Role In Development Of Multiple Myeloma 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.

Abnormal expression pattern of lncRNA H19 participates in multiple myeloma bone disease by unbalancing osteogenesis and osteolysis

Accumulating genetic and epigenetic alterations in multiple myeloma (MM) have been demonstrated to be closely associated with osteolytic bone disease, generally characterized as increased osteoclast formation and decreased osteoblast activity. Previously, serum long non-coding RNA (lncRNA) H19 has been proved to be a biomarker for the diagnosis of MM. Whereas, its role in MM-associated bone homeostasis remains largely elusive. A cohort of 42 MM patients and 40 healthy volunteers were enrolled for evaluating differential expressions of H19 and its downstream effectors. The proliferative capacity of MM cells was monitored by CCK-8 assay. Alkaline phosphatase (ALP) staining and activity detection, either with Alizarin red staining (ARS) were employed to assess osteoblast formation. Osteoblast- or osteoclast-associated gene were detected using qRT-PCR and western blot analysis. Bioinformatics analysis, RNA pull-down, RNA immunoprecipitation (RIP), and chromatin immunoprecipitation (ChIP) were subjected to verify H19/miR-532-3p/E2F7/EZH2 axis, which was accounted for epigenetic suppression of PTEN. The functional role of H19 on MM development through unbalancing osteolysis and osteogenesis was also confirmed in the murine MM model. Upregulation of serum H19 was observed in MM patients, suggesting its positive correlation with the poor prognosis of MM patients. Loss of H19 dramatically weakened cell proliferation of MM cells, promoted osteoblastic differentiation, and impaired osteoclast activity. While reinforced H19 exhibited the opposite effects. Akt/mTOR signaling plays an indispensable role in H19-mediated osteoblast formation and osteoclastgenesis. Mechanistically, H19 served as a sponge for miR-532-3p to upregulate E2F7, a transcriptional activator of EZH2, thereby accounting for modulating epigenetic suppression of PTEN. The in vivo experiments further validated that H19 exerted important impacts on tumor growth through breaking the balance between osteogenesis and osteolysis via Akt/mTOR signaling. Collectively, increased enrichment of H19 in MM cells exhibits an essential role in MM development by disturbing bone homeostasis.

MiRNA as a Potential Target for Multiple Myeloma Therapy-Current Knowledge and Perspectives.

Multiple myeloma (MM) is the second most common hematological malignancy. Despite the huge therapeutic progress thanks to the introduction of novel therapies, MM remains an incurable disease. Extensive research is currently ongoing to find new options. MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate gene expression at a post-transcriptional level. Aberrant expression of miRNAs in MM is common. Depending on their role in MM development, miRNAs have been reported as oncogenes and tumor suppressors. It was demonstrated that specific miRNA alterations using miRNA mimics or antagomirs can normalize the gene regulatory network and signaling pathways in the microenvironment and MM cells. These properties make miRNAs attractive targets in anti-myeloma therapy. However, only a few miRNA-based drugs have been entered into clinical trials. In this review, we discuss the role of the miRNAs in the pathogenesis of MM, their current status in preclinical/clinical trials, and the mechanisms by which miRNAs can theoretically achieve therapeutic benefit in MM treatment.

Investigating the Interplay between Myeloma Cells and Bone Marrow Stromal Cells in the Development of Drug Resistance: Dissecting the Role of Epigenetic Modifications.

Simple SummaryDespite advances made in the last two decades, multiple myeloma (MM) is still an incurable disease. The genetic complexity of MM and the presence of intra-clonal heterogeneity are major contributors to disease relapse and the development of treatment resistance. Additionally, the bone marrow microenvironment is known to play a pivotal role in MM disease progression. Together with genetic modifications, epigenetic changes have been shown to influence MM development and progression. However, epigenetic treatments for MM are still lacking. This is mainly due to the high rate of adverse events of epigenetic drugs in clinical practice. In this review, we will focus on the role of epigenetic modifications in MM disease progression and the development of drug resistance, as well as their role in shaping the interplay between bone marrow stromal cells and MM cells. The current and future treatment strategies involving epigenetic drugs will also be addressed.Multiple Myeloma (MM) is a malignancy of plasma cells infiltrating the bone marrow (BM). Many studies have demonstrated the crucial involvement of bone marrow stromal cells in MM progression and drug resistance. Together with the BM microenvironment (BMME), epigenetics also plays a crucial role in MM development. A variety of epigenetic regulators, including histone acetyltransferases (HATs), histone methyltransferases (HMTs) and lysine demethylases (KDMs), are altered in MM, contributing to the disease progression and prognosis. In addition to histone modifications, DNA methylation also plays a crucial role. Among others, aberrant epigenetics involves processes associated with the BMME, like bone homeostasis, ECM remodeling or the development of treatment resistance. In this review, we will highlight the importance of the interplay of MM cells with the BMME in the development of treatment resistance. Additionally, we will focus on the epigenetic aberrations in MM and their role in disease evolution, interaction with the BMME, disease progression and development of drug resistance. We will also briefly touch on the epigenetic treatments currently available or currently under investigation to overcome BMME-driven treatment resistance.

Association of RANK and RANKL gene polymorphism with survival and calcium levels in multiple myeloma.

Multiple myeloma (MM) is a heterogeneous bone marrow cancer characterized by proliferation of malignant plasma cells in the bone marrow. One of its major symptoms are hypercalcaemia and bone lesions, which may result in pathologic bone fractures. Receptor activator for nuclear factor κB (RANK) and its ligand, RANKL, are part of an activation pathway for osteoclasts and are thus responsible for bone resorption. Furthermore, RANKL expression is increased in multiple myeloma. In the present study, we investigated the role of single nucleotide polymorphisms (SNPs) in the genes coding for RANK (rs1805034, rs8086340), RANKL (rs7325635, rs7988338), and TACI (rs34562254), a receptor for osteoclast-derived pro-survival factors. The study involved 222 patients and 222 healthy individuals, and the analysis included disease susceptibility, survival, bone lesions, calcium levels, and vascular endothelial growth factor levels. Patients with allele RANK rs1805034 C had higher survival (p = .003). This relationship was especially evident in women (p = .006). Furthermore, allele rs1805034 C was associated with slightly lower median age at diagnosis (64.0 vs. 65.5, p = .008). Allele RANKL rs7325635 A correlated with lower progression-free survival (p = .027), and with lack of early progression (p = .023). Additionally, women with allele rs7325635 G were found to have higher calcium blood concentration (p = .040). Allele TACI rs34562254 A was more common in MM patients in more advanced stages (II and III stage International Staging System) at diagnosis (p = .017), and the SNP showed a slight trend towards association in a multivariate analysis (p = .084). Taken together, our results suggest that RANK rs1805034 and RANKL rs7325635 may have a role in MM development and progression.

Unveiling molecular associations of polymorphic variants of VDR gene (FokI, BsmI and ApaI) in multiple myeloma patients of Indian population

Multiple myeloma (MM) is a plasma cell malignancy frequently accompanied with skeletal co-morbidity. Vitamin D (1,25(OH)2D) is an important mediator of skeletal homeostasis that mediates its effect by binding to vitamin D receptor (VDR), a steroid family receptor and modulates various downstream pathways. Multiple polymorphisms have been determined in VDR gene that witnessed significant association with cancer development and progression. Therefore, in this maiden study, we recruited 75 newly diagnosed MM patients and 75 control subjects. 25-hydroxy vitamin D (25(OH)D) levels were measured in all recruited study subjects. Further, PCR-RFLP was performed in DNA samples of recruited study subjects. Results demonstrated significantly decreased 25(OH)D levels in MM patients compared to controls. Additionally, decreased 25(OH)D levels in MM patients inversely associated with disease severity. Further, single nucleotide polymorphism (SNP) analysis of VDR gene showed significantly higher risk of MM disease development in Ff + ff, Aa + aa, and Bb + bb genotypes. Additionally, FokI f, ApaI a and BsmI b alleles were significantly associated with MM occurrence. In conclusion, this study provided initial evidences of association between 25(OH)D insufficiency, VDR gene polymorphism and MM development. Thus, we suggest that a study involving assessment of 25(OH)D levels and VDR gene polymorphism in large patients’ cohort might substantiate their role in MM development which would further provide impetus to give 25(OH)D supplementation along with conventional chemotherapeutic agents for myeloma treatment in future.

PF566 INCREASE OF MITOCHONDRIAL ACTIVITY CONTRIBUTES TO RELAPSE IN MULTIPLE MYELOMA, A NOVEL THERAPEUTIC OPPORTUNITY

Background:Preliminary results (Ruiz‐Heredia, ASH 2017) showed an increase of the mitochondrial burden in the Multiple Myeloma (MM) and its progression, suggesting to have an important role in the pathogenesis of the disease.Aims:We planned to decipher the role of the mitochondria in the MM disease and its progression, and the potential exploitation of mitochondrial activity as a functional target in the MM therapy.Methods:In order to understand the role of mitochondria in MM and its therapeutic exploitation, firstly we studied factors involved in the mitochondrial function gene expression (c‐Myc, TFAM, EF‐Tu, NRF1 and HNRNPK RT‐PCR), protein expression (COXII IHC), and mitochondrial activity (histoenzymatic‐HE assay of COX) in 77 MM patients.Furthermore, we have tested the effect of tigecycline, a mitochondrial inhibitor, alone or in combination with bortezomib in the MM cell lines JJN3, L363 and NCI‐H929. To characterized the molecular mechanisms underlying the cytotoxic effect of tigecycline we analysed OXPHOS expression by WB and mitochondria activity by HE assay. Finally, we followed an in vivo experiment in NSG mice (n = 40) 6–8 week‐old engrafted with the JJN3‐GFP cell line (1 x 106) via tail vein and treated by 4 weeks. Analysis of the in vivo imaging and survival curve were obtained.Results:Mitochondrial representative gene and protein expression and activity were found increased in MM relapse stage patients. We showed overexpression of C‐Myc, TFAM and EF‐Tu, and an increased tendency for HNRNPK on the MM relapsed group (n = 34) (Fig. 1A). Moreover, IHC reveals overexpression of mitochondrial COXII protein in relapse MM patients (n = 32; p‐value ∗∗ <0.001) (Fig. 1B). By functional assays we have demonstrated that gene and protein overexpression drives to an increase of activity (COX HE) in MM at relapse (N = 11 p‐value ∗∗∗<0.0001). (Fig. 1C). Together these results suggest elevation of mitochondrial activity plays a role in the mechanism of resistance to treatment and/or progression of MM and the consequent relapse of the patients.In vitro studies with tigecyline and the combination with the frontline MM drug, bortezomib showed cytotoxic effects in three MM cell lines (IC50 JJN3 11,91 μM; IC50 L363 10,21 μM and NCI‐H929 26,37 μM, p‐value ∗<0.05). Moreover, bortezomib and tigecyline showed high levels of synergism (CI 0,19) (Fig. 1D). The cells treated with tigecycline and the combination reflect diminishing in the expression of the respiratory chain complexes, suggesting a reduction of mitochondrial activity, and being validated in lower activity measured by the HE assay of COX (Fig. 1E). Finally, mice groups treated with tigecycline alone or in combination with bortezomib reported a better survival and lower JJN3‐GFP infiltration (n = 40; p‐value ∗<0.05) (Fig. 1F).Summary/Conclusion:To sum up, we observed that mitochondria activity plays a pivotal role in MM development and specially its progression and/or potential treatment resistance, correlating the increase of activity with MM patient's poor outcomes and relapse prone.imageWe proof the potential therapeutic exploitation of mitochondria in the disease, and the value of tigecycline, in monotherapy and in a synergic combination with frontline MM treatment Bortezomib. This new approach should be considered as a novel target therapy in MM, especially in relapse patients.

Proteomic and Biological Analysis of Myeloma Cell Derived Extracellular Vesicles

Intercellular communication between multiple myeloma (MM) cells and the normal bone marrow stroma leads to a modification of the bone marrow microenvironment, which favors tumor progression. New developments in extracellular vesicle (EV) research suggest that this diverse population of vesicles, released by cancer cells including MM cells, express transmembrane proteins and carry cargo that can modify recipient cells in myriad ways. In particular, tumor-derived EVs have been shown to create permissive microenvironments that lead to metastatic colonization by circulating tumor cells. As we have previously shown that MM EVs can enhance proliferation of recipient MM cells, we hypothesize that MM EVs can potentially play a much larger role in MM development and progression. In order to understand the scope of potential EV roles in MM, we executed a comprehensive proteomic analysis of the cargo of MM EVs. We isolated EVs from patient derived MM cell lines that represent the most common genetic variants of this tumor, and used in vitro generated plasma cells (IVPCs) as a reference population. In a first pass analysis, we selected proteins that were expressed ≥3 fold higher in MM EVs than in IVPC EVs, and this analysis identified 306 proteins. Of interest, included in the 306 differentially proteins were several involved in the regulation of cell adhesion such as members of the a disintegrin and metalloprotease domain (ADAM8, 9, 10, 13, 15 and 22) family, which are also associated with inhibition of cell proliferation. Moreover, CEACAM1, PTPRK, and CDH2, which are also linked to cellular adhesion, were also expressed at a higher level in MM EVs. Various proteins linked to myeloma cell biology were likewise found to be over-represented in MM EVs, and these include BCMA, ITGAV, ITGB5, IL6ST (gp130), CD276 (B7-H3), and CD28. As we are most interested in biologically relevant and actionable proteins present uniquely in MM derived EVs, we filtered from our data proteins that were also present in EVs from IVPCs. We further filtered out proteins known to be present in EVs from normal cells. This filtering strategy reduced the number of interesting candidates to 8, which included CD28, MET, TRKC, and ADAM15. Thus far, we have confirmed the presence of these 4 proteins in a panel of MM EVs, and we are currently in the process of validating additional candidate cargo proteins for their biological role in enhancing tumor cell proliferation and/or protection from apoptosis. In summary, EV proteomic analysis of cell lines representing MM genetic subtypes can lead to the identification of biologically relevant proteins transported systemically by EVs as well as suggest novel biomarkers that are easily detectable in plasma and may permit earlier recognition of disease progression in patients with MM. DisclosuresNo relevant conflicts of interest to declare.

CUL4A as a marker and potential therapeutic target in multiple myeloma.

Multiple myeloma is the most common cause of death of hematological malignancy worldwide. Cullin 4A has been proposed as oncogene in several types of human cancer, but the expression and function of cullin 4A in multiple myeloma remain unclear. Here, we demonstrate that cullin 4A plays an oncogenic role in multiple myeloma development. The expression of cullin 4A was detected by quantitative real-time polymerase chain reaction in multiple myeloma patients and multiple myeloma cell lines. In addition, silencing of cullin 4A with small interfering RNA was performed in human multiple myeloma cells, and the impact on proliferation, cell cycle, apoptosis, migration, and invasion of the multiple myeloma cells was analyzed. We found that the level of cullin 4A in serum samples was significantly upregulated in patients with multiple myeloma compared with healthy control subjects. Knockdown of cullin 4A via small interfering RNA inhibited the proliferation of the multiple myeloma cell lines by delaying cell-cycle progression and increasing apoptosis. cullin 4A downregulation inhibited multiple myeloma cell migration and invasion in vitro. Our results suggested that cullin 4A could be a promising therapy target in multiple myeloma patients.

Restoration of Mir-138 Expression By Epigenetic Modulation Overcomes Drug Resistance in Multiple Myeloma Cells

Multiple myeloma (MM) is a plasma cell malignancy characterized by highly heterogeneous genomic alteration including frequent changes in chromatin remodeling enzymes. The recent studies showed that deregulation of epigenetics mechanisms play an essential role in MM development. In particular, overexpression of enhancer of zeste homologue 2 (EZH2), the catalytic subunit of Polycomb Complex 2 (PRC2), has been shown in several cancers including MM. However, the detailed function of EZH2 histone methyltransferase in drug resistance of MM has not yet been elucidated. This study sought to investigate the role of histone modification changes in drug resistance of MM. First, we checked if the expression level of the epigenetic modulating enzyme, EZH2, changed in drug resistant cells (8226-R5 and MM1R) in comparison to parental sensitive cells (8226 and MM1S). We found that EZH2 expression was upregulated in 8226-R5 and MM1R cells. In addition, the global H3K27me3 level, a silencing histone modification mark induced by EZH2, was dramatically increased in the resistant MM cells. To support our finding, we analyzed some publically available gene expression datasets (GSE 6477 and GSE26760) and found that the EZH2 expression level was significantly upregulated in relapsed patients in comparison to newly diagnosed MM patients. It also revealed that overexpression of EZH2 correlated with the progression of the disease and poor survival of the MM patients.We next examined the functional effect of EZH2 inhibition on resistant cells using a novel selective EZH2 inhibitor (EPZ-6438) which turned out to significantly inhibit proliferation of MM cells by MTT assay. Furthermore, combination of EPZ-6438 with bortezomib revealed synergistic cytotoxicity effects on 8226-R5 and MM1R cells. In parallel, global H3K27me3 level in MM cells was reduced by EPZ-6438 further confirming its specific functionality. To explore whether miRNAs are associated with EZH2 overexpression in drug resistance, we used several target scan algorithms and identified mir-138, a tumor suppressor miRNA, to potentially target EZH2. We found that mir-138 expression level was downregulated in 8226-R5 and MM1R relative to 8226 and MM1S, respectively. To investigate if the reduction is due to overexpression of EZH2, we performed H3k27me3 chip on the promoter region of mir-138 gene in MM cell lysates. The chip qPCR showed that occupancy of H3K27me3 in the promoter region of mir-138 was increased in 8226-R5 and MM1R cells compared to 8226 and MM1s cells leading to repression of mir-138 gene transcription in the resistant cells.As a result, we concluded that reduction of mir-138 expression level in the resistant MM cells is due to chromatin remodeling changes in its promoter region and identified mir-138 gene as a target of EZH2.To further demonstrate the role of EZH2 in mir-138 expression, 8226-R5 and MM1R were treated with EZH2 inhibitor and mir-138 expression level was compared to untreated cells. We found a significant upregulation of mir-138 expression in EPZ-6438 treated cells compared with untreated controls. The chip qPCR results also confirmed that the inhibition of EZH2 decreased H3K27me3 occupancy on the mir-138 promoter region which indicated that epigenetic silencing is mechanism underlying miR-138 suppression in drug resistant cells. Furthermore, we overexpressed mir-138 in 8226-R5 and MM1R cells and treated them with bortezomib to assess cell viability using MTT assay. Overexpression of mir-138 sensitized 8226-R5 and MM1R cells to bortezomib. We also observed that overexpression of mir-138 reduced EZH2 expression level. These results suggest a negative feedback loop between miR-138 and EZH2 in our model system.Altogether, these findings indicate that downregulation of miR-138, likely due to EZH2 overexpression, contributes to drug resistance of MM and the restoration of mir-138 expression by epigenetics modulation re-sensitizes drug resistant MM cells to anti myeloma drugs. We report, for the first time, that miR-138 is involved in a negative feedback loop with EZH2 in MM cells and provide a framework for targeting EZH2 or restoration of mir-138 as novel strategies for the treatment of MM. DisclosuresNo relevant conflicts of interest to declare.

RETRACTED: Downregulation of p53-inducible microRNAs 192, 194, and 215 Impairs the p53/MDM2 Autoregulatory Loop in Multiple Myeloma Development

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the editors. This correction has been retracted because the article that it relates to has now been retracted at the request of the editors.

Small RNA Deep Sequencing Highlights the Important Contribution of Mirnas in Regulating IRF4/c-Myc Axis in Myeloma Development

Introduction: Multiple myeloma (MM) is a hematologic malignancy characterized by the accumulation of plasma cells (PCs) in the bone marrow (BM). Over 50% of patients die within 5 years of diagnosis. The transition from normal PCs to active MM, via premalignant condition (monoclonal gammopathy of undetermined significance; MGUS), consists of many oncogenic events, including upregulation of cyclin D1 and IRF4 genes, as well as activating mutations in NRAS, and KRAS. Despite recent advances in oncogenomics, further studies are needed to identify critical players in MM pathogenesis that could be targeted for pharmacological intervention to improve outcome. Recently, aberrations in epigenetic modifications, including DNA modifications and miRNA expression have been shown to play a crucial role in development and progression of MM. miRNAs are short non-coding RNAs that bind to complementary sequences on target messenger RNA (mRNAs) and downregulate their expression by inhibiting mRNA translation, or inducing its degradation. miRNA analysis, may lead to improved understanding of MM biology and classification, by establishing associations between gene expression changes and MM molecular and clinical features. To assess whether miRNA deregulation plays a critical role in the development of MM we performed small RNA next generation sequencing in the PCs isolated from 3 patients at the MGUS stage and after that they developed active disease, but still untreated. miRNA deregulation was also validated in an independent set of newly diagnosed MM patients (n.34) compared to non-cancer age matched donors (n.6). Mechanisms of transcriptional regulation and biological roles of the differentially expressed miRNAs were also analyzed.Methods: 1x106 CD138+ frozen PCs (purity>90%) from different 3 donors before and after the disease development were used for the analysis. RNA was extracted with RNA-DNA-protein kit (Norgen Biotek) and 0.8µg of total RNA was used to generate the cDNA libraries using TruSeq Small RNA Library Preparation Kit. The obtained cDNA libraries were sequenced on an ILLUMINA system through the OSU Genomic Shared Resource (GSR). Myeloma cells (MM.1S) were treated with pan-HDACi for 24 hours and total miRNA expression was analyzed by nCounter microRNA array (NanoString Technologies, Inc.). miRNA deregulation upon use of several pan-HDAC'i in clinical use (LBH589, SAHA and AR-42) were validated in 4 different cell lines and in the MM cells of newly diagnosed MM patients. Chromatin immunoprecipitation, silencing RNA for specific histone deacetylase enzymes (HDACI, HDAC2, HDAC3, and HDAC6), western blot analysis, luciferase assays, stem loop RT-PCR, q-RT-PCR and cell proliferation assays were also performed.Results: We found that several miRNAs are commonly deregulated during disease transition. Some of these miRNAs, including miR-223, miR-221, miR-222, miR-92a and miR-93 (p<0.05) were commonly upregulated, where instead the majority of c-Myc transcriptionally repressed miRNAs, including miR-29s family, were found to be downregulated in the MM-PCs compared to the MGUS-PCs obtained from the same patients. Our data also show that IRF4 expression in MM cells is directly under the control of c-Myc regulated miRNAs, which we found downregulated during the multi-step transformation process of the PCs. We also observed that the use of pan-HDACi's in clinical use, including the recently FDA approved panobinostat (LBH589), in MM cells is able to upregulate the expression of those miRNAs and subsequently downregulate IRF4 at the posttranscriptional level. We also dissected the role of different histone deacetylases to specifically modulate miRNA expression and consequently IRF4-MYC pathway in MM cells.Conclusions: Collectively, we believe, that these findings support the key role of miRNA aberrant expression in PC transformation. Their role in regulating the expression of IRF4 during myeloma development and lead us to speculate that this explains why IRF4 and c-Myc mRNA levels are higher in newly diagnosed MM patients, without obvious chromosomal abnormalities, compared to MGUS patients. Understanding of the molecular bases of how c-Myc expression can be regulated by a specific histone deacetylase via modulation of miRNA levels will have important impact not only on myeloma therapy, but also other hematopoietic malignancies involving c-Myc deregulation. DisclosuresNo relevant conflicts of interest to declare.

Myelopoiesis dysregulation associated to sustained APRIL production in multiple myeloma-infiltrated bone marrow.

Multiple myeloma (MM) is a non-curable tumor developing in the bone marrow (BM). The BM microenvironment rich in hematopoietic precursors is suspected to have a role in MM development. Here we show that a proliferation-inducing ligand (APRIL) mediated in vivo MM promotion. In MM-infiltrated BM, APRIL originated from differentiating myeloid cells with an expression peak in precursor cells. Notably, APRIL expression stayed stable in BM despite MM infiltration. The pool of APRIL-producing cells changed upon MM infiltration. Although CD16(+) mature myeloid cells constituted about half of the APRIL-producing cells in healthy BM, CD16(-) Elastase(+) myeloid precursor cells were predominant in MM-infiltrated BM. Myeloid precursor cells secreted all the APRIL they produced, and binding of secreted APRIL to MM cells, strictly dependent of heparan sulfate carried by CD138, resulted in an in situ internalization by tumor cells. This indicated APRIL consumption by MM in BM. Taken together, our data show that myelopoiesis dysregulation characterized by an increased proportion of precursor cells occurs in MM patients. Such dysregulation correlates with a stable expression of the MM-promoting factor APRIL in infiltrated BM.

RETRACTED: Downregulation of p53-inducible microRNAs 192, 194, and 215 Impairs the p53/MDM2 Autoregulatory Loop in Multiple Myeloma Development

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the editors. This article was published on October 19, 2010, and Figures 4A and 7A were later corrected on August 8, 2016. In January 2021, The Ohio State University notified the Cancer Cell editors that an internal investigation concluded that Figures 1E, 4A, 4D, 5A, and 7A were falsified and that part of Figure 1E of the article is the same as part of Figure 1F in the correction of another article (Pichiorri et al., 2017, J. Exp. Med., 214, 1557, https://doi.org/10.1084/jem.2012095001172017c) and recommended retraction of the article. The editors no longer have confidence in the validity of the data and are retracting the article. S.-S. S. agrees with the retraction, and F.P., C.H., A.P., and C.M.C. disagree with the retraction; all other authors couldn't be reached or didn't respond.

Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) DNA sequences are absent in leukapheresis products and ex vivo expanded CD34+ cells from multiple myeloma patients.

Recently it was reported that Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) infects bone marrow (BM) dendritic cells (DC) in multiple myeloma (MM) patients and therefore might play a role in MM development. Because of the use of myeloid growth factors like GM-CSF and G-CSF for the mobilization of peripheral blood progenitor cells (PBPC), the subsequent increase of DC precursors might imply a risk for KSHV contamination in PBPC grafts. Therefore, in this study leukapheresis products and ex vivo cultured CD34+ cell suspensions were analysed. KSHV DNA could not be amplified in any of them.