Novel Approaches to Improve Myeloma Cell Killing by Monoclonal Antibodies

The monoclonal antibodies (mAbs) have significantly changed the treatment of multiple myeloma (MM) patients. However, despite their introduction, MM remains an incurable disease. The mAbs currently used for MM treatment were developed with different mechanisms of action able to target antigens, such as cluster of differentiation 38 (CD38) and SLAM family member 7 (SLAMF7) expressed by both, MM cells and the immune microenvironment cells. In this review, we focused on the mechanisms of action of the main mAbs approved for the therapy of MM, and on the possible novel approaches to improve MM cell killing by mAbs. Actually, the combination of anti-CD38 or anti-SLAMF7 mAbs with the immunomodulatory drugs significantly improved the clinical effect in MM patients. On the other hand, pre-clinical evidence indicates that different approaches may increase the efficacy of mAbs. The use of trans-retinoic acid, the cyclophosphamide or the combination of anti-CD47 and anti-CD137 mAbs have given the rationale to design these types of combinations therapies in MM patients in the future. In conclusion, a better understanding of the mechanism of action of the mAbs will allow us to develop novel therapeutic approaches to improve their response rate and to overcome their resistance in MM patients

PROTEASOME INHIBITORS MODULATE OSTEOCYTE DEATH AND AUTOPHAGY IN MULTIPLE MYELOMA.

Background: Cell death and autophagy are the main cellular processes involved in the regulation of bone remodeling by osteocytes. Recently we have demonstrated that an increased osteocyte death is involved in multiple myeloma (MM)-induced osteolysis through the upregulation of osteoclast recruitment. Aims: Because proteasome inhibitors including Bortezomib (BOR) are known to be able to target osteoblasts in this study we have investigated the potential effect of these drugs on osteocytes and their cell death and autophagy. Methods: Firstly the effect of the proteasome inhibitors BOR and MG262 on osteocyte viability was evaluated in vitro in murine osteocytic cell line MLO-Y4 and in the human pre-osteocytic one HOB-01. Both cell lines were co-coltured for 48 hours in the presence or absence of the human myeloma cell lines (HMCLs) RPMI8226 and JJN3, placed in a transwell insert in the presence or the absence of BOR or MG262. Moreover the effect of proteasome inhibitors on dexamethasone (DEX)-induced MLO-Y4 death, obtained at high doses (10-5-10-6M), was checked in combination with PTH(1-34). To evaluate the presence of autophagy and apoptosis in osteocytes, we checked the expression of both autophagic marker LC3 and apoptotic marker APAF-1 by confocal microscopy in the co-colture system with MLO-Y4 and RPMI-8226. Finally we performed a retrospective histological evaluation on bone biopsies of a cohort of 31 newly diagnosis MM underwent to different treatments including BOR-based regimen. Bone biopsies were obtained at the diagnosis and after an average time of 12 months of treatment. Osteocyte viability was evaluated in a total of 500 lacunae per histological sections. Results: The in vitro treatment with BOR or MG262 significantly blunted MLO-Y4 and HOB-01 cell death. Similarly, DEXinduced MLO-Y4 death was reduced by proteasome inhibitors. Interestingly, we found that both proteasome inhibitors potentiated the PTH (1-34) short-term effects on DEX-induced osteocyte death. Prevalence of autophagic cell death compared to apoptosis was observed in this system. In line with these data, we showed that neither the HMCLs nor treatment with DEX increase the apoptotic death and caspase 3 activation in both MLO-Y4 and HOB-01 cell lines. BOR treatment increased the basal level of LC3 indicating a pro-survival and protective function of autophagy against the BOR-induce stress. On the contrary, when the cells undergo to a stronger stress such as in the presence of HMCLs or by treatment with high dose of DEX we found that both proteasome inhibitors blocked autophagic cell death in osteocytes. In the in vivo study we found a significant increase of the number of viable osteocytes in MM patients treated with BOR-based regimen as compared to those treated without BOR (% median increase: +6% vs. +1.30%; p=0.017). Patients treated with BOR alone showed the highest increase of osteocyte viability, as compared to those either treated without BOR (+11.6% vs. +1.3%, p=0.0019) or treated with BOR plus DEX (+11.6% vs. +4.4%, p=0.01). On the other hand, any significant difference was not observed in patients treated with Thalidomide (THAL) or Immunomodulatory drugs (IMiDs) than in those untreated with these drugs (p= 0.7). A multiple regression non-parametric analysis showed that BOR had a significant positive impact on osteocyte viability (p=0.042) whereas THAL/IMiDs as well as Zoledronic acid (ZOL) treatments have not (p=0.2). BOR also counterbalanced the negative effect of DEX treatment (p=0.035). Summary/Conclusion: Our data suggest that proteasome inhibitors blunted osteocyte cell death induced by MM cells and DEX through the modulation of the autophagy and potentiated the effect of PTH. Overall our in vitro and in vivo data support the use of BOR to improve bone integrity in MM patients

Mechanism of Action of Bortezomib and the New Proteasome Inhibitors on Myeloma Cells and the Bone Microenvironment: Impact on Myeloma-Induced Alterations of Bone Remodeling

Multiple myeloma (MM) is characterized by a high capacity to induce alterations in the bone remodeling process. The increase in osteoclastogenesis and the suppression of osteoblast formation are both involved in the pathophysiology of the bone lesions in MM. The proteasome inhibitor (PI) bortezomib is the first drug designed and approved for the treatment of MM patients by targeting the proteasome. However, recently novel PIs have been developed to overcome bortezomib resistance. Interestingly, several preclinical data indicate that the proteasome complex is involved in both osteoclast and osteoblast formation. It is also evident that bortezomib either inhibits osteoclast differentiation induced by the receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL) or stimulates the osteoblast differentiation. Similarly, the new PIs including carfilzomib and ixazomib can inhibit bone resorption and stimulate the osteoblast differentiation. In a clinical setting, PIs restore the abnormal bone remodeling by normalizing the levels of bone turnover markers. In addition, a bone anabolic effect was described in responding MM patients treated with PIs, as demonstrated by the increase in the osteoblast number. This review summarizes the preclinical and clinical evidence on the effects of bortezomib and other new PIs on myeloma bone disease

Myeloma-Induced Osteocyte Death Was Blunted By Proteasome Inhibitors Through The Modulation Of Autophagy

Osteocytes are critical in the maintenance of bone integrity regulating bone remodeling through the cell death and autophagy, a cellular process stress-induced to prolong cell survival but when induced excessively can cause cell death. Recently we have demonstrated that an increased osteocyte death is involved in multiple myeloma (MM)-induced osteolysis. However the mechanisms involved in this process as well as the effect of the proteasome inhibitors able to stimulate bone formation are not known and have been investigated in this study. Firstly the effect of the proteasome inhibitors BOR and MG262 on osteocyte viability was evaluated in vitro in murine osteocytic cell line MLO-Y4 and in the human pre-osteocytic one HOB-01. Both cell lines were co-coltured for 48 hours in the presence or absence of the human myeloma cell lines (HMCLs) RPMI8226 and JJN3, placed in a traswell insert. The treatment for 12-24 hours with (BOR) (2nM) and MG262 (10nM) significantly blunted MLO-Y4 and HOB-01 cell death. In addition, dexamethasone (DEX)-induced MLO-Y4 apoptosis, obtained at high doses (10-5-10-6 M), was reduced by the treatment with proteasome inhibitors. Interestingly, we found that PTH short-term treatment potentiated the in vitro effects of proteasome inhibitors on DEX-induced osteocyte death. To evaluate the presence of autophagy in osteocytes, we checked the expression of the autophagic marker LC3 both by confocal microscopy and western blot analysis in the co-colture system with MLO-Y4 and RPMI-8226. Prevalence of autophagic cell death and in a lesser extent apoptosis was observed in this system. BOR increased the basal level of LC3 indicating a pro-survival and protective function of autophagy against the BOR-induce stress. On the contrary, when cells undergo to a stronger stress such as in the presence of HMCLs or by treatment with high dose of DEX we found that both proteasome inhibitors BOR and MG262 blocked autophagic cell death in osteocytes. To translate our in vitro evidence in a clinical perspective, thereafter we performed a histological evaluation on bone biopsies of a cohort of 37 newly diagnosis MM patients 31 of them with symptomatic MM and 6 with smoldering MM (SMM). The 55% of patients with MM have evidence of osteolytic lesions at the X-rays survey. Bone biopsies were obtained at the diagnosis and after an average time of 12 months of treatment or observation. Osteocyte viability was evaluated in a total of 500 lacunae per histological sections. A significant increase of the number of viable osteocytes was demonstrated in MM patients treated with BOR-based regimen as compared to those treated without BOR (% median increase: +6% vs. +1.30%; p=0.017). Patients treated with BOR alone showed the highest increase of osteocyte viability, as compared to those either treated without BOR (+11.6% vs. +1.3%, p=0.0019) or treated with BOR plus DEX (+11.6% vs. +4.4%, p=0.01). A reduction of both osteocyte apoptosis and autophagy was demonstrated by TUNEL assays and confocal microscopy. On the other hand, any significant difference was not observed in patients treated with Thalidomide (THAL) or Immunomodulatory drugs (IMiDs) than in those untreated with these drugs (p= 0.7). A multiple regression non-parametric analysis showed that BOR had a significant positive impact on osteocyte viability (p=0.042) whereas THAL/IMiDs as well as Zoledronic acid (ZOL) treatments have not (p=0.2). BOR also counterbalanced the negative effect of DEX treatment (p=0.035). Our data suggest that proteasome inhibitors blunted osteocyte cell death induced by MM cells and DEX through the modulation of the autophagy supporting their use to improve bone integrity in MM patients

Bovine pestivirus is a new alternative virus for multiple myeloma oncolytic virotherapy

The oncolytic viruses have shown promising results for the treatment of multiple myeloma. However, the use of human viruses is limited by the patients' antiviral immune response. In this study, we investigated an alternative oncolytic strategy using non-human pathogen viruses as the bovine viral diarrhea virus (BVDV) that were able to interact with CD46

Proteasome Inhibitors Block Myeloma-Induced Osteocyte Death in Vitro and in Vivo in Multiple Myeloma Patients

Multiple myeloma (MM) is characterized by a severe unbalanced and uncoupling bone remodeling leading to osteolysis. We have recently shown that osteocytes are involved in MM-induced osteolysis through an increased cell death. Accordingly MM patients are characterized by a reduced number of viable osteocytes related to the presence of bone lesions. Proteasome inhibitors currently used in the treatment of MM are able to stimulate osteoblast formation but their potential effects on osteocyte death are not known and have been investigated in this study both in vitro and in vivo. Osteocytic MLO-Y4 cells or human pre-osteocytic HOB-01 cells were co-cultured for 48 hours in the presence or absence of the human myeloma cell lines (HMCLs) JJN3 or RPMI-8226 placed in a transwell insert. A significantly reduction of ostecyte viability was observed (median percent reduction of MLO-Y4 viability: -16% and -30%, respectively). The treatment for 12–24 hours with Bortezomib (BOR) (2nM) or other proteasome inhibitors such as MG262 (10nM) or MG132 (100nM) significantly blunted MLO-Y4 and HOB-01 cell death. Similarly, Dexamethasone (DEX)-induced MLO-Y4 apoptosis, obtained at pharmacological doses (10–4–10–5 M), was significantly reduced by the treatment with proteasome inhibitors. To translate our in vitro data into a clinical perspective we performed a retrospective histological evaluation on bone biopsies of a cohort of 40 newly diagnosis MM patients (24 male and 16 female, median age: 68 years) 34 of them with symptomatic MM and 6 with smoldering MM (SMM). The 58% of patients with symptomatic MM have evidence of osteolytic lesions at the X-rays survey. Bone biopsies were obtained in both symptomatic MM and SMM at diagnosis and after an average time of 12 months of treatment or observation, respectively. The 68% of patients with symptomatic MM were treated with a BOR-based regimen while 42% do not. Moreover the 58% of MM patients received DEX and the 59% Thalidomide (TAL). Zoledronic acid (ZOL) was infused monthly in the 60% of MM patients. Osteocyte viability was evaluated in a total of 500 lacunae per histological sections, corresponds to the total number of osteocyte lacunae in the bone biopsies. The number of viable osteocytes and the number of degenerated or apoptotic osteocytes and empty lacunae have been evaluated. In patients with SMM no significant change was observed in the number of viable osteocytes in the two histological evaluations carried out (median percent change: +1.2, p=0.68, NS). In symptomatic MM patients the mean percent change of the osteocyte viability was not correlated with the response rate to treatment (R2 0.01, p=NS). A significant increase of the number of viable osteocytes was demonstrated in MM patients treated with BOR-based regimen as compared to those treated without BOR (% median increase of osteocyte viability: +6% vs. +1.30%, Mann-Whitney test: p=0.017). Patients treated with BOR alone showed the highest increase of osteocyte viability that was statistical significant in comparison with that observed either in patients treated without BOR (+11.6% vs. +1.3%, p=0.0019) or in those treated with BOR plus DEX (+11.6% vs. +4.4%, p=0.01). On the contrary, no significant difference was observed in patients treated with TAL than in those treated without TAL (p= 0.7, NS) as well as patients treated with ZOL compared to those untreated showed no significant difference in the number of viable osteocytes (p=0.18, NS). To confirm the role of the different drug treatment on the osteocyte viability we perform a multiple regression non-parametric analysis showing that BOR had a significant positive impact on osteocyte viability (p=0.042) whereas ZOL and TAL have not (p>0.2,NS) and it counterbalanced the negative effect of DEX treatment (p=0.035). In conclusion our in vitro and in vivo data suggest the proteasome inhibitors block osteocyte death induced by MM cells could have a positive impact on bone integrity in MM patients

New Insights into Osteogenic and Chondrogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells and Their Potential Clinical Applications for Bone Regeneration in Pediatric Orthopaedics

Human mesenchymal stem cells (hMSCs) are pluripotent adult stem cells capable of being differentiated into osteoblasts, adipocytes, and chondrocytes. The osteogenic differentiation of hMSCs is regulated either by systemic hormones or by local growth factors able to induce specific intracellular signal pathways that modify the expression and activity of several transcription factors. Runt-related transcription factor 2 (Runx2) and Wnt signaling-related molecules are the major factors critically involved in the osteogenic differentiation process by hMSCs, and SRY-related high-mobility-group (HMG) box transcription factor 9 (SOX9) is involved in the chondrogenic one. hMSCs have generated a great interest in the field of regenerative medicine, particularly in bone regeneration. In this paper, we focused our attention on the molecular mechanisms involved in osteogenic and chondrogenic differentiation of hMSC, and the potential clinical use of hMSCs in osteoarticular pediatric disease characterized by fracture nonunion and pseudarthrosis

New Insights into Osteogenic and Chondrogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells and Their Potential Clinical Applications for Bone Regeneration in Pediatric Orthopaedics

Human mesenchymal stem cells (hMSCs) are pluripotent adult stem cells capable of being differentiated into osteoblasts, adipocytes, and chondrocytes. The osteogenic differentiation of hMSCs is regulated either by systemic hormones or by local growth factors able to induce specific intracellular signal pathways that modify the expression and activity of several transcription factors. Runt-related transcription factor 2 (Runx2) and Wnt signaling-related molecules are the major factors critically involved in the osteogenic differentiation process by hMSCs, and SRY-related high-mobility-group (HMG) box transcription factor 9 (SOX9) is involved in the chondrogenic one. hMSCs have generated a great interest in the field of regenerative medicine, particularly in bone regeneration. In this paper, we focused our attention on the molecular mechanisms involved in osteogenic and chondrogenic differentiation of hMSC, and the potential clinical use of hMSCs in osteoarticular pediatric disease characterized by fracture nonunion and pseudarthrosis

Identification of <i>PSMB4</i> and <i>PSMD4</i> as novel target genes correlated with 1q21 amplification in patients with smoldering myeloma and multiple myeloma

Multiple myeloma (MM) is a malignant plasma cell (PC) dyscrasia characterized by heterogeneous biological features and genetic alterations, resulting in a wide range of disease courses.1,2 Despite all the therapeutic strategies developed in the last three decades, MM is still incurable, and almost all patients will inevitably experience disease progression and eventually relapse.3 Among all the genetic abnormalities, the amplification of the 1q21 region is one of the most frequent cytogenetic abnormalities occurring in malignant PC and it has become a new prognostic factor in MM patients.4,5 The incidence of gain and/or amplification of the 1q21 locus (1q21+) increases with disease progression. It can be detected in around 30-45% of patients with smoldering MM (SMM) and newly diagnosed MM (NDMM), and in around 70% of relapsed/refractory MM patients (RRMM).6 The impact of 1q21 on disease progression at an early stage has not been widely investigated. A few studies have suggested that the acquisition of extra 1q21 copies may play a role in disease progression.7,8 In fact, SMM patients with 1q21+ may be more likely to progress to MM than patients without 1q21+.8 Recent studies have demonstrated that the 1q21 copy number has a different impact on the responsiveness to MM treatments, especially proteasome inhibition (PI).9 PI is a well-established anti-cancer treatment approach used in MM. Throughout the years, the implementation of PI drugs as part of standard MM therapy has continued to improve the quality of life and clinical outcomes of MM patients. Furthermore, additional copies of 1q21 have been associated with PI resistance and recurrence of the disease in patients with 1q21+, limiting the long-term medical utility of PI.9,10 Recent studies have demonstrated that patients with 1q21+ treated with combination treatment with bortezomib (Bor) have inferior progression-free survival and overall survival compared to patients who do not present 1q21+.11 Similar results were observed when patients harboring 1q21 ampliSeveral genes are known to be deregulated upon the amplification of the 1q21 locus;9 nonetheless, the pathogenic and their possible role as druggable targets is not fully understood. In our study, we analyzed primary MM bone marrow (BM) PC from both SMM and NDMM patients to identify gene