BackgroundPD1/PDL1-directed therapies have been unsuccessful for multiple myeloma (MM), an incurable cancer of plasma cells in the bone marrow (BM). Therefore, other immune checkpoints such as extracellular adenosine and its immunosuppressive receptor should be considered. CD39 and CD73 convert extracellular ATP to adenosine, which inhibits T-cell effector functions via the adenosine receptor A2A (A2AR). We set out to investigate whether blocking the adenosine pathway could be a therapy for MM.MethodsExpression of CD39 and CD73 on BM cells from patients and T-cell proliferation were determined by flow cytometry and adenosine production by Liquid chromatograpy-mass spectrometry (HPCL/MS). ENTPD1 (CD39) mRNA expression was determined on myeloma cells from patients enrolled in the publicly available CoMMpass study. Transplantable 5T33MM myeloma cells were used to determine the effect of inhibiting CD39, CD73 and A2AR in mice in vivo.ResultsElevated level of adenosine was found in BM plasma of MM patients. Myeloma cells from patients expressed CD39, and high gene expression indicated reduced survival. CD73 was found on leukocytes and stromal cells in the BM. A CD39 inhibitor, POM-1, and an anti-CD73 antibody inhibited adenosine production and reduced T-cell suppression in vitro in coculture of myeloma and stromal cells. Blocking the adenosine pathway in vivo with a combination of Sodium polyoxotungstate (POM-1), anti-CD73, and the A2AR antagonist AZD4635 activated immune cells, increased interferon gamma production, and reduced the tumor load in a murine model of MM.ConclusionsOur data suggest that the adenosine pathway can be successfully targeted in MM and blocking this pathway could be an alternative to PD1/PDL1 inhibition for MM and other hematological cancers. Inhibitors of the adenosine pathway are available. Some are in clinical trials and they could thus reach MM patients fairly rapidly.

Multiple myeloma (myeloma in short) is an incurable cancer of antibody-producing plasma cells that comprise 13% of all hematological malignancies. The proteasome inhibitor bortezomib has improved treatment significantly, but inherent and acquired resistance to the drug remains a problem. We here show that bortezomib-induced cytotoxicity was completely dampened when cells were supplemented with cysteine or its derivative, glutathione (GSH) in ANBL-6 and INA-6 myeloma cell lines. GSH is a major component of the antioxidative defense in eukaryotic cells. Increasing intracellular GSH levels fully abolished bortezomib-induced cytotoxicity and transcriptional changes. Elevated intracellular GSH levels blocked bortezomib-induced nuclear factor erythroid 2-related factor 2 (NFE2L2, NRF2)-associated stress responses, including upregulation of the xCT subunit of the Xc- cystine-glutamate antiporter. INA-6 cells conditioned to increasing bortezomib doses displayed reduced bortezomib sensitivity and elevated xCT levels. Inhibiting Xc- activity potentiated bortezomib-induced cytotoxicity in myeloma cell lines and primary cells, and re-established sensitivity to bortezomib in bortezomib-conditioned cells. We propose that intracellular GSH level is the main determinant of bortezomib-induced cytotoxicity in a subset of myeloma cells, and that combined targeting of the proteasome and the Xc- cystine-glutamate antiporter can circumvent bortezomib resistance.

BackgroundMultiple myeloma is an incurable complex disease characterized by clonal proliferation of malignant plasma cells in a hypoxic bone marrow environment. Hypoxia-dependent erythropoietin (EPO)-receptor (EPOR) signaling is central in various cancers, but the relevance of EPOR signaling in multiple myeloma cells has not yet been thoroughly investigated.MethodsMyeloma cell lines and malignant plasma cells isolated from bone marrow of myeloma patients were used in this study. Transcript levels were analysed by quantitative PCR and cell surface levels of EPOR in primary cells by flow cytometry. Knockdown of EPOR by short interfering RNA was used to show specific EPOR signaling in the myeloma cell line INA-6. Flow cytometry was used to assess viability in primary cells treated with EPO in the presence and absence of neutralizing anti-EPOR antibodies. Gene expression data for total therapy 2 (TT2), total therapy 3A (TT3A) trials and APEX 039 and 040 were retrieved from NIH GEO omnibus and EBI ArrayExpress.ResultsWe show that the EPOR is expressed in myeloma cell lines and in primary myeloma cells both at the mRNA and protein level. Exposure to recombinant human EPO (rhEPO) reduced viability of INA-6 myeloma cell line and of primary myeloma cells. This effect could be partially reversed by neutralizing antibodies against EPOR. In INA-6 cells and primary myeloma cells, janus kinase 2 (JAK-2) and extracellular signal regulated kinase 1 and 2 (ERK-1/2) were phosphorylated by rhEPO treatment. Knockdown of EPOR expression in INA-6 cells reduced rhEPO-induced phospo-JAK-2 and phospho-ERK-1/2. Co-cultures of primary myeloma cells with bone marrow-derived stroma cells did not protect the myeloma cells from rhEPO-induced cell death. In four different clinical trials, survival data linked to gene expression analysis indicated that high levels of EPOR mRNA were associated with better survival.ConclusionsOur results demonstrate for the first time active EPOR signaling in malignant plasma cells. EPO-mediated EPOR signaling reduced the viability of myeloma cell lines and of malignant primary plasma cells in vitro. Our results encourage further studies to investigate the importance of EPO/EPOR in multiple myeloma progression and treatment.Trial registration[Trial registration number for Total Therapy (TT) 2: NCT00083551 and TT3: NCT00081939].

The fast-moving field of dendritic cell (DC) biology is hard to keep pace with. Here we report on advances from the recent Keystone Symposium, “Dendritic Cells at the Center of Innate and Adaptive Immunity,” organized in Vancouver, BC on Feb. 1–7, 2005 by Anne O'Garra, Jacques Banchereau, and Alan Sher. New insights into the molecular mechanisms of DC function and their influence on immune regulation, their role in infectious and autoimmune disease, and new clinical applications are highlighted.

In this review article we discuss the role of the memory T cells in multiple myeloma (MM) and how they may influence immune responses in patients that received immunomodulating drugs and check point therapy.

Multiple Myeloma is a cancer of the plasma cells in the bone marrow. Despite from the fact that new drugs have increased survival in the past decade, it is still an incurable cancer. It is therefore important to develop new drugs. Tumor immunosurveillance contributes to the control of cancer growth, but there many different escape mechanisms utilized by tumour to evade anti-tumour immune responses. One of the largely unexplored mechanisms of immune suppression in multiple myeloma is the role of adenosine in the bone marrow microenvironment, which now represents an attractive new therapeutic target for cancer therapy. 2 ectoenzymes, CD39 and CD73 are important for converting extracellular ATP to adenosine. When investigating the role of adenosine in the immune response to multiple myeloma, we found increased concentration of adenosine in the bone marrow plasma from myeloma patients compared with healthy controls. CD39 (ENTPD1) was expressed by myeloma cell lines and on myeloma cells from patients. CD73 was found on leukocytes and stromal cells in the bone marrow. Although very few cells expressed CD73 in the bone marrow, these cells could clearly convert AMP to adenosine. ATP was converted to AMP by CD39+ myeloma cell lines, and CD73+ stromal cells converted AMP to adenosine. Importantly, co-culture of CD39+ myeloma cells and CD73+ stromal cells catalyzed extracellular ATP to immunosuppressive adenosine. Indeed, we found that CD3 T cells stimulated with anti CD3/CD28 beads in the presence of supernatants from co-cultured cells did not proliferate as well as T cell culture without this supernatant. The fact that this proliferation was inhibited by the ZM241385 inhibitor, suggested that the suppression was mediated by the A2AR receptor. The CD39 inhibitor POM1 inhibited adenosine generation in the co-culture system as well as T cell proliferation in vitro. We have recently obtained the CD73 antibody MEDI199447 from MedImmune and are testing the ability of this antibody to prevent adenosine production and T cell proliferation in vitro, as well as the ability to reduce tumor growth in a mouse model of multiple myeloma. The clinical importance of the adenosine pathway in multiple myeloma found when analyzing patient data. Using the publicly available coMMpass database, we found that patients with high expression of CD39 had significantly reduced progression free and overall survival. Citation Format: Rui Yang, Samah Elsaadi, Kristine Misund, Geir Slupphaug, Eline Menu, Carl Hay, Zac Cooper, Karin Vanderkerken, Magne Børset, Anne Marit Sponaas. Role of ectoenzymes CD39 and CD73 in the immune response to multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-117.

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