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 ß-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.
Subject(s)
Leukemia, Myeloid, Acute/etiology , Osteonectin/physiology , Adolescent , Adult , Animals , Cell Line, Tumor , Cell Proliferation , Female , Gene Knockdown Techniques , Heterografts , Humans , Leukemia, Myeloid, Acute/genetics , Leukemia, Myeloid, Acute/pathology , Male , Mice , Mice, Inbred NOD , Mice, SCID , MicroRNAs/genetics , MicroRNAs/metabolism , Middle Aged , NF-kappa B/metabolism , Nucleophosmin , Osteonectin/antagonists & inhibitors , Osteonectin/genetics , Prognosis , Protein Serine-Threonine Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , Sp1 Transcription Factor/metabolism , Young Adult , beta Catenin/metabolismABSTRACT
AIMS: Maternal inflammation is a risk factor for preterm birth, and premature infants are often exposed to supplemental oxygen as a life-sustaining therapy. While more immature neonates are surviving, rates of neurodevelopmental impairment are not improving. We developed a novel mouse model with clinically relevant exposures to test the hypothesis that systemic maternal inflammation with transient neonatal hyperoxia exposure will induce a phenotype similar to diffuse periventricular leukomalacia (PVL) like that observed in premature human infants. MAIN METHODS: Timed-pregnant C3H/HeN mice received intraperitoneal injections of lipopolysaccharide (LPS) or saline on embryonic day 16. Newborn pups were placed in room air (RA) or 85% oxygen (O2) for 14 days, followed by 14 days in RA recovery. Oligodendroglial and microglial populations were evaluated at 14 and 28 days. KEY FINDINGS: Brain weight to body weight ratios were lower in mice exposed to LPS. Oligodendrocyte numbers were decreased significantly in the cerebral cortex and hippocampus in groups exposed to LPS or LPS/O2 at 14 days, and persisted in the cerebral cortex at 28 days for LPS/O2 mice. At day 14, cleaved caspase 3 was increased and numbers of microglia were elevated in the cerebral cortex and hippocampus of LPS/O2 animals. SIGNIFICANCE: These data indicate that combining systemic maternal LPS and neonatal hyperoxic exposure impairs myelination, and suggests that this novel mouse model may represent a subtle, diffuse form of periventricular white matter injury that could provide a clinically relevant platform for further study of perinatal brain injury.
