Promotes Multiple Myeloma Cell Research Articles

PDCD4 interacting with PIK3CB and CTSZ promotes the apoptosis of multiple myeloma cells.

The role of programmed cell death 4 (PDCD4) in multiple myeloma (MM) development remains unknown. Here, we investigated its role and action mechanism in MM. Bioinformatic analysis indicated that patients with MM and high PDCD4 expression had higher overall survival than those with low PDCD4 expression. PDCD4 expression promoted MM cell apoptosis and inhibited their viability invitro and tumor growth invivo. RNA-binding protein immunoprecipitation sequencing analysis showed that PDCD4 is bound to the 5' UTR of the apoptosis-related genes PIK3CB, Cathepsin Z (CTSZ), and X-chromosome-linked apoptosis inhibitor (XIAP). PDCD4 knockdown reduced the cell apoptosis rate, which was rescued by adding PIK3CB, CTSZ, or XIAP inhibitors. Dual luciferase reporter assays confirmed the internal ribosome entry site (IRES) activity of the 5' UTRs of PIK3CB and CTSZ. An RNA pull-down assay confirmed binding of the 5' UTR of PIK3CB and CTSZ to PDCD4, identifying the specific binding fragments. PDCD4 is expected to promote MM cell apoptosis by binding to the IRES domain in the 5' UTR of PIK3CB and CTSZ and inhibiting their translation. Our findings suggest that PDCD4 plays an important role in MM development by regulating the expression of PIK3CB, CTSZ, and XIAP, and highlight new potential molecular targets for MM treatment.

Activated platelet-derived exosomal LRG1 promotes multiple myeloma cell growth

The hypercoagulable state is a hallmark for patients with multiple myeloma (MM) and is associated with disease progression. Activated platelets secrete exosomes and promote solid tumor growth. However, the role of platelet-derived exosomes in MM is not fully clear. We aim to study the underlying mechanism of how platelet-derived exosomes promote MM cell growth. Flow cytometry, Western blot, proteome analysis, co-immunoprecipitation, immunofluorescence staining, and NOD/SCID mouse subcutaneous transplantation model were performed to investigate the role of exosomal LRG1 on multiple myeloma cell growth. Peripheral blood platelets in MM patients were in a highly activated state, and platelet-rich plasma from MM patients significantly promoted cell proliferation and decreased apoptotic cells in U266 and RPMI8226 cells. Leucine-rich-alpha-2-glycoprotein 1 (LRG1) was significantly enriched in MM platelet-derived exosomes. Blocking LRG1 in recipient cells using LRG1 antibody could significantly eliminate the proliferation-promoting effect of platelet-derived exosomes on MM cells. And high exosomal LRG1 was associated with poor prognosis of patients with MM. Mechanistic studies revealed that LRG1 interacted with Olfactomedin 4 (OLFM4) to accelerate MM progression by activating the epithelial-to-mesenchymal transition (EMT) signaling pathway and promoting angiogenesis. Our results revealed that blocking LRG1 is a promising therapeutic strategy for the treatment of MM.

Mechanism and Clinical Significance of NAMPT in Multiple Myeloma

To investigate the mechanism and clinical value of nicotinamide phosphoribosyltransferase (NAMPT) in multiple myeloma (MM). RT-qPCR and Western blot were used to detect the expression of NAMPT in MM cells and normal bone marrow mononuclear cells. The biological function of NAMPT was analyzed by cell proliferation and apoptosis assay, small interfering RNA silencing, overexpression assay and chromatin immunoprecipitation assay. The mRNA and protein expression levels of NAMPT in MM cell lines (MM1R, MM1S, U266 and RPMI-8226) were significantly higher than those in normal bone marrow mononuclear cells (P < 0.001), and were most obvious in U266 cells. Compared with Si-NC group, the proliferation of U266 cells in Si-NAMPT group was significantly inhibited at 24, 48 and 72 h after transfection (P =0.006, P < 0.001, P =0.001), and the apoptosis rate of U266 cells was significantly increased at 48 h after transfection (P < 0.001). Compared with Flag-NC group, U266 cell proliferation in Flag-NAMPT group was significantly increased (P =0.003, P =0.002, P < 0.001), while the apoptosis rate decreased significantly at 48 h after transfection. The expression of NAMPT in U266 cells was regulated by XBP1 at transcriptional level. The proliferation rate of U266 cells with XBP1 or NAMPT stable knockout or MKC3946 pretreated with bortezomib was significantly decreased, the levels of BCL-2 mRNA and protein were also significantly decreased, while the levels of BAX mRNA and protein were significantly increased, moreover, the cleavage degree of caspase-3 significantly decreased, while caspase-3/7 activity increased dramatically (P < 0.05). The high expression of NAMPT in MM cell line can promote MM cell proliferation and inhibit apoptosis. NAMPT is regulated by IRE1α-XBP1 signaling pathway in U266 cells. Stable knockdown of NAMPT or blocking of IRE1α-XBP1 pathway can significantly increase the sensitivity of U266 cells to bortezomib.

A Functional Genomic Screen to Identify Novel Genes Involved in Multiple Myeloma Tumour Development

Multiple myeloma (MM) is an incurable malignancy characterised by uncontrolled proliferation of plasma cells (PCs) in the bone marrow (BM). MM is a genetically heterogeneous disease with each patient's PCs harbouring unique genetic mutations, however the development of MM tumours is not only dependent on the underlying genetics but also on the selective pressures applied by the BM microenvironment. Hence, we hypothesise that identifying the dependencies which promote MM cell outgrowth in the BM microenvironment will allow for the identification of new drug targets. This project aims to use an in vivo functional screen, combining CRISPR-Cas9 gene editing, using a single guide RNA (sgRNA) library targeting thousands of genes, with a murine model of MM, to identify novel genes involved in MM tumour development. The Bassik human apoptosis and cancer CRISPR knockout library (Addgene #101926) was used to transduce MM cells with 31,324 unique sgRNAs targeting 3,015 genes and 1,500 control regions. The human MM cell line OPM2 was transduced with the Cas9 transgene (FuCas9GFP), followed by the sgRNA expression vector (pMCB320) generating OPM2-Cas9-sgRNA cells. These cells were then injected (5x10 5 cells/mouse, n=8 mice + 1 tumour-naive control) into the tibiae of immunodeficient NOD.Cg-Prkdc scid Il2rg tm1Wjl/SzJ (NSG) mice. Four weeks post-injection, the primary tumour within the injected tibia was isolated and sgRNA frequencies were assessed via next generation sequencing and compared with that of the initial library and the injected cells using the MAGeCK algorithm. To identify genes that play roles in MM tumour formation in patients, we assessed the expression of our identified genes in CD138-selected BM PCs from newly diagnosed MM patients (n=155) when compared with normal PCs from healthy donors (n=5) in microarray dataset E-MTAB-363 (ArrayExpress). Furthermore, to identify potential pathway involvement of our identified genes we performed gene set enrichment analysis (GSEA) using the University of California San Diego and Broad Institute developed GSEA software, comparing to Hallmark Gene Sets. Comparison of the in vitro cultured cells with the initial library identified 34 genes with undetectable (p&amp;lt;0.05) sgRNAs post in vitro culture, suggesting these genes play key roles in the survival of OPM2 cells. This list contained a number of genes known to control MM cell survival, such as IRF4 and CCND2. Additionally, sgRNAs targeting a further 115 genes were significantly depleted (p&amp;lt;0.05) in vitro and were completely undetectable in vivo, suggesting that these are implicated in cell proliferation and tumour formation in vivo. This gene list contained some already known MM drivers such as MYC, KRAS and DIS3. Furthermore, we identified 28 genes where CRISPR knockout had no significant effect in vitro but were critical dependencies for tumour development, with sgRNAs being undetectable (p&amp;lt;0.05) in vivo. This list contained genes known to be important for MM and BM stromal cell interaction such as ALCAM and SPP1. Notably, 25% of the genes identified as critical dependencies for OPM2 cells in vitro and/or in vivo are significantly upregulated &amp;gt;2-fold (p&amp;lt;0.05; limma) in MM patient PCs when compared with normal PCs (E-MTAB-363), suggesting these may play a role in tumour development in patients. Gene set enrichment analysis revealed that the genes that were essential in vitro were predominantly involved in cell survival related pathways such as cell cycle regulation (G2M checkpoint) and DNA replication/repair; however, the uniquely in vivo genes are predominantly involved in cell metabolism pathways such as MTORC1 signalling, oxidative phosphorylation and glycolysis. Overall, this study has successfully used a functional genetic screen to identify novel gene dependencies required for in vitro MM cell growth and in vivo MM tumour development. A secondary genetic screen will be performed in vivo to validate and refine this list of candidate genes. These validated genes will be further investigated using patient derived data sets to determine if they represent common vulnerabilities in patients and in multiple MM cell lines to investigate their specific mechanistic and pathway involvement. Identification and understanding the driving dependencies which promote MM cell outgrowth in the BM microenvironment will allow for the identification and development of new drug targets to improve patient outcomes.

Exosomal lncRNA NEAT1 Inhibits NK-Cell Activity to Promote Multiple Myeloma Cell Immune Escape via an EZH2/PBX1 Axis.

This study reveals that exosomal NEAT1 regulates EZH2/PBX1 axis to inhibit NK-cell activity, thereby promoting multiple myeloma cell immune escape, which offers a novel therapeutic potential for multiple myeloma.

Identification of evolutionary mechanisms of myelomatous effusion by single-cell RNA sequencing

AbstractMyelomatous effusion (ME) is a rare manifestation of extramedullary multiple myeloma (MM) with limited therapeutic options and poor outcomes. The molecular mechanisms underlying ME are incompletely understood. We profiled transcriptomes of bone marrow, peripheral blood (PB), and pleural effusion/ascites from 3 patients with ME using single-cell RNA sequencing analysis. We found that ME contained a higher percentage of cytotoxic T cells, whereas PB contained a higher proportion of naive T cells. Malignant cells varied within and between sites and patients in their expression of signatures. We identified a gene module highly expressed in intramedullary and extramedullary plasma cell clusters and defined cell clusters expressing this gene set as extramedullary-initiating cells (EMICs). This gene set was associated with increased cellular proliferation, involved in p53 signaling, and related to poor prognosis in MM. The transcriptional regulators E2F1, YY1, and SMAD1 were activated in EMICs. Leukocyte immunoglobulin–like receptor subfamily B4 (LILRB4) was upregulated in extramedullary EMICs. We confirmed that LILRB4 promoted MM cell migration in vitro. This study provided insight into the evolutionary mechanisms of ME and defined EMICs and LILRB4 associated with extramedullary development.

CRIP1 INDUCES PIS RESISTANCE BY FORMING A COMPLEX WITH USP7 /PA200 AND ENHANCING PROTEASOME ACTIVITY AND AUTOPHAGY IN MULTIPLE MYELOMA

Introduction: Multiple myeloma (MM) is a plasma malignancy characterized by an accumulation of misfolded immunoglobulins in the cell. Although proteasome inhibitor (PI) can treat MM by inhibiting ubiquitin-proteasome system (UPS), autophagy as a compensatory protein clearance mechanism, it still leads to drug resistance. The discovery of new targets that can simultaneously inhibit UPS and autophagy will provide great potential for the treatment of MM. Methods: The proliferation, invasion, migration, proteasome activity and autophagy were detected in CRIP1- knockdown /overexpression and control MM cells. Co-IP (Co-Immunoprecipitation) with TAP/MS (Tandem affinity purification/Mass spectrum) was performed to detect the binding of USP7, CRIP1 and PA200. Myeloma xenograft model was used to determine the role of CRIP1 to promote proliferation of MM cells and induce BTZ resistance in vivo. Results: The levels of CRIP1 were significantly increased in plasma cells from NDMM (newly diagnosed multiple myeloma) compared to healthy donors, and further increased in patients with RRMM (relapsed/refractory multiple myeloma). Moreover, the high expression of CRIP1 is significantly related to the poor prognosis of MM patients, especially those treated with BTZ. Our results in vitro and in vivo showed that CRIP1 knockdown noteworthy inhibited the cell growth, invasion, migration. MM cells were more sensitive to PIs-induced cell growth arrest when CRIP1 knockdown. The proteasome activity and the protein level of LC3B-Ⅱ of the MM cells were significantly reduced with CRIP1 knockdown. Co-IP analysis showed that CRIP1 formed a complex with USP7/PA200. The protein level of CRIP1 decreased and the ubiquitination CRIP1 increased with USP7 inhibition. These data suggested that CRIP1 is the substrate of USP7.CRIP1 promotes the de-ubiquitination and stabilization of PA200 mediated by USP7 by interacting with USP7 and PA200, which in turn promotes MM cell survival and drug resistant. Functional inhibition of CRIP1 by knocking down of USP7 or PSME4 in CRIP1 OE MM cell line led to a decrease of the activity of proteasome and autophagy, thus enhancing the sensitivity to PIs in intro and in vivo. Conclusion: CRIP1 plays a critical role in MM progression and PIs resistance by formation of CRIP1/USP7/PA200 complex. High level of CRIP1 is a biomarker for high-risk MM patients. CRIP1 is a potential target for MM therapy, can simultaneously inhibit proteasome activity and autophagy. Encore Abstract - previously submitted to EHA 2023 The research was funded by the following foundations:(a) CAMS Innovation Fund for Medical Sciences (CIFMS) (2021-I2M-1-040 and 2022-I2M-1-022), (b) National NaturalScience Foundation of China (82170194, 81920108006, 82270175) and Natural Science Foundation of Fujian Province of China (2021J02040). Keywords: Diagnostic and Prognostic Biomarkers, Multiple Myeloma, Tumor Biology and Heterogeneity No conflicts of interests pertinent to the abstract.

A novel 2-iminobenzimidazole compound, XYA1353, displays in vitro and in vivo anti-myeloma activity via targeting NF-κB signaling.

Multiple myeloma (MM) is an accumulated disease of malignant plasma cells, which is still incurably owing to therapeutic resistance and disease relapse. Herein, we synthesized a novel 2-iminobenzimidazole compound, XYA1353, showing a potent anti-myeloma activity both in vitro and in vivo. Compound XYA1353 dose-dependently promoted MM cell apoptosis via activating caspase-dependent endogenous pathways. Moreover, compound XYA1353 could enhance bortezomib (BTZ)-mediated DNA damage via elevating γH2AX expression levels. Notably, compound XYA1353 interacted synergistically with BTZ and overcame drug resistance. RNA sequencing analysis and experiments confirmed that compound XYA1353 inhibited primary tumor growth and myeloma distal infiltration by disturbing canonical NF-κB signaling pathway via decreasing expression of P65/P50 and p-IκBα phosphorylation level. Due to its importance in regulating MM progression, compound XYA1353 alone or combined with BTZ may potentially exert therapeutic effects on multiple myeloma by suppressing canonical NF-κB signaling.

N6-methyladenosine reader YTHDF2 promotes multiple myeloma cell proliferation through EGR1/p21cip1/waf1/CDK2-Cyclin E1 axis-mediated cell cycle transition

Multiple myeloma (MM) is the second most common hematological malignancy. N6-methyladenosine (m6A) is the most abundant RNA modification. YTH domain-containing family protein 2 (YTHDF2) recognizes m6A-cotaining RNAs and accelerates degradation to regulate cancer progression. However, the role of YTHDF2 in MM remains unclear. We investigated the expression levels and prognostic role of YTHDF2 in MM, and studied the effect of YTHDF2 on MM proliferation and cell cycle. The results showed that YTHDF2 was highly expressed in MM and was an independent prognostic factor for MM survival. Silencing YTHDF2 suppressed cell proliferation and caused the G1/S phase cell cycle arrest. RNA immunoprecipitation (RIP) and m6A-RIP (MeRIP) revealed that YTHDF2 accelerated EGR1 mRNA degradation in an m6A-dependent manner. Moreover, overexpression of YTHDF2 promoted MM growth via the m6A-dependent degradation of EGR1 both in vitro and in vivo. Furthermore, EGR1 suppressed cell proliferation and retarded cell cycle by activating p21cip1/waf1 transcription and inhibiting CDK2-cyclinE1. EGR1 knockdown could reverse the inhibited proliferation and cell cycle arrest upon YTHDF2 knockdown. In conclusion, the high expression of YTHDF2 promoted MM cell proliferation via EGR1/p21cip1/waf1/CDK2-cyclin E1 axis-mediated cell cycle transition, highlighting the potential of YTHDF2 as an effective prognostic biomarker and a promising therapeutic target for MM.

CD229 interacts with RASAL3 to activate RAS/ERK pathway in multiple myeloma proliferation.

Multiple myeloma (MM) is an incurable plasma cell malignancy, while CAR-T therapy offers a new direction for the treatment of MM. Recently, signaling lymphocytic activation molecule family 3 (CD229), a cell surface immune receptor belonging to the signaling lymphocyte activating molecule family (SLAMF), is emerging as a CAR-T therapeutic target in MM. However, a clear role of CD229 in MM remains elusive. In this study, MM patients with elevated CD229 expression achieved poor prognosis by analyzing MM clinical databases. In addition, CD229 promoted MM cell proliferation in vitro as well as in xenograft mouse model in vivo. Mechanism study revealed that CD229 promoted MM cell proliferation by regulating the RAS/ERK signaling pathway. Further exploration employed co-immunoprecipitation coupled with mass spectrometry to identify RASAL3 as an important downstream protein of CD229. Additionally, we developed a co-culture method combined with the immunofluorescence assay to confirm that intercellular tyrosine phosphorylation mediated self-activation of CD229 to activate RAS/ERK signaling pathway via interacting with RASAL3. Taken together, these findings not only demonstrate the oncogenic role of CD229 in MM cell proliferation, but also illustrate the potential of CD229 as a promising therapeutic target for MM treatment.

Bioprocessing of MIR17HG Results in Long and Short Noncoding RNAs with Targetable Tumor-Promoting Activity in Multiple Myeloma

Our recent studies demonstrated that multiple myeloma (MM) cells can become significantly addicted to and in turn therapeutically susceptible to the modulation of oncogenic noncoding RNAs (ncRNAs). Through large-scale CRISPR interference (CRISPRi) and CRISPR-Cas13d viability screens, we identified MIR17HG as a leading cell growth-dependency in 6 MM cell lines. MIR17HG is mainly known for producing the miRNA cluster miR-17-92, which includes six mature oncogenic miRNAs (-17, -18a, -19a, -20a, -19b, -92a). However, we observed that depleting MIR17HG pre-RNA with sgRNAs or antisense oligonucleotides (ASO) took >3 days to downregulate the miR-17-92 members, yet appreciable transcriptional changes were immediately produced followed by cell cycle arrest in G0-G1 in 10 MM cell lines and CD138+ cells from 13 MM patients. Moreover, antagonism of miR-17-92 using anti-miRs did not phenocopy the anti-MM activity of targeting the MIR17HG pre-RNA, and this activity was only partially rescued by ectopic expression of miR-17-92 mimics. Therefore, we reasoned that alternative transcripts generated at this locus could provide cell growth dependency. We analyzed our RNA-seq dataset of CD138+ cells from >300 MM patients and 70 MM cell lines for these transcripts and observed reads from regions of MIR17HG that are not included in miR-17-92. Using qRT-PCR and single molecule RNA FISH, we identified the expression of a nuclear-enriched, ~5k-nt long, polyA(+) lncRNA. This lncRNA, named lnc-17-92 was quickly downregulated within a few hours of exposure to ASOs targeting the MIR17HG pre-RNA. Using DROSHA-knockout MM cells, in which MIR17HG produces lnc-17-92 but not miR-17-92, we found that targeting the MIR17HG pre-RNA effectively antagonized MM cell growth. Using easy-to-manipulate cellular models (e.g., HCT-116), we observed stronger rescue by ectopic expression of lnc-17-92, as compared to miR-17-92, after targeting MIR17HG pre-RNA. Using RNA-protein pull down (RPPD) and RNA yeast-3-hybrid (Y3H) assays, we found that the transcription factor c-MYC and the epigenetic modulator WDR82 were binding partners for lnc-17-92. In fact, we found that lnc-17-92 mediated their protein-protein interaction by providing the chromatin scaffold for the assembly of a MYC-WDR82 complex at the promoter region of ACC1. This gene encodes the limiting enzyme for de novo lipogenesis, a metabolic pathway that we show is controlled by lnc-17-92 to promote MM cell growth. Using three different cellular models (P493-6, HMECMYC, and U226MYC), we found that targeting MIR17HG pre-RNA preferentially killed MYC+ cells. This could be explained both by lnc-17-92 acting as a chromatin scaffold for MYC and also the known role of miR-17-92 in fine-tuning the downstream transcriptional program of MYC. However, we also observed that lnc-17-92 protected MYC from proteasomal degradation and found that the miR-17-92 member miR-92a negatively regulated MYC protein expression via an, as yet, unknown mechanism. The concerted action of lnc-17-92 and miR-17-92 on MYC protein stability is under investigation and updates will also be presented. Finally, we explored MIR17HG as a therapeutic target, which includes targeting both its lncRNA and miRNAs. To develop clinically applicable inhibitors, we screened >80 fully phosphorothioated (PS), 2'-O-methoxyethyl (2'-MOE)-modified, lipid-conjugated ASOs that could either trigger RNase H-mediated degradation of MIR17HG pre-RNA (gapmeRs) or exert function via an RNase H-independent mechanism (blockmeRs). We identified an 18-mer tocopherol (T)-conjugated gapmeR G2-15b-T ("G") and an 18-mer tocopherol (T)-conjugated steric blocker SB9-19-T ("B"). We found they had potent anti-tumor effects both in vitro and in vivo in three pre-clinical animal models, including a clinically relevant PDX-NSG mouse model. Tumor growth inhibition ranged from 100% (regression) to 50% in these models. Inhibitors did not cause overt toxicity in the mice, as shown by blood cell count, clinical, and body weight analysis. These inhibitors are currently being developed for translation to clinical trials. Altogether, our studies characterize a novel oncogenic mechanism for MIR17HG and provide clinically applicable inhibitors.

Long Noncoding RNA LINC01410 Interacts with the Minichromosome Maintenance (MCM) Complex to Promote Tumor Cell Growth in Multiple Myeloma

The human genome contains thousands of loci that produce long non-protein coding RNAs (lncRNAs) that play critical roles in healthy cell function as well as tumorigenesis. We have recently described the lncRNA landscape in newly diagnosed multiple myeloma (MM), identified their role as independent risk predictors for clinical outcome, and validated the functional contribution of specific lncRNAs to MM cell growth and viability. Although these examples suggest the significance of lncRNAs in MM pathobiology, the vast majority of lncRNA genes have not been functionally tested. To identify lncRNAs that promote MM cell growth, we performed a large-scale cell viability screen of lncRNAs using CRISPR interference (CRISPRi) to inhibit gene expression. To find lncRNA targets, we first interrogated our large RNA-seq dataset from 360 newly diagnosed MM patients and identified 913 lncRNA transcripts expressed in primary MM cells. We designed the CRISPRi library to target the transcription start site of these 913 lncRNA genes, each with 7 sgRNAs. We screened 3 MM cell lines (H929, KMS12BM, KMS11) and identified 32 lncRNA loci that modified cell growth upon CRISPRi targeting, with 7 lncRNAs impacting all three cell lines tested. We then evaluated the differential expression of these lncRNAs in primary MM cells compared to normal plasma cells (PC). We observed that LINC01410 was significantly overexpressed in MM patients compared to normal PC, especially in MM patients with t(4;14) translocations, and was an independent risk predictor that highly correlated with overall survival in newly diagnosed MM patients. We next knocked down LINC01410 using gapmeR antisense oligonucleotides (ASO) in a panel of MM cell lines and observed time-dependent inhibition of MM cell viability, including in the t(4;14) cell lines. As LINC01410 appears to localize to both the cytosol and nucleus, we also utilized siRNAs to specifically target the cytosolic isoform and observed a robust reduction of cell growth, suggesting that both cellular localizations are important for the activity of LINC01410. Transcriptomic analysis indicated a set of genes modulated in response to LINC01410 depletion, with an enrichment in genes involved in the cell cycle and DNA replication. An RNA-protein pull down (RPPD) assay identified three out of six MCM complex subunits (MCM4, MCM5, MCM7) as relevant protein interactors of LINC01410 and was confirmed using RNA-immunoprecipitation (RIP) assay. The MCM complex is a DNA helicase essential for genomic DNA replication, and we hypothesize that LINC01410 affects cell proliferation by interacting with this complex. We are now investigating this functional interaction by looking at the impact of LINC01410 modulation on the assembly of the complex, by using integrated mass spectrometry analysis, and on its ability to load onto chromatin by using chromatin immunoprecipitation sequencing (ChIP-Seq). In conclusion, we report the identification of LINC01410 as a novel lncRNA dependancy that supports MM cell growth via interacting with the MCM complex and controlling the cell cycle/DNA replication axis. Promising developments in the field of lncRNA inhibitors may allow forthcoming clinical applications.

FGFR1OP2 Promotes Proliferation and Survival of Myeloma Cells and Is a Potential Therapeutic Target

Background: Multiple myeloma (MM) is an incurable disease with high tendency to relapse and drug resistance. Exploring new targets and new drugs is crucial for treatment. Elevated expression of fibroblast growth factor receptor 1 oncogene partner 2 （FGFR1OP2） has been observed in relapsed and refractory MM and indicated the poor prognosis. FGFR1OP2 is expressed in diverse tissues, including bone marrow, spleen and thymus and might be a oncogene in lung cancer, acute leukemia. we hypothesize that FGFR1OP2 may exert effects in MM and will be a a potential therapeutic target. Aims: To Investigate the functional role of FGFR1OP2 in MM Methods: FGFR1OP2 knockdown and overexpression MM cell lines were generated. Molecular mechanism underlying was elucidated by qRT-PCR, Western Blot and gene expression microarray. Results: To study whether FGFR1OP2 is important for MM, we found high expression of FGFR1OP2 in different myeloma cell lines which was validated by CCLE datasets. Knockdown the FGFR1OP2 in MM cells led to a decreased proliferation, while overexpression of FGFR1OP2 increased the cell growth (Fig.1a). Next, flow cytometry was performed to evaluate the cell cycle and apoptosis in MM cells. FGFR1OP2 suppression showed cell cycle arrest and overexpression accelerateed cell cycle progression (Fig.1b). Furthermore, Bortezomib(Bor)-induced apoptosis of MM cells was significantly increased when FGFR1OP2 expression was suppressed (Fig.1c). Moreover, results of Western Blot revealed increased levels of Bor-induced caspase-3 and cleaved PARP after FGFR1OP2 knockdown. Taken together these data indicate that FGFR1OP2 can increase MM cell growth and inhibit apoptosis. To better understand the molecular mechanism of FGFR1OP2, we performed gene expression microarray profiling and compared results from FGFR1OP2-knockdown cells and control cells. Surprisingly, data showed that the expression of several members of the Hippo signaling pathway changed significantly. We performed Western Blot to validate these results, and found expression of YAP1 decreased while MST1/2 increased in FGFR1OP2-knockdown cells (Fig.1c). This suggests that the FGFR1OP2 promotes MM cell growth and anti-apoptosis through Hippo signaling pathway. Conclusion:FGFR1OP2 is critical for the proliferation and survival of MM cells through Hippo pathway and may represent a novel target for therapy. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

PHF19 Inhibits Multiple Myeloma Cell Response to Immunotherapy Via Promoting Immunosuppressive Microenvironment

Introduction: The multiple myeloma (MM) bone marrow (BM) microenvironment promotes tumor cell growth, survival, and drug resistance, while also conferring immunosuppression. This involves crosstalk between the myeloma cells and the components of BM microenvironment which can be facilitated or hindered by epigenetic modifiers altering the gene expression of receptors. Among those, regulatory T (Tregs) cells are essential to control peripheral tolerance and response to foreign and tumor antigens. Tregs within the BM niche play a significant role in the suppression of antitumor immune responses and limiting the beneficial response of immunotherapy in MM. Here, we investigated the impact of the Polycomb-like protein PHF19/PCL3, an epigenetic gene whose high level predicts poor prognosis in patients with MM, on the immunosuppressive BM microenvironment. Methods & Results: We first investigated how PHF19 overexpression would affect the microenvironment by using an ex vivo co-culture of MM cells with PBMCs or purified CD3+ T cells. MM cells that overexpressed PHF19 by lenti-virus infection (PHF19-OE cells) induced 2-4-fold higher conversion of conventional T cells (Tcon) into induced regulatory T cells (iTregs) (n=5, day 4). In addition, PHF19-OE MM cells increased the frequency of iTreg at later time points (day 7) and upregulated cell proliferation (CCND1, CCND2), anti-apoptosis (BCL2, BCL2L1), and Treg-related genes (TGFβ1, IL-10, Foxp3) (P < .0001). Moreover, enhanced checkpoint marker (PD1, TIM3, LAG3) expression was observed on Tcon co-cultured with PHF19-OE vs control MM cells. There were elevated IL-10 and TGFβ1 levels in the culture supernatants of PHF19-OE MM cells, alone and in co-cultures, and antibodies to these cytokines partially neutralized the Treg inhibition of Tcon proliferation triggered by PHF19-OE MM cells. Thus, PHF19 seems to be important in facilitating the crosstalk between MM cells and immune cells in the BM. CD38 expression on the MM cell surface is commonly targeted in immunotherapy. However, CD38 expression was downregulated on PHF19-OE vs -KD MM cells, and PHF19 mRNA expression was negatively correlated to CD38 expression in patient MM cells (Spearman's ρ = -0.38 and -0.2 for GSE5900 and GSE31161, P < .004). As expected, PHF19-OE MM cells were less susceptible than PHF19-KD MM cells to in vitro NK-mediated lysis induced by daratumumab (dara) or isatuximab, which target CD38, as evidenced by fewer CD107a+ and IFN γ+ NK effector cells. Moreover, dara-induced cytotoxicity was diminished in xenografted NSG mice with PHF19-OE vs control cells and reconstituted with human NK cells. These resistant PHF19-OE AMO1 tumors had lower expression of CD38, STAT1, and IFN-related genes, which produced higher levels of human κ light chain, soluble BCMA, and TGFβ1 in matched serum samples. Accordingly, PHF19-OE resulted in significantly decreased mouse survival. To find the mediators of the immunosuppression induced by PHF19, we used ATAC-seq and CHIP-seq analysis in MM cell lines. We found that a number of genes essential for T cell-mediated tumor immunity was downregulated in the PHF19 OE group vs control, including key genes in the interferon-γ (IFN-γ) signaling pathway, which is a pathway that leads to cytokine-mediated cell death. Among the genes of the IFN-γ pathway, 56 genes had less chromatin accessibility in PHF19 OE vs control cells. RNA-seq analysis confirmed that PHF19 OE repressed the expression of CD38 and the IFN-γ and IFN-α signaling pathway. Furthermore, PHF19 OE altered the expression of genes in NF-κB signaling triggered by TNF-α signaling pathway, which are associated with resistance to immunotherapy. Finally, activation of the PI3K/AKT pathway was also identified in PHF19 OE cells, which directly promotes MM cell proliferation and survival, as well as enhances resistance to immunotherapy via upregulation of PD-L1 on the MM cell surface. Conclusions: Taken together, these data indicate that PHF19 promotes an immunosuppressive BM milieu by promoting iTreg frequency and the expression of immunosuppressive cytokines, as well as decreasing CD38 expression on MM cells and diminishing their sensitivity to IFN-γ-mediated killing. These results suggest the potential clinical utility of targeting PHF19 to overcome immunosuppression and thereby enhance or restore sensitivity to CD38-targeted therapy in MM.

G6PD promotes cell proliferation and dexamethasone resistance in multiple myeloma via increasing anti-oxidant production and activating Wnt/β-catenin pathway

BackgroundGlucose-6-phosphate dehydrogenase (G6PD) as the rate-limiting enzyme in the pentose phosphate pathway (PPP) is well-established as an aberrantly expressed protein in numerous clinical diseases; however, its role in cancer, specifically in multiple myeloma (MM) remains elusive.MethodsIn this study, serum metabolites in 70 normal people and 70 newly diagnosed MM patients were analyzed using untargeted metabolomics and the results were verified using ELISA. The survival analysis of multiple clinical datasets was performed to identify a potential target gene in MM. The oncogenic role of G6PD was investigated using lentivirus-based overexpression or knockdown of G6PD using RNAi or an inhibitor in vitro, and in a xenograft mouse model in vivo. The mechanisms of induced Dexamethasone (Dexa)-resistance of G6PD were further explored using the above established MM cell lines in vitro.ResultsBased on the screening of potential genes, PPP was shown to be involved in the occurrence of MM, which was evidenced by the differential expression of serum metabolites of G6P and Dehydroepiandrosterone sulfate (DHEAS, the more stable sulfate ester form of an endogenously uncompetitive G6PD inhibitor known as DHEA). Elevated G6PD promoted MM cell proliferation. Mechanistically, high G6PD expression enhanced enzymatic generation of the antioxidant NADPH via the PPP and decreased the production of reactive oxygen species (ROS), thus inducing the proliferation and Dexa resistance in MM cells. Furthermore, canonical Wnt/β-catenin signaling also participated in regulating G6PD-induced drug resistance and cellular redox levels of ROS. Intriguingly, DHEA treatment could enhance the sensitivity of MM cells to Dexa primarily through augmenting cellular oxidative stress.ConclusionsOur data demonstrate that G6PD enhances the generation of the enzymatic anti-oxidant NADPH and decreases ROS generation, thereby promoting resistance to Dexa-induced apoptosis via the enzymatic PPP and non-enzymatic Wnt/β-catenin signaling pathway in MM. Targeting G6PD to harness cellular redox may serve as a promising novel strategy for the management of MM.

DAZAP1 facilitates the alternative splicing of KITLG to promote multiple myeloma cell proliferation via ERK signaling pathway.

Multiple myeloma (MM) is an incurable plasma cell malignancy, in which alternative pre-mRNA splicing (AS) acts as one of the key transcriptome modifier. The Deleted in Azoospermia-Associated Protein 1 (DAZAP1) is a splicing factor that has been identified as an oncogene in multiple cancers, yet its role in MM proliferation remains unclear. We first analyzed MM clinical databases and found that MM patients with elevated DAZAP1 had a poor survival. Furthermore, we overexpressed DAZAP1 by lentiviral transfection and utilized siRNA silencing the expression of DAZAP1 in MM cells. DAZAP1 promoted MM cell proliferation in vitro and accelerated MM xenograft tumor growth in vivo. KEGG pathway enrichment analysis showed that ERK signaling pathway was activated in DAZAP1-OE MM cells. The analyses of RIP-seq and RIP-qPCR revealed that DAZAP1 activated alternative splicing of KIT proto-oncogene ligand (KITLG) mRNA. Further study validated that DAZAP1 increased ERK phosphorylation via modulating alternative splicing of KITLG mRNA to promote MM cell proliferation. In conclusion, we establish DAZAP1 as a tumor-promoting gene with therapeutic potential and provide mechanistic insights into targeting DAZAP1 as a new strategy for the diagnosis and treatment of MM.

Elevated SFXN2 limits mitochondrial autophagy and increases iron-mediated energy production to promote multiple myeloma cell proliferation.

Human sideroflexin 2 (SFXN2) belongs to the SFXN protein family, which is a mitochondrial outer membrane protein involved in mitochondrial iron metabolism. Mitochondria are indispensable for cellular energy production and iron metabolism. However, it remains elusive how SFXN2 modulates mitochondrial homeostasis and cellular iron metabolism in multiple myeloma (MM). In this study, we first found that SFXN2 was significantly elevated and correlated to poor outcomes in MM patients from clinical datasets. SFXN2 overexpression promoted MM cell proliferation and suppressed starvation-induced autophagy/mitophagy, while SFXN2 knockdown aggravated mitochondria damage and autophagic processes in ARP1 and H929 MM cell lines. Furthermore, inhibition of SFXN2 exerted effectively anti-myeloma activity in vivo by using myeloma xenograft model. Mechanism studies indicated that heme oxygenase 1 (HO1) with anti-oxidant function contributed to the process of autophagy suppression and cellular proliferation mediated by SFXN2. Our study revealed the critical role of SFXN2 in regulating mitochondrial bioenergetics, mitophagy, cellular iron metabolism, and redox homeostasis in interconnected and intricate way. Collectively, these findings not only provide insights into the metabolic reprogramming of tumor cells, but also highlight the therapeutic potential of SFXN2 in combination with iron metabolism as target for prognosis and treatment in MM patients.

NORAD promotes multiple myeloma cell progression via BMP6/P-ERK1/2 axis

Multiple myeloma (MM) is one of the most common tumors of the hematological system and remains incurable. Recent studies have shown that long noncoding RNA NORAD is a potential oncogene in a variety of tumors. However, the general biological role and clinical value of NORAD in MM remains unknown. In this study, we measured NORAD expression in bone marrow of 60 newly diagnosed MM, 30 post treatment MM and 17 healthy donors by real-time quantitative polymerase chain reaction (qPCR). The NORAD gene was knockdown by lentiviral transfection in MM cell lines, and the effects of NORAD on apoptosis, cell cycle and cell proliferation in MM cells were examined by flow cytometry, CCK8 assay, EDU assay and Western blot, and the differential genes after knockdown of NORAD were screened by mRNA sequencing, followed by in vivo experiments and immunohistochemical assays. We found that knockdown of NORAD promoted MM cell apoptosis, induced cell cycle G1 phase arrest, and inhibited MM cell apoptosis in in vivo and in vitro experiments. Mechanistically, NORAD plays these roles through the BMP6/P-ERK1/2 axis. We discuss a novel mechanism by which NORAD acts pro-tumorigenically in MM via the BMP6/P-ERK1/2 axis.

AIMP1 promotes multiple myeloma malignancy through interacting with ANP32A to mediate histone H3 acetylation

Multiple myeloma (MM) is the second most common hematological malignancy. An overwhelming majority of patients with MM progress to serious osteolytic bone disease. Aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1) participates in several steps during cancer development and osteoclast differentiation. This study aimed to explore its role in MM. The gene expression profiling cohorts of MM were applied to determine the expression of AIMP1 and its association with MM patient prognosis. Enzyme-linked immunosorbent assay, immunohistochemistry, and Western blotting were used to detect AIMP1 expression. Protein chip analysis, RNA-sequencing, and chromatin immunoprecipitation and next-generation sequencing were employed to screen the interacting proteins and key downstream targets of AIMP1. The impact of AIMP1 on cellular proliferation was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in vitro and a xenograft model in vivo. Bone lesions were evaluated using tartrate-resistant acid phosphatase staining in vitro. A NOD/SCID-TIBIA mouse model was used to evaluate the effect of siAIMP1-loaded exosomes on bone lesion formation in vivo. AIMP1 expression was increased in MM patients and strongly associated with unfavorable outcomes. Increased AIMP1 expression promoted MM cell proliferation in vitro and in vivo via activation of the mitogen-activated protein kinase (MAPK) signaling pathway. Protein chip assays and subsequent experiments revealed that AIMP1 interacted with acidic leucine-rich nuclear phosphoprotein 32 family member A (ANP32A) to regulate histone H3 acetylation. In addition, AIMP1 increased histone H3 acetylation enrichment function of GRB2-associated and regulator of MAPK protein 2 (GAREM2) to increase the phosphorylation of extracellular-regulated kinase 1/2 (p-ERK1/2). Furthermore, AIMP1 promoted osteoclast differentiation by activating nuclear factor of activated T cells c1 (NFATc1) in vitro. In contrast, exosome-coated small interfering RNA of AIMP1 effectively suppressed MM progression and osteoclast differentiation in vitro and in vivo. Our data demonstrate that AIMP1 is a novel regulator of histone H3 acetylation interacting with ANP32A in MM, which accelerates MM malignancy via activation of the MAPK signaling pathway.

NAT10 acetylates BCL-XL mRNA to promote the proliferation of multiple myeloma cells through PI3K-AKT pathway.

Multiple myeloma (MM) is a clinically distinctive plasma cell malignancy in the bone marrow (BM), in which epigenetic abnormalities are featured prominently. Epigenetic modifications including acetylation have been deemed to contribute to tumorigenesis. N-acetyltransferase 10 (NAT10) is an important regulator of mRNA acetylation in many cancers, however its function in MM is poorly studied. We first analyzed MM clinical databases and found that elevated NAT10 expression conferred a poor prognosis in MM patients. Furthermore, overexpression of NAT10 promoted MM cell proliferation. The correlation analysis of acRIP-seq screened BCL-XL (BCL2L1) as a significant downstream target of NAT10. Further RNA decay assay showed that increased NAT10 improved the stability of BCL-XL mRNA and promoted protein translation to suppress cell apoptosis. NAT10 activated PI3K-AKT pathway and upregulated CDK4/CDK6 to accelerate cellular proliferation. Importantly, inhibition of NAT10 by Remodelin suppressed MM cell growth and induced cell apoptosis. Our findings show the important role of NAT10/BCL-XL axis in promoting MM cell proliferation. Further explorations are needed to fully define the potential of targeting NAT10 therapy in MM treatment.