High-risk multiple myeloma: a multifaceted entity, multiple therapeutic challenges

The Peptide-Drug Conjugate Melflufen Modulates the Unfolded Protein Response of Multiple Myeloma and Amyloidogenic Plasma Cells and Induces Cell Death

Immunoglobulin light-chain (AL) amyloidosis is a rare disease caused by clonal plasma cell secretion of misfolded light chains that assemble as toxic amyloid fibrils, depositing in vital organs including the heart and kidneys, causing organ dysfunction. Plasma cell-directed therapeutics are expected to reduce production of toxic light chain by eliminating amyloidogenic cells in bone marrow, thereby diminishing amyloid fibril deposition and providing the potential for organ recovery. Melphalan flufenamide (melflufen) is a first-in-class peptide-drug conjugate that targets aminopeptidases and rapidly releases alkylating agents inside tumor cells. Melflufen is highly lipophilic, permitting rapid uptake by cells, where it is enzymatically hydrolyzed by aminopeptidases, resulting in intracellular accumulation of the alkylating agents, including melphalan. Previous data demonstrating sensitivity of myeloma cells to melflufen suggest that the drug might be useful in AL amyloidosis. We describe the effects of melflufen on amyloidogenic plasma cells in vitro and ex vivo, demonstrating enhanced cytotoxic effects in comparison to melphalan, as well as novel mechanisms of action through the unfolded protein response (UPR) pathway. These findings provide evidence that melflufen-mediated cytotoxicity extends to amyloidogenic plasma cells, and support the rationale for the evaluation of melflufen in patients with AL amyloidosis.

Blockade of PLD1 potentiates the antitumor effects of bortezomib in multiple myeloma cells by inhibiting the mTOR/NF-κB signal pathway

OBJECTIVE

Phospholipase D1 (PLD1) is an enzyme of the phospholipase D (PLD) superfamily. It is involved in the occurrence of various tumors. However, its role in multiple myeloma (MM) remained undefined. This study aimed to investigate the mechanism of PLD1 in the therapy of myeloma disease.

MATERIAL AND METHODS

Cell lines U266 and H929 were treated with PLD1 specific inhibitor VU0359595 combined bortezomib, a proteasome inhibitor. Their effects on MM cell proliferation, apoptosis, and relevant signal pathways of apoptosis were determined by cell counting kit-8 (CCK-8), real-time polymerase reaction chain (RT-PCR), ATP assay, and western blot.

RESULTS

PLD1 was highly expressed in U266 and H929 cells. VU0359595 didn't affect the proliferation and apoptosis of MM cells. However, VU0359595 could enhance growth inhibition, decreasing mitochondrial membrane potentials (MMPs) and ATP levels of bortezomib treated MM cells. VU0359595 also strengthened bortezomib-induced apoptosis via activating caspase-8, caspase-9, caspase-3; and down-regulating the expressions of anti-apoptosis proteins BCL-2. In addition, the bortezomib-induced cytotoxicity on MM cells was significantly augmented by VU0359595 through efficient suppression of the mTOR/NF-κB signal pathway.

CONCLUSION

PLD1 inhibition can remarkably exert antitumor effects with bortezomib on MM, which is a novel potentially targeting therapeutic agent, especially for drug-resistant MM patients.

Evodiamine Selectively Inhibits Multiple Myeloma Cell Growth by Triggering Activation of Intrinsic Apoptosis Pathway

Introduction

Evodiamine (Evo) is one of the main bioactive components derived from the drying mature fruit of the genus Evodia rutaecarpa (Juss.) Benth. Although Evo has shown its anti-cancer activity in several cancers, the effects on multiple myeloma (MM) remain unknown. In this study, we aim to investigate the cytotoxic role of Evo on MM cells.

Methods

CCK-8 assay, apoptotic cell analysis, xenografted mice model, caspase activity assay and mitochondrial membrane potential assay were performed.

Results

We found that Evo selectively inhibits cell proliferation and increases apoptosis rate in MM cells, but not in healthy B lymphocytes, in a time and dose-dependent manner. Evo treatment significantly activated caspase-3 and −9 in MM cells. Evo also increased cytochrome C expression and ROS production in cytosol in a dose-dependent manner, which was abolished by MitoTEMPO cotreatment. In addition, co-treatment with bortezomib and Evo showed a more potent reduction of cell viability and a higher apoptosis than that of bortezomib single treatment in U266 and RPMI8226 cells.

Conclusion

We provided evidence to demonstrate that Evo selectively suppresses cell growth and increases apoptosis rate in MM cells through the intrinsic apoptosis pathway. Application of Evo and bortezomib might enhance the anti-cancer effect on MM cells.

Maintaining therapeutic progress in multiple myeloma by integrating genetic and biological advances into the clinic

INTRODUCTION

Utilizing advances in genetic and immunologic analysis to segment and direct treatment is potentially a way of maintaining therapeutic progress toward cure in multiple myeloma (MM). This approach works well using clinical segments but can be optimized using recent genetic and immunologic technologies, which have opened the possibility of enhancing risk stratification and disease subclassification. Areas covered: This position paper discusses strategies to segment myeloma into subgroups with distinct risk profiles and distinct targetable lesions are presented. Expert commentary: Risk stratified treatment of MM is already a clinical reality that can be enhanced by the developmental of unified segmentation and testing approaches. Mutation-targeted treatment has proven to be effective against the RAS pathway, but is compromised by intra-clonal and spatiotemporal heterogeneity. Identifying new disease segments based on tumor biology or immunological content of the microenvironment offers an exciting new way to control and even eradicate myeloma clones. Going forward, risk and biologically stratified therapy for myeloma is a promising way of maintaining therapeutic progress, as is precision immunotherapy directed by the cellular context of the bone marrow.

Diagnosis and management of smoldering multiple myeloma: the razor's edge between clonality and cancer

Smoldering multiple myeloma (SMM) is a rare plasma cell disorder, and as the disease is asymptomatic, diagnosis is often incidental. SMM is characterized by increased marrow infiltration by clonal plasma cells and/or elevated serum M-protein in the absence of a myeloma-defining event (MDE). In recent years, SMM has gained increased attention owing to a broadening of the criteria for MDE, which include apart from the CRAB criteria, three additional parameters. Survival advantage may be offered by early treatment in the high-risk subset, based on a single trial. In this review, we assess the risk factors and models for progression to multiple myeloma. A review of our diagnostic and management approaches to SMM is presented.