Bcr-Abl-mediated suppression of normal hematopoiesis in leukemia

CRISPR/Cas9-Directed Gene Trap Constitutes a Selection System for Corrected BCR/ABL Leukemic Cells in CML

Chronic myeloid leukaemia (CML) is a haematological neoplasm driven by the BCR/ABL fusion oncogene. The monogenic aspect of the disease and the feasibility of ex vivo therapies in haematological disorders make CML an excellent candidate for gene therapy strategies. The ability to abolish any coding sequence by CRISPR-Cas9 nucleases offers a powerful therapeutic opportunity to CML patients. However, a definitive cure can only be achieved when only CRISPR-edited cells are selected. A gene-trapping approach combined with CRISPR technology would be an ideal approach to ensure this. Here, we developed a CRISPR-Trap strategy that efficiently inserts a donor gene trap (SA-CMV-Venus) cassette into the BCR/ABL-specific fusion point in the CML K562 human cell line. The trapping cassette interrupts the oncogene coding sequence and expresses a reporter gene that enables the selection of edited cells. Quantitative mRNA expression analyses showed significantly higher level of expression of the BCR/Venus allele coupled with a drastically lower level of BCR/ABL expression in Venus+ cell fractions. Functional in vitro experiments showed cell proliferation arrest and apoptosis in selected Venus+ cells. Finally, xenograft experiments with the selected Venus+ cells showed a large reduction in tumour growth, thereby demonstrating a therapeutic benefit in vivo. This study represents proof of concept for the therapeutic potential of a CRISPR-Trap system as a novel strategy for gene elimination in haematological neoplasms.

Regulation of the Nfkbiz Gene and Its Protein Product IkBζ in Animal Models of Sepsis and Endotoxic Shock

Sepsis is a life-threatening condition that arises from a poorly regulated inflammatory response to pathogenic organisms. Current treatments are limited to antibiotics, fluid resuscitation, and other supportive therapies. New targets for monitoring disease progression and therapeutic interventions are therefore critically needed. We previously reported that lipocalin-2 (Lcn2), a bacteriostatic mediator with potent proapoptotic activities, was robustly induced in sepsis. Other studies showed that Lcn2 was a predictor of mortality in septic patients. However, how Lcn2 is regulated during sepsis is poorly understood. We evaluated how IkBζ, an inducer of Lcn2, was regulated in sepsis using both the cecal ligation and puncture (CLP) and endotoxemia (lipopolysaccharide [LPS]) animal models. We show that Nfkbiz, the gene encoding IkBζ, was rapidly stimulated but, unlike Lcn2, whose expression persists during sepsis, mRNA levels of Nfkbiz decline to near basal levels several hours after its induction. In contrast, we observed that IkBζ expression remained highly elevated in septic animals following CLP but not LPS, indicating the occurrence of a CLP-specific mechanism that extends IkBζ half-life. By using an inhibitor of IkBζ, we determined that the expression of Lcn2 was largely controlled by IkBζ. Altogether, these data indicate that the high IkBζ expression in tissues likely contributes to the elevated expression of Lcn2 in sepsis. Since IkBζ is also capable of promoting or repressing other inflammatory genes, it might exert a central role in sepsis.

Implication and role of neutrophil gelatinase-associated lipocalin in cancer: lipocalin-2 as a potential novel emerging comprehensive therapeutic target for a variety of cancer types

Cancer is a leading cause of mortalities worldwide. Over the past few decades, exploration of molecular mechanisms behind cancer initiation and progression has been of great interest in the viewpoint of both basic and clinical scientists. It is generally believed that identification of key molecules implicated in cancer pathology not only improves our understanding of the disease, but also could result in introduction of novel therapeutic strategies. Neutrophil gelatinase-associated lipocalin (NGAL)/lipocalin-2 (LCN2) is a member of lipocalin superfamily with a variety of functions. Although the main function of LCN2 is still unknown, many studies confirmed its significant role in the initiation, progression, and metastasis of various types of cancer. Furthermore, aberrant expression of LCN2 is also concerned with the chemo- and radio-resistant phenotypes of tumors. Here, we will review the contribution of known functions of LCN2 to the pathophysiology of cancer. We also highlight how the deregulated expression of LCN2 is associated with a variety of fatal types of cancer for which there are no effective therapeutic modalities. The unique and multiple functions of LCN2 and its widespread expression in different types of cancer prompted us to suggest LCN2 could be considered either as a valuable diagnostic and prognostic biomarker or as a potential novel therapeutic target.

Association of peripheral blood neutrophil gelatinase-associated lipocalin levels with bone marrow neutrophil gelatinase-associated lipocalin levels and neutrophil count in hematologic malignancy

Background

Although neutrophil gelatinase‐associated lipocalin (NGAL) is a biomarker for acute kidney injury, recently, high NGAL levels have been reported in hematologic malignancies. Given the mechanism underlying NGAL synthesis and secretion in neutrophilic series, it is speculated that NGAL levels are higher in bone marrow (BM) than in peripheral blood (PB). Additionally, PB NGAL levels are thought to be associated with neutrophilic parameters. We aimed to test both hypotheses in hematologic malignancies.

Methods

Paired BM and PB samples were collected from 41 patients undergoing BM examination for hematologic malignancies. NGAL levels were measured using immunoassays. Data on hematologic parameters were collected from medical records. Single and multiple regression analyses were performed to analyze the relationship.

Results

PB and BM NGAL (n = 41) levels were significantly different (163.0 ± 258.3 and 413.1 ± 616.2 ng/mL [mean ± standard deviation], respectively; P < 0.05). Simple regression analysis and multicollinearity assessment showed that BM NGAL levels, BM neutrophil%, and neutrophil count were significant predictors of PB NGAL. Two multiple regression models were developed (model 1, PB NGAL = 21.467* neutrophil count ‐ 0.785*BM neutrophil%; model 2, PB NGAL = 21.202*neutrophil count‐ 0.915*BM neutrophil% +0.10*BM NGAL). Akaike's information criterion and adjusted R² values showed that model 1 had higher predictive accuracy for PB NGAL. In both models, neutrophil count was the only significant predictor.

Conclusion

BM NGAL was significantly higher than PB NGAL in hematologic malignancy. In addition, PB NGAL could be expressed as a multiple regression model including neutrophil count and BM neutrophil%, being significantly influenced by neutrophil count.

LCN2 overexpression in bone enhances the hematopoietic compartment via modulation of the bone marrow microenvironment

Lipocalin-2 (LCN2) is a member of the lipocalin family whose expression is modulated in several conditions, including cell differentiation, innate immunity, stress, and cancer. Although it is known that it is expressed in bone, its function in this tissue remains poorly studied. To this end, we took advantage of transgenic mice lines that expressed LCN2 driven by a bone specific type I collagen (LCN2-Tg). In the bone marrow (BM) of LCN2-Tg mice we observed an increased number of phenotypically long-term hematopoietic stem cells (LT-HSC) that also displayed a higher proliferation rate compared to wild-type controls (Wt). Furthermore, hematopoietic progenitor cells, obtained from LCN2-Tg BM showed an increased clonogenic capacity compared to those obtained from LCN2-Tg spleen, a higher concentration of serum erythropoietin and a higher number of mature erythrocytes in the peripheral blood of old LCN2-Tg animals compared to aged-matched wt. The findings of a combined increase in the BM of the LCN2-Tg mice of SDF-1, SCF, and TIMP-1 levels along with the reduction of both MMP-9 activity and cathepsin K concentration may explain the observed effects on the HSC compartment. This study shows that LCN2 overexpression in bones modifies the BM microenvironment via modulation of the expression of key secreted factors and cytokines, which in turn regulate the HSC niche behavior enhancing both HSC homing in young mice and erythrocytes production in older mice.

From the periphery to the brain: Lipocalin-2, a friend or foe?

Lipocalin-2 (LCN2) is an acute-phase protein that, by binding to iron-loaded siderophores, acts as a potent bacteriostatic agent in the iron-depletion strategy of the immune system to control pathogens. The recent identification of a mammalian siderophore also suggests a physiological role for LCN2 in iron homeostasis, specifically in iron delivery to cells via a transferrin-independent mechanism. LCN2 participates, as well, in a variety of cellular processes, including cell proliferation, cell differentiation and apoptosis, and has been mostly found up-regulated in various tissues and under inflammatory states, being its expression regulated by several inducers. In the central nervous system less is known about the processes involving LCN2, namely by which cells it is produced/secreted, and its impact on cell proliferation and death, or in neuronal plasticity and behaviour. Importantly, LCN2 recently emerged as a potential clinical biomarker in multiple sclerosis and in ageing-related cognitive decline. Still, there are conflicting views on the role of LCN2 in pathophysiological processes, with some studies pointing to its neurodeleterious effects, while others indicate neuroprotection. Herein, these various perspectives are reviewed and a comprehensive and cohesive view of the general function of LCN2, particularly in the brain, is provided.

JAK2V617F+ myeloproliferative neoplasm clones evoke paracrine DNA damage to adjacent normal cells through secretion of lipocalin-2

JAK2V617F+ MPN clones induce paracrine DNA damage into coexisting normal clones through secretion of lipocalin-2. Lipocalin-2 suppresses normal hematopoiesis via p53 pathway activation and gives relative growth advantage to MPN clones.

Dendritic cell-secreted lipocalin2 induces CD8+ T-cell apoptosis, contributes to T-cell priming and leads to a TH1 phenotype

Lipocalin 2 (LCN2), which is highly expressed by dendritic cells (DCs) when treated with dexamethasone (Dex) and lipopolysaccharide (LPS), plays a key role in the defence against bacteria and is also involved in the autocrine apoptosis of T-cells. However, the function of LCN2 when secreted by DCs is unknown: this is a critical gap in our understanding of the regulation of innate and adaptive immune systems. Tolerance, stimulation and suppression are functions of DCs that facilitate the fine-tuning of the immune responses and which are possibly influenced by LCN2 secretion. We therefore examined the role of LCN2 in DC/T-cell interaction. WT or Lcn2^−/− bone marrow-derived DCs were stimulated with LPS or LPS+IFN-γ with and without Dex and subsequently co-cultured with T-cells from ovalbumin-specific TCR transgenic (OT-I and OT-II) mice. We found that CD8⁺ T-cell apoptosis was highly reduced when Lcn2^−/− DCs were compared with WT. An in vivo CTL assay, using LPS-treated DCs, showed diminished killing ability in mice that had received Lcn2^−/− DCs compared with WT DCs. As a consequence, we analysed T-cell proliferation and found that LCN2 participates in T-cell-priming in a dose-dependent manner and promotes a T_H1 microenvironment. DC-secreted LCN2, whose function has previously been unknown, may in fact have an important role in regulating the balance between T_H1 and T_H2. Our results yield insights into DC-secreted LCN2 activity, which could play a pivotal role in cellular immune therapy and in regulating immune responses.

Low serum lipocalin levels in patients with iron deficiency anemia

In the recent literature, there are studies on the relationship between anemia and lipocalin, but there is no study regarding the relationship between lipocalin and iron deficiency anemia (IDA) up to date. In this study, we aimed to observe lipocalin levels at admission, and after iron therapy in children with IDA. We also compared our findings to those in healthy children. Sixty-one children admitted in our outpatient clinic were included in the study. Thirty of these children had IDA (study group) and the rest were healthy (control group). Thirty patients, meeting the IDA criteria, received oral ferrous sulfate of 4 mg/kg/d. As soon as the hemoglobin value reached >11 g/dL, half dose of oral ferrous sulfate therapy was continued for another month. Serum lipocalin levels before and after iron therapies were compared. Hematologic parameters and serum lipocalin levels were also compared between the 2 groups. Mean values of serum lipocalin were 31.01±14.46 and 74.77 ng/dL in patients with IDA at admission and at third month of therapy, respectively (P<0.0001). The same figure was 57.35±39.51 ng/dL in the control group. Before treatment, mean values of lipocalin levels in patients with IDA was significantly lower than the control group (P=0.001); however, such a difference was not detected after 3 months of therapy (P=0.102). We suggest that decreased serum lipocalin levels in our patients during iron insufficiency were caused by iron deficiency rather than anemia.

Impaired neutrophil function in 24p3 null mice contributes to enhanced susceptibility to bacterial infections

Lipocalin 24p3 (24p3) is a neutrophil secondary granule protein. 24p3 is also a siderocalin, which binds several bacterial siderophores. It was therefore proposed that synthesis and secretion of 24p3 by stimulated macrophages or release of 24p3 upon neutrophil degranulation sequesters iron-laden siderophores to attenuate bacterial growth. Accordingly, 24p3-deficient mice are susceptible to bacterial pathogens for which siderophores would normally be chelated by 24p3. Specific granule deficiency (SGD) is a rare congenital disorder characterized by complete absence of proteins in secondary granules. Neutrophils from SGD patients, who are prone to bacterial infections, lack normal functions, but the potential role of 24p3 in neutrophil dysfunction in SGD is not known. In this study, we show that neutrophils from mice genetically deficient for lipocalin 24p3 (24p3(-/-)) are defective in many neutrophil functions. Specifically, neutrophils in 24p3(-/-) mice do not extravasate to sites of infection and are defective for chemotaxis. A transcriptome analysis revealed that genes that control cytoskeletal reorganization are selectively suppressed in 24p3(-/-) neutrophils. Additionally, small regulatory RNAs (microRNAs) that control upstream regulators of cytoskeletal proteins are also increased in 24p3(-/-) neutrophils. Further, 24p3(-/-) neutrophils failed to phagocytose bacteria, which may account for the enhanced sensitivity of 24p3(-/-) mice to both intracellular (Listeria monocytogenes) and extracellular (Candida albicans and Staphylococcus aureus) pathogens. Listeria does not secrete siderophores, and additionally, the siderophore secreted by Candida is not sequestered by 24p3. Therefore, the heightened sensitivity of 24p3(-/-) mice to these pathogens is not due to sequestration of siderophores limiting iron availability, but is a consequence of impaired neutrophil function.

Higher lipocalin 2 expression may represent an independent favorable prognostic factor in cytogenetically normal acute myeloid leukemia

Abstract Several molecular markers, such as NPM1, FLT3 and CEBPA, have been incorporated into both the World Health Organization and European LeukemiaNet classifications as routine assessments for the diagnosis and evaluation of prognostic significance in acute myeloid leukemia (AML). Lipocalin 2 (LCN2) is related to cancer development and is believed to be associated with the outcome of cytogenetically normal (CN)-AML. In the present study, we analyzed the prognostic effects and interactions of LCN2 expression (by molecular analysis, quantitative real-time polymerase chain reaction [qRT-PCR]) with neucleophosmin 1, fms-related tyrosine kinase 3 (FLT3) and CCAAT/enhancer-binding protein alpha mutations in 85 patients with CN-AML receiving intensive induction chemotherapy. Our results indicate that patients with higher LCN2 mRNA expression in the bone marrow (LCN2high), especially in combination with wild type FLT3-ITD, had better prognoses. FLT3-ITD compensated LCN2-overexpression-enhanced oxidative stress-induced apoptosis in cell line studies. In conclusion, LCN2high was associated with better prognosis, and FLT3 status had an adjuvant effect on overall survival.

The multifaceted roles of neutrophil gelatinase associated lipocalin (NGAL) in inflammation and cancer

Neutrophil gelatinase associated lipocalin (NGAL), also known as oncogene 24p3, uterocalin, siderocalin or lipocalin 2, is a 24kDa secreted glycoprotein originally purified from a culture of mouse kidney cells infected with simian virus 40 (SV-40). Subsequent investigations have revealed that it is a member of the lipocalin family of proteins that transport small, hydrophobic ligands. Since then, NGAL expression has been reported in several normal tissues where it serves to provide protection against bacterial infection and modulate oxidative stress. Its expression is also dysregulated in several benign and malignant diseases. Its small size, secreted nature and relative stability have led to it being investigated as a diagnostic and prognostic biomarker in numerous diseases including inflammation and cancer. Functional studies, conducted primarily on lipocalin 2 (Lcn2), the mouse homologue of human NGAL have revealed that Lcn2 has a strong affinity for iron complexed to both bacterial siderophores (iron-binding proteins) and certain human proteins like norepinephrine. By sequestering iron-laden siderophores, Lcn2 deprives bacteria of a vital nutrient and thus inhibits their growth (bacteriostatic effect). In malignant cells, its proposed functions range from inhibiting apoptosis (in thyroid cancer cells), invasion and angiogenesis (in pancreatic cancer) to increasing proliferation and metastasis (in breast and colon cancer). Ectopic expression of Lcn2 also promotes BCR-ABL induced chronic myelogenous leukemia in murine models. By transporting iron into and out of the cell, NGAL also regulates iron responsive genes. Further, it stabilizes the proteolytic enzyme matrix metalloprotease-9 (MMP-9) by forming a complex with it, and thereby prevents its autodegradation. The factors regulating NGAL expression are numerous and range from pro-inflammatory cytokines like interleukins, tumor necrosis factor-α and interferons to vitamins like retinoic acid. The purpose of this review article is to examine the expression, structure, regulation and biological role of NGAL and critically assess its potential as a novel diagnostic and prognostic marker in both benign and malignant human diseases.

Mammalian siderophores, siderophore-binding lipocalins, and the labile iron pool

Bacteria use tight-binding, ferric-specific chelators called siderophores to acquire iron from the environment and from the host during infection; animals use proteins such as transferrin and ferritin to transport and store iron. Recently, candidate compounds that could serve endogenously as mammalian siderophore equivalents have been identified and characterized through associations with siderocalin, the only mammalian siderophore-binding protein currently known. Siderocalin, an antibacterial protein, acts by sequestering iron away from infecting bacteria as siderophore complexes. Candidate endogenous siderophores include compounds that only effectively transport iron as ternary complexes with siderocalin, explaining pleiotropic activities in normal cellular processes and specific disease states.

Imatinib mesylate therapy induces reduction in neutrophil gelatinase-associated lipocalin serum levels and increase in leptin concentrations in chronic myeloid leukemia patients in molecular remission

The aim of the present study was to determine serum levels of neutrophil gelatinase-associated lipocalin (NGAL) and leptin in patients with chronic myeloid leukemia (CML) at diagnosis and after imatinib therapy when patients achieved a complete molecular remission. The study was conducted on 22 patients with CML in the chronic phase and 10 healthy subjects. The median serum NGAL levels in CML patients at diagnosis were significantly higher compared to age-matched controls. After imatinib therapy, all patients achieved complete molecular remission and NGAL levels decreased and were found significantly lower with respect to the baseline. No significant correlations were found between NGAL levels and other disease parameters. Before imatinib therapy, the median blood leptin levels were not significantly different from those of controls. After therapy with imatinib, all patients in molecular remission presented an increase in leptin levels. Future research is eagerly awaited as it may demonstrate the real role of NGAL and leptin in the onset and progression of CML.

Multiple apoptotic defects in hematopoietic cells from mice lacking lipocalin 24p3

The lipocalin mouse 24p3 has been implicated in diverse physiological processes, including apoptosis, iron trafficking, development and innate immunity. Studies from our laboratory as well as others demonstrated the proapoptotic activity of 24p3 in a variety of cultured models. However, a general role for the lipocalin 24p3 in the hematopoietic system has not been tested in vivo. To study the role of 24p3, we derived 24p3 null mice and back-crossed them onto C57BL/6 and 129/SVE backgrounds. Homozygous 24p3(-/-) mice developed a progressive accumulation of lymphoid, myeloid, and erythroid cells, which was not due to enhanced hematopoiesis because competitive repopulation and recovery from myelosuppression were the same as for wild type. Instead, apoptotic defects were unique to many mature hematopoietic cell types, including neutrophils, cytokine-dependent mast cells, thymocytes, and erythroid cells. Thymocytes isolated from 24p3 null mice also displayed resistance to apoptosis-induced by dexamethasone. Bim response to various apoptotic stimuli was attenuated in 24p3(-/-) cells, thus explaining their resistance to the ensuing cell death. The results of these studies, in conjunction with those of previous studies, reveal 24p3 as a regulator of the hematopoietic compartment with important roles in normal physiology and disease progression. Interestingly, these functions are limited to relatively mature blood cell compartments.

Relationships of lipocalin 2 with breast tumorigenesis and metastasis

Breast cancer is one of the most common cancers in women worldwide and accounts for one-sixth of cancer deaths in the United States. Breast cancer consists of a heterogeneous group of tumours classified into five types, in which the HER2/neu positive and the basal type (most are ER and HER2 negative) have the worst clinical prognosis. In recent years, prognostic/predictive markers such as ER/PR or HER2/neu have been widely used in the selection of the optimal breast cancer treatments for individual patients, which have been proven to be very effective in disease control. These results suggest that further examination of the molecular mechanisms underlying the breast tumorigenesis and identification of the potential biomarkers in different types of breast cancers will greatly benefit clinical diagnosis and facilitate the design of more effective personalized therapies to increase patient survival. This review aims to summarize recent research findings on lipocalin 2 (LCN2), a newly identified biomarker and a potential therapeutic target for breast cancer, and the possible mechanisms underlying its role in tumorigenesis and metastasis.

Upregulation of neutrophil gelatinase-associated lipocalin by ErbB2 through nuclear factor-kappaB activation

ErbB2 (HER2, neu) is a receptor tyrosine kinase overexpressed in about 25% of invasive breast carcinomas. Neutrophil gelatinase-associated lipocalin (NGAL) is a secreted glycoprotein expressed in a variety of cancers, including breast carcinomas. NGAL can inhibit erythroid cell production, leading to anemia. Anemia usually occurs in cancer patients and negatively affects quality of life. However, current treatment for cancer-related anemia has potential complications. ErbB2, NGAL, and anemia have all been associated with increased metastasis and poor prognosis in breast cancer patients, although the relationship between ErbB2 and NGAL expression is not clear. Here, using breast cancer cell lines in vitro and transgenic mice carrying the activated c-neu oncogene driven by a mouse mammary tumor virus (MMTV-neu) in vivo, we show that ErbB2 overexpression leads to NGAL upregulation, which is dependent on nuclear factor-kappaB (NF-kappaB) activity. MMTV-neu transgenic mice developed anemia after tumor onset, and anemia progression could be partially arrested by a NF-kappaB inhibitor and ErbB2-targeted therapy. Taken together, upregulation of NGAL by ErbB2 through NF-kappaB activation is involved in cancer-related anemia, and the ErbB2, NF-kappaB, and NGAL pathways may serve as potential therapeutic targets for cancer-related anemia.

Inhibition of lipocalin 2 impairs breast tumorigenesis and metastasis

Lipocalin 2 (LCN2; also known as NGAL) is a secreted glycoprotein and its elevated expression has been observed in breast cancers. However, the importance of LCN2 in breast tumorigenesis is unclear. Here, we employed a spontaneous mammary tumor mouse model showing that MMTV-ErbB2(V664E) mice lacking mouse LCN2 had significantly delayed mammary tumor formation and metastasis with reduced matrix metalloproteinase-9 activity in the blood. LCN2 expression is upregulated by HER2/phosphoinositide 3-kinase/AKT/NF-kappaB pathway. Decreasing LCN2 expression significantly reduced the invasion and migration ability of HER2(+) breast cancer cells. Furthermore, injecting an anti-mouse LCN2 antibody into mice bearing established murine breast tumors resulted in significant blockage of lung metastasis. Our findings indicate that LCN2 is a critical factor in enhancing breast tumor formation and progression possibly in part by stabilizing matrix metalloproteinase-9. Our results suggest that inhibition of LCN2 function by an inhibitory monoclonal antibody has potential for breast cancer therapy, particularly by interfering with metastasis in aggressive types of breast cancer.

Lipocalin 2: a multifaceted modulator of human cancer

Lipocalin 2 (Lcn2), a member of the lipocalin family that transports small lipophilic ligands, has gained recent attention as both a potential biomarker and a modulator of human cancers. Here we describe recent findings of the functions of Lcn2 in breast cancer and the potential mechanisms that underlie its actions. Lcn2 has been shown to induce the epithelial to mesenchymal transition (EMT) in breast cancer cells and to promote breast tumor invasion. Estrogen receptor alpha may participate in the pathway that leads to Lcn2-induced EMT. Preliminary evidence also suggests that Lcn2 may be useful as a potential non-invasive urinary biomarker of breast cancer. Elevated levels of Lcn2 have also been reported in other human cancers. The potential roles of Lcn2 in epithelial tumors as well as leukemia are also reviewed and discussed here.

NGAL decreases E-cadherin-mediated cell-cell adhesion and increases cell motility and invasion through Rac1 in colon carcinoma cells

Expression of neutrophil gelatinase-associated lipocalin (NGAL)/lipocalin2, a recently recognized iron regulatory protein that binds to matrix metalloproteinase-9 (MMP9), is increased in a spectrum of cancers, including those of the colorectum. Using colon carcinoma cell lines stably transfected with NGAL or antisense NGAL, we showed that NGAL overexpression altered subcellular localization of E-cadherin and catenins, decreased E-cadherin-mediated cell-cell adhesion, enhanced cell-matrix attachment, and increased cell motility and in vitro invasion. Conversely, a decrease in NGAL enhanced more aggregated growth pattern and decreased in vitro invasion. We further showed that NGAL exerted these effects through the alteration of the subcellular localization of Rac1 in an extracellular matrix-dependent, but MMP9-independent, manner. Furthermore, we observed that the NGAL-overexpressing cells tolerated increased iron levels in the culture environment, whereas the NGAL-underexpressing cells showed significant cell death after prolonged incubation in high-iron condition. Thus, overexpressing NGAL in colon carcinomas is an important regulatory molecule that integrates extracellular environment cues, iron metabolism, and intracellular small GTPase signaling in cancer migration and invasion. NGAL may therefore be a new target for therapeutic intervention in colorectal carcinoma.

Transcription and signalling pathways involved in BCR-ABL-mediated misregulation of 24p3 and 24p3R

Lipocalin 24p3 is a secreted protein that can induce apoptosis in cells containing the 24p3 cell surface receptor, 24p3R. The oncoprotein BCR-ABL activates 24p3 and represses 24p3R expression. Thus, BCR-ABL(+) cells synthesise and secrete 24p3, which induces apoptosis in normal 24p3R-containing cells but not in BCR-ABL(+) cells. The cell signalling and transcription factor pathways by which BCR-ABL misregulates expression of 24p3 and 24p3R remain to be elucidated. Here we show that BCR-ABL upregulates 24p3 expression through activation of the JAK/STAT pathway, which culminates in binding of Stat5 to the 24p3 promoter. We find that 24p3R expression is regulated by Runx transcription factors, and that BCR-ABL induces a switch in binding from Runx3, an activator of 24p3R expression, to Runx1, a repressor of 24p3R expression, through a Ras signalling pathway. Finally, we show that repression of 24p3R by BCR-ABL is a critical feature of the mechanism by which imatinib kills BCR-ABL(+) cells. Our results reveal diverse signalling/transcription pathways that regulate 24p3 and 24p3R expression in response to BCR-ABL and are directly relevant to the treatment of BCR-ABL(+) disease.

Identification of 24p3 as a direct target of Foxo3a regulated by interleukin-3 through the phosphoinositide 3-kinase/Akt pathway

Pro-apoptotic protein 24p3, a member of lipocalin family, is induced upon interleukin-3 (IL-3) deprivation and plays a pivotal role in induction of apoptosis in hematopoietic cells. However, the molecular mechanism by which IL-3 regulates 24p3 expression remains largely unknown. Here, we show that 24p3 is a direct target of Foxo3a and that phosphoinositide 3-kinase (PI3K)/Akt mediates IL-3-repressed 24p3 through regulation of Foxo3a. Inhibition of the PI3K/Akt (but not MAPK) pathway induced 24p3 expression and programmed cell death in FL5.12 cells. Furthermore, constitutively active Akt largely attenuated 24p3 expression and apoptosis in response to IL-3 withdrawal. Foxo3a directly bound to the 24p3 promoter and induced promoter activity. Akt abrogated wild-type Foxo3a-induced (but not Akt-non-phosphorylatable Foxo3a3A-induced) 24p3 expression and promoter activity. Therefore, these data indicate for the first time that 24p3 is a Foxo3a target gene and that PI3K/Akt (but not MAPK) mediates IL-3-regulated 24p3 expression in hematopoietic cells.

Neutrophil gelatinase-associated lipocalin expression in chronic myeloid leukemia

The murine equivalent of neutrophil gelatinase-associated lipocalin (NGAL) was previously found to be increased by BCR-ABL expression in murine models of chronic myeloid leukemia (CML). Our study evaluates, in CML patients at various clinical stages, the levels of NGAL mRNA in blood samples and protein in sera. A highly significant increase of mRNA expression and protein secretion was shown in patients at diagnosis. The parallel expression of NGAL and BCR-ABL at the early stage of CML process allows us to suggest that NGAL could play an important role in the physiopathology of CML.

Requirement of lipocalin 2 for chronic myeloid leukemia

The Bcr-Abl oncoprotein causes chronic myeloid leukemia by a mechanism involving its activated tyrosine kinase. BCR-ABL+ mouse hematopoietic cells persistently express and secrete lipocalin 2 by a mechanism that requires the tyrosine kinase of the Bcr-Abl oncoprotein. Our new findings indicate that lipocalin 2 is required for leukemia induction, as prevention of expression of lipocalin 2 by BCR-ABL+ mouse marrow cells totally blocks leukemia induction in a mouse model.

Lipocalin 2 is required for BCR-ABL-induced tumorigenesis

Our previous studies indicate that reduction of lipocalin 2 (mouse 24p3) expression by either anti-sense or siRNA approaches strongly reduces the overgrowth of BCR-ABL+ mouse myeloid 32D in marrow and spleen of NOD/SCID mice. In this study, we used the mouse bone marrow transplant model to further explore the role of 24p3 in BCR-ABL-induced leukemia. Consistent with our previous findings, when using non-irradiated mice as recipient, donor marrow cells expressing BCR-ABL but lacking 24p3 did not cause leukemia or any disease after 75 days, whereas all mice receiving wild type BCR-ABL donor cells died with CML-like disease. An agar clone of the BCR-ABL+ human CML cell line K562 (C5) that secretes relatively high levels of lipocalin 2 (human NGAL) induced suppression of hematopoiesis in spleen and marrow of mice, leading to early death in contrast to parental K562 or K562 clone (C6) expressing low amounts of NGAL. Compared with K562 cells, overexpressing NGAL in K562 led to a higher apoptosis rate and an atrophy phenotype in the spleen of the inoculated mice. Plasma from both leukemic mice and CML patients showed elevated lipocalin 2 levels compared with healthy individuals. Moreover, we found that a primary stable cell line from wild-type mouse marrow cells expressing BCR-ABL caused solid tumors in nude mice whereas a similar BCR-ABL+ cell line from 24p3 null mice did not. These findings demonstrate that lipocalin 2 has at least two functions related to tumorigenesis, one involving apoptosis induction of normal hematopoietic cells and the other being tissue invasion by leukemia cells.

The hematopoietic stem cell compartment of JAK2V617F-positive myeloproliferative disorders is a reflection of disease heterogeneity

The JAK2V617F somatic point mutation has been described in patients with myeloproliferative disorders (MPDs). Despite this progress, it remains unknown how a single JAK2 mutation causes 3 different MPD phenotypes, polycythemia vera (PV), essential thrombocythemia, and primitive myelofibrosis (PMF). Using an in vivo xenotransplantation assay in nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice, we tested whether disease heterogeneity was associated with quantitative or qualitative differences in the hematopoietic stem cell (HSC) compartment. We show that the HSC compartment of PV and PMF patients contains JAK2V617F-positive long-term, multipotent, and self-renewing cells. However, the proportion of JAK2V617F and JAK2 wild-type SCID repopulating cells was dramatically different in these diseases, without major modifications of the self-renewal and proliferation capacities for JAK2V617F SCID repopulating cells. These experiments provide new insights into the pathogenesis of JAK2V617F MPD and demonstrate that a JAK2 inhibitor needs to target the HSC compartment for optimal disease control in classical MPD.

Emerging stem cell concepts for imatinib-resistant chronic myeloid leukaemia: implications for the biology, management, and therapy of the disease

Chronic myeloid leukaemia (CML) is a myeloid neoplasm defined by the BCR/ABL oncoprotein that is considered essential for leukaemogenesis and accumulation of neoplastic cells. The BCR/ABL kinase inhibitor imatinib is an effective agent in most patients and can now be regarded as front-line therapy. Hence, intrinsic and acquired resistance to imatinib has been described and is an emerging challenge in clinical practice. While CML stem cells display primary resistance, stem cell subclones may, in addition, acquire imatinib-resistant mutants of BCR/ABL. Other factors that are considered to contribute to stem cell resistance include the genetic background, clonal evolution, additional biological features of subclones, gene amplifications, silencing of tumour suppressor genes and specific pharmacological aspects. In this article, mechanisms of resistance of CML (stem) cells against imatinib and other BCR/ABL inhibitors are discussed, together with strategies to overcome and/or to prevent resistance with available drugs or novel anti-leukaemic approaches.

Iron metabolism at the host pathogen interface: lipocalin 2 and the pathogen-associated iroA gene cluster

The host innate immune defense protein lipocalin 2 binds bacterial enterobactin siderophores to limit bacterial iron acquisition. To counteract this host defense mechanism bacteria have acquired the iroA gene cluster, which encodes enzymatic machinery and transporters that revitalize enterobactin in the form of salmochelin. The iroB enzyme introduces glucosyl residues at the C5 site on 2,3-dihydroxybenzoylserine moieties of enterobactin and thereby prevents lipocalin 2 binding. Additional strategies to evade lipocalin 2 have evolved in other bacteria, such as Mycobacteria tuberculosis and Bacillus anthracis. Targeting these specialized bacterial evasion strategy may provide a mechanism to reinvigorate lipocalin 2 in defense against specific pathogens.

Lipocalin-2 regulates the inflammatory response during ischemia and reperfusion of the transplanted heart

Ischemia and reperfusion (IR) are known to negatively affect early allograft function following solid organ transplantation. Lipocalin-2 (Lcn-2) has been described as a marker and potential positive modulator of acute inflammation during these processes. Using a heterotopic murine heart transplant model we previously found that IR resulted in a pronounced upregulation of Lcn-2 mRNA in the heart at 12 (22.7-fold increase) and 24 h (9.8-fold increase) of reperfusion. We now confirm this increase at the protein level and provide evidence for infiltrating polymorphonuclear cells as the primary source of Lcn-2 protein. Lcn-2 levels are increased 6.6-fold at 12 h, 11.4-fold at 24 h and 6.4 fold at 48 h after reperfusion. In Lcn-2(-/-) grafts the number of infiltrating granulocytes is reduced by 54% (p < 0.05) at 2 h, 79% (p < 0.01) at 12 h, 72% (p < 0.01) at 24 h and 52% (p < 0.01) at 48 h after reperfusion compared to Lcn-2(+/+) grafts, without any differences in cardiomyocyte apoptosis. These data suggest a function of Lcn-2 in the initiation of the inflammatory response. Moreover, an increase in Lcn-2 is not only restricted to the transplanted heart, but is also observed in the kidney, hinting at a possible involvement of Lcn-2 in the systemic response to IR.

Molecular cytogenetic characterization of the 11q13 amplicon in head and neck squamous cell carcinoma

Amplification of 11q13 DNA sequences and overexpression of CCND1 are common findings in head and neck squamous cell carcinoma (HNSCC), identified in about 30% of the cases. However, little is known about initiation of the amplification and the organization of the amplicon. In order to study the structure of the amplicon in more detail and to learn more about the mechanisms involved in its initiation, prometaphase, metaphase, and anaphase fluorescence in situ hybridization (FISH) with 40 BAC clones spanning a 16-Mb region in chromosome bands 11q12.2 to 11q13.5 was performed in nine HNSCC cell lines with homogeneously staining regions. FISH analysis showed that the size of the amplicon varied among the nine cell lines, the smallest being 2.12 Mb and the largest 8.97 Mb. The smallest overlapping region of amplification was approximately 1.61 Mb, covering the region from BAC 729E14 to BAC 102B19. This region contained several genes previously shown to be amplified and overexpressed in HNSCC, including CCDN1, CTTN, SHANK2, and ORAOV1. The cell lines were also used to study the internal structure of the amplicon. Various patterns of amplified DNA sequences within the amplicon were found among the nine cell lines. Even within the same cell line, different amplicon structures could be found in different cell populations, indicating that the mechanisms involved in the development of the amplicons in HNSCC were more complex than previously assumed. The frequent finding of inverted repeats within the amplicons, however, suggests that breakage-fusion-bridge cycles are important in the initiation, but the fact that such repeats constituted only small parts of the amplicons indicate that they are further rearranged during tumor progression.

A Cell-Surface Receptor for Lipocalin 24p3 Selectively Mediates Apoptosis and Iron Uptake

The lipocalin mouse 24p3 has been implicated in diverse physiological processes, including apoptosis due to interleukin-3 (IL-3) deprivation and iron transport. Here we report cloning of the 24p3 cell-surface receptor (24p3R). Ectopic 24p3R expression confers on cells the ability to undergo either iron uptake or apoptosis, dependent upon the iron content of the ligand: Iron-loaded 24p3 increases intracellular iron concentration without promoting apoptosis; iron-lacking 24p3 decreases intracellular iron levels, which induces expression of the proapoptotic protein Bim, resulting in apoptosis. Intracellular iron delivery blocks Bim induction and suppresses apoptosis due to 24p3 addition or IL-3 deprivation. We find, unexpectedly, that the BCR-ABL oncoprotein activates expression of 24p3 and represses 24p3R expression, rendering BCR-ABL(+) cells refractory to secreted 24p3. By inhibiting BCR-ABL, imatinib induces 24p3R expression and, consequently, apoptosis. Our results reveal an unanticipated role for intracellular iron regulation in an apoptotic pathway relevant to BCR-ABL-induced myeloproliferative disease and its treatment.

Impaired DNA replication within progenitor cell pools promotes leukemogenesis

Impaired cell cycle progression can be paradoxically associated with increased rates of malignancies. Using retroviral transduction of bone marrow progenitors followed by transplantation into mice, we demonstrate that inhibition of hematopoietic progenitor cell proliferation impairs competition, promoting the expansion of progenitors that acquire oncogenic mutations which restore cell cycle progression. Conditions that impair DNA replication dramatically enhance the proliferative advantage provided by the expression of Bcr-Abl or mutant p53, which provide no apparent competitive advantage under conditions of healthy replication. Furthermore, for the Bcr-Abl oncogene the competitive advantage in contexts of impaired DNA replication dramatically increases leukemogenesis. Impaired replication within hematopoietic progenitor cell pools can select for oncogenic events and thereby promote leukemia, demonstrating the importance of replicative competence in the prevention of tumorigenesis. The demonstration that replication-impaired, poorly competitive progenitor cell pools can promote tumorigenesis provides a new rationale for links between tumorigenesis and common human conditions of impaired DNA replication such as dietary folate deficiency, chemotherapeutics targeting dNTP synthesis, and polymorphisms in genes important for DNA metabolism.

Expression of SIP24 in the peripartum and postpartum rat uterus

SIP24 is, a 24 kDa superinducible protein, is an acute phase protein that is expressed in several tissues and organs and is identified in the human, mouse, and rat genome as lipocalin 2 (lcn2). This study investigated SIP24 expression by the rat uterus just before delivery and during postpartum involution. The distribution and levels of expression of SIP24 and myeloperoxidase (MPO) were compared by Western blot analysis and immunocytochemistry. The SIP24 level was high on day 22 of pregnancy and on days 1 and 2 postpartum, decreased on day 3 postpartum, and declined to low levels similar to those in nonpregnant rats by day 5 postpartum. SIP24 positive cells were identified by immunohistochemistry in the luminal and glandular epithelium on day 22 of pregnancy and on days 1, 2, 3, and 5 postpartum in addition to nonpregnant rats. Immunostaining was intense on day 22 of pregnancy and on days 1 and 2 postpartum. MPO also was identified in uterine tissues by immunohistochemistry. An evaluation of the SIP24 and MPO distribution and levels of expression in the rat uterus is consistent with the hypothesis that SIP24 modulates the neutrophil population by activities such as inducing their apoptosis.