Bone marrow mesenchymal stromal cells affect the cell cycle arrest effect of genotoxic agents on acute lymphocytic leukemia cells via p21 down-regulation

The mechanisms of mutual relationship between malignant hematologic cells and mesenchymal stem cells: Does it contradict the nursing role of mesenchymal stem cells?

Mesenchymal stem/stromal cells (MSCs) are known as the issue in biology because of some unpredictable characteristics in the different microenvironments especially in their bone marrow niche. MSCs are used in the regenerative medicine because of their unique potentials for trans-differentiation, immunomodulation, and paracrine capacity. But, their pathogenic and pro-survival effects in tumors/cancers including hematologic malignancies are indisputable. MSCs and/or their derivatives might be involved in tumor growth, metastasis and drug resistance in the leukemias. One of important relationship is MSCs and hematologic malignancy-derived cells which affects markedly the outcome of disease. The communication between these two cells may be contact-dependent and/or contact-independent. In this review, we studied the crosstalk between MSCs and malignant hematologic cells which results the final feedback either the progression or suppression of blood cell malignancy. Video abstract.

ALL blasts drive primary mesenchymal stromal cells to increase asparagine availability during asparaginase treatment

Mechanisms underlying the resistance of acute lymphoblastic leukemia (ALL) blasts to l-asparaginase are still incompletely known. Here we demonstrate that human primary bone marrow mesenchymal stromal cells (MSCs) successfully adapt to l-asparaginase and markedly protect leukemic blasts from the enzyme-dependent cytotoxicity through an amino acid trade-off. ALL blasts synthesize and secrete glutamine, thus increasing extracellular glutamine availability for stromal cells. In turn, MSCs use glutamine, either synthesized through glutamine synthetase (GS) or imported, to produce asparagine, which is then extruded to sustain asparagine-auxotroph leukemic cells. GS inhibition prevents mesenchymal cells adaptation to l-asparaginase, lowers glutamine secretion by ALL blasts, and markedly hinders the protection exerted by MSCs on leukemic cells. The pro-survival amino acid exchange is hindered by the inhibition or silencing of the asparagine efflux transporter SNAT5, which is induced in mesenchymal cells by ALL blasts. Consistently, primary MSCs from ALL patients express higher levels of SNAT5 (P < .05), secrete more asparagine (P < .05), and protect leukemic blasts (P < .05) better than MSCs isolated from healthy donors. In conclusion, ALL blasts arrange a pro-leukemic amino acid trade-off with bone marrow mesenchymal cells, which depends on GS and SNAT5 and promotes leukemic cell survival during l-asparaginase treatment.

Leukemia-Induced Cellular Senescence and Stemness Alterations in Mesenchymal Stem Cells Are Reversible upon Withdrawal of B-Cell Acute Lymphoblastic Leukemia Cells

Leukemic cell growth in the bone marrow (BM) induces a very stressful condition. Mesenchymal stem cells (MSC), a key component of this BM niche, are affected in several ways with unfavorable consequences on hematopoietic stem cells favoring leukemic cells. These alterations in MSC during B-cell acute lymphoblastic leukemia (B-ALL) have not been fully studied. In this work, we have compared the modifications that occur in an in vitro leukemic niche (LN) with those observed in MSC isolated from B-ALL patients. MSC in this LN niche showed features of a senescence process, i.e., altered morphology, increased senescence-associated β-Galactosidase (SA-βGAL) activity, and upregulation of p53 and p21 (without p16 expression), cell-cycle arrest, reduced clonogenicity, and some moderated changes in stemness properties. Importantly, almost all of these features were found in MSC isolated from B-ALL patients. These alterations rendered B-ALL cells susceptible to the chemotherapeutic agent dexamethasone. The senescent process seems to be transient since when leukemic cells are removed, normal MSC morphology is re-established, SA-βGAL expression is diminished, and MSC are capable of re-entering cell cycle. In addition, few cells showed low γH2AX phosphorylation that was reduced to basal levels upon cultivation. The reversibility of the senescent process in MSC must impinge important biological and clinical significance depending on cell interactions in the bone marrow at different stages of disease progression in B-ALL.

Wnt Signaling in Leukemia and Its Bone Marrow Microenvironment

Leukemia is an aggressive hematologic neoplastic disease. Therapy-resistant leukemic stem cells (LSCs) may contribute to the relapse of the disease. LSCs are thought to be protected in the leukemia microenvironment, mainly consisting of mesenchymal stem/stromal cells (MSC), endothelial cells, and osteoblasts. Canonical and noncanonical Wnt pathways play a critical role in the maintenance of normal hematopoietic stem cells (HSC) and LSCs. In this review, we summarize recent findings on the role of Wnt signaling in leukemia and its microenvironment and provide information on the currently available strategies for targeting Wnt signaling.

Aiding and Abetting: How the Tumor Microenvironment Protects Cancer from Chemotherapy

Disease recurrence following cancer therapy remains an intractable clinical problem and represents a major impediment to reducing the mortality attributable to malignant tumors. While research has traditionally focused on the cell-intrinsic mechanisms and mutations that render tumors refractory to both classical chemotherapeutics and targeted therapies, recent studies have begun to uncover myriad roles for the tumor microenvironment (TME) in modulating therapeutic efficacy. This work suggests that drug resistance is as much ecological as it is evolutionary. Specifically, cancers resident in organs throughout the body do not develop in isolation. Instead, tumor cells arise in the context of nonmalignant cellular components of a tissue. While the roles of these cell-extrinsic factors in cancer initiation and progression are well established, our understanding of the TME's influence on therapeutic outcome is in its infancy. Here, we focus on mechanisms by which neoplastic cells co-opt preexisting or treatment-induced signaling networks to survive chemotherapy.

Mesenchymal stem cells in suppression or progression of hematologic malignancy: current status and challenges

Mesenchymal stem cells (MSCs) are known for being multi-potent. However, they also possess anticancer properties, which has prompted efforts to adapt MSCs for anticancer therapies. However, MSCs have also been widely implicated in pathways that contribute to tumor growth. Numerous studies have been conducted to adapt MSCs for further clinical use; however, the results have been inconclusive, possibly due to the heterogeneity of MSC populations. Moreover, the conflicting roles of MSCs in tumor inhibition and tumor growth impede their adaptation for anticancer therapies. Antitumorigenic and protumorigenic properties of MSCs in hematologic malignancies are not as well established as they are for solid malignancies, and data comparing them are still limited. Herein the effect of MSCs on hematologic malignancies, such as leukemia and lymphoma, their mechanisms, sources of MSCs, and their effects on different types of cancer, have been discussed. This review describes how MSCs preserve both antitumorigenic and protumorigenic effects, as they tend to not only inhibit tumor growth by suppressing tumor cell proliferation but also promote tumor growth by suppressing tumor cell apoptosis. Thus clinical studies trying to adapt MSCs for anticancer therapies should consider that MSCs could actually promote hematologic cancer progression. It is necessary to take extreme care while developing MSC-based cell therapies in order to boost anticancer properties while eliminating tumor-favoring effects. This review emphasizes that research on the therapeutic applications of MSCs must consider that they exert both antitumorigenic and protumorigenic effects on hematologic malignancies.

Mimicking the Acute Myeloid Leukemia Niche for Molecular Study and Drug Screening

Bone marrow niche is a major contributing factor in leukemia development and drug resistance in acute myeloid leukemia (AML) patients. Although mimicking leukemic bone marrow niche relies on two-dimensional (2D) culture conditions, it cannot recapitulate complex bone marrow structure that causes introduction of different three-dimensional (3D) scaffolds. Simultaneously, microfluidic platform by perfusing medium culture mimic interstitial fluid flow, along with 3D scaffold would help for mimicking bone marrow microenvironment. In this study TF-1 cells were cocultured with bone marrow mesenchymal stem cells (BM-MSCs) in 2D and 3D microfluidic devices. Phenotype maintenance during cell culture and proliferation rate was assayed and confirmed by cell cycle analysis. Morphology of cells in 2D and 3D culture conditions was demonstrated by scanning electron microscopy. After these experiments, drug screening was performed by applying azacitidine and cytarabine and cytotoxicity assay and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for B cell lymphoma 2 (BCL2) were done to compare drug resistance in 2D and 3D culture conditions. Our result shows leukemic cells in 3D microfluidic device retaining their phenotype and proliferation rate was significantly higher in 3D culture condition in comparison to 2D culture condition (p < 0.05), which was confirmed by cell cycle analysis. Cytotoxicity assay also illustrated drug resistance in 3D culture condition and qRT-PCR demonstrated higher BCL2 expression in 3D microfluidic device in contrast to 2D microfluidic device (p < 0.05). On balance, mimicking bone marrow niche would help the target therapy and specify the role of niche in development of leukemia in AML patients.

Human-derived normal mesenchymal stem/stromal cells in anticancer therapies

The tumor microenvironment (TME) not only plays a pivotal role during cancer progression and metastasis, but also has profound effects on therapeutic efficacy. Stromal cells of the TME are increasingly becoming a key consideration in the development of active anticancer therapeutics. However, dispute concerning the role of stromal cells to fight cancer continues because the use of mesenchymal stem/stromal cells (MSCs) as an anticancer agent is dependent on the specific MSCs subtype, in vitro or in vivo conditions, factors secreted by MSCs, types of cancer cell lines and interactions between MSCs, cancer cells and host immune cells. In this review, we mainly focus on the role of human-derived normal MSCs in anticancer therapies. We first discuss the use of different MSCs in the therapies for various cancers. We then focus on their anticancer mechanism and clinical application.

NR2F2 regulates bone marrow-derived mesenchymal stem cell-promoted proliferation of Reh cells

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are pivotal components of the leukemic microenvironment. BM-MSCs have been previously reported to promote the proliferation of leukemic cells. To further understand the molecular mechanisms of BM-MSC-induced proliferation of leukemic cells, the present study co-cultured acute lymphoblastic leukemia (ALL) Reh cells with BM-MSCs. The current study used methods including shRNA, flow cytometry, MTT, reverse transcription-quantitative polymerase chain reaction, ELISA and western blotting. The data of the present study demonstrated that BM‑MSCs promote the proliferation of Reh cells and the NR2F2 mRNA and protein levels were elevated in BM‑MSCs following co‑culture. Additionally, it was demonstrated that shRNA knockdown of NR2F2 inhibited BM‑MSC‑induced proliferation of Reh cells. Furthermore, following downregulation of NR2F2, vascular endothelial growth factor A (VEGFA) secretion by BM‑MSCs was reduced. The present study demonstrated that NR2F2 mediates BM‑MSC‑induced proliferation of Reh cells, partially via regulation of VEGFA. Disrupting microenvironmental support by targeting NR2F2 may be a potential therapeutic strategy for ALL.

Mesenchymal stem cells promote colorectal cancer progression through AMPK/mTOR-mediated NF-κB activation

Mesenchymal stem cells (MSCs) exert a tumor-promoting effect in a variety of human cancers. This study was designed to identify the molecular mechanisms related to the tumor-promoting effect of MSCs in colorectal cancer. In vitro analysis of colorectal cancer cell lines cultured in MSC conditioned media (MSC-CM) showed that MSC-CM significantly promoted the progression of the cancer cells by enhancing cell proliferation, migration and colony formation. The tumorigenic effect of MSC-CM was attributed to altered expression of cell cycle regulatory proteins and inhibition of apoptosis. Furthermore, MSC-CM induced high level expression of a number of pluripotency factors in the cancer cells. ELISAs revealed MSC-CM contained higher levels of IL-6 and IL-8, which are associated with the progression of cancer. Moreover, MSC-CM downregulated AMPK mRNA and protein phosphorylation, but upregulated mTOR mRNA and protein phosphorylation. The NF-κB pathway was activated after addition of MSC-CM. An in vivo model in Balb/C mice confirmed the ability of MSC-CM to promote the invasion and proliferation of colorectal cancer cells. This study indicates that MSCs promote the progression of colorectal cancer via AMPK/mTOR-mediated NF-κB activation.

Visceral adipose tissue is prognostic for survival of diffuse large B cell lymphoma treated with frontline R-CHOP

The potential role of visceral adipose tissue (VAT) as a prognostic factor in patients with diffuse large B cell lymphoma (DLBCL) treated with frontline rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) immunochemotherapy was explored. Total adipose tissue and VAT were measured by analyzing positron emission tomography (PET)/computed tomography (CT) images obtained during the initial staging of patients with DLBCL. The VAT ratio was calculated as follows: VAT ratio = VAT area/total adipose tissue area. Body mass index (BMI), sex, and International Prognostic Index (IPI) were also incorporated as co-variates in the final model of multivariate Cox regression analysis for survival. A total of 156 patients with DLBCL, who were treated with frontline R-CHOP, were enrolled in our study. The median patient age was 61 years, and 81 patients were male (51.9 %). The median cycle of R-CHOP was six. The IPI risk group was a strong prognostic factor for progression-free survival (PFS) and overall survival (OS) (p < 0.001). Obese BMIs were an independent prognostic factor for PFS, but not for OS in multivariate analyses, compared to patients with normal BMIs (HR = 0.43, 95 % CI = 0.19-0.98, and p = 0.046 for PFS). A high VAT ratio (third tertile) was an independent adverse prognostic factor for PFS and OS in multivariate analyses (HR = 2.87 and 2.66, 95 % CI = 1.30-6.32 and 1.30-5.44, and p = 0.009 and 0.007 for PFS and OS, respectively). VAT ratio was an independent prognostic factor for patients with DLBCL treated with first-line R-CHOP; thus, additional large prospective studies are warranted.

MAPK signaling cascades mediate distinct glucocorticoid resistance mechanisms in pediatric leukemia

The outcome for pediatric acute lymphoblastic leukemia (ALL) patients who relapse is dismal. A hallmark of relapsed disease is acquired resistance to multiple chemotherapeutic agents, particularly glucocorticoids. In this study, we performed a genome-scale short hairpin RNA screen to identify mediators of prednisolone sensitivity in ALL cell lines. The incorporation of these data with an integrated analysis of relapse-specific genetic and epigenetic changes allowed us to identify the mitogen-activated protein kinase (MAPK) pathway as a mediator of prednisolone resistance in pediatric ALL. We show that knockdown of the specific MAPK pathway members MEK2 and MEK4 increased sensitivity to prednisolone through distinct mechanisms. MEK4 knockdown increased sensitivity specifically to prednisolone by increasing the levels of the glucocorticoid receptor. MEK2 knockdown increased sensitivity to all chemotherapy agents tested by increasing the levels of p53. Furthermore, we demonstrate that inhibition of MEK1/2 with trametinib increased sensitivity of ALL cells and primary samples to chemotherapy in vitro and in vivo. To confirm a role for MAPK signaling in patients with relapsed ALL, we measured the activation of the MEK1/2 target ERK in matched diagnosis-relapse primary samples and observed increased phosphorylated ERK levels at relapse. Furthermore, relapse samples have an enhanced response to MEK inhibition compared to matched diagnosis samples in xenograft models. Together, our data indicate that inhibition of the MAPK pathway increases chemosensitivity to glucocorticoids and possibly other agents and that the MAPK pathway is an attractive target for prevention and/or treatment of relapsed disease.