Common deleted genes in the 5q- syndrome: thrombocytopenia and reduced erythroid colony formation in SPARC null mice

ABIN1 (Q478) is Required to Prevent Hematopoietic Deficiencies through Regulating Type I IFNs Expression

A20-binding inhibitor of NF-κB activation (ABIN1) is a polyubiquitin-binding protein that regulates cell death and immune responses. Although Abin1 is located on chromosome 5q in the region commonly deleted in patients with 5q minus syndrome, the most distinct of the myelodysplastic syndromes (MDSs), the precise role of ABIN1 in MDSs remains unknown. In this study, mice with a mutation disrupting the polyubiquitin-binding site (Abin1Q478H/Q478H ) is generated. These mice develop MDS-like diseases characterized by anemia, thrombocytopenia, and megakaryocyte dysplasia. Extramedullary hematopoiesis and bone marrow failure are also observed in Abin1Q478H/Q478H mice. Although Abin1Q478H/Q478H cells are sensitive to RIPK1 kinase-RIPK3-MLKL-dependent necroptosis, only anemia and splenomegaly are alleviated by RIPK3 deficiency but not by MLKL deficiency or the RIPK1 kinase-dead mutation. This indicates that the necroptosis-independent function of RIPK3 is critical for anemia development in Abin1Q478H/Q478H mice. Notably, Abin1Q478H/Q478H mice exhibit higher levels of type I interferon (IFN-I) expression in bone marrow cells compared towild-type mice. Consistently, blocking type I IFN signaling through the co-deletion of Ifnar1 greatly ameliorated anemia, thrombocytopenia, and splenomegaly in Abin1Q478H/Q478H mice. Together, these results demonstrates that ABIN1(Q478) prevents the development of hematopoietic deficiencies by regulating type I IFN expression.

Dynamic changes in the levels of sCD62L and SPARC in chronic myeloid leukaemia patients during imatinib treatment

WHAT IS KNOWN AND OBJECTIVE

Chronic myeloid leukaemia (CML) microenvironment is responsible for resistance of leukaemic cells to tyrosine kinase inhibitor, altered adhesion, increased proliferation and leukaemic cells growth and survival through the secretion of many soluble molecules. We aimed at monitoring soluble L-selectin (sCD62L) and secreted protein acidic and rich in cysteine (SPARC) levels in chronic phase chronic myeloid leukaemia (CP-CML) patients and assessing the impact of imatinib on these parameters.

METHODS

This prospective controlled clinical trial enrolled 35 subjects classified into two groups: control group included 10 healthy volunteers and CP-CML patients group included 25 newly diagnosed CP-CML patients received imatinib 400 mg once daily. sCD62L plasma levels, SPARC serum levels, breakpoint cluster region-Abelson1 (BCR-ABL1) %, complete blood count with differential, liver and kidney functions parameters were assessed at baseline and after 3 and 6 months of treatment.

RESULTS AND DISCUSSION

At baseline, sCD62L and SPARC were significantly elevated in CP-CML patients (p < 0.05) compared to control group. After 3 months of treatment, sCD62L was non-significantly decreased (p > 0.05), while surprisingly SPARC was significantly increased (p < 0.05) compared to baseline. Moreover, after 6 months of treatment, sCD62L was significantly decreased (p < 0.05) and SPARC was non-significantly decreased (p > 0.05) compared to baseline. In addition, sCD62L was significantly correlated with WBCs and neutrophils counts, while SPARC was significantly correlated with lymphocytes count at baseline and after 3 and 6 months of imatinib treatment.

WHAT IS NEW AND CONCLUSION

The elevated levels of sCD62L and SPARC at diagnosis in CP-CML patients could reflect their roles in CML pathogenesis and the dynamic changes in their levels during imatinib therapy might suppose additional mechanisms of action of imatinib beside inhibition of BCR-ABL. Furthermore, imatinib showed a significant impact on sCD62L and SPARC levels during treatment period.

Insights into the Hematopoietic Regulatory Activities of Osteoblast by Secretomics

Osteoblasts are a key component of the endosteal hematopoietic stem cell (HSC) niche and are recognized with strong hematopoietic supporting activity. Similarly, mesenchymal stromal cells (MSC)-derived osteoblast (M-OST) conditioned media (OCM) enhances the growth of hematopoietic progenitors in culture and modulate their engraftment activity. We aimed to characterize the hematopoietic supporting activity of OCM by comparing the secretome of M-OST to that of their precursor. Over 300 proteins were quantified by mass spectroscopy in media conditioned with MSC or M-OST, with 47 being differentially expressed. Included were growth factors, extracellular matrix (ECM) proteins and proteins from the complement pathways. The functional contribution of selected proteins on the growth and differentiation of cord blood (CB) progenitors was tested. Secreted Protein Acidic and Rich in Cysteine (SPARC) and Galectin 3 (Gal3) had little impact on the growth of CB cells in serum-free medium (SFM). In contrast, inhibition of the complement 3 A receptor (C3a-R) present on CB progenitors significantly reduced the growth of CD34+ cells in OCM cultures but not in SFM. These results provide new insights into changes in factors released by MSC undergoing osteoblast differentiation, and on paracrine factors that are partially responsible for the hematopoietic supporting activity of osteoblasts. This article is protected by copyright. All rights reserved.

Therapy-related myeloid neoplasms: when genetics and environment collide

Therapy-related myeloid neoplasms (t-MN) arise as a late effect of chemotherapy and/or radiation administered for a primary condition, typically a malignant disease, solid organ transplant or autoimmune disease. Survival is measured in months, not years, making t-MN one of the most aggressive and lethal cancers. In this Review, we discuss recent developments that reframe our understanding of the genetic and environmental aetiology of t-MN. Emerging data are illuminating who is at highest risk of developing t-MN, why t-MN are chemoresistant and how we may use this information to treat and ultimately prevent this lethal disease.

Transcriptome meta-analysis reveals a dysregulation in extra cellular matrix and cell junction associated gene signatures during Dengue virus infection

Dengue Viruses (DENVs) cause one of the most prevalent arthropod-borne viral diseases affecting millions of people worldwide. Identification of genes involved in DENV pathogenesis would help in deciphering molecular mechanisms responsible for the disease progression. Here, we carried out a meta-analysis of publicly available gene expression data of dengue patients and further validated the meta-profile using in-vitro infection in THP-1 cells. Our findings reveal that DENV infection modulates expression of several genes and signalling pathways including interferons, detoxification of ROS and viral assembly. Interestingly, we have identified novel gene signatures comprising of INADL/PATJ and CRTAP (Cartilage Associated Protein), which were significantly down-regulated across all patient data sets as well as in DENV infected THP-1 cells. PATJ and CRTAP genes are involved in maintaining cell junction integrity and collagen assembly (extracellular matrix component) respectively, which together play a crucial role in cell-cell adhesion. Our results categorically reveal that overexpression of CRTAP and PATJ genes restrict DENV infection, thereby suggesting a critical role of these genes in DENV pathogenesis. Conclusively, these findings emphasize the utility of meta-analysis approach in identifying novel gene signatures that might provide mechanistic insights into disease pathogenesis and possibly lead towards the development of better therapeutic interventions.

Original Research: A case-control genome-wide association study identifies genetic modifiers of fetal hemoglobin in sickle cell disease

Sickle cell disease (SCD) is a group of inherited blood disorders that have in common a mutation in the sixth codon of the β-globin (HBB) gene on chromosome 11. However, people with the same genetic mutation display a wide range of clinical phenotypes. Fetal hemoglobin (HbF) expression is an important genetic modifier of SCD complications leading to milder symptoms and improved long-term survival. Therefore, we performed a genome-wide association study (GWAS) using a case-control experimental design in 244 African Americans with SCD to discover genetic factors associated with HbF expression. The case group consisted of subjects with HbF≥8.6% (133 samples) and control group subjects with HbF≤£3.1% (111 samples). Our GWAS results replicated SNPs previously identified in an erythroid-specific enhancer region located in the second intron of the BCL11A gene associated with HbF expression. In addition, we identified SNPs in the SPARC, GJC1, EFTUD2 and JAZF1 genes as novel candidates associated with HbF levels. To gain insights into mechanisms of globin gene regulation in the HBB locus, linkage disequilibrium (LD) and haplotype analyses were conducted. We observed strong LD in the low HbF group in contrast to a loss of LD and greater number of haplotypes in the high HbF group. A search of known HBB locus regulatory elements identified SNPs 5' of δ-globin located in an HbF silencing region. In particular, SNP rs4910736 created a binding site for a known transcription repressor GFi1 which is a candidate protein for further investigation. Another HbF-associated SNP, rs2855122 in the cAMP response element upstream of Gγ-globin, was analyzed for functional relevance. Studies performed with siRNA-mediated CREB binding protein (CBP) knockdown in primary erythroid cells demonstrated γ-globin activation and HbF induction, supporting a repressor role for CBP. This study identifies possible molecular determinants of HbF production.

Insights into myelodysplastic syndromes from current preclinical models

In recent years, there has been significant progress made in our understanding of the molecular genetics of myelodysplastic syndromes (MDS). Using massively parallel sequencing techniques, recurring mutations are identified in up to 80% of MDS cases, including many with a normal karyotype. The differential role of some of these mutations in the initiation and progression of MDS is starting to be elucidated. Engineering candidate genes in mice to model MDS has contributed to recent insights into this complex disease. In this review, we examine currently available mouse models, with detailed discussion of selected models. Finally, we highlight some advances made in our understanding of MDS biology, and conclude with discussions of questions that remain unanswered.

Clinical utility of lenalidomide in the treatment of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a heterogeneous group of acquired clonal hematopoietic disorders characterized by peripheral blood cytopenias, paradoxical BM hypercellularity, ineffective hematopoiesis, and increased risk of leukemic transformation. Risk stratification, using different prognostic scores and markers, is at the core of MDS management. Deletion 5q [del(5q)] MDS is a distinct class of MDS characterized by the haploinsufficiency of specific genes, microRNAs, and proteins, which has been linked to increased sensitivity to the drug lenalidomide. Phase II and III clinical trials have demonstrated the efficacy of lenalidomide in improving clinical outcomes of patients with del(5q) MDS, including reduction in red blood cell transfusion requirements and improvements in quality of life. Lenalidomide has also demonstrated some activity in non-del(5q) lower-risk MDS as well as higher-risk MDS, especially in combination with other agents. In this paper, we review the pathogenesis of del(5q) MDS, the proposed mechanisms of action of lenalidomide, the major clinical trials that documented the activity of lenalidomide in different MDS populations, potential predictors of benefit from the drug and suggested mechanisms of resistance, and the use of combination strategies to expand the clinical utility of lenalidomide in MDS.

Loss of SPARC protects hematopoietic stem cells from chemotherapy toxicity by accelerating their return to quiescence

Around birth, hematopoietic stem cells (HSCs) expanding in the fetal liver migrate to the developing bone marrow (BM) to mature and expand. To identify the molecular processes associated with HSCs located in the 2 different microenvironments, we compared the expression profiles of HSCs present in the liver and BM of perinatal mice. This revealed the higher expression of a cluster of extracellular matrix-related genes in BM HSCs, with secreted protein acidic and rich in cysteine (SPARC) being one of the most significant ones. This extracellular matrix protein has been described to be involved in tissue development, repair, and remodeling, as well as metastasis formation. Here we demonstrate that SPARC-deficient mice display higher resistance to serial treatment with the chemotherapeutic agent 5-fluorouracil (5-FU). Using straight and reverse chimeras, we further show that this protective effect is not due to a role of SPARC in HSCs, but rather is due to its function in the BM niche. Although the kinetics of recovery of the hematopoietic system is normal, HSCs in a SPARC-deficient niche show an accelerated return to quiescence, protecting them from the lethal effects of serial 5-FU treatment. This may become clinically relevant, as SPARC inhibition and its protective effect on HSCs could be used to optimize chemotherapy schemes.

SPARC promotes leukemic cell growth and predicts acute myeloid leukemia outcome

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.

Lenalidomide as a disease-modifying agent in patients with del(5q) myelodysplastic syndromes: linking mechanism of action to clinical outcomes

Deletion of the long arm of chromosome 5, del(5q), is the most prevalent cytogenetic abnormality in patients with myelodysplastic syndromes (MDS). In isolation, it is traditionally associated with favorable prognosis compared with other subtypes of MDS. However, owing to the inherent heterogeneity of the disease, prognosis for patients with del(5q) MDS is highly variable depending on the presence of factors such as additional chromosomal abnormalities, >5 % blasts in the bone marrow (BM), or transfusion dependence. Over recent years, the immunomodulatory drug lenalidomide has demonstrated remarkable efficacy in patients with del(5q) MDS. Advances in the understanding of the pathogenesis of the disease have suggested that lenalidomide targets aberrant signaling pathways caused by haplosufficiency of specific genes in a commonly deleted region on chromosome 5 (e.g., SPARC, RPS14, Cdc25C, and PP2A). As a result, the agent specifically targets del(5q) clones while also promoting erythropoiesis and repopulation of the bone marrow in normal cells. This review discusses recent developments in the understanding of the mechanism of action of lenalidomide, and how this underlies favorable outcomes in patients with del(5q) MDS. In addition, we discuss how improved understanding of the mechanism of disease will facilitate clinicians’ ability to predict/monitor response and identify patients at risk of relapse.

Global methylation analysis identifies prognostically important epigenetically inactivated tumor suppressor genes in multiple myeloma

Outcome in multiple myeloma is highly variable and a better understanding of the factors that influence disease biology is essential to understand and predict behavior in individual patients. In the present study, we analyzed combined genomewide DNA methylation and gene expression data of patients treated in the Medical Research Council Myeloma IX trial. We used these data to identify epigenetically repressed tumor suppressor genes with prognostic relevance in myeloma. We identified 195 genes with changes in methylation status that were significantly associated with prognosis. Combining DNA methylation and gene expression data led to the identification of the epigenetically regulated tumor modulating genes GPX3, RBP1, SPARC, and TGFBI. Hypermethylation of these genes was associated with significantly shorter overall survival, independent of age, International Staging System score, and adverse cytogenetics. The 4 differentially methylated and expressed genes are known to mediate important tumor suppressive functions including response to chemotherapy (TGFBI), interaction with the microenvironment (SPARC), retinoic acid signaling (RBP1), and the response to oxidative stress (GPX3), which could explain the prognostic impact of their differential methylation. Assessment of the DNA methylation status of the identified genes could contribute to the molecular characterization of myeloma, which is prerequisite for an individualized treatment approach.

MicroRNA-584 and the protein phosphatase and actin regulator 1 (PHACTR1), a new signaling route through which transforming growth factor-β Mediates the migration and actin dynamics of breast cancer cells

TGF-β plays an important role in breast cancer progression as a prometastatic factor, notably through enhancement of cell migration. It is becoming clear that microRNAs, a new class of small regulatory molecules, also play crucial roles in mediating tumor formation and progression. We found TGF-β to down-regulate the expression of the microRNA miR-584 in breast cancer cells. Furthermore, we identified PHACTR1, an actin-binding protein, to be positively regulated by TGF-β in a miR-584-dependent manner. Moreover, we found TGF-β-mediated down-regulation of miR-584 and increased expression of PHACTR1 to be required for TGF-β-induced cell migration of breast cancer cells. Indeed, both overexpression of miR-584 and knockdown of PHACTR1 resulted in a drastic reorganization of the actin cytoskeleton and reduced TGF-β-induced cell migration. Our data highlight a novel signaling route whereby TGF-β silences the expression of miR-584, resulting in enhanced PHACTR1 expression, and further leading to actin rearrangement and breast cancer cell migration.

Chromosome 5q deletion is extremely rare in patients with myelofibrosis

Chromosome 5q deletion can be found in rare cases of myelofibrosis (MF) but the incidence, clinical significance and response to therapies are not well studied. We retrospectively reviewed charts of 939 patients with MF and identified 8 patients [0.8%] who carried 5q deletion. Of the 8, seven had complex cytogenetic abnormalities and one had additional clone with different cytogenetic abnormality. All 8 had significant three-lineage pancytopenia. Three patients took lenalidomide and one (patient with 5q-clone) achieved long-lasting hematologic response. Two patients responded to JAK2 inhibitor therapy. MF patients with 5q deletion often have complex karyotype and poor outcome.

Stromal SPARC contributes to the detrimental fibrotic changes associated with myeloproliferation whereas its deficiency favors myeloid cell expansion

In myeloid malignancies, the neoplastic clone outgrows normal hematopoietic cells toward BM failure. This event is also sustained by detrimental stromal changes, such as BM fibrosis and osteosclerosis, whose occurrence is harbinger of a dismal prognosis. We show that the matricellular protein SPARC contributes to the BM stromal response to myeloproliferation. The degree of SPARC expression in BM stromal elements, including CD146+ mesenchymal stromal cells, correlates with the degree of stromal changes, and the severity of BM failure characterizing the prototypical myeloproliferative neoplasm primary myelofibrosis. Using Sparc−/− mice and BM chimeras, we demonstrate that SPARC contributes to the development of significant stromal fibrosis in a model of thrombopoietin-induced myelofibrosis. We found that SPARC deficiency in the radioresistant BM stroma compartment impairs myelofibrosis but, at the same time, associates with an enhanced reactive myeloproliferative response to thrombopoietin. The link betwen SPARC stromal deficiency and enhanced myeloid cell expansion under a myeloproliferative spur is also supported by the myeloproliferative phenotype resulting from the transplantation of defective Apcmin mutant hematopoietic cells into Sparc−/− but not WT recipient BM stroma. Our results highlight a complex influence of SPARC over the stromal and hematopoietic BM response in myeloproliferative conditions.

Engineering mouse models with myelodysplastic syndrome human candidate genes; how relevant are they?

Myelodysplastic syndromes represent particularly challenging hematologic malignancies that arise from a large spectrum of genetic events resulting in a disease characterized by a range of different presentations and outcomes. Despite efforts to classify and identify the key genetic events, little improvement has been made in therapies that will increase patient survival. Animal models represent powerful tools to model and study human diseases and are useful pre-clinical platforms. In addition to enforced expression of candidate oncogenes, gene inactivation has allowed the consequences of the genetic effects of human myelodysplastic syndrome to be studied in mice. This review aims to examine the animal models expressing myelodysplastic syndrome-associated genes that are currently available and to highlight the most appropriate model to phenocopy myelodysplastic syndrome disease and its risk of transformation to acute myelogenous leukemia.

Lenalidomide promotes p53 degradation by inhibiting MDM2 auto-ubiquitination in myelodysplastic syndrome with chromosome 5q deletion

Allelic deletion of the RPS14 gene is a key effector of the hypoplastic anemia in patients with myelodysplastic syndrome (MDS) and chromosome 5q deletion (del(5q)). Disruption of ribosome integrity liberates free ribosomal proteins to bind to and trigger degradation of mouse double minute 2 protein (MDM2), with consequent p53 transactivation. Herein we show that p53 is overexpressed in erythroid precursors of primary bone marrow del(5q) MDS specimens accompanied by reduced cellular MDM2. More importantly, we show that lenalidomide (Len) acts to stabilize MDM2, thereby accelerating p53 degradation. Biochemical and molecular analyses showed that Len inhibits the haplodeficient protein phosphatase 2A catalytic domain alpha (PP2Acα) phosphatase resulting in hyperphosphorylation of inhibitory serine-166 and serine-186 residues on MDM2, and displaces binding of RPS14 to suppress MDM2 autoubiquitination whereas PP2Acα overexpression promotes drug resistance. Bone marrow specimens from del(5q) MDS patients resistant to Len overexpressed PP2Acα accompanied by restored accumulation of p53 in erythroid precursors. Our findings indicate that Len restores MDM2 functionality in the 5q- syndrome to overcome p53 activation in response to nucleolar stress, and therefore may warrant investigation in other disorders of ribosomal biogenesis.

Important genes in the pathogenesis of 5q- syndrome and their connection with ribosomal stress and the innate immune system pathway

Myelodysplastic syndrome (MDS) with interstitial deletion of a segment of the long arm of chromosome 5q [del(5q)] is characterized by bone marrow erythroid hyperplasia, atypical megakaryocytes, thrombocythemia, refractory anemia, and low risk of progression to acute myeloid leukemia (AML) compared with other types of MDS. The long arm of chromosome 5 contains two distinct commonly deleted regions (CDRs). The more distal CDR lies in 5q33.1 and contains 40 protein-coding genes and genes coding microRNAs (miR-143, miR-145). In 5q-syndrome one allele is deleted that accounts for haploinsufficiency of these genes. The mechanism of erythroid failure appears to involve the decreased expression of the ribosomal protein S14 (RPS14) gene and the upregulation of the p53 pathway by ribosomal stress. Friend leukemia virus integration 1 (Fli1) is one of the target genes of miR145. Increased Fli1 expression enables effective megakaryopoiesis in 5q-syndrome.

Morphologic analysis in myelodysplastic syndromes with del(5q) treated with lenalidomide. A Japanese multiinstitutional study

Lenalidomide is known to be effective in myelodysplastic syndromes (MDS) with del(5q) in improving anemia and suppressing del(5q) cells. MDS with del(5q) shows increase of nonlobulated megakaryocytes. However, histopathology of MDS with del(5q) treated with lenalidomide has not been fully studied. We investigated the morphologic changes in lenalidomide treated low- or intermediate-1-risk MDS with del(5q). All of evaluable patients showed high proportion of nonlobulated megakaryocytes. The nonlobulated megakaryocytes were markedly decreased in 6 patients during therapy in parallel with suppression of del(5q) cells. Our analysis suggests that single allele deletion of common deleted region inhibits nuclear lobulation of megakaryocytes.

Molecular dissection of the 5q deletion in myelodysplastic syndrome

The 5q-syndrome is a subtype of myelodysplastic syndrome (MDS) with a defined clinical phenotype associated with heterozygous deletions of chromosome 5q. While no genes have been identified that undergo recurrent homozygous inactivation, functional studies have revealed individual genes that contribute to the clinical phenotype of MDS through haplo-insufficient gene expression. Heterozygous loss of the RPS14 gene on 5q leads to activation of p53 in the erythroid lineage and the macrocytic anemia characteristic of the 5q-syndrome. The megakaryocytic and platelet phenotype of the 5q-syndrome has been attributed to heterozygous deletion of miR145 and miR146a. Murine models have implicated heterozygous loss of APC, EGR1, DIAPH1, and NPM1 in the pathophysiology of del(5q) MDS. These findings indicate that the phenotype of MDS patients with deletions of chromosome 5q is due to haplo-insufficiency of multiple genes.

The impact of the ovarian microenvironment on the anti-tumor effect of SPARC on ovarian cancer

A lack of host-derived SPARC promotes disease progression in an intraperitoneal (IP) ID8 mouse model of epithelial ovarian cancer (EOC). Since orthotopic injection (OT) of ID8 cells better recapitulates high-grade serous cancer, we examined the impact of host-derived SPARC following OT injection. Sparc(-/-) and wild-type (WT) mice were injected with ID8 cells either OT or IP and tumors were analyzed at the moribund stage. Sparc(-/-) mice had reduced survival and fewer well-defined abdominal lesions compared with WT controls after IP injection, whereas no differences were observed in survival or abdominal lesions between Sparc(-/-) and WT mice after OT injection. No differences in mass or collagen content were observed in ovarian tumors between OT-injected Sparc(-/-) and WT mice. The abdominal wall of the IP-injected Sparc(-/-) mice exhibited immature and less abundant collagen fibrils compared with WT mice both in injected and non-injected controls. In contrast to human EOC, SPARC was expressed by the tumor cells but was absent in reactive stroma of WT mice. Exposure to the ovarian microenvironment through OT injections alters the metastatic behaviour of ID8 cells, which is not affected by the absence of host-derived SPARC.

Biology and treatment of the 5q- syndrome

The 5q- syndrome is a unique subtype of myelodysplastic syndromes typified by a relatively indolent course and responsiveness to lenalidomide. Here, we review the salient biologic features of this disease. Hemizygous deletion of a segment of chromosome 5q is believed to be the disease-initiating event. Recent molecular techniques have isolated the common deleted region and characterized key candidate genes contributing to the disease phenotype. Gene-specific RNA interference strategies revealed that haplo-insufficiency for the RPS14 gene, which encodes a ribosomal protein, is a critical effector of the p53-dependent erythroid hypoplasia and apoptotic loss of erythroid precursors. Disease-specific sensitivity to lenalidomide results from the drug's inhibitory effect on two haplodeficient phosphatases, PP2Acα and CDC25c, which are coregulators of the G(2)/M checkpoint. Hyperphosphorylation of MDM2, as a result of inhibition of PP2A phosphatase activity, stabilizes MDM2, permitting p53 degradation and transition to G(2) arrest and clonal suppression. With the emerging data elucidating the pathogenesis of the 5q- syndrome and the success of clinical trials, a cohesive story connecting the biology and pharmacology associated with this subtype of myelodysplastic syndromes has emerged.

Isolated del(5q) in myeloid malignancies: clinicopathologic and molecular features in 143 consecutive patients

World Health Organization (WHO) criteria were used to identify 143 consecutive patients (median age 73 years; 90 females) with myeloid neoplasms and isolated del(5q) seen between 1989 and 2009. We have previously reported on 88 (61%) of these patients who met criteria for WHO defined "myelodysplastic syndromes (MDS) with isolated del(5q)." The remaining 55 patients were classified as having "other" MDS variants (n = 29; 20%), acute myeloid leukemia (AML; n = 14; 10%), or myeloproliferative neoplasms (MPN; n = 12; 8%). DNA was available in 138 patients and mutation screening revealed 20 cases with JAK2, 6 with IDH, and 3 with MPL mutations; JAK2 and MPL mutations were seen mostly in MPN or "MDS with isolated del(5q)" whereas IDH mutations were frequent in other MDS variants. Overall median survival for the 143 patient cohort was 35 months and leukemic transformation (LT) was documented in 19 (~13%) cases. "MDS with isolated del(5q)" had the best prognosis with median survival of 66 months and LT rate of ~6%. Survival was poor among the other myeloid neoplasm subgroups regardless of specific morphologic diagnosis. Multivariable analysis identified higher leukocyte count and percentage of bone marrow and circulating blasts as independent predictors of shortened survival. The first two parameters and the presence of IDH mutations predicted inferior leukemia-free survival. The current study validates the prognostic relevance of considering "MDS with isolated del(5q)" as a separate WHO subcategory and identifies leukocytosis, higher blast count, and IDH mutations as being prognostically detrimental, in myeloid neoplasms associated with isolated del(5q).

Mouse models of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are hematopoietic malignancies characterized by peripheral cytopenias in the face of normo- or hypercellular, dysplastic bone marrow that arise from mutations in the hematopoietic stem/progenitor cell (HSPC). The disease is characterized by multiple cytogenetic and molecular defects, which result in an extremely heterogeneous phenotype. Recently, significant efforts have been made to develop appropriate mouse models to study this complex disease. Because of the heterogeneity of MDS, no single model is able to capture the MDS phenotype in its entirety. In this review, we describe several MDS mouse models and discuss the advances made in our understanding of the different disease mechanisms within the malignant clone and the marrow microenvironment. In addition, we describe progress in xenotransplantation models of MDS and discuss questions that remain to be answered.

High-level CD34 expression on megakaryocytes independently predicts an adverse outcome in patients with myelodysplastic syndromes

Expression of CD34 on mature-appearing megakaryocytes can be seen in various intrinsic bone marrow (BM) disorders as well as reactive bone marrows. In this study we investigate the clinical significance of CD34+ megakaryocytes in myelodysplastic syndromes (MDSs). Expression of CD34 on megakaryocytes was assessed on BM biopsies obtained from 202 patients with MDS. High-level (≥20%) CD34 expression on megakaryocytes was found in BM of 29 patients (14%). The expression of CD34 on megakaryocytes is correlated with severe cytopenia, higher numbers of myeloblasts, more frequent and higher risk cytogenetic abnormalities, and a shorter overall survival. Multivariate analysis indicated that the expression of CD34 on megakaryocytes could be a strong and an independent poor prognostic factor in MDS, with a hazard ratio of 2.53.

Distinctive microRNA expression profiles in CD34+ bone marrow cells from patients with myelodysplastic syndrome

MicroRNAs (miRNAs) are small non-coding RNAs functioning as regulators of hematopoiesis. Their differential expression patterns have been linked with various pathological processes originating from hematopoietic stem cells (HSCs). However, limited information is available regarding the role of miRNAs in myelodysplastic syndrome (MDS). Using miRNA arrays, we measured expression of 1,145 miRNAs in CD34+ bone marrow cells obtained from 39 MDS and acute myeloid leukemia (AML) evolved from MDS patients, and compared them with those of six healthy donors. Differential miRNA expression was analyzed and a panel of upregulated (n=13) and downregulated (n=9) miRNAs were found (P<0.001) in MDS/AML patients. An increased expression of a large miRNA cluster mapped within the 14q32 locus was detected. Differences in miRNA expression of MDS subtypes showed a distinction between early and advanced MDS; an apparent dissimilarity was observed between RAEB-1 and RAEB-2 subtypes. In early MDS, we monitored upregulation of proapoptotic miR-34a, which may contribute to the increased apoptosis of HSCs. Patients with 5q deletion were characterized by decreased levels of miR-143(*) and miR-378 mapped within the commonly deleted region at 5q32. This is an early report describing differential expression in MDS CD34+ cells, likely reflecting their disease-specific regulation.

Advances in the 5q- syndrome

The 5q- syndrome is the most distinct of all the myelodysplastic syndromes with a clear genotype/phenotype relationship. The significant progress made during recent years has been based on the determination of the commonly deleted region and the demonstration of haploinsufficiency for the ribosomal gene RPS14. The functional screening of all the genes in the commonly deleted region determined that RPS14 haploinsufficiency is the probable cause of the erythroid defect in the 5q- syndrome. A mouse model of the human 5q- syndrome has now been created by chromosomal engineering involving a large-scale deletion of the Cd74-Nid67 interval (containing RPS14). A variety of lines of evidence support the model of ribosomal deficiency causing p53 activation and defective erythropoiesis, including most notably the crossing of the "5q- mice" with p53-deficient mice, thereby ameliorating the erythroid progenitor defect. Emerging evidence supports the notion that the p53 activation observed in the mouse model may also apply to the human 5q- syndrome. Other mouse modeling data suggest that haploinsufficiency of the microRNA genes miR-145 and miR-146a may contribute to the thrombocytosis seen in the 5q- syndrome. Lenalidomide has become an established therapy for the 5q- syndrome, although its precise mode of action remains uncertain.

Innate immune signaling in the myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are heterogeneous clonal hematologic malignancies characterized by cytopenias caused by ineffective hematopoiesis and propensity to progress to acute myeloid leukemia. Innate immunity provides immediate protection against pathogens by coordinating activation of signaling pathways in immune cells. Given the prominent role of the innate immune pathway in regulating hematopoiesis, it is not surprising that aberrant signaling of this pathway is associated with hematologic malignancies. Increased activation of the innate immune pathway may contribute to dysregulated hematopoiesis, dysplasia, and clonal expansion in myelodysplastic syndromes.

Molecular mechanisms involved in the progression of myelodysplastic syndrome

Myelodysplastic syndromes (MDS) are a heterogeneous group of diseases characterized by ineffective hematopoiesis presenting with peripheral cytopenias in combination with a hyperplastic bone marrow. MDS patients have an increased risk of disease evolution to acute leukemia. Strong efforts have been made to gain further insights into the pathobiology of MDS. Development and progression of MDS to acute myeloid leukemia is suggested to be a multistep alteration to hematopoietic stem cells consisting of class I and class II alterations: the former targeting genes that are involved in signal transduction (e.g., FLT3, RAS and KIT), whereas the latter affect transcription factors (e.g., RUNX, RARA, EVI1 and WT1). These alterations consist of not only genomic mutations but also epigenetic aberrations, which can lead to reversible gene silencing. However, whether numerical and structural alterations of chromosomes and/or single genes or epigenetic changes represent the initiating event or, more likely, secondary events remains part of the discussion. Accumulation of such defects may finally cause the leukemic transformation of MDS.

Chromosomal deletions in AML

Several, acquired, non-random chromosomal deletions have been characterized in acute myelogenous leukemia (AML). While the deletion limits vary among patients, there are consistent regions of overlap among the deleted segments between patients. Furthermore, chromosomal deletions are achieved frequently by unbalanced translocations between two and more chromosomes resulting loss of candidate leukemia suppressor loci from the affected chromosomes. Most deletions occurring as sole anomalies are associated with good-intermediate clinical outcome, but complex cytogenetic anomalies signify an aggressive clinical course. Thanks to the exciting development in microarray, siRNA technologies, a number of candidate AML suppressor genes localizing to the critical regions of overlap within the deletions have been identified recently. Most of the candidate genes do not function by the classical "two hits," namely loss of an allele unmasking inactivating mutations in the remaining allele. Gene dosage, epigenetic silencing, and uniparental disomy appear to be common mechanisms of gene inactivation in AML. While several of the newly discovered candidate genes lead to new pathways, a few of them affect previously known leukemogenic targets. Thus the investments made over the years on leukemia suppressor gene discovery are beginning to yield reasonable results at the present time. Future beholds promise for targeted therapy of these poorly characterized AMLs, as we uncover the mutations driving their clonal evolution.

A p53-dependent mechanism underlies macrocytic anemia in a mouse model of human 5q- syndrome

The identification of the genes associated with chromosomal translocation breakpoints has fundamentally changed our understanding of the molecular basis of hematological malignancies. By contrast, the study of chromosomal deletions has been hampered by the large number of genes deleted and the complexity of their analysis. We report the generation of a mouse model for the human 5q⁻ syndrome using large-scale chromosomal engineering. Haploinsufficiency of the Cd74 – Nid67 interval (containing the Ribosomal protein S14 gene – Rps14) causes macrocytic anemia, prominent erythroid dysplasia and monolobulated megakaryocytes in the bone marrow. This is associated with defective bone marrow progenitor development, increased apoptosis and the appearance of bone marrow cells expressing high levels of p53. Notably, intercrossing with p53-deficient mice, completely rescues the progenitor cell defect, restoring CMP/MEP, GMP and HSC bone marrow populations. This novel mouse model suggests that a p53-dependent mechanism underlies the pathophysiology of the 5q⁻ syndrome.

A critical role for phosphatase haplodeficiency in the selective suppression of deletion 5q MDS by lenalidomide

Lenalidomide is the first karyotype-selective therapeutic approved for the treatment of myelodysplastic syndromes (MDS) owing to high rates of erythroid and cytogenetic response in patients with chromosome 5q deletion [del(5q)]. Although haploinsufficiency for the RPS14 gene and others encoded within the common deleted region (CDR) have been implicated in the pathogenesis of the del(5q) phenotype, the molecular basis of the karyotype specificity of lenalidomide remains unexplained. We focused our analysis on possible haplodeficient enzymatic targets encoded within the CDR that play key roles in cell-cycle regulation. We show that the dual specificity phosphatases, Cdc25C and PP2Acalpha, which are coregulators of the G(2)-M checkpoint, are inhibited by lenalidomide. Gene expression was lower in MDS and acute myeloid leukemia (AML) specimens with del(5q) compared with those with alternate karyotypes. Lenalidomide inhibited phosphatase activity either directly (Cdc25C) or indirectly (PP2A) with corresponding retention of inhibitory phospho-tyrosine residues. Treatment of del(5q) AML cells with lenalidomide induced G(2) arrest and apoptosis, whereas there was no effect in nondel(5q) AML cells. Small interfering RNA (shRNA) suppression of Cdc25C and PP2Acalpha gene expression recapitulated del(5q) susceptibility to lenalidomide with induction of G(2) arrest and apoptosis in both U937 and primary nondel(5q) MDS cells. These data establish a role for allelic haplodeficiency of the lenalidomide inhibitable Cdc25C and PP2Acalpha phosphatases in the selective drug sensitivity of del(5q) MDS.

Diagnostic challenges in the myelodysplastic syndromes: the current and future role of genetic and immunophenotypic studies

Myelodysplastic syndromes (MDS) comprise a clinically and pathologically diverse collection of hematopoietic neoplasms, most commonly presenting with peripheral cytopenias typically in the context of bone marrow hypercellularity. Mechanistically, at least in the early phases of the disease, this apparently paradoxical picture is primarily due to ineffective hematopoiesis, which is accompanied by a variety of morphologic abnormalities in hematopoietic cells. The identification of recurrent, clinically relevant cytogenetic defects in MDS has spurred the research of molecular mechanisms that contribute to its inception as well as to the development of heterogeneous subtypes. Although conventional cytogenetic analyses remain a diagnostic mainstay in MDS, the application of contemporary techniques including molecular cytogenetics, microarray technologies and multiparametric flow cytometry may ultimately reveal new diagnostic parameters that are theoretically more objective and sensitive than current morphologic approaches. This review aims to outline the role of genetic and immunophenotypic studies in the evaluation of MDS, including findings that may potentially influence future diagnostic classifications, which could refine prognostication and ultimately facilitate the growth of targeted therapies.

Deletion 5q in myelodysplastic syndrome: a paradigm for the study of hemizygous deletions in cancer

Hemizygous deletions are common molecular abnormalities in cancer. In some cases, these deletions highlight chromosomal loci containing tumor suppressor genes that undergo homozygous inactivation. In other cases, hemizygous deletions cause disease by allelic insufficiency for one or more genes. As the intact allele has no identifiable lesions, functional approaches are critical for the identification of pathogenic genes within large deletions. Hemizygous, interstitial deletion of chromosome 5q is the most common cytogenetic abnormality in myelodysplastic syndrome (MDS) and has been the focus of functional analysis. Some patients with this molecular lesion have the 5q- syndrome, a disorder with a highly consistent clinical phenotype. A systematic RNA interference screen to interrogate the function of each gene in the common deleted region (CDR) for the 5q- syndrome identified RPS14 as a critical haploinsufficiency disease gene for the erythroid failure, which is a characteristic of this syndrome. Genes located in an adjacent deleted region have also been implicated in MDS. The full clinical phenotype is likely caused by the integration of effects from allelic insufficiency for multiple genes. With the identification and characterization of these genes, the 5q deletion is becoming a model for understanding hemizygous chromosomal deletions in cancer.

Myelodysplastic syndromes: biology and treatment

Optimal management of patients with myelodysplastic syndromes (MDS) requires an insight into the biology of the disease and the mechanisms of action of the available therapies. This review focuses on low-risk MDS, for which chronic anaemia and eventual progression to acute myeloid leukaemia are the main concerns. We cover the updated World Health Organization classification, the latest prognostic scoring system, and describe novel findings in the pathogenesis of 5q- syndrome. We perform in depth analyses of two of the most widely used treatments, erythropoietin and lenalidomide, discussing mechanisms of action, reasons for treatment failure and influence on survival.

Van-den Berghe's 5q- syndrome in 2008

Van Den Berghe established 5q- syndrome as a discrete clinical entity in 1974 when he described patients with macrocytic anaemia, thrombocytosis, dyserythropoiesis, hypolobulated megakaryocytes and an interstitial deletion within chromosome 5q. With del(5q) as the sole cytogenetic abnormality, 5q- syndrome represents an opportunity to define precisely the molecular defect(s) underlying the pathogenesis of this disease. The commonly deleted region in 5q- syndrome, which is distinct from that in patients with complex cytogenetic changes that include del(5q), includes the ribosomal protein S14 locus and it has been proposed that that loss of an RPS14 allele accounts for the 5q- syndrome phenotype. However, this hypothesis fails to explain the growth advantage of the 5q- syndrome clone and it is evident that ribosomal protein defects are not specific to 5q- syndrome, as they are found in other bone marrow failure syndromes. Lenalidomide therapy leads to normalization of both haematological and cytogenetic parameters in the majority of 5q- syndrome patients. This review examines the potential role of several genes, including RPS14, in the pathogenesis of the 5q- syndrome and recent advances in clinical management, with particular emphasis on the role and mechanism of action of lenalidomide.

IFATS collection: Combinatorial peptides identify alpha5beta1 integrin as a receptor for the matricellular protein SPARC on adipose stromal cells

The biological features of adipose stromal (stem) cells (ASC), which serve as progenitors for differentiated cells of white adipose tissue (WAT), are still largely undefined. In an initiative to identify functional ASC surface receptors, we screened a combinatorial library for peptide ligands binding to patient-derived ASC. We demonstrate that both primary and cultured human and mouse stromal cells express a conserved receptor targeted by peptides found to mimic SPARC, a matricellular protein that is required for normal WAT development. A signaling receptor for SPARC has not as yet been determined. By using the SPARC-mimicking peptides CMLAGWIPC (termed hPep) and CWLGEWLGC (termed mPep), isolated by panning on human and mouse cells, respectively, we identified the alpha5beta1 integrin complex as a candidate receptor for SPARC. On the basis of these results, we evaluated ASC responses to SPARC or SPARC-mimicking peptide exposure. Our results suggest that extracellular SPARC binds to alpha5beta1 integrin at sites of focal adhesions, an interaction disrupting firm attachment of ASC to extracellular matrix. We propose that SPARC-mediated mobilization of ASC through its effect on alpha5beta1 integrin complex provides a functional basis for the regulation of WAT body composition by SPARC. We also show that alpha5beta1 integrin is a potential target for ASC-selective intracellular delivery of bioactive peptides and gene therapy vectors directed by the SPARC-mimicking peptides. Disclosure of potential conflicts of interest is found at the end of this article.