BackgroundMultiple myeloma (MM) is the second most common hematologic malignancy. Aberrant epigenetic modifications have been reported in MM and could be promising therapeutic targets. As response rates are overall limited but deep responses occur, it is important to identify those patients who could indeed benefit from epigenetic-targeted therapy.MethodsSince HDACi and DNMTi combination have potential therapeutic value in MM, we aimed to build a GEP-based score that could be useful to design future epigenetic-targeted combination trials. In addition, we investigated the changes in GEP upon HDACi/DNMTi treatment.ResultsWe report a new gene expression-based score to predict MM cell sensitivity to the combination of DNMTi/HDACi. A high Combo score in MM patients identified a group with a worse overall survival but a higher sensitivity of their MM cells to DNMTi/HDACi therapy compared to a low Combo score. In addition, treatment with DNMTi/HDACi downregulated IRF4 and MYC expression and appeared to induce a mature BMPC plasma cell gene expression profile in myeloma cell lines.ConclusionIn conclusion, we developed a score for the prediction of primary MM cell sensitivity to DNMTi/HDACi and found that this combination could be beneficial in high-risk patients by targeting proliferation and inducing maturation.

Multiple myeloma (MM) is a B cell neoplasia characterized by clonal plasma cell (PC) proliferation. Minimal residual disease monitoring by multi-parameter flow cytometry is a powerful tool for predicting treatment efficacy and MM outcome.In this study, we compared CD antigens expression between normal and malignant plasma cells to identify new potential markers to discriminate normal from malignant plasma cells, new potential therapeutic targets for monoclonal-based treatments and new prognostic factors. Nine genes were significantly overexpressed and 16 were significantly downregulated in MMC compared with BMPC (ratio ≥2; FDR CD24, CD27, CD36 and CD302) was associated with a prognostic value in two independent cohorts of patients with MM (HM cohort and TT2 cohort, n=345). The expression level of these four genes was then used to develop a CD gene risk score that classified patients in two groups with different survival (P = 2.06E-6) in the HM training cohort. The prognostic value of the CD gene risk score was validated in two independent cohorts of patients with MM (TT2 cohort and HOVON65/GMMGHD4 cohort, n=282 patients). The CD gene risk score remained a prognostic factor that separated patients in two groups with significantly different overall survival also when using publicly available data from a cohort of relapsing patients treated with bortezomib (n=188). In conclusion, the CD gene risk score allows identifying high risk patients with MM based on CD24, CD27, CD36 and CD302 expression and could represent a powerful tool for simple outcome prediction in MM.

Multiple Myeloma (MM) is an incurable malignant plasma cell disorder. We have evaluated the counts of Multiple Myeloma Cells (MMCs) and normal plasma cells (N-PCs), seven days after high-dose melphalan (HDM) and autologous stem transplantation (ASCT). Two third of patients had detectable minimal residual disease (MRD+) (71.7 MMCs/μL) after induction treatment with dexamethasone and proteasome inhibitor. MMC counts were reduced by 92% (P ≤ .05) but not eradicated 7 days after HDM+ASCT. Post-HDM+ASCT MMCs were viable and bathed in a burst of MMC growth factors, linked with post-HDM aplasia. In one third of patients (MRD− patients), MMCs were not detectable after induction treatment and remained undetectable after HDM+ASCT. Major difference between MRD− and MRD+ patients is that N-PC counts were increased 3 fold (P < .05) by HDM+ASCT in MRD− patients, but were unaffected in MRD+ patients. Possible explanation could be that clearance of MMCs in MRD− patients makes more niches available for N-PCs. Thus, MMCs are not fully eradicated shortly after HDM, are bathed in high concentrations of MMC growth factors in an almost desert BM, are viable in short-term culture, which suggests providing additional therapies shortly after HDM to kill resistant MMCs before full repair of lesions.

131 Background and Objectives: Multiple myeloma (MM) is still an incurable plasma cell dyscrasia. In an attempt to further improve MM patients' outcome, we have characterized malignant plasma cells resistant to treatments as well as their cellular and molecular environment. The aim is to highlight interactions that could be targeted at optimal time points of the treatment schedule. Methods: Twenty-four newly diagnosed MM patients treated in first line by bortezomib and dexamethasone induction followed by high dose melphalan (HDM) and autologous stem cell transplantation were included. Tumor and normal plasma cell were detected and counted in peripheral blood and bone marrow using 7-color multiparameter flow cytometry at different time points of treatment: at the end of induction, 9 days, 3 months and 6 months after high dose melphalan and autologous stem cell reinjection. The sensitivity of detection reached was 10−5. The cellular content of the leukapheresis product was also analyzed after thawing before being reinjected. Plasma cells were characterized in terms of tumor markers (CD200, CD56, CD117, CD27, CD19, CD45), proliferation status (KI67) and expression of CCR2 chemokine receptor. Using multiplex technique, we also evaluated the medullary cytokine / chemokine environment (Interleukin-1b (IL-1b), IL-1RA, IL-2, IL-2R, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, Epidermal Growth Factor (EGF), eotaxin, Fibroblast Growth Factor-basic (FGF-b), Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF), G-CSF, Hepatocyte Growth Factor (HGF), Interferon-a (IFN-a), IFN-g, Inducible Protein 10 (IP-10, CXCL10), Monocyte Chemotactic Protein-1 (MCP-1, CCL2), Monokine Induced by IFN-g, Regulated on Activation Normally T-cell Expressed and Secreted (RANTES, CCL5), Tumor Necrosis Factor a (TNF- a), and Vascular Endothelial Growth Factor (VEGF) at the end of induction, 9 days and 3 months post HDM. IGF1, IL21, BAFF and APRIL were measured by Elisa. Results: Two thirds of the 24 patients had detectable tumor plasma cells after induction treatment and in all these patients, tumor plasma cells (median 5.9 cells/ mm3, range 0.1–76.9 cells/mm3) as well as normal plasma cells (median 3.3 cells/mm3, range 0.4–32.2 cells/mm3) could be detected 9 days after HDM treatment in an aplastic bone marrow (median cell count 400 cells/mm3). Nine days post HDM, a burst of cytokines / chemokines was detected in bone marrow plasma which could prompt survival, growth and homing of tumor plasma cells. CCL2 chemokine (chemokine C-C motif ligand 2) which is a chemotactant and survival factor for myeloma cells was the only cytokine / chemokine differentially expressed in immuno-phenotypic complete response patients compared to patients with persistent tumor plasma cells, with a concentration 2.1 times higher in the last ones. In parallel, preliminary data show an enrichment in CCR2 positive tumor plasma cells 9 days after HDM, CCR2 being the receptor for CCL2. This interaction could be a clinically significant target to get rid of minimal residual disease. Conclusions: In conclusion, we show that the early post intensification (HDM) period could be an interesting therapeutic window to target resistant myeloma cells and their interactions with the pro-survival micro-environment. The CCL2-CCR2 interaction could be of particular interest, an anti CCR2 antibody already being in clinical development in rheumatoid arthritis (Van Driel et al. 2008). Disclosures: No relevant conflicts of interest to declare.