Interdependence between cytokines and cell adhesion molecules to induce interleukin-6 production by stromal cells in myeloma

Review paper. Chemobrain in patients suffering from cancer based on the example of multiple myeloma

Introduction: The incidence rate of cancers emphasizes the necessity to investigate not only patients’ somatic ailments but also their psychosocial functioning as well as the need to raise the quality standards of cancer patients. The improvement of the quality of life is one of the major challenges of psycho-oncology, which is the science created in the interface of two disciplines: psychology and medicine.

One of the important aspects of psycho-oncologists’ activity is the minimization of negative side-effects related to treatment, such as changes in patients’ cognitive functioning resulting from anti-cancer treatment.

Objective: The aim of this work is to provide the reader with the knowledge concerning the phenomenon of chemobrain in a very special group of patients with hemato-oncologic tumour. Few researches related to this topic have confirmed the occurrence of cognitive deficits resulting from the cancer process, taken cytotoxic drugs, other forms of anti-cancer therapy and the activeness of biochemical compounds in patients with multiple myeloma.

Methods: The author has done a literary review concerning the topic under study using the Google Scholar and EBSCO databases. The main part of this work consists of references to Polish and English research literature published after 2000. The review includes also classic works from the eighties and nineties of the 20th century.

Results: The present work has been divided into several sections. The part devoted to explanation of the term chemobrain describes the evolution of its definition over the years. The second section - ‘Heterogeneity of the phenomenon - causes’ - underlines the influence of biochemical etiological factors, such as the impact of the activity of proinflammatory cytokines on the cognitive state of the patients suffering from tumour. Next part - ‘Chemobrain and multiple myeloma’ is devoted to the clinical characteristics of this cancer and to the descriptions of the selected methods of chemotherapy. The review of researches concerning the deteriorated cognitive functioning of patients with multiple myeloma in relation to the probable aetiology of this disease has been also presented.

Conclusions: The review of Polish and English literature concerning the functioning of memory and attention processes in the patients suffering from multiple myeloma can serve as an inspiration for a search for objective biochemical factors conditioning the deterioration of cognitive processes of the patients undergoing anti-cancer treatment.

Mesenchymal stem cells: key players in cancer progression

Tumour progression is dependent on the interaction between tumour cells and cells of the surrounding microenvironment. The tumour is a dynamic milieu consisting of various cell types such as endothelial cells, fibroblasts, cells of the immune system and mesenchymal stem cells (MSCs). MSCs are multipotent stromal cells that are known to reside in various areas such as the bone marrow, fat and dental pulp. MSCs have been found to migrate towards inflammatory sites and studies have shown that they also migrate towards and incorporate into the tumour. The key question is how they interact there. MSCs may interact with tumour cells through paracrine signalling. On the other hand, MSCs have the capacity to differentiate to various cell types such as osteocytes, chondrocytes and adipocytes and it is possible that MSCs differentiate at the site of the tumour. More recently it has been shown that cross-talk between tumour cells and MSCs has been shown to increase metastatic potential and promote epithelial-to-mesenchymal transition. This review will focus on the role of MSCs in tumour development at various stages of progression from growth of the primary tumour to the establishment of distant metastasis.

Mesenchymal stem cells as a double-edged sword in suppression or progression of solid tumor cells

Tumor cells are able to attract mesenchymal stem cells (MSCs) to primary tumor site. On the other hand, MSCs secrete various factors to attract tumor cells towards BM. In this review, in addition to assessment of MSCs function at tumor sites and their impact on growth and metastasis of tumor cells, the importance of MSC in attraction of malignant cells to BM and their involvement in drug resistance of tumor cells have also been studied. Relevant literature was identified by a PubMed search (2000-2015) of English-language literature using the terms mesenchymal stem cells, cancer cell, metastasis, and tumor microenvironment. MSCs migrate towards tumor microenvironment and are involved in both pro-tumorigenic and antitumorigenic functions. The dual function of MSCs at tumor sites is dependent upon a variety of factors, including the type and origin of MSCs, the cancer cell line under study, in vivo or in vitro conditions, the factors secreted by MSCs and interactions between MSCs, host immune cells and cancer cells. Therefore, MSCs can be regarded both as friends and enemies of cancer cells. Although the role of a number of pathways, including IL-6/STAT3 pathway, has been indicated in controlling the interaction between MSCs and tumor cells, other mechanisms by which MSCs can control the tumor cells are not clear yet. A better understanding of these mechanisms through further studies can determine the exact role of MSCs in cancer progression and identify them as important therapeutic agents or targets.

Prognostic indicators of lenalidomide for multiple myeloma: consensus and controversy

The long-term outcome of multiple myeloma (MM) has been greatly improved through new agents, one being lenalidomide (LEN). Based upon the findings of in vitro experiments, its mode of action against MM occurs through a combination of direct tumoricidal effects on myeloma cells, modulatory effects on tumor immunity and tumor microenvironment-regulatory effects. However, it has not been clearly defined whether the clinical response and long-term outcome of MM with LEN treatment truly reflect the mechanisms of action of LEN proposed by in vitro studies. To ascertain what is known and what remains to be elucidated with LEN, we review the current literature on the mode of action of LEN in association with myeloma pathophysiology, and discuss the prognostic indicators in the treatment of MM with LEN.

Implication of tumor microenvironment in chemoresistance: tumor-associated stromal cells protect tumor cells from cell death

Tumor development principally occurs following the accumulation of genetic and epigenetic alterations in tumor cells. These changes pave the way for the transformation of chemosensitive cells to chemoresistant ones by influencing the uptake, metabolism, or export of drugs at the cellular level. Numerous reports have revealed the complexity of tumors and their microenvironment with tumor cells located within a heterogeneous population of stromal cells. These stromal cells (fibroblasts, endothelial or mesothelial cells, adipocytes or adipose tissue-derived stromal cells, immune cells and bone marrow-derived stem cells) could be involved in the chemoresistance that is acquired by tumor cells via several mechanisms: (i) cell-cell and cell-matrix interactions influencing the cancer cell sensitivity to apoptosis; (ii) local release of soluble factors promoting survival and tumor growth (crosstalk between stromal and tumor cells); (iii) direct cell-cell interactions with tumor cells (crosstalk or oncologic trogocytosis); (iv) generation of specific niches within the tumor microenvironment that facilitate the acquisition of drug resistance; or (v) conversion of the cancer cells to cancer-initiating cells or cancer stem cells. This review will focus on the implication of each member of the heterogeneous population of stromal cells in conferring resistance to cytotoxins and physiological mediators of cell death.

A galectin-3-dependent pathway upregulates interleukin-6 in the microenvironment of human neuroblastoma

Interleukin-6 (IL-6) is a pleiotropic cytokine with a broad range of physiologic and pathologic functions. Because in cancer, IL-6 contributes to a microenvironment that promotes tumor cell survival, angiogenesis, and inflammation, understanding the mechanism responsible for its production is important. In neuroblastoma, the second most common solid tumor in children, IL-6 is produced not by tumor cells but by stromal cells such as monocytes and bone marrow mesenchymal stem cells (BMMSC). Here we show that the production of IL-6 in BMMSCs is in part stimulated by galectin-3 binding protein (Gal-3BP) secreted by neuroblastoma cells. We identified a distal region of the IL-6 promoter that contains 3 CCATT/enhancer binding protein (C/EBP) binding domains involved in the transcriptional upregulation of IL-6 by Gal-3BP. Gal-3BP interacted with Galectin-3 (Gal-3) present in BMMSCs, and a Gal-3BP/Gal-3/Ras/MEK/ERK signaling pathway was responsible for the transcriptional upregulation of IL-6 in BMMSCs in which Gal-3 has a necessary function. In support of the role of this pathway in human neuroblastoma tumors, Gal-3BP was found to be present in tumor cells and in the adjacent extracellular matrix of 96% of 78 primary neuroblastoma tumor samples examined by immunohistochemistry. Considering the protumorigenic function of IL-6 in cancer, this tumor cell-stromal cell interactive pathway could be a target for anticancer therapy.

Mesenchymal niches of bone marrow in cancer

Over the last decade, genetic and cell biology studies have indicated that tumour growth is not only determined by malignant cancer cells themselves, but also by the tumour microenvironment. Cells present in the tumour microenvironment include fibroblasts, vascular, smooth muscle, adipocytes, immune cells and mesenchymal stem cells (MSC). The nature of the relationship between MSC and tumour cells appears dual and whether MSC are pro- or anti-tumorigenic is a subject of controversial reports. This review is focused on the role of MSC and bone marrow (BM) niches in cancer.

Towards effective immunotherapy of myeloma: enhanced elimination of myeloma cells by combination of lenalidomide with the human CD38 monoclonal antibody daratumumab

BACKGROUND

In our efforts to develop novel effective treatment regimens for multiple myeloma we evaluated the potential benefits of combining the immunomodulatory drug lenalidomide with daratumumab. Daratumumab is a novel human CD38 monoclonal antibody which kills CD38+ multiple myeloma cells via antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity and apoptosis.

DESIGN AND METHODS

To explore the effect of lenalidomide combined with daratumumab, we first carried out standard antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity assays in which the CD38+ multiple myeloma cell line UM-9 and primary multiple myeloma cells isolated from patients were used as target cells. We also tested the effect of lenalidomide on daratumumab-dependent cell-mediated-cytotoxicity and complement-dependent cytotoxicity of multiple myeloma cells directly in the bone marrow mononuclear cells of multiple myeloma patients. Finally, we determined the daratumumab-dependent cell-mediated cytotoxicity using peripheral blood mononuclear cells of multiple myeloma patients receiving lenalidomide treatment.

RESULTS

Daratumumab-dependent cell-mediated cytotoxicity of purified primary multiple myeloma cells, as well as of the UM-9 cell line, was significantly augmented by lenalidomide pre-treatment of the effector cells derived from peripheral blood mononuclear cells from healthy individuals. More importantly, we demonstrated a clear synergy between lenalidomide and daratumumab-induced antibody-dependent cell-mediated cytotoxicity directly in the bone marrow mononuclear cells of multiple myeloma patients, indicating that lenalidomide can also potentiate the daratumumab-dependent lysis of myeloma cells by activating the autologous effector cells within the natural environment of malignant cells. Finally, daratumumab-dependent cell-mediated cytotoxicity was significantly up-regulated in peripheral blood mononuclear cells derived from 3 multiple myeloma patients during lenalidomide treatment.

CONCLUSIONS

Our results indicate that powerful and complementary effects may be achieved by combining lenalidomide and daratumumab in the clinical management of multiple myeloma.

Abnormal cytokine production by bone marrow stromal cells of multiple myeloma patients in response to RPMI8226 myeloma cells

INTRODUCTION

Recent studies indicate that bone marrow stromal cells (BMSCs) derived from patients with multiple myeloma (MM) differ from those of healthy donors in their expression of extracellular matrix compounds and in cytokine production. It is not known whether these abnormalities are primary or are acquired by BMSCs on contact with MM cells.

MATERIALS AND METHODS

Interleukin (IL)-6, IL-11, IL-10, and tumor necrosis factor (TNF)-alpha production by CD166+ mesenchymal BMSCs and the CD38+/CD138+ RPMI8226 myeloma cell line cultivated in vitro in monocultures or co-cultivated under cell-to-cell contact or non-contact conditions in the presence of a tissue culture insert were measured. Intracellular cytokines were measured by flow cytometry analysis as the percentage of cytokine-producing cells or by mean fluorescence intensity as the level of cytokine expression in cells. Additionally, ELISA was used to measure IL-6, soluble IL-6 receptor (sIL-6R), IL-11, IL-10, TNF-alpha, B-cell-activating factor of the TNF family (BAFF), hepatocyte growth factor (HGF), and osteopontin (OPN) production in the supernatants of the cultures and co-cultures.

RESULTS

A higher ability of the BMSCs of MM patients than in controls was detected to produce IL-6, IL-10, TNF-alpha, OPN, and especially HGF and BAFF in response to the RPMI8226 cells. Moreover, the BMSCs of the MM patients significantly enhanced the production of sIL-6R by the RPMI8226 cells.

DISCUSSION

Cytokines over-expressed by BMSCs of MM patients can function as growth factors for myeloma cells (IL-6, IL-10, HGF), migration stimulatory factors for tumor plasma cells (TNF-alpha, HGF), adhesion stimulatory factors (HGF, BAFF and OPN), stimulators of osteoclastogenesis (IL-6, TNF-alpha), and angiogenic factors (TNF-alpha). The results of this experiment strongly suggest that the BMSCs from MM patients differed in spontaneous and myeloma cell-induced production of cytokines, especially of HGF and BAFF, and these abnormalities were both primary and acquired by the BMSCs on contact with the MM cells. This in turn suggests the presence of an undefined, autocrine stimulation pathway resulting in a prolonged production of cytokines even in long-term cultures in vitro and in vivo. These abnormalities might provide optimal conditions for the proliferation and differentiation of residual tumor cells or their precursors in the affected bone marrow.

HSP70 inhibition reverses cell adhesion mediated and acquired drug resistance in multiple myeloma

Heat shock proteins (HSPs) are a super family of highly conserved molecular chaperone proteins, which are induced in response to stress. HSP70 has been demonstrated to inhibit apoptosis induced by a number of chemotherapeutic agents. Previous investigations have suggested the development of drug resistance in multiple myeloma (MM) cells after adhesion to stroma. This study used MM cell lines and primary plasma cells to determine if HSP70 had a role in development of chemo resistance. Adhesion of MM cells to either bone marrow stromal cells or fibronectin (FN) enhanced HSP70 expression. Inhibition of the HSP70 expression decreased 8226 cell adhesion to stroma or FN and induced more apoptosis in FN-adhered 8226 cells than in suspension cultures at 24 h. Further, HSP70 inhibitors enhanced melphalan-induced apoptosis and reversed melphalan-induced cell adhesion-mediated drug resistance (CAM-DR) phenotype. In addition, compared to parental cells, KNK-437, a heat shock factor inhibitor caused more apoptosis in melphalan-resistant 8226/LR5 cells and sensitized them to melphalan. Primary CD138 positive cells showed high expression of HSPA4 mRNA, and KNK-437 caused apoptosis in these cells. In conclusion, our data suggest inhibition of HSP70, reduced adhesion and caused apoptosis of both acquired and de novo drug resistant MM cells.

Identification of Two Groups of Smoldering Multiple Myeloma Patients Who Are Either High or Low Producers of Interleukin-1

Interleukin-1beta (IL-1beta) is abnormally expressed by the plasma cells obtained from myeloma patients, and it is a potent inducer of the important myeloma growth factor, IL-6. We investigated whether levels of IL-1beta biologic activity might distinguish different groups of patients with smoldering multiple myeloma (SMM). We measured the ability of IL-6 production by bone marrow stromal cells to serve as a surrogate marker for IL-1beta biologic activity. Using this IL-1beta bioassay, we found that it is sensitive at < 1 pg/ml of recombinant IL-1beta and that IL-1beta biologic activity is detectable with either mature or pro-IL-1beta-transduced myeloma cell lines. Patients with active myeloma induced quantitatively higher levels of stromal cell IL-6 production when compared with those with monoclonal gammopathy of undetermined significance (MGUS). The bioassay distinguished two groups of SMM patients, those who were high producers, similar to patients with active MM, and those who were low producers, comparable to MGUS patients. IL-1 antagonists inhibited the paracrine IL-6 production by > or = 90% in the majority of patients with an elevated IL-6 level. Based on such studies, it may be possible to predict patients that will progress to active MM and to delay or prevent this progression with IL-1 antagonists.

Targeting receptor kinases by a novel indolinone derivative in multiple myeloma: abrogation of stroma-derived interleukin-6 secretion and induction of apoptosis in cytogenetically defined subgroups

In multiple myeloma (MM), both vascular endothelial (VEGF) and basic fibroblast growth factor (bFGF) promote tumor growth and survival. We have used the novel indolinone BIBF 1000 to study effects of simultaneous inhibition of VEGF, FGF and transforming growth factor-beta on MM cells and their interactions with bone marrow stroma cells (BMSCs). Both, in the absence and presence of myeloma-stroma cell contacts, BIBF 1000 abrogated BMSC-derived secretion of interleukin-6 (IL-6). In addition, BIBF 1000 directly induced apoptosis in t(4;14)-positive cell lines as well as in CD138+ marrow cells from patients with t(4;14) myeloma. To a similar extent, BIBF 1000 induced apoptosis in MM.1S and MM.1R cells carrying the translocation t(14;16). In case of MM.1S and other dexamethasone-sensitive t(14;16) cell lines, BIBF 1000 and dexamethasone had additive proapoptotic effects. Induction of apoptosis by BIBF 1000 was associated with inhibition of the mitogen-activated protein kinases (MAPK) pathway in t(4;14) and inhibition of the phosphatidyl-inositol-3 kinase/AKT pathway in t(14;16) cells. Apoptotic effects did not occur in t(4;14)-or t(14;16)-positive MM cells carrying n- or k-Ras mutations. The data provide the rationale for clinical evaluation of this class of targeted kinase inhibitors in MM with focus on defined cytogenetic subgroups.

MIP-1α utilizes both CCR1 and CCR5 to induce osteoclast formation and increase adhesion of myeloma cells to marrow stromal cells

OBJECTIVES

Macrophage inflammatory protein-1alpha (MIP-1alpha), an osteoclast (OCL) stimulatory factor produced by primary multiple myeloma (MM) cells, increases bone destruction and tumor burden in murine models of MM. Several chemokine receptors (CCR1, CCR5, and CCR9) mediate the effects of MIP-1alpha. In this study, we determined which of these mediates the effects of MIP-1alpha on human OCL formation and myeloma cells.

METHODS

We employed RT-PCR analysis, neutralizing antibodies to CCR1 and CCR5 as well as a CCR1-specific antagonist and OCL formation assays to identify the MIP-1alpha receptors involved in MIP-1alpha's effects on myeloma cells and OCL formation.

RESULTS

RT-PCR analysis demonstrated that both CCR1 and CCR5 were expressed by highly purified human OCL precursors, myeloma cell lines, and purified marrow plasma cells from MM patients. Neutralizing antibodies to CCR1 or CCR5 inhibited MIP-1alpha-induced OCL formation. Furthermore, monocyte chemotactic protein-3 (MCP-3), which binds CCR1 but not CCR5 and the CCR1-specific antagonist, BX471, markedly inhibited OCL formation stimulated with MIP-1alpha. Anti-CCR1, anti-CCR5, or BX471 also inhibited the upregulation of beta1 integrin mRNA in myeloma cells induced by MIP-1alpha, as well as the adherence of myeloma cells to stromal cells and IL-6 production by stromal cells in response to myeloma cells.

CONCLUSION

These data demonstrate that MIP-1alpha utilizes either CCR1 or CCR5 for its effects on OCL formation and myeloma cells, and that blocking either CCR1 or CCR5 inhibits OCL formation and myeloma cell adhesion to stromal cells.

Transendothelial migration of myeloma cells is increased by tumor necrosis factor (TNF)-alpha via TNF receptor 2 and autocrine up-regulation of MCP-1

The proinflammatory cytokine tumor necrosis factor (TNF)-alpha has been shown to facilitate leukocyte transendothelial migration. In multiple myeloma, TNF-alpha is an important factor in the promotion of growth and survival of the malignant cells. Studies have shown that enhanced TNF-alpha levels in myeloma patients correlated with aggressive disease. Therefore, we investigated the effect of recombinant human TNF-alpha on the migrational behavior of myeloma cells across the physiological barrier of the major disease compartment, i.e., human bone marrow endothelial cells. In the presence of TNF-alpha, we observed significantly increased migration both in established myeloma cell lines and in plasma cells from myeloma patients. Expression of TNF-receptor 2 (TNF-R2) but not TNF-receptor 1 (TNF-R1) was detected in myeloma cell lines. Myeloma cells of patients also showed expression of TNF-R2 but not TNF-R1. The effect of TNF-alpha could not be explained by altered expression of adhesion molecules or metalloproteases. Instead, we found an up-regulation of monocyte chemoattractant protein (MCP)-1 and confirmed that myeloma cells express the relevant receptor C-C chemokine receptor 2. Preincubation of myeloma cells with recombinant human MCP-1 also enhanced cell migration, and this effect, as well as the effect of TNF-alpha, was abolished by treatment with anti-MCP-1 antibody. In contrast, migration of myeloma cells in the direction of an MCP-1 gradient, i.e., chemotaxis, could not be observed in the cell lines investigated. Additionally, the mRNA level of TNF-alpha was up-regulated by the cytokine treatment, which points to an autocrine loop augmenting and/or stabilizing the TNF-alpha-MCP-1 pathway. In summary, our data clearly support additional investigations using anti-MCP-1 antibodies in myeloma progression.

Cell proliferation of myeloma plasma cells: comparison of the blood and marrow compartments

The plasma cell labeling Index (PCLI), a measure of marrow plasma cells in S phase of the cell cycle, provides a good estimate of the proliferative capacity of the malignant clonal plasma cells. Multiple studies have also demonstrated its prognostic value in multiple myeloma (MM). Clonal plasma cells have been demonstrated in the peripheral blood of patients with multiple myeloma. The labeling index of these circulating cells can also be determined by a method similar to that employed for marrow plasma cells. The goal of this study was to compare the proliferation kinetics of plasma cells in the marrow to that in the circulation. The PCLI was estimated on peripheral blood (PBLI) and bone marrow aspirates (BMLI) using a slide-based bromodeoxyuridine (BrdU) immunofluorescence microscopy technique. One hundred seventeen patients who had simultaneous estimation of the PBLI and BMLI and who had > or =90% of the blood cIg+ cells identified as monoclonal plasma cells were studied. The PBLI was generally lower than the BMLI (median difference 0.4) and correlated with the BMLI (rho = 0.491, P < 0.0001). Twenty-seven patients with PBLI higher than BMLI had a poorer prognosis, with median survival of 2 months from the time of the labeling index determination, compared to 12 months for the remaining 90 patients (P = 0.01). Myeloma plasma cells circulating in the peripheral blood are capable of proliferation, albeit at a slower rate compared to those in the marrow. These differences reflect a more favorable microenvironment in the marrow likely resulting from the differences in the cytokine levels and supporting stromal cells in the marrow.

The protein tyrosine phosphatase CD45 is required for interleukin 6 signaling in U266 myeloma cells

The objective of this study was to examine whether CD45 mediates interleukin 6 (IL-6) signaling in human multiple myeloma (MM) cells. We chose U266 MM cells as a study model and isolated cells into CD45+ and CD45- subpopulations. CD45+ and CD45- U266 cells were cocultured with bone marrow stromal cells (BMSCs). IL-6-induced proliferation in CD45+ U266 cells was inhibited by vanadate, a potent protein tyrosine phosphatase inhibitor. However, IL-6-independent CD45- U266 cell growth was not affected by vanadate. CD45+ U266 cells, but not CD45- U266 cells, have the capability of cell adhesion concomitant with actin filament polymerization at the adherent cells. Adhesion of CD45+ U266 cells to BMSCs was impaired by vanadate. We clarified the signaling differences between CD45+ and CD45- U266 cells in response to IL-6. In CD45+ U266 cells, IL-6 increased tyrosine phosphorylation of gp130 and STAT3 and stimulated the level of Mcl-1 protein expression. An association between CD45 and the Src-family protein tyrosine kinase, Lyn, was maintained in the presence of IL-6; the formation of the CD45/Lyn complex was impaired by vanadate. Additionally, IL-6-induced Lyn kinase activity in CD45+ U266 cells was increased by the cross-linking of CD45, and this increase was due to the dephosphorylation of Tyr507 at Lyn. In conclusion, IL-6-dependent MM cells require CD45 to initiate IL-6 signaling and to maintain Lyn kinase activity, both of which are essential for cell proliferation and cell adhesion.

Expression of VEGF and its receptors by myeloma cells

Angiogenesis or new vessel formation is an essential component in the growth and progression of neoplasms and there is growing evidence of its importance in hematological malignancies including multiple myeloma (MM). Vascular endothelial growth factor (VEGF) is believed to play a role in tumor angiogenesis. We studied the expression of VEGF and its receptors (VEGFR1 or Flt-1 and VEGFR2 or Flk-1/KDR) by myeloma cell lines and plasma cells isolated from patients, using different methods. VEGF expression by the plasma cells was demonstrated by immunohistochemistry in 18 of 20 patients with MM. Enzyme-linked immunosorbent assay demonstrated VEGF secretion in all six different myeloma cell lines studied. Five patient marrow samples and seven different myeloma cell lines were then studied for VEGF mRNA expression by reverse-transcriptase polymerase chain reaction (RT-PCR), which was positive in all. We further evaluated the expression of both VEGFR1 and VEGFR2 in different myeloma cell lines and five sorted myeloma bone marrow samples by RT-PCR. All the myeloma cell lines expressed VEGFR1 and three of the cell lines expressed VEGFR2. VEGFR1 expression was detected in all and VEGFR2 in all but one of the sorted marrow samples. Increased expression of VEGF by the myeloma cells taken in the context of the suspected prognostic value of marrow angiogenesis suggests a pathogenetic role for this cytokine and presence of its receptors on myeloma cells points toward an autocrine mechanism. Demonstration of the presence of VEGFR2 in our study provides a potential biological explanation for the preclinical activity observed with VEGFR2 inhibitors.

Paracrine interactions of basic fibroblast growth factor and interleukin-6 in multiple myeloma

Myeloma cells express basic fibroblast growth factor (bFGF), an angiogenic cytokine triggering marrow neovascularization in multiple myeloma (MM). In solid tumors and some lymphohematopoietic malignancies, angiogenic cytokines have also been shown to stimulate tumor growth via paracrine pathways. Since interleukin-6 (IL-6) is a potent growth and survival factor for myeloma cells, we have studied the effects of bFGF on IL-6 secretion by bone marrow stromal cells (BMSCs) and its potential reverse regulation in myeloma cells. Both myeloma-derived cell lines and myeloma cells isolated from the marrow of MM patients were shown to express and secrete bFGF. Cell-sorting studies identified myeloma cells as the predominant source of bFGF in MM marrow. BMSCs from MM patients and control subjects expressed high-affinity FGF receptors R1 through R4. Stimulation of BMSCs with bFGF induced a time- and dose-dependent increase in IL-6 secretion (median, 2-fold; P <.001), which was completely abrogated by anti-bFGF antibodies. Conversely, stimulation with IL-6 enhanced bFGF expression and secretion by myeloma cell lines (2-fold; P =.02) as well as MM patient cells (up to 3.6-fold; median, 1.5-fold; P =.002). This effect was inhibited by anti-IL-6 antibody. When myeloma cells were cocultured with BMSCs in a noncontact transwell system, both IL-6 and bFGF concentrations in coculture supernatants increased 2- to 3-fold over the sum of basal concentrations in the monoculture controls. The IL-6 increase was again partially, but significantly, inhibited by anti-bFGF. The data demonstrate a paracrine interaction between myeloma and marrow stromal cells triggered by mutual stimulation of bFGF and IL-6.

Expression of interleukin-6, leukemia inhibitory factor and their receptors by colonic epithelium and pericryptal fibroblasts

BACKGROUND AND AIM

The cellular configuration of the human colon suggests a predetermined organization that creates specific microenvironments. The role of pericryptal fibroblasts in this microenvironment has been the subject of considerable speculation. This study examined the expression of growth factors and their receptors by colonic crypt epithelium and pericryptal fibroblasts.

METHODS AND RESULTS

Pericryptal fibroblast cells were isolated and cultured from decrypted human colonic mucosa. The pericryptal fibroblast cells expressed messenger RNA (mRNA) for interleukin-6 (IL-6), leukemia inhibitory factor (LIF), LIF receptor alpha, and the common coreceptor glycoprotein 130 (GP130), but not the IL-6 receptor alpha. Interleukin-6 protein expression was confirmed by the analysis of conditioned medium and immunohistochemistry. In comparison, normal colonic epithelial cells express mRNA for LIF but not IL-6 as well as the receptors for GP-130, IL-6 receptor alpha but not LIF receptor alpha. As cultures of normal human colonic epithelial cells were not available, the conditioned medium was assayed from established colon carcinoma cell lines and demonstrated a secretion of LIF but not IL-6 protein.

CONCLUSION

The expression of reciprocal cytokine and receptor expression suggest that there is a paracrine relationship between pericryptal fibroblasts and colonic epithelium.

The IL-6 receptor antagonist SANT-7 overcomes bone marrow stromal cell-mediated drug resistance of multiple myeloma cells

The bone marrow micro-environment produces a number of different survival factors that are important for the malignant growth and drug resistance of multiple myeloma (MM) cells. One of the main factors reported to be essential for survival and growth of MM cells in some experimental systems is IL-6. Therefore, the development and testing of substances that interfere with IL-6 or IL-6 receptor (IL-6R) function might have therapeutic value for the treatment of MM. We analyzed the effect of the IL-6R antagonist SANT-7 on growth and survival of the IL-6--dependent MM cell lines INA-6 and XG-1 as well as primary MM cells from 7 patients co-cultured with bone marrow stromal cells (BMSCs). In particular, we were interested in whether SANT-7 enhances the growth-inhibitory effects of dexamethasone (Dex) and all-trans-retinoic acid (ATRA). None of the drugs when tested as a single substance, including SANT-7, induced major growth inhibition if MM cells were co-cultured with primary human BMSCs. However, when Dex and ATRA were given in combination with SANT-7, strong growth inhibition was achieved in cell lines and primary MM cells. This effect was due to cell-cycle arrest and induction of apoptosis.

Biology of osteoclast activation in cancer

Bone is a frequent site of cancer metastasis. Bone metastases can result in bone destruction or new bone formation. Bone destruction is mediated by factors produced or induced by tumor cells that stimulate formation and activation of osteoclasts, the normal bone-resorbing cells. Local bone destruction also occurs in patients with osteoblastic metastases and may precede or occur simultaneously with increased bone formation. Several factors, including interleukin (IL)-1, IL-6, receptor activator of NF-kappaB (RANK) ligand, parathyroid hormone-related protein (PTHrP), and macrophage inflammatory protein-1-alpha (MIP-1alpha), have been implicated as factors that enhance osteoclast formation and bone destruction in patients with neoplasia. PTHrP seems to be the major factor produced by breast cancer cells that induces osteoclast formation through upregulation of RANK ligand. Enhanced RANK ligand expression also plays an important role in bone destruction in patients with myeloma. RANK ligand can act to enhance the effects of other factors produced by myeloma cells or in response to myeloma cells, such as MIP-1alpha and/or IL-6, to induce osteoclast formation. Understanding of the molecular mechanisms responsible for osteoclast activation in osteolytic metastases should lead to development of novel therapeutic approaches for this highly morbid and potentially fatal complication of cancer.

The promotion of plasmacytoma tumor growth by mesenchymal stroma is antagonized by basic fibroblast growth factor induced activin A

The mesenchymal stroma has been shown to play a crucial role in the development of multiple myeloma, partly by secretion of interleukin (IL)-6, that serves as a growth factor for myeloma cells. However, it is still unclear which other stromal molecules are involved in the pathogenesis of this disease. We chose, as a model system, a mouse plasmacytoma cell line, which does not respond to IL-6. We found that the formation of mouse plasmacytoma tumors, in an in vivo skin transplantation model, is facilitated by co-injection of these tumor cells along with a mesenchymal stromal cell. The tumor promoting effect of the stroma was reproduced in an in vitro model; stromal cells induced the proliferation of plasmacytoma cells under serum-free conditions. This growth promotion could not be mimicked by a series of cytokines including IL-6 and insulin-like growth factor (IGF)-I implying a role for yet unidentified stromal factors. The in vivo formation of plasmacytoma tumors was reduced following administration of activin A, a cytokine member of the transforming growth factor (TGF)beta superfamily. Furthermore, the in vitro growth promoting effect of the stroma was abrogated by basic fibroblast growth factor (bFGF) which induced a higher stromal expression of activin A. Our results thus show that mesenchymal stroma expresses plasmacytoma growth stimulating activities that overcome the low constitutive level of the plasmacytoma inhibitor, activin A. The expression of activin A is upregulated by bFGF rendering the stroma suppressive for plasmacytoma growth. The balance between the expression of these regulators may contribute to mesenchymal stroma activity and influence the progression of multiple myeloma.

Myeloma bone disease

Bone destruction is a hallmark of myeloma, with 70% to 80% of patients manifesting bone involvement. Destruction is mediated through normal osteoclasts (OCLs), which respond to local osteoclast-activating factors (OAFs) produced by myeloma cells or by other cells in the local microenvironment. OAFs implicated in myeloma bone disease include tumor necrosis factor-beta (TNFbeta), RANK ligand (RANKL), interleukin-1 (IL-1), parathyroid hormone-related protein (PTHrP), hepatocyte growth factor (HGH), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFalpha), and macrophage inflammatory protein-1-alpha (MIP-1alpha). To date, the leading candidates for OAFs are MIP-1alpha and RANKL. Adhesive interactions between marrow stromal cells and myeloma cells induce marrow stromal cells to secrete IL-6, a potent myeloma growth/survival factor that may contribute to the bone disease. Evaluation of myeloma bone disease includes plain radiographs, and newer methods, such as magnetic resonance imaging (MRI), positron emission tomography (PET) scans, technetium-99m-sestamibi (Mibi) scanning, and dual-energy x-ray absorptiometry (DEXA) scanning, may provide more complete information. In addition, biochemical markers of bone resorption are being evaluated, although the limited availability of these assays and lack of extensive testing in patients make their routine use premature. Treatment of myeloma bone disease includes radiation therapy, vertebroplasty, surgery, and bisphosphonates. New developments on the pathogenesis and treatment of myeloma bone disease present great opportunities to combat bone disease.

Acute activation of gp130 gene expression in bone marrow stromal cells by contact with myeloma-derived lymphoblastic cell line ARH77 cell membranes

Cell-cell contact of myeloma-derived cell lines (MDCL) or fresh myeloma cells with bone marrow stromal cells (BMSC) is known to induce interleukin-6 (IL-6) and matrix metalloproteinase-1 (MMP-1) production by a marrow stromal cell line. To determine if other BMSC transcripts are altered during cell-cell contact between BMSC and tumor cells, we have used cell lines ARH77 and U266 in an in vitro model. Using mRNA differential display and reverse transcriptase-polymerase chain reaction (RT-PCR), it was determined that a total of 141 transcripts were either upregulated or downregulated in the BMSC on contact with cell membrane from cell lines ARH77 and U266. Induction of two of these transcripts, interleukin-6 (IL-6) and gp130 in the BMSC by ARH77 cell membranes was studied in greater detail. Real-time PCR was used to quantitate transcript levels of gp130, IL-6, and 36b4, a housekeeping gene. Cycloheximide (CHX) alone increased both gp130 and IL-6 transcripts in the BMSC. In addition, CHX caused a superinduction of these transcripts in BMSC exposed to ARH77 cell membranes. The induction of gp130 was independent of the increase in IL-6 mRNA. Upregulation of gp130, a component of the membrane receptors for the IL-6 superfamily, can have profound effects on the response of BMSC to the IL-6 superfamily of cytokines.

The tumor microenvironment as a determinant of cancer cell survival: a possible mechanism for de novo drug resistance

The influence of the microenvironment in the pathogenesis and progression of human cancer has traditionally been considered in the context of solid tumors. More recently, evidence has been accumulating to support the role of the bone marrow microenvironment in hematologic malignancies as well, particularly in multiple myeloma. This review focuses on myeloma as a model to demonstrate that the bone marrow microenvironment provides a sanctuary against programmed cell death and promotes tumor cell survival and progression. Additionally, the protective effects of the bone marrow milieu may confer a protection from cytotoxic drugs, allowing the emergence of drug-resistant tumors. These advances may assist in the design of novel therapeutic approaches to enhance the efficacy of standard chemotherapeutic drugs.

Vascular endothelial growth factor and interleukin-6 in paracrine tumor-stromal cell interactions in multiple myeloma

Vascular endothelial growth factor (VEGF), a multifunctional cytokine, potently stimulates angiogenesis including tumor neovascularization. Although well established in solid tumors, the role of VEGF in bone marrow neoangiogenesis and paracrine tumor-stromal cell interactions in lymphohematopoietic malignancies has not been fully elucidated. In multiple myeloma (MM), marrow neovascularization parallels disease progression. This parallel prompted us to investigate the expression and secretion of VEGF by myeloma cells and its potential effects in myeloma-marrow stroma interactions. The biologically active splice variants VEGF165 and VEGF121 were expressed and secreted by myeloma cell lines and plasma cells isolated from the marrow of patients with MM. As shown by immunocytochemistry or RT-PCR, myeloma cells did not express or weakly expressed the VEGF receptors FLT-1 and FLK-1/KDR, indicating that autocrine stimulation is unlikely. In contrast, FLK-1/KDR was abundantly expressed by marrow stromal cells. Therefore, we studied the effects of VEGF on marrow stroma, focusing on the secretion of interleukin-6 (IL-6), a potent growth factor for myeloma cells and an inhibitor of plasma cell apoptosis. Exposure of stromal and microvascular endothelial cells to recombinant human (rh) VEGF165 or VEGF121 induced a time- and dose-dependent increase in IL-6 secretion (14- to 27-fold at 50 ng/mL after 24 hours, P &lt; .001). Conversely, rhIL-6 stimulated VEGF expression and secretion in myeloma cell lines (40%-60%; P &lt; .05) and to a variable degree (up to 5.3-fold; P &lt; .005) in plasma cells purified from the marrow of patients with MM. This mutual stimulation suggests paracrine interactions between myeloma and marrow stromal cells triggered by VEGF and IL-6.

Vascular endothelial growth factor and interleukin-6 in paracrine tumor-stromal cell interactions in multiple myeloma

Vascular endothelial growth factor (VEGF), a multifunctional cytokine, potently stimulates angiogenesis including tumor neovascularization. Although well established in solid tumors, the role of VEGF in bone marrow neoangiogenesis and paracrine tumor-stromal cell interactions in lymphohematopoietic malignancies has not been fully elucidated. In multiple myeloma (MM), marrow neovascularization parallels disease progression. This parallel prompted us to investigate the expression and secretion of VEGF by myeloma cells and its potential effects in myeloma-marrow stroma interactions. The biologically active splice variants VEGF165 and VEGF121 were expressed and secreted by myeloma cell lines and plasma cells isolated from the marrow of patients with MM. As shown by immunocytochemistry or RT-PCR, myeloma cells did not express or weakly expressed the VEGF receptors FLT-1 and FLK-1/KDR, indicating that autocrine stimulation is unlikely. In contrast, FLK-1/KDR was abundantly expressed by marrow stromal cells. Therefore, we studied the effects of VEGF on marrow stroma, focusing on the secretion of interleukin-6 (IL-6), a potent growth factor for myeloma cells and an inhibitor of plasma cell apoptosis. Exposure of stromal and microvascular endothelial cells to recombinant human (rh) VEGF165 or VEGF121 induced a time- and dose-dependent increase in IL-6 secretion (14- to 27-fold at 50 ng/mL after 24 hours, P < .001). Conversely, rhIL-6 stimulated VEGF expression and secretion in myeloma cell lines (40%-60%; P < .05) and to a variable degree (up to 5.3-fold; P < .005) in plasma cells purified from the marrow of patients with MM. This mutual stimulation suggests paracrine interactions between myeloma and marrow stromal cells triggered by VEGF and IL-6.