Disruption of Annexin II /p11 Interaction Suppresses Leukemia Cell Binding, Homing and Engraftment, and Sensitizes the Leukemia Cells to Chemotherapy

Characterizations of annexin A1-interacting proteins in apical membrane and cytosolic compartments of renal tubular epithelial cells

Annexin A1 (ANXA1) is a multifunctional calcium-binding protein that can bind to membrane phospholipids. Under high-calcium condition, ANXA1 expression increases on renal epithelial cell surface, leading to enhanced adhesion of calcium oxalate (CaOx) crystal (stone material) onto the cells. To regulate various cellular processes, ANXA1 interacts with many other intracellular protein partners. However, components of the ANXA1-interacting protein complex remain unclear. Herein, we characterized the interacting complexes of apical membrane (ApANXA1) and cytosolic (cyANXA1) forms of ANXA1 in apical membrane and cytosolic compartments, respectively, of renal epithelial cells under high-calcium condition using proteomic and bioinformatic approaches. After fractionation, the ApANXA1- and CyANXA1-interacting partners were identified by immunoprecipitation followed by nanoLC‑ESI‑Qq-TOF tandem mass spectrometry (IP-MS/MS). The ANXA1-interacting partners that were common in both apical membrane and cytosolic compartments and those unique in each compartment were then analyzed for their physico-chemical properties (molecular weight, isoelectric point, amino acid contents, instability index, aliphatic index, and grand average of hydropathicity), secondary structure (α-helix, β-turn, random coil, and extended strand), molecular functions, biological processes, reactome pathways and KEGG pathways. The data demonstrated that each set of these interacting proteins exhibited common and unique characteristics and properties. The knowledge from this study may lead to better understanding of the ApANXA1 and CyAXNA1 biochemistry and functions as well as the pathophysiology of CaOx kidney stone formation induced by high-calcium condition.

Açaí (Euterpe oleracea Mart.) Seed Oil Exerts a Cytotoxic Role over Colorectal Cancer Cells: Insights of Annexin A2 Regulation and Molecular Modeling

Açaí, Euterpe oleracea Mart., is a native plant from the Amazonian and is rich in several phytochemicals with anti-tumor activities. The aim was to analyze the effects of açaí seed oil on colorectal adenocarcinoma (ADC) cells. In vitro analyses were performed on CACO-2, HCT-116, and HT-29 cell lines. The strains were treated with açaí seed oil for 24, 48, and 72 h, and cell viability, death, and morphology were analyzed. Molecular docking was performed to evaluate the interaction between the major compounds in açaí seed oil and Annexin A2. The viability assay showed the cytotoxic effect of the oil in colorectal adenocarcinoma cells. Acai seed oil induced increased apoptosis in CACO-2 and HCT-116 cells and interfered with the cell cycle. Western blotting showed an increased expression of LC3-B, suggestive of autophagy, and Annexin A2, an apoptosis regulatory protein. Molecular docking confirmed the interaction of major fatty acids with Annexin A2, suggesting a role of açaí seed oil in modulating Annexin A2 expression in these cancer cell lines. Our results suggest the anti-tumor potential of açaí seed oil in colorectal adenocarcinoma cells and contribute to the development of an active drug from a known natural product.

Bone Marrow Microenvironment-Induced Chemoprotection in KMT2A Rearranged Pediatric AML Is Overcome by Azacitidine-Panobinostat Combination

Advances in therapies of pediatric acute myeloid leukemia (AML) have been minimal in recent decades. Although 82% of patients will have an initial remission after intensive therapy, approximately 40% will relapse. KMT2A is the most common chromosomal translocation in AML and has a poor prognosis resulting in high relapse rates and low chemotherapy efficacy. Novel targeted approaches are needed to increase sensitivity to chemotherapy. Recent studies have shown how interactions within the bone marrow (BM) microenvironment help AML cells evade chemotherapy and contribute to relapse by promoting leukemic blast survival. This study investigates how DNA hypomethylating agent azacitidine and histone deacetylase inhibitor panobinostat synergistically overcome BM niche-induced chemoprotection modulated by stromal, endothelial, and mesenchymal stem cells and the extracellular matrix (ECM). We show that direct contact between AML cells and BM components mediates chemoprotection. We demonstrate that azacitidine and panobinostat synergistically sensitize MV4;11 cells and KMT2A rearranged pediatric patient-derived xenograft lines to cytarabine in multicell coculture. Treatment with the epigenetic drug combination reduced leukemic cell association with multicell monolayer and ECM in vitro and increased mobilization of leukemic cells from the BM in vivo. Finally, we show that pretreatment with the epigenetic drug combination improves the efficacy of chemotherapy in vivo.

S100A10 Is a New Prognostic Biomarker Related to the Malignant Molecular Features and Immunosuppression Process of Adult Gliomas

OBJECTIVE

Previous studies have demonstrated the role of S100A10 in the progression of several tumors; however, few studies have investigated its immunological characteristics in adult gliomas. In this study, we systematically explored its biological features and clinical significance in adult gliomas.

METHODS

Altogether, 325 glioma cases from the Chinese Glioma Genome Atlas and 699 glioma cases from The Cancer Genome Atlas were included as the training and validation cohorts. R software was used for data analysis and mapping using the RNA sequencing data from these cases. One-way analysis of variance and Student's t-test were used to assess the differences between the groups. Differences were considered statistically significant at P < 0.05.

RESULTS

We found that S100A10 was remarkably highly expressed in high-grade glioma, isocitrate dehydrogenase wild type, 1p19q noncodeletion type, O⁶-methylguanine-DNA methyltransferase promoter unmethylation type, and mesenchymal-like molecular subtype. S100A10 specifically and sensitively indicates the mesenchymal-like molecular subtype. Upregulated S100A10 levels were independently correlated with poor survival. S100A10-related biological processes in gliomas mainly concentrate on immunoreaction and inflammatory response. We then proved that S100A10 was positively related to most inflammatory metagenes, except IgG, including HCK, LCK, MHC II, STAT1, and interferon. More importantly, the levels of glioma-infiltrating immune cells were positively associated with the expression of S100A10, especially in tumor-related macrophages, regulatory T cells, and myeloid-derived suppressor cells.

CONCLUSIONS

S100A10 is closely related to malignant pathological subtypes, worse prognosis, and immunosuppressive immune cell infiltration in adult gliomas, making it a promising biomarker and potential target in the diagnosis, treatment, and prognostic assessment of gliomas.

Annexin A2: The Diversity of Pathological Effects in Tumorigenesis and Immune Response

Annexin A2 (ANXA2) is widely used as a marker in a variety of tumors. By regulating multiple signal pathways, ANXA2 promotes the epithelial-mesenchymal transition, which can cause tumorigenesis and accelerate thymus degeneration. The elevated ANXA2 heterotetramer facilitates the production of plasmin, which participates in pathophysiologic processes such as tumor cell invasion and metastasis, bleeding diseases, angiogenesis, inducing the expression of inflammatory factors. In addition, the ANXA2 on the cell membrane mediates immune response via its interaction with surface proteins of pathogens, C1q, toll-like receptor 2, anti-dsDNA antibodies and immunoglobulins. Nuclear ANXA2 plays a role as part of a primer recognition protein complex that enhances DNA synthesis and cells proliferation by acting on the G1-S phase of the cell. ANXA2 reduction leads to the inhibition of invasion and metastasis in multiple tumor cells, bleeding complications in acute promyelocytic leukemia, retinal angiogenesis, autoimmunity response and tumor drug resistance. In this review, we provide an update on the pathological effects of ANXA2 in both tumorigenesis and the immune response. We highlight ANXA2 as a critical protein in numerous malignancies and the immune host response.

The Bone Marrow Microenvironment in B-Cell Development and Malignancy

B lymphopoiesis is characterized by progressive loss of multipotent potential in hematopoietic stem cells, followed by commitment to differentiate into B cells, which mediate the humoral response of the adaptive immune system. This process is tightly regulated by spatially distinct bone marrow niches where cells, including mesenchymal stem and progenitor cells, endothelial cells, osteoblasts, osteoclasts, and adipocytes, interact with B-cell progenitors to direct their proliferation and differentiation. Recently, the B-cell niche has been implicated in initiating and facilitating B-cell precursor acute lymphoblastic leukemia. Leukemic cells are also capable of remodeling the B-cell niche to promote their growth and survival and evade treatment. Here, we discuss the major cellular components of bone marrow niches for B lymphopoiesis and the role of the malignant B-cell niche in disease development, treatment resistance and relapse. Further understanding of the crosstalk between leukemic cells and bone marrow niche cells will enable development of additional therapeutic strategies that target the niches in order to hinder leukemia progression.

In BCR-ABL1 Positive B-Cell Acute Lymphoblastic Leukemia, Steroid Therapy Induces Hypofibrinogenemia

Hypofibrinogenemia (HF) in adult acute lymphoblastic leukemia (ALL) of B lineage is uncommon and mostly associated with asparaginase (ASP) delivery. Since we noticed a significant reduction in fibrinogen (FBG) plasma levels even before the first ASP dose, we aim to assess the levels of FBG during induction treatment and explore if the FBG fall correlated with therapies other than asparaginase and/or specific leukemia biological features. We retrospectively analyzed FBG levels in 115 patients with B-ALL. In 74 (64%) out of 115 patients FBG decline occurred during the steroid prephase. In univariate analysis, such a steroid-related HF was significantly associated with BCR-ABL1 rearrangement (p = 0.00158). None of those experiencing HF had significant modifications of liver function tests during induction treatment. Our retrospective study suggests that in B-ALL, steroid therapy can also induce HF and that such an event is preferentially observed in patients carrying BCR-ABL1 rearrangements. The pathogenesis of this phenomenon is still unclear. We attempt to explain it by applying the International Society of Thrombosis and Hemostasis-Disseminated Intravascular Coagulation score (ISTH-DIC score); nonetheless additional studies are needed to clarify further the mechanisms of HF in this subset of patients.

Clinical significance of serum S100A10 in lung cancer

Objective

To investigate the clinical significance of serum S100 calcium-binding protein A10 (S100A10) levels in lung cancer.

Methods

This prospective study enrolled patients with lung cancer, patients with benign lung nodules and healthy control subjects. Serum S100A10 levels and three biomarkers were measured and compared between the groups. Associations between serum S100A10 and clinical characteristics in patients with lung cancer were investigated. The diagnostic efficacy of serum S100A10 and carcinoembryonic antigen for lung cancer was calculated.

Results

The study enrolled 82 patients with lung cancer, 21 with benign lung nodules and 50 healthy controls. Serum S100A10 levels were significantly higher in patients with lung cancer compared with patients with benign lung nodules and healthy control subjects. Serum S100A10 levels of patients with advanced lung cancer were significantly higher than those with early stage disease. Patients with lymph node metastases had significantly higher serum S100A10 levels than patients without lymph node metastases. The cut-off serum S100A10 value for lung cancer detection was 1.34 ng/ml, which had a sensitivity of 48.2%, a specificity of 76.2% and an area under the curve of 0.63.

Conclusion

Serum S100A10 was significantly correlated with disease stage and lymph node metastasis. It has the potential to be a tumour biomarker for lung cancer.

CD81 knockout promotes chemosensitivity and disrupts in vivo homing and engraftment in acute lymphoblastic leukemia

Relapse remains a major obstacle to achieving 100% overall survival rate in pediatric hematologic malignancies like acute lymphoblastic leukemia (ALL). Relapse often results from the development of chemoresistance. One of the mechanisms of chemoresistance involves ALL cell interactions with the bone marrow (BM) microenvironment, providing a sanctuary. This phenomenon is known as BM microenvironment-induced chemoprotection. Members of the transmembrane 4 superfamily (tetraspanins; TSPANs) are known to mediate microenvironmental interactions and have been extensively studied in solid tumors. Although the TSPAN family member CD81 is a minimal residual disease marker, its biological role in ALL is not well characterized. We show for the first time that CD81 knockout induces chemosensitivity, reduces cellular adhesion, and disrupts in vivo BM homing and engraftment in B-ALL. This chemosensitization is mediated through control of Bruton tyrosine kinase signaling and induction of p53-mediated cell death. We then show how CD81-related signaling can be disrupted by treatment with the epigenetic drug combination of DNA hypomethylating agent azacitidine (aza) and histone deacetylase inhibitor panobinostat (pano), which we previously used to sensitize ALL cells to chemotherapy under conditions that promote BM microenvironment-induced chemoprotection. Aza/pano-mediated modulation of CD81 surface expression is involved in decreasing BM load by promoting ALL cell mobilization from BM to peripheral blood and increasing response to chemotherapy in disseminated patient-derived xenograft models. This study identifies the novel role of CD81 in BM microenvironment-induced chemoprotection and delineates the mechanism by which aza/pano successfully sensitizes ALL cells via modulation of CD81.

Plasmin and Plasminogen System in the Tumor Microenvironment: Implications for Cancer Diagnosis, Prognosis, and Therapy

Simple Summary

In this review, we present a detailed discussion of how the plasminogen-activation system is utilized by tumor cells in their unrelenting attack on the tissues surrounding them. Plasmin is an enzyme which is responsible for digesting several proteins that hold the tissues surrounding solid tumors together. In this process tumor cells utilize the activity of plasmin to digest tissue barriers in order to leave the tumour site and spread to other parts of the body. We specifically focus on the role of plasminogen receptor—p11 which is an important regulatory protein that facilitates the conversion of plasminogen to plasmin and by this means promotes the attack by the tumour cells on their surrounding tissues.

Abstract

The tumor microenvironment (TME) is now being widely accepted as the key contributor to a range of processes involved in cancer progression from tumor growth to metastasis and chemoresistance. The extracellular matrix (ECM) and the proteases that mediate the remodeling of the ECM form an integral part of the TME. Plasmin is a broad-spectrum, highly potent, serine protease whose activation from its precursor plasminogen is tightly regulated by the activators (uPA, uPAR, and tPA), the inhibitors (PAI-1, PAI-2), and plasminogen receptors. Collectively, this system is called the plasminogen activation system. The expression of the components of the plasminogen activation system by malignant cells and the surrounding stromal cells modulates the TME resulting in sustained cancer progression signals. In this review, we provide a detailed discussion of the roles of plasminogen activation system in tumor growth, invasion, metastasis, and chemoresistance with specific emphasis on their role in the TME. We particularly review the recent highlights of the plasminogen receptor S100A10 (p11), which is a pivotal component of the plasminogen activation system.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

S100A10 Accelerates Aerobic Glycolysis and Malignant Growth by Activating mTOR-Signaling Pathway in Gastric Cancer

S100 calcium-binding protein A10 (S100A10) is crucially involved in the tumorigenesis of multiple malignant tumors. Reprogrammed glucose metabolism is emerging as a hallmark of various human cancers. However, the function of S100A10 in aerobic glycolysis is unclear. The expression of S100A10 was analyzed using the Oncomine database, Gene Expression Profiling Interactive Analysis (GEPIA), The Cancer Genome Atlas (TCGA), and the UALCAN cancer database. Prognostic analysis was performed using the Kaplan-Meier Plotter. The correlation between S100A10 and key glycolytic factors was assessed by GEPIA. The glycolysis level was examined by determining glucose consumption, lactate production, adenosine triphosphate production, cellular oxygen consumption rate, and extracellular acidification rate. Cell apoptosis was investigated by flow cytometry. Colony formation and BrdU assays were performed to detect cell proliferation. A subcutaneous xenograft mouse model was established to evaluate the effects of S100A10 in vivo. Gene Set Enrichment Analysis and western blotting were performed to explore the downstream signaling pathway. S100A10 was significantly upregulated in gastric cancer. Its expression was associated with poor survival. S100A10 increased glucose consumption, lactate production, and the switch from oxidative phosphorylation to aerobic glycolysis. S100A10 promoted malignant proliferation and suppressed cell apoptosis in gastric cancer. S100A10 activated the mTOR pathway by interacting with annexin A2 (ANXA2) to accelerate tumor glycolysis, resulting in tumor malignant progression. S100A10 contributed to aerobic glycolysis and accelerated malignant growth by modulating the Src/ANXA2/AKT/mTOR signaling pathway. Thus, S100A10 may have pivotal roles in gastric cancer.

Circular RNA profile of acute myeloid leukaemia indicates circular RNA annexin A2 as a potential biomarker and therapeutic target for acute myeloid leukaemia

This study was to investigate the circular RNA (circRNA) expression profile and the potential circRNAs as biomarkers and therapeutic targets for acute myeloid leukaemia (AML). CircRNA expression profile in bone marrow mononuclear cells from 5 AML patients and 5 healthy donor controls (HCs) was evaluated by microarray. Then, 10 candidate circRNAs (top 5 upregulated and top 5 downregulated) from microarray were validated by RT-qPCR in 130 AML patients and 50 HCs. Finally, the effects of circRNA annexin A2 (circ-ANXA2) knockdown on cell proliferation, apoptosis, chemosensitivity to cytarabine, daunorbicin and potential target microRNAs were assessed in THP-1 and KG-1 cells. By microarray, 173 upregulated and 181 downregulated circRNAs were found in AML patients than HCs, and these circRNAs were found in AML patients compared with HCs, and these circRNAs were implicated in AML-related pathways such as ErbB and EGFR pathways. By RT-qPCR, 9 of 10 candidate circRNAs (including circ-RPS6KB1, circ-CSMD2, circ-PTK2, circ-ANXA2, circ-PWP2, circ-RBM5, circ-ZZEF1, circ-GSK3B and circ-FOXP1) were dysregulated in AML patients compared with HCs. Circ-ANXA2 correlated with higher disease risk, poor risk stratification, lower complete remission level, shorter event-free survival and overall survival in AML. In cellular experiments, circ-ANXA2 was upregulated in AML cell lines, and its knockdown suppressed proliferation, enhanced apoptosis of THP-1 and KG-1 cells and increased their chemosensitivity to cytarabine and daunorbicin. Additionally, circ-ANXA2 knockdown promoted microRNA (miR)-23a-5p and miR-503-3p expression in THP-1 and KG-1 cells. In conclusion, our findings provide a macroscopic view of the circRNA expression profile in AML, and demonstrate that circ-ANXA2 may be a potential biomarker and therapeutic target for AML.

Modulation of Ion Channels and Receptors by p11 (S100A10)

p11 (S100A10, annexin II light chain, calpactin I light chain) is a multifunctional protein that forms a heterotetrameric complex with Annexin A2, particularly at cell membranes. p11, alone or together with Annexin A2, interacts with several ion channels and receptors and regulates their cellular localization and function. Altered levels of p11 are implicated in the pathophysiology of several forms of cancer, psychiatric disorders, and neurodegeneration. Via interactions with ion channels and receptors, p11 modulates therapeutic actions of drugs targeting brain disorders. By serving as a plasminogen receptor, p11 plays an important role in plasmin generation, fibrinolysis, angiogenesis, tumor progression, and metastasis. Here, we review mechanisms whereby p11 regulates functions of ion channels and receptors in health and disease states.

Multiple functions of S100A10, an important cancer promoter

The S100 group of calcium binding proteins is composed of 21 members that exhibit tissue/cell specific expressions. These S100 proteins bind a diverse range of targets and regulate multiple cellular processes, including proliferation, migration and differentiation. S100A10, also known as p11, binds mainly to annexin A2 and mediates the conversion of plasminogen to an active protease, plasmin. Higher S100A10 expression has been reported to link to worse outcome and/or chemoresistance in a number of cancer types in lung, breast, ovary, pancreas, gall bladder and colorectum and leukemia although some discrepancy was reported. In this review, we focused on the roles of the S100A10 in cancer. We summarized its biological functions, role in cancer progression, prognostic value and targeting of S100A10 for cancer therapy.

S100A10 and Cancer Hallmarks: Structure, Functions, and its Emerging Role in Ovarian Cancer

S100A10, which is also known as p11, is located in the plasma membrane and forms a heterotetramer with annexin A2. The heterotetramer, comprising of two subunits of annexin A2 and S100A10, activates the plasminogen activation pathway, which is involved in cellular repair of normal tissues. Increased expression of annexin A2 and S100A10 in cancer cells leads to increased levels of plasmin—which promotes the degradation of the extracellular matrix—increased angiogenesis, and the invasion of the surrounding organs. Although many studies have investigated the functional role of annexin A2 in cancer cells, including ovarian cancer, S100A10 has been less studied. We recently demonstrated that high stromal annexin A2 and high cytoplasmic S100A10 expression is associated with a 3.4-fold increased risk of progression and 7.9-fold risk of death in ovarian cancer patients. Other studies have linked S100A10 with multidrug resistance in ovarian cancer; however, no functional studies to date have been performed in ovarian cancer cells. This article reviews the current understanding of S100A10 function in cancer with a particular focus on ovarian cancer.

S100 Proteins in Acute Myeloid Leukemia

The S100 protein family contains 20 functionally expressed members, which are commonly dysregulated in cancer. Their wide range of functions includes cell proliferation, cell differentiation, regulation of transcription factors, inflammation, chemotaxis, and angiogenesis. S100 proteins have in several types of cancer proven to be biomarkers for disease progression and prognosis. Acute myeloid leukemia (AML) is a highly heterogeneous and aggressive disease in which immature myeloblasts replace normal hematopoietic cells in the bone marrow. This review focuses on the S100 protein family members, which commonly are dysregulated in AML, and on the consequences of their dysregulation in the disorder. Like in other cancers, it appears as if S100 proteins are potential biomarkers for leukemogenesis. Furthermore, several S100 members seem to be involved in maintaining the leukemic phenotype. For these reasons, specific S100 proteins might serve as prognostic biomarkers, especially in the patient subset with intermediate/undetermined risk, and as potential targets for patient-adjusted therapy. Because the question of the most suitable candidate S100 biomarkers in AML still is under discussion, because particular AML subgroups lead to specific S100 signatures, and because downstream effects and the significance of co-expression of potential S100 binding partners in AML are not fully elucidated yet, we conclude that a panel of S100 proteins will probably be best suited for prognostic purposes.

Eviction from the sanctuary: Development of targeted therapy against cell adhesion molecules in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a malignant hematological disease afflicting hematopoiesis in the bone marrow. While 80%-90% of patients diagnosed with ALL will achieve complete remission at some point during treatment, ALL is associated with high relapse rate, with a 5-year overall survival rate of 68%. The initial remission failure and the high rate of relapse can be attributed to intrinsic chemoprotective mechanisms that allow persistence of ALL cells despite therapy. These mechanisms are mediated, at least in part, through the engagement of cell adhesion molecules (CAMs) within the bone marrow microenvironment. This review assembles CAMs implicated in protection of leukemic cells from chemotherapy. Such studies are limited in ALL. Therefore, CAMs that are associated with poor outcomes or are overexpressed in ALL and have been shown to be involved in chemoprotection in other hematological cancers are also included. It is likely that these molecules play parallel roles in ALL because the CAMs identified to be a factor in ALL chemoresistance also work similarly in other hematological malignancies. We review the signaling mechanisms activated by the engagement of CAMs that provide protection from chemotherapy. Development of targeted therapies against CAMs could improve outcome and raise the overall cure rate in ALL.

Epigenetic drug combination overcomes osteoblast-induced chemoprotection in pediatric acute lymphoid leukemia

Although there has been much progress in the treatment of acute lymphoblastic leukemia (ALL), decreased sensitivity to chemotherapy remains a significant issue. Recent studies have shown how interactions with the bone marrow microenvironment can protect ALL cells from chemotherapy and allow for the persistence of the disease. Epigenetic drugs have been used for the treatment of ALL, but there are no reports on whether these drugs can overcome bone marrow-induced chemoprotection. Our study investigates the ability of the DNA methyltransferase inhibitor azacitidine and the histone deacetylase inhibitor panobinostat to overcome chemoprotective effects mediated by osteoblasts. We show that the combination of azacitidine and panobinostat has a synergistic killing effect and that this combination is more effective than cytarabine in inducing ALL cell death in co-culture with osteoblasts. We also show that this combination can be used to sensitize ALL cells to chemotherapeutics in the presence of osteoblasts. Finally, we demonstrate that these effects can be replicated ex vivo in a number of mouse passaged xenograft lines from both B-ALL and T-ALL patients with varying cytogenetics. Thus, our data provides evidence that azacitidine and panobinostat can successfully overcome osteoblast-induced chemoprotection in vitro and ex vivo in both B-ALL and T-ALL cells.

Generation of Pediatric Leukemia Xenograft Models in NSG-B2m Mice: Comparison with NOD/SCID Mice

Generation of orthotopic xenograft mouse models of leukemia is important to understand the mechanisms of leukemogenesis, cancer progression, its cross talk with the bone marrow microenvironment, and for preclinical evaluation of drugs. In these models, following intravenous injection, leukemic cells home to the bone marrow and proliferate there before infiltrating other organs, such as spleen, liver, and the central nervous system. Moreover, such models have been shown to accurately recapitulate the human disease and correlate with patient response to therapy and prognosis. Thus, various immune-deficient mice strains have been used with or without recipient preconditioning to increase engraftment efficiency. Mice homozygous for the severe combined immune deficiency (SCID) mutation and with non-obese diabetic background (NOD/SCID) have been used in the majority of leukemia xenograft studies. Later, NOD/SCID mice deficient for interleukin 2 receptor gamma chain (IL2Rγ) gene called NSG mice became the model of choice for leukemia xenografts. However, engraftment of leukemia cells without irradiation preconditioning still remained a challenge. In this study, we used NSG mice with null alleles for major histocompatibility complex class I beta2-microglobulin (β2m) called NSG-B2m. This is a first report describing the 100% engraftment efficiency of pediatric leukemia cell lines and primary samples in NSG-B2m mice in the absence of host preconditioning by sublethal irradiation. We also show direct comparison of the engraftment efficiency and growth rate of pediatric acute leukemia cells in NSG-B2m and NOD/SCID mice, which showed 80–90% engraftment efficiency. Secondary and tertiary xenografts in NSG-B2m mice generated by injection of cells isolated from the spleens of leukemia-bearing mice also behaved similar to the primary patient sample. We have successfully engrafted 25 acute lymphoblastic leukemia (ALL) and 5 acute myeloid leukemia (AML) patient samples with distinct cytogenetic characteristics in NSG-B2m mice, with the purpose of generating pediatric ALL and AML xenografts for preclinical evaluation of drugs. Thus, our data support the use of NSG-B2m mouse model for leukemia engraftment and in vivo preclinical drug efficacy studies.