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The gene expression signature of anagrelide provides an insight into its mechanism of action and uncovers new regulators of megakaryopoiesis
Author(s) -
Ahluwalia M.,
Butcher L.,
Donovan H.,
KillickCole C.,
Jones P. M.,
Erusalimsky J. D.
Publication year - 2015
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.12959
Subject(s) - anagrelide , megakaryocytopoiesis , biology , cancer research , thrombopoiesis , atf4 , gene expression , transcription factor , microbiology and biotechnology , gene , megakaryocyte , essential thrombocythemia , genetics , haematopoiesis , platelet , immunology , stem cell
Summary Background Anagrelide is a cytoreductive agent used to lower platelet counts in essential thrombocythemia. Although the drug has been known to selectively inhibit megakaryopoiesis for many years, the molecular mechanism accounting for this activity is still unclear. Objectives and Methods To address this issue we have compared the global gene expression profiles of human hematopoietic cells treated ex‐vivo with and without anagrelide while growing under megakaryocyte differentiation conditions, using high‐density oligonucleotide microarrays. Gene expression data were validated by the quantitative polymerase chain reaction and mined to identify functional subsets and regulatory pathways. Results We identified 328 annotated genes differentially regulated by anagrelide, including many genes associated with platelet functions and with the control of gene transcription. Prominent among the latter was TRIB 3, whose expression increased in the presence of anagrelide. Pathway analysis revealed that anagrelide up‐regulated genes that are under the control of the transcription factor ATF 4, a known TRIB 3 inducer. Notably, immunoblot analysis demonstrated that anagrelide induced the phosphorylation of eIF 2α, which is an upstream regulator of ATF 4, and increased ATF 4 protein levels. Furthermore, salubrinal, an inhibitor of eIF 2α dephosphorylation, increased the expression of ATF 4‐regulated genes and blocked megakaryocyte growth. Conclusions These findings link signaling through eIF 2α/ ATF 4 to the anti‐megakaryopoietic activity of anagrelide and identify new potential modulators of megakaryopoiesis.