David Chiron

TLR3 Ligand Induces NF-κB Activation and Various Fates of Multiple Myeloma Cells Depending on IFN-α Production

Multiple myeloma (MM) cells express TLR. It has been shown that TLR ligands induce the proliferation, survival, and immune surveillance escape of MM cells through MyD88-TLR pathways. Deciphering TLR function in MM cells will help in understanding the mechanisms of tumor cell growth. In this study, we examined the response of MM cells to the MyD88-independent/TIR-domain-containing adapter-inducing IFN-β-dependent TLR3. Deregulation of NF-κB pathway is a feature of MM cells, and we wondered whether TLR3 activation could mobilize the NF-κB pathway. We show that five of seven human myeloma cell line (HMCL) cells expressed TLR3. In the presence of the synthetic TLR3 ligand (poly(I:C)), activation of NF-κB pathway was observed in three of five selected TLR3+ HMCL, NCI-H929, RPMI 8226, and KMM1. In agreement with NF-κB activation, only these three HMCL responded to poly(I:C), although by either an increase (KMM1) or a decrease (NCI-H929, RPMI 8226) of proliferation. We show that KMM1 increase of proliferation was prevented by NF-κB inhibitor. In contrast, inhibition of proliferation in both NCI-H929 and RPMI 8226 was due to IFN-α-induced apoptosis. We next demonstrated that p38 MAPK pathway controlled both IFN-α secretion and IFN-α-mediated cell death. Moreover, cell death also involved activation of ERK1/2 pathway. In conclusion, our results show that TLR3 ligand induces NF-κB pathway activation in MM and support a switching function of type I IFN in the functional outcome of TLR3 triggering in tumor cells.

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.

Phosphorothioate-Modified TLR9 Ligands Protect Cancer Cells against TRAIL-Induced Apoptosis

Hypomethylated CpG oligodeoxynucleotides (CpG ODNs) target TLR9 expressed by immune cells and are currently being evaluated as adjuvants in clinical trials. However, TLR signaling can promote some tumor growth and immune evasion, such as in multiple myeloma (MM). Therefore, deciphering the effects of CpG ODNs on cancer cells will help in preventing these adverse effects and in designing future clinical trials. TLR activation induces multiple signaling pathways, notably NF-κB that has been involved in the resistance to TRAIL. Thus, we wondered if CpG ODNs could modulate TRAIL-induced apoptosis in different models of tumors. Here, we show that TLR9+ (NCI-H929, NAN6, KMM1) and TLR9− MM cells (MM1S) were protected by CpG ODNs against recombinant TRAIL-induced apoptosis. By using two fully human, agonist mAbs directed against TRAIL receptors DR4 and DR5 (mapatumumab and lexatumumab, respectively), we show that the protection was restricted to DR5-induced apoptosis. Similar results were observed for two colon cancer (C45 and Colo205) and two breast cancer cell lines (HCC1569 and Cal51). The protection of CpG ODNs was mediated by its nuclease-resistant phosphorothioate backbone independent of TLR9. We next demonstrated by surface plasmon resonance that phosphorothioate-modified CpG ODNs directly bound to either TRAIL or lexatumumab and then decreased their binding to DR5. Finally, NK cell lysis of a DR5-sensitive MM cell line (NCI-H929) through TRAIL was partially inhibited by phosphorothioate-modified CpG ODNs. In conclusion, our results suggest that the phosphorothioate modification of CpG ODNs could dampen the clinical efficacy of CpG ODN-based adjuvants by altering TRAIL/TRAIL receptor interaction.

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.

p53 dysregulation in B-cell malignancies: More than a single gene in the pathway to hell

TP53 deletion or mutation is frequent in B-cell malignancies and is associated with a low response rate. We describe here the p53 landscape in B-cell malignancies, from B-Acute Lymphoblastic Leukemia to Plasma Cell Leukemia, by analyzing incidence of gain or loss of function of actors both upstream and within the p53 pathway, namely MYC, RAS, ARF, MDM2, ATM and TP53. Abnormalities are not equally distributed and their incidence is highly variable among malignancies. Deletion and mutation, usually associated, of ATM or TP53 are frequent in Diffuse Large B-Cell Lymphoma and Mantle Cell Lymphoma. MYC gain, absent in post-GC malignancies, is frequent in B-Prolymphocytic-Leukemia, Multiple Myeloma and Plasma Cell Leukemias. RAS mutations are rare except in MM and PCL. Multiple Factorial Analysis notes that MYC deregulation is closely related to TP53 status. Moreover, MYC gain, TP53 deletion and RAS mutations are inversely correlated with survival. Based on this landscape, we further propose targeted therapeutic approaches for the different B-cell malignancies.

BH3 profiling as a tool to identify acquired resistance to venetoclax in multiple myeloma

BH3 profiling as a tool to identify acquired resistance to venetoclax in multiple myeloma Venetoclax/ABT-199 is the first in the class of BCL2-specific BH3 mimetics and the most promising targeted therapy in oncology (Souers et al, 2013). Venetoclax is currently under investigation in multiple myeloma (MM), which is heterogeneous and includes either patients with a translocation on chromosome 14 with different chromosomes (4, 6, 11 or 16) or a hyperdiploidy. We demonstrated that venetoclax induces cell death in a subgroup harbouring the t(11;14) transloca-tion, expressing a high BCL2/MCL1 gene expression ratio, and that intrinsic venetoclax resistance is mediated by high MCL1 expression in MM cells (Touzeau et al, 2014). Preliminary results from an ongoing phase I clinical trial testing venetoclax in relapsed/refractory MM patients indicate that BCL2 inhibition has a tolerable safety profile and single agent activity mostly in t(11;14) patients (Kumar et al, 2015). The anticipated use of venetoclax in the treatment of MM lead us to explore the mechanisms of acquired veneto-clax resistance. We generated two venetoclax-resistant mye-loma cell lines using in vitro selection and derived resistant sublines (named-199R) from KMS12-PE and XG5 t(11;14) myeloma venetoclax-sensitive cell lines (Figs 1A, 2A) (Data S1). Both resistant sublines showed a strong reduction in V

The REFRACT-LYMA cohort study: a French observational prospective cohort study of patients with mantle cell lymphoma.

BackgroundMantle Cell Lymphoma (MCL) is often associated with progression, temporary response to therapy and a high relapse rate over time resulting in a poor long-term prognosis. Because MCL is classified as an incurable disease, therapeutic resistance is of great interest. However, knowledge about the biological mechanisms underlying resistance associated with MCL therapies and about associated predictors remains poor. The REFRACT-LYMA Cohort, a multicenter prospective cohort of patients with MCL, is set up to address this limitation. We here describe the study background, design and methods used for this cohort.Methods/DesignThe REFRACT-LYMA Cohort Study aims at including all patients (>18xa0years old) who are diagnosed with MCL in any stage of the disease and treated in specialized oncology centers in three public hospitals in Northwestern France. Any such patient providing a signed informed consent is included. All subjects are followed up indefinitely, until refusal to participate in the study, emigration or death. The REFRACT-LYMA follow-up is continuous and collects data on socio-economic status, medical status, MCL therapies and associated events (resistance, side effects). Participants also complete standardized quality of life (QOL) questionnaires. In addition, participants are asked to donate blood samples that will support ex vivo analysis of expression and functional assays required to uncover predictive biomarkers and companion diagnostics. If diagnostic biopsies are performed during the course of the disease, extracted biological samples are kept in a dedicated biobank.DiscussionTo our knowledge, the REFRACT-LYMA Cohort Study is the first prospective cohort of patients with MCL for whom “real-life” medical, epidemiological and QOL data is repeatedly collected together with biological samples during the course of the disease. The integrative cohort at mid-term will be unique at producing a large variety of data that can be used to conceive the most effective personalized therapy for MCL patients. Additionally, the REFRACT-LYMA Cohort puts the medical care of MCL patients in a health and pharmacoeconomic perspective.

Rationale for targeting tumor cells in their microenvironment for mantle cell lymphoma treatment

Abstract Mantle cell lymphoma (MCL) is an aggressive non-Hodgkin lymphoma associated with poor prognosis, and despite recent improvements in the therapeutic strategies for treating MCL, its management remains challenging. While improvements in next generation sequencing technology have greatly increased our understanding of the intrinsic abnormalities of MCL, the role of extrinsic signaling remains largely unknown. Recent studies have highlighted the central role of the MCL microenvironment in tumor cell survival, drug resistance and proliferation. Characterization of the diverse MCL tumoral niches and comprehension of the crosstalk between tumor cells and surrounding cells within the MCL microenvironment are needed to increase treatment efficacy. Here, we reviewed the recent findings regarding the MCL microenvironment that could be rapidly translated into new therapeutic strategies to overcome drug resistance during MCL treatment.

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.