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CXCR4/YinYang1/Hsa-let-7a axis functions as tumor suppressor in acute myeloid leukemia

ABSTRACT: Surface expression of C-X-C chemokine receptor type 4 (CXCR4) in acute myeloid leukemia (AML) has been reported to be an independent prognostic factor for disease relapse and survival. We previously reported that targeting the stromal-derived factor 1α (SDF-1α)/CXCR4 axis could overcome resistance of AML cells to chemotherapy both in vitro and in vivo. To further explore the mechanism of targeting CXCR4, in the current study we focused on the regulation of microRNA. Microarray analysis revealed that the hsa-let-7a microRNA was down-regulated in OCI-AML3 cells by SDF-1α treatment and increased after CXCR4 inhibition. To further investigate the role of hsa-let-7a in leukemia biology, we overexpressed it in AML cell lines, which resulted in decreased Bcl-xL protein expression and consequently enhanced cell sensitivity to the chemotherapeutic agent cytarabine, both in vitro and in vivo. We also identified the transcription factor Yin Yang 1 (YY1) as a mediator that links the SDF-1α/CXCR4 axis with hsa-let-7a. Western blotting and immunocytochemistry demonstrated a correlation between YY1 and CXCR4 activation. ChIP assay confirmed the binding of YY1 to pri-let-7a DNA fragments. In primary AML samples (n=50), high CXCR4 surface expression was associated with low hsa-let-7a levels (r2=0.53). Improved effects of cytarabine treatment associated with greatly extended survival of human AML carrying mice was observed in primary human AML overexpressing hsa-let-7a. On the basis of these results, we propose that CXCR4 regulation of hsa-let-7a microRNA through YY1 and transcriptional silencing of the Bcl-xL protein together identifies a novel mechanism by which CXCR4 functions to induce chemoresistance in AML cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE44828 | GEO | 2013/12/01

SECONDARY ACCESSION(S): PRJNA192259

REPOSITORIES: GEO

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Project description:Surface expression of C-X-C chemokine receptor type 4 (CXCR4) in acute myeloid leukemia (AML) has been reported to be an independent prognostic factor for disease relapse and survival. We previously reported that targeting the stromal-derived factor 1M-NM-1 (SDF-1M-NM-1)/CXCR4 axis could overcome resistance of AML cells to chemotherapy both in vitro and in vivo. To further explore the mechanism of targeting CXCR4, in the current study we focused on the regulation of microRNA. Microarray analysis revealed that the hsa-let-7a microRNA was down-regulated in OCI-AML3 cells by SDF-1M-NM-1 treatment and increased after CXCR4 inhibition. To further investigate the role of hsa-let-7a in leukemia biology, we overexpressed it in AML cell lines, which resulted in decreased Bcl-xL protein expression and consequently enhanced cell sensitivity to the chemotherapeutic agent cytarabine, both in vitro and in vivo. We also identified the transcription factor Yin Yang 1 (YY1) as a mediator that links the SDF-1M-NM-1/CXCR4 axis with hsa-let-7a. Western blotting and immunocytochemistry demonstrated a correlation between YY1 and CXCR4 activation. ChIP assay confirmed the binding of YY1 to pri-let-7a DNA fragments. In primary AML samples (n=50), high CXCR4 surface expression was associated with low hsa-let-7a levels (r2=0.53). Improved effects of cytarabine treatment associated with greatly extended survival of human AML carrying mice was observed in primary human AML overexpressing hsa-let-7a. On the basis of these results, we propose that CXCR4 regulation of hsa-let-7a microRNA through YY1 and transcriptional silencing of the Bcl-xL protein together identifies a novel mechanism by which CXCR4 functions to induce chemoresistance in AML cells. MicroRNA expression profiling of OCI-AML3 cell lines treated with CXCR4 antagonist or SDF-1M-NM-1. OCI-AML3 cells were treated with 100 ng/mL SDF-1M-NM-1 or 250 nM POL6326 (a CXCR4 antagonist, Allschwil, Switzerland), total RNA was extracted at specific time points (1, 2, 4, and 8 h), and miRNA expression profiling was performed

Project description:In colorectal cancer, increased expression of the CXC chemokine receptor 4 (CXCR4) has been shown to provoke metastatic disease due to the interaction with its ligand stromal cell-derived factor 1 (SDF-1). Recently, a second SDF-1 receptor, CXCR7, was found to enhance tumor growth in solid tumors. Albeit signaling cascades via SDF-1/CXCR4 have been intensively studied, the significance of the SDF-1/CXCR7-induced intracellular communication triggering malignancy is still only marginally understood. In tumor tissue of 52 colorectal cancer (CRC) patients, we observed that expression of CXCR7 and CXCR4 increased with tumor stage, tumor size, and lymph node infiltration. Asking whether activation of CXCR4 or CXCR7 might result in a similar expression pattern, we performed microarray expression analyses using lentivirally CXCR4- and/or CXCR7-overexpressing SW480 colon cancer cell lines with and without stimulation by SDF-1α. Gene regulation via SDF-1α/CXCR4 and SDF-1α/CXCR7 was completely different and partly antidromic. Expressions of the differentially expressed genes AKR1C3, AXL, EGFR, IGFBP7, IL24, TNNC1, TRIP6 were confirmed by qPCR. Differentially regulated genes were assigned by GO to migration and lipid metabolic processes. Furthermore, using the in silico gene set enrichment analysis we showed for the first time that expressions of miR-217 and miR-218 were increased in CXCR4 and reduced in CXCR7 cells after stimulation with SDF-1α. As expected, their putative target mRNAs were inversely expressed. Functional assays exerted that exposure to SDF-1α resulted in strongly amplified invasiveness and chemosensitivity of CXCR4-expressing cells. CXCR7 overexpression led to reduced invasiveness which could only be marginally increased by SDF-1α. The CXCR4 antagonist plerixafor significantly reduced invasiveness of CXCR4-overexpressing cells only. Similarly, compared to control cells, CXCR4 cells showed increased sensitivity against 5-FU, while CXCR7 cells were more chemoresistant. These opposing results for CXCR4- or CXCR7-overexpressing colon carcinoma cells demand an unexpected attention in the clinical application of chemokine receptor antagonists like Plerixafor.

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CXCR4/YinYang1/Hsa-let-7a axis functions as tumor suppressor in acute myeloid leukemia

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