Activation of integrin-linked kinase is a critical prosurvival pathway induced in leukemic cells by bone marrow-derived stromal cells.
Integrin-linked kinase (ILK) directly interacts with beta integrins and phosphorylates Akt in a phosphatidylinositol 3-kinase (PI3K)-dependent manner. In this study, we examined the functional role of ILK activation in leukemic and bone marrow stromal cells on their direct contact. Coculture of leukemic NB4 cells with bone marrow-derived stromal mesenchymal stem cells (MSC) resulted in robust activation of multiple signaling pathways, including ILK/Akt, extracellular signal-regulated kinase 1/2 (ERK1/2), signal transducers and activators of transcription 3 (STAT3), and Notch1/Hes. Blockade of PI3K or ILK signaling with pharmacologic inhibitors LY294002 or QLT0267 specifically inhibited stroma-induced phosphorylation of Akt and glycogen synthase kinase 3beta, suppressed STAT3 and ERK1/2 activation, and decreased Notch1 and Hes1 expression in leukemic cells. This resulted in induction of apoptosis in both leukemic cell lines and in primary acute myelogenous leukemia samples that was not abrogated by MSC coculture. In turn, leukemic cells growing in direct contact with bone marrow stromal elements induce activation of Akt, ERK1/2, and STAT3 signaling in MSC, accompanied by significant increase in Hes1 and Bcl-2 proteins, which were all suppressed by QLT0267 and LY294002. In summary, our results indicate reciprocal activation of ILK/Akt in both leukemic and bone marrow stromal cells. We propose that ILK/Akt is a proximal signaling pathway critical for survival of leukemic cells within the bone marrow microenvironment. Hence, disruption of these interactions by ILK inhibitors represents a potential novel therapeutic strategy to eradicate leukemia in the bone marrow microenvironment by simultaneous targeting of both leukemic cells and activated bone marrow stromal cells.
Tabe
Yoko
Y
Section of Molecular Hematology and Therapy, Department of Blood and Marrow Transplantation, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
Jin
Linhua
L
Tsutsumi-Ishii
Yuko
Y
Xu
Yuanyuan
Y
McQueen
Teresa
T
Priebe
Waldemar
W
Mills
Gordon B
GB
Ohsaka
Akimichi
A
Nagaoka
Isao
I
Andreeff
Michael
M
Konopleva
Marina
M
D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D001854:Bone Marrow Cells / Q000166:cytology / Q000201:enzymology; D002450:Cell Communication / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D002867:Chromones / Q000494:pharmacology; D018920:Coculture Techniques; D004789:Enzyme Activation / Q000187:drug effects; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D053612:Janus Kinases / Q000378:metabolism; D015473:Leukemia, Promyelocytic, Acute / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000201:enzymology*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D051880:Receptors, Notch / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D017154:Stromal Cells / Q000166:cytology / Q000201:enzymology; D000072056:Transcription Factor HES-1; D000099200:Scaffold Protein ILK
D051792:Basic Helix-Loop-Helix Proteins; D002867:Chromones; D018398:Homeodomain Proteins; D053612:Janus Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D051880:Receptors, Notch; D050796:STAT3 Transcription Factor; D000072056:Transcription Factor HES-1; D000099200:Scaffold Protein ILK; C494086:STAT3 protein, human; C078493:HES1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one