MCL1 Inhibitors in Multiple Myeloma

Apoptosis plays a key role, not only in normal homeostasis but also in protection against genomic instability. Protection against apoptosis is a hallmark of cancer and is mainly regulated by the overexpression of anti-apoptotic proteins such as Bcl-2, Bcl-Xl or Mcl-1. This results in increased survival of the tumor cells and resistance to therapy. This presentation will focus on MCL-1 (myeloid cell leukemia 1), its expression and its role as potential target in multiple myeloma (MM). MCL1 gene regions are one the most amplified gene regions in several human cancers and Mcl-1 activity is often associated with therapy resistance and relapse. Mcl-1 binds to and sequesters the pro-apoptotic BH3 proteins, thereby preventing apoptosis. Mcl-1 is overexpressed on MM cells from newly diagnosed patients compared to normal plasma cells and in MM cells at relapse. This overexpression is furthermore associated with a shorter survival of these patients. Increased Mcl-1 expression can result either from genetic lesions or by induction through interaction with the bone marrow microenvironment. Its expression is correlated with the molecular heterogeneity of the myeloma patients; while the CCDN1 group has high BCL2 and low MCL-1 expression; the MMSET and MAF group has high MCL-1 and low BCL2 expression. Unlike Bcl-2 and Bcl-Xl, Mcl-1 has a large unstructured aminoterminus and its activity is mainly dependent on posttranslational modifications. The bone marrow microenvironment, by producing high levels of interleukin 6, also induces the upregulation of Mcl-1. Furthermore, our group recently demonstrated that not only stromal cells in the bone marrow microenvironment, but also MDSC (myeloid derived suppressor cells) induce survival of MM cells by increasing Mcl-1 levels through the AMPK pathway. As such, these data suggest the potential therapeutic benefit of targeting Mcl-1 in MM patients. Developing the first-generation inhibitors appeared to be challenging, especially in view of the occurrence of unwanted off target effects. Recent preclinical data with new, selective Mcl-1 inhibitors show promising anti-tumor effects both in vitro and in in vivo myeloma models, either alone or in combination with the Bcl-2 selective inhibitor, venetoclax, especially as it was demonstrated that high levels of MCL-1 are associated with venetoclax resistance in MM. In addition, it was also shown that proteasome inhibition can trigger Mcl-1 accumulation, further pointing to the importance of Mcl-1 inhibition. Induction of NOXA, as an inhibitor of Mcl-1, is also suggested as a therapeutic option, especially in combinations with other drugs. Clinically, following preclinical results, several new Mcl-1 inhibitors have entered phase I trials. Most of them are still recruiting patients, and as such too early to have results. Disclosures No relevant conflicts of interest to declare.

Download Full-text

A novel BCMA/CD3 bispecific T-cell engager for the treatment of multiple myeloma induces selective lysis in vitro and in vivo

Leukemia ◽

10.1038/leu.2016.388 ◽

2016 ◽

Vol 31 (8) ◽

pp. 1743-1751 ◽

Cited By ~ 86

Author(s):

S Hipp ◽

Y-T Tai ◽

D Blanset ◽

P Deegen ◽

J Wahl ◽

...

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

T Cell ◽

Plasma Cells ◽

Ex Vivo ◽

Xenograft Model ◽

Selective Lysis ◽

Bispecific T Cell Engager

Abstract B-cell maturation antigen (BCMA) is a highly plasma cell-selective protein that is expressed on malignant plasma cells of multiple myeloma (MM) patients and therefore is an ideal target for T-cell redirecting therapies. We developed a bispecific T-cell engager (BiTE) targeting BCMA and CD3ɛ (BI 836909) and studied its therapeutic impacts on MM. BI 836909 induced selective lysis of BCMA-positive MM cells, activation of T cells, release of cytokines and T-cell proliferation; whereas BCMA-negative cells were not affected. Activity of BI 836909 was not influenced by the presence of bone marrow stromal cells, soluble BCMA or a proliferation-inducing ligand (APRIL). In ex vivo assays, BI 836909 induced potent autologous MM cell lysis in both, newly diagnosed and relapsed/refractory patient samples. In mouse xenograft studies, BI 836909 induced tumor cell depletion in a subcutaneous NCI-H929 xenograft model and prolonged survival in an orthotopic L-363 xenograft model. In a cynomolgus monkey study, administration of BI 836909 led to depletion of BCMA-positive plasma cells in the bone marrow. Taken together, these results show that BI 836909 is a highly potent and efficacious approach to selectively deplete BCMA-positive MM cells and represents a novel immunotherapeutic for the treatment of MM.

Download Full-text

Dual Targeting of -TORC1 and -TORC2 as a New Strategy In the Treatment of Multiple Myeloma

Blood ◽

10.1182/blood.v116.21.133.133 ◽

2010 ◽

Vol 116 (21) ◽

pp. 133-133 ◽

Cited By ~ 2

Author(s):

Patricia Maiso ◽

AbdelKareem Azab ◽

Yang Liu ◽

Yong Zhang ◽

Feda Azab ◽

...

Keyword(s):

Cell Cycle ◽

Multiple Myeloma ◽

Bone Marrow ◽

Board Of Directors ◽

Cell Lines ◽

Mechanism Of Action ◽

Plasma Cells ◽

Bone Marrow Microenvironment ◽

Advisory Committees

Abstract Abstract 133 Introduction: Mammalian target of rapamycin (mTOR) is a downstream serine/threonine kinase of the PI3K/Akt pathway that integrates signals from the tumor microenvironment such as cytokines and growth factors, nutrients and stresses to regulate multiple cellular processes, including translation, autophagy, metabolism, growth, motility and survival. Mechanistically, mTOR operates in two distinct multi-protein complexes, TORC1 and TORC2. Activation of TORC1 leads to the phosphorylation of p70S6 kinase and 4E-BP1, while activation of TORC2 regulates phosphorylation of Akt and other AGC kinases. In multiple myeloma (MM), PI3K/Akt plays an essential role enhancing cell growth and survival and is activated by the loss of the tumor suppressor gene PTEN and by the bone marrow microenvironment. Rapamycin analogues such as RAD001 and CCI-779 have been tested in clinical trials in MM. Their efficacy as single agents is modest, but when used in combination, they show higher responses. However, total inhibition of Akt and 4E-BP1 signaling requires inactivation of both complexes TORC1 and TORC2. Consequently, there is a need for novel inhibitors that can target mTOR in both signaling complexes. In this study we have evaluated the role of TORC1 and TORC2 in MM and the activity and mechanism of action of INK128, a novel, potent, selective and orally active small molecule TORC1/2 kinase inhibitor. Methods: Nine different MM cell lines and BM samples from MM patients were used in the study. The mechanism of action was investigated by MTT, Annexin V, cell cycle analysis, Western-blotting and siRNA assays. For the in vivo analyses, Luc+/GFP+ MM.1S cells (2 × 106/mouse) were injected into the tail vein of 30 SCID mice and tumor progression was detected by bioluminescence imaging. Nanofluidic proteomic immunoassays were performed in selected tumors. Results: To examine activation of the mTOR pathway in MM, we performed kinase activity assays and protein analyses of mTOR complexes and its downstream targets in nine MM cell lines. We found mTOR, Akt, pS6R and 4E-BP1 are constitutively activated in all cell lines tested independently of the status of Deptor, PTEN, and PI3K. All cell lines expressed either Raptor, Rictor or both; excepting H929 and U266LR7 which were negative for both of them. Moreover, primary plasma cells from several MM patients highly expressed pS6R while normal cells were negative for this protein. We found that INK128 and rapamycin effectively suppressed phosphorylation of p6SR, but only INK128 was able to decrease phosphorylation of 4E-BP1. We observed that INK128 fully suppressed cell viability in a dose and time dependent manner, but rapamycin reached a plateau in efficacy at ± 60%. The IC50 of INK128 was in the range of 7.5–30 nM in the eight cell lines tested. Similar results were observed in freshly isolated plasma cells from MM patients. Besides the induction of apoptosis and cell cycle arrest, INK128 was more potent than rapamycin to induce autophagy, and only INK128 was able to induce PARP and Caspases 3, 8 and 9 cleavage. In the bone marrow microenvironment context, INK128 inhibited the proliferation of MM cells and decreased the p4E-BP1 induction. Importantly, treatment with rapamycin under such conditions did not affect cell proliferation. INK128 also showed a significantly greater effect inhibiting cell adhesion to fibronectin OPM2 MM1S, BMSCs and HUVECs compared to rapamycin. These results were confirmed in vivo. Oral daily treatment of NK128 (1.0 mg/kg) decreased tumor growth and improved survival of mice implanted with MM1S. Conclusion: Dual inhibition of TORC1 and TORC2 represent a new and promising approach in the treatment of MM and its microenvironment. The ability of INK128 to inhibit both TORC1 and TORC2 strongly supports the potential use of this compound in MM patients. Disclosures: Anderson: Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Ghobrial:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

Download Full-text

Mcl-1 Is Overexpressed in Multiple Myeloma and Correlates with Disease Severity.

Blood ◽

10.1182/blood.v104.11.1419.1419 ◽

2004 ◽

Vol 104 (11) ◽

pp. 1419-1419

Author(s):

Soraya Wuilleme-Toumi ◽

Nelly Robillard ◽

Patricia Gomez-Bougie ◽

Philippe Moreau ◽

Steven Le Gouill ◽

...

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Disease Severity ◽

Cell Lines ◽

Plasma Cells ◽

Myeloma Cell ◽

Lymphocytic Leukemia ◽

Myeloma Cells

Abstract Multiple Myeloma (MM) is a fatal malignancy of B-cell origin characterized by the accumulation of plasma cells within the bone marrow. The expression of the pro-survival members of the Bcl-2 family has been shown to be a key process in the survival of myeloma cells. More particularly, Mcl-1 expression turned out to be critical for their survival. Indeed, knockdown of Mcl-1 by antisenses induces apoptosis in myeloma cells. Finally, Mcl-1 was found to be the only anti-apoptotic Bcl-2 family member which level of expression was modified by cytokine treatment of myeloma cells. For these reasons, we have evaluated the expression of Mcl-1 in vivo in normal, reactive and malignant plasma cells (PC) i.e., myeloma cells from 55 patients with MM and 20 human myeloma cell lines using flow cytometry. We show that Mcl-1 is overexpressed in MM in comparison with normal bone marrow PC. Forty-seven percent of patients with MM at diagnosis (p=.017) and 80% at relapse (p=.014 for comparison with diagnosis) overexpress Mcl-1. Of note, only myeloma cell lines but not reactive plasmocytoses have abnormal Mcl-1 expression, although both plasmocyte expansion entities share similar high proliferation rates (>20%). Of interest, Bcl-2 as opposed to Mcl-1, does not discriminate malignant from normal PC. This shows that the overexpression of Mcl-1 is clearly related to malignancy rather than to proliferation. It will be important to know whether the overexpression of Mcl-1 is related to an abnormal response to cytokines like Interleukin-6 or to mutations of the promoter of the Mcl-1 gene as already described in B chronic lymphocytic leukemia. Finally, level of Mcl-1 expression is related to disease severity, the highest values being correlated with the shortest event-free survival (p=.01). In conclusion, Mcl-1 which has been shown to be essential for the survival of human myeloma cells in vitro is overexpressed in vivo in MM and correlates with disease severity. Mcl-1 represents a major therapeutical target in MM.

Download Full-text

Repurposing tofacitinib as an anti-myeloma therapeutic to reverse growth-promoting effects of the bone marrow microenvironment

10.1101/143206 ◽

2017 ◽

Author(s):

Christine Lam ◽

Megan Murnane ◽

Hui Liu ◽

Geoffrey A. Smith ◽

Sandy Wong ◽

...

Keyword(s):

Bone Marrow ◽

Stromal Cells ◽

Plasma Cells ◽

Single Agent ◽

Drug Repurposing ◽

Myeloma Cell ◽

Bone Marrow Microenvironment ◽

Growth Promoting

AbstractThe myeloma bone marrow microenvironment promotes proliferation of malignant plasma cells and resistance to therapy. Interleukin-6 (IL-6) and downstream JAK/STAT signaling are thought to be central components of these microenvironment-induced phenotypes. In a prior drug repurposing screen, we identified tofacitinib, a pan-JAK inhibitor FDA-approved for rheumatoid arthritis, as an agent that may reverse the tumor-stimulating effects of bone marrow mesenchymal stromal cells. Here, we validated bothin vitro, in stromal-responsive human myeloma cell lines, andin vivo, in orthotopic disseminated murine xenograft models of myeloma, that tofacitinib showed both single-agent and combination therapeutic efficacy in myeloma models. Surprisingly, we found that ruxolitinib, an FDA-approved agent targeting JAK1 and JAK2, did not lead to the same anti-myeloma effects. Combination with a novel irreversible JAK3-selective inhibitor also did not enhance ruxolitinib effects. RNA-seq and unbiased phosphoproteomics revealed that marrow stromal cells stimulate a JAK/STAT-mediated proliferative program in myeloma plasma cells, and tofacitinib reversed the large majority of these pro-growth signals. Taken together, our results suggest that tofacitinib specifically reverses the growth-promoting effects of the tumor microenvironment through blocking an IL-6-mediated signaling axis. As tofacitinib is already FDA-approved, these results can be rapidly translated into potential clinical benefits for myeloma patients.

Download Full-text

Altered Iron Metabolism Is a New Targetable Hallmark for Multiple Myeloma

Blood ◽

10.1182/blood-2019-123473 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 3059-3059

Author(s):

Can Li ◽

Xuelian Tan ◽

Qierra Brockman ◽

Yogesh Jethava ◽

Marta Chesi ◽

...

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Flow Cytometry ◽

Western Blot ◽

Plasma Cells ◽

Macrophage Polarization ◽

Mouse Bone Marrow ◽

Iron Dextran

Conventional therapies to multiple myeloma (MM) are not aimed at specific molecular targets leading ultimately to treatment resistance. Recent reports have shown that iron is instrumental in cancer development and progression and that high intracellular iron levels are associated with poor prognosis. We have demonstrated that MM cells exhibit dysregulated iron homeostasis and that limitation of cytosolic iron inhibits MM cell growth both in vitro and in vivo. The potential therapeutic role of iron should be further investigated to better understand how targeting high-iron MM cells could prevent or delay MM development and recurrence. Our study will provide crucial insights into the iron biology of MM pathogenesis and may lead to novel MM therapy. In this study, two mouse models, young Vk*MYC and old KaLwRij mice, were injected with iron dextran (1.25 mg/kg, IP, once a week). Tumor burden was monitored by serial Serum Protein Electrophoresis (SPEP) tests, flow cytometry, and immunohistochemistry. In vitro co-culturing of ARP1 MM cells with macrophages was employed to determine iron transfer. To determine iron's roles in MM evolution, we injected iron dextran into Vk*MYC mice at 8-week age. Vk*MYC mice develop MGUS around 40-50 weeks with plasma cell (PC) bone marrow infiltration and kidney damage etc. Iron-dextran was used because it is primarily taken up by macrophages. After 14-16 weeks of iron injection, M spike was detected in the injected Vk*MYC mice. The percentage of bone marrow plasma cells (CD138+) were significantly increased to 9% in the Vk*MYC mice injected with iron compared to control mice injected with vehicle by flow cytometry and immunohistochemistry. The acceleration of disease progression via iron injection was also tested in KaLwRij mice, which also spontaneously develops MGUS in old age. M protein was detected in 12 of 15 mice (80%) injected with iron dextran for 10 weeks and 1 of 5 KaLwRij (20%) control mice at 18-months of age. CD138+ B220- plasma cells were determined by flow cytometry. A significant increase of CD138+B220- plasma cells in iron treated mice (4% versus 2%) was observed compared to vehicle control mice. Deparaffined sections of bone marrow from the above mice were stained with Prussian blue and confirmed positive staining of macrophages from iron administrated mice. These results indicate that iron accelerates MGUS development in vivo. We next evaluated whether MM cells accumulate iron from the microenvironment. ARP1 MM cells were co-cultured with primary macrophages derived from mouse bone marrow to mimic disease environment in vitro. Under these conditions, MM cells induced macrophage polarization from M0 to M1 and M2. Furthermore, increased macrophage polarization was confirmed in vivo from the KaLwRij mice injected with 5TGM1 MM cells. To confirm that MM cells uptake iron from macrophages, increased intracellular ferritin levels were observed by western blot in ARP1 MM cells following co-culture with iron-loaded macrophages. We observed that this increase in intracellular ferritin was mediated via the transferrin receptor. This iron mobilization was prevented by iron chelation. Additionally, we confirmed that ferritin levels were higher in CD138+ primary human MM cells compared to CD138- non-MM cells by western blot. Our data indicate that MM cells promote macrophage polarization resulting in the transferring of iron into MM cells. The blockade of iron trafficking between MM cells and macrophages might hold a promise for the prevention and therapy in MM. Disclosures Bergsagel: Celgene: Consultancy; Ionis Pharmaceuticals: Consultancy; Janssen Pharmaceuticals: Consultancy. Zhan:BIPHARM LLC: Consultancy, Other: % Allocation of Profit.

Download Full-text

Gadolinium Containing Contrast Agent Promotes Multiple Myeloma Cell Growth: Implication for Clinical Use of MRI in Myeloma.

Blood ◽

10.1182/blood.v114.22.1809.1809 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1809-1809

Author(s):

Mariateresa Fulciniti ◽

Swaminathan Sundararaman ◽

Puru Nanjappa ◽

Samir B Amin ◽

Prajwal Chevireddy ◽

...

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Cell Growth ◽

Contrast Agent ◽

Conflicts Of Interest ◽

Bone Lesions ◽

Myeloma Cells ◽

Growth Promoting

Abstract Abstract 1809 Poster Board I-835 Bone marrow infiltration by myeloma cells and osteolytic bone lesions are the major features of Multiple Myeloma. Magnetic Resonance Imaging (MRI) has been used in MM not only to image bone marrow (BM) and to identify lytic bone disease but to also evaluate therapeutic response and prognosis. Gadolinium (Gd)-based contrast agents are frequently used to enhance MRI resolution. We evaluated effect of the most common Gd-containing agent, Omniscan, on myeloma cells. We observed that Omniscan induced both time and dose dependent MM cell growth in vitro (8-20 fold increase relative to control). Importantly, the presence of BMSC enhanced the effect of Omniscan on growth of both MM cell lines and primary MM cells. However, Omniscan was not able to overcome cytotoxic effects of conventional and novel agents in MM. This growth promoting effects were not observed on normal BM stromal cells. Evaluating the molecular mechanism of action of Omniscan on MM cells, we observed time dependent ERK1/2 phosphorylation as well as reversal of growth promoting effects of Omniscan by specific inhibition of ERK signaling; however, Omniscan had no effect on STAT3 and AKT signaling pathways. Next, we investigated in vivo effect of Omniscan in a murine xenograft model of MM. Following detection of tumor, mice were treated with either iv Omniscan or PBS. Treatment with Omniscan significantly induced MM tumor growth compared to control mice (1042 ±243 mm3 vs 502 ±137 mm3 respectively; p=0.0001). Finally in autopsies in 8 MM patients with repeated exposure to Omniscan, we quantified gadolinium in various tissues using Inductively-coupled mass spectrometry. We observed massive quantities of gadolinium accumulation in tissues of these MM patients regardless of their renal function. These results, confirming both in vitro and in vivo growth promoting effects of Gd-containing contrast agent on MM, suggest the need for further analysis of the mechanism of its action on myeloma cells and careful analysis of its clinical impact in MM patients undergoing MRI evaluation. Disclosures No relevant conflicts of interest to declare.

Download Full-text

Promotion of human multiple myeloma cell growth in vitro and bone marrow invasion in vivo by Notch receptors and the CXCR4/SDF1 axis.

Journal of Clinical Oncology ◽

10.1200/jco.2013.31.15_suppl.8591 ◽

2013 ◽

Vol 31 (15_suppl) ◽

pp. 8591-8591 ◽

Cited By ~ 1

Author(s):

Maurizio Chiriva-Internati ◽

Leonardo Mirandola ◽

Elisa Lazzari ◽

Michela Colombo ◽

Marialuigia Lancellotti ◽

...

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Drug Resistance ◽

Cell Growth ◽

Plasma Cells ◽

Myeloma Cell ◽

Notch Receptors ◽

Associated Lesions

8591 Background: Multiple myeloma (MM) originates from post-germinal center B cells, and is caused by malignant plasma cells accumulating in the bone marrow. Interactions of MM cells with the bone marrow stroma promote tumor growth, migration and drug resistance. The chemokine receptor CXCR4 and its ligand SDF1 are critical regulators of this process. MM cells frequently hyper-express CXCR4 and respond to SDF1,2 enhancing MM cell infiltration, proliferation and osteolysis. Notch receptors similarly promote MM cell growth, drug resistance and the associated osteolytic process. We hypothesized that the CXCR4/SDF1 axis mediates the effects of Notch signals in MM. Methods: We used real-time PCR, flow-cytometry, E.L.I.S.A. and chemotaxis assay to explore the effects of CXCR4 in cultured human MM cell lines after Notch inhibition or over-stimulation. Additionally, we validated our findings in a NOD/SCID murine model xenografted with human MM cells. Results: Our results show that Notch blocking reduced CXCR4 and SDF1 expression by MM cells. Further, Notch activation was required for MM cell chemotactic and proliferative response to SDF1 in vitro. We then investigated the outcome of anti-Notch treatment on human MM cells bone invasion in NOD/SCID mice. Interfering with Notch activity dramatically reduced xenografted MM cell ability to infiltrate the bone marrow, ultimately resulting in diminished tumor burden. Notably, such effect was associated with a decrease of CXCR4 expression. Conclusions: This was the first time that Notch receptors were reported to regulate the CXCR4/SDF1 axis and bone marrow invasion in human MM. These findings indicate that specific Notch-tailored therapies may effectively hamper CXCR4-mediated bone infiltration and associated lesions, and are expected to significantly improve treatment outcome and survival.

Download Full-text

APRIL and BCMA promote human multiple myeloma growth and immunosuppression in the bone marrow microenvironment

Blood ◽

10.1182/blood-2016-01-691162 ◽

2016 ◽

Vol 127 (25) ◽

pp. 3225-3236 ◽

Cited By ~ 104

Author(s):

Yu-Tzu Tai ◽

Chirag Acharya ◽

Gang An ◽

Michele Moschetta ◽

Mike Y. Zhong ◽

...

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Drug Resistance ◽

Bone Marrow Microenvironment ◽

Key Points ◽

Human Multiple Myeloma

Key Points APRIL/BCMA activation promotes MM proliferation, survival, and immunosuppression in vitro and in vivo. Targeting the APRIL/BCMA pathway represents a promising mechanism-based immunotherapy to target MM and overcome drug resistance.

Download Full-text

A Deptor Inhibitor Induces Its Degradation with Resulting Anti-Myeloma Cytotoxicity in Vitro and In Vivo

Blood ◽

10.1182/blood-2019-121480 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1821-1821

Author(s):

Mario I Vega ◽

Yijiang Shi ◽

Patrick Frost ◽

Sara Huerta-Yepez ◽

Alan Lichtenstein

Keyword(s):

Multiple Myeloma ◽

Cell Lines ◽

Therapeutic Target ◽

Cytotoxic Effect ◽

Plasma Cells ◽

Conflicts Of Interest ◽

Inhibition Of Proliferation ◽

Induction Of Apoptosis

Multiple myeloma (MM) is a hematological disorder characterized by a proliferation of malignant monoclonal plasma cells in the bone marrow (BM) and / or in extramedullary sites. Despite recent progress in OS rates, MM remains an incurable disease and most patients will relapse and require treatment. Deptor is a component of mTOR complexes and a constitutive inhibitor of their activities. It is known that the inhibition of Deptor results in the inhibition of the proliferation and induction of apoptosis in MM cells. In addition, high levels of Deptor are predictive of a poor response to conventional therapies, indicating that Deptor expression are important as a prognostic marker for patients with myeloma and is a possible therapeutic target. Our group previously identified a drug which prevents mTOR-Deptor binding (NSC126405) and induces cellular cytotoxicity in MM (Shi Y, et al 2016). In this study, we developed a new related chemical inhibitor (43 M) capable of inducing the inhibition of the mTOR / Deptor interaction and results in the negative regulation of Deptor that leads to the inhibition of proliferation and induces apoptosis in several MM cell lines. The cytotoxic effect of 43 M is not dependent of caspase activation and induces the activation of p70 and AKT (T308). This leads to the induction of apoptosis in MM cell lines and tumor cells derived from MM patients. The degradation of Deptor induced by 43 M is dependent on the proteasome complex since it was prevented in the presence of MG132. In vivo, 43 M prevents the expression of Deptor in a xenograft tumor, and delayed tumor growth and interestingly, induces the eradication of tumors in 40% of mice in a murine model of MM, without significant toxic implications. Recent studies show that Deptor expression protects MM cells against Bortezomib treatment, suggesting that anti-Deptor drugs can synergize with proteasome inhibitors (PIs). However, the combination of 43 M + Bortezomib was not synergistic, and was antagonistic in vitro. These results are probably due to the prevention of the proteasomal degradation of Deptor, suggesting a possible use of the 43 M inhibitor in MM in the absence of the current PIs. This study describes for the first time the possible role of Deptor as a therapeutic target using a chemical inhibitor capable of degrading and inducing a cytotoxic effect in MM cell lines. In addition, Deptor is reported as an important therapeutic target in an in vivo MM model. Shi Y, Daniels-Wells TR, Frost P, Lee J, Finn RS, Bardeleben C, Penichet ML, Jung ME, Gera J, Lichtenstein A. Cytotoxic Properties of a DEPTOR-mTOR Inhibitor in Multiple Myeloma Cells. Cancer Res. 2016 Oct 1;76(19):5822-5831 Disclosures No relevant conflicts of interest to declare.

Download Full-text

Clonogenic MM Progenitor Cells Reside In CD19-CD38++ Plasma Cells

Blood ◽

10.1182/blood.v116.21.1897.1897 ◽

2010 ◽

Vol 116 (21) ◽

pp. 1897-1897

Author(s):

Naoki Hosen ◽

Haruo Sugiyama

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

B Cells ◽

Progenitor Cells ◽

Plasma Cells ◽

Conflicts Of Interest ◽

The Other ◽

Xenograft Models ◽

Nog Mice

Abstract Abstract 1897 For effective treatment of multiple myeloma (MM), it is important to identify clonogenic MM progenitor cells and target them. However, it is still controversial where MM progenitor cells reside. It was reported that CD19+ B cells from MM patients generated MM upon transplantation to NOD/SCID mice, while CD19-CD38++ plasma cells generated MM disease in SCID-hu or rab model. In this study, we performed both of those two xenograft models with a series of MM patient samples. To increase engraftment efficiencies, we used highly immuno-deficient NOD/Scid, IL-2Rγnull (NOG) mice as recipients, and cells were injected directly into bone marrow (BM) or intravenously to new born pups. CD19+ cells from 10 MM samples were transplanted, but none of them engrafted in NOG mice. Thus, the significance of CD19+ B cells was unclear in the MM patients examined in this study. On the other hand, in SCID-rab model, CD19-CD38++ plasma cells, but not CD19+ B cells, generate MM disease in 5 out of 13 MM patient samples. In addition, in vitro MM colony-forming cells were highly enriched in CD19-CD38++ plasma cells. Taken together, our results indicate that clonogenic MM progenitors reside in CD19-CD38++ cells and are essential targets to eradicate MM clones. Disclosures: No relevant conflicts of interest to declare.

Download Full-text