β2 integrin–derived signals induce cell survival and proliferation of AML blasts by activating a Syk/STAT signaling axis

Abstract

Key Points• Integrin signaling promotes proliferative signals in AML cells that are mediated by the kinase Syk and the transcription factors STAT3 and STAT5.Spleen tyrosine kinase (Syk) induces cell survival and proliferation in a high proportion of acute myeloid leukemia (AML) blasts, but the underlying molecular events of Syk signaling have not been investigated. Proteomic techniques have allowed us to identify the multiprotein complex that is nucleated by constitutively active Syk in AML cells. This complex differs from the B-lymphoid Syk interactome with respect to several proteins, especially the integrin receptor Mac-1, the Fc-g receptor I (FcgRI), and the transcription factors STAT3 and STAT5. We show in several AML cell line models that tonic signals derived from the Fc-g chain lead to Syk-dependent activation of STAT3 and STAT5, which in turn induces cell survival and proliferation. Moreover, stimulation of Mac-1 or FcgRI intensifies the constitutive Syk-mediated STAT3/5 activation in AML cells, a scenario likely to take place in the bone marrow niche. In accordance with these findings, we observed that b 2 integrins, including Mac-1, trigger proliferation of AML cells in an AML cell/stroma coculture model. Taken together, we identified an oncogenic integrin/Syk/STAT3/5 signaling axis that might serve as a therapeutic target of AML in the future. (Blood. 2013;121(19):3889-3899)

FLT3-ITD and TLR9 use Bruton tyrosine kinase to activate distinct transcriptional programs mediating AML cell survival and proliferation

“…Metabolic labeling of KG-1 and MV4-11 cells via stable isotope labeling with amino acids in cell culture (SILAC) for arginine and lysine and AML cell culture were performed as described earlier. 6 Details of the ethics approval and the protocols for lentiviral transductions, cell proliferation, and immunohistochemistry analyses are provided in the supplemental Data available on the Blood Web site.…”

“…6 Detailed information about instrument settings, bioinformatic work flows, and the QUICK method 13 are provided in the supplemental Data.…”

“…For this purpose, we transduced KG-1 and MV4-11 cells retrovirally, using IRES-EGFP vectors to express EGFP either alone, as a control, or in combination with a constitutive active form of STAT5 (caSTAT5), 6 a constitutively active variant of IKK (caIKK) as a well-known activator of NF-kB, 17 or MYC (supplemental Figure 3B-C). Subsequently, the transduced cell batches were left untreated or were treated with ibrutinib for 6 days, and the proportion of EGFP-positive cells was monitored by flow cytometry.…”

“…4 In accordance with this, pharmacologic targeting of these microenvironment-dependent pathways showed promising effects in preclinical AML models, as found, for example, for the integrin-SYK-STAT signaling axis. 5,6 In this study, we identified Bruton tyrosine kinase (BTK) as an AML target. BTK is best known for its functions in the context of B-cell receptor signaling.…”

STAT5 in hematopoietic stem cell biology and transplantation

“…83,84 Roles for integrin signaling and the spleen tyrosine kinase (Syk) in activation of STAT5 in AML blasts, including MLL-AF9 positive AML have also been reported. 85,86 Interestingly, retention of phosphorylated STAT5 in the cytoplasm has been observed in leukemias and the cytoplasmic functions for STAT5 will be important to define. STAT5 nuclear accumulation occurs predominately in Flt3-ITD + AML 87 where other mutations and pathways could provide complimentary signals.…”