Polycomb-like Protein 3 Induces Proliferation and Drug Resistance in Multiple Myeloma and Is Regulated by miRNA-15a

PHF19 before and post induction treatment possess favorable potency of reflecting treatment response to protease inhibitors, event-free survival, and overall survival in multiple myeloma patients

OBJECTIVE

Plant homeodomain finger protein 19 (PHF19) regulates hematopoietic stem cell differentiation and promotes multiple myeloma (MM) progression. This study intended to explore the potency of PHF19 at baseline and post induction treatment in estimating treatment response to protease inhibitors and survival in MM patients.

METHODS

This retrospective study screened 69 MM patients who received protease inhibitors with bone marrow (BM) samples available at both baseline and post induction treatment. Twenty healthy BM donors were included as healthy controls (HCs). PHF19 in plasma cells from BM was quantified by reverse transcription-quantitative polymerase chain reaction.

RESULTS

PHF19 at baseline and post induction treatment in MM patients were increased than in HCs. In MM patients, PHF19 was declined post induction treatment. Elevated PHF19 at baseline and post induction treatment were correlated with renal impairment, beta-2-microglobulin ≥5.5 mg/L, t (4; 14), higher international staging system (ISS) stage, and higher revised ISS (R-ISS) stage. Concerning treatment response, PHF19 at baseline and post induction treatment were negatively associated with complete response and overall response rate. Notably, abnormal PHF19 (above 95% quantile value of PHF19 in HCs) at baseline and post induction treatment were linked with shortened event-free survival (EFS) and overall survival (OS). After adjustment, abnormal PHF19 post induction treatment was independently related to shortened EFS (hazard ratio = 2.474) and OS (hazard ratio = 3.124).

CONCLUSION

PHF19 is aberrantly high and declines post induction therapy, which simultaneously reflects unfavorable treatment response to protease inhibitors as well as shorter EFS and OS in MM patients.

CRIP1 involves the pathogenesis of multiple myeloma via dual-regulation of proteasome and autophagy

BACKGROUND

Multiple myeloma (MM) is an incurable hematological malignancy of the plasma cells. The maintenance of protein homeostasis is critical for MM cell survival. Elevated levels of paraproteins in MM cells are cleared by proteasomes or lysosomes, which are independent but inter-connected with each other. Proteasome inhibitors (PIs) work as a backbone agent and successfully improved the outcome of patients; however, the increasing activity of autophagy suppresses the sensitivity to PIs treatment.

METHODS

The transcription levels of CRIP1 were explored in plasma cells obtained from healthy donors, patients with newly diagnosed multiple myeloma (NDMM), and relapsed/refractory multiple myeloma (RRMM) using Gene expression omnibus datasets. Doxycycline-inducible CRIP1-shRNA and CRIP1 overexpressed MM cell lines were constructed to explore the role of CRIP1 in MM pathogenesis. Proliferation, invasion, migration, proteasome activity and autophagy were examined in MM cells with different CRIP1 levels. Co-immunoprecipitation (Co-IP) with Tandem affinity purification/Mass spectrum (TAP/MS) was performed to identify the binding proteins of CRIP1. The mouse xenograft model was used to determine the role of CRIP1 in the proliferation and drug-resistance of MM cells.

FINDINGS

High CRIP1 expression was associated with unfavorable clinical outcomes in patients with MM and served as a biomarker for RRMM with shorter overall survival. In vitro and in vivo studies showed that CRIP1 plays a critical role in protein homeostasis via the dual regulation of the activities of proteasome and autophagy in MM cells. A combined analysis of RNA-seq, Co-IP and TAP/MS demonstrated that CRIP1 promotes proteasome inhibitors resistance in MM cells by simultaneously binding to de-ubiquitinase USP7 and proteasome coactivator PA200. CRIP1 promoted proteasome activity and autophagosome maturation by facilitating the dequbiquitination and stabilization of PA200.

INTERPRETATION

Our findings clarified the pivotal roles of the CRIP1/USP7/PA200 complex in ubiquitin-dependent proteasome degradation and autophagy maturation involved in the pathogenesis of MM.

FUNDING

A full list of funding sources can be found in the acknowledgements section.

MALAT1 regulates network of microRNA-15a/16-VEGFA to promote tumorigenesis and angiogenesis in multiple myeloma

MALAT1 is one of the most hopeful members implicated in angiogenesis in a variety of non-malignant diseases. In multiple myeloma (MM), MALAT1 is recognized as the most highly expressed long non-coding RNA. However, the functional roles of MALAT1 in angiogenesis and the responsible mechanisms have not yet been explored. Herein, we discovered a novel regulatory network dependent on MALAT1 in relation to MM tumorigenesis and angiogenesis. We observed that MALAT1 was upregulated in MM and significantly associated with poor overall survival. MALAT1 knockdown suppressed MM cell proliferation and promoted apoptosis, while restricting endothelial cells angiogenesis. Moreover, MALAT1 directly targeted microRNA-15a/16, and microRNA-15a/16 suppression partly reverted the effects of MALAT1 deletion on MM cells in vitro as well as tumor growth and angiogenesis in vivo. In addition, further study indicated that MALAT1 functioned as a competing endogenous RNA for microRNA-15a/16 to regulate vascular endothelial growth factor A (VEGFA) expression. Our results suggest that MALAT1 plays an important role in the regulatory axis of microRNA-15a/16-VEGFA to promote tumorigenicity and angiogenesis in MM. Consequently, MALAT1 could serve as a novel promising biomarker and a potential antiangiogenic target against MM.

Advances in research on potential inhibitors of multiple myeloma

Multiple myeloma (MM) is a common hematological malignancy. Although recent clinical applications of immunomodulatory drugs, proteasome inhibitors and CD38-targeting antibodies have significantly improved the outcome of MM patient with increased survival, the incidence of drug resistance and severe treatment-related complications is gradually on the rise. This review article summarizes the characteristics and clinical investigations of several MM drugs in clinical trials, including their structures, mechanisms of action, structure-activity relationships, and clinical study progress. Furthermore, the application potentials of the drugs that have not yet entered clinical trials are also reviewed. The review also outlines the future directions of MM drug development.

Exosome miRNAs profiling in serum and prognostic evaluation in patients with multiple myeloma

MicroRNAs (MiRNAs) carried by exosomes play pivotal roles in the crosstalk between cell components in the tumor microenvironment. Our study aimed at identifying the expression profile of exosomal miRNAs (exo-miRNAs) in the serum of multiple myeloma (MM) patients and investigating the regulation networks and their potential functions by integrated bioinformatics analysis. Exosomes in serum from 19 newly diagnosed MM patients and 9 healthy donors were isolated and the miRNA profile was investigated by small RNA sequencing. Differential expression of exo-miRNAs was calculated and target genes of miRNAs were predicted. CytoHubba was applied to identify the hub miRNAs and core target genes. The LASSO Cox regression model was used to develop the prognostic model, and the ESTIMATE immune score was calculated to investigate the correlation between the model and immune status in MM patients. The top six hub differentially expressed serum exo-miRNAs were identified. 513 target genes of the six hub exo-miRNAs were confirmed to be differentially expressed in MM cells in the Zhan Myeloma microarray dataset. Functional enrichment analysis indicated that these target genes were mainly involved in mRNA splicing, cellular response to stress, and deubiquitination. 13 core exo-miRNA target genes were applied to create a novel prognostic signature to provide risk stratification for MM patients, which is associated with the immune microenvironment of MM patients. Our study comprehensively investigated the exo-miRNA profiles in MM patients. A novel prognostic signature was constructed to facilitate the risk stratification of MM patients with distinct outcomes.

Study on the Effect of EZH2 Inhibitor Combined with TIGIT Monoclonal Antibody against Multiple Myeloma Cells

EZH2, a member of the polycomb repressive complex 2, induces trimethylation of the downstream gene at the histone three lysine 27 (H3K27me3) position to inhibit tumor cell proliferation. Here, we showed that the apoptosis rate and apoptotic protein expression increased after EZH2 inhibition, whereas key molecules of the NF-κB signaling pathway and the downstream target genes were inhibited. Additionally, the expression of CD155, a TIGIT high-affinity ligand in multiple myeloma (MM) cells, was decreased by the mTOR signaling pathway. Furthermore, the combination of EZH2 inhibitor and TIGIT monoclonal antibody blockade enhanced the anti-tumor effect of natural killer cells. In summary, the EZH2 inhibitor not only plays an anti-tumor role as an epigenetic drug, but also enhances the anti-tumor effect of the TIGIT monoclonal antibody by affecting the TIGIT-CD155 axis between NK cells and MM cells, thus providing new ideas and theoretical basis for the treatment of MM patients.

Polycomb-like Proteins in Gene Regulation and Cancer

Polycomb-like proteins (PCLs) are a crucial group of proteins associated with the Polycomb repressive complex 2 (PRC2) and are responsible for setting up the PRC2.1 subcomplex. In the vertebrate system, three homologous PCLs exist: PHF1 (PCL1), MTF2 (PCL2), and PHF19 (PCL3). Although the PCLs share a similar domain composition, they differ significantly in their primary sequence. PCLs play a critical role in targeting PRC2.1 to its genomic targets and regulating the functionality of PRC2. However, they also have PRC2-independent functions. In addition to their physiological roles, their dysregulation has been associated with various human cancers. In this review, we summarize the current understanding of the molecular mechanisms of the PCLs and how alterations in their functionality contribute to cancer development. We particularly highlight the nonoverlapping and partially opposing roles of the three PCLs in human cancer. Our review provides important insights into the biological significance of the PCLs and their potential as therapeutic targets for cancer treatment.

Epi-miRNAs: Modern mediators of methylation status in human cancers

Methylation of the fundamental macromolecules, DNA/RNA, and proteins, is remarkably abundant, evolutionarily conserved, and functionally significant in cellular homeostasis and normal tissue/organism development. Disrupted methylation imprinting is strongly linked to loss of the physiological equilibrium and numerous human pathologies, and most importantly to carcinogenesis, tumor heterogeneity, and cancer progression. Mounting recent evidence has documented the active implication of miRNAs in the orchestration of the multicomponent cellular methylation machineries and the deregulation of methylation profile in the epigenetic, epitranscriptomic, and epiproteomic levels during cancer onset and progression. The elucidation of such regulatory networks between the miRNome and the cellular methylation machineries has led to the emergence of a novel subclass of miRNAs, namely "epi-miRNAs" or "epi-miRs." Herein, we have summarized the existing knowledge on the functional role of epi-miRs in the methylation dynamic landscape of human cancers and their clinical utility in modern cancer diagnostics and tailored therapeutics. This article is categorized under: RNA in Disease and Development > RNA in Disease.

[Establishment and comparison of three human multiple myeloma cell line transplantation models in mice]

Objective: To establish three types of xenotransplantation models using human myeloma cell lines ARP1, MM.1S, and NCI-H929 and to compare the proliferation, tumor load, and biological characteristics of the three types of cells after transplantation. Methods: Suspensions of human myeloma cell lines ARP1, MM.1S, and NCI-H929 were implanted into NOD/SCID mice by subcutaneous injection or tail vein injection. The survival of the mice was observed weekly, and the tumor load was measured. Flow cytometry was used to detect the proportion of CD138(+) cells in tumor tissue or the mouse bone marrow. CD138(+) cells and light chains were detected by immunofluorescence. Light chains in bone marow and peipheral blood were measured by ELISA, and bone disease was assessed by micro-CT. Results: Mice injected with ARP1, MM.1S, and NCI-H929 cells all formed tumors subcutaneously in about 2 weeks. Immunofluorescence detection supported plasma cell tumors. Kappa light chains were detected in the peripheral blood of ARP1 mice on day 20 after tail vein transplantation (8.2±1.0 ng/ml) . After 6 weeks of tail vein transplantation, mice in the ARP1 group showed signs of weight loss, mental depression, and dragging legs, and human CD138(+)CD38(+) cells were detected in the bone marrow (BM) . Furthermore, bortezomib (BTZ) treatment given once the tumor was established significantly reduced the tumor burden[ (5.7±0.2) % vs (21.3±2.1) %, P<0.01]. Human CD138(+)CD38(+) cells were not detected in the BM of the MM.1S or NCI-H929 groups. Conclusion: The results of this study suggest that the mouse models constructed by the three cell lines (ARP1, MM.1S, and NCI-H929) can be used as models for the pathogenesis and clinical research of MM.

Indirubin-3'-monoxime acts as proteasome inhibitor: Therapeutic application in multiple myeloma

BACKGROUND

Multiple myeloma (MM) is still an incurable malignancy of plasma cells. Proteasome inhibitors (PIs) work as the backbone agent and have greatly improved the outcome in majority of newly diagnosed patients with myeloma. However, drug resistance remains the major obstacle causing treatment failure in clinical practice. Here, we investigated the effects of Indirubin-3'-monoxime (I3MO), one of the derivatives of Indirubin, in the treatment of MM.

METHODS

MM patient primary samples and human cell lines were examined. I3MO effects on myeloma treatment and the underling molecular mechanisms were investigated via in vivo and in vitro study.

FINDINGS

Our results demonstrated the anti-MM activity of I3MO in both drug- sensitive and -resistance MM cells. I3MO sensitizes MM cells to bortezomib-induced apoptosis. Mechanistically, I3MO acts as a multifaceted regulator of cell death, which induced DNA damage, cell cycle arrest, and abrogates NF-κB activation. I3MO efficiently down-regulated USP7 expression, promoted NEK2 degradation, and suppressed NF-κB signaling in MM. Our study reported that I3MO directly bound with and caused the down-regulation of PA28γ (PSME3), and PA200 (PSME4), the proteasome activators. Knockdown of PSME3 or PSME4 caused the inhibition of proteasome capacity and the overload of paraprotein, which sensitizes MM cells to bortezomib-mediated growth arrest. Clinical data demonstrated that PSME3 and PSME4 are over-expressed in relapsed/refractory MM (RRMM) and associated with inferior outcome.

INTERPRETATION

Altogether, our study indicates that I3MO is agent triggering proteasome inhibition and represents a promising therapeutic strategy to improve patient outcome in MM.

FUNDINGS

A full list of funding can be found in the acknowledgements.

Effect of Autologous Stem Cell Transplantation Combined with Modified VTD Regimen on Elderly Patients with Multiple Myeloma and Its Influence on miRNA Cytokines

OBJECTIVE

To explore the effect of autologous stem cell transplantation combined with modified VTD regimen on elderly patients with multiple myeloma and its influence on miRNA cytokines.

METHODS

The data of 42 elderly patients with multiple myeloma who were treated in our hospital from May 2010 to June 2018 were retrospectively analyzed, and they were divided into the combined group (autologous stem cell transplantation combined with improved VTD scheme, n = 25) and the control group (improved VTD scheme, n = 17) according to different treatment schemes, and the clinical efficacy of the two groups was compared. The levels of CD3+, CD4+, CD4+/CD8+, and Treg were measured in the two groups. The expression levels of miRNA-15a, miRNA-16, and miRNA-21 in the bone marrow fluid of the two groups were measured before and after treatment. The levels of M protein and myeloma cells in the two groups were detected. Comparing the incidence of adverse reactions between the two groups, the Kaplan-Meier method was used for survival analysis.

RESULTS

The total effective rate of the combined group (84.00%) was higher than that of the control group (52.94%), and the difference was statistically significant (P < 0.05). After treatment, the levels of CD3+, CD4+, CD4+/CD8+, Treg, miRNA-15a, and miRNA-16 in the combined group were higher than those in the control group, and the levels of miRNA-21, M protein, and myeloma cells were lower than those in the control group, with statistical significance (P < 0.05). There was no significant difference in adverse reactions between the two groups (P > 0.05). The first, second, and third year survival rates of group A (96.00%, 88.00%, and 80.00%) were significantly higher than those of the control group (70.59%, 58.82%, and 47.06%), and the difference was statistically significant (P < 0.05).

CONCLUSION

Autologous stem cell transplantation combined with a modified VTD regimen can effectively improve the immune function and survival rate of elderly patients with multiple myeloma, which is safe and effective.

Bone Marrow Stroma-Induced Transcriptome and Regulome Signatures of Multiple Myeloma

Multiple myeloma (MM) is a hematological cancer with inevitable drug resistance. MM cells interacting with bone marrow stromal cells (BMSCs) undergo substantial changes in the transcriptome and develop de novo multi-drug resistance. As a critical component in transcriptional regulation, how the chromatin landscape is transformed in MM cells exposed to BMSCs and contributes to the transcriptional response to BMSCs remains elusive. We profiled the transcriptome and regulome for MM cells using a transwell coculture system with BMSCs. The transcriptome and regulome of MM cells from the upper transwell resembled MM cells that coexisted with BMSCs from the lower chamber but were distinctive to monoculture. BMSC-induced genes were enriched in the JAK2/STAT3 signaling pathway, unfolded protein stress, signatures of early plasma cells, and response to proteasome inhibitors. Genes with increasing accessibility at multiple regulatory sites were preferentially induced by BMSCs; these genes were enriched in functions linked to responses to drugs and unfavorable clinic outcomes. We proposed JUNB and ATF4::CEBPβ as candidate transcription factors (TFs) that modulate the BMSC-induced transformation of the regulome linked to the transcriptional response. Together, we characterized the BMSC-induced transcriptome and regulome signatures of MM cells to facilitate research on epigenetic mechanisms of BMSC-induced multi-drug resistance in MM.

Mechanisms of Polycomb group protein function in cancer

Cancer arises from a multitude of disorders resulting in loss of differentiation and a stem cell-like phenotype characterized by uncontrolled growth. Polycomb Group (PcG) proteins are members of multiprotein complexes that are highly conserved throughout evolution. Historically, they have been described as essential for maintaining epigenetic cellular memory by locking homeotic genes in a transcriptionally repressed state. What was initially thought to be a function restricted to a few target genes, subsequently turned out to be of much broader relevance, since the main role of PcG complexes is to ensure a dynamically choregraphed spatio-temporal regulation of their numerous target genes during development. Their ability to modify chromatin landscapes and refine the expression of master genes controlling major switches in cellular decisions under physiological conditions is often misregulated in tumors. Surprisingly, their functional implication in the initiation and progression of cancer may be either dependent on Polycomb complexes, or specific for a subunit that acts independently of other PcG members. In this review, we describe how misregulated Polycomb proteins play a pleiotropic role in cancer by altering a broad spectrum of biological processes such as the proliferation-differentiation balance, metabolism and the immune response, all of which are crucial in tumor progression. We also illustrate how interfering with PcG functions can provide a powerful strategy to counter tumor progression.

Insights into high-risk multiple myeloma from an analysis of the role of PHF19 in cancer

Despite  improvements in outcome, 15-25% of newly diagnosed multiple myeloma (MM) patients have treatment resistant high-risk (HR) disease with a poor survival. The lack of a genetic basis for HR has focused attention on the role played by epigenetic changes. Aberrant expression and somatic mutations affecting genes involved in the regulation of tri-methylation of the lysine (K) 27 on histone 3 H3 (H3K27me3) are common in cancer. H3K27me3 is catalyzed by EZH2, the catalytic subunit of the Polycomb Repressive Complex 2 (PRC2). The deregulation of H3K27me3 has been shown to be involved in oncogenic transformation and tumor progression in a variety of hematological malignancies including MM. Recently we have shown that aberrant overexpression of the PRC2 subunit PHD Finger Protein 19 (PHF19) is the most significant overall contributor to HR status further focusing attention on the role played by epigenetic change in MM. By modulating both the PRC2/EZH2 catalytic activity and recruitment, PHF19 regulates the expression of key genes involved in cell growth and differentiation. Here we review the expression, regulation and function of PHF19 both in normal and the pathological contexts of solid cancers and MM. We present evidence that strongly implicates PHF19 in the regulation of genes important in cell cycle and the genetic stability of MM cells making it highly relevant to HR MM behavior. A detailed understanding of the normal and pathological functions of PHF19 will allow us to design therapeutic strategies able to target aggressive subsets of MM.

One Omics Approach Does Not Rule Them All: The Metabolome and the Epigenome Join Forces in Haematological Malignancies

Aberrant DNA methylation, dysregulation of chromatin-modifying enzymes, and microRNAs (miRNAs) play a crucial role in haematological malignancies. These epimutations, with an impact on chromatin accessibility and transcriptional output, are often associated with genomic instability and the emergence of drug resistance, disease progression, and poor survival. In order to exert their functions, epigenetic enzymes utilize cellular metabolites as co-factors and are highly dependent on their availability. By affecting the expression of metabolic enzymes, epigenetic modifiers may aid the generation of metabolite signatures that could be utilized as targets and biomarkers in cancer. This interdependency remains often neglected and poorly represented in studies, despite well-established methods to study the cellular metabolome. This review critically summarizes the current knowledge in the field to provide an integral picture of the interplay between epigenomic alterations and the cellular metabolome in haematological malignancies. Our recent findings defining a distinct metabolic signature upon response to enhancer of zeste homolog 2 (EZH2) inhibition in multiple myeloma (MM) highlight how a shift of preferred metabolic pathways may potentiate novel treatments. The suggested link between the epigenome and the metabolome in haematopoietic tumours holds promise for the use of metabolic signatures as possible biomarkers of response to treatment.

PHD finger protein 19 expression in multiple myeloma: Association with clinical features, induction therapy outcome, disease progression, and survival

Background

PHD finger protein 19 (PHF19), also known as polycomb‐like protein 3 (PCL3), promotes the progression of multiple myeloma (MM) and drug resistance; however, its role in the management of MM remains unclear. Therefore, we aimed to elucidate the correlation between PHF19 expression and treatment response, disease progression, and survival of patients with MM.

Methods

Plasma cells derived from the bone marrow of 101 patients with de novo MM were collected prior to induction therapy, as were plasma cells derived from the bone marrow of 30 healthy donors. PHF19 expression in plasma cells was analyzed using quantitative reverse transcription polymerase chain reaction. Furthermore, the response to induction therapy, progression‐free survival (PFS), and overall survival (OS) were assessed.

Results

PHF19 expression tends to be upregulated more often in MM patients than in healthy donors (p < 0.001) and can accurately predict MM risk (area under curve [AUC], 0.916; 95% confidence interval [CI], 0.869–0.962). Furthermore, elevated PHF19 expression was correlated with higher International Staging System (ISS) (p = 0.036) and revised ISS stages (p = 0.035). In addition, MM patients who achieved complete response (CR) exhibited reduced PHF19 compared to those who did not (p = 0.028). Moreover, increased PHF19 expression was correlated with unfavorable PFS (p = 0.006) and OS (p = 0.027) rates. Furthermore, the results of multivariate Cox analysis also revealed that PHF19 high expression was independently associated with a reduced PFS rate (hazard ratio: 2.025, p = 0.028).

Conclusion

Increased PHF19 expression is correlated with poor induction therapy response and unfavorable long‐term prognosis of MM.

PHF19 inhibition as a therapeutic target in multiple myeloma

Epigenetic deregulation is increasingly recognized as a contributing pathological factor in multiple myeloma (MM). In particular tri-methylation of H3 lysine 27 (H3K27me3), which is catalyzed by PHD finger protein 19 (PHF19), a subunit of the Polycomb Repressive Complex 2 (PRC2), has recently shown to be a crucial mediator of MM tumorigenicity. Overexpression of PHF19 in MM has been associated with worse clinical outcome. Yet, while there is mounting evidence that PHF19 overexpression plays a crucial role in MM carcinogenesis downstream mechanisms remain to be elucidated. In the current study we use a functional knock down (KD) of PHF19 to investigate the biological role of PHF19 and show that PHF19KD leads to decreased tumor growth in vitro and in vivo. Expression of major cancer players such as bcl2, myc and EGR1 were decreased upon PHF19KD further underscoring the role of PHF19 in MM biology. Additionally, our results highlighted the prognostic impact of PHF19 overexpression, which was significantly associated with worse survival. Overall, our study underscores the premise that targeting the PHF19-PRC2 complex would open up avenues for novel MM therapies.

Potential Role of microRNAs in inducing Drug Resistance in Patients with Multiple Myeloma

The prognosis for newly diagnosed subjects with multiple myeloma (MM) has significantly progressed in recent years. However, most MM patients relapse and after several salvage therapies, the onset of multidrug resistance provokes the occurrence of a refractory disease. A continuous and bidirectional exchange of information takes place between the cells of the microenvironment and neoplastic cells to solicit the demands of cancer cells. Among the molecules serving as messengers, there are microRNAs (miRNA), a family of small noncoding RNAs that regulate gene expression. Numerous miRNAs are associated with drug resistance, also in MM, and the modulation of their expression or activity might be explored to reverse it. In this review we report the most recent studies concerning the relationship between miRNAs and chemoresistance to the most frequently used drugs, such as proteasome inhibitors, steroids, alkylating agents and immunomodulators. The experimental use of antagomirs or miRNA mimics have successfully been proven to counteract chemoresistance and display synergistic effects with antimyeloma drugs which could represent a fundamental moment to overcome resistance in MM treatment.

Multiple myeloma hinders erythropoiesis and causes anaemia owing to high levels of CCL3 in the bone marrow microenvironment

Anaemia is the most common complication of myeloma and is associated with worse clinical outcomes. Although marrow replacement with myeloma cells is widely considered a mechanistic rationale for anaemia, the exact process has not been fully understood. Our large cohort of 1363 myeloma patients had more than 50% of patients with moderate or severe anaemia at the time of diagnosis. Anaemia positively correlated with myeloma cell infiltration in the bone marrow (BM) and worse patient outcomes. The quantity and erythroid differentiation of HSPCs were affected by myeloma cell infiltration in the BM. The master regulators of erythropoiesis, GATA1 and KLF1, were obviously downregulated in myeloma HSPCs. However, the gene encoding the chemokine CCL3 showed significantly upregulated expression. Elevated CCL3 in the BM plasma of myeloma further inhibited the erythropoiesis of HSPCs via activation of CCL3/CCR1/p38 signalling and suppressed GATA1 expression. Treatment with a CCR1 antagonist effectively recovered GATA1 expression and rescued erythropoiesis in HSPCs. Myeloma cell infiltration causes elevated expression of CCL3 in BM, which suppresses the erythropoiesis of HSPCs and results in anaemia by downregulating the level of GATA1 in HSPCs. Thus, our study indicates that targeting CCL3 would be a potential strategy against anaemia and improve the survival of myeloma patients.

Role of Polycomb Complexes in Normal and Malignant Plasma Cells

Plasma cells (PC) are the main effectors of adaptive immunity, responsible for producing antibodies to defend the body against pathogens. They are the result of a complex highly regulated cell differentiation process, taking place in several anatomical locations and involving unique genetic events. Pathologically, PC can undergo tumorigenesis and cause a group of diseases known as plasma cell dyscrasias, including multiple myeloma (MM). MM is a severe disease with poor prognosis that is characterized by the accumulation of malignant PC within the bone marrow, as well as high clinical and molecular heterogeneity. MM patients frequently develop resistance to treatment, leading to relapse. Polycomb group (PcG) proteins are epigenetic regulators involved in cell fate and carcinogenesis. The emerging roles of PcG in PC differentiation and myelomagenesis position them as potential therapeutic targets in MM. Here, we focus on the roles of PcG proteins in normal and malignant plasma cells, as well as their therapeutic implications.