Acquired expression of osteopontin selectively promotes enrichment of leukemia stem cells through AKT/mTOR/PTEN/β-catenin pathways in AML cells

In Vitro Study of the Anti-inflammatory and Antifibrotic Activity of Tannic Acid-Coated Curcumin-Loaded Nanoparticles in Human Tenocytes

Tendinitis is a tendon disorder related to inflammation and pain, due to an injury or overuse of the tissue, which is hypocellular and hypovascular, leading to limited repair which occurs in a disorganized deposition of extracellular matrix that leads to scar formation and fibrosis, ultimately resulting in impaired tendon integrity. Current conventional treatments are limited and often ineffective, highlighting the need for new therapeutic strategies. In this work, acetalated-dextran nanoparticles (AcDEX NPs) loaded with curcumin and coated with tannic acid (TA) are developed to exploit the anti-inflammatory and anti-fibrotic properties of the two compounds. For this purpose, a microfluidic technique was used in order to obtain particles with a precise size distribution, aiming to decrease the batch-to-batch variability for possible future clinical translation. Coating with TA increased not only the stability of the nanosystem in different media but also enhanced the interaction and the cell-uptake in primary human tenocytes and KG-1 macrophages. The nanosystem exhibited good biocompatibility toward these cell types and a good release profile in an inflammatory environment. The efficacy was demonstrated by real-time quantitative polymerase chain reaction, in which the curcumin loaded in the particles showed good anti-inflammatory properties by decreasing the expression of NF-κb and TA-coated NPs showing anti-fibrotic effect, decreasing the gene expression of TGF-β. Overall, due to the loading of curcumin and TA in the AcDEX NPs, and their synergistic activity, this nanosystem has promising properties for future application in tendinitis.

Differential Gene Expression Profiling in Alveolar Echinococcosis Identifies Potential Biomarkers Associated With Angiogenesis

Background

Alveolar echinococcosis (AE) is a worldwide zoonosis caused by Echinococcus multilocularis. Alveolar echinococcosis is a severe chronic parasitic disease that exhibits a tumor-like growth, with the potential for invasion and distant metastasis; however, the molecular mechanism underlying this condition remains unclear.

Methods

Transcriptome analyses were performed to detect differentially expressed genes (DEGs) in samples from patients with AE with invasion and distant metastasis. The results were further verified by immunohistochemistry.

Results

A total of 1796 DEGs were identified, including 1742 upregulated and 54 downregulated DEGs. A subsequent functional analysis showed that the significant DEGs were involved in the angiogenesis process. Immunohistochemical analysis confirmed the reliability of the transcriptomic data.

Conclusions

These results suggest that angiogenesis is a possible mechanism underlying the tumor-like biological behavior observed during E multilocularis infection. Genes related to this process may play important roles in AE invasion and distant metastasis.

Osteopontin is required for the maintenance of leukemia stem cells in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic disorder with a poor prognosis. The clinical significance of Leukemia stem cells (LSCs) plays an important role in the generation of AML and is the main cause of the recurrence after remission. Osteopontin (OPN), an extracellular matrix protein, has been implicated in hematopoietic malignancies. However, the specific role and the underlying mechanism of AML cell autocrined OPN in leukemia maintenance remain unknown. Here, we showed that knockdown of Opn expression significantly prolonged the survival of mice with MLL-AF9 cell-induced AML and markedly reduced the tumor burden. The LSCs from the Opn-knockdown groups exhibited decreased numbers and impaired function as determined by immunophenotype, colony-forming and limiting dilution assays. Further analysis revealed that Opn prevents LSCs from undergoing apoptosis and cell cycle arrest. Repression of OPN in human AML cell lines in vitro mimics the phenotypes observed in the mouse model. Overall, our data indicated that OPN is a potent therapeutic target for eradicating LSCs in AML.

Molecular Systems Architecture of Interactome in the Acute Myeloid Leukemia Microenvironment

A molecular systems architecture is presented for acute myeloid leukemia (AML) to provide a framework for organizing the complexity of biomolecular interactions. AML is a multifactorial disease resulting from impaired differentiation and increased proliferation of hematopoietic precursor cells involving genetic mutations, signaling pathways related to the cancer cell genetics, and molecular interactions between the cancer cell and the tumor microenvironment, including endothelial cells, fibroblasts, myeloid-derived suppressor cells, bone marrow stromal cells, and immune cells (e.g., T-regs, T-helper 1 cells, T-helper 17 cells, T-effector cells, natural killer cells, and dendritic cells). This molecular systems architecture provides a layered understanding of intra- and inter-cellular interactions in the AML cancer cell and the cells in the stromal microenvironment. The molecular systems architecture may be utilized for target identification and the discovery of single and combination therapeutics and strategies to treat AML.

Regulatory T cells promote the stemness of leukemia stem cells through IL10 cytokine-related signaling pathway

Regulatory T cells (Tregs) could maintain the characteristics of stem cells and inhibit the differentiation of normal hematopoietic stem/progenitor cells. Recent studies have shown that Tregs, as an important component of acute myeloid leukemia (AML) microenvironments, can help AML cells to evade immune surveillance. However, their function in directly regulating the stemness of AML cells remains elusive. In this study, the increased stemness of AML cells promoted by Tregs was verified in vitro and in vivo. The cytokines released by Tregs were explored, the highly expressed anti-inflammatory cytokine IL10 was found, which could promote the stemness of AML cells through the activation of PI3K/AKT signal pathway. Moreover, disrupting the IL10/IL10R/PI3K/AKT signal in AML/ETO c-kit^mut (A/Ec) leukemia mice could prolong the mice survival and reduce the stemness of A/Ec leukemia cells. Finally, it was confirmed in patient samples that the proportion of Tregs to leukemia stem cells (LSCs) was positively correlated, and in CD34⁺ primary AML cells, the activation of PI3K/AKT was stronger in patients with high Tregs' infiltration. After rhIL10 treatment, primary AML cells showed increased activation of PI3K/AKT signaling. Therefore, blocking the interaction between Tregs and AML cells may be a new approach to target LSCs in AML treatment.

Prognostic and predictive significance of osteopontin in malignant neoplasms

Osteopontin is an extracellular matrix protein which is produced by different types of cells and plays an important functional role in many biological processes. This review discusses the main functions of osteopontin, its role in the progression and chemoresistance of malignant neoplasms, in the regulation of epithelial-mesenchymal transition, angiogenesis, and the body’s immune response to the tumor. The article considers the currently known mechanisms by which osteopontin affects to the survival, mobility and invasion of tumor cells, to tumor sensitivity to drug treatment, as well as the prospects for a integrated study of the predictive significance of osteopontin, markers of hypoxia, angiogenesis, epithelial- mesenchymal transition, and immunological tolerance.

The extracellular matrix: A key player in the pathogenesis of hematologic malignancies

Hematopoietic stem and progenitor cells located in the bone marrow lay the foundation for multiple lineages of mature hematologic cells. Bone marrow niches are architecturally complex with specific cellular, physiochemical, and biomechanical factors. Increasing evidence suggests that the bone marrow microenvironment contributes to the pathogenesis of hematological neoplasms. Numerous studies have deciphered the role of genetic mutations and chromosomal translocations in the development hematologic malignancies. Significant progress has also been made in understanding how the cellular components and cytokine interactions within the bone marrow microenvironment promote the evolution of hematologic cancers. Although the extracellular matrix is known to be a key player in the pathogenesis of various diseases, it's role in the progression of hematologic malignancies is less understood. In this review, we discuss the interactions between the extracellular matrix and malignant cells, and provide an overview of the role of extracellular matrix remodeling in sustaining hematologic malignancies.

Effects of different autophagy inhibitors on sensitizing KG-1 and HL-60 leukemia cells to chemotherapy

A little number of current autophagy inhibitors may have beneficial effects on the acute myeloid leukemia (AML) patients. However, there is a strong need to figure out which settings should be activated or inhibited in autophagy pathway to prevail drug resistance and also to improve current treatment options in leukemia. Therefore, this study aimed to compare the effects of well-known inhibitors of autophagy (as 3-MA, BafA1, and HCQ) in leukemia KG-1 and HL-60 cells exposed to arsenic trioxide (ATO) and/or all-trans retinoic acid (ATRA). Cell proliferation and cytotoxicity of cells were examined by MTT assay. Autophagy was studied by evaluating the development of acidic vesicular organelles, and the autophagosomes formation was investigated by acridine orange staining and transmission electron microscopy. Moreover, the gene and protein expressions levels of autophagy markers (ATGs, p62/SQSTM1, and LC-3B) were also performed by qPCR and western blotting, respectively. The rate of apoptosis and cell cycle were evaluated using flow cytometry. We compared the cytotoxic and apoptotic effects of ATO and/or ATRA in both cell lines and demonstrated that some autophagy markers upregulated in this context. Also, it was shown that autophagy blockers HCQ and/or BafA1 could potentiate the cytotoxic effects of ATO/ATRA, which were more pronounced in KG-1 cells compared to HL-60 cell line. This study showed the involvement of autophagy during the treatment of KG-1 and HL-60 cells by ATO/ATRA. This study proposed that therapy of ATO/ATRA in combination with HCQ can be considered as a more effective strategy for targeting leukemic KG-1 cells.

E35 ablates acute leukemia stem and progenitor cells in vitro and in vivo

Leukemia stem cells (LSCs) have critical functions in acute leukemia (AL) pathogenesis, participating in its initiation and relapse. Thus, identifying new molecules to eradicate LSCs represents a high priority for AL management. This work identified E35, a novel Emodin derivative, which strongly inhibited growth and enhanced apoptosis of AL stem cell lines, and primary stem and progenitor cells from AL cases, while sparing normal hematopoietic cells. Furthermore, functional assays in cultured cells and animals suggested that E35 preferentially ablated primitive leukemia cell populations without impairing their normal counterparts. Moreover, molecular studies showed that E35 remarkably downregulated drug-resistant gene and dramatically inhibited the Akt/mammalian target of rapamycin signaling pathway. Notably, the in vivo anti-LSC activity of E35 was further confirmed in murine xenotransplantation models. Collectively, these findings indicate E35 constitutes a novel therapeutic candidate for AL, potentially targeting leukemia stem and progenitor cells.

Curcumin Combined with Thalidomide Reduces Expression of STAT3 and Bcl-xL, Leading to Apoptosis in Acute Myeloid Leukemia Cell Lines

Introduction

Acute myeloid leukemia (AML) is a type of blood disorder that exhibits uncontrolled growth and reduced ability to undergo apoptosis. Signal transducer and activator of transcription 3 (STAT3) is a family member of transcription factors which promotes carcinogenesis in most human cancers. This effect on AML is accomplished through deregulation of several critical genes, such as B cell lymphoma-extra-large (BCL-XL) which is anti-apoptotic protein. The aim of this study was to evaluate the effect of curcumin (CUR) and thalidomide (THAL) on apoptosis induction and also the alteration of the mRNA expression level of STAT3 and BCL-XL mRNA on AML cell line compounds.

Methods

The growth inhibitory effects of CUR and THAL and their combination were measured by MTT assay in U937 and KG-1 cell lines. The rates of apoptosis induction and cell cycle analysis were measured by concurrent staining with Annexin V and PI. The mRNA expression level of STAT3 and BCL-XL was evaluated by Real-Time PCR.

Results

CUR inhibited proliferation and induced apoptosis in both KG-1 and U937 cells and this effect increased by combination with THAL. The expression level of STAT3 and BCL-XL was significantly down-regulated in KG-1 cells after treatment by CUR and THAL and their combination.

Conclusion

Overall, our findings suggested that down-regulation of STAT3 and BCL-XL mRNA expression in response to CUR and THAL treatment lead to inhibition of cell growth and induction of apoptosis.

Effects of Sorafenib and Arsenic Trioxide on U937 and KG-1 Cell Lines: Apoptosis or Autophagy?

Objective

Acute myeloid leukemia (AML) is a clonal disorder of hemopoietic progenitor cells. The Raf serine/threonine (Ser/Thr) protein kinase isoforms including B-Raf and RAF1, are the upstream in the MAPK cascade that play essential functions in regulating cellular proliferation and survival. Activated autophagy-related genes have a dual role in both cell death and cell survival in cancer cells. The cytotoxic activities of arsenic trioxide (ATO) were widely assessed in many cancers. Sorafenib is known as a multikinase inhibitor which acts through suppression of Ser/Thr kinase Raf that was reported to have a key role in tumor cell signaling, proliferation, and angiogenesis. In this study, we examined the combination effect of ATO and sorafenib in AML cell lines.

Materials and Methods

In this experimental study, we studied in vitro effects of ATO and sorafenib on human leukemia cell lines. The effective concentrations of compounds were determined by MTT assay in both single and combination treatments. Apoptosis was evaluated by annexin-V FITC staining. Finally, mRNA levels of apoptotic and autophagy genes were evaluated using real-time polymerase chain reaction (PCR).

Results

Data demonstrated that sorafenib, ATO, and their combination significantly increase the number of apoptotic cells. We found that the combination of ATO and sorafenib significantly reduces the viability of U937 and KG-1 cells. The expression level of selective autophagy genes, ULK1 and Beclin1 decreased but LC3-II increased in U937.

Conclusion

The expression levels of apoptotic and autophagy activator genes were increased in response to treatment. The crosstalk between apoptosis and autophagy is a complicated mechanism and further investigations seem to be necessary.

Arsenic Trioxide and Thalidomide Combination Induces Autophagy Along with Apoptosis in Acute Myeloid Cell Lines

Objective

Autophagy and apoptosis play key roles in cancer survival and pathogenesis and are governed by specific genes which have a dual role in both cell death and survival. Arsenic trioxide (ATO) and thalidomide (THAL) are used for treatment of many types of hematologic malignancies. ATO prevents the proliferation of cells and induces apoptosis in some cancer cells. Moreover, THAL has immunomodulatory and antiangiogenic effects in malignant cells. The aim of present study was to examine the effects of ATO and THAL on U937 and KG-1 cells, and evaluation of mRNA expression level of VEGFs genes, PI3K genes and some of autophagy genes.

Materials and Methods

In this in vitro experimental study, U937 and KG-1 cells were treated by ATO (0.4-5 μM) and THAL (5-100 μM) for 24, 48 and 72 hours. Cell viability was measured by MTT assay. The apoptosis rate and cell cycle arrest were evaluated by flow cytometry (Annexin/PI) and cell cycle flow cytometry analysis, respectively. The effect of ATO/THAL on mRNAs expression was evaluated by real-time polymerase chain reaction (PCR).

Results

ATO/THAL combination enhanced cell apoptosis in a dose-dependent manner. Also, ATO/THAL induced SubG1/ G1 phase arrest. mRNA expression levels of VEGFC (contrary to other VEGFs isoform), PI3K, AKT, mTOR, MEK1, PTEN, IL6, LC3 and P62 genes were upregulated in acute myeloid leukemia (AML) cells following treatment with ATO/THAL.

Conclusion

Combined treatment with ATO and THAL can inhibit proliferation and invasion of AML cells by down-regulating ULK1 and BECLIN1 and up-regulating PTEN and IL6, and this effect was more marked than the effects of ATO and THAL alone.

Leukemia stem cell immunophenotyping tool for diagnostic, prognosis, and therapeutics

The existence of cancer stem cells is debatable in numerous solid tumors, yet in leukemia, there is compelling evidence of this cell population. Leukemic stem cells (LSCs) are altered cells in which accumulating genetic and/or epigenetic alterations occur, resulting in the transition between the normal, preleukemic, and leukemic status. These cells do not follow the normal differentiation program; they are arrested in a primitive state but with high proliferation potential, generating undifferentiated blast accumulation and a lack of a mature cell population. The identification of LSCs might guide stem cell biology research and provide key points of distinction between these cells and their normal counterparts. The identification and characterization of the main features of LSCs can be useful as tools for diagnosis and treatment. In this context, the aim of the present review was to connect immunophenotype data in the main types of leukemia to further guide technical improvements.

Pivotal role of mitophagy in response of acute myelogenous leukemia to a ceramide-tamoxifen-containing drug regimen

Acute myelogenous leukemia (AML) is a hematological malignancy marked by the accumulation of large numbers of immature myeloblasts in bone marrow. The overall prognosis in AML is poor; hence, there is a pressing need to improve treatment. Although the sphingolipid (SL) ceramide demonstrates known cancer suppressor properties, it's mechanism of action is multifaceted. Our studies in leukemia and other cancers have demonstrated that when combined with the antiestrogen, tamoxifen, the apoptosis-inducting effect of ceramide is greatly enhanced. The goal of the present study was to establish whether a ceramide-tamoxifen regimen also affects autophagic-driven cellular responses in leukemia. Using the human AML cell line KG-1, we demonstrate that, unlike exposure to the single agents, combination C6-ceramide-tamoxifen upregulated LC3-II expression, inhibited the mTOR signaling pathway, and synergistically induced KG-1 cell death in an Atg5-dependent manner. In addition, colocalization of autophagosome and mitochondria, indicative of mitophagosome formation and mitophagy, was observed. Versatility of the drug regimen was confirmed by experiments in MV4-11 cells, a FLT3-ITD AML mutant. These results indicate that the C6-ceramide-tamoxifen regimen plays a pivotal role inducing autophagy in AML, and thus constitutes a novel therapeutic design.

Microvesicles of osteoblasts modulate bone marrow mesenchymal stem cell-induced apoptosis to curcumin in myeloid leukemia cells

Microvesicles (MVs) derived from bone marrow niche components have an important role in genetic reprogramming and subsequent drugs induce apoptosis in leukemic cells. Here, we have found that undertreatment of curcumin or daunorubicin, the cross-talk through MVs of KG-1-bone marrow mesenchymal stem cells (BMSCs), significantly downregulates the expression of the survival gene osteopontin (OPN), CXCL-12, IL-6 (interleukin-6), STAT-3, and VCAM-1 (vascular cell adhesion molecule 1) in treated-KG-1 cells as well as exclusively upregulates CXCL-12 in BMSCs. Drug treated-cell populations' MVs of both single cultured osteoblasts (OBs) and cocultured KG-1 + BMSCs + OBs similarly upregulate survival mediators' OPN, CXCL-12, IL-6, STAT-3, and VCAM-1 in treated-KG-1 cells. Likewise, isolated MVs from KG-1 cells or communication between KG-1, BMSCs, and OBs treated by drugs increase the expression of genes OPN, CXCL-12, IL-6, STAT3, and VCAM-1 by OBs. MVs derived from KG-1 + BMSCs + OBs reduce drug-induced apoptosis in KG-1 cells. This suggests MVs-mediated information transfer is a procedure whereby OBs could overcome BMSCs-induced apoptosis in drug-treated-KG-1 cells.

Inhibitory Effects of Arsenic Trioxide and Thalidomide on Angiogenesis and Vascular Endothelial Growth Factor Expression in Leukemia Cells

Acute myeloid leukemia (AML) is a blood disorder characterized by uncontrolled proliferation of myeloid progenitors and decrease in the apoptosis rate. The vascular endothelial growth factor (VEGF) promotes blood vessel regeneration which might play important roles in development and progression of neoplasia. Our previous studies focused on cytotoxicity and anticancer effects of arsenic trioxide (ATO) and thalidomide (THAL) as an anti-VEGF compound in the AML cell model. ATO also affects regulatory genes involved in cell proliferation and apoptosis. The aim of present study was to examine the effects of ATO and THAL alone and in combination on U937 and KG-1 cells, with attention to mRNA expression for VEGF isoforms. Growth inhibitory effects was assessed by MTT assay and apoptosis induction was determined by Annexin/PI staining. mRNA expression levels were evaluated by real-time PCR. Our data indicated that ATO (1.618μM and 1μM in KG-1 and U937 cell lines respectively), THAL (80μM and 60μM) and their combination inhibited proliferation and induced apoptosis in our cell lines. mRNA expression of VEGF (A, B) decreased while C and D isoforms did not show any significant changes. Taken together, according to the obtained results, the VEGF autocrine loop could be a target as a therapeutic strategy for cases of AML.

Oxidative stress in normal hematopoietic stem cells and leukemia

Leukemia is developed following the abnormal proliferation of immature hematopoietic cells in the blood when hematopoietic stem cells lose the ability to turn into mature cells at different stages of maturation and differentiation. Leukemia initiating cells are specifically dependent upon the suppression of oxidative stress in the hypoglycemic bone marrow (BM) environment to be able to start their activities. Relevant literature was identified by a PubMed search (2000-2017) of English-language literature using the terms 'oxidative stress,' 'reactive oxygen species,' 'hematopoietic stem cell,' and 'leukemia.' The generation and degradation of free radicals is a main component of the metabolism in aerobic organisms. A certain level of ROS is required for proper cellular function, but values outside this range will result in oxidative stress (OS). Long-term overactivity of reactive oxygen species (ROS) has harmful effects on the function of cells and their vital macromolecules, including the transformation of proteins into autoantigens and increased degradation of protein/DNA, which eventually leads to the change in pathways involved in the development of cancer and several other disorders. According to the metabolic disorders of cancer, the relationship between OS changes, the viability of cancer cells, and their response to chemotherapeutic agents affecting this pathway are undeniable. Recently, studies have been conducted to determine the effect of herbal agents and cancer chemotherapy drugs on oxidative stress pathways. By emphasizing the role of oxidative stress on stem cells in the incidence of leukemia, this paper attempts to state and summarize this subject.

Osteopontin b and c Splice isoforms in Leukemias and Solid Tumors: Angiogenesis Alongside Chemoresistance

Osteopontin (OPN) is a glycoprotein involved in regulation of various influences on tumor progression, such as cellular proliferation, apoptosis, angiogenesis, and metastasis. Vascular endothelial growth factor (VEGF) is a secreted molecule supporting angiogenesis in various cancers through activation of the PI3K/AKT/ERK1/2 pathway. OPN and VEGF have a number of isoforms with various activities. In spite of the well-defined association between OPN and VEGF isoform expression and cure rate for solid tumors, there is a scarcity of information as to any association in leukemia. Based on the critical role of OPN in cell survival, it seems reasonable to hypothesize that OPN and VEGF isoform expression levels may impact on chemoresistance and relapse in leukemia the same as in solid tumors. Hence, the aim of our review was to explain relationships between OPN and VEGF isoforms and angiogenesis and related pathways in chemoresistance of leukemia and solid tumors. Our findings demonstrated that OPNb and OPNc alongside with VEGF isoforms and other gene pathways are involved in angiogenesis and also might promote chemoresistance and even recurrence in leukemia and solid tumors. To sum up, targeting OPN isoforms, particularly b and c, might be a novel therapeutic strategy for the treatment of leukemia as well as solid tumors.

Anti-Vascular Endothelial Growth Factor Targeting by Curcumin and Thalidomide in Acute Myeloid Leukemia Cells

Acute myeloid leukemias (AMLs) are blood disorders that exhibit uncontrolled growth and reduction of apoptosis rates. As with other malignancies, progression may be result of induction and formation of new blood vessels influenced by disease conditions. Cancer cells produce a variety of factors which play important roles in angiogenesis. Vascular endothelial growth factor (VEGF) is critical for many malignancies, including AMLs. Curcumin, as a natural compound, is able to enhance apoptosis via a mechanism affecting regulatory genes. As a new strategy we here evaluated anti-VEGF properties of curcumin, alone and in combination with thalidomide, in leukemic cell lines. Growth inhibitory effects were assessed by MTT assay and apoptosis was detected by annexin/PI staining in U937 and KG-1 cell lines. mRNA expression levels of VEGF isoforms were evaluated by qRT-PCR. Curcumin inhibited proliferation and induced apoptosis in both KG-1 and U937 cells and this effect was stronger in combination with thalidomide. In KG-1 cells, the level of VEGF (A, B, C and D) mRNA was decreased in curcumin-treated as compared to untreated cells. Maximum effects were obtained at the concentration of 40 μM curcumin in U937 cells. Taken together, the results indicate that the VEGF autocrine loop may have an impact on AML development and progression and could be considered as a therapeutic target. Thalidomide as a VEGF inhibitor in combination with curcumin appears to have a synergistic impact on inhibition of cell proliferation and promotion of apoptosis.

OPN b and c Isoforms Doubtless Veto Anti-angiogenesis Effects of Curcumin in Combination with Conventional AML Regiment

Osteopontin (OPN) is an extracellular structural protein that is secreted by osteoblasts and hematopoietic cells. It suppresses the proliferation of hematopoietic stem and also plays an important role in promoting survival and drug resistance in leukemic stem cells (LSCs). Since the role of OPN isoforms in AML angiogenesis are remaining controversial, in the present study, we aimed to evaluate whether curcumin (CUR), as a known natural component with anti-angiogenesis effects, in a combination of AML conventional regiment has the potency to preclude induced anti-angiogenesis effects of OPN isoforms or not? Leukemia cells were treated with different concentration of CUR and AML conventional drugs alone and/or in combination with together to find effective doses and IC50 values. Percentages of apoptotic cells were evaluated by Annexin/PI staining and mRNA levels of OPN isoforms and AKT/ VEGF-A and VEGF-C/ STAT3/ β-catenin/ CXCR4/ IL-6/ KDR gene expression were investigated by Real Time-PCR method. Moreover, to confirm OPN gene expression data, we investigated the effect of simvastatin and OPN siRNA as an OPN inhibitor on the cell proliferation and induction of apoptosis in the indicated cell lines. Our data display that Ara-c (2μM and 1μM in KG-1 and U937 cell lines respectively), CUR (40μM in both cell lines), and also their combination significantly increased the percentage of apoptotic cells. Moreover, the mRNA level of OPN isoforms were down regulated in the KG-1and U937 cell lines treated with Ara-c while, upregulated in KG-1and U937 cell lines treated with CUR and its combination. Our results suggest that despite anti-angiogenesis effects of CUR, AML cells probably evade from anti-angiogenesis effects of CUR via induction of OPN b and c isoform and related molecular pathways.

Osteopontin and their roles in hematological malignancies: Splice variants on the new avenues

Osteopontin (OPN) is a protein expressed in several tissues, including bone marrow, in which it performs distinct roles, such as modulating hematopoietic stem cell niche and bone remodeling. Most data in hematological malignancies (HMs) refers to total OPN (tOPN), comprehending the sum of distinct OPN splicing isoforms (OPN-SI), while reports describing the expression and roles of each OPN-SI are scarce. This review aims to summarize tOPN roles in HMs and provide evidence that OPN-SIs can also modulate specific functions in HMs biology. We summarize that upregulated tOPN can modulate HMs (leukemia, lymphoma and myeloma) progression, inducing cell adhesion, invasion, angiogenesis, cell differentiation and extramedullary and/or central nervous system infiltration. Based on this expression pattern, tOPN has been pointed out as a biomarker in those HMs, thus providing potential targets for therapeutic approaches. Our group found that OPN-SIs are expressed in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cell lines (unpublished data), providing early evidence that OPN-SIs are also expressed in BCP-ALL. Further studies should investigate whether these OPN-SIs can differently modulate HMs biology and their putative application as auxiliary biomarkers for HMs.

Osteopontin at the Crossroads of Inflammation and Tumor Progression

Complex interactions between tumor and host cells regulate systemic tumor dissemination, a process that begins early at the primary tumor site and goes on until tumor cells detach themselves from the tumor mass and start migrating into the blood or lymphatic vessels. Metastatic cells colonize the target organs and are capable of surviving and growing at distant sites. In this context, osteopontin (OPN) appears to be a key determinant of the crosstalk between cancer cells and the host microenvironment, which in turn modulates immune evasion. OPN is overexpressed in several human carcinomas and has been implicated in inflammation, tumor progression, and metastasis. Thus, it represents one of the most attracting targets for cancer therapy. Within the tumor mass, OPN is secreted in various forms either by the tumor itself or by stroma cells, and it can exert either pro- or antitumorigenic effects according to the cell type and tumor microenvironment. Thus, targeting OPN for therapeutic purposes needs to take into account the heterogeneous functions of the multiple OPN forms with regard to cancer formation and progression. In this review, we will describe the role of systemic, tumor-derived, and stroma-derived OPN, highlighting its pivotal role at the crossroads of inflammation and tumor progression.

Anti-Vascular Endothelial Growth Factor Effects of Sorafenib and Arsenic Trioxide in Acute Myeloid Leukemia Cell Lines

Acute myeloid leukemia (AML), is a clonal disorder caused by acquired somatic mutations and chromosomal rearrangements. According to some evidence, progression of hematolymphoid malignancies depends on the induction of new blood vessel formation under the influence of acute leukemia. Various factors are produced by cancer cells under hypoxic conditions to increase vascular formation. Among these, vascular endothelial growth factor (VEGF) plays a crucial role. Cytotoxicity and anticancer effects of arsenic trioxide (ATO) have been reported in many cancers. Sorafenib, known as an angiogenic inhibitor, decreases leukemic cell survival. The aim of this study was to indicate combination effects of ATO and sorafenib in two AML cell lines, KG-1 and U937. Effective doses was determined by MTT assay for both single and combination treatments. Percentages of apoptotic cells were evaluated by Annexin V FITC staining and mRNA levels of VEGF isoforms and receptor expression were investigated by Real-Time PCR. Our data show that sorafenib (5μM and 7μM in KG-1 and U937 cell lines respectively), ATO (1.618μM and 1μM in KG-1 and U937 cell lines respectively), and also their combination significantly increased the percentage of apoptotic cells. In addition the mRNA level of VEGF isoforms was downregulated in the U937 cell line while upregulated in KG-1 cells. Taken together, our results suggest that the VEGF autocrine loop may have an influence on AML development and progression and could be consider as a therapeutic target. The combination of sorafenib as a VEGF inhibitor with ATO synergistically inhibits cell proliferation and promotes apoptosis.

Osteopontin b and c isoforms: Molecular Candidates Associated with Leukemic Stem Cell Chemoresistance in Acute Myeloid Leukemia

Despite impressive advances in therapeutic approaches, long-term survival with acute myeloid leukemia (AML) is low as a result of treatment resistance and frequent relapse. Among multitude oncogenic proteins involved in acquisition of a chemo-resistanr phenotype, osteopontin (OPN) recently has attracted marked attention. In spite of the well-defined association between OPN expression and cure rate with solid tumors, there is a scarcity of information on any role of this protein in AML cases. Based on the critical role of OPN in cell survival, it seems reasonable to hypothesize that isoform expression levels may impact on regulation of apoptosis in AML cells in response to conventional chemotherapeutic drugs and its relation to relapse. To investigate associations between induction of apoptosis and OPN isoform expression, two distinct AML cell lines (KG-1 as a leukemic stem cell model and U937) were treated with chemotherapy drugs, and cell viability and apoptosis were evaluated by MTT and Annexin/PI assay. After determination of appropriate drug doses, mRNA expression levels of OPN isoforms and OPN-related genes were investigated. Our results demonstrated for the first time that acquired up-regulation of OPN-b and c isoforms might prevent conventional chemotherapy regimen-induced apoptosis in AML cells. Moreover, upregulation of OPN-b and c in AML cells appears concurrent with upregulation of AKT/VEGF/CXCR4/STAT3/ IL-6 gene expression. To sum up, this study suggests that OPN-b and c isoforms could be considered as unique beneficial molecular biomarkers associated with leukemic stem cell chemoresistance. Hence, they have potential as molecular candidates for detection of minimal residual disease (MRD) and determination of remission in AML patients. Further evaluation with quantative real time PCR on patient samples for confirmation appears warranted.

Reciprocal Interactions of Leukemic Cells with Bone Marrow Stromal Cells Promote Enrichment of Leukemic Stem Cell Compartments in Response to Curcumin and Daunorubicin

A predominant challenge in developing curative leukemia therapy is interactions of leukemic cells with the bone marrow stromal microenvironment. We aimed to investigate the role of stromal cells, such as bone marrow mesenchymal stromal cells (BMSCs) and osteoblasts (OBs), in curcumin (CUR) and daunorubicin (DNR) induced apoptosis of acute myeloid leukemia (AML) cells. We used KG1 and U937 as leukemia cell line models and treated them with CUR and DNR. The cells were then co-cultured with BMSCs or a combination of BMSCs and OBs as feeders. After 24 hours of co-culture, BMSCs or OBs were sorted and separated from the leukemia cells and apoptosis levels were analyzed by annexin/propidium iodide (PI) staining on flow cytometry. Potentially involved molecular pathways were analyzed at gene and protein levels by Real time PCR and western blotting, respectively. The results showed AML cells co-cultured with BMSCs plus OBs to be more resistant to drug induced-apoptosis compared to co-culture with BMSCs alone or without co-culture. Expression levels of OPN, CXCL-12, IL-6, STAT-3 and VCAM-1 were also significantly up-regulated in OBs and AML cells, at both mRNA and protein levels after co-culture, with concurrent enrichment of CD34+ AML cells. Our data showed, in a stromal cell niche-based model, that OBs revoke the influence of BMSCs on leukemic cells and promote enrichment of both CD34+ and CD34- leukemic stem cell (LSC) compartments in response to CUR and DNR. Up-regulation of OPN, CXCL-12, IL-6, STAT-3 and VCAM-1 in OBs and AML cells in co-culture might be part of molecular mechanisms that block CUR or CUR+DNR-induced apoptosis and promote enrichment of CD34+ and CD34- LSCs.