecular weight, 26 kD; isoelectric point, 5.60) in pediatric bone marrow
CD19+CD10+B-cell precursors (BCPs) purified from either common acute
lymphoblastic leukemia (c-ALL) patients, normal donors, or non-c-ALL
patients. Compared with normal BCPs, we found increased hsp27 expressions
(M2 isoform) (by a factor 5 to 9 of mean level) in c-ALL as well as in non-
c-ALL (nonleukemic) precursors. Though increased phosphorylation of hsp27
(M3 isoform) was observed in BCPs from c-ALL patients at relapse (by a
factor 3 of mean level compared with normal BCPs and precursors from c-ALL
at diagnosis), which might represent a differential enzymatic activity,
this was not distinguishable from that of non-c-ALL patients. Therefore,
our studies suggest constitutive differences of hsp27 isoforms between
pediatric leukemic BCPs and their relatively low- expressing,
immunophenotypically normal bone marrow counterparts. In light of the
occasional and possibly transient increase of hsp27 expression during
nonleukemic BCP differentiation and the possible role of hsp27 in signal
transduction to microfilaments, these differences might be of considerable
biologic interest and of importance in future studies of regulated normal
or dysregulated leukemic hematopoietic cellular differentiation.
Volume 85,
Issue 2,
pp. 510-521,
01/15/1995
Copyright © 1995 by The American Society of Hematology