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CXCL12/CXCR4 signaling mediates niche occupancy and tumor maintenance in T-cell leukemia

ABSTRACT: T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy characterized by infiltration of the bone marrow and other sites with transformed T cell progenitors. The role of tissue microenvironments in the pathogenesis of T-ALL or any other type of acute leukemia is little understood. In delineating interactions between T-ALL cells and their environment, we initially found that T-ALL cells express high surface levels of the chemokine receptor CXCR4. Intravital imaging of an intact tibia revealed T-ALL cells in direct contact with bone marrow stromal cells producing the CXCR4 ligand, CXCL12. Genetic targeting of CXCR4 on T-ALL cells resulted in a marked reduction of leukemia burden and prolonged disease remission, and disruption of the CXCL12/CXCR4 axis using small molecule inhibitors prevented T-ALL progression in a primary xenograft model. Finally, we were able to show that CXCR4 inhibition significantly decreased expression of Myc and its target genes. Myc expression is a key regulator of T-ALL leukemia initiating cell (LIC) activity, suggesting that CXCR4 inhibition can suppress LIC activity by silencing the Myc response in T-ALL cells. Our data suggest that targeting of CXCL12/CXCR4 signaling could be a powerful new tool for combating T-ALL, a disease with no current targeted therapies.

ORGANISM(S): Mus musculus

PROVIDER: GSE60367 | GEO | 2015/08/12

SECONDARY ACCESSION(S): PRJNA258103

REPOSITORIES: GEO

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Project description:T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy characterized by infiltration of the bone marrow and other sites with transformed T cell progenitors. The role of tissue microenvironments in the pathogenesis of T-ALL or any other type of acute leukemia is little understood. In delineating interactions between T-ALL cells and their environment, we initially found that T-ALL cells express high surface levels of the chemokine receptor CXCR4. Intravital imaging of an intact tibia revealed T-ALL cells in direct contact with bone marrow stromal cells producing the CXCR4 ligand, CXCL12. Genetic targeting of CXCR4 on T-ALL cells resulted in a marked reduction of leukemia burden and prolonged disease remission, and disruption of the CXCL12/CXCR4 axis using small molecule inhibitors prevented T-ALL progression in a primary xenograft model. Finally, we were able to show that CXCR4 inhibition significantly decreased expression of Myc and its target genes. Myc expression is a key regulator of T-ALL leukemia initiating cell (LIC) activity, suggesting that CXCR4 inhibition can suppress LIC activity by silencing the Myc response in T-ALL cells. Our data suggest that targeting of CXCL12/CXCR4 signaling could be a powerful new tool for combating T-ALL, a disease with no current targeted therapies. Mouse T-ALL cells were treated ex vivo with Cxcr4 inhibitor AMD3100 or vehicle control. Additionally, mouse T-ALL primary tumors were isolated from control (Cxcr4+/+) or knockout (Cxcr4-/-) animals. Total RNA was extracted from samples using the RNeasy Plus Mini Kit (Qiagen). Samples were then subject to PolyA selection using oligo-dT beads (Life Technologies, Carlsbad, CA) according to the manufacturer's instructions. The resulting RNA samples were then used as input for library construction using the dUTP method as described by Parkhomchuck et al., 2009. RNA libraries were then sequenced on the Illumina HiSeq 2500 using 50bp single-end reads.

Project description:Nathaniel L. Coggins, Danielle Trakimas, S. Laura Chang, Anna Ehrlich, Paramita Ray, Kathryn E. Luker, Jennifer J. Linderman & Gary D. Luker. CXCR7 controls competition for recruitment of β-arrestin 2 in cells expressing both CXCR4 and CXCR7. PLoS ONE 9, 6 (2014). Chemokine CXCL12 promotes growth and metastasis of more than 20 different human cancers, as well as pathogenesis of other common diseases. CXCL12 binds two different receptors, CXCR4 and CXCR7, both of which recruit and signal through the cytosolic adapter protein β-arrestin 2. Differences in CXCL12-dependent recruitment of β-arrestin 2 in cells expressing one or both receptors remain poorly defined. To quantitatively investigate parameters controlling association of β-arrestin 2 with CXCR4 or CXCR7 in cells co-expressing both receptors, we used a systems biology approach combining real-time, multi-spectral luciferase complementation imaging with computational modeling. Cells expressing only CXCR4 maintain low basal association with β-arrestin 2, and CXCL12 induces a rapid, transient increase in this interaction. In contrast, cells expressing only CXCR7 have higher basal association with β-arrestin 2 and exhibit more gradual, prolonged recruitment of β-arrestin 2 in response to CXCL12. We developed and fit a data-driven computational model for association of either CXCR4 or CXCR7 with β-arrestin 2 in cells expressing only one type of receptor. We then experimentally validated model predictions that co-expression of CXCR4 and CXCR7 on the same cell substantially decreases both the magnitude and duration of CXCL12-regulated recruitment of β-arrestin 2 to CXCR4. Co-expression of both receptors on the same cell only minimally alters recruitment of β-arrestin 2 to CXCR7. In silico experiments also identified β-arrestin 2 as a limiting factor in cells expressing both receptors, establishing that CXCR7 wins the "competition" with CXCR4 for CXCL12 and recruitment of β-arrestin 2. These results reveal how competition for β-arrestin 2 controls integrated responses to CXCL12 in cells expressing both CXCR4 and CXCR7. These results advance understanding of normal and pathologic functions of CXCL12, which is critical for developing effective strategies to target these pathways therapeutically.

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CXCL12/CXCR4 signaling mediates niche occupancy and tumor maintenance in T-cell leukemia

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