Géraldine Descamps

A high-risk signature for patients with multiple myeloma established from the molecular classification of human myeloma cell lines

Background Multiple myeloma is a plasma-cell tumor with heterogeneity in molecular abnormalities and treatment response. Design and Methods We have assessed whether human myeloma cell lines have kept patients’ heterogeneity using Affymetrix gene expression profiling of 40 human myeloma cell lines obtained with or without IL6 addition and could provide a signature for stratification of patient risk. Results Human myeloma cell lines, especially those derived in the presence of IL6, displayed a heterogeneity that overlaps that of the patients with multiple myeloma. Human myeloma cell lines segregated into 6 groups marked by overexpression of MAF, MMSET, CCND1, FRZB with or without overexpression of cancer testis antigens (CTA). Cell lines of CTA/MAF and MAF groups have a translocation involving C-MAF or MAFB, cell lines of groups CCND1-1 and CCND1-2like have a t(11;14) and cell lines of group MMSET have a t(4;14). The CTA/FRZB group comprises cell lines that had no or no recurrent 14q32 translocation. Expression of 248 genes accounted for human myeloma cell line molecular heterogeneity. Human myeloma cell line heterogeneity genes comprise genes with prognostic value for survival of patients making it possible to build a powerful prognostic score involving a total of 13 genes. Conclusions Human myeloma cell lines derived in the presence of IL6 recapitulate the molecular diversity of multiple myeloma that made it possible to design, using human myeloma cell line heterogeneity genes, a high-risk signature for patients at diagnosis. We propose this classification to be used when addressing the physiopathology of multiple myeloma with human myeloma cell lines.

ABT-737 is highly effective against molecular subgroups of multiple myeloma.

Multiple myeloma is a plasma cell malignancy that is heterogeneous with respect to its causative molecular abnormalities and the treatment response of patients. The Bcl-2 protein family is critical for myeloma cell survival. ABT-737 is a cell-permeant compound that binds to Bcl-2 and Bcl-x(L) but not to Mcl-1. Using a myeloma cell line collection (n = 25) representative of different molecular translocations, we showed that ABT-737 effectively kills a subset of cell lines (n = 6), with a median lethal dose ranging from 7 ± 0.4 nM to 150 ± 7.5 nM. Of interest, all sensitive cell lines harbored a t(11;14). We demonstrated that ABT-737-sensitive and ABT-737-resistant cell lines could be differentiated by the BCL2/MCL1 expression ratio. A screen of a public expression database of myeloma patients indicates that the BCL2/MCL1 ratio of t(11;14) and hyperdiploid patients was significantly higher than in all other groups (P < .001). ABT-737 first induced the disruption of Bcl-2/Bax, Bcl-2/Bik, or Bcl-2/Puma complexes, followed by the disruption of Bcl-2 heterodimers with Bak and Bim. Altogether, the identification of a subset of cell lines and primary cells effectively killed by ABT-737 alone supported the evaluation of ABT-263, an orally active counterpart to ABT-737, for the treatment of t(11;14) and hyperdiploid groups of myeloma harboring a Bcl-2(high)/Mcl-1(low) profile.

Cell Death via DR5, but not DR4, Is Regulated by p53 in Myeloma Cells

Myeloma cells are sensitive to TRAIL through the two death receptors DR4 and DR5. Because p53 directly modulates expression of death receptors, we investigated here whether p53 can modulate myeloma sensitivity to TRAIL. We found that p53 affects the sensitivity of myeloma cells to the DR5 agonistic human antibody lexatumumab but not the DR4 antibody mapatumumab. TP53 wild-type myeloma cells overexpressed DR5 in correlation with sensitivity to lexatumumab. Both nongenotoxic (nutlin-3a) and genotoxic (melphalan) p53-inducing stresses increased DR5 expression only in TP53 wild-type cells and synergistically increased lexatumumab efficiency yet did not increase DR4 expression, nor sensitivity to mapatumumab. Silencing of p53 strongly decreased DR5 expression and induced resistance to nutlin-3a and lexatumumab but did not modulate DR4 expression or sensitivity to mapatumumab. Increase of lexatumumab efficiency induced by nutlin-3a was related to a p53-dependent increase of DR5 expression. In primary myeloma cells, nutlin-3a increased DR5 expression and lexatumumab efficiency but did not increase mapatumumab efficiency. Taken together, our findings indicate that p53 controls the sensitivity of myeloma through DR5 but not DR4 and suggest that a subset of patients with multiple myeloma may benefit from DR5 therapy.

Critical role of the NOTCH ligand JAG2 in self-renewal of myeloma cells.

The purpose of this study was to identify the pathways associated with the ability of CD138(+) human myeloma cells to form colonies in a serum-free semi-solid human collagen-based assay. Only 26% (7 of 27) of human myeloma cell lines were able to spontaneously form colonies. This spontaneous clonogenic growth correlated with the expression of the NOTCH ligand JAG2 (p<0.001). Blocking JAG-NOTCH interactions with NOTCH-Fc chimeric molecules impaired self-colony formation, indicating a role for JAG-NOTCH pathway in colony formation. In two cell lines, silencing of JAG2 blocked both colony formation and in vivo tumor formation in immunocompromised mice. RT-PCR and flow cytometry analysis revealed that JAG2 is often expressed by CD138(+) primary cells. Our results indicate that spontaneous clonogenic growth of myeloma cells requires the expression of JAG2.

Heat shock factor 1 is a potent therapeutic target for enhancing the efficacy of treatments for multiple myeloma with adverse prognosis

Deregulated expression of heat shock proteins (HSPs) encoding genes is frequent in multiple myeloma. HSPs, which are molecular chaperones involved in protein homeostasis pathways, have emerged recently as promising therapeutic targets. Using human myeloma cell lines and primary myeloma cells belonging to various molecular groups, we tested the efficacy of HSP90, HSP70, and heat shock factor 1 (HSF1) inhibitors alone or associated with current antimyeloma drugs. We report here that KNK-437 (an inhibitor of HSF1) and bortezomib have additive effects on apoptosis induction in cells belonging to groups with bad prognosis.

Bendamustine and melphalan kill myeloma cells similarly through reactive oxygen species production and activation of the p53 pathway and do not overcome resistance to each other

Abstract Because the old alkylating drug bendamustine (BDM) is currently under evaluation in patients with multiple myeloma, we compared its efficacy to that of melphalan in 29 human myeloma cell lines (HMCLs). The concentrations of BDM and melphalan that killed 50% of cells (LD50) in HMCLs were linearly correlated (p < 0.001), and reactive oxygen (ROS) scavengers similarly inhibited cell death induced by both drugs. Sensitivity of HMCLs to both drugs was correlated to p53: the BDM and melphalan median LD50 values of TP53wild-type HMCLs were more than two-fold lower than those of TP53abnormal HMCLs (p < 0.001), and p53 silencing in TP53wt NCI-H929 cells inhibited BDM- and melphalan-induced cell death. Both drugs induced expression of p53 targets, p21, Puma and DR5, only in TP53wt HMCLs. In primary cells, both drugs induced an increase in DR5 expression in cells without del(17p). Finally, we demonstrated that the combined effect of BDM and melphalan was additive, and that BDM did not overcome melphalan resistance and vice versa.

The selectivity of Marinopyrrole A to induce apoptosis in MCL1(high) BCL2(low) expressing myeloma cells is related to its ability to impair protein translation.

Multiple myeloma (MM) is an incurable plasma-cell malignancy that is heterogeneous in its clinical presentation and prognosis. The gene expression profile of patients led to the molecular classification of MM patients into different disease subtypes, which takes into account the presence of primary IGH translocations and the universal over-expression of the cyclin D genes. The main translocation subtypes include t(11;14), t(4;14) and t(14;16) with an over-expression of CCND1, WHSC1 (MMSET) and MAF genes, respectively. The notion of MM heterogeneity has been extended to the BCL2 family content in each MM subgroup. Indeed, we have previously shown that the combined profile of BCL2, BCL2L1 (BCLXL) and MCL1 was sufficient to distinguish MM molecular groups (Gomez-Bougie & Amiot, 2013). Namely, MAF and WHCS1 groups can be distinguished from hyperdiploid and Cyclin D1 (CCND1) groups by a low expression of BCL2 and high MCL1 expression. Of note, WHSC1 and MAF subgroups are known to be of poor prognosis (Chesi & Bergsagel, 2013) highlighting the importance of targeting MCL1. We assessed the capacity of Marinopyrrole A, a new class of MCL1 inhibitor (Doi et al, 2012), to elicit apoptosis across a large collection of human MM cell lines (HMCLs) (n = 20) encompassing the main molecular myeloma subtypes and well characterized for BCL2 family gene and protein expression (Bodet et al, 2011). As previously described, we have authenticated each cell line used in this study by a flow cytometry-based barcode (Table SI). The median lethal dose (LD50) values of Marinopyrrole A was defined as the concentration sufficient to kill 50% of cells after 48 h of treatment. Cell lines displayed LD50 ranging from 0 7 to 11 lmol/l (Table SI). Marinopyrrole A efficiency was analysed according to the BCL2 family gene expression. We found that not only a high expression of MCL1 (P < 0 04, q = 0 45) but also a low expression of BCL2 (P < 0 0002, q = 0 63) correlated with Marinopyrrole A LD50s (Fig 1A). These results suggest that the sensitivity of Marinopyrrole A was strongly dependent on BCL2 family protein expression. Analysis of the main myeloma subgroups showed that the CCND1 HMCLs were significantly less sensitive (median LD50 4 12 lmol/l) than the other MAF and

Decitabine and Melphalan Fail to Reactivate p73 in p53 Deficient Myeloma Cells

(1) Background: TP53 deficiency remains a major adverse event in Multiple Myeloma (MM) despite therapeutic progresses. As it is not possible to target TP53 deficiency with pharmacological agents, we explored the possibility of activating another p53 family member, p73, which has not been well studied in myeloma. (2) Methods: Using human myeloma cell lines (HMCLs) with normal or abnormal TP53 status, we assessed TP73 methylation and expression. (3) Results: Using microarray data, we reported that TP73 is weakly expressed in 47 HMCLs and mostly in TP53 wild type (TP53wt) HMCLs (p = 0.0029). Q-RT-PCR assays showed that TP73 was expressed in 57% of TP53wt HMCLs (4 out of 7) and 11% of TP53 abnormal (TP53abn) HMCLs (2 out of 18) (p = 0.0463). We showed that TP73 is silenced by methylation in TP53abn HMCLs and that decitabine increased its expression, which, however, remained insufficient for significant protein expression. Alkylating drugs increased expression of TP73 only in TP53wt HMCLs but failed to synergize with decitabine in TP53abn HMCLs. (4) Conclusions: Decitabine and melphalan does not appear as a promising combination for inducing p73 and bypassing p53 deficiency in myeloma cells.