SPARC promotes leukemic cell growth and predicts acute myeloid leukemia outcome
Houda Alachkar, Ramasamy Santhanam, Kati Maharry, Klaus H. Metzeler, Xiaomeng Huang, Jessica Kohlschmidt, Jason H. Mendler, Juliana M. Benito, Christopher Hickey, Paolo Neviani, Adrienne M. Dorrance, Mirela Anghelina, Jihane Khalife, Somayeh S. Tarighat, Stefano Volinia, Susan P. Whitman, Peter Paschka, Pia Hoellerbauer, Yue-Zhong Wu, Lina Han, Brad N. Bolon, William Blum, Krzysztof Mrózek, Andrew J. Carroll, Danilo Perrotti, Michael Andreeff, Michael A. Caligiuri, Marina Konopleva, Ramiro Garzon, Clara D. Bloomfield, Guido Marcucci
Houda Alachkar, Ramasamy Santhanam, Kati Maharry, Klaus H. Metzeler, Xiaomeng Huang, Jessica Kohlschmidt, Jason H. Mendler, Juliana M. Benito, Christopher Hickey, Paolo Neviani, Adrienne M. Dorrance, Mirela Anghelina, Jihane Khalife, Somayeh S. Tarighat, Stefano Volinia, Susan P. Whitman, Peter Paschka, Pia Hoellerbauer, Yue-Zhong Wu, Lina Han, Brad N. Bolon, William Blum, Krzysztof Mrózek, Andrew J. Carroll, Danilo Perrotti, Michael Andreeff, Michael A. Caligiuri, Marina Konopleva, Ramiro Garzon, Clara D. Bloomfield, Guido Marcucci
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Research Article Oncology

SPARC promotes leukemic cell growth and predicts acute myeloid leukemia outcome

Abstract

Aberrant expression of the secreted protein, acidic, cysteine-rich (osteonectin) (SPARC) gene, which encodes a matricellular protein that participates in normal tissue remodeling, is associated with a variety of diseases including cancer, but the contribution of SPARC to malignant growth remains controversial. We previously reported that SPARC was among the most upregulated genes in cytogenetically normal acute myeloid leukemia (CN-AML) patients with gene-expression profiles predictive of unfavorable outcome, such as mutations in isocitrate dehydrogenase 2 (IDH2-R172) and overexpression of the oncogenes brain and acute leukemia, cytoplasmic (BAALC) and v-ets erythroblastosis virus E26 oncogene homolog (ERG). In contrast, SPARC was downregulated in CN-AML patients harboring mutations in nucleophosmin (NPM1) that are associated with favorable prognosis. Based on these observations, we hypothesized that SPARC expression is clinically relevant in AML. Here, we found that SPARC overexpression is associated with adverse outcome in CN-AML patients and promotes aggressive leukemia growth in murine models of AML. In leukemia cells, SPARC expression was mediated by the SP1/NF-κB transactivation complex. Furthermore, secreted SPARC activated the integrin-linked kinase/AKT (ILK/AKT) pathway, likely via integrin interaction, and subsequent β-catenin signaling, which is involved in leukemia cell self-renewal. Pharmacologic inhibition of the SP1/NF-κB complex resulted in SPARC downregulation and leukemia growth inhibition. Together, our data indicate that evaluation of SPARC expression has prognosticative value and SPARC is a potential therapeutic target for AML.

Authors

Houda Alachkar, Ramasamy Santhanam, Kati Maharry, Klaus H. Metzeler, Xiaomeng Huang, Jessica Kohlschmidt, Jason H. Mendler, Juliana M. Benito, Christopher Hickey, Paolo Neviani, Adrienne M. Dorrance, Mirela Anghelina, Jihane Khalife, Somayeh S. Tarighat, Stefano Volinia, Susan P. Whitman, Peter Paschka, Pia Hoellerbauer, Yue-Zhong Wu, Lina Han, Brad N. Bolon, William Blum, Krzysztof Mrózek, Andrew J. Carroll, Danilo Perrotti, Michael Andreeff, Michael A. Caligiuri, Marina Konopleva, Ramiro Garzon, Clara D. Bloomfield, Guido Marcucci

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Figure 8

Targeting SPARC expression in AML.

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Targeting SPARC expression in AML. (A) SPARC 3′ UTR–luciferase activity ...
(A) SPARC 3′ UTR–luciferase activity in the presence of miR-29b was measured by cotransfecting 293T cells with SPARC–3′ UTR reporter and a synthetic microRNA; values were normalized to those of cells transfected with scramble. (B) Ectopic expression of synthetic miR-29b significantly decreases SPARC mRNA expression in Kasumi-1 cells. (C) SPARC protein in AML blast samples (patients 6 and 10) at 24 hours following transfection with miR-29b. (D) miR-29b levels, (E) mRNA levels of SPARC and SP1, and (F) Western blot analysis showing SPARC, SP1, and MYC protein levels, measured in Kasumi-1 cells treated with 20, 60, and 100 nM of bortezomib. (G) SPARC mRNA and (H) protein levels in blasts from 3 primary AML samples (patients 6, 10, and 7) treated with 100 nM bortezomib and assessed 24 hours later.