Molecular pathogenesis of multiple myeloma and its premalignant precursor

Does immunohistochemical staining predict mobilization success in multiple myeloma patients?

BACKGROUND

So many risk factors for mobilization failure have been described so far. We aimed to identify the risk factors and search the possible effects of bone marrow fibrosis (BMF), CD56, c-myc, and cyclinD1 expression on mobilization.

METHODS

We evaluated 189 patients with MM who were admitted for stem cell mobilization before autologous stem cell transplantation (ASCT) between 2015 and June 2021. Clinical, laboratory, treatment features, and survival outcomes were compared in patients who were successfully mobilized and who were not.

RESULTS

Mobilization failure rate was 11.1 % (21) in our study group. Male gender, mobilization with only G-CSF, history of previous ASCT, lenalidomide exposure, and 2 lines of chemotherapy before stem cell mobilization were observed more commonly in mobilization failure group. There is no relationship between mobilization failure and BMF, CD56, c-myc, and cyclin D1 expression status in patients who received either only G-CSF or G-CSF+ chemotherapy for mobilization. Overall survival (OS) was not different in groups of patients who were successfully mobilized and who were not. Neutrophil engraftment was faster in patients who were transfused > 5 × 106/kg stem cells (p = 0.015). ECOG performance status (p = 0.004), c-myc expression (p = 0.005), lenalidomide therapy before mobilization (p = 0.032), and mobilization with G-CSF+chemotherapy was found to be predictive factors for OS.

CONCLUSION

Even though we could not find any predictive value of CD56, c-myc, and cyclin D1 expression on mobilization, c-myc was found to be associated with low OS. Further studies with large and homogenous study population would be more informative.

Exploring the anti-myeloma potential of composite nanoparticles As4S4/Fe3O4: Insights from in vitro, ex vivo and in vivo studies

Given the profound multiple myeloma (MM) heterogeneity in clonal proliferation of malignant plasma cells (PCs) and anti-MM therapeutic potential of nanotherapies, it is inevitable to develop treatment plan for patients with MM. Two composite nanoparticles (NPs), As4S4/Fe3O4 (4:1) and As4S4/Fe3O4 (1:1) demonstrated effective anti-MM activity in in vitro, ex vivo, and in vivo in xenograft mouse model. Composite NPs triggered activation of p-ERK1/2/p-JNK, and downregulation of c-Myc, p-PI3K, p-4E-BP1; G2/M cell cycle arrest with increase in cyclin B1, histones H2AX/H3, activation of p-ATR, p-Chk1/p-Chk2, p-H2AX/p-H3; and caspase- and mitochondria-dependent apoptosis induction. NPs attenuated the stem cell-like side population in MM cells, both alone and in the presence of stroma. For a higher clinical response rate, As4S4/Fe3O4 (4:1) observed synergism with dexamethasone and melphalan, while As4S4/Fe3O4 (1:1) showed synergistic effects in combination with bortezomib, lenalidomide and pomalidomide anti-MM agents, providing the framework for further clinical evaluation of composite NPs in MM.

Efficacy and survival outcome of allogeneic stem-cell transplantation in multiple myeloma: meta-analysis in the recent 10 years

Introduction

Allogeneic hematopoietic cell transplantation (alloHCT) possessed direct cytotoxicity and graft-versus-multiple myeloma effect (GvMM). Growing trials have shown survival benefits of performing alloHCT in both newly diagnosed and relapsed MM.

Methods

We aimed to provide a comprehensive analysis in the recent 10 years to verify the efficacy and survival outcome of alloHCT in MM patients. A total of 61 studies which provide data between 14/04/2013 and 14/04/2023 and a total of 15,294 data from MM patients who had undergone alloSCT were included in our study. The best response rates (CR, VGPR, PR) and survival outcomes (1-, 2-, 3-,5-, and 10-year OS, PFS, NRM) were assessed. We further conducted meta-analysis in the NDMM/frontline setting and RRMM/salvage setting independently.

Results

The pooled estimate CR, VGPR, and PR rates were 0.45, 0.21, and 0.24, respectively. The pooled estimates of 1-, 2-, 3-, 5-, and 10-year OS were 0.69, 0.57, 0.45, 0.45, and 0.36, respectively; the pooled estimates of 1-, 2-, 3-, 5-, and 10-year PFS were 0.47, 0.35, 0.24, 0.25, and 0.28, respectively; and the pooled estimates of 1-, 2-, 3-, 5-, and 10-year NRM were 0.16, 0.21, 0.16, 0.20, and 0.15, respectively. In the NDMM/upfront setting, the pooled estimate CR rate was 0.54, and those for 5-year OS, PFS, and NRM were 0.69, 0.40, and 0.11, respectively. In a relapsed setting, the pooled estimate CR rate was 0.31, and those for 5-year OS, PFS, and NRM were 0.24, 0.10, and 0.15, respectively.

Discussion

Our results showed constant OS, PFS, and NRM from the third year onwards till the 10th year, suggesting that alloSCT has sustained survival benefits. Good response rate and promising survival outcome were observed in the NDMM/ frontline setting.

Conclusion

Although comparing with other treatments, alloSCT had a lower response rate and poorer short-term survival outcome, long-term follow-up could reveal survival benefits of alloSCT in MM patients.

TGF-β: an active participant in the immune and metabolic microenvironment of multiple myeloma : TGF-β in the microenvironment of multiple myeloma

Although substantial quantities of potent therapies for multiple myeloma (MM) have been established, MM remains an incurable disease. In recent years, our understanding of the initiation, development, and metastasis of cancers has made a qualitative leap. Cancers attain the abilities to maintain proliferation signals, escape growth inhibitors, resist cell death, induce angiogenesis, and more importantly, escape anti-tumor immunity and reprogram metabolism, which are the hallmarks of cancers. Besides, different cancers have different tumor microenvironments (TME), thus, we pay more attention to the TME in the pathogenesis of MM. Many researchers have identified that myeloma cells interact with the components of TME, which is beneficial for their survival, ultimately causing the formation of immunosuppressive and high-metabolism TME. In the process, transforming growth factor-β (TGF-β), as a pivotal cytokine in the TME, controls various cells' fates and influences numerous metabolic pathways, including inhibiting immune cells to infiltrate the tumors, suppressing the activation of anti-tumor immune cells, facilitating more immunosuppressive cells, enhancing glucose and glutamine metabolism, dysregulating bone metabolism and so on. Thus, we consider TGF-β as the tumor promoter. However, in healthy cells and the early stage of tumors, it functions as a tumor suppressor. Due to the effect of context dependence, TGF-β has dual roles in TME, which attracts us to further explore whether targeting it can overcome obstacles in the treatment of MM by regulating the progression of myeloma, molecular mechanisms of drug resistance, and various signaling pathways in the immune and metabolic microenvironment. In this review, we predominantly discuss that TGF-β promotes the development of MM by influencing immunity and metabolism.

Functional Investigation of IGF1R Mutations in Multiple Myeloma

High expression of the receptor tyrosine kinase (RTK) insulin-like growth factor-1 receptor (IGF1R) and RTK mutations are associated with high-risk/worse prognosis in multiple myeloma (MM). Combining the pIGF1R/pINSR inhibitor linsitinib with the proteasome inhibitor (PI) bortezomib seemed promising in a clinical trial, but IGF1R expression was not associated with therapy response. Because the oncogenic impact of IGF1R mutations is so far unknown, we investigated the functional impact of IGF1R mutations on survival signaling, viability/proliferation and survival response to therapy. We transfected four human myeloma cell lines (HMCLs) with IGF1RWT, IGF1RD1146N and IGF1RN1129S (Sleeping Beauty), generated CRISPR-Cas9 IGF1R knockouts in the HMCLs U-266 (IGF1RWT) and L-363 (IGF1RD1146N) and tested the anti-MM activity of linsitinib alone and in combination with the second-generation PI carfilzomib in seven HMCLs. IGF1R knockout entailed reduced proliferation. Upon IGF1R overexpression, survival signaling was moderately increased in all HCMLs and slightly affected by IGF1RN1129S in one HMCL, whereby the viability remained unaffected. Expression of IGF1RD1146N reduced pIGF1R-Y1135, especially under serum reduction, but did not impact downstream signaling. Linsitinib and carfilzomib showed enhanced anti-myeloma activity in six out of seven HMCL irrespective of the IGF1R mutation status. In conclusion, IGF1R mutations can impact IGF1R activation and/or downstream signaling, and a combination of linsitinib with carfilzomib might be a suitable therapeutic approach for MM patients potentially responsive to IGF1R blockade.

Is It Possible to Predict Tumor Progression Through Genomic Characterization of Monoclonal Gammopathy and Smoldering Multiple Myeloma?

The study of monoclonal serum proteins has led to the generation of two major theories: one proposing that individuals who had monoclonal proteins without any symptoms or evidence of end-organ damage have a benign condition, the other one suggesting that some individuals with asymptomatic monoclonal proteins may progress to multiple myeloma and thus are affected by a monoclonal gammopathy of undetermined significance (MGUS). Longitudinal studies of subjects with MGUS have supported the second theory. Subsequent studies have characterized and defined the existence of another precursor of multiple myeloma, smoldering multiple myeloma (SMM), intermediate between MGUS and multiple myeloma. Primary molecular events, chromosome translocations, and chromosome number alterations resulting in hyperploidy, required for multiple myeloma development, are already observed in myeloma precursors. MGUS and SMM are heterogeneous conditions with the presence of tumors with distinct pathogenic phenotypes and clinical outcomes. The identification of MGUS and SMM patients with a molecularly defined high risk of progression to MM offers the unique opportunity of early intervention with a therapeutic approach on a low tumor burden.

Molecular Pathogenesis of Multiple Myeloma: Clinical Implications

Multiple myeloma is a malignancy of bone-marrow-localized, isotype-switched plasma cells that secrete a monoclonal immunoglobulin and cause hyperCalcemia, Anemia, Renal failure, and lytic Bone disease. It is preceded, often for decades, by a relatively stable monoclonal gammopathy lacking these clinical and malignant features. Both conditions are characterized by the presence of types of immunoglobulin heavy gene translocations that dysregulate a cyclin D family gene on 11q13 (CCND1), 6p21 (CCND3), or 12q11 (CCND2), a maf family gene on 16q23 (MAF), 20q11 (MAFB), or 8q24 (MAFA), or NSD2/FGFR3 on 4p16, or the presence of hyperdiploidy. Subsequent loss of function of tumor suppressor genes and mutations activating MYC, RAS, NFkB, and cell cycle pathways are associated with the progression to malignant disease.

Lifestyle Factors and Cancer: A Narrative Review

Lifestyle factors and their impact on cancer prevention, prognosis, and survivorship are increasingly recognized in the medical literature. Lifestyle factors are primarily defined here as diet and physical activity. We conducted a narrative review of the primary published data, including randomized controlled trials and prospective studies, on the impact of primary lifestyle factors on oncogenesis and clinical outcomes in the preventative and survivorship setting. First, we discuss the oncogenic mechanisms behind primary lifestyle factors (diet, physical activity and, within these 2, obesity). Then, we discuss the impact of adherence to lifestyle guidelines and dietary patterns on cancer incidence based on primary data. Owing to the plethora of published literature, to summarize the data in a more efficient manner, we describe the role of physical activity on cancer incidence using summative systematic reviews. We end by synthesizing the primary data on lifestyle factors in the survivorship setting and conclude with potential future directions. In brief, the various large-scale studies investigating the role diet and physical activity have reported a beneficial effect on cancer prevention and survivorship. Although the impact of single lifestyle factors on cancer incidence risk reduction is generally supported, holistic approaches to address the potential synergistic impact of multiple lifestyle factors together in concert is limited. Future research to identify the potentially synergistic effects of lifestyle modifications on oncogenesis and clinical outcomes is needed, particularly in cancer subtypes beyond colorectal and breast cancers.

Immunocompetent Mouse Models of Multiple Myeloma: Therapeutic Implications

Immunocompetent mouse models of multiple myeloma (MM) are particularly needed in the era of T cell redirected therapy to understand drivers of sensitivity and resistance, optimize responses, and prevent toxicities. Three mouse models have been extensively characterized: the Balb/c plasmacytomas, the 5TMM, and the Vk*MYC. In the last year, additional models have been generated, which, for the first time, capture primary MM initiating events, like MMSET/NSD2 or cyclin D1 dysregulation. However, the long latency needed for tumor development and the lack of transplantable lines limit their utilization. Future studies should focus on modeling hyperdiploid MM.

Immune profiles to predict bortezomib-based treatment response for multiple myeloma patients

BACKGROUND

To evaluate the distribution of bone marrow immune cell subsets and their correlation with treatment efficacy in patients with multiple myeloma (MM).

METHODS

We analyzed the bone marrow lymphocyte subsets of 186 newly diagnosed MM patients at diagnosis and their correlation with clinical characteristics. In our study, eight-color flow cytometry, a method commonly used to detect plasma cell phenotypes, was used to analyze seven bone marrow immune cell groups by change gate-strategy.

RESULTS

First, for all the 7 immune cell groups, the percentage of immature B cells was significantly lower in stage III patients than in stage I patients, while the trend was reversed in memory B cells in both the International Staging System(p = 0.004) and Revised International Staging System(p = 0.018). Second, the percentage of naïve B cells were significantly lower in patients with severe anemia, while the percentage of memory B cells had reversed trend. The percentage of immature B cells were lower in patients with Cr ≥ 2 mg/dL than in patients with Cr < 2 mg/dL. Then we followed the treatment efficacy of 152 patients who received four cycles of induction therapy (bortezomib + dexamethasone or bortezomib + lenalidomide + dexamethasone) and analyzed the relationship between bone marrow lymphocyte subsets at the initial stage and treatment response datasets. We found that both the percentage of B cells(p＜0.001) and immature B(p = 0.002) were increased in patients who achieved very good partial remission(VGPR) after four cycles of induction therapy. The ROC results indicated the combination of the multiple immune subgroups had predictive values (AUC = 0.802, p<0.001) in the treatment effect after four cycles of induction therapy.

CONCLUSIONS

Overall, these results suggest that the analysis of lymphocyte subsets along with plasma cell immunophenotyping could be a potential index for determining the prognosis of MM patients.

Transcriptional Heterogeneity Overcomes Super-Enhancer Disrupting Drug Combinations in Multiple Myeloma

Multiple myeloma (MM) is a malignancy that is often driven by MYC and that is sustained by IRF4, which are upregulated by super-enhancers. IKZF1 and IKZF3 bind to super-enhancers and can be degraded using immunomodulatory imide drugs (IMiD). Successful IMiD responses downregulate MYC and IRF4; however, this fails in IMiD-resistant cells. MYC and IRF4 downregulation can also be achieved in IMiD-resistant tumors using inhibitors of BET and EP300 transcriptional coactivator proteins; however, in vivo these drugs have a narrow therapeutic window. By combining IMiDs with EP300 inhibition, we demonstrate greater downregulation of MYC and IRF4, synergistic killing of myeloma in vitro and in vivo, and an increased therapeutic window. Interestingly, this potent combination failed where MYC and IRF4 expression was maintained by high levels of the AP-1 factor BATF. Our results identify an effective drug combination and a previously unrecognized mechanism of IMiD resistance.

SIGNIFICANCE

These results highlight the dependence of MM on IKZF1-bound super-enhancers, which can be effectively targeted by a potent therapeutic combination pairing IMiD-mediated degradation of IKZF1 and IKZF3 with EP300 inhibition. They also identify AP-1 factors as an unrecognized mechanism of IMiD resistance in MM. See related article by Neri, Barwick, et al., p. 56. See related commentary by Yun and Cleveland, p. 5. This article is featured in Selected Articles from This Issue, p. 4.

BCMA- and CST6-specific CAR T cells lyse multiple myeloma cells and suppress murine osteolytic lesions

We have previously demonstrated that cystatin E/M (CST6), which is elevated in a subset of patients with multiple myeloma (MM) lacking osteolytic lesions (OLs), suppresses MM bone disease by blocking osteoclast differentiation and function. CST6 is a secreted type 2 cystatin, a cysteine protease inhibitor that regulates lysosomal cysteine proteases and the asparaginyl endopeptidase legumain. Here, we developed B cell maturation antigen (BCMA) CST6 chimeric antigen receptor T cells (CAR-T cells), which lysed MM cells and released CST6 proteins. Our in vitro studies show that these CAR-T cells suppressed the differentiation and formation of tartrate-resistant acid phosphatase-positive (TRAP+) osteoclasts. Using xenografted MM mice, bioluminescence images showed that both BCMA-CAR-T and BCMA-CST6-CAR-T cells inhibited MM growth to a similar extent. Reconstructed micro-computed tomography images revealed that BCMA-CST6-CAR-T cells, but not BCMA-CAR-T cells, prevented MM-induced bone damage and decreased osteoclast numbers. Our results provide a CAR-T strategy that targets tumor cells directly and delivers an inhibitor of bone resorption.

RING box protein-1(RBX1), a key component of SCF E3 ligase, induced multiple myeloma cell drug-resistance though suppressing p27

Multiple myeloma (MM) is a clonal disease of plasma cells that remains, for the most part, incurable despite the advent of several novel therapeutics. The elevated expression of p27 and its association with cell-cycle arrest is speculated to be one of the major mechanisms by which MM cells escape the cytotoxic effects of therapeutic agents. In this study, we demonstrated that RBX1 silencing could inhibit MM cell growth and promote cell drug resistance. RBX1 directly interacted with and triggered the ubiquitination and degradation of p27, ultimately causing p27 reduction. Additionally, cell growth and apoptosis analysis indicated that the role of RBX1 in regulating myeloma cell proliferation and drug resistance resulted from p27 accumulation, which occurred in a Thr187 phosphorylation-dependent manner. Furthermore, the cell-cycle analysis demonstrated that RBX1 overexpression induced cells to enter the cell cycle (S-phase) and partially inhibited chemotherapeutic drugs-mediated cell cycle arrest. Notably, the forced expression of RBX1 also inhibited the cell adhesion-mediated elevation of p27 and induced the accumulation of adherent cells in apoptosis, especially the proteolytic cleavage of caspase-3. Additionally, RBX1 knockdown significantly inhibited myeloma development in SCID-Hu mice and in a human MM xenotransplant model. Overall, these in vitro and in vivo experiments indicated that the RBX1-p27 axis could be a central molecular mechanism by which RBX1 functions as a tumor promoter and stimulates cell growth in chemotherapeutic drugs treated MM cells.

Cytokine receptor IL27RA is an NF-κB-responsive gene involved in CD38 upregulation in multiple myeloma

Multiple myeloma (MM) shows constitutive activation of canonical and noncanonical nuclear factor κB (NF-κB) signaling via genetic mutations or tumor microenvironment (TME) stimulations. A subset of MM cell lines showed dependency for cell growth and survival on the canonical NF-κB transcription factor RELA alone, suggesting a critical role for a RELA-mediated biological program in MM pathogenesis. Here, we determined the RELA-dependent transcriptional program in MM cell lines and found the expression of the cell surface molecules interleukin-27 receptor-α (IL-27Rα) and the adhesion molecule JAM2 to be responsive to RELA at the messenger RNA and protein levels. IL-27Rα and JAM2 were expressed on primary MM cells at higher levels than on healthy long-lived plasma cells (PCs) in the bone marrow. IL-27 activated STAT1, and to a lesser extent STAT3, in MM cell lines and in PCs generated from memory B cells in an IL-21-dependent in vitro PC differentiation assay. Concomitant activity of IL-21 and IL-27 enhanced differentiation into PCs and increased the cell-surface expression of the known STAT target gene CD38. In accordance, a subset of MM cell lines and primary MM cells cultured with IL-27 upregulated CD38 cell-surface expression, a finding with potential implications for enhancing the efficacy of CD38-directed monoclonal antibody therapies by increasing CD38 expression on tumor cells. The elevated expression of IL-27Rα and JAM2 on MM cells compared with that on healthy PCs may be exploited for the development of targeted therapeutic strategies that modulate the interaction of MM cells with the TME.

Regulation of miRNA expression by α4β1 integrin-dependent multiple myeloma cell adhesion

The α4β1 integrin regulates the trafficking of multiple myeloma (MM) cells and contributes to MM disease progression. MicroRNAs (miRNAs) can have both tumor suppressor and oncogenic roles and thus are key controllers of tumor evolution, and have been associated with different phases of MM pathogenesis. Using small RNAseq analysis, we show here that α4β1-dependent MM cell adhesion regulates the expression of forty different miRNAs, therefore expanding our current view of the α4β1 involvement in MM cell biology. Specific upregulation of miR-324-5p and miR-331-3p in cells attached to α4β1 ligands was confirmed upon silencing the α4 integrin subunit, and their increased levels found to be dependent on Erk1/2- and PI3K-Akt-, but not Src-dependent signaling. Enhanced miR-324-5p expression upon α4β1-mediated MM cell adhesion aimed the hedgehog (Hh) component SMO, revealing that the miR-324-5p-SMO module represents a α4β1-regulated pathway that could control Hh-dependent cellular responses in myeloma. Our results open new therapy research avenues around the α4β1 contribution to MM progression that deserve to be investigated.

Laboratory and Clinical Settings of Heavy/Light Chain (HLC) Assays in the Management of Monoclonal Gammopathies and Multiple Myeloma

The antibody-related immune response is mediated by immunoglobulins (Igs), soluble circulating glycoproteins produced by activated B cells that, upon the recognition of specific epitopes on pathogen surfaces, activate, proliferate, and differentiate into antibody-secreting plasma cells. Although the antibodies are effectors of the humoral immune adaptive response, their overproduction in response to a dysregulated proliferation of clonal plasma cell production in tumoral conditions (i.e., multiple myeloma), enriches the serum and urinary matrices, assuming the crucial role of biomarkers. Multiple myeloma (MM) is a plasma cell dyscrasia characterized by the expansion and accumulation of clonally activated plasma cells in bone marrow, determining the release of high amounts of monoclonal component (MC) that can be detected as intact immunoglobulin (Ig), immunoglobulin fragments, or free light chains (FLCs). The importance of detecting biomarkers for the diagnosis, monitoring, and prognosis of diseases is highlighted by the international guidelines that recommend specific assays for the analysis of intact Igs and FLC. Moreover, a developed assay called Hevylite^® allows for the quantification of immunoglobulins that are both involved (iHLC) and not involved (uHLC) in the tumor process; this is a fundamental aspect of following up the patient's workup and evaluating the progression of disease, together with the treatments response. We here summarize the major points of the complex scenario involving monoclonal gammopathies and MM clinical management in view of advantages derived for the use of Hevylite^®.

HDAC4 in cancer: A multitasking platform to drive not only epigenetic modifications

Controlling access to genomic information and maintaining its stability are key aspects of cell life. Histone acetylation is a reversible epigenetic modification that allows access to DNA and the assembly of protein complexes that regulate mainly transcription but also other activities. Enzymes known as histone deacetylases (HDACs) are involved in the removal of the acetyl-group or in some cases of small hydrophobic moieties from histones but also from the non-histone substrate. The main achievement of HDACs on histones is to repress transcription and promote the formation of more compact chromatin. There are 18 different HDACs encoded in the human genome. Here we will discuss HDAC4, a member of the class IIa family, and its possible contribution to cancer development.

Analysis of signaling cascades from myeloma cells treated with pristimerin

Multiple myeloma (MM) is the 2nd most frequently diagnosed blood cancer after non-Hodgkin's lymphoma. The present study aimed to identify the differentially expressed genes (DEGs) between the control and pristimerin-treated MM cell lines. We examined the GSE14011 microarray dataset and screened DEGs with GEO2R statistical tool using the inbuilt limma package. We used a bioinformatics pipeline to identify the differential networks, signaling cascades, and the survival of the hub genes. We implemented two different enrichment analysis including ClueGO and Metacore™, to get accurate annotation for most significant DEGs. We screened the most significant 408 DEGs from the dataset based on p-values and logFC values. Using protein network analysis, we found the genes UBC, HSP90AB1, HSPH1, HSPA1B, HSPA1L, HSPA6, HSPD1, DNAJB1, HSPE1, DNAJC10, BAG3, and DNAJC7 had higher node degree distribution. In contrast, the functional annotation provided that the DEGs were predominantly enriched in B-cell receptor signaling, unfolded protein response, positive regulation of phagocytosis, HSP70, and HSP40-dependent folding, and ubiquitin-proteasomal proteolysis. Using network algorithms, and comparing enrichment analysis, we found the hub genes enriched were INHBE, UBC, HSPA1A, HSP90AB1, IKBKB, and BAG3. These DEGs were further validated with overall survival and gene expression analysis between the tumor and control groups. Finally, pristimerin effects were validated independently in a cell line model consisting of IM9 and U266 MM cells. Pristimerin induced in vitro cytotoxicity in MM cells in a dose-dependent manner. Pristimerin inhibited NF-κB, induced accumulation of ubiquitinated proteins and inhibited HSP60 in the validation of bioinformatics findings, while pristimerin-induced caspase-3 and PARP cleavage confirmed cell death. Taken together, we found that the identified DEGs were strongly associated with the apoptosis induced in MM cell lines due to pristimerin treatment, and combinatorial therapy derived from pristimerin could act as novel anti-myeloma multifunctional agents.

The BLM helicase is a new therapeutic target in multiple myeloma involved in replication stress survival and drug resistance

Multiple myeloma (MM) is a hematologic cancer characterized by accumulation of malignant plasma cells in the bone marrow. To date, no definitive cure exists for MM and resistance to current treatments is one of the major challenges of this disease. The DNA helicase BLM, whose depletion or mutation causes the cancer-prone Bloom's syndrome (BS), is a central factor of DNA damage repair by homologous recombination (HR) and genomic stability maintenance. Using independent cohorts of MM patients, we identified that high expression of BLM is associated with a poor outcome with a significant enrichment in replication stress signature. We provide evidence that chemical inhibition of BLM by the small molecule ML216 in HMCLs (human myeloma cell lines) leads to cell cycle arrest and increases apoptosis, likely by accumulation of DNA damage. BLM inhibition synergizes with the alkylating agent melphalan to efficiently inhibit growth and promote cell death in HMCLs. Moreover, ML216 treatment re-sensitizes melphalan-resistant cell lines to this conventional therapeutic agent. Altogether, these data suggest that inhibition of BLM in combination with DNA damaging agents could be of therapeutic interest in the treatment of MM, especially in those patients with high BLM expression and/or resistance to melphalan.

NAIRscore as a biomarker for the quality of immune response to neoantigens is related with an increased overall survival in multiple myeloma

Neoantigen provides a promising breakthrough in tumor immunotherapy, although only a subset of patients responds well due to the quality of their immune response. However, few biomarkers have been reported to measure the quality of immune response to neoantigens and to predict prognosis of patients with multiple myeloma (MM). Here, we first developed a neoantigen-prediction pipeline starting from outcomes of somatic mutations and gene-expression profiles. Given the expression of some specific marker genes, the human leukocyte antigen (HLA)-I score and the cytolytic score were evaluated respectively to reflect HLA-I molecular expression and CD8+ T/natural killer (NK) cell abundance. According to the process of the immune response to neoantigens, we comprehensively took neoantigen load, cytolytic score, and HLA-I score to construct a neoantigen immune response score (NAIRscore), in which the HLA-I score presented a hazard ratio (HR) of less than 1, while the cytolytic score and neoantigen load presented a HR of greater than 1. Meanwhile, NAIRscore presented a competitive advantage to stratify MM samples. Especially, those exhibiting high NAIRscore correlated with an increased overall survival (OS), echoing the underlying molecular signatures of lower driver-gene mutations and down-regulated immune response. Notably, an online tool based on this study is provided to identify neoantigens and predict OS.

Multiple Myeloma Uncovered Under Excessive Antacid and Chronic NSAID Use in a Young Female

Multiple myeloma (MM) is a plasma cell dyscrasia in which nearly all cases are diagnosed in patients over 40 years old. This report illustrates a case of a young female who presented with severe generalized weakness, acute kidney injury, hypercalcemia, and anemia. Her symptoms were initially attributed to chronic NSAID and antacid intake, especially given her young age. However, further workup was pursued to rule out other potential diagnoses despite her age. She was ultimately diagnosed with multiple myeloma and started on bortezomib, cyclophosphamide, and dexamethasone. This report emphasizes the importance of maintaining a broad differential diagnosis. Untrained physicians can easily overlook rare cases. Timely diagnosis and treatment are key, and therefore, a high degree of suspicion is crucial for this patient population.

Gene expression profiling and in vitro functional studies reveal RAD54L as a potential therapeutic target in multiple myeloma

Background

Current advances in the molecular biology of multiple myeloma (MM) are not sufficient to fully delineate the genesis and development of this disease.

Objective

This study aimed to identify molecular targets underlying MM pathogenesis.

Methods

mRNA expression profiling for 29 samples (19 MM samples, 7 MM cell lines and 3 controls) were obtained using microarray. We evaluated the in vitro effects of RAD54L gene silencing on the proliferation, apoptosis and cell cycle distribution in KMS-28BM human MM cells using siRNA approach. Cell proliferation was determined by MTS assay while apoptosis and cell cycle distribution were analysed with flow cytometry. Gene and protein expression was evaluated using RT-qPCR and ELISA, respectively.

Results

Microarray results revealed a total of 5124 differentially expressed genes (DEGs), in which 2696 and 2428 genes were up-regulated and down-regulated in MM compared to the normal controls, respectively (fold change ≥ 2.0; P < 0.05). Up-regulated genes (RAD54L, DIAPH3, SHCBP1, SKA3 and ANLN) and down-regulated genes (HKDC1, RASGRF2, CYSLTR2) have never been reported in association with MM. Up-regulation of RAD54L was further verified by RT-qPCR (P < 0.001). In vitro functional studies revealed that RAD54L gene silencing significantly induced growth inhibition, apoptosis (small changes) and cell cycle arrest in G0/G1 phase in KMS-28BM (P < 0.05). Silencing of RAD54L also decreased its protein level (P < 0.05).

Conclusions

This study has identified possible molecular targets underlying the pathogenesis of MM. For the first time, we reveal RAD54L as a potential therapeutic target in MM, possibly functioning in the cell cycle and checkpoint control.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13258-022-01272-7.

Serum Free Light-Chain Ratio at Diagnosis Is Associated with Early Renal Damage in Multiple Myeloma: A Case Series Real-World Study

The serum free light-chain (FLC) ratio is a sensitive tool for the differential diagnosis of plasma cell disorders and is biomarker of multiple myeloma (MM) progression from premalignant conditions. Here, we investigate the potential role of FLC ratio at diagnosis in identifying early renal damage in MM patients and other correlations with clinical, laboratory, and molecular findings. A total of 34 MM patients who had undergone autologous stem cell transplantation were included in this retrospective case series study, and FLC quantification was performed with nephelometric assays. In our study, sFLC ratio was significantly associated with light-chain MM and β-2 microglobulin levels, likely indicating a high disease burden at diagnosis, especially in patients without heavy chain M-protein at serum electrophoresis. Moreover, the sFLC ratio was inversely correlated with glomerular filtration rate, possibly identifying early renal damage in MM patients. Our preliminary results confirm the importance of early sFLC evaluation, especially in patients with the light-chain MM type and low disease burden, to minimize the risk of late renal failure.

Characteristics and clinical outcome of high-risk multiple myeloma patients in Korea (KMM 1805)

Optimal treatments for multiple myeloma (MM) patients with high-risk cytogenetics must be determined, but subgroup features are not well-defined. We used real-world data from the Korean Myeloma Registry (KMR) to analyze the characteristics and clinical outcomes of newly diagnosed MM patients with ≥ 1 high-risk cytogenetic abnormality: Group 1: t(4;14) or t(14;16); Group 2: del(17p); Group 3: t(4;14)/del(17p) or t(14;16)/del(17p). Overall, 347 high-risk patients were identified (males, 48.7%; median age, 63 years). Median progression-free survival (PFS) and overall survival (OS) were 19.0 months (95% CI 17.0-20.0) and 50.0 months (95% CI 37.0-61.0), respectively. PFS (p = 0.047) and OS (p = 0.020) differed significantly between groups. After stratification by transplant eligibility, PFS and OS were significantly poorer in Group 3 among transplant-eligible patients, and even poorer in those with gain(1q). Patients stratified by cytogenetic abnormality and revised International Staging System (R-ISS) had significantly different PFS (p < 0.001) and OS (p = 0.003), with the worst survival in R-ISS III/Group 3 (median OS 21.0 months). Higher number of high-risk cytogenetic abnormalities was a negative prognostic marker for PFS and OS (p < 0.001). Real-world KMR data showed that risk factors for poor prognosis of MM patients included del(17p), R-ISS stage, and number of cytogenetic abnormalities.

Single-Cell Proteomics and Tumor RNAseq Identify Novel Pathways Associated With Clofazimine Sensitivity in PI- and IMiD- Resistant Myeloma, and Putative Stem-Like Cells

Multiple myeloma (MM) is an incurable plasma cell malignancy with dose-limiting toxicities and inter-individual variation in response/resistance to the standard-of-care/primary drugs, proteasome inhibitors (PIs), and immunomodulatory derivatives (IMiDs). Although newer therapeutic options are potentially highly efficacious, their costs outweigh the effectiveness. Previously, we have established that clofazimine (CLF) activates peroxisome proliferator-activated receptor-γ, synergizes with primary therapies, and targets cancer stem-like cells (CSCs) in drug-resistant chronic myeloid leukemia (CML) patients. In this study, we used a panel of human myeloma cell lines as in vitro model systems representing drug-sensitive, innate/refractory, and clonally-derived acquired/relapsed PI- and cereblon (CRBN)-negative IMiD-resistant myeloma and bone marrow-derived CD138+ primary myeloma cells obtained from patients as ex vivo models to demonstrate that CLF shows significant cytotoxicity against drug-resistant myeloma as single-agent and in combination with PIs and IMiDs. Next, using genome-wide transcriptome analysis (RNA-sequencing), single-cell proteomics (CyTOF; Cytometry by time-of-flight), and ingenuity pathway analysis (IPA), we identified novel pathways associated with CLF efficacy, including induction of ER stress, autophagy, mitochondrial dysfunction, oxidative phosphorylation, enhancement of downstream cascade of p65-NFkB-IRF4-Myc downregulation, and ROS-dependent apoptotic cell death in myeloma. Further, we also showed that CLF is effective in killing rare refractory subclones like side populations that have been referred to as myeloma stem-like cells. Since CLF is an FDA-approved drug and also on WHO's list of safe and effective essential medicines, it has strong potential to be rapidly re-purposed as a safe and cost-effective anti-myeloma drug.

Revisiting Proteasome Inhibitors: Molecular Underpinnings of Their Development, Mechanisms of Resistance and Strategies to Overcome Anti-Cancer Drug Resistance

Proteasome inhibitors have shown relevant clinical activity in several hematological malignancies, namely in multiple myeloma and mantle cell lymphoma, improving patient outcomes such as survival and quality of life, when compared with other therapies. However, initial response to the therapy is a challenge as most patients show an innate resistance to proteasome inhibitors, and those that respond to the therapy usually develop late relapses suggesting the development of acquired resistance. The mechanisms of resistance to proteasome inhibition are still controversial and scarce in the literature. In this review, we discuss the development of proteasome inhibitors and the mechanisms of innate and acquired resistance to their activity—a major challenge in preclinical and clinical therapeutics. An improved understanding of these mechanisms is crucial to guiding the design of new and more effective drugs to tackle these devastating diseases. In addition, we provide a comprehensive overview of proteasome inhibitors used in combination with other chemotherapeutic agents, as this is a key strategy to combat resistance.

secDrug: a pipeline to discover novel drug combinations to kill drug-resistant multiple myeloma cells using a greedy set cover algorithm and single-cell multi-omics

Multiple myeloma, the second-most common hematopoietic malignancy in the United States, still remains an incurable disease with dose-limiting toxicities and resistance to primary drugs like proteasome inhibitors (PIs) and Immunomodulatory drugs (IMiDs).We have created a computational pipeline that uses pharmacogenomics data-driven optimization-regularization/greedy algorithm to predict novel drugs ("secDrugs") against drug-resistant myeloma. Next, we used single-cell RNA sequencing (scRNAseq) as a screening tool to predict top combination candidates based on the enrichment of target genes. For in vitro validation of secDrugs, we used a panel of human myeloma cell lines representing drug-sensitive, innate/refractory, and acquired/relapsed PI- and IMiD resistance. Next, we performed single-cell proteomics (CyTOF or Cytometry time of flight) in patient-derived bone marrow cells (ex vivo), genome-wide transcriptome analysis (bulk RNA sequencing), and functional assays like CRISPR-based gene editing to explore molecular pathways underlying secDrug efficacy and drug synergy. Finally, we developed a universally applicable R-software package for predicting novel secondary therapies in chemotherapy-resistant cancers that outputs a list of the top drug combination candidates with rank and confidence scores.Thus, using 17AAG (HSP90 inhibitor) + FK866 (NAMPT inhibitor) as proof of principle secDrugs, we established a novel pipeline to introduce several new therapeutic options for the management of PI and IMiD-resistant myeloma.

Genetic Aberrations and Interaction of NEK2 and TP53 Accelerate Aggressiveness of Multiple Myeloma

It has been previously shown that (never in mitosis gene A)-related kinase 2 (NEK2) is upregulated in multiple myeloma (MM) and contributes to drug resistance. However, the mechanisms behind this upregulation remain poorly understood. In this study, it is found that amplification of NEK2 and hypermethylation of distal CpG islands in its promoter correlate strongly with increased NEK2 expression. Patients with NEK2 amplification have a poor rate of survival and often exhibit TP53 deletion, which is an independent prognostic factor in MM. This combination of TP53 knockout and NEK2 overexpression induces asymmetric mitosis, proliferation, drug resistance, and tumorigenic behaviors in MM in vitro and in vivo. In contrast, delivery of wild type p53 and suppression of NEK2 in TP53^-/- MM cell lines inhibit tumor formation and enhance the effect of Bortezomib against MM. It is also discovered that inactivating p53 elevates NEK2 expression genetically by inducing NEK2 amplification, transcriptionally by increased activity of cell cycle-related genes like E2F8 and epigenetically by upregulating DNA methyltransferases. Dual defects of TP53 and NEK2 may define patients with the poorest outcomes in MM with p53 inactivation, and NEK2 may serve as a novel therapeutic target in aggressive MM with p53 abnormalities.

Epigenomic reprogramming via HRP2-MINA dictates response to proteasome inhibitors in multiple myeloma with t(4;14) translocation

The chromosomal t(4;14) (p16;q32) translocation drives high expression of histone methyltransferase nuclear SET domain–containing 2 (NSD2) and plays vital roles in multiple myeloma (MM) evolution and progression. However, the mechanisms of NSD2-driven epigenomic alterations in chemoresistance to proteasome inhibitors (PIs) are not fully understood. Using a CRISPR/Cas9 sgRNA library in a bone marrow–bearing MM model, we found that hepatoma-derived growth factor 2 (HRP2) was a suppressor of chemoresistance to PIs and that its downregulation correlated with a poor response and worse outcomes in the clinic. We observed suppression of HRP2 in bortezomib-resistant MM cells, and knockdown of HRP2 induced a marked tolerance to PIs. Moreover, knockdown of HRP2 augmented H3K27me3 levels, consequentially intensifying transcriptome alterations promoting cell survival and restriction of ER stress. Mechanistically, HRP2 recognized H3K36me2 and recruited the histone demethylase MYC-induced nuclear antigen (MINA) to remove H3K27me3. Tazemetostat, a highly selective epigenetic inhibitor that reduces H3K27me3 levels, synergistically sensitized the anti-MM effects of bortezomib both in vitro and in vivo. Collectively, these results provide a better understanding of the origin of chemoresistance in patients with MM with the t(4;14) translocation and a rationale for managing patients with MM who have different genomic backgrounds.

B-cell maturation antigen targeting strategies in multiple myeloma treatment, advantages and disadvantages

B cell maturation antigen (BCMA), a transmembrane glycoprotein member of the tumor necrosis factor receptor superfamily 17 (TNFRSF17), highly expressed on the plasma cells of Multiple myeloma (MM) patients, as well as the normal population. BCMA is used as a biomarker for MM. Two members of the TNF superfamily proteins, including B-cell activating factor (BAFF) and A proliferation-inducing ligand (APRIL), are closely related to BCMA and play an important role in plasma cell survival and progression of MM. Despite the maximum specificity of the monoclonal antibody technologies, introducing the tumor-specific antigen(s) is not applicable for all malignancies, such as MM that there plenty of relatively specific antigens such as GPCR5D, MUC1, SLAMF7 and etc., but higher expression of BCMA on these cells in comparison with normal ones can be regarded as a relatively exclusive marker. Currently, different monoclonal antibody (mAb) technologies applied in anti-MM therapies such as daratuzumab, SAR650984, GSK2857916, and CAR-T cell therapies are some of these tools that are reviewed in the present manuscript. By the way, the structure, function, and signaling of the BCMA and related molecule(s) role in normal plasma cells and MM development, evaluated as well as the potential side effects of its targeting by different CAR-T cells generations. In conclusion, BCMA can be regarded as an ideal molecule to be targeted in immunotherapeutic methods, regarding lower potential systemic and local side effects.

Potential of a sphingosine 1‑phosphate receptor antagonist and sphingosine kinase inhibitors as targets for multiple myeloma treatment

Sphingosine 1-phosphate (S1P) is a bioactive lipid involved in cancer progression through its binding to S1P receptors (S1PRs). However, the association between multiple myeloma (MM) and S1P is unclear. The current study aimed to investigate the potential anti-cancer effects of fingolimod and sphingosine kinase (SK) inhibitors in myeloma cells and the effects of S1P-induced chemoresistance and neovascularization on MM cell proliferation. MM cell lines were treated with the S1PR1 antagonist fingolimod and the SK inhibitors ABC294640 and SK1-I, after which cell proliferation was measured. Protein expression was also assessed under each condition using immunoblotting. Serum S1P levels in patients with MM, monoclonal gammopathy of undetermined significance and healthy volunteers were assessed. Human umbilical vessel cells (HUVECs) were co-cultured with anti-S1P agents to assess the effect on cell migration. All treatments suppressed myeloma cell proliferation and caspase-3-mediated apoptosis by suppressing S1P activity. These findings suggest that S1P activation is associated with proliferation and survival for MM cells. S1P attenuated the proteosome inhibitor (PI) effect, while the anti-S1P agents recovered the effect. In addition, S1P promoted the migration and proliferation of HUVECs, whereas the S1P inhibitors reduced the influence of S1P. This study highlights the therapeutic potential of anti-S1P agents for MM treatment. Inhibition of S1P function may overcome resistance to PI developed by myeloma cells and inhibit the changes to the bone marrow microenvironment via neovascularization.

Structural and Ultrastructural Analysis of the Multiple Myeloma Cell Niche and a Patient-Specific Model of Plasma Cell Dysfunction

Multiple myeloma (MM) is a deadly, incurable malignancy in which antibody-secreting plasma cells (PCs) become neoplastic. Previous studies have shown that the PC niche plays a role cancer progression. Bone marrow (BM) cores from MM and a premalignant condition known as monoclonal gammopathy of unknown significance (MGUS) patients were analyzed with confocal and transmission electron microscopy. The BM aspirates from these patients were used to generate 3D PC cultures. These in vitro cultures were then assayed for the molecular, cellular, and ultrastructural hallmarks of dysfunctional PC at days 1 and 5. In vivo, evidence of PC endoplasmic reticulum stress was found in both MM and MGUS BM; however, evidence of PC autophagy was found only in MM BM. Analysis of in vitro cultures found that MM PC can survive and maintain a differentiated phenotype over an unprecedented 5 days, had higher levels of paraprotein production when compared to MGUS-derived cultures, and showed evidence of PC autophagy as well. Increased fibronectin deposition around PC associated with disease severity and autophagy dysregulation was also observed. 3D cultures constructed from BM aspirates from MGUS and MM patients allow for long-term culture of functional PC while maintaining their distinct morphological phenotypes.

Multiple Myeloma Involving Left Hemicranium

Multiple myeloma (MM) is a malignant neoplasm of bone marrow affecting plasma cells. It is commonly seen as multiple punched-out lesions in the skull bone as a characteristic feature. Its presentation as hemicranial involvement with intracranial extension is rare. A 46-year-old male presented with left side scalp swelling, prominent over parietal region. X-ray showed multiple punched out lesions involving left hemicranium. CT and MRI brain showed intracranial extension of lesion without brain parenchyma invasion. He was treated with biopsy of lesion followed by chemotherapy.

Checkpoint Inhibitors in Multiple Myeloma: Intriguing Potential and Unfulfilled Promises

Immune dysregulation and alteration of the bone marrow microenvironment allowing plasma cells to escape immune surveillance are well-known factors associated with the proliferation of clonal plasma cells and development of multiple myeloma (MM). Whilst immunotherapeutic approaches are now commonplace in a wide spectrum of malignancies, this aberration of myeloma development gives rise to the biological rationale for the use of immune checkpoint inhibitors (ICIs) in MM. However, the initial experience with these agents has been challenging with limited single agent efficacy, significant toxicity, and side effects. Herein, we review the biological and immunological aspects of MM and ICIs. We discuss the basic biology of immune checkpoint inhibitors, mechanisms of resistance, and drug failure patterns, review the published clinical trial data for ICIs in MM, and look towards the future of ICIs for MM treatment.

Allogeneic Stem Cell Transplantation in Multiple Myeloma

The development of new inhibitory and immunological agents and combination therapies significantly improved response rates and survival of patients diagnosed with multiple myeloma (MM) in the last decade, but the disease is still considered to be incurable by current standards and the prognosis is dismal especially in high-risk groups and in relapsed and/or refractory patients. Allogeneic hematopoietic stem cell transplantation (allo-SCT) may enable long-term survival and even cure for individual patients via an immune-mediated graft-versus-myeloma (GvM) effect, but remains controversial due to relevant transplant-related risks, particularly immunosuppression and graft-versus-host disease, and a substantial non-relapse mortality. The decreased risk of disease progression may outweigh this treatment-related toxicity for young, fit patients in high-risk constellations with otherwise often poor long-term prognosis. Here, allo-SCT should be considered within clinical trials in first-line as part of a tandem approach to separate myeloablation achieved by high-dose chemotherapy with autologous SCT, and following allo-SCT with a reduced-intensity conditioning to minimize treatment-related organ toxicities but allow GvM effect. Our review aims to better define the role of allo-SCT in myeloma treatment particularly in the context of new immunomodulatory approaches.

Beta-Caryophyllene Exhibits Anti-Proliferative Effects through Apoptosis Induction and Cell Cycle Modulation in Multiple Myeloma Cells

Cannabinoid receptors, which are widely distributed in the body, have been considered as possible pharmacological targets for the management of several tumors. Cannabinoid type 2 receptors (CB2Rs) belong to the G protein-coupled receptor family and are mainly expressed in hematopoietic and immune cells, such as B-cells, T-cells, and macrophages; thus, CB2R activation might be useful for treating cancers affecting plasma cells, such as multiple myeloma (MM). Previous studies have shown that CB2R stimulation may have anti-proliferative effects; therefore, the purpose of the present study was to explore the antitumor effect of beta-caryophyllene (BCP), a CB2R agonist, in an in vitro model of MM. Dexamethasone-resistant (MM.1R) and sensitive (MM.1S) human multiple myeloma cell lines were used in this study. Cells were treated with different concentrations of BCP for 24 h, and a group of cells was pre-incubated with AM630, a specific CB2R antagonist. BCP treatment reduced cell proliferation through CB2R stimulation; notably, BCP considerably increased the pro-apoptotic protein Bax and decreased the anti-apoptotic molecule Bcl-2. Furthermore, an increase in caspase 3 protein levels was detected following BCP incubation, thus demonstrating its anti-proliferative effect through apoptosis activation. In addition, BCP regulated AKT, Wnt1, and beta-catenin expression, showing that CB2R stimulation may decrease cancer cell proliferation by modulating Wnt/β-catenin signaling. These effects were counteracted by AM630 co-incubation, thus confirming that BCP's mechanism of action is mainly related to CB2R modulation. A decrease in β-catenin regulated the impaired cell cycle and especially promoted cyclin D1 and CDK 4/6 reduction. Taken together, these data revealed that BCP might have significant and effective anti-cancer and anti-proliferative effects in MM cells by activating apoptosis, modulating different molecular pathways, and downregulating the cell cycle.

Anti-tumor activity of the pan-RAF inhibitor TAK-580 in combination with KPT-330 (selinexor) in multiple myeloma

RAS/RAF/MEK/ERK pathway inhibitors exhibit significant anti-tumor effects against various tumor types, including multiple myeloma (MM), and they are predicted to play a pivotal role in precision medicine. The XPO1 inhibitor KPT-330 has also exhibited promising efficacy in combination with other novel drugs in treating relapsed/refractory MM (RRMM). In this study, we explored the anti-tumor effects of a combination of the pan-RAF inhibitor TAK-580 and KPT-330. Importantly, TAK-580 enhanced KPT-330-induced cytotoxicity and apoptosis in human myeloma cell lines and primary myeloma cells from RRMM patients. Moreover, TAK-580 and KPT-330 synergistically inhibited nuclear phospho-FOXO3a and enhanced cytoplasmic phospho-FOXO3a in MM cells, leading to cytoplasmic enhanced Bim expression and finally apoptosis. This indicates that TAK-580 enhances KPT-330-induced cytotoxicity and apoptosis primarily via the FOXO3a-Bim axis. In addition, TAK-580 enhanced the cytotoxicity of KPT-330 against MM cells even in the presence of IGF-1. Taken together, our results demonstrate that a combination of pan-RAF inhibitor and XPO1 inhibitor is a potential therapeutic option in treating MM.

[Multiple myeloma from the pathologist's perspective]

BACKGROUND

Multiple myeloma (MM) is one of the most common hematological neoplasms and accounts for approximately 1% of human cancers.

OBJECTIVES

Description of current diagnostics and classification of MM and related plasma cell neoplasms from the pathology viewpoint.

MATERIALS AND METHODS

Current knowledge regarding pathology and genetics of MM is summarized and tissue-based diagnostics following international consensus classifications and the current S3 guideline are described.

RESULTS

MM and related neoplasms are composed of malignant plasma cells that secrete a monoclonal immunoglobulin, which is an important parameter of disease activity. MM shows a multistage development. Almost all cases are preceded by a clinically inapparent precursor lesion, monoclonal gammopathy of undetermined significance (MGUS), which can progress to smoldering myeloma with a higher tumor burden, but absence of organ damage. Systemic MM needs to be discerned from the localized forms, solitary osseous and primary extramedullary plasmacytoma. MM is genetically very heterogeneous and can be broadly subdivided into two cytogenetic groups, cases with primary IGH translocations and cases with hyperdiploidy. Intratumoral genetic heterogeneity is frequently pronounced and correlates with the size of focal lesions in imaging.

CONCLUSIONS

Diagnosis of plasma cell neoplasms is done according to the criteria of the International Myeloma Working Group (IWMG) and requires interdisciplinary evaluation of clinical, serological, pathological and radiological features. In addition to clinical parameters, molecular markers, especially cytogenetic aberrations, are of great prognostic relevance.

Autophagy in Hematological Malignancies: Molecular Aspects in Leukemia and Lymphoma

The organization of the hematopoietic system is dependent on hematopoietic stem cells (HSCs) that are capable of self-renewal and multilineage differentiation to produce different blood cell lines. Autophagy has a central role in energy production and metabolism of the cells during starvation, cellular stress adaption, and removing mechanisms for aged or damaged organelles. The role and importance of autophagy pathways are becoming increasingly recognized in the literature because these pathways can be useful in organizing intracellular circulation, molecular complexes, and organelles to meet the needs of various hematopoietic cells. There is supporting evidence in the literature that autophagy plays an emerging role in the regulation of normal cells and that it also has important features in malignant hematopoiesis. Understanding the molecular details of the autophagy pathway can provide novel methods for more effective treatment of patients with leukemia. Overall, our review will emphasize the role of autophagy and its different aspects in hematological malignant neoplasms.

SY-1530, a highly selective BTK inhibitor, effectively treats B-cell malignancies by blocking B-cell activation

OBJECTIVE

B-cell antigen receptor (BCR) signaling is required to maintain the physiological functions of normal B cells and plays an important pathogenic role in B-cell malignancies. Bruton tyrosine kinase (BTK), a critical mediator of BCR signaling, is an attractive target for the treatment of B-cell malignancies. This study aimed to identify a highly potent and selective BTK inhibitor.

METHODS

Homogeneous time-resolved fluorescence assays were used to screen BTK inhibitors. Typhoon fluorescence imaging and Western blot analysis were used to confirm the effects of SY-1530 on the BCR signaling pathway. Additionally, the anti-tumor activities of SY-1530 were evaluated in TMD8 xenografts and spontaneous canine B-cell lymphoma.

RESULTS

We found a novel irreversible and non-competitive inhibitor of BTK, SY-1530, which provided dose-dependent and time-dependent inhibition. SY-1530 selectively bound to BTK rather than inducible T-cell kinase; consequently, it did not significantly affect T-cell receptor signaling and caused limited off-target effects. SY-1530 blocked the BCR signaling pathway through down-regulation of BTK activity, thus leading to impaired phosphorylation of BTK and its downstream kinases. Moreover, SY-1530 induced apoptosis in a caspase-dependent manner and efficaciously inhibited tumor growth in mouse xenograft models of B-cell malignancy (P < 0.001). SY-1530 also induced positive clinical responses in spontaneous canine B-cell lymphoma.

CONCLUSIONS

SY-1530 is an irreversible and selective BTK inhibitor that shows inhibitory effects on B-cell malignancies by blocking the BCR signaling pathway. Therefore, it may be a promising therapeutic approach for the treatment of B-cell malignancies.

Orthogonal targeting of osteoclasts and myeloma cells for radionuclide stimulated dynamic therapy induces multidimensional cell death pathways

Rationale: Multiple myeloma (MM) is a multifocal malignancy of bone marrow plasma cells, characterized by vicious cycles of remission and relapse that eventually culminate in death. The disease remains mostly incurable largely due to the complex interactions between the bone microenvironment (BME) and MM cells (MMC). In the “vicious cycle” of bone disease, abnormal activation of osteoclasts (OCs) by MMC causes severe osteolysis, promotes immune evasion, and stimulates the growth of MMC. Disrupting these cancer-stroma interactions would enhance treatment response.

Methods: To disrupt this cycle, we orthogonally targeted nanomicelles (NM) loaded with non-therapeutic doses of a photosensitizer, titanocene (TC), to VLA-4 (α4ß1, CD49d/CD29) expressing MMC (MM1.S) and αvß3 (CD51/CD61) expressing OC. Concurrently, a non-lethal dose of a radiopharmaceutical, ¹⁸F-fluorodeoxyglucose ([¹⁸F]FDG) administered systemically interacted with TC (radionuclide stimulated therapy, RaST) to generate cytotoxic reactive oxygen species (ROS). The in vitro and in vivo effects of RaST were characterized in MM1.S cell line, as well as in xenograft and isograft MM animal models.

Results: Our data revealed that RaST induced non-enzymatic hydroperoxidation of cellular lipids culminating in mitochondrial dysfunction, DNA fragmentation, and caspase-dependent apoptosis of MMC using VLA-4 avid TC-NMs. RaST upregulated the expression of BAX, Bcl-2, and p53, highlighting the induction of apoptosis via the BAK-independent pathway. The enhancement of multicopper oxidase enzyme F5 expression, which inhibits lipid hydroperoxidation and Fenton reaction, was not sufficient to overcome RaST-induced increase in the accumulation of irreversible function-perturbing α,ß-aldehydes that exerted significant and long-lasting damage to both DNA and proteins. In vivo, either VLA-4-TC-NM or αvß3-TC-NMs RaST induced a significant therapeutic effect on immunocompromised but not immunocompetent MM-bearing mouse models. Combined treatment with both VLA-4-TC-NM and αvß3-TC-NMs synergistically inhibited osteolysis, reduced tumor burden, and prevented rapid relapse in both in vivo models of MM.

Conclusions: By targeting MM and bone cells simultaneously, combination RaST suppressed MM disease progression through a multi-prong action on the vicious cycle of bone cancer. Instead of using the standard multidrug approach, our work reveals a unique photophysical treatment paradigm that uses nontoxic doses of a single light-sensitive drug directed orthogonally to cancer and bone cells, followed by radionuclide-stimulated generation of ROS to inhibit tumor progression and minimize osteolysis in both immunocompetent murine and immunocompromised human MM models.

Growth inhibition and apoptosis of human multiple myeloma cells induced by 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid derivatives

Multiple myeloma is a blood cell cancer and can cause symptoms such as bone loss and fatigue. Recent studies have shown that the bone marrow microenvironment may mediate tumor proliferation, drug resistance, and migration of the multiple myeloma cells. Synthetic triterpenoids have been used for the treatment of cancer due to their antiproliferative and anti-inflammatory effects. The objective of this study is to examine the effect of 2-cyano-3, 12 dioxoolean-1,9-dien-28-oic acid (CDDO) derivatives on human multiple myeloma cells. Three CDDO derivatives, such as CDDO-methyl ester, CDDO-trifluroethyl amide, and CDDO-imidazolide (Im), were tested on the growth of human multiple myeloma cells. Our results show that all CDDO derivatives decrease the viability of multiple myeloma cells in a dose- and time-dependent manner, with CDDO-Im being the most potent. CDDO-Im was selected to investigate whether its inhibitory effect on multiple myeloma cell growth is due to cell cycle arrest and induction of apoptosis. The results suggest that CDDO-Im may inhibit cell cycle progression in the G0/G1 phase and induce the intrinsic apoptotic pathway. The effect of CDDO-Im on multiple myeloma cells was evaluated in a Transwell model using myeloma cells co-culturing with human HS-5 stromal cells to simulate the bone marrow microenvironment in vitro. The results showed that CDDO-Im induced multiple myeloma cell apoptosis in the presence of HS-5 cells, albeit to a lower extent than in multiple myeloma cells cultured alone. In conclusion, our data suggest that CDDO-Im inhibits the growth of multiple myeloma cells, either cultured alone or co-cultured with bone marrow stromal cells, through the induction of apoptosis.

The nonreceptor tyrosine kinase SRMS inhibits autophagy and promotes tumor growth by phosphorylating the scaffolding protein FKBP51

Nutrient-responsive protein kinases control the balance between anabolic growth and catabolic processes such as autophagy. Aberrant regulation of these kinases is a major cause of human disease. We report here that the vertebrate nonreceptor tyrosine kinase Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristylation sites (SRMS) inhibits autophagy and promotes growth in a nutrient-responsive manner. Under nutrient-replete conditions, SRMS phosphorylates the PHLPP scaffold FK506-binding protein 51 (FKBP51), disrupts the FKBP51-PHLPP complex, and promotes FKBP51 degradation through the ubiquitin-proteasome pathway. This prevents PHLPP-mediated dephosphorylation of AKT, causing sustained AKT activation that promotes growth and inhibits autophagy. SRMS is amplified and overexpressed in human cancers where it drives unrestrained AKT signaling in a kinase-dependent manner. SRMS kinase inhibition activates autophagy, inhibits cancer growth, and can be accomplished using the FDA-approved tyrosine kinase inhibitor ibrutinib. This illuminates SRMS as a targetable vulnerability in human cancers and as a new target for pharmacological induction of autophagy in vertebrates.

This study describes the discovery and characterization of a nutrient-sensitive signaling pathway that drives growth and inhibits autophagy in mammalian cells. This pathway, which involves the non-receptor tyrosine kinase SRMS and the PHLPP scaffold protein FKBP51, promotes tumor growth and is amenable to pharmacological inhibition.

AKT signaling restrains tumor suppressive functions of FOXO transcription factors and GSK3 kinase in multiple myeloma

The phosphatidylinositide-3 kinases and the downstream mediator AKT drive survival and proliferation of multiple myeloma (MM) cells. AKT signaling is active in MM and has pleiotropic effects; however, the key molecular aspects of AKT dependency in MM are not fully clear. Among the various downstream AKT targets are the Forkhead box O (FOXO) transcription factors (TFs) and glycogen synthase kinase 3 (GSK3), which are negatively regulated by AKT signaling. Here we show that abrogation of AKT signaling in MM cells provokes cell death and cell cycle arrest, which crucially depends on both FOXO TFs and GSK3. Based on gene expression profiling, we defined a FOXO-repressed gene set that has prognostic significance in a large cohort of patients with MM, indicating that AKT-mediated gene activation is associated with inferior overall survival. We further show that AKT signaling stabilizes the antiapoptotic myeloid cell leukemia 1 (MCL1) protein by inhibiting FOXO- and GSK3-mediated MCL1 turnover. In concordance, abrogation of AKT signaling greatly sensitized MM cells for an MCL1-targeting BH3-mimetic, which is currently in clinical development. Taken together, our results indicate that AKT activity is required to restrain the tumor-suppressive functions of FOXO and GSK3, thereby stabilizing the antiapoptotic protein MCL1 in MM. These novel insights into the role of AKT in MM pathogenesis and MCL1 regulation provide opportunities to improve targeted therapy for patients with MM.

Che-1/AATF-induced transcriptionally active chromatin promotes cell proliferation in multiple myeloma

Multiple myeloma (MM) is a hematologic malignancy produced by a clonal expansion of plasma cells and characterized by abnormal production and secretion of monoclonal antibodies. This pathology exhibits an enormous heterogeneity resulting not only from genetic alterations but also from several epigenetic dysregulations. Here we provide evidence that Che-1/AATF (Che-1), an interactor of RNA polymerase II, promotes MM proliferation by affecting chromatin structure and sustaining global gene expression. We found that Che-1 depletion leads to a reduction of "active chromatin" by inducing a global decrease of histone acetylation. In this context, Che-1 directly interacts with histones and displaces histone deacetylase class I members from them. Strikingly, transgenic mice expressing human Che-1 in plasma cells develop MM with clinical features resembling those observed in the human disease. Finally, Che-1 downregulation decreases BRD4 chromatin accumulation to further sensitize MM cells to bromodomain and external domain inhibitors. These findings identify Che-1 as a promising target for MM therapy, alone or in combination with bromodomain and external domain inhibitors.

Role of ARK5 in cancer and other diseases (Review)

Malignant tumors are often exposed to hypoxic and glucose-starved microenvironments. AMP-activated protein kinase (AMPK) is an energy sensor that is stimulated during energy-deficient conditions and protects cells from hypoxic injury by regulating metabolism. AMPK-related protein kinase 5 (ARK5) is a member of the catalytic sub-unit of the AMPK family and has an important role in energy regulation and hypoxia. ARK5 is regulated by Akt and liver kinase B1 and is associated with numerous tumor-related molecules to exert the negative effects of tumors. Studies have revealed ARK5 overexpression in cases of tumor invasion and metastasis and a positive association with the degree of cancer cell malignancy, which is regarded as a key element in determining cancer prognosis. Furthermore, ARK5 downregulation improves drug sensitivity through the epithelial-mesenchymal transition pathway, indicating that it may be a potential therapeutic target. In other non-cancer conditions, ARK5 has various roles in neurodegenerative diseases (Alzheimer's and Huntington's disease), renal disorders (diabetic nephropathy and renal fibrosis) and physiological processes (striated muscle generation). In the present review, the upstream and downstream molecular pathways of ARK5 in cancer and other diseases are described and potential therapeutic strategies are discussed.

Suppression of multiple myeloma by mitochondrial targeting

Treatment of multiple myeloma (MM) aims at inducing cell apoptosis by surpassing the limited capacity of MM cells to cope with oxidative stress. MM cell survival may further be suppressed by limiting cellular cholesterol. Long-chain fatty acid analogs of the MEDICA series promote mitochondrial stress and inhibit cholesterol biosynthesis, thus prompting us to verify their efficacy and mode-of-action in suppressing MM cell survival, in comparison to bortezomib. MEDICA analog is shown here to effectively suppress survival of MM cells, and to inhibit growth of MM xenograft. Suppression of MM cell survival by MEDICA is accompanied by inhibition of the STAT3, MAPK and the mTORC1 transduction pathways due to mitochondrial oxidative stress. MEDICA-induced oxidative stress is abrogated by added exogenous cholesterol. Suppression of MM cell survival by bortezomib is similarly driven by bortezomib-induced oxidative stress, being abrogated by added cholesterol. In line with that, the time-to-best-response of MM patients to bortezomib-based treatment protocols is shown to be positively correlated with their plasma cholesterol level. MEDICA profile may indicate novel therapeutic potential in the management of MM.

Targeting phosphoinositide 3-kinases and histone deacetylases in multiple myeloma

Background

Multiple myeloma (MM) is a type of hematological malignancy affecting the functions of plasma cells. The treatment of MM patients has changed dramatically with the use of new agents. However, unfortunately, it is still incurable. Therefore, a new approach for treating MM is still needed to improve patient outcomes.

Methods

Because the histone deacetylase (HDAC) and phosphoinositide 3-kinase (PI3K) pathway is a key signal in cancer cell biology, we investigated whether dual HDAC and PI3K inhibitors could suppress the myeloma cells.

Results

Gene expression of HDACs is high in myeloma cells. CUDC-907, a dual inhibitor of PI3K and HDAC, inhibits HDAC activity. Akt activity and expression of BCL-XL, MCL-1, and NF-κB p65 were reduced by CUDC-907 in a dose-dependent manner. The number of apoptotic and caspase 3/7-positive cells also increased in the myeloma cells. Combined treatment of myeloma cells with carfilzomib and CUDC-907 increased cytotoxicity compared to that observed with each drug alone.

Conclusions

Data from this study suggested that the administration of CUDC-907 might be a powerful strategy against myeloma cells, to enhance the cytotoxic effects of proteasome inhibitors.

Perspectives for the Use of CAR-T Cells for the Treatment of Multiple Myeloma

During recent years considerable progress has been made in the treatment of multiple myeloma. However, despite the current improvements in the prognosis of this malignancy, it always ends with relapse, and therefore new therapy approaches for destroying resistant cancer cells are needed. Presently, there is great hope being placed in the use of immunotherapy against refractory/relapsed multiple myeloma which is unresponsive to any other currently known drugs. The most promising one is CAR-T cell therapy which has already shown tremendous success in treating other malignancies such as acute lymphoblastic leukaemia (ALL) and could potentially be administered to multiple myeloma patients. CAR-T cells equipped with receptors against BCMA (B-cell maturation antigen), which is a surface antigen that is highly expressed on malignant cells, are now of great interest in this field with significant results in clinical trials. Furthermore, CAR-T cells with other receptors and combinations of different strategies are being intensively studied. However, even with CAR-T cell therapy, the majority of patients eventually relapse, which is the greatest limitation of this therapy. Serious adverse events such as cytokine release syndrome or neurotoxicity should also be considered as possible side effects of CAR-T cell therapy. Here, we discuss the results of CAR-T cell therapy in the treatment of multiple myeloma, where we describe its main advantages and disadvantages. Additionally, we also describe the current results that have been obtained on using combinations of CAR-T cell therapies with other drugs for the treatment of multiple myeloma.