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Differential constitutive activation between STAT‐related proteins and MAP kinase in primary acute myelogenous leukaemia
Author(s) -
Hayakawa Fumihiko,
Towatari Masayuki,
Iida Hiroatsu,
Wakao Hiroshi,
Kiyoi Hitoshi,
Naoe Tomoki,
Saito Hidehiko
Publication year - 1998
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.1998.00720.x
Subject(s) - phosphorylation , jak stat signaling pathway , stat5 , cancer research , map2k7 , janus kinase , biology , tyrosine phosphorylation , microbiology and biotechnology , protein kinase a , cyclin dependent kinase 2 , receptor tyrosine kinase
Many cytokines and growth factors stimulate multiple signal transduction pathways essential for proliferation in human acute leukaemia cells, including a mitogen‐activated protein (MAP) kinase pathway and a Janus kinase (JAK)‐STAT (signal transducers and activators of transcription) pathway. We have previously shown constitutive activation of MAP kinase in approximately 50% of acute myelogenous leukaemia (AML) samples. Recently, STAT proteins have been reported to be constitutively activated in 10–20% of AML cases. STAT3 and STAT5 are the main STAT proteins activated in haemopoietic progenitors in response to cytokines such as IL‐3, GM‐CSF, erythropoietin and thrombopoietin. Although the possibility of STAT1 protein as a substrate for MAP kinase at a serine residue has been suggested, the cross‐talk between STATs and MAP kinase pathways in vivo , especially in leukaemia cells, remains unknown. We examined the phosphorylation of STAT3 and STAT5 at the tyrosine residues in AML samples in which MAP kinase activity had already been found. 40/50 primary AML cases (80%) exhibited constitutive tyrosine phosphorylation of STAT5. Electrophoretic mobility shift assay showed DNA binding activity of STAT5 correlated with tyrosine phosphorylation of STAT5. Similarly, with respect to STAT3, 17/23 cases examined (74%) showed constitutive tyrosine phosphorylation of STAT3. In addition, we examined the tyrosyl‐phosphorylation of STAT5 isoforms, STAT5A and STAT5B, in 20 AML cases, and found selective STAT5B phosphorylation in the absence of STAT5A phosphorylation in three cases. Furthermore, in certain AML cases, constitutive activation of MAP kinase and STAT proteins occurred independently. No significant correlation of MAP kinase activation was observed with either tyrosine phosphorylation of STAT3/STAT5 or positive DNA binding of STAT proteins. These results suggest that constitutive activation of STAT proteins occurs commonly and that the causes of constitutive activation of these two major cascades are heterogenous in AML.