Immune Response In Multiple Myeloma Research Articles

BET Inhibitor JQ1 Selectively Reduce Tregs by Upregulating STAT3 and Suppressing PD-1 Expression in Patients with Multiple Myeloma.

Multiple myeloma (MM) stands as a prevalent hematological malignancy, primarily incurable, originating from plasma cell clones. MM's progression encompasses genetic abnormalities and disruptions in the bone marrow microenvironment, leading to tumor proliferation, immune dysfunction, and compromised treatment outcomes. Emerging evidence highlights the critical role of regulatory T cells (Tregs) in MM progression, suggesting that targeting Tregs could enhance immune functionality and treatment efficacy. In this study, a notable increase in Treg proportions within MM patients' bone marrow (BM) compared to healthy individuals is observed. Additionally, it is found that the bromodomain and extraterminal domain (BET) inhibitor JQ1 selectively diminishes Treg percentages in MM patients' BM and reduces TGF-β1-induced Tregs. This reduction occurs via inhibiting cell viability and promoting apoptosis. RNA sequencing further indicates that JQ1's inhibitory impact on Tregs likely involves upregulating STAT3 and suppressing PD-1 expression. Collectively, these findings suggest JQ1's potential to modulate Tregs, bolstering the immune response in MM and introducing a promising avenue for MM immunotherapy.

Analysis of COVID-19-Associated Proteins Identifies TANK-Binding Kinase 1 As an Immunotherapeutic Target in Multiple Myeloma

Background and Rationale. Patients with multiple myeloma (MM) are at a higher risk of viral infection due to immune deficiency, as recently highlighted by the severity of COVID-19 in MM patients. However, the mechanism(s) underlying the lack of anti-viral immune response in MM are unclear. We have previously shown that there are more plasmacytoid dendritic cells (pDCs) in the bone marrow of MM patients than in the bone marrow of healthy individuals and that these dysfunctional patient pDCs suppress T and NK cell-mediated immunity. Importantly, pDCs play a key role in both recognizing viral nucleic acid and initiating anti-viral immunity via type 1 interferon (IFN) response signaling. Therefore, we analyzed the immune-pathway proteins implicated in COVID-19-host interactions [COVID-19 protein interaction map, Gordon et al, Nature 2020; 583, 459-568] to assess whether pDC-MM interactions modulate these pathways to confer immune suppression and susceptibility to COVID-19. Results. We first assessed whether the expression of human genes involved in the COVID-19-host interaction changes when ex vivo MM cells are co-cultured with patient pDCs (compared to MM cells alone). We found that 41 of these genes were differentially expressed in MM cells when exposed to pDCs (log2Fold change: ± 3.5-fold; p < 0.00001), and this expression varied widely (median (log10): -0.13 to 4.5; adj p < 0.001). Three of these genes are linked to innate immunity and are essential for IFN production in MM cells - TBK1, IRF3 (Interferon regulatory factor 3), and RAE1 (interferon-inducible mRNA nuclear export factor). Importantly, pDCs downregulated the expression of TBK1 (Log2FC: -0.5) and RAE1 (Log2FC: -0.3) and upregulated the expression of IRF3 (Log2FC: 1.5) in MM cells after coculture (compared to MM cells alone, p < 0.0001). Concordantly, analysis of publicly available gene profiling datasets on relapsed MM patients showed low levels of TBK1 and RAE1 and higher levels of IRF3 (n = 50) (Log2FC: TBK1: -0.208; RAE1: -0.286; IRF3: 0.273; vs normal; p < 0.05). Of note, TBK1 expression was positively correlated with prognosis (n = 350, p = 0.026). We found that most of the 41 genes were also expressed in pDCs (NCBI GEO Datasets based on pDC cell line CAL1 and human peripheral blood pDCs). In unstimulated pDCs, TBK1 expression was significantly lower than IRF3 and RAE1 expression (2-3-fold, p < 0.05). Yet treating pDCs with CpG-ODN type-A, which induces IFN-α expression, increased both TBK1 (adj P = 0.004) and RAE1 (adj P = 0.043) expression, without significantly altering IRF3 expression. Finally, COVID-19 relies on the host ubiquitin-proteasome system for propagation, and we found that targeting ubiquitin receptor Rpn13 with the specific inhibitor RA190 restored TBK1 expression in MM cell lines, indicating the potential clinical use of targeting Rpn13 in restoring anti-viral immune responses in MM. Conclusion. Taken together, we show that TBK1 is downregulated in pDCs, and pDCs interacting with MM cells further decrease TBK1 expression in MM cells, thereby attenuating IFN-mediated anti-viral immune response signaling. Our findings suggest that: 1) low levels of TBK1 may confer increased susceptibility of MM patients to COVID-19 and 2) targeting TBK1 may restore the anti-viral immune response and reduce COVID-19 severity in MM.

Immune Profiling of MM Microenvironment at Single-Cell Resolution

Background: The survival of multiple myeloma (MM) is highly dependent on the support of immune microenvironment. However, it is still a challenge to enhance the efficacy of immunotherapy and the underlying mechanism remains obscure. Thus, the aim of our study is to investigate into the dysfunction of immune cells associated with myelomagenesis and figure out the novel immunotherapeutic targets. Method: Single-cell RNA sequencing was utilized for bone marrow mononuclear cells of 7 healthy donors and 12 newly diagnosed MM patients. We analyze the various immune cell populations and their interaction network with tumor cells of NDMM patients by single-cell RNA sequencing data. Results: Firstly, we found a significant negative correlation between the proportion of T/NK cells and tumor burden. Especially, we observed a decrease of CD8+ effector T cells and skewed accumulation of CD8+ memory T cells in patients with high tumor burden. Further, via calculating the cytotoxicity and exhaustion score of T cells, we demonstrated that the dysfunction of CD8+ effector T cells is mostly related with the impaired cytotoxicity, but not the expression of classical exhausted genes, such as CTLA4, VSIR, LAG3, etc. PIM kinases PIM2/3 and KLRB1 seemed to play critical roles in the dysfunction of CD8+ effector T cells. Referring to NK cells, NK cells displayed similar pattern with effector T cells. NK cells also presented decreased cytotoxicity score in patients with high tumor burden and increased expression of PIM1 and KLRC1, which contributed to immunosuppression. Next, we investigated into myeloid compartment of MM patients. Conventional DC (cDC) cells expressed low level of genes including HLA-B, HLA-C, HLA-DRB1, and HLA-DQA1, etc., indicating the impaired antigen presentation by DCs in high-tumor-burden condition. By cell contact analysis, we evaluated the immune crosstalk among immune cells and tumor cells. We indicated the core role of myeloid cells in MM microenvironment. Consistently, the cellular interaction was active in low-tumor-burden condition, whereas suppressed in high-tumor-burden condition. Finally, we examined the metabolic status of immune cell of MM patients to elucidate the underlying mechanisms of dysfunction of immune cells. Our analysis suggested that aberrant metabolism including amino acid metabolism, lipid metabolism, oxidative phosphorylation caused by MM cells were involved in the defective immune response in MM. Conclusion: Our study delineated the immune profile of bone marrow in MM. We suggested an immunosuppressive microenvironment impacted by high tumor infiltration. The serine/threonine kinase PIM family were involved in the dysfunction of both innate and adaptive immune response. Reprogramming immune metabolism proved to be a hopeful immunotherapeutic strategy.

Immunoregulatory CD71+ Erythroid Cells (CECs) Expand in Multiple Myeloma and Impair Control of L. Monocytogenes Infection

Introduction Although the clinical management of multiple myeloma (MM) patients has significantly improved over recent years, MM remains a largely incurable disease. One of the most common complication of MM, which correlates with the worse clinical outcome, is anemia. Moreover, MM patients are prone to develop life-threatening infections mainly due to the disease-related impairment of the immune system function. Recently, CD71+ erythroid progenitor and precursor cells (CECs) arose as a relevant immunomodulatory population. CECs have been shown to create an immunosuppressive microenvironment via multiple mechanisms including arginase 2 (ARG2), PDL-1, and TGF-beta. It was recently observed in our laboratory that mice bearing late-stage tumors are characterized by the presence of an increased percentage of CECs in their blood and spleens. Moreover, the tumor-associated CECs show elevated levels of arginases. The abovementioned facts may suggest an important role of CECs and their related mechanisms in compromising the immune response in MM. Methods Vk*MYC MM model Recipient C57BL/6 (wild type or ARG2 KO) mice were injected via tail vein with 1 × 106 Vk*MYC cells. M-spike levels were evaluated with serum protein electrophoresis. Five weeks later they were challenged with L. monocytogenes. L.monocytogenes infection and bacterial burden evaluation Mice were injected intraperitoneally with 1 x 103L. monocytogenes cells (strain EGDe). Bacterial burden was analyzed 72h and 7 days post infection. Briefly, spleens and livers of sacrificed mice were isolated, weighed, and homogenized. The homogenates were serially diluted and plated on culture plates. Bacterial burden was calculated using the number of colonies and the dilution factor. Flow cytometry analysis Flow cytometry analyses (immunophenotyping of spleen and bone marrow (BM) cells as well as cytokine beads arrays, Legenplex, BioLegend) were performed using BD Fortessa X-20 flow cytometer operated by BD FACSDiva Software ver. 8.0. The acquired data were re-analyzed using FlowJo™ ver. 10 software. Arginase inhibitor OAT-1746 arginase inhibitor (Molecure SA) was administered intraperitoneally at doses of 5 or 20 mg/kg twice daily, starting from the second or the fifth day before the bacterial challenge, respectively. The treatment was continued until the end of the experiment. Results In Vk*MYC-bearing mice we observed an accumulation of CECs in the blood and spleen in time, correlating with the development of anemia. At the late stage of the disease MM-associated CECs showed less differentiated phenotype and increased expression of arginase-1 (ARG1) and ARG2. MM-associated CECs inhibited T cells activation and proliferation in an ARG and reactive oxygen species-dependent manner. Interestingly, MM development was delayed in ARG2 KO vs WT mice. In the BM aspirates of MM patients we observed increased percentage of CECs expressing high levels of both ARG1 and ARG2 comparing with healthy controls. Moreover, MM impaired control of L. monocytogenes infection as we observed an elevated bacterial burden in the livers and spleens of Vk*MYC-bearing vs control mice. Infected MM-bearing mice had fewer NK cells and activated CD4+ and CD8+ T cells in the spleen than infected control mice. Furthermore, MM altered the dynamics of cytokines involved in the control of intracellular infection. 24h post Listeria challenge we observed their significant decrease followed by an increase at 72h comparing to infected non-MM mice. These results indicate that MM-bearing mice have delayed initial immune response leading to increased bacterial burden followed by excessive cytokines response resulting in sepsis-like condition leading to increased mice mortality. Finally, ARG inhibitor decreased L. monocytogenes burden in MM-bearing mice. Altogether, our results show that accumulation of CECs during MM progression leads to impaired bacterial infection control, at least partially dependent on ARG2 activity. Funding: National Science Centre in Poland [grants No 2017/25/B/NZ6/01139 and 2019/35/B/NZ6/00540]; Polish Ministry of Education and Science [grant No 013/RID/2018/19 (Regional Initiative for Excellence, project budget 12,000,000 PLN)].

Immune checkpoint inhibition improves antimyeloma activity of bortezomib and STING agonist combination in Vk*MYC preclinical model

Multiple myeloma (MM), a hematological malignancy of plasma cells, has remained incurable despite the development of novel therapies that improve patients’ outcome. Recent evidence indicates that the stimulator of interferon genes (STING) pathway may represent a novel target for induction of antitumor immune response in multiple myeloma. Here, we investigated antitumor effects of STING agonist with bortezomib with or without checkpoint inhibitor in the treatment of MM. Methods: STING expression in bone marrow plasma cells of 58 MM patients was examined by immunohistochemical staining. The effectiveness of the proposed therapy was evaluated in vivo in a syngeneic transplantable mouse model of MM (Vĸ*MYC) in immunocompetent mice. Flow cytometry was used to assess tumor burden and investigate activation of immune response against MM. ELISA was performed to measure serum inflammatory cytokines concentrations upon treatment. Results: Combining a STING agonist [2′3′-cGAM(PS)2] with bortezomib significantly decreased tumor burden and improved the survival of treated mice compared to either of the compounds used alone. The combination treatment led to secretion of pro-inflammatory cytokines and increased the percentage of neutrophils, activated dendritic cells and T cells in the tumor microenvironment. However, it resulted also in increased expression of PD-L1 on the surface of the immune cells. Addition of anti-PD1 antibody further potentiated the therapeutic effects. Conclusions: Our findings indicate high antimyeloma efficacy of the three-drug regimen comprising bortezomib, STING agonist, and a checkpoint inhibitor.

High-dimensional single-cell analysis of the immune response in multiple myeloma and profiling of the T cell repertoire in response to immunomodulatory treatment

Abstract Multiple myeloma is a largely incurable malignancy of plasma cells in the bone marrow. The standard of care for this disease has increasingly included the use of immunomodulatory drugs such as thalidomide and its derivatives. However, high-dimensional analysis of the immune response in multiple myeloma tumors and the resultant response to immunomodulatory treatment is lacking. Here, we present a single-cell multi-omic analysis of the immune response in refractory multiple myeloma patient tumors including profiling of CD8+ T cell antigen specificities. We also analyze changes in the T cell repertoire and gene expression following treatment of pomalidomide. We observe a contraction of the repertoire that includes the expansion of select clones within the repertoire. These results provide a clearer map of the immune response in multiple myeloma and how patients respond to immunomodulatory treatment. Supported by grants from CRI Lloyd J. Old STAR Program and NIH R33 IMAT 2018

Targeting LAG3/GAL-3 to overcome immunosuppression and enhance anti-tumor immune responses in multiple myeloma

Immune profiling in patients with monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and multiple myeloma (MM) provides the framework for developing novel immunotherapeutic strategies. Here, we demonstrate decreased CD4+ Th cells, increased Treg and G-type MDSC, and upregulation of immune checkpoints on effector/regulatory and CD138+ cells in MM patients, compared MGUS/SMM patients or healthy individuals. Among the checkpoints profiled, LAG3 was most highly expressed on proliferating CD4+ Th and CD8+ Tc cells in MM patients BMMC and PBMC. Treatment with antibody targeting LAG3 significantly enhanced T cells proliferation and activities against MM. XBP1/CD138/CS1-specific CTL generated in vitro displayed anti-MM activity, which was further enhanced following anti-LAG3 treatment, within the antigen-specific memory T cells. Treg and G-type MDSC weakly express LAG3 and were minimally impacted by anti-LAG3. CD138+ MM cells express GAL-3, a ligand for LAG3, and anti-GAL-3 treatment increased MM-specific responses, as observed for anti-LAG3. Finally, we demonstrate checkpoint inhibitor treatment evokes non-targeted checkpoints as a cause of resistance and propose combination therapeutic strategies to overcome this resistance. These studies identify and validate blockade of LAG3/GAL-3, alone or in combination with immune strategies including XBP1/CD138/CS1 multipeptide vaccination, to enhance anti-tumor responses and improve patient outcome in MM.

Bone marrow-derived mesenchymal stem cells inhibit CD8+ T cell immune responses via PD-1/PD-L1 pathway in multiple myeloma.

High expression of the inhibitory receptor programmed cell death ligand 1 (PD-L1) on tumor cells and tumor stromal cells have been found to play a key role in tumor immune evasion in several human malignancies. However, the expression of PD-L1 on bone marrow mesenchymal stem cells (BMSCs) and whether the programmed cell death 1 (PD-1)/PD-L1 signal pathway is involved in the BMSCs versus T cell immune response in multiple myeloma (MM) remains poorly defined. In this study, we explored the expression of PD-L1 on BMSCs from newly diagnosed MM (NDMM) patients and the role of PD-1/PD-L1 pathway in BMSC-mediated regulation of CD8+ T cells. The data showed that the expression of PD-L1 on BMSCs in NDMM patients was significantly increased compared to that in normal controls (NC) (18·81±1·61 versus 2·78±0·70%; P<0·001). Furthermore, the PD-1 expression on CD8+ T cells with NDMM patients was significantly higher than that in normal controls (43·22±2·98 versus 20·71±1·08%; P<0·001). However, there was no significant difference in PD-1 expression of CD4+ T cells and natural killer (NK) cells between the NDMM and NC groups. Additionally, the co-culture assays revealed that BMSCs significantly suppressed CD8+ T cell function. However, the PD-L1 inhibitor effectively reversed BMSC-mediated suppression in CD8+ T cells. We also found that the combination of PD-L1 inhibitor and pomalidomide can further enhance the killing effect of CD8+ T cells on MM cells. In summary, our findings demonstrated that BMSCs in patients with MM may induce apoptosis of CD8+ T cells through the PD-1/PD-L1 axis and inhibit the release of perforin and granzyme B from CD8+ T cells to promote the immune escape of MM.

Co-evolution of Immune Response in Multiple Myeloma: Implications for Immune Prevention.

Multiple myeloma (MM), a malignant neoplasm of plasma cells that reside in the bone marrow (BM), is universally preceded by a precursor state termed monoclonal gammopathy of undetermined significance (MGUS). Many individuals with MGUS never progress to MM or progress over many years. Therefore, MGUS provides a unique opportunity to surveil changes in the BM tumor microenvironment throughout disease progression. It is increasingly appreciated that MGUS cells carry many of the genetic changes found in MM. Prior studies have also shown that MGUS cells can be recognized by the immune system, leading to early changes in the BM immune environment compared to that of healthy individuals, including alterations in both innate and adaptive immunity. Progression to clinical MM is associated with attrition of T cells with stem memory-like features and instead accumulation of T cells with more terminally differentiated features. Recent clinical studies have suggested that early application of immune-modulatory drugs, which are known to activate both innate and adaptive immunity, can delay the progression to clinical MM. Understanding the biology of how the immune response and tumors coevolve over time is needed to develop novel immune-based approaches to achieve durable and effective prevention of clinical malignancy.

Analysis of Sars-Cov-2-Associated Proteins Identify Tank-Binding Kinase-1 As an Immunotherapeutic Target in Multiple Myeloma

Background and Rationale Patients with multiple myeloma (MM) are at a higher risk of viral infection due to immune deficiency. Importantly, recent studies highlighted the severity of COVID-19 in MM. To date, however, the mechanism(s) underlying the lack of anti-viral immune response in MM are unclear. Plasmacytoid dendritic cells (pDCs) play a key role in both recognition of viral nucleic acid and initiating anti-viral activity via type 1 interferon (IFN) response signaling. We showed that interactions of dysfunctional pDCs with MM cells, T cells, and NK cells confer immune suppression in the host-MM bone marrow (BM) microenvironment (Chauhan et al, Cancer Cell 2009; 16: p309; Ray et al, Leukemia 2015; 29: p1441). Here, we analyzed the immune-pathway proteins implicated in Covid-19-host interactions [Gordon et al, Nature 2020; 583, p459] to assess whether pDC-MM interactions modulate these pathways to confer immune suppression and susceptibility to COVID-19. We identified the TLR pathway serine/threonine kinase TBK1 (TANK-binding kinase 1), involved in type I IFN induction, as a potential immunotherapeutic target in MM. Moreover, Covid-19 relies on host-Ubiquitin-proteasome-system for propagation, and we found that targeting ubiquitin receptor Rpn13 with a specific inhibitor RA190 restores TBK1 expression in MM.Methods For our studies, we examined SARS-CoV-2-human protein-protein interactions (PPIs) maps (Gordon et al, 2020). pDC-MM co-cultures, and RNAseq using next- generation sequencing (NGS): Purified MM patient pDCs were cocultured with autologous MM cells (1pDC/5MM) for 48h, followed by separation of MM cells from pDCs using FACS. Total RNA from MM cells was subjected to RNAseq analysis using Illumina NGS. Raw sequence data were analyzed to generate differential expression (DEseq2). Linear model (Limma) and its GUI (Glimma) were also used. Statistical significance: log2FC (fold change) values in coculture vs control, with a False Discovery Rate value of <0.05, was considered significant (CI > 95). The heatmap analysis was done using Morpheus software (Broad Institute, MIT). MM patient and pDCs data used for bioinformatics were from the NCBI GEO.Results A total of 41 genes involved in the Covid-19 host-pathogen immune interactions are also differentially expressed in MM after coculture with pDCs. (log2Fold change: ± 3.5-fold; p < 0.00001; pDC-MM vs MM alone). The gene expression widely varies in pDC-MM vs MM [Median (log10): -0.13 to 4.5; adj p < 0.001]. We identified 3 specific innate immunity-linked genes TBK1, IRF3 (Interferon regulatory factor 3), and RAE1 (interferon-inducible mRNA nuclear export factor) which are essential for IFN production in MM. Importantly, pDCs decrease TBK1 (Log2FC: -0.5) and RAE1 (Log2FC: -0.3) as well as induce IRF3 (Log2FC: 1.5) in MM (p < 0.0001). Analysis of publicly available gene profiling datasets on relapsed MM patient showed low levels of TBK1 and RAE1 and higher IRF3 (n = 50) [Log2FC: TBK1: -0.208; RAE1: -0.286; IRF3: 0.273; vs normal; p < 0.05). Of note, low TBK1 expression correlates with poor survival in MM patients (n = 350) and elevated TBK1 correlates with a better prognosis (p = 0.026). Similar analysis showed that most of 41 genes involved in the Covid-19 host-pathogen immune interactions are expressed in pDCs. In unstimulated pDCs, TBK1 expression is significantly lower than IRF3 and RAE1 (2-3-fold, p < 0.05). In functional studies, treatment of pDCs with IFN-α activating CpG-ODN type-A increases both TBK1 (adj P = 0.004) and RAE1 (adj P = 0.043), without significantly altering IRF3 expression. Taken together, we show that TBK1 is downregulated in pDCs, and pDCs-MM interactions further decreases TBK1 in MM, thereby attenuating IFN-mediated anti-viral immune response signaling in MM. Finally, we found that blockade of proteasome-mediated protein degradation via inhibition of Ubiquitin receptor Rpn13 upregulates TBK-1 expression, indicating potential clinical use of targeting Rpn13 in restoring anti-viral immune responses in MM.Conclusion We found that pDC-MM interactions downregulate TBK1, which in turn reduces IFN response signaling essential to generate an effective anti-viral immune response in the MM BM microenvironment. Our findings suggest that: 1) low levels of TBK1 may confer increased susceptibility of MM patients to COVID-19; and 2) targeting TBK1 may restore anti-viral immune response and reduce COVID-19 severity in MM.DisclosuresChauhan:consultant to Stemline Therapeutics, Inc., and Equity owner in C4 Therapeutics.: Consultancy, Other: Equity owner in C4 Therapeutics.; Oncopeptide AB: Consultancy. Anderson:Janssen: Membership on an entity's Board of Directors or advisory committees; Millenium-Takeda: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Oncopep and C4 Therapeutics.: Other: Scientific Founder of Oncopep and C4 Therapeutics.; Sanofi-Aventis: Membership on an entity's Board of Directors or advisory committees.

Bone Marrow-Derived Mesenchymal Stem Cells Inhibit CD8+ t Cell Immune Responses Via PD-1/PD-L1 Pathway in Multiple Myeloma

High expression of the inhibitory receptor programmed death ligand 1 (PD-L1) on tumor cells and tumor stromal cells have been found play a key role in tumor immune evasion in several human malignancies. However, the expression of PD-L1 on bone marrow mesenchymal stem cells (BMSCs) and whether the PD-1/PD-L1 signal pathway is involved in the BMSCs versus T cell immune response in Multiple Myeloma (MM) remain poorly defined. In this study, we explored the expression of PD-L1 on BMSCs from newly diagnosed MM (NDMM) patients and the role of PD-1/PD-L1 pathway in BMSCs-mediated regulation of CD8+T cells. The data showed that the expression of PD-L1 on BMSCs in NDMM patients was significantly increased than that in normal controls (NC) (18.81±1.61% vs. 2.78±0.70 %; P&amp;lt;0.001). Furthermore, the PD-1 expression on CD8+T cells with NDMM patients was significantly higher than that in normal controls (43.22±2.98% vs. 20.71±1.08%; P&amp;lt;0.001). However, there was no significant difference in PD-1 expression of CD4+ T cells and NK cells between NDMM group and NC group. Additionally, the co-culture assays revealed that BMSCs significantly promoted CD8+ T cells apoptosis and suppressed CD8+ T cells function. However, PD-L1 inhibitor effectively reversed BMSCs-mediated suppression in CD8+ T cells. We also found that the combination of PD-L1 inhibitor and pomalidomide can further enhance the killing effect of CD8+ T cells on MM cells. In summary, our findings demonstrated that BMSCs in patients with MM may induce apoptosis of CD8+T cells through the PD-1/PD-L1 axis and inhibit the release of perforin and granzyme B from CD8+ T cells so as to promote the immune escape of MM. Disclosures No relevant conflicts of interest to declare.

Blockade of Deubiquitylating Enzyme USP7 in Plasmacytoid Dendritic Cells Stimulates Anti-Myeloma Immunity

Introduction Proteasome inhibitors (PIs) are a backbone standard of care in the treatment of relapsed/refractory and newly diagnosed multiple myeloma (MM). Although PIs represent a major advance, not all MM responds, and relapse develops due to the development of drug-resistance. Besides the 26S proteasome, the ubiquitin proteasome pathway harbors many other sites for therapeutic intervention, with the potential to overcome PI-resistance. We showed that inhibition of deubiquitylating enzyme USP7, upstream of the 20S proteasome, induces cell death even in MM cells resistant to PI therapies. To date, however, the effect of USP7 inhibition on the immunosuppressive and tumor-promoting MM-host bone marrow (BM) accessory cells such as plasmacytoid dendritic cells (pDC) remains unclear. Here, we utilized our co-culture models of pDCs, T cells, and NK cells with autologous patient MM cells to examine whether USP7 inhibition also stimulates anti-MM immunity. Methods MM cell lines were validated by fingerprinting, and MM patient BM/PB samples (n = 9) were obtained after informed consent. We used minimally cytotoxic concentrations of a novel USP7 inhibitor XL177A (0.1-0.5 µM). Activation/maturation assays MM-pDCs were treated with XL177A (0.2 uM; 24h), followed by evaluation of CD86/HLA-DR markers by FACS. USP7-HA-UbVME Labeling: pDC representative Cal-1 cells were treated with DMSO or XL177A for 6h; proteins were labeled with ubiquitin (Ub) active site probe Ub-vinyl methyl ester (HAUbVME) for 30 mins, followed by immunoblot analysis using anti-USP7 antibodies. CTL/NK activity assays MM CD8+ T- or NK-cells cells were cultured with autologous pDCs (1:10 pDC:T/NK ratio) with XL177A for 3 days; after washing to remove drug, cells were cultured with pre-stained (CellTrace Violet) target MM cells (10:1 E/T ratio; T/NK:MM) for 24h, followed by FACS quantification of viable MM cells. Statistical parameters were calculated using GraphPad Prism. Results 1) Treatment of MM cell lines and patient MM cells with XL177A for 24h significantly decreases their viability (IC50 range 0.6 uM to 5 uM) (mean ± SD; p &amp;lt; 0.05; n=4). 2) Blockade of USP7 by XL177A activates MM patient BM-pDCs, evidenced by an increase in pDC maturation markers CD86 and HLA-DR. As a negative control, treatment of pDCs with XL177B, an inactive (R) enantiomer of XL177A, had no effect on CD86 or HLA-DR expression on pDCs. 3) XL177A specificity against USP7 DUB activity was assessed using competition assays between XL177A and Ub-active site labeling probe HAUbVME: treatment of pDC-Cal-1 cells with XL177A blocked the labeling HAUbME probe, confirming its specificity. Similar results were noted using another USP7 inhibitor P5091. 4) Functional studies showed that XL177A stimulates MM-specific CD8+ CTL activity, evidenced by a decrease in the viability of patient MM cells (p = 0.0004; n= 9). 5) XL177A triggered pDC-induced NK cell-mediated MM-specific cytolytic activity (p&amp;lt;0.05). Finally, 6) XL177A decreased Treg (CD4+/CD25+/Foxp3+) populations in MM. Conclusion Targeting USP7 DUB enzyme restores both innate and adaptive immune responses in MM. These findings, coupled with our prior findings showing that inhibition of USP7 overcomes PI-resistance in MM cells, suggest that targeting USP7 is a novel therapeutic strategy to overcome both PI-resistance and immune suppression in MM. Disclosures Buhrlage: Adenoid Cystic Carcinoma Foundation: Other: Scientific Advisory Board. Chauhan:consultant to Stemline Therapeutics, Inc., and Equity owner in C4 Therapeutics.: Consultancy, Other: Equity owner in C4 Therapeutics.; Oncopeptide AB: Consultancy. Anderson:Sanofi-Aventis: Membership on an entity's Board of Directors or advisory committees; Oncopep and C4 Therapeutics.: Other: Scientific Founder of Oncopep and C4 Therapeutics.; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millenium-Takeda: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees.

Inverse relationship between oligoclonal expanded CD69− TTE and CD69+ TTE cells in bone marrow of multiple myeloma patients

AbstractCD8+CD57+ terminal effector T (TTE) cells are a component of marrow-infiltrating lymphocytes and may contribute to the altered immune responses in multiple myeloma (MM) patients. We analyzed TTE cells in the bone marrow (BM) and peripheral blood (PB) of age-matched controls and patients with monoclonal gammopathy of undetermined significance (MGUS), smoldering MM (SMM), and newly diagnosed (ND) MM using flow cytometry, mass cytometry, and FlowSOM clustering. TTE cells are heterogeneous in all subjects, with BM containing both CD69− and CD69+ subsets, while only CD69− cells are found in PB. Within the BM-TTE compartment, CD69− and CD69+ cells are found in comparable proportions in controls, while CD69− cells are dominant in MGUS and SMM and predominantly either CD69− or CD69+ cells in NDMM. A positive relationship between CD69+TTE and CD69−TTE cells is observed in the BM of controls, lost in MGUS, and converted to an inverse relationship in NDMM. CD69−TTE cells include multiple oligoclonal expansions of T-cell receptor/Vβ families shared between BM and PB of NDMM. Oligoclonal expanded CD69−TTE cells from the PB include myeloma-reactive cells capable of killing autologous CD38hi plasma cells in vitro, involving degranulation and high expression of perforin and granzyme. In contrast to CD69−TTE cells, oligoclonal expansions are not evident within CD69+TTE cells, which possess low perforin and granzyme expression and high inhibitory checkpoint expression and resemble T resident memory cells. Both CD69−TTE and CD69+TTE cells from the BM of NDMM produce large amounts of the inflammatory cytokines interferon-γ and tumor necrosis factor α. The balance between CD69− and CD69+ cells within the BM-TTE compartment may regulate immune responses in NDMM and contribute to the clinical heterogeneity of the disease.

Deregulation of Adaptive T Cell Immunity in Multiple Myeloma: Insights Into Mechanisms and Therapeutic Opportunities.

Immunotherapy has recently emerged as a promising treatment option for multiple myeloma (MM) patients. Profound immune dysfunction and evasion of immune surveillance are known to characterize MM evolution and disease progression. Along with genomic changes observed in malignant plasma cells, the bone marrow (BM) milieu creates a protective environment sustained by the complex interaction of BM stromal cells (BMSCs) and malignant cells that using bidirectional connections and cytokines released stimulate disease progression, drug resistance and enable immune escape. Local immune suppression and T-cell exhaustion are important mediating factors of clinical outcomes and responses to immune-based approaches. Thus, further characterization of the defects present in the immune system of MM patients is essential to develop novel therapies and to repurpose the existing ones. This review seeks to provide insights into the mechanisms that promote tumor escape, cause inadequate T-cell stimulation and impaired cytotoxicity in MM. Furthermore, it highlights current immunotherapies being used to restore adaptive T-cell immune responses in MM and describes strategies created to escape these multiple immune evasion mechanisms.

Targeting tryptophan catabolic kynurenine pathway enhances antitumor immunity and cytotoxicity in multiple myeloma.

Our prior studies showed that dysfunctional plasmacytoid dendritic cells (pDCs) contribute to multiple myeloma (MM) pathogenesis. Specifically, pDC interactions with tumor and T/NK effector cells in the bone marrow (BM) milieu induce immune suppression and MM cell proliferation. Delineation of the mechanism(s) mediating pDC-MM-T-NK cell interactions will identify novel therapeutic targets to both enhance cytotoxicity and anti-MM immunity. Here, we utilized gene expression profiling (GEP) to show that pDC-MM interactions trigger upregulation of immunosuppressive tryptophan catabolic kynurenine (Kyn) pathway. In particular, we show that Kyn pathway enzyme kynurenine-3-monooxygenase (KMO) is upregulated during pDC-MM interactions. Using our coculture models of patient autologous pDC-T-NK-MM cells, we show that pharmacological blockade of KMO activates pDCs and triggers both MM-specific cytotoxic T-cell lymphocytes (CTL) and NK cells cytolytic activity against tumor cells. Furthermore, we show that simultaneous inhibition of Kyn pathway and immune checkpoint PD-L1 enhances antitumor immunity and cytotoxicity in MM. Our preclinical data therefore provide the basis for novel immune-based therapeutic approaches targeting Kyn metabolic pathway enzyme KMO, alone or in combination with anti-PD-L1 Ab, to restore anti-MM immune responses in MM.

Immune responses in multiple myeloma: role of the natural immune surveillance and potential of immunotherapies.

Multiple myeloma (MM) is a tumor of terminally differentiated B cells that arises in the bone marrow. Immune interactions appear as key determinants of MM progression. While myeloid cells foster myeloma-promoting inflammation, Natural Killer cells and T lymphocytes mediate protective anti-myeloma responses. The profound immune deregulation occurring in MM patients may be involved in the transition from a premalignant to a malignant stage of the disease. In the last decades, the advent of stem cell transplantation and new therapeutic agents including proteasome inhibitors and immunoregulatory drugs has dramatically improved patient outcomes, suggesting potentially key roles for innate and adaptive immunity in disease control. Nevertheless, MM remains largely incurable for the vast majority of patients. A better understanding of the complex interplay between myeloma cells and their immune environment should pave the way for designing better immunotherapies with the potential of very long term disease control. Here, we review the immunological microenvironment in myeloma. We discuss the role of naturally arising anti-myeloma immune responses and their potential corruption in MM patients. Finally, we detail the numerous promising immune-targeting strategies approved or in clinical trials for the treatment of MM.

Lenalidomide Enhances Immune Checkpoint Blockade-Induced Immune Response in Multiple Myeloma.

PD-1/PD-L1 signaling promotes tumor growth while inhibiting effector cell-mediated antitumor immune responses. Here, we assessed the impact of single and dual blockade of PD-1/PD-L1, alone or in combination with lenalidomide, on accessory and immune cell function as well as multiple myeloma cell growth in the bone marrow (BM) milieu. Surface expression of PD-1 on immune effector cells, and PD-L1 expression on CD138(+) multiple myeloma cells and myeloid-derived suppressor cells (MDSC) were determined in BM from newly diagnosed (ND) multiple myeloma and relapsed/refractory (RR) multiple myeloma versus healthy donor (HD). We defined the impact of single and dual blockade of PD-1/PD-L1, alone and with lenalidomide, on autologous anti-multiple myeloma immune response and tumor cell growth. Both ND and RR patient multiple myeloma cells have increased PD-L1 mRNA and surface expression compared with HD. There is also a significant increase in PD-1 expression on effector cells in multiple myeloma. Importantly, PD-1/PD-L1 blockade abrogates BM stromal cell (BMSC)-induced multiple myeloma growth, and combined blockade of PD-1/PD-L1 with lenalidomide further inhibits BMSC-induced tumor growth. These effects are associated with induction of intracellular expression of IFNγ and granzyme B in effector cells. Importantly, PD-L1 expression in multiple myeloma is higher on MDSC than on antigen-presenting cells, and PD-1/PD-L1 blockade inhibits MDSC-mediated multiple myeloma growth. Finally, lenalidomide with PD-1/PD-L1 blockade inhibits MDSC-mediated immune suppression. Our data therefore demonstrate that checkpoint signaling plays an important role in providing the tumor-promoting, immune-suppressive microenvironment in multiple myeloma, and that PD-1/PD-L1 blockade induces anti-multiple myeloma immune response that can be enhanced by lenalidomide, providing the framework for clinical evaluation of combination therapy.

Epigenetic induction of adaptive immune response in multiple myeloma: sequential azacitidine and lenalidomide generate cancer testis antigen‐specific cellular immunity

Patients with multiple myeloma (MM) undergoing high dose therapy and autologous stem cell transplantation (SCT) remain at risk for disease progression. Induction of the expression of highly immunogenic cancer testis antigens (CTA) in malignant plasma cells in MM patients may trigger a protective immune response following SCT. We initiated a phase II clinical trial of the DNA hypomethylating agent, azacitidine (Aza) administered sequentially with lenalidomide (Rev) in patients with MM. Three cycles of Aza and Rev were administered and autologous lymphocytes were collected following the 2nd and 3rd cycles of Aza-Rev and cryopreserved. Subsequent stem cell mobilization was followed by high-dose melphalan and SCT. Autologous lymphocyte infusion (ALI) was performed in the second month following transplantation. Fourteen patients have completed the investigational therapy; autologous lymphocytes were collected from all of the patients. Thirteen patients have successfully completed SCT and 11 have undergone ALI. Six patients tested have demonstrated CTA up-regulation in either unfractionated bone marrow (n = 4) or CD138+ cells (n = 2). CTA (CTAG1B)-specific T cell response has been observed in all three patients tested and persists following SCT. Epigenetic induction of an adaptive immune response to cancer testis antigens is safe and feasible in MM patients undergoing SCT.

Development of Novel CD138 Antigen-Specific Peptide Capable of Eliciting Myeloma-Specific Cytotoxic T Lymphocytes Response.

Multiple myeloma (MM) is characterized by the accumulation of mature plasma cells in the bone marrow. Despite progress in treatment, the disease still remains incurable, therefore novel therapeutic approaches are required to achieve better treatment. Development of peptide-based immunotherapies against specific tumor-associated antigens offers an attractive approach that may lead to tumor-targeted cellular therapy in MM patients. CD138 (Syndecan-1) is an unique target expressed on the surface of MM cells and normal plasma cells with very limited other distribution or expression. CD138 has been reported to play an important role in myeloma cell survival and, infact, is used to purify MM cells in laboratory experiments. The purpose of this study was to develop immunogenic peptides derived from CD138 antigen for the induction of antigen-specific cytotoxic T lymphocytes (CTLs) against MM. We have identified an immunogeneic HLA-A2-specific CD138 peptide that is capable of inducing MM specific-CTLs. To induce the specific CTLs, HLA-A2-positive normal human T lymphocytes were stimulated with autologous dendritic cells or T2 cells pulsed with the CD138 peptide. The generated CTLs showed a distinct phenotype consisting of 67% of CD69+/CD45RO+ and 1% of CD45RA+/CCR7+ T cells, characteristic of effector memory cell population. A significant (p < 0.05) increase in T cell proliferation and IFN-g secretion were observed by the CTLs following restimulation with HLA-A2+/CD138+ MM cells. The CTLs displayed HLA-A2-restricted CD138-specific cytotoxic activity against MM cell, demonstrated as 76% and 86% cytotoxicity at Effector:Target ratios of 20:1 or 60:1, respectively. The MM cell-specific cytotoxicity was confirmed in “cold” target inhibition assays using HLA-A2.1+/CD138+ MM cells as “cold” inhibitor, demonstrated 25% and 39% reduction in cytotoxicity when incubated with cold inhibitors at E:T ratios of 20:1 or 60:1, respectively. A distinct CD138 peptide-specific tetramer+/CD8+ population was also confirmed. Taken together, these data demonstrate the efficacy of the immunogenic CD138 peptide in inducing a cellular immune response in MM for future clinical application.

Effects of Interferon-α-2a on Th3 Cytokine Response in Multiple Myeloma Patients

Multiple myeloma cells increase Th3 cytokine response by secreting TGF-beta, which causes defective Th1 and Th2 cytokine responses. Therefore, a significant suppression of the immune system is seen in multiple myeloma. Interferon-alpha (IFN-alpha) is used in the treatment of multiple myeloma due to its immunomodulatory and anti-tumoral effects. We attempted to define the characteristics of immune cytokine responses and the effects of IFN-alpha-2a on the immune response in multiple myeloma. Fifteen patients with multiple myeloma and 15 healthy controls were enrolled. IFN-alpha-2a, 3 million units/day x 3 times/week, was administered subcutaneously to the patients for 2 weeks. Cytokines (TGF-beta, IL-1, IL-2, IL-4, IL-10, IFN-gamma) were assessed by the ELISA method in sera of the patients in pretreatment and posttreatment periods and in the sera of the controls. IL-2 and IL-4 levels in patients, before IFN-alpha-2a, were lower than the controls, whereas TGF-beta levels were higher than the controls. In other words, Th3 cytokine response was increased and Th1 and Th2 cytokine responses were decreased in patients. A short course of IFN-alpha-2a increased IL-2 levels. These findings suggest IFN-alpha-2a may enhance nonTh3 cytokine responses in multiple myeloma patients.