The involvement of adhesion molecules in the biology of multiple myeloma

CD38 x ICAM-1 Bispecific Antibody Is a Novel Approach for Treating Multiple Myeloma and Lymphoma

The cluster of differentiation 38 (CD38) is a well-validated target for treating multiple myeloma. Although anti-CD38 mAbs have demonstrated outstanding initial responses in patients with multiple myeloma, nearly all patients eventually develop resistance and relapse. In addition, currently approved CD38 targeting therapies have failed to show monotherapy efficacy in lymphomas, where CD38 expression is present but at lower levels. To effectively target CD38 on tumor cells, we generated an antibody-dependent cellular cytotoxicity (ADCC) enhanced bispecific CD38 x intercellular cell adhesion molecule 1 (ICAM-1) antibody, VP301. This bispecific antibody targets unique epitopes on CD38 and ICAM-1 on tumor cells with reduced red blood cell binding compared with the benchmark CD38 antibody daratumumab. VP301 demonstrated potent ADCC and antibody-dependent cellular phagocytosis activities on a selected set of myeloma and lymphoma cell lines even those with low CD38 expression. In an ex vivo drug sensitivity assay, we observed responses to VP301 in multiple myeloma primary samples from relapsed/refractory patients. Moreover, VP301 demonstrated potent tumor inhibition activities in in vivo myeloma and lymphoma models. Interestingly, combination of VP301 with the immunomodulatory drug, lenalidomide, led to synergistic antitumor growth activity in an in vivo efficacy study. In conclusion, the CD38 x ICAM-1 bispecific antibody VP301 demonstrated promising efficacy and specificity toward CD38+ and ICAM-1+ tumor cells and represents a novel approach for treating multiple myeloma and lymphoma.

Adhesion molecules in multiple myeloma oncogenesis and targeted therapy

Every day we march closer to finding the cure for multiple myeloma. The myeloma cells inflict their damage through specialized cellular meshwork and cytokines system. Implicit in these interactions are cellular adhesion molecules and their regulators which include but are not limited to integrins and syndecan-1/CD138, immunoglobulin superfamily cell adhesion molecules, such as CD44, cadherins such as N-cadherin, and selectins, such as E-selectin. Several adhesion molecules are respectively involved in myelomagenesis such as in the transition from the precursor disorder monoclonal gammopathy of undetermined significance to indolent asymptomatic multiple myeloma (smoldering myeloma) then to active multiple myeloma or primary plasma cell leukemia, and in the pathological manifestations of multiple myeloma.

Pulsatilla saponin A Induces Apoptosis and Differentiation of Myeloma Cells

OBJECTIVES

To investigate the performance of Pulsatilla saponin A (PsA) in Multiple Myeloma (MM) cells.

METHODS

Proliferation, cell cycle analysis, apoptosis and TUNEL assays were conducted to detect the growth and apoptosis in MM cells. Western blotting was used to identify the change in the protein.

RESULTS

In cell assays, PsA significantly inhibited the growth and apoptosis in MM cells. Cyclin B1, caspase-3, cleaved-caspase-3, PARP, cleaved-PARP, p-ERK increased, while Bcl-2 decreased after PSA treatment. The CD49e positive rate of U266 cells was increased after 96h PsA treatment. At the same time, immunoglobulin and the Free Light Chain (FLC) ratio in the culture supernatant obviously increased. Also, the differentiation induced by PsA was confirmed in the primary myeloma cells.

CONCLUSION

Our findings reveal that PsA may exert its antitumor effect by causing G2 arrest and apoptosis in myeloma cells. And low-dose PsA can induce the differentiation of myeloma cell lines and primary myeloma cells, probably through the MEK/ERK signaling pathway in vitro.

Facts and Hopes in Multiple Myeloma Immunotherapy

Among the hallmarks of cancer is the ability of neoplastic cells to evade and suppress immune surveillance to allow their growth and evolution. Nowhere is this as apparent as in multiple myeloma, a cancer of antibody-producing plasma cells, where a complex interplay between neoplastic cells and the immune microenvironment is required for the development and progression of disease. Decades of research has led to the discovery of a number of therapeutic agents, from cytotoxic drugs to genetically engineered cells that mediate their antimyeloma effects at least partially through altering these immune interactions. In this review, we discuss the history of immunotherapy and current practices in multiple myeloma, as well as the advances that promise to one day offer a cure for this deadly disease.

Tellurium compound provides pro-apoptotic signaling in drug resistant multiple myeloma

Multiple Myeloma, effectively treated by chemotherapeutic drugs, relapses due to drug resistance. We tested here the capacity of mesenchymal stromal cells, from the bone marrow of patients or from adipose tissue of healthy individuals, to induce drug resistance in Myeloma cell lines. We show that drug resistance can be achieved by factors secreted by the various MSC's. Mass spectrometry analysis of MSC's conditioned media revealed that fibronectin, was particularly instrumental in providing anti-apoptotic signals to MM cells. Moreover, we demonstrate that SAS ([octa-O-bis-(R,R)tartarate ditellurane]), an immunomodulator Tellurium compound, is not only able of blocking the physical interaction between MM cells and fibronectin but is also capable of re-sensitizing the cells to the chemotherapeutic drugs. Finally, we show that this re-sensitization is coupled with the blocking of pAKT induction, in MM cells, by the MSC's. These results indicate that SAS may be useful in the treatment of drug resistant MM.

Potent Activity of an Anti-ICAM1 Antibody-Drug Conjugate against Multiple Myeloma

PURPOSE

New therapies have changed the outlook for patients with multiple myeloma, but novel agents are needed for patients who are refractory or relapsed on currently approved drug classes. Novel targets other than CD38 and BCMA are needed for new immunotherapy development, as resistance to daratumumab and emerging anti-BCMA approaches appears inevitable. One potential target of interest in myeloma is ICAM1. Naked anti-ICAM1 antibodies were active in preclinical models of myeloma and safe in patients, but showed limited clinical efficacy. Here, we sought to achieve improved targeting of multiple myeloma with an anti-ICAM1 antibody-drug conjugate (ADC).

EXPERIMENTAL DESIGN

Our anti-ICAM1 human mAb was conjugated to an auristatin derivative, and tested against multiple myeloma cell lines in vitro, orthotopic xenografts in vivo, and patient samples ex vivo. The expression of ICAM1 was also measured by quantitative flow cytometry in patients spanning from diagnosis to the daratumumab-refractory state.

RESULTS

The anti-ICAM1 ADC displayed potent anti-myeloma cytotoxicity in vitro and in vivo. In addition, we have verified that ICAM1 is highly expressed on myeloma cells and shown that its expression is further accentuated by the presence of bone marrow microenvironmental factors. In primary samples, ICAM1 is differentially overexpressed on multiple myeloma cells compared with normal cells, including daratumumab-refractory patients with decreased CD38. In addition, ICAM1-ADC showed selective cytotoxicity in multiple myeloma primary samples.

CONCLUSIONS

We propose that anti-ICAM1 ADC should be further studied for toxicity, and if safe, tested for clinical efficacy in patients with relapsed or refractory multiple myeloma.

Lymphocyte Subsets and Inflammatory Cytokines of Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

Almost all multiple myeloma (MM) cases have been demonstrated to be linked to earlier monoclonal gammopathy of undetermined significance (MGUS). Nevertheless, there are no identified characteristics in the diagnosis of MGUS that have been helpful in differentiating subjects whose cancer may progress to a malignant situation. Regarding malignancy, the role of lymphocyte subsets and cytokines at the beginning of neoplastic diseases is now incontestable. In this review, we have concentrated our attention on the equilibrium between the diverse lymphocyte subsets and the cytokine system and summarized the current state of knowledge, providing an overview of the condition of the entire system in MGUS and MM. In an age where the therapy of neoplastic monoclonal gammopathies largely relies on drugs capable of acting on the immune system (immunomodulants, immunological checkpoint inhibitors, CAR-T), detailed knowledge of the the differences existing in benign and neoplastic forms of gammopathy is the main foundation for the adequate and optimal use of new drugs.

Heparanase regulation of cancer, autophagy and inflammation: new mechanisms and targets for therapy

Because of its impact on multiple biological pathways, heparanase has emerged as a major regulator of cancer, inflammation and other disease processes. Heparanase accomplishes this by degrading heparan sulfate which regulates the abundance and location of heparin-binding growth factors thereby influencing multiple signaling pathways that control gene expression, syndecan shedding and cell behavior. In addition, heparanase can act via nonenzymatic mechanisms that directly activate signaling at the cell surface. Clinical trials testing heparanase inhibitors as anticancer therapeutics are showing early signs of efficacy in patients further emphasizing the biological importance of this enzyme. This review focuses on recent developments in the field of heparanase regulation of cancer and inflammation, including the impact of heparanase on exosomes and autophagy, and novel mechanisms whereby heparanase regulates tumor metastasis, angiogenesis and chemoresistance. In addition, the ongoing development of heparanase inhibitors and their potential for treating cancer and inflammation are discussed.

Multiple myeloma and persistence of drug resistance in the age of novel drugs (Review)

Multiple myeloma (MM) is a mature B cell neoplasm that results in multi-organ failure. The median age of onset, diverse clinical manifestations, heterogeneous survival rate, clonal evolution, intrinsic and acquired drug resistance have impact on the therapeutic management of the disease. Specifically, the emergence of multidrug resistance (MDR) during the course of treatment contributes significantly to treatment failure. The introduction of the immunomodulatory agents and proteasome inhibitors has seen an increase in overall patient survival, however, for the majority of patients, relapse remains inevitable with evidence that these agents, like the conventional chemotherapeutics are also subject to the development of MDR. Clinical management of patients with MM is currently compromised by lack of a suitable procedure to monitor the development of clinical drug resistance in individual patients. The current MM prognostic measures fail to pick the clonotypic tumor cells overexpressing drug efflux pumps, and invasive biopsy is insufficient in detecting sporadic tumors in the skeletal system. This review summarizes the challenges associated with treating the complex disease spectrum of myeloma, with an emphasis on the role of deleterious multidrug resistant clones orchestrating relapse.

Therapeutic targeting of N-cadherin is an effective treatment for multiple myeloma

Elevated expression of the cell adhesion molecule N-cadherin (cadherin 2, type 1, N-cadherin (neuronal); CDH2) is associated with poor prognosis in newly-diagnosed multiple myeloma (MM) patients. In this study, we investigated whether targeting of N-cadherin represents a potential treatment for the ~50% of MM patients with elevated N-cadherin. Initially, we stably knocked-down N-cadherin in the mouse MM plasma cell (PC) line 5TGM1 to assess the functional role of N-cadherin in MM pathogenesis. When compared with 5TGM1-scramble-shRNA cells, 5TGM1-Cdh2-shRNA cells had significantly reduced adhesion to bone marrow endothelial cells. However, N-cadherin knock-down did not affect 5TGM1 cell proliferation or adhesion to bone marrow stromal cells. In the C57BL/KaLwRij murine MM model, mice intravenously inoculated with 5TGM1-Cdh2-shRNA cells showed significantly decreased tumour burden after 4 weeks, compared with animals bearing 5TGM1-scramble-shRNA cells. Finally, the N-cadherin antagonist ADH-1 had no effect on tumour burden in the established disease setting, whereas up-front ADH-1 treatment resulted in significantly reduced tumour burden after 4 weeks. Our findings demonstrate that N-cadherin may play a key role in the extravasation of circulating MM PCs promoting bone marrow homing. Moreover, these studies suggest that N-cadherin may represent a viable therapeutic target to prevent the dissemination of MM PCs and delay MM disease progression.

Genistein inhibited proliferation and induced apoptosis in acute lymphoblastic leukemia, lymphoma and multiple myeloma cells in vitro

Genistein is one of the major isoflavones in soy products. It has been reported that genistein has apoptotic effects on certain hematological malignancies. However, so far there have been no completely comparative studies of the effect of genistein on malignant hematological diseases, especially multiple myeloma. We investigated genistein's inhibitory effect on the growth of acute lymphoblastic leukemia (RS4;11 and CEM), lymphoma (Toledo and GA10) and multiple myeloma (OPM-2 and U266) cell lines in vitro. We observed that genistein dose- and time-dependently inhibited proliferation of these cells. The cell line sensitivity to genistein treatment based on the 50% inhibitory concentration (IC(50)) values in decreasing order of toxicity was found to be as follows: RS4;11 (4.89 ± 4.28 μM) > GA10 (13.08 ± 3.49 μM) > Toledo (16.94 ± 3.89 μM) > CEM (17.31 ± 0.72 μM) > OPM-2 (46.76 ± 2.26 μM) > U266 (128.82 ± 1.90 μM). The mechanism of growth inhibition was through induction of apoptosis and cell cycle arrest. The concomitant altered expression of apoptosis pathway proteins and cell cycle modulators (caspases 9, 3, 7, PARP [poly(ADP-ribose) polymerase], cIAP1 [inhibitor of apoptosis protein 1], Bcl-2 and cyclin B1) were observed by Western blot and real-time polymerase chain reaction (PCR) analyses. In addition, some malignancy-related embryologic pathway proteins, e.g. Notch1 and Gli1, were modulated by genistein treatment in sensitive cell lines.

Extravasation and homing mechanisms in multiple myeloma

Multiple myeloma (MM) is a malignant B-cell disorder characterized by a monoclonal expansion of plasma cells (PC) in the bone marrow (BM). During the main course of disease evolution, MM cells depend on the BM microenvironment for their growth and survival. Reciprocal interactions between MM cells and the BM mediate not only MM cell growth, but also protect them against apoptosis and cause bone disease and angiogenesis. A striking feature of MM represents the predominant localization and retention of MM cells in the BM. Although BM PC indeed represent the main neoplastic cell type, small numbers of MM cells can also be detected in the peripheral blood circulation. It can be assumed that these circulating cells represent the tumour-spreading component of the disease. This implicates that MM cells have the capacity to (re)circulate, to extravasate and to migrate to the BM (homing). In analogy to the migration and homing of normal leucocytes, the BM homing of MM cells is mediated by a multistep process of extravasation with adhesion to the endothelium, invasion of the subendothelial basement membrane, followed by further migration within the stroma, mediated by chemotactic factors. At the end stage of disease, MM cells are thought to develop autocrine growth supporting loops that enable them to survive and proliferate in the absence of the BM microenvironment and to become stroma-independent. In this stage, the number of circulating cells increases and growth at extramedullary sites can occur, associated with alteration in adhesion molecule and chemokine receptor expression. This review summarizes the recent progress in the study of the extravasation and homing mechanisms of MM cells.

Wnt3/RhoA/ROCK signaling pathway is involved in adhesion-mediated drug resistance of multiple myeloma in an autocrine mechanism

Adhesion of myeloma cells to bone marrow stromal cells is now considered to play a critical role in chemoresistance. However, little is known about the molecular mechanism governing cell adhesion-mediated drug resistance (CAM-DR) of myeloma cells. In this study, we focused our interests on the implication of the Wnt signal in CAM-DR. We first screened the expression of Wnt family in myeloma cell lines and found that Wnt3 was overexpressed in all the myeloma cells examined. KMS-5 and ARH77, which highly expressed Wnt3 protein, tightly adhered to human bone marrow stromal cells, and accumulation of beta-catenin and GTP-bounded RhoA was observed in these myeloma cell lines. Conversely, RPMI8226 and MM1S, which modestly expressed Wnt3 protein, rather weakly adhered to human bone marrow stromal. We then examined the relevance of Wnt3 expression to adhesive property to stromal cells and to CAM-DR of myeloma cells. KMS-5 and ARH-77 exhibited apparent CAM-DR against doxorubicin. This CAM-DR was significantly reduced by anti-integrin beta(1) antibody, anti-integrin alpha(6) antibody and a Wnt-receptor competitor, secreted Frizzled-related protein-1, and Rho kinase inhibitor Y27632, but not by the specific inhibitor of canonical signaling (Dickkopf-1), indicating that Wnt-mediated CAM-DR that is dependent on integrin alpha(6)/beta(1) (VLA-6)-mediated attachment to stromal cells is induced by the Wnt/RhoA/Rho kinase pathway signal. This CAM-DR was also significantly reduced by Wnt3 small interfering RNA transfer to KMS-5. These results indicate that Wnt3 contributes to VLA-6-mediated CAM-DR via the Wnt/RhoA/ROCK pathway of myeloma cells in an autocrine manner. Thus, the Wnt3 signaling pathway could be a promising molecular target to overcome CAM-DR of myeloma cells.

Oncolytic Coxsackievirus A21 as a novel therapy for multiple myeloma

Oncolytic viruses are attractive biological agents for the control of human malignancy. This study assessed the capacity of Coxsackievirus A21 (CVA21) to target and destroy multiple myeloma (MM) and precursor aberrant plasma cells in vitro using established MM cell lines and 15 patient bone marrow (BM) biopsies [n = 10 MM and five monoclonal gammopathy of undetermined significance (MGUS)]. Cell surface analysis revealed that all tumour cells lines expressed high levels of intercellular adhesion molecule-1 (ICAM-1) and decay-accelerating factor (DAF), the receptor molecules to which CVA21 can bind, leading to subsequent cell-entry and infection. MM cell lines were remarkably susceptible to CVA21 lytic infection, producing 100-1000-fold increases in viral progeny within 24 h. In contrast, normal peripheral blood cells were refractile to CVA21 infection. Furthermore, challenge of patient BM biopsies with CVA21 for 48 h resulted in specific purging of up to 98.7% of CD138+ plasma cells, with no significant decrease in progenitor cell function. Data generated in this study suggests that CVA21 virotherapy may have potential applications as a systemic anti-tumour agent for MM, or in the ex vivo purging of malignant plasma cells prior to autologous stem cell transplantation.

Role of CCR1 and CCR5 in homing and growth of multiple myeloma and in the development of osteolytic lesions: a study in the 5TMM model

Multiple myeloma (MM) is a plasma cell malignancy, characterized by the localization of the MM cells in the bone marrow (BM), where they proliferate and induce osteolysis. The MM cells first need to home or migrate to the BM to receive necessary survival signals. In this work, we studied the role of CCR1 and CCR5, two known chemokine receptors, in both chemotaxis and osteolysis in the experimental 5TMM mouse model. A CCR1-specific (BX471) and a CCR5-specific (TAK779) antagonist were used to identify the function of both receptors. We could detect by RT-PCR and flow cytometric analyses the expression of both CCR1 and CCR5 on the cells and their major ligand, macrophage inflammatory protein 1alpha (MIP1alpha) could be detected by ELISA. In vitro migration assays showed that MIP1alpha induced a 2-fold increase in migration of 5TMM cells, which could only be blocked by TAK779. In vivo homing kinetics showed a 30% inhibition in BM homing when 5TMM cells were pre-treated with TAK779. We found, in vitro, that both inhibitors were able to reduce osteoclastogenesis and osteoclastic resorption. In vivo end-term treatment of 5T2MM mice with BX471 resulted in a reduction of the osteolytic lesions by 40%; while TAK779 treatment led to a 20% decrease in lesions. Furthermore, assessment of the microvessel density demonstrated a role for both receptors in MM induced angiogenesis. These data demonstrate the differential role of CCR1 and CCR5 in MM chemotaxis and MM associated osteolysis and angiogenesis.

Inhibiting the IGF-1 receptor tyrosine kinase with the cyclolignan PPP: an in vitro and in vivo study in the 5T33MM mouse model

Insulin-like growth factor 1 (IGF-1) plays a pleiotropic role in multiple myeloma (MM), that is, in survival, proliferation, chemotaxis, and angiogenesis. Strategies targeting the IGF-1 receptor (IGF-1R) may therefore be important to develop efficient anti-MM agents. In this work we investigated the effect of an IGF-1R tyrosine kinase (IGF-1RTK) inhibitor (picropodophyllin or PPP) in the 5T33MM mouse model. In vitro data showed that PPP reduced IGF-1R autophosphorylation and downstream ERK activation, leading to inhibition of IGF-1–stimulated proliferation and vascular endothelial growth factor (VEGF) secretion of MM cells. In an in vivo study, PPP reduced the bone marrow tumor burden and serum paraprotein in 5T33MM mice by 77% and 90%, respectively, compared to vehicle-treated animals. Angiogenesis was assessed by quantifying the microvessel density on CD31-stained paraffin sections and this was reduced by 60% in the PPP-treated group. In a separate survival experiment, Kaplan-Meier analysis demonstrated a significant increase in survival in PPP-treated 5T33MM animals compared to the vehicle controls (28 versus 18 days). These data suggest that the IGF-1RTK inhibitor PPP possesses a marked antitumor activity and strongly points to the possibility of using IGF-1R inhibitors in the treatment of MM.

2-Methoxyestradiol at low dose induces differentiation of myeloma cells

Previous studies showed that 2-methoxyestradiol (2ME2) could suppress the proliferation of myeloma cells and induce their apoptosis. In the present study, we found that treatments with low-concentration of 2ME2 resulted in some maturing morphological changes of myeloma cells. Flow cytometric analysis showed that the expression of CD49e on the myeloma cells surface was significantly increased by 2ME2. Moreover, 2ME2 increased the secretion of light chain protein remarkably. Furthermore, the expressions of transcription factor XBP-1 mRNA and protein were also up-regulated. These results demonstrated that 2ME2 at low-concentration could induce differentiation of the myeloma cells, which would provide a new, safe strategy for myeloma therapy.

Myeloma cells (5TMM) and their interactions with the marrow microenvironment

Myeloma is a deadly B-cell neoplasm, characterized by the monoclonal proliferation of plasma cells, the development of osteolytic lesions, and the induction of angiogenesis. Myeloma cells are predominantly localized in the marrow where they receive the appropriate survival and proliferation signals. To reach or spread over the marrow, the myeloma cells need to migrate from the vascular to the extravascular compartment of the marrow. A process called "homing". In this review, the steps of the homing scheme, analyzed in the 5TMM model, will be described. These murine models originated from spontaneously developed myeloma in elderly mice and have since been propagated by intravenous injection of myeloma cells into young syngeneic mice. These models resemble the human condition closely. The different studies reported here demonstrate that adhesion of 5TMM cells to marrow endothelial cells is partially mediated by CD44v10 and to stromal cells by CD44v6. The 5TMM cells migrate to the marrow through the effects of MCP-1, laminin-1, and IGF-1. Once past the marrow endothelium, they invade the extravascular compartment of the marrow by secreting MMP-9 and uPA. When they have settled in the marrow, they become susceptible to the effects of IGF-1, which stimulates the cells to proliferate and produce VEGF. Furthermore, studies targeting the marrow with inhibitors will be highlighted. These studies show that the 5TMM models are useful for unraveling basic biological processes and for identifying new therapeutic targets.

Clinical significance of circulating endothelial adhesion molecules (sE-selectin and sICAM) in untreated multiple myeloma patients

BACKGROUND

The expression of adhesion molecules is important for the interaction of myeloma cells with the bone marrow microenvironment. In the current study, serum soluble adhesion molecules (sICAM-1 and sE-selectin) were measured in untreated multiple myeloma (MM) patients in relation with other markers of disease activity.

MATERIALS AND METHODS

The study group consisted of 67 patients with MM (classified according to the Durie-Salmon classification) and 15 controls. Interleukin-6 (IL-6), sICAM-1 and sE-selectin concentrations were determined by enzyme-linked immunosorbent assay (ELISA). In addition, the monoclonal protein, erythrocyte sedimentation rate (ESR) and hemoglobin (Hb) concentration were also determined.

RESULTS

Serum sICAM-1 level increased significantly at advanced stages of MM and was higher in comparison to controls (p<0.01). sE-selectin increased significantly with advancing stage of the disease, but did not differ from controls. IL-6, ESR and M-component were significantly higher and Hb concentrations lower with advancing stage of disease. There was a positive correlation of IL-6 with sICAM-1 and sE-selectin.

CONCLUSIONS

We conclude that serum sICAM-1 differs in multiple myeloma patients from normals and together with sE-selectin increase in parallel to increasing stage of disease, which may reflect a dysregulation and possible involvement of these adhesion molecules in myeloma progression.

Specific roles for the PI3K and the MEK-ERK pathway in IGF-1-stimulated chemotaxis, VEGF secretion and proliferation of multiple myeloma cells: study in the 5T33MM model

Insulin-like growth factor-1 (IGF-1) has been described as an important factor in proliferation, cell survival and migration of multiple myeloma (MM) cells. Angiogenesis correlates with development and prognosis of the MM disease. Vascular endothelial growth factor (VEGF) is one of the prominent factors involved in this process. The different functions of IGF-1 were investigated in the 5TMM mouse model with emphasis on proliferation, migration and VEGF secretion, and the signalling pathways involved. Western Blot analysis revealed that ERK1/2 and Akt (PKB) were activated after IGF-1 stimulation. The activation of ERK1/2 was reduced by the PI3K inhibitor Wortmannin, implying that the PI3K pathway is involved in its activation. Insulin-like growth factor-1 induced an increase in DNA synthesis in MM cells, which was mediated by a PI3K/Akt-MEK/ERK pathway. Insulin-like growth factor-1 enhanced F-actin assembly and this process was only PI3K mediated. Stimulation by IGF-1 of VEGF production was reduced by PD98059, indicating that only the MEK–ERK pathway is involved in IGF-1-stimulated VEGF production. In conclusion, IGF-1 mediates its multiple effects on MM cells through different signal transduction pathways. In the future, we can study the potential in vivo effects of IGF-1 inhibition on tumour growth and angiogenesis in MM.

The F-actin content of multiple myeloma cells as a measure of their migration

One of the main characteristics of multiple myeloma (MM) cells is their specific homing and growth in the bone marrow (BM). For their homing, MM cells need chemotactic signals to be attracted towards the BM and to be activated. Profound knowledge of the different chemokines for MM cells and their signal transduction pathways is necessary to interfere in this process. We studied here an extra possible tool for the investigation of the different chemokines and their pathways. The 5T experimental mouse model was used to investigate the migration of MM cells towards BM stromal cells. We studied the changes of the F-actin content in the 5TMM cells in the presence of BM stromal cell conditioned medium and we correlated this with their migratory capacity. F-actin became polarized when the cells were migrating, in contrast to nonmigrating cells. This polarization could not only be seen by fluorescence and confocal laser scanning microscopy, but also could be quantified by fluorometry and flow cytometry. The correlation between the F-actin content of the MM cells and their migration capacity thus makes its quantification a useful tool in studying their migratory behavior.

Serum bone sialoprotein as a marker of tumour burden and neoplastic bone involvement and as a prognostic factor in multiple myeloma

To test the potential of immunoreactive BSP, a non-collagenous bone matrix component, as a clinical guide in patients with plasma cell dyscrasias, serum BSP concentrations were measured in 62 patients with newly diagnosed multiple myeloma (MM) followed over a period of 4 years, in 46 patients with monoclonal gammopathy of undetermined significance (MGUS), in 71 patients with untreated benign vertebral osteoporosis (OPO), and in 139 healthy adults. Results were compared with clinical and laboratory data, including serum osteocalcin (OC), and urinary pyridinoline (PYD) and deoxypyridinoline (DPD) as markers of bone turnover. In MM, serum BSP, and urinary PYD and DPD were higher than in healthy controls and in MGUS or OPO (P< 0.001). BSP levels correlated with the bone marrow plasma cell content (r = 0.40, P< 0.001), and serum beta2-microglobulin (r = 0.31, P < 0.01). The differentiation of MM from healthy controls and from MGUS or OPO was highest for BSP. After chemotherapy, BSP reflected the response to treatment and correlated with the change in monoclonal protein (r = 0.55, P< 0.001). MM patients with normal baseline BSP levels survived longer than patients with initially elevated BSP values (P< 0.001, log rank test). Only serum monoclonal protein and BSP were independent predictors of survival. We conclude that in MM, BSP levels are associated with skeletal involvement and tumour cell burden. The quantification of serum BSP may be a non-invasive method for the diagnosis and follow-up, and may improve the prognostic value of conventional staging in MM.

Malignant hematopoietic cell lines: in vitro models for the study of multiple myeloma and plasma cell leukemia

Multiple myeloma (MM) is a neoplasm of a terminally differentiated B-cell. The disease is progressive and always lethal characterized by the slow proliferation of malignant plasma cells in the bone marrow. Much of our current understanding of the biology of MM has been obtained by studying MM-derived cell lines. Human myeloma cell lines were shown to be suitable model systems for use in various fields of the biological sciences. However, it has proved very difficult to establish cell lines from plasma cell dyscrasias. Most reported MM cell lines have been derived from patients with advanced disease and from extramedullary sites. Nevertheless, within the last 20 years more than 100 cell lines have been established. A significant portion of this panel is partially or well characterized with regard to their cell culture, clinical, immunophenotypic, cytogenetic and functional features. Distinct immunoprofiles could be assigned to MM cell lines. All MM cell lines display chromosomal aberrations; in more than 80% of the cell lines analyzed, chromosome 14 band q32 (immunoglobulin heavy chain locus) is affected; the various types of 14q+ chromosomes showed different distributions among the MM cell lines. A large percentage of MM cell lines is constitutively interleukin-6-dependent or responsive to various cytokines. It is important to realize that not every cell line established from a patient with myeloma is a neoplastic cell line. So-called 'myeloma cell lines' have been previously reported and are still widely used which are in reality Epstein-Barr virus (EBV)-positive B-lymphoblastoid cell lines. The presence of the EBV-genome in residual normal B-cells provides them with a selective growth advantage after explantation. In summary, a significant number of authentic and well-characterized MM cell lines has been established and described. The availability of these bona fide MM cell lines is of great importance for the study of the biology, etiology and treatment of the disease.

Expression of CD44 isoforms on isolated bone marrow plasma cells and peripheral CD19+ B cells of patients with multiple myeloma and healthy individuals

The expression of certain isoforms of CD44 was shown to correlate with aggressiveness and metastatic potential of various tumour types. We analysed the expression of the adhesion molecule CD44 and its variant domains (v6, v7, v7/8, v10) on isolated bone marrow (BM) plasma cells and peripheral blood (PBL) CD19+ B cells of 21 patients with MM and 15 healthy donors. B cells and plasma cells were isolated by immunomagnetic sorting and analysed by two-colour flow cytometry. The expression of CD44 isoforms was significantly higher on PBL B cells of patients with MM than in healthy controls. The elevated expression of CD44 isoforms (v6, v7/8, v10) on PBL B cells correlated with reduced overall survival in MM. CD44 isoforms were more strongly expressed on "larger", activated B cells. Furthermore, CD44 isoforms were found to be simultaneously expressed with CD38hi and CD56 on both, B lymphocytes and plasma cells of patients with MM. The determination of CD44 isoforms on circulating B cells may be helpful in defining prognostically unfavourable subgroups in MM.

Insulin-Like Growth Factor-1 Acts as a Chemoattractant Factor for 5T2 Multiple Myeloma Cells

The chemotactic and growth-stimulatory effect of insulin-like growth factor 1 (IGF-1) was investigated in the experimental mouse 5T2 multiple myeloma (MM) model. Chemotaxis was analyzed by classical checkerboard analysis. Bone marrow fibroblasts–conditioned medium exhibited a chemotactic effect on 5T2 MM cells that could be neutralized by adding a blocking antibody to IGF-1. On the other hand, exogenously added IGF-1 also had a chemotactic effect on the 5T2 MM cells. Moreover, in vitro analysis demonstrated that transmigrated 5T2 MM cells have a higher expression of IGF-1 receptor, both in bone marrow–conditioned medium and in IGF-1–induced chemotaxis, in comparison to cells before migration. When analyzed in vivo, 18 hours after injection of the heterogeneous 5T2 MM population, 5T2 MM cells present in the bone marrow show a higher expression of the IGF-1 receptor than their counterparts before injection. When the proliferative effect of IGF-1 was analyzed, no stimulation was observed, which is in contrast to the influence of bone marrow–conditioned medium and interleukin-6. Our results suggest a causal relationship between the presence of IGF-1 in the bone marrow and the chemotaxis of MM cells to and their subsequent presence in the bone marrow.

Insulin-Like Growth Factor-1 Acts as a Chemoattractant Factor for 5T2 Multiple Myeloma Cells

The chemotactic and growth-stimulatory effect of insulin-like growth factor 1 (IGF-1) was investigated in the experimental mouse 5T2 multiple myeloma (MM) model. Chemotaxis was analyzed by classical checkerboard analysis. Bone marrow fibroblasts–conditioned medium exhibited a chemotactic effect on 5T2 MM cells that could be neutralized by adding a blocking antibody to IGF-1. On the other hand, exogenously added IGF-1 also had a chemotactic effect on the 5T2 MM cells. Moreover, in vitro analysis demonstrated that transmigrated 5T2 MM cells have a higher expression of IGF-1 receptor, both in bone marrow–conditioned medium and in IGF-1–induced chemotaxis, in comparison to cells before migration. When analyzed in vivo, 18 hours after injection of the heterogeneous 5T2 MM population, 5T2 MM cells present in the bone marrow show a higher expression of the IGF-1 receptor than their counterparts before injection. When the proliferative effect of IGF-1 was analyzed, no stimulation was observed, which is in contrast to the influence of bone marrow–conditioned medium and interleukin-6. Our results suggest a causal relationship between the presence of IGF-1 in the bone marrow and the chemotaxis of MM cells to and their subsequent presence in the bone marrow.

Homing behaviour of the malignant cell clone in multiple myeloma

Multiple myeloma (MM) represents a B cell malignancy characterised by the presence of a monoclonal population of end-stage B cells in the bone marrow. Although fully matured bone marrow plasma cells are the predominant cell type in MM, there is much evidence that also more immature B cells are included in the malignant cell clone which are considered to be the myeloma precursor cells. The fact that these cells are detectable in the blood circulation and that their number increases with disease progression, makes it very likely that they represent the component of the tumour clone that mediates disease dissemination. This implies that these cells must have the potential to extravasate and home to the bone marrow environment. Like the migration mechanisms used by normal leukocytes and/or metastatic tumour cells of non-haematopoietic origin, it can be assumed that this bone marrow homing process is mediated by adhesive interactions and chemotactic signals provided by the microenvironment of the tumour. Once in the bone marrow compartment, myeloma cells will receive the appropriate signals to grow and survive. This aspect of tumour-homing is found to be the result of a functional interplay between the myeloma cells and the surrounding microenvironment, involving the action of several cytokines and adhesion molecules. In the end phase of the disease, myeloma cells can lose their stroma-dependency resulting in extramedullary tumour growth. We review normal B cell homing and discuss molecular mechanisms that determine the homing behaviour of the malignant cell clone in MM.

Biology of the Transition of Monoclonal Gammopathy of Undetermined Significance (MGUS) to Multiple Myeloma

BACKGROUND: Approximately 25% of patients with monoclonal gammopathy of undetermined significance (MGUS) eventually develop multiple myeloma (MM) or a related plasma cell disorder that is universally fatal. In this report, we examine the changes that occur in the clonal plasma cell that are likely to be important in the progression of MGUS to active myeloma. METHODS: Studies that investigate the mechanisms involved in the multistep pathogenesis of monoclonal gammopathies are reviewed. Cytokines such as IL-6 and IL-1-beta, adhesion molecules, viruses, and oncogenes including ras, bcl-2, Rb, and p53 are discussed. RESULTS: IL-1-beta is produced by plasma cells from virtually all MM patients but is undetectable in most MGUS patients. IL-1-beta has potent osteoclast activating factor activity, can increase the expression of adhesion molecules, and can induce paracrine IL-6 production. The increased production of adhesion molecules could explain why myeloma cells are found predominantly in the bone marrow. Subsequently, these "fixed" monoclonal plasma cells could now stimulate osteoclasts through the production of IL-1-beta and paracrine generation of IL-6 resulting in osteolytic disease. With continued progression of the myeloma, the monoclonal plasma cells may later acquire the ability to produce IL-6 in an autocrine fashion that will be manifested clinically by an elevated labeling index. CONCLUSIONS: A better understanding of the progression of MGUS to myeloma may lead to novel therapeutic strategies to prevent the development of MM.

Growth control mechanisms in multiple myeloma

Interleukin-6 (IL-6) is the major growth factor for the malignant plasma cell clone in patients with multiple myeloma (MM). Although interferon-alpha (IFN-alpha) has been widely used as maintenance therapy in MM, controversy exists as to its clinical utility. This review summarizes data showing that cell growth arrest brought about by type I (IFNs-alpha/beta) and type II (IFN-gamma) IFNs occurs in part through utilization/modification of various components of the otherwise stimulatory Jak-STAT and Ras signaling pathways triggered by IL-6. Recent experimental results indicating that IFN-alpha acts as a survival factor for certain myeloma cell lines and frequently induces endogenous IL-6 expression may help to explain the conflicting clinical findings obtained in this heterogeneous disease with this usually potent growth inhibitor. By comparison, consistent antiproliferative activity exhibited by IFN-gamma on IL-6-dependent myeloma cell lines and primary myeloma cells from patients suggests that further investigation of the possible value of this cytokine in the treatment of MM may be warranted.

Expression of adhesion molecules in malignant plasma cells in multiple myeloma: comparison with normal plasma cells and functional significance

Malignant plasma cells in multiple myeloma are predominantly confined to the bone marrow, where they stimulate cytokine production by stromal cells and bone cells leading to osteoclast activation and formation of the characteristic lytic lesions in the skeleton. Adhesion molecules are critically involved in the cellular interactions between myeloma cells and stromal elements and may represent novel therapeutic targets to reduce osteolytic bone disease in multiple myeloma. Here, we review the literature on the adhesion molecule repertoire expressed by malignant plasma cells and discuss the evidence that adhesive interactions between myeloma cells and stromal cells stimulate production of bone-resorbing cytokines.

Organ involvement and phenotypic adhesion profile of 5T2 and 5T33 myeloma cells in the C57BL/KaLwRij mouse

The aim of this study was to evaluate the tissue infiltration and phenotypic adhesion profile of 5T2 multiple myeloma (MM) and 5T33 MM cells and to correlate it with that observed in human disease. For each line, 30 mice were intravenously inoculated with myeloma cells and at a clear-cut demonstrable serum paraprotein concentration; mice were sacrificed and a number of organs removed. The haematoxylin-eosin stainings on paraffin sections were complemented with immunohistochemistry using monoclonal antibodies developed against the specific MM idiotype. When analysed over time, 5T2 MM cells could be observed in bone marrow samples from week 9 after transfer of the cells. For the 5T33 MM, a simultaneous infiltration was observed in bone marrow, spleen and liver 2 weeks after inoculation. Osteolytic lesions consistently developed in the 5T2 MM, but this was not consistent for 5T33 MM. PCNA staining showed a higher proliferative index for the 5T33 MM cells. The expression of adhesion molecules was analysed by immunohistochemistry on cytosmears: both 5T2 MM and 5T33 MM cells were LFA-1, CD44, VLA-4 and VLA-5 positive. We conclude that both lines have a phenotypic adhesion profile analogous to that of human MM cells. As the 5T2 MM cells are less aggressive than the 5T33 MM cells, their organ distribution is more restricted to the bone marrow and osteolytic lesions are consistently present, the former cell line induces myeloma development similar to the human disease.

Adhesive interactions between tumour cells and bone marrow stromal elements in human multiple myeloma

Long-term bone marrow cultures (LTBMC) were established from marrow samples obtained from 6 myeloma patients and 5 healthy donors and were examined by in situ immunogold-silver staining. During the culture period, the established stroma in myeloma LTBMC revealed a lower level of confluency compared to the normal LTBMC. In addition, an increasing proportion of macrophages and osteoclasts was observed in the myeloma stroma throughout the culture period. Moreover, plasma cells were detectable by wk 8, mostly organized in small clusters. They strongly expressed VLA-4 (6/6), H-CAM (6/6), ICAM-1 (6/6) and N-CAM (3/6). In most cases, a weak expression of the other members of beta 1-integrins was observed. The expression of beta 2-integrins was always absent. Stromal fibroblasts were found to be weakly positive for VLA-2, VLA-3 and VLA-5 and showed strong expression of VCAM-1, H-CAM and ICAM-1. N-CAM expression could not be detected. By comparing the adhesion molecule profile of the stromal cells in myeloma cultures with normal bone marrow (BM) cultures, no particular defects could be observed. The stroma displayed most of the potential ligands which could interact with adhesion molecules detected on the myeloma cells. Among these ligands we could find fibronectin and VCAM-1 for VLA-4, collagen I for VLA-2 and VLA-3 and laminin for VLA-2, 3 and 6. Four myeloma cell lines, i.e. OPM-1, U266, RPMI 8226 and JJN3, with a representative phenotype, were used to study the adhesive interactions of myeloma cells with the BM microenvironment. All the myeloma cell lines bound strongly to the marrow cell layers and also showed a high binding to purified fibronectin (FN). However, the adhesion of the cell lines to intact stroma could not be significantly inhibited by anti-FN receptors antibodies. Nor could it be prevented when the latter were combined with anti-H-CAM, V-CAM and ICAM-1 antibodies, as tested in the JJN3 cell line. This implies that other unknown mechanisms contribute to the myeloma cell binding.

New insights into tumor-host interactions in lymphoma metastasis

The metastatic process is characterized by a complex series of sequential steps involving constant interactions (mutual "cross-talks") of metastasized tumor cells with their microenvironment (lymphocyte, macrophages, endothelial cells, etc.) in target organs. These interactions determine the outcome of metastasis (either the eradication of metastatic cells or their increased proliferation and invasion). Recently developed methods of tumor and host cell analysis at the molecular level allow better elucidation of molecular mechanisms of metastasis and of immune mechanisms involved in antitumor responses. Direct modulation of these processes will probably increase the success of clinical cancer treatment. Here we review data (a) on the expression of some costimulatory (MHC class II, CD80, sialoadhesin) and adhesion (LFA-1, ICAM-1, VLA-4) molecules on both metastasized tumor cells and host cells and (b) on the production of a cytotoxic molecule, nitric oxide, by in situ activated Kupffer and endothelial cells in the process of liver metastasis. This study was performed with well-characterized murine ESbL T lymphoma cells transduced with the bacterial lacZ gene, which allows detection and quantification of metastases at the single cell level throughout lymphoma growth and metastasis. Experimental results are discussed in the context of recent literature.

The neural cell adhesion molecule NCAM in multiple myeloma

The Neural Cell Adhesion Molecule NCAM is a membrane glycoprotein and belongs to the immunoglobulin superfamily. It is expressed on neural cells as well as on various neuroendocrine tumors and can be detected in sera of patients with small cell lung cancer. Its role is attributed to tumor invasion and formation of metastases. Malignant plasma cells and a subset of plasma cells from patients with monoclonal gammopathy exhibit surface expression of NCAM whereas normal plasma cells do not express NCAM. Expression as measured by flow cytometry using anti-CD56 antibodies does not seem to correlate with clinical course, however leukemic myelomas and myeloma cell lines tend to loose NCAM surface expression. An isoform of NCAM which is rich in polysialic acids and characteristic for embryonal NCAM (eNCAM) has been shown to be elevated in sera of patients with multiple myeloma using a chemiluminescence immunoassay. Patients with progressive myeloma tend to have high serum NCAM levels above the normal range of 20 U/ml. Analysis of 125 myeloma patients suggest that serum NCAM is a valuable parameter for tumor progression rather than tumor mass. Increase in serum NCAM may be associated with loss of adhesive function.

Intercellular adhesion molecule-1

The intercellular adhesion molecule (ICAM) 1 is an Ig-like cell adhesion molecule expressed by several cell types, including leukocytes and endothelial cells. It can be induced in a cell-specific manner by several cytokines, for example, tumor necrosis factor-alpha, interleukin-1, and interferon-gamma, and inhibited by glucocorticoids. Its ligands are the membrane-bound integrin receptors LFA-1 and Mac-1 on leukocytes, CD43, the soluble molecule fibrinogen, the matrix factor hyaluronan, rhinoviruses, and Plasmodium falciparum malaria-infected erythrocytes. ICAM-1 expression is predominantly transcriptionally regulated. The ICAM-1 promoter contains several enhancer elements, among them a novel kappa B element which mediates effects of 12-O-tetradecanoylphorbol-13-acetate, interleukin-1, lipopolysaccharide, tumor necrosis factor-alpha, and glucocorticoids. Expression regulation is cell specific and depends on the availability of cytokine/hormone receptors, signal transduction pathways, transcription factors, and posttranscriptional modification. ICAM-1 plays a role in inflammatory processes and in the T-cell mediated host defense system. It functions as a costimulatory molecule on antigen-presenting cells to activate MHC class II restricted T-cells, and on other cell types in association with MHC class I to activate cytotoxic T-cells. ICAM-1 on endothelium plays an important role in migration of (activated) leukocytes to sites of inflammation. ICAM-1 is shed by the cell and detected in plasma as sICAM-1. Regulation and significance of sICAM-1 are as yet unclear, but sICAM-1 is increased in many pathological conditions. ICAM-1 may play a pathogenetic role in rhinovirus infections. Derangement of ICAM-1 expression probably contributes to the clinical manifestations of a variety of diseases, predominantly by interfering with normal immune function. Among these are malignancies (e.g., melanoma and lymphomas), many inflammatory disorders (e.g., asthma and autoimmune disorders), atherosclerosis, ischemia, certain neurological disorders, and allogeneic organ transplantation. Interference with ICAM-1 leukocyte interaction using mAbs, soluble ICAM-1, antisense ICAM-1 RNA, and in the case of melanoma mAb-coupled immunotoxin, may offer therapeutic possibilities in the future. Integration of knowledge concerning membrane-bound and soluble ICAM-1 into a single functional system is likely to contribute to elucidating the immunoregulatory function of ICAM-1 and its pathophysiological significance in various disease entities.

Adhesion molecules involved in the binding of murine myeloma cells to bone marrow stromal elements

In previous work, we reported the development of the B9/BMI syngeneic murine bone marrow metastasis model. Interleukin (IL)-6-dependent, IL-I-producing B9/BMI cells, which preferentially home to and colonise the vertebral and femoral marrow after i.v. injection, exhibit striking similarity in cell surface phenotype to human myeloma cells, especially the expression of 3 adhesion molecules, CD44, VLA-4 and ICAM-I. Because the haematopoietic microenvironment consists of different cell types, such as endothelial cells, fibroblasts, adipocytes and macrophages, we investigated the functional significance of these adhesion molecules in heterotypic binding assays between B9/BMI cells and a newly established bone marrow-derived endothelial cell line (BMEC), a fibroblastoid pre-adipocyte cell line (BMS2.2) and primary bone marrow-derived macrophages. B9/BMI cells adhered well to all stromal elements: a combination of monoclonal antibodies (MAbs) against CD44 and VLA-4 significantly inhibited the adherence of B9/BMI cells to BMEC and BMS2.2 cells, whereas binding of B9/BMI cells to macrophages was partially blocked with an anti-ICAM-I MAb. Our results implicate multiple recognition mechanisms, including those involving CD44, VLA-4 and ICAM-I, in the retention of B9/BMI cells in the bone marrow.

Plasma cell dyscrasias: classification, clinical and laboratory characteristics, and differential diagnosis

Plasma cell dyscrasias form a heterogeneous group of diseases characterized by the expansion of the number of monoclonal bone marrow plasma cells that produce monoclonal immunoglobulins. Sensitive electrophoretic methods have shown that the incidence of these diseases is as high as 5% in adult individuals. Thus, the majority of cases should be considered to be a normal phenomenon. A few transform into neoplastic diseases, plasma cells becoming responsible for lytic bone lesions, the hallmark of MM. The distinction of benign and malignant forms is frequently difficult at presentation. We can easily recognize solitary myeloma, overt myeloma and plasma cell leukaemia, which require immediate chemotherapy. Therapy could be safely withheld in all the remaining forms, which require only follow-up. Thus, we suggest that plasma cell dyscrasias should be classified simply into two main groups according to the need of immediate chemotherapy. The appearance of new bone lesions and the increase of the M-component level remain the only two criteria that define malignant transformation. Several clinical and laboratory prognostic parameters indicate the risk of transformation, and hence how close the follow-up of the patient should be. Parameters related to the expansion of the plasma cell clone (percentage of bone marrow plasma cells, M-component level, lytic bone lesions and beta 2-microglobulin) are not always very low and very high in the benign and malignant forms, respectively, and frequently overlap in patients with intermediate plasma cell expansions. On the contrary, all parameters related to the intrinsic malignancy of the plasma cells (plasma cell LI, Karyotypic abnormalities and molecular alterations) have, by definition, to be normal in the benign forms. MRI is a new tool that may, early on, reveal lytic bone lesions undetectable by conventional radiography.

Mechanisms of the escape phase of myeloma

In multiple myeloma the duration of plateau is an important clinical and biological determinant of quality of life and survival. During plateau phase, the tumour is in an indolent state, as manifested by a low labelling index of plasma cells and other proliferative markers, e.g. the thymidine kinase level. The mechanism by which plasma cells escape from this indolent phase to a more aggressive phase of this disease is unknown, but a number of possible mechanisms have been postulated. These include loss of immunoregulation, clonal evolution, cytokine dysfunction and oncogene activation or tumour suppressor gene dysfunction. As current chemotherapy protocols do not appear to be able to eradicate the malignant clone, understanding the nature of the indolent phase of the malignant clone and the reasons for its escape from this phase are very important and may provide new options for disease control.