Epigenetic heterochromatin markers distinguish terminally differentiated leukocytes from incompletely differentiated leukemia cells in human blood.
OBJECTIVE
During terminal cell differentiation, nuclear chromatin becomes condensed and the repertoire of epigentic heterochromatin proteins responsible for chromatin condensation is dramatically changed. In order to identify the chromatin regulatory factors associated with incomplete cell differentiation and impaired chromatin condensation in hematological malignancies, we examined expression levels of major heterochromatin proteins in normal blood cells and cells derived from a number of chronic and acute myeloid leukemia patients exhibiting different degrees of differentiation.


METHODS
We used immunoblotting and immunofluorescence to examine the levels and localization of epigenetic heterochromatin factors in isolated cell nuclei and fractionated peripheral blood cells.


RESULTS
While the major epigenetic heterochromatin factor, histone H3 methylated at lysine 9, is present in all cell types, its main counterparts, nonhistone proteins, heterochromatin proteins 1 (HP1) alpha, beta, and gamma, are dramatically reduced in peripheral blood leukocytes of normal donors and chronic myeloid leukemia patients, but are substantially increased in the blood of accelerated phase and blast crisis patients. In the terminally differentiated cells, nuclear chromatin accumulates a nucleocytoplasmic serpin, monocyte and neutrophil elastase inhibitor (MNEI). HP1 and MNEI levels inversely correlate in a number of normal and leukemia myeloid cells and show strikingly opposite coordinated changes during differentiation of U937 cell line induced by retinoic acid.


CONCLUSIONS
Our results suggest that repression of HP1 and accumulation of MNEI are linked to terminal cell differentiation and that their levels may be monitored in blood cell populations to detect transitions in cell differentiation associated with leukemia progression and treatment.
Popova
Evgenya Y
EY
Department of Biochemistry and Molecular Biology, Penn State University College of Medicine, Milton S. Hershey Medical Center, Hershey, 17033., USA.
Claxton
David F
DF
Lukasova
Emilie
E
Bird
Phillip I
PI
Grigoryev
Sergei A
SA
D000970:Antineoplastic Agents / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000378:metabolism; D001752:Blast Crisis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D044127:Epigenesis, Genetic / Q000187:drug effects; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D018922:HL-60 Cells; D006570:Heterochromatin / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006657:Histones / Q000378:metabolism; D006801:Humans; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007962:Leukocytes / Q000378:metabolism* / Q000473:pathology; D009363:Neoplasm Proteins / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D015843:Serpins / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology; D020298:U937 Cells
D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D006657:Histones; D009363:Neoplasm Proteins; D011506:Proteins; D015843:Serpins; C075177:SERPINB1 protein, human; D014212:Tretinoin