Vascular endothelial growth factor-induced migration of multiple myeloma cells is associated with beta 1 integrin- and phosphatidylinositol 3-kinase-dependent PKC alpha activation

Still high risk? A review of translocation t(14;16) in multiple myeloma

Multiple myeloma (MM) is a heterogeneous and complex disease, both in mutational biology as well as in the clinical presentation of patients. While tailored and biomarker-targeted therapy remains the direct goal for patient-centric management, existing therapies in MM remain largely uniform. Translocation t(14;16) is a rare primary genetic event found in less than 5% of patients with newly diagnosed MM. Here, we present an overview of the biology of t(14;16), epidemiology, clinical presentation, prognostic impact, and discuss the future clinical and therapeutic strategies for targeting this rare yet high-risk group in MM to optimize patient outcomes.

MiR-34c-5p Inhibition Affects Bax/Bcl2 Expression and Reverses Bortezomib Resistance in Multiple Myeloma Cells

Developing resistance to anticancer drugs complicates the clinical treatment of multiple myeloma patients. Previous studies revealed a link between the unfolded protein response (UPR) and miRNAs with acquired drug resistance. This study aimed to determine the expression profile of XBP1, hsa-miR-34c-5p, hsa-miR-214, and hsa-miR-30c-2* in resistant and sensitive multiple myeloma cell lines to a proteasome inhibitor, bortezomib. After establishing bortezomib-resistant cells, the expression level of XBP1, hsa-miR-214, hsa-miR-34c-5p, and hsa-miR-30c-2* in both cell lines were assessed by qRT-PCR. Hsa-miR-34c-5p was suppressed to study its effect on the expression profile of Bax/Bcl-2. Statistical analysis was done by t-test in two clinically resistant and sensitive cells to bortezomib. MTT assay confirmed the creation of the resistant cell line. The qRT-PCR screening showed a significant difference between XBP1 and miR-34c-5p levels in resistant and sensitive cells. Following hsa-miR-34c-5p blockage, while Bax was overexpressed, Bcl-2 expression was reduced in the resistant cell line, overcoming cells resistant to bortezomib. Our findings demonstrate miR-34c-5p is differentially expressed between bortezomib-sensitive and -resistant MM cells. Inhibiting miR-34c-5p re-sensitized resistant cells to bortezomib by modulating Bax/Bcl-2 expression, suggesting this miRNA regulates apoptosis and drug resistance and may be a promising therapeutic target for overcoming proteasome inhibitor resistance in MM.

Computational modeling of multiple myeloma interactions with resident bone marrow cells

The interaction of multiple myeloma with bone marrow resident cells plays a key role in tumor progression and the development of drug resistance. The tumor cell response involves contact-mediated and paracrine interactions. The heterogeneity of myeloma cells and bone marrow cells makes it difficult to reproduce this environment in in-vitro experiments. The use of in-silico established tools can help to understand these complex problems. In this article, we present a computational model based on the finite element method to define the interactions of multiple myeloma cells with resident bone marrow cells. This model includes cell migration, which is controlled by stress-strain equilibrium, and cell processes such as proliferation, differentiation, and apoptosis. A series of computational experiments were performed to validate the proposed model. Cell proliferation by the growth factor IGF-1 is studied for different concentrations ranging from 0-10 ng/mL. Cell motility is studied for different concentrations of VEGF and fibronectin in the range of 0-100 ng/mL. Finally, cells were simulated under a combination of IGF-1 and VEGF stimuli whose concentrations are considered to be dependent on the cancer-associated fibroblasts in the extracellular matrix. Results show a good agreement with previous in-vitro results. Multiple myeloma growth and migration are shown to correlate linearly to the IGF-1 stimuli. These stimuli are coupled with the mechanical environment, which also improves cell growth. Moreover, cell migration depends on the fiber and VEGF concentration in the extracellular matrix. Finally, our computational model shows myeloma cells trigger mesenchymal stem cells to differentiate into cancer-associated fibroblasts, in a dose-dependent manner.

Bench to Bedside: New Therapeutic Approaches with Extracellular Vesicles and Engineered Biomaterials for Targeting Therapeutic Resistance of Cancer Stem Cells

Cancer has recently been the second leading cause of death worldwide, trailing only cardiovascular disease. Cancer stem cells (CSCs), represented as tumor-initiating cells (TICs), are mainly liable for chemoresistance and disease relapse due to their self-renewal capability and differentiating capacity into different types of tumor cells. The intricate molecular mechanism is necessary to elucidate CSC's chemoresistance properties and cancer recurrence. Establishing efficient strategies for CSC maintenance and enrichment is essential to elucidate the mechanisms and properties of CSCs and CSC-related therapeutic measures. Current approaches are insufficient to mimic the in vivo chemical and physical conditions for the maintenance and growth of CSC and yield unreliable research results. Biomaterials are now widely used for simulating the bone marrow microenvironment. Biomaterial-based three-dimensional (3D) approaches for the enrichment of CSC provide an excellent promise for future drug discovery and elucidation of molecular mechanisms. In the future, the biomaterial-based model will contribute to a more operative and predictive CSC model for cancer therapy. Design strategies for materials, physicochemical cues, and morphology will offer a new direction for future modification and new methods for studying the CSC microenvironment and its chemoresistance property. This review highlights the critical roles of the microenvironmental cues that regulate CSC function and endow them with drug resistance properties. This review also explores the latest advancement and challenges in biomaterial-based scaffold structure for therapeutic approaches against CSC chemoresistance. Since the recent entry of extracellular vesicles (EVs), cell-derived nanostructures, have opened new avenues of investigation into this field, which, together with other more conventionally studied signaling pathways, play an important role in cell-to-cell communication. Thus, this review further explores the subject of EVs in-depth. This review also discusses possible future biomaterial and biomaterial-EV-based models that could be used to study the tumor microenvironment (TME) and will provide possible therapeutic approaches. Finally, this review concludes with potential perspectives and conclusions in this area.

SARS-CoV-2 infection associated with monoclonal gammopathy. A case report based on the study of minimally invasive ultrasound-guided autopsy

Coronavirus disease-2019 (COVID-19) is a global public health emergency with numerous clinical facets, including acute kidney injury and acute cerebrovascular disease. Further knowledge of its various pathogenic mechanisms is essential, including coagulation disorders. Monoclonal gammopathy is characterized by the overproduction of a monoclonal immunoglobulin caused by clonal proliferation. Using a postmortem study of ultrasound-guided percutaneous core biopsies, the aim of this report is to present our observations on the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection pathology associated with monoclonal gammopathy. The clinical presentation was acute renal failure. Pathological findings revealed kappa light chain cast nephropathy. SARS-CoV-2 immunohistochemistry was positive in some renal tubular cells. Another notable finding was the presence of a high density of alveolar megakaryocytes, which probably explained the final outcome (acute cerebrovascular disease). Immunohistochemical study for SARS-CoV-2 does not verify the pathogenic effect of the virus and thus its contribution to the acute kidney injury.

The Non-receptor Tyrosine Kinase Pyk2 in Brain Function and Neurological and Psychiatric Diseases

Pyk2 is a non-receptor tyrosine kinase highly enriched in forebrain neurons. Pyk2 is closely related to focal adhesion kinase (FAK), which plays an important role in sensing cell contacts with extracellular matrix and other extracellular signals controlling adhesion and survival. Pyk2 shares some of FAK’s characteristics including recruitment of Src-family kinases after autophosphorylation, scaffolding by interacting with multiple partners, and activation of downstream signaling pathways. Pyk2, however, has the unique property to respond to increases in intracellular free Ca²⁺, which triggers its autophosphorylation following stimulation of various receptors including glutamate NMDA receptors. Pyk2 is dephosphorylated by the striatal-enriched phosphatase (STEP) that is highly expressed in the same neuronal populations. Pyk2 localization in neurons is dynamic, and altered following stimulation, with post-synaptic and nuclear enrichment. As a signaling protein Pyk2 is involved in multiple pathways resulting in sometimes opposing functions depending on experimental models. Thus Pyk2 has a dual role on neurites and dendritic spines. With Src family kinases Pyk2 participates in postsynaptic regulations including of NMDA receptors and is necessary for specific types of synaptic plasticity and spatial memory tasks. The diverse functions of Pyk2 are also illustrated by its role in pathology. Pyk2 is activated following epileptic seizures or ischemia-reperfusion and may contribute to the consequences of these insults whereas Pyk2 deficit may contribute to the hippocampal phenotype of Huntington’s disease. Pyk2 gene, PTK2B, is associated with the risk for late-onset Alzheimer’s disease. Studies of underlying mechanisms indicate a complex contribution with involvement in amyloid toxicity and tauopathy, combined with possible functional deficits in neurons and contribution in microglia. A role of Pyk2 has also been proposed in stress-induced depression and cocaine addiction. Pyk2 is also important for the mobility of astrocytes and glioblastoma cells. The implication of Pyk2 in various pathological conditions supports its potential interest for therapeutic interventions. This is possible through molecules inhibiting its activity or increasing it through inhibition of STEP or other means, depending on a precise evaluation of the balance between positive and negative consequences of Pyk2 actions.

Malignant Pleural Mesothelioma Interactome with 364 Novel Protein-Protein Interactions

Malignant pleural mesothelioma (MPM) is an aggressive cancer affecting the outer lining of the lung, with a median survival of less than one year. We constructed an 'MPM interactome' with over 300 computationally predicted protein-protein interactions (PPIs) and over 2400 known PPIs of 62 literature-curated genes whose activity affects MPM. Known PPIs of the 62 MPM associated genes were derived from Biological General Repository for Interaction Datasets (BioGRID) and Human Protein Reference Database (HPRD). Novel PPIs were predicted by applying the HiPPIP algorithm, which computes features of protein pairs such as cellular localization, molecular function, biological process membership, genomic location of the gene, and gene expression in microarray experiments, and classifies the pairwise features as interacting or non-interacting based on a random forest model. We validated five novel predicted PPIs experimentally. The interactome is significantly enriched with genes differentially ex-pressed in MPM tumors compared with normal pleura and with other thoracic tumors, genes whose high expression has been correlated with unfavorable prognosis in lung cancer, genes differentially expressed on crocidolite exposure, and exosome-derived proteins identified from malignant mesothelioma cell lines. 28 of the interactors of MPM proteins are targets of 147 U.S. Food and Drug Administration (FDA)-approved drugs. By comparing disease-associated versus drug-induced differential expression profiles, we identified five potentially repurposable drugs, namely cabazitaxel, primaquine, pyrimethamine, trimethoprim and gliclazide. Preclinical studies may be con-ducted in vitro to validate these computational results. Interactome analysis of disease-associated genes is a powerful approach with high translational impact. It shows how MPM-associated genes identified by various high throughput studies are functionally linked, leading to clinically translatable results such as repurposed drugs. The PPIs are made available on a webserver with interactive user interface, visualization and advanced search capabilities.

Treatment Strategies Considering Micro-Environment and Clonal Evolution in Multiple Myeloma

Simple Summary

Multiple myeloma is an uncurable hematological malignancy, although the prognosis of myeloma patients is getting better using proteasome inhibitors (PIs), immune modulatory drugs (IMiDs), monoclonal antibodies (MoAbs), and cytotoxic agents. Drug resistance makes myeloma difficult to treat and it can be subdivided into two broad categories: de novo and acquired. De novo drug resistance is associated with the bone marrow microenvironment including bone marrow stromal cells, the vascular niche and endosteal niche. Acquired drug resistance is related to clonal evolution and non-genetic diversity. The initial treatment plays the most important role considering de novo and acquired drug resistance and should contain PIs, IMIDs, MoAbs, and autologous stem cell transplantation because these treatments improve the bone marrow microenvironment and might prevent clonal evolution via sustained deep response including minimal residual disease negativity.

Abstract

Multiple myeloma is an uncurable hematological malignancy because of obtained drug resistance. Microenvironment and clonal evolution induce myeloma cells to develop de novo and acquired drug resistance, respectively. Cell adhesion-mediated drug resistance, which is induced by the interaction between myeloma and bone marrow stromal cells, and soluble factor-mediated drug resistance, which is induced by cytokines and growth factors, are two types of de novo drug resistance. The microenvironment, including conditions such as hypoxia, vascular and endosteal niches, contributes toward de novo drug resistance. Clonal evolution was associated with acquired drug resistance and classified as branching, linear, and neutral evolutions. The branching evolution is dependent on the microenvironment and escape of immunological surveillance while the linear and neutral evolution is independent of the microenvironment and associated with aggressive recurrence and poor prognosis. Proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), monoclonal antibody agents (MoAbs), and autologous stem cell transplantation (ASCT) have improved prognosis of myeloma via improvement of the microenvironment. The initial treatment plays the most important role considering de novo and acquired drug resistance and should contain PIs, IMIDs, MoAb and ASCT. This review summarizes the role of anti-myeloma agents for microenvironment and clonal evolution and treatment strategies to overcome drug resistance.

Signaling Pathway Mediating Myeloma Cell Growth and Survival

Simple Summary

The bone marrow (BM) microenvironment plays a crucial role in pathogenesis of multiple myeloma (MM), and delineation of the intracellular signaling pathways activated in the BM microenvironment in MM cells is essential to develop novel therapeutic strategies to improve patient outcome.

Abstract

The multiple myeloma (MM) bone marrow (BM) microenvironment consists of different types of accessory cells. Both soluble factors (i.e., cytokines) secreted from these cells and adhesion of MM cells to these cells play crucial roles in activation of intracellular signaling pathways mediating MM cell growth, survival, migration, and drug resistance. Importantly, there is crosstalk between the signaling pathways, increasing the complexity of signal transduction networks in MM cells in the BM microenvironment, highlighting the requirement for combination treatment strategies to blocking multiple signaling pathways.

Management of acute spinal cord compression in multiple myeloma

Spinal cord compression (SCC) is a devastating complication of multiple myeloma and has the potential to cause loss of neurological function. The common symptoms of SCC are back pain, motor weakness, and sensory change. Once diagnosed, the patient should be managed as soon as possible to prevent permanent loss of neurological function. Currently, there have been a number of studies describing the mechanism and management experience of SCC in patients with myeloma. The clinical features, diagnostic strategies, and the roles of different therapeutic options are herein reviewed.

Contribution of the bone marrow stromal cells in mediating drug resistance in hematopoietic tumors

The bone marrow microenvironment (BMM) provides input via production of cytokines, chemokines, extracellular matrixes in the context of lower oxygen levels that influences self-renewal, survival, differentiation, progression, and therapeutic resistance of multiple myeloma and leukemic cells. Within the context of the BMM, tumor cells are supported by osteoblasts, bone marrow stromal cells (BMSCs), fibroblasts, myeloid cells, endothelial cells and blood vessels, as well as extracellular matrix (ECM) that contribute to tumor progression. Environmental mediated-drug resistance (EM-DR) contains cell adhesion-mediated drug resistance (CAM-DR) and soluble factor-mediated drug resistance (SM-DR) that contributes to de novo drug resistance. In this review, we focus on the crosstalk between the BMM and tumor cells as well as mechanisms underlying the BMM contributing to drug resistance in hematologic malignancies.

Role of the Bone Marrow Milieu in Multiple Myeloma Progression and Therapeutic Resistance

Multiple myeloma (MM) is a cancer of the plasma cells within the bone marrow (BM). Studies have shown that the cellular and noncellular components of the BM milieu, such as cytokines and exosomes, play an integral role in MM pathogenesis and progression by mediating drug resistance and inducing MM proliferation. Moreover, the BM microenvironment of patients with MM facilitates cancer tolerance and immune evasion through the expansion of regulatory immune cells, inhibition of antitumor effector cells, and disruption of the antigen presentation machinery. These are of special relevance, especially in the current era of cancer immunotherapy. An improved understanding of the supportive role of the MM BM microenvironment will allow for the development of future therapies targeting MM in the context of the BM milieu to elicit deeper and more durable responses. In the present review, we have discussed our current understanding of the role of the BM microenvironment in MM progression and resistance to therapy and discuss novel potential approaches to alter its pro-MM function.

miR-125b Upregulates miR-34a and Sequentially Activates Stress Adaption and Cell Death Mechanisms in Multiple Myeloma

miR-125b, ubiquitously expressed and frequently dysregulated in several tumors, has gained special interest in the field of cancer research, displaying either oncogenic or oncosuppressor potential based on tumor type. We have previously demonstrated its tumor-suppressive role in multiple myeloma (MM), but the analysis of molecular mechanisms needs additional investigation. The purpose of this study was to explore the effects of miR-125b and its chemically modified analogs in modulating cell viability and cancer-associated molecular pathways, also focusing on the functional aspects of stress adaptation (autophagy and senescence), as well as programmed cell death (apoptosis). Based on the well-known low microRNA (miRNA) stability in therapeutic application, we designed chemically modified miR-125b mimics, laying the bases for their subsequent investigation in in vivo models. Our study clearly confirmed an oncosuppressive function depending on the repression of multiple targets, and it allowed the identification, for the first time, of miR-125b-dependent miR-34a stimulation as a possible consequence of the inhibitory role on the interleukin-6 receptor (IL-6R)/signal transducer and activator of transcription 3 (STAT3)/miR-34a feedback loop. Moreover, we identified a pattern of miR-125b-co-regulated miRNAs, shedding light on possible new players of anti-MM activity. Finally, functional studies also revealed a sequential activation of senescence, autophagy, and apoptosis, thus indicating, for the first two processes, an early cytoprotective and inhibitory role from apoptosis activation.

Inflammatory and Anti-Inflammatory Equilibrium, Proliferative and Antiproliferative Balance: The Role of Cytokines in Multiple Myeloma

Multiple myeloma (MM) is typically exemplified by a desynchronized cytokine system with increased levels of inflammatory cytokines. We focused on the contrast between inflammatory and anti-inflammatory systems by assessing the role of cytokines and their influence on MM. The aim of this review is to summarize the available information to date concerning this equilibrium to provide an overview of the research exploring the roles of serum cytokines in MM. However, the association between MM and inflammatory cytokines appears to be inadequate, and other functions, such as pro-proliferative or antiproliferative effects, can assume the role of cytokines in the genesis and progression of MM. It is possible that inflammation, when guided by cancer-specific Th1 cells, may inhibit tumour onset and progression. In a Th1 microenvironment, proinflammatory cytokines (e.g., IL-6 and IL-1) may contribute to tumour eradication by attracting leucocytes from the circulation and by increasing CD4 ⁺ T cell activity. Hence, caution should be used when considering therapies that target factors with pro- or anti-inflammatory activity. Drugs that may reduce the tumour-suppressive Th1-driven inflammatory immune response should be avoided. A better understanding of the relationship between inflammation and myeloma will ensure more effective therapeutic interventions.

Arg-Leu-Tyr-Glu tetrapeptide inhibits tumor progression by suppressing angiogenesis and vascular permeability via VEGF receptor-2 antagonism

The tetrapeptide Arg-Leu-Tyr-Glu (RLYE) is known to inhibit vascular endothelial growth factor-A (VEGF-A)-induced angiogenesis in vitro. Herein, we examined its underlying mechanism and antitumor activity associated with vascular remodeling. RLYE inhibited VEGF-A-induced angiogenesis in a mouse model and suppressed VEGF-A-induced angiogenic signal cascades in human endothelial cells. However, RLYE showed no inhibitory effect on VEGF-A-induced proliferation and migration of multiple myeloma cells expressing VEGF receptor (VEGFR)-1, but not VEGFR-2. In addition, RLYE showed no inhibitory effect on angiogenic activities induced by VEGF-B, basic fibroblast growth factor, epithermal growth factor, sphingosine-1-phosphate, and placental growth factor. RLYE bound specifically to VEGFR-2 at the VEGF-A binding site, thereby blocking VEGF-A-VEGFR-2 binding and VEGF-A-induced VEGFR-2 internalization. The RLYE peptide inhibited tumor growth and metastasis via suppression of tumor angiogenesis in tumor-bearing mice. Moreover, RLYE showed a synergistic effect of the cytotoxic agent irinotecan on tumor cell apoptosis and tumor progression via tumor vessel normalization due to stabilization of VE-cadherin-mediated adherens junction, improvement of pericyte coverage, and inhibition of vascular leakage in tumors. Our results suggest that RLYE can be used as an antiangiogenic and tumor blood vessel remodeling agent for inhibition of tumor growth and metastasis by antagonizing VEGFR-2, with the synergistic anti-cancer effect via enhancement of drug delivery and therapeutic efficacy.

SIGMAR1 Regulates Membrane Electrical Activity in Response to Extracellular Matrix Stimulation to Drive Cancer Cell Invasiveness

The sigma 1 receptor (Sig1R) is a stress-activated chaperone that regulates ion channels and is associated with pathologic conditions, such as stroke, neurodegenerative diseases, and addiction. Aberrant expression levels of ion channels and Sig1R have been detected in tumors and cancer cells, such as myeloid leukemia and colorectal cancer, but the link between ion channel regulation and Sig1R overexpression during malignancy has not been established. In this study, we found that Sig1R dynamically controls the membrane expression of the human voltage-dependent K(+) channel human ether-à-go-go-related gene (hERG) in myeloid leukemia and colorectal cancer cell lines. Sig1R promoted the formation of hERG/β1-integrin signaling complexes upon extracellular matrix stimulation, triggering the activation of the PI3K/AKT pathway. Consequently, the presence of Sig1R in cancer cells increased motility and VEGF secretion. In vivo, Sig1R expression enhanced the aggressiveness of tumor cells by potentiating invasion and angiogenesis, leading to poor survival. Collectively, our findings highlight a novel function for Sig1R in mediating cross-talk between cancer cells and their microenvironment, thus driving oncogenesis by shaping cellular electrical activity in response to extracellular signals. Given the involvement of ion channels in promoting several hallmarks of cancer, our study also offers a potential strategy to therapeutically target ion channel function through Sig1R inhibition.

Mechanisms of Drug Resistance in Relapse and Refractory Multiple Myeloma

Multiple myeloma (MM) is a hematological malignancy that remains incurable because most patients eventually relapse or become refractory to current treatments. Although the treatments have improved, the major problem in MM is resistance to therapy. Clonal evolution of MM cells and bone marrow microenvironment changes contribute to drug resistance. Some mechanisms affect both MM cells and microenvironment, including the up- and downregulation of microRNAs and programmed death factor 1 (PD-1)/PD-L1 interaction. Here, we review the pathogenesis of MM cells and bone marrow microenvironment and highlight possible drug resistance mechanisms. We also review a potential molecular targeting treatment and immunotherapy for patients with refractory or relapse MM.

PKCα promotes the mesenchymal to amoeboid transition and increases cancer cell invasiveness

Background

The local invasion of tumor cells into the surrounding tissue is the first and most critical step of the metastatic cascade. Cells can invade either collectively, or individually. Individual cancer cell invasion can occur in the mesenchymal or amoeboid mode, which are mutually interchangeable. This plasticity of individual cancer cell invasiveness may represent an escape mechanism for invading cancer cells from anti-metastatic treatment.

Methods

To identify new signaling proteins involved in the plasticity of cancer cell invasiveness, we performed proteomic analysis of the amoeboid to mesenchymal transition with A375m2 melanoma cells in a 3D Matrigel matrix.

Results

In this screen we identified PKCα as an important protein for the maintenance of amoeboid morphology. We found that the activation of PKCα resulted in the mesenchymal-amoeboid transition of mesenchymal K2 and MDA-MB-231 cell lines. Consistently, PKCα inhibition led to the amoeboid-mesenchymal transition of amoeboid A375m2 cells. Next, we showed that PKCα inhibition resulted in a considerable decrease in the invading abilities of all analyzed cancer cell lines.

Conclusions

Our results suggest that PKCα is an important protein for maintenance of the amoeboid morphology of cancer cells, and that downregulation of PKCα results in the amoeboid to mesenchymal transition. Our data also suggest that PKCα is important for both mesenchymal and amoeboid invasiveness, making it an attractive target for anti-metastatic therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1347-1) contains supplementary material, which is available to authorized users.

Recent advances in antimultiple myeloma drug development

Multiple myeloma (MM) is the second most common hematological malignancy and is characterized by the aberrant proliferation of terminally differentiated plasma B cells with impairment in apoptosis capacity. Particularly, osteolytic bone diseases and renal failure resulting from hyperparaproteinemia and hypercalcemia have been the major serious sequelae that are inextricably linked with MM tumor progression. Despite the introduction of new treatment regimens, problematic neuropathy, thrombocytopenia, drug resistance and high MM relapse rates continue to plague the current therapies. New chemical agents are in development on the basis of understanding several signaling pathways and molecular mechanisms like tumor necrosis factor-α, proteasome, PI3K and MARKs. This review focuses on the most recent patents and clinical trials in the development of new medicine for the treatment of multiple myeloma. Furthermore, the important signaling pathways involved in the proliferation, survival and apoptosis of myeloma cells will be discussed.

The Analysis of the Relationship between Multiple Myeloma Cells and Their Microenvironment

The bone marrow microenvironment plays a key role in the stimulation of growth and survival of multiple myeloma (MM) cells. We investigated whether membrane microfragments (MFBs) exert a stimulatory effect on mesenchymal stem cell (MSC) gene expression or differentiation. MSCs from patients with multiple myeloma (MMBM-MSCs) proliferated at a slower rate than MSCs from healthy volunteers (BM-MSCs), and fewer MMBM-MSCs adhered to the substrate as compared to BM-MSCs. Phenotypic analysis revealed that MMBM-MSCs and BM-MSCs differed significantly in terms of their CD166 and CXCR4 expressions. In conclusion, our comparative analysis of mesenchymal cells from MM patients and healthy volunteers revealed differences in the genetic and phenotypic profiles of these two populations, their potential for osteodifferentiation, and expression of surface antigens. Moreover, we showed that membrane MFBs may alter the genetic profile of MSCs, leading to disorders of their osteodifferentiation, and interact with the WNT pathway via presentation of the DKK-1 protein.

Simultaneous Inhibition of CXCR4 and VLA-4 Exhibits Combinatorial Effect in Overcoming Stroma-Mediated Chemotherapy Resistance in Mantle Cell Lymphoma Cells

There is growing evidence that crosstalk between mantle cell lymphoma (MCL) cells and stromal microenvironments, such as bone marrow and secondary lymphoid tissues, promotes tumor progression by enhancing survival and growth as well as drug resistance of MCL cells. Recent advances in the understanding of lymphoma microenvironment have led to the identification of crucial factors involved in the crosstalk and subsequent generation of their targeted agents. In the present study, we evaluated the combinatory effect of blocking antibodies (Ab) targeting CXCR4 and VLA-4, both of which were known to play significant roles in the induction of environment-mediated drug resistance (EMDR) in MCL cell line, Jeko-1. Simultaneous treatment with anti-CXCR4 and anti-VLA-4 Ab not only reduced the migration of Jeko-1 cells into the protective stromal cells, but also enhanced sensitivity of Jeko-1 to a chemotherapeutic agent to a greater degree than with either Ab alone. These combinatorial effects were associated with decreased phosphorylation of ERK1/2, AKT and NF-κB. Importantly, drug resistance could not be overcome once the adhesion of Jeko-1 to the stromal occurred despite the combined use of Abs, suggesting that the efforts to mitigate migration of MCLs should be attempted as much as possible. Our results provide a basis for a future development of therapeutic strategies targeting both CXCR4 and VLA-4, such as Ab combinations or bispecific antibodies, to improve treatment outcomes of MCL with grave prognosis.

Intracellular TCR-signaling pathway: novel markers for lymphoma diagnosis and potential therapeutic targets

Despite the immunologic functions of T-cell receptor signaling molecules being extensively investigated, their potential as immunohistochemical markers has been poorly explored. With this background, we evaluated the expression of 5 intracellular proteins-GADS, DOK2, SKAP55, ITK, and PKCα-involved in T-cell receptor signaling in normal and neoplastic hematologic tissue samples, using antibodies raised against fixation-resistant epitopes of the 5 molecules. All 5 antibodies were associated with normal T-cell differentiation. GADS, DOK2, SKAP55, and ITK turned out to be T-cell lineage-specific markers in the setting of lymphoid and myeloid precursor neoplasms but showed differential expression in peripheral T-cell lymphoma (PTCL) subtypes, being detected in PTCL/not otherwise specified (NOS) and angioimmunoblastic T-cell lymphoma but negative in anaplastic large cell lymphoma (ALCL). Peripheral B-cell lymphomas were consistently negative for ITK, with occasional cases showing expression of DOK2 and SKAP55, and a proportion (47%) of hairy cell leukemias were GADS. Notably, PKCα highlighted a defective antigen in both PTCL/NOS (6%) and angioimmunoblastic T-cell lymphoma (10%), mostly negative in ALCL, and was aberrantly expressed in classical Hodgkin lymphoma (65%), Burkitt lymphoma (48%), and plasma cell myeloma (48%). In conclusion, all five molecules evaluated play a role in T-cell differentiation in normal and neoplastic tissues. They can be applied confidently to routine sections contributing primarily to assignment of T-lineage differentiation in the setting of hematopoietic precursor neoplasms (GADS/DOK2/SKAP55/ITK) and for the differential diagnosis between ALCL and PTCL/NOS (GADS/DOK2/SKAP55/ITK) or classical Hodgkin lymphoma (PKCα). Finally, association with specific tumor subtypes may have therapeutic potential.

A multicenter phase II study of single-agent enzastaurin in previously treated multiple myeloma

Enzastaurin is an oral serine/threonine kinase inhibitor of the protein kinase C (PKC) and phosphatidylinositol 3 (PI3) kinase/Akt pathways that induces apoptosis in multiple myeloma (MM) cell lines in a caspase-independent manner. A phase II study was conducted to assess response rate, time to progression (TTP), safety and biomarker association with clinical outcomes after monotherapy with the PKC inhibitor enzastaurin in previously treated patients with MM. Eligible patients (n = 14) were treated with enzastaurin 250 mg twice daily after receiving loading doses on day 1. One minimal response was observed. The median TTP was 5.11 months. There were two grade 3 adverse events, anemia and prolonged QTc interval, and no grade 4 adverse events. Single-agent enzastaurin was well tolerated but not effective in this heavily pretreated population with MM.

The detection of risk pathways, regulated by miRNAs, via the integration of sample-matched miRNA-mRNA profiles and pathway structure

The use of genome-wide, sample-matched miRNA (miRNAs)-mRNA expression data provides a powerful tool for the investigation of miRNAs and genes involved in diseases. The identification of miRNA-regulated pathways has been crucial for analysis of the role of miRNAs. However, the classical identification method fails to consider the structural information of pathways and the regulation of miRNAs simultaneously. We proposed a method that simultaneously integrated the change in gene expression and structural information in order to identify pathways. Our method used fold changes in miRNAs and gene products, along with the quantification of the regulatory effect on target genes, to measure the change in gene expression. Topological characteristics were investigated to measure the influence of gene products on entire pathways. Through the analysis of multiple myeloma and prostate cancer expression data, our method was proven to be effective and reliable in identifying disease risk pathways that are regulated by miRNAs. Further analysis showed that the structure of a pathway plays a crucial role in the recognition of the pathway as a factor in disease risk.

MET dysregulation is a hallmark of aggressive disease in multiple myeloma patients

Abnormal activation of MET/HGF (Hepatocyte Growth Factor) pathway has been described in several tumours and increased HGF plasmatic levels have been detected in patients with aggressive multiple myeloma (MM). MET and HGF mRNA expression was investigated in 105 samples of purified plasma cells derived from newly diagnosed MM patients treated with bortezomib-based induction therapy. Gene expression was compared with response to therapy and clinical outcome. MET gene copy number was also evaluated. MET mRNA expression was higher in CD138(+) than in CD138(-) cells (median 76·90 vs. 11·24; P = 0·0009). Low MET mRNA expression characterized patients with better response (complete response or very good partial response) compared to other patients (median 56·10 vs. 134·83; P = 0·0006). After a median follow-up of 50 months, patients with high MET mRNA expression displayed a worse progression-free survival (PFS; P = 0·0029) and overall survival (OS; P = 0·0023) compared to those with low MET mRNA levels. Patients with both high MET mRNA expression and high β2-microglobulin level (>5·5 mg/l) had further worse median PFS (P < 0·0001) and OS (P < 0·0001). Patients carrying 4 MET gene copies (8 out of 82, 9·8%) also had a short PFS. High MET mRNA expression identifies patients with dismal PFS and OS and the combination with high β2-microglobulin further characterizes patients with worse outcome.

Multiple myeloma : recent progress in diagnosis and treatment

Multiple myeloma (MM) has been the most intractable hematological disease for many years. Recently, basic and clinical research has advanced remarkably and a new therapeutic strategy has been established. The introduction of high-dose melphalan with autologous stem-cell transplantation and the availability of molecular-targeted novel agents such as immunomodulatory drugs and proteasome inhibitors have dramatically changed the treatment strategies for MM. Achievement of a high response rate resulted in the extension of overall survival, but further research and the development of more multimodality therapeutic approaches is warranted to cure this disease.

In vitro and in vivo antitumor activity of a novel alkylating agent, melphalan-flufenamide, against multiple myeloma cells

PURPOSE

The alkylating agent melphalan prolongs survival in patients with multiple myeloma; however, it is associated with toxicities and development of drug-resistance. Here, we evaluated the efficacy of melphalan-flufenamide (mel-flufen), a novel dipeptide prodrug of melphalan in multiple myeloma.

EXPERIMENTAL DESIGN

Multiple myeloma cell lines, primary patient cells, and the human multiple myeloma xenograft animal model were used to study the antitumor activity of mel-flufen.

RESULTS

Low doses of mel-flufen trigger more rapid and higher intracellular concentrations of melphalan in multiple myeloma cells than are achievable by free melphalan. Cytotoxicity analysis showed significantly lower IC50 of mel-flufen than melphalan in multiple myeloma cells. Importantly, mel-flufen induces apoptosis even in melphalan- and bortezomib-resistant multiple myeloma cells. Mechanistic studies show that siRNA knockdown of aminopeptidase N, a key enzyme mediating intracellular conversion of mel-flufen to melphalan, attenuates anti-multiple myeloma activity of mel-flufen. Furthermore, mel-flufen-induced apoptosis was associated with: (i) activation of caspases and PARP cleavage; (ii) reactive oxygen species generation; (iii) mitochondrial dysfunction and release of cytochrome c; and (iv) induction of DNA damage. Moreover, mel-flufen inhibits multiple myeloma cell migration and tumor-associated angiogenesis. Human multiple myeloma xenograft studies showed a more potent inhibition of tumor growth in mice treated with mel-flufen than mice receiving equimolar doses of melphalan. Finally, combining mel-flufen with lenalidomide, bortezomib, or dexamethasone triggers synergistic anti-multiple myeloma activity.

CONCLUSION

Our preclinical study supports clinical evaluation of mel-flufen to enhance therapeutic potential of melphalan, overcome drug-resistance, and improve multiple myeloma patient outcome.

HGF and IGF-1 synergize with SDF-1α in promoting migration of myeloma cells by cooperative activation of p21-activated kinase

Stromal-derived factor (SDF)-1α, insulin-like growth factor (IGF)-1 and hepatocyte growth factor (HGF) are potent mediators of cell migration. We studied the effect of combinations of these cytokines on the migration of myeloma cells. When SDF-1α was combined with either HGF or IGF-1, we found a striking synergy in the cytokines' ability to guide cells across a transwell membrane. Between HGF and IGF-1 there was no cooperativity. However, the effects of HGF and IGF-1 were not redundant. HGF and SDF-1 caused concentration gradient-directed migration, as opposed to IGF-1, which apparently caused randomly directed cell movement. The SDF-1α-driven migration of JJN-3 cells, a myeloma cell line secreting large amounts of HGF, was reduced when JJN-3 cells were given an inhibitor of the HGF receptor, demonstrating a cooperative activity between autocrine HGF and exogenous SDF-1α. There was a clear positive correlation between the degree of cytokine-induced migration and phosphorylation of p21-activated kinase (PAK) both in primary myeloma cells and in cell lines including INA-6 and IH-1. Downregulation of PAK with small interfering RNA in INA-6 cells resulted in decreased cytokine-driven migration. This study shows synergy between SDF-1α and HGF/IGF-1 in inducing migration of myeloma cells, yet each cytokine has distinct properties in the way it regulates cell migration. These findings are likely to be of clinical relevance because multiple myeloma cells are located in an environment containing HGF and IGF-1 and are exposed to an SDF-1α gradient between the bone marrow and peripheral blood.

Elevated serum angiotensin converting enzyme levels as a reflection of bone marrow renin-angiotensin system activation in multiple myeloma

INTRODUCTION

Angiotensin converting enzyme (ACE) is a circulating enzyme that participates in the body's renin-angiotensin system (RAS) and is localized on the endothelial cell surface in the lung and other vascular beds. It catalyses the conversion of decapeptide angiotensin I to octapeptide angiotensin II. In the present study, we aimed to analyse the possible relationship between the levels of ACE in the context of RAS in multiple myeloma (MM) pathogenesis.

MATERIALS AND METHODS

The study was conducted on 25 MM patients (13 males, 12 females; median age 66 years, range 47-88) and 20 healthy controls. The clinical features of MM patients including demographics and laboratory findings were summarized. Serum ACE levels were measured by using commercially available kits.

RESULTS

The serum ACE levels of MM patients and controls were 32.60±20.26 and 15.35±6.47 respectively. Serum ACE levels were significantly higher in MM patients compared with control groups (p<0.001).

CONCLUSIONS

Being an important component of RAS, circulating ACE might be associated with clonal proliferation of malignant plasma cells in the bone marrow microenvironment. Identification of the pathobiological activity of the local RAS in MM would enlighten the biologic basis and clinical management of haematologic disorders.

Cell Trafficking in Multiple Myeloma

Multiple myeloma (MM) is an incurable cancer of terminally differentiated plasma cells (PC) and represents the second most frequent hematologic malignancy in the western world. MM cells localize preferentially to the bone marrow where they interact closely with bone marrow stroma cells (BMSC) and extracellular matrix (ECM) proteins in a reciprocal pro-survival loop. Such a bone marrow niche guarantees a survival advantage for MM cells and has a crucial role in mediating drug resistance to chemotherapy agents. As the name suggests, hallmark characteristic of MM is the ability to localize in multiple, distant bone sites causing disruption of the normal bone architecture and impairment of normal hematopoiesis. The pathogenic mechanisms of MM rely then not only on proliferation of cancerous cells, but also on the ability of myeloma cells to traffic between sites and home to appropriate survival niches. Identifying the mechanisms that regulate the homing of MM cells to the bone marrow, the MM-BMSC interaction and the trafficking of MM cells from the bloodstream to distant bone locations is therefore crucial to design new, more effective therapies capable of overcoming the maladaptive interaction between BMSCs and MM and help in finding a cure for MM.

Downregulated plasma miR-92a levels have clinical impact on multiple myeloma and related disorders

Recent studies have demonstrated that one-third of known microRNAs (miRNAs) are stably detectable in plasma. Therefore, we assessed plasma miRNAs to investigate the dynamics of oncomir 17-92a, which is highly expressed in multiple myeloma (MM) patients. The plasma miR-92a level in symptomatic MM patients was significantly downregulated compared with normal subjects (P<0.0001), regardless of immunoglobulin subtypes or disease stage at diagnosis. In contrast, miR-92a levels in peripheral blood CD8⁺ or CD4⁺ cells from MM patients were lower than those of normal subjects, and the miR-92a levels of the cells tended to correlate with plasma miR-92a levels. The plasma miR-92a level in the complete remission group became normalized, whereas the partial response (PR) and very good PR groups did not reach the normal range. In smoldering MM, the plasma miR-92a level did not show a significant difference compared with normal subjects. Our findings suggest that measurement of the plasma miR-92a level in MM patients could be useful for initiation of chemotherapy and monitoring disease status, and the level may represent, in part, the T-cell immunity status of these patients.

QUICK identification and SPR validation of signal transducers and activators of transcription 3 (Stat3) interacting proteins

Signal transducers and activators of transcription 3 (Stat3) has been reported to be involved in the pathogenesis of various human diseases and is constitutively active in human multiple myeloma (MM) U266 cells. The Stat3-regulated mechanisms involved in these processes, however, are not fully defined. To further understand the regulation of Stat3 activity, we performed a systematic proteomic analysis of Stat3 interacting proteins in U266 cells. This analysis, termed quantitative immunoprecipitation combined with knockdown (QUICK), combines RNAi, stable isotope labeling with amino acids in cell culture (SILAC), immunoprecipitation, and quantitative MS. As a result, quantitative mass spectrometry analysis allowed us to distinguish specific Stat3 interacting proteins from background proteins and led to the identification of a total of 38 proteins. Three Stat3 interacting proteins - 14-3-3ζ, PRKCB and Hsp90 - were further confirmed by reciprocal co-immunoprecipitations and surface plasmon resonance (SPR) analysis. Our results therefore not only uncover a number of Stat3 interacting proteins that possess a variety of cellular functions, but also provide new insight into the mechanisms that regulate Stat3 activity and function in MM cells.

Melanoma vasculogenic mimicry capillary-like structure formation depends on integrin and calcium signaling

OBJECTIVE

We recently demonstrated that the formation of CLSs in vitro, which are thought to be a reconstitution of VM, is controlled by VEGFA. CLS formation also requires the extracellular matrix signals, presumably transduced by integrins. Both pathways are affected by Ca(2+). Therefore, we directly tested the roles of Ca(2+) and integrin in melanoma VM.

METHODS

The investigation was performed by immunocytochemical, histochemical, and 3D co-culture assays. We have also used an in vivo animal model.

RESULTS

The extracellular and intracellular Ca(2+) chelators, EGTA and BAPTA-AM, prevented CLS formation on Matrigel, caused actin rearrangement, and completely destroyed the preformed CLS. Addition of colcemid or cytochalasin D prevented the CLS formation and destroyed the preformed CLS network. Herein, we also show that blocking antibodies to ανβ3 and ανβ5 integrins disrupted the CLS network. Control blocking antibody to β1 integrin had no effect. In vivo experiments indicated that Ca(2+) chelation dramatically reduced the signs of VM in melanoma tumors grafted in mice.

CONCLUSIONS

Our results indicate that the formation of CLS is tightly regulated by extracellular and intracellular Ca(2+) levels; ανβ3 and ανβ5 integrins are primarily responsible for CLS formation, whereas β1 integrin does not participate in CLS formation.

Preclinical evaluation of a novel SIRT1 modulator SRT1720 in multiple myeloma cells

SIRT1 belongs to the silent information regulator 2 (Sir2) protein family of enzymes and functions as a NAD(+) -dependent class III histone deacetylase. Here, we examined the anti-multiple myeloma (MM) activity of a novel oral agent, SRT1720, which targets SIRT1. Treatment of MM cells with SRT1720 inhibited growth and induced apoptosis in MM cells resistant to conventional and bortezomib therapies without significantly affecting the viability of normal cells. Mechanistic studies showed that anti-MM activity of SRT1720 is associated with: (i) activation of caspase-8, caspase-9, caspase-3, poly(ADP) ribose polymerase; (ii) increase in reactive oxygen species; (iii) induction of phosphorylated ataxia telangiectasia mutated/checkpoint kinase 2 signalling; (iv) decrease in vascular endothelial growth factor-induced migration of MM cells and associated angiogenesis; and (v) inhibition of nuclear factor-κB. Blockade of ATM attenuated SRT1720-induced MM cell death. In animal tumour model studies, SRT1720 inhibited MM tumour growth. Finally, SRT1720 enhanced the cytotoxic activity of bortezomib or dexamethasone. Our preclinical studies provide the rationale for novel therapeutics targeting SIRT1 in MM.

Association of clinicopathologic parameters with the expression of inducible nitric oxide synthase and vascular endothelial growth factor in mucoepidermoid carcinoma

BACKGROUND

The roles that inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor (VEGF) play in tumorigenesis have been given special attention. In many tumors, their expression is upregulated. In addition, iNOS can stimulate the expression of VEGF. This study was carried out to investigate the expression of iNOS and VEGF as well as their relationship with angiogenesis and the clinicopathological characteristics of mucoepidermoid carcinoma (MEC).

METHOD

The expression of iNOS and VEGF was detected by Streptavidin-peroxidase immunohistochemistry, and microvessel density (MVD) was determined by anti-CD34 antibody staining in 70 MEC cases and 40 normal salivary gland tissues (NSG). Follow-up was performed on the 70 patients with MEC. Non-parametric tests were performed for the comparison of iNOS and VEGF expression.

RESULTS

The positive expression rates of iNOS and VEGF were successively enhanced in NSG, well-differentiated and poorly differentiated MEC (P < 0.05). MVD counts were positively correlated with the expression levels of iNOS and VEGF in MEC (P < 0.05). The expression of iNOS was positively correlated with the expression of VEGF (P < 0.05). iNOS and VEGF expression were significantly associated with tumor differentiation, size metastasis, and relapse (P < 0.05) but were not correlated lymph node metastasis and metastasis.

CONCLUSION

Inducible nitric oxide synthase can stimulate the expression of VEGF, and their expression status may help assess tumor malignancy and patient prognosis.

A novel bisindolymaleimide derivative (WK234) inhibits proliferation and induces apoptosis through the protein kinase Cβ pathway, in chronic myelogenous leukemia K562 cells

WK234, a novel bisindolymaleimide derivative, was designed as a protein kinase Cβ (PKCβ) inhibitor. The objective of this study was to evaluate the anti-tumor activity of WK234 in the human chronic myelogenous leukemia (CML) K562 cell line and to investigate possible mechanisms of its action. The results show that WK234 inhibited K562 cell proliferation in a time- and dose-dependent manner. WK234 increased cytochrome C release and caspase-3 cleavage, which indicates that it induced apoptosis via mitochondria- and caspase-mediated pathways. Western blotting showed that PKCβ1, PKCβ2, and their phosphorylation levels were effectively decreased after 2-4 h of WK234 treatment. Meanwhile the phosphorylation status of PKCβ downstream proteins, glycogen synthase kinase 3α/β (GSK3α/β) and extracellular signal-regulated kinase (ERK), were inhibited. WK234 blocked phorbol myristate acetate (PMA)-induced Ser(660) phosphorylation of PKCβ2 located at the cell membrane, and increased Ser(660) PKCβ2 expression within the cytoplasm and the nucleus. These results indicate that WK234 inhibited cell proliferation and induced apoptosis through suppressing the PKCβ signal pathway. WK234 might be a promising candidate for the treatment of CML.

Integrin β7-mediated regulation of multiple myeloma cell adhesion, migration, and invasion

Integrin-β7 (ITGB7) mRNA is detected in multiple myeloma (MM) cells and its presence is correlated with MAF gene activation. Although the involvement of several integrin family members in MM-stoma cell interaction is well documented, the specific biologic functions regulated by integrin-β7 in MM are largely unknown. Clinically, we have correlated integrin-β7 expression in MM with poor survival outcomes post autologous stem cell transplantation and postsalvage therapy with bortezomib. Functionally, we have found that shRNA-mediated silencing of ITGB7 reduces MM-cell adhesion to extra-cellular matrix elements (fibronectin, E-cadherin) and reverses cell-adhesion-mediated drug resistance (CAM-DR) sensitizing them to bortezomib and melphalan. In addition, ITGB7 silencing abrogated MM-cell transwell migration in response to SDF1α gradients, reduced vessel density in xenografted tumors, and altered MM cells in vivo homing into the BM. Mechanistically, ITGB7 knockdown inhibited focal adhesion kinase (FAK) and Src phosphorylation, Rac1 activation, and SUMOylation, reduced VEGF production in MM-BM stem cell cocultures and attenuated p65-NF-κB activity. Our findings support a role for integrin-β7 in MM-cell adhesion, migration, and BM homing, and pave the way for a novel therapeutic approach targeting this molecule.

Multiple myeloma: biology of the disease

Multiple myeloma (MM) is a clonal B-cell malignancy characterized by the aberrant expansion of plasma cells within the bone marrow, as well as at extramedullary sites. Decades of scientific research are now beginning to unravel the intricate biology that underlies the pathophysiology of MM. In particular, the roles of cellular differentiation, molecular pathogenesis, and oncogenes involved in the natural history of MM are becoming clearer. This has enabled the identification of specific cytokines, adhesion molecules, and stromal cells that affect MM cell development, disease progression, and treatment responses. This review describes our current understanding regarding the biology of MM, and how this has led to a robust pipeline of novel therapeutic agents with the potential to overcome resistance to existing MM therapies and, therefore, further improve outcomes in patients with MM.

Integrin targeted delivery of chemotherapeutics

Targeted delivery of chemotherapeutics is defined in the sense, that is, to maximize the therapeutic index of a chemotherapeutic agent by strictly localizing its pharmacological activity to the site or tissue of action. Integrins are a family of heterodimeric transmembrane glycoproteins involved in a wide range of cell-to-extracellular matrix (ECM) and cell-to-cell interactions. As cell surface receptors, integrins readily interact with extracellular ligands and play a vital role in angiogenesis, leukocytes function and tumor development, which sets up integrins as an excellent target for chemotherapy treatment. The peptide ligands containing the arginine-glycine-aspartic acid (RGD), which displays a strong binding affinity and selectivity to integrins, particularly to integrin αvβ3, have been developed to conjugate with various conventional chemotherapeutic agents, such as small molecules, peptides and proteins, and nanoparticle-carried drugs for integtrin targeted therapeutic studies. This review highlights the recent advances in integrin targeted delivery of chemotherapeutic agents with emphasis on target of integrin αvβ3, and describes the considerations for the design of the diverse RGD peptide-chemotherapeutics conjugates and their major applications.

Cancer-stromal interactions: role in cell survival, metabolism and drug sensitivity

It has been known for a long time that the interaction between cancer cells and tissue microenvironment plays a major role in cancer development, progression and metastasis. The biochemical aspect of cancer-stromal interactions, however, is less appreciated. This short review article first provides a brief summary of the communications between cancer cells and the tissue microenvironment by direct cell-cell interactions and by soluble factors, and then describes several biochemical pathways that are important for the interaction between stromal and cancer cells with respect to energy metabolism, redox balance, cell survival and drug resistance. The potential therapeutic implications of abolishing stromal protective mechanisms to overcome drug resistance are also discussed.

A novel orally active proteasome inhibitor ONX 0912 triggers in vitro and in vivo cytotoxicity in multiple myeloma

Bortezomib therapy has proven successful for the treatment of relapsed, relapsed/refractory, and newly diagnosed multiple myeloma (MM). At present, bortezomib is available as an intravenous injection, and its prolonged treatment is associated with toxicity and development of drug resistance. Here we show that the novel proteasome inhibitor ONX 0912, a tripeptide epoxyketone, inhibits growth and induces apoptosis in MM cells resistant to conventional and bortezomib therapies. The anti-MM activity of ONX-0912 is associated with activation of caspase-8, caspase-9, caspase-3, and poly(ADP) ribose polymerase, as well as inhibition of migration of MM cells and angiogenesis. ONX 0912, like bortezomib, predominantly inhibits chymotrypsin-like activity of the proteasome and is distinct from bortezomib in its chemical structure. Importantly, ONX 0912 is orally bioactive. In animal tumor model studies, ONX 0912 significantly reduced tumor progression and prolonged survival. Immununostaining of MM tumors from ONX 0912-treated mice showed growth inhibition, apoptosis, and a decrease in associated angiogenesis. Finally, ONX 0912 enhances anti-MM activity of bortezomib, lenalidomide dexamethasone, or pan-histone deacetylase inhibitor. Taken together, our study provides the rationale for clinical protocols evaluating ONX 0912, either alone or in combination, to improve patient outcome in MM.

Vascular endothelial growth factor receptor 1 contributes to Escherichia coli K1 invasion of human brain microvascular endothelial cells through the phosphatidylinositol 3-kinase/Akt signaling pathway

Escherichia coli is the most common Gram-negative organism causing neonatal meningitis. Previous studies demonstrated that E. coli K1 invasion of brain microvascular endothelial cells (BMEC) is required for penetration into the central nervous system, but the microbe-host interactions that are involved in this process remain incompletely understood. Here we report the involvement of vascular endothelial growth factor receptor 1 (VEGFR1) expressed on human brain microvascular endothelial cells (HBMEC) in E. coli K1 invasion of HBMEC. Our results showed that treatment of confluent HBMEC with pan-VEGFR inhibitors significantly inhibited E. coli K1 invasion of HBMEC. Immunofluorescence results indicated the colocalization of VEGFR1 with E. coli K1 during bacterial invasion of HBMEC. The E. coli-induced actin cytoskeleton rearrangements in HBMEC were blocked by VEGFR inhibitors but not by VEGFR2-specific inhibitors. The small interfering RNA (siRNA) knockdown of VEGFR1 in HBMEC significantly attenuated E. coli invasion and the concomitant actin filament rearrangement. Furthermore, we found an increased association of VEGFR1 with the p85 subunit of phosphatidylinositol 3-kinase (PI3K) in HBMEC infected with E. coli K1 and that E. coli K1-triggered Akt activation in HBMEC was blocked by VEGFR1 siRNA and VEGFR inhibitors. Taken together, our results demonstrate that VEGFR1 contributes to E. coli K1 invasion of HBMEC via recruitment of the PI3K/Akt signaling pathway.

Biological impact of vascular endothelial growth factor on vessel density and survival in multiple myeloma and plasmacytoma

We compared the differences in a number of angiogenesis-related immunohistochemical parameters, including microvascular density (MVD) and tumor cell activity, between multiple myeloma (MM) and solitary plasmacytoma (SP). Tissue sections from tumors of MM and SP were immunohistochemically stained and analyzed using ImageJ image analysis software for the expression of vascular endothelial growth factor (VEGF), VEGF receptors (Flt-1 and Flk-1), inducible nitric oxide (iNOS), and anti-apoptotic (Bcl-2) protein. Tumor tissues were cytologically graded as high-, intermediate-, or low-grade. Two pathologists determined the MVD of each section independently by recording the average number of CD34+ blood vessels in 500 unit fields. The arithmetic means for MVD were statistically analyzed using the Student's t-test and the significance level was calculated at P-value <0.001. The results indicate a direct correlation between upregulation of iNOS/VEGF in high-grade tumors. For MM, an increase in MVD is also correlated with a high-grade. Tumor survival signaling by Bcl-2 in both SP and MM emphasizes the fact that VEGF has a bimodal role that is mainly angiogenic in MM and tumorigenic, promoting tumor cell survival in SP.

The cytokine/chemokine pattern in the bone marrow environment of multiple myeloma patients

OBJECTIVE

The interaction of multiple myeloma (MM) with its bone marrow (BM) microenvironment is important for the homing pattern, survival, and proliferation of malignant plasma cells. We aimed at answering the question which cytokines, chemokines, and growth factors are typically found in the BM of untreated MM patients as well as in MM patients after allogeneic stem cell transplantation (alloSCT).

MATERIALS AND METHODS

We determined the concentrations of 34 cytokines/chemokines in the supernatants of 10 myeloma cell lines, as well as in the plasma derived from BM and peripheral blood samples of 10 newly diagnosed MM patients, 20 MM patients who had received allogeneic stem cell transplantation (alloSCT), and 20 healthy donors.

RESULTS

Besides cytokines/chemokines known to be secreted by myeloma cell lines, such as interleukin-1 receptor antagonist (IL-1RA), IL-8, monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1α, MIP-1β, and MIP-3α, we also detected significant levels of epidermal growth factor (EGF), hepatocyte growth factor (HGF), IL2R, IL-12p40/p70, IL-22, interferon-γ (IFN-γ)-inducible protein 10 (IP-10), monokine induced by IFN-γ (MIG), and regulated on activation normally T-cell expressed and secreted (RANTES) in culture supernatants. The BM environment in MM patients evidenced elevated concentrations of HGF, IL-2R, IL-16, EGF, IL-1RA, IP-10, MCP-1, and monokine induced by IFN-γ. Additionally, in the BM of MM patients post alloSCT, we found selectively elevated concentration of IL-4, IL-6, IL-8, IL-12p40/p70, and eotaxin. Eotaxin levels were particularly high in patients with chronic graft-vs-host disease.

CONCLUSIONS

Our study demonstrates characteristic cytokine/chemokine patterns in the BM environment of MM patients before and after alloSCT. Certain factors, such as MIP-1α, MCP-1, HGF, IL-16, IP-10, and eotaxin, might not only be developed into diagnostic instruments and/or predictive biomarkers, but are also potential targets for future myeloma- or graft-vs-host disease-specific therapies.

The PKCbeta/HuR/VEGF pathway in diabetic retinopathy

We investigated whether the diabetes-related PKCbeta activation affects VEGF expression through the mRNA-stabilizing human embryonic lethal abnormal vision (ELAV) protein, HuR, in the retina of streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in rats by STZ injection. Retinal tissues were processed to detect PKCbetaI, PKCbetaII, VEGF and HuR contents, as well as HuR phosphorylation. Immunoprecipitation coupled to RT-PCR was employed to evaluate HuR binding to VEGF mRNA in RiboNucleoProteic (RNP) complexes. Statistical analysis was performed by ANOVA followed by an appropriate post hoc comparison test. Following experimental diabetes PKCbetaI and PKCbetaII levels were increased compared to sham; there was also a PKC-mediated phosphorylation/activation of HuR. These effects were blunted by the in vivo co-administration of a selective PKCbeta inhibitor. A specific binding between the HuR protein and the VEGF mRNA was also detected. The PKCbeta/HuR activation was accompanied by enhanced VEGF protein expression that was, again, blunted by the PKCbeta inhibitor. These findings first demonstrate the activation, in the retina, of the PKCbeta/HuR/VEGF pathway following experimental diabetes and disclose a new potential pharmacological target to counteract pathologies implicating VEGF deregulation, such as diabetic retinopathy.