Suitable drug combination with bortezomib for multiple myeloma under stroma-free conditions and in contact with fibronectin or bone marrow stromal cells

Modelling the Tumour Microenvironment, but What Exactly Do We Mean by "Model"?

The Oxford English Dictionary includes 17 definitions for the word "model" as a noun and another 11 as a verb. Therefore, context is necessary to understand the meaning of the word model. For instance, "model railways" refer to replicas of railways and trains at a smaller scale and a "model student" refers to an exemplary individual. In some cases, a specific context, like cancer research, may not be sufficient to provide one specific meaning for model. Even if the context is narrowed, specifically, to research related to the tumour microenvironment, "model" can be understood in a wide variety of ways, from an animal model to a mathematical expression. This paper presents a review of different "models" of the tumour microenvironment, as grouped by different definitions of the word into four categories: model organisms, in vitro models, mathematical models and computational models. Then, the frequencies of different meanings of the word "model" related to the tumour microenvironment are measured from numbers of entries in the MEDLINE database of the United States National Library of Medicine at the National Institutes of Health. The frequencies of the main components of the microenvironment and the organ-related cancers modelled are also assessed quantitatively with specific keywords. Whilst animal models, particularly xenografts and mouse models, are the most commonly used "models", the number of these entries has been slowly decreasing. Mathematical models, as well as prognostic and risk models, follow in frequency, and these have been growing in use.

Bone Marrow Microenvironment Interplay and Current Clinical Practice in Multiple Myeloma: A Review of the Balkan Myeloma Study Group

The course of multiple myeloma (MM) is influenced by a variety of factors, including the specificity of the tumour microenvironment (TME). The aim of this review is to provide insight into the interplay of treatment modalities used in the current clinical practice and TME. Bortezomib-based triplets are the standard for MM first-line treatment. Bortezomib is a proteasome inhibitor (PI) which inhibits the nuclear factor kappa B (NF-κB) pathway. However, bortezomib is decreasing the expression of chemokine receptor CXCR4 as well, possibly leading to the escape of extramedullary disease. Immunomodulatory drugs (IMiDs), lenalidomide, and pomalidomide downregulate regulatory T cells (Tregs). Daratumumab, anti-cluster of differentiation 38 (anti-CD38) monoclonal antibody (MoAb), downregulates Tregs CD38+. Bisphosphonates inhibit osteoclasts and angiogenesis. Sustained suppression of bone resorption characterises the activity of MoAb denosumab. The plerixafor, used in the process of stem cell mobilisation and harvesting, block the interaction of chemokine receptors CXCR4-CXCL12, leading to disruption of MM cells’ interaction with the TME, and mobilisation into the circulation. The introduction of several T-cell-based immunotherapeutic modalities, such as chimeric-antigen-receptor-transduced T cells (CAR T cells) and bispecific antibodies, represents a new perspective in MM treatment affecting TME immune evasion. The optimal treatment approach to MM patients should be adjusted to all aspects of the individual profile including the TME niche.

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

Simple Summary

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

Abstract

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

NRF2 Is One of the Players Involved in Bone Marrow Mediated Drug Resistance in Multiple Myeloma

Multiple myeloma with clonal plasma expansion in bone marrow is the second most common hematologic malignancy in the world. Though the improvement of outcomes from the achievement of novel agents in recent decades, the disease progresses and leads to death eventually due to the elusive nature of myeloma cells and resistance mechanisms to therapeutic agents. In addition to the molecular and genetic basis of resistance pathomechanisms, the bone marrow microenvironment also contributes to disease progression and confers drug resistance in myeloma cells. In this review, we focus on the current state of the literature in terms of critical bone marrow microenvironment components, including soluble factors, cell adhesion mechanisms, and other cellular components. Transcriptional factor nuclear factor erythroid-derived-2-like 2 (NRF2), a central regulator for anti-oxidative stresses and detoxification, is implicated in chemoresistance in several cancers. The functional roles of NRF2 in myeloid-derived suppressor cells and multiple myeloma cells, and the potential of targeting NRF2 for overcoming microenvironment-mediated drug resistance in multiple myeloma are also discussed.

Myeloma Cells Are Activated in Bone Marrow Microenvironment by the CD180/MD-1 Complex, Which Senses Lipopolysaccharide

Multiple myeloma (MM) cells acquire dormancy and drug resistance via interaction with bone marrow stroma cells (BMSC) in a hypoxic microenvironment. Elucidating the mechanisms underlying the regrowth of dormant clones may contribute to further improvement of the prognosis of MM patients. In this study, we find that the CD180/MD-1 complex, a noncanonical lipopolysaccharide (LPS) receptor, is expressed on MM cells but not on normal counterparts, and its abundance is markedly upregulated under adherent and hypoxic conditions. Bacterial LPS and anti-CD180 antibody, but not other Toll-like receptor ligands, enhanced the growth of MM cells via activation of MAP kinases ERK and JNK in positive correlation with expression levels of CD180. Administration of LPS significantly increased the number of CD180/CD138 double-positive cells in a murine xenograft model when MM cells were inoculated with direct attachment to BMSC. Knockdown of CD180 canceled the LPS response in vitro and in vivo Promoter analyses identified IKZF1 (Ikaros) as a pivotal transcriptional activator of the CD180 gene. Both cell adhesion and hypoxia activated transcription of the CD180 gene by increasing Ikaros expression and its binding to the promoter region. Pharmacological targeting of Ikaros by the immunomodulatory drug lenalidomide ameliorated the response of MM cells to LPS in a CD180-dependent manner in vitro and in vivo Thus, the CD180/MD-1 pathway may represent a novel mechanism of growth regulation of MM cells in a BM milieu and may be a therapeutic target of preventing the regrowth of dormant MM cells.Significance: This study describes a novel mechanism by which myeloma cells are regulated in the bone marrow, where drug resistance and dormancy can evolve after treatment, with potential therapeutic implications for treating this often untreatable blood cancer. Cancer Res; 78(7); 1766-78. ©2018 AACR.

A phase II trial of small-dose bortezomib, lenalidomide and dexamethasone (sVRD) as consolidation/maintenance therapy in patients with multiple myeloma

PURPOSE

Consolidation/maintenance therapy induces deep remission in patients with multiple myeloma (MM); however, the most suitable regimen has been under investigation. The combination therapy with bortezomib, lenalidomide and dexamethasone (VRD) is a powerful regimen for relapsed/refractory as well as newly diagnosed MM as an induction therapy. However, severe adverse events (AEs) may become a problem when VRD is introduced without dose reduction as a consolidation/maintenance therapy.

METHODS

In this single-arm phase II study, we evaluated the efficacy of small-dose VRD regimen (sVRD) in the consolidation/maintenance setting. Sixteen patients who had partial response (PR) or better after any induction therapy were enrolled. Patients received at least six 28-day cycles of subcutaneous bortezomib (1.3 mg/m² on days 1 and 15), lenalidomide (10 mg on days 1-21) and dexamethasone (40 mg on days 1, 8, 15 and 22).

RESULTS

The overall response rate and the complete response (CR) rate were 100 and 43.8 %, respectively. In particular, one patient with CR and two patients with very good PR at enrollment achieved stringent CR during 6 courses of sVRD. With a median follow-up time of 29.4 months, the median progression-free survival (PFS) and overall survival (OS) were not reached, while the PFS and OS rates at 2.5 years were 66.6 and 77.3 %, respectively. Univariate analysis demonstrated that disease progression as a reason for discontinuation of sVRD had a negative impact on OS. There were no grade 3 or 4 hematologic or nonhematologic AEs.

CONCLUSION

Our sVRD regimen as a consolidation/maintenance therapy was highly effective and well tolerable.

Phosphorylation-mediated EZH2 inactivation promotes drug resistance in multiple myeloma

Alterations in chromatin modifications, such as histone methylation, have been suggested as mediating chemotherapy resistance in several cancer types; therefore, elucidation of the epigenetic mechanisms that underlie drug resistance may greatly contribute to the advancement of cancer therapies. In the present study, we identified histone H3-lysine 27 (H3K27) as a critical residue for epigenetic modification in multiple myeloma. We determined that abrogation of drug-induced H3K27 hypermethylation is associated with cell adhesion-mediated drug resistance (CAM-DR), which is the most important form of drug resistance, using a coculture system to evaluate stroma cell adhesion-dependent alterations in multiple myeloma cells. Cell adhesion counteracted anticancer drug-induced hypermethylation of H3K27 via inactivating phosphorylation of the transcription regulator EZH2 at serine 21, leading to the sustained expression of antiapoptotic genes, including IGF1, B cell CLL/lymphoma 2 (BCL2), and hypoxia inducible factor 1, α subunit (HIF1A). Pharmacological and genetic inhibition of the IGF-1R/PI3K/AKT pathway reversed CAM-DR by promoting EZH2 dephosphorylation and H3K27 hypermethylation both in vitro and in refractory murine myeloma models. Together, our findings identify and characterize an epigenetic mechanism that underlies CAM-DR and suggest that kinase inhibitors to counteract EZH2 phosphorylation should be included in combination chemotherapy to increase therapeutic index.

The formation of electronically excited species in the human multiple myeloma cell suspension

In this study, evidence is provided on the formation of electronically excited species in human multiple myeloma cells U266 in the growth medium exposed to hydrogen peroxide (H2O2). Two-dimensional imaging of ultra-weak photon emission using highly sensitive charge coupled device camera revealed that the addition of H2O2 to cell suspension caused the formation of triplet excited carbonyls (3)(R = O)*. The kinetics of (3)(R = O)* formation in the real time, as measured by one-dimensional ultra-weak photon emission using low-noise photomultiplier, showed immediate enhancement followed by a slow decay. In parallel to the formation of (3)(R = O)*, the formation of singlet oxygen ((1)O2) in U266 cells caused by the addition of H2O2 was visualized by the imaging of (1)O2 using the green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. Additionally, the formation of (1)O2 after the addition of H2O2 to cell suspension was detected by electron paramagnetic resonance spin-trapping spectroscopy using 2,2,6,6-tetramethyl-4-piperidone. Presented results indicate that the addition of H2O2 to cell suspension results in the formation of (3)(R = O)* and (1)O2 in U266 cell suspension. The contribution of the cell-free medium to the formation of electronically excited species was discussed.