Type I MAGE Proteins: Novel Markers of Proliferation in Multiple Myeloma Progenitor Cells.

Abstract CT7 (MAGE-C1) and MAGE-A3, two members of the type I MAGE family of Cancer-Testis antigens, are commonly expressed at both the mRNA and protein levels in primary tumor specimens from multiple myeloma patients. In previous analyses, tumors with higher percentages of type I MAGE-expressing cells had a positive correlation with abnormally elevated plasma cell proliferation. These data support the hypothesis that type I MAGE proteins are molecular markers of proliferating myeloma progenitor cells (the so-called “myeloma stem cell”) and may play a role in the pathobiology of this disease. To test this hypothesis, we examined the expression of type I MAGE in proliferating myeloma cells by flow cytometry. Human multiple myeloma cell lines U266, RPMI-8226, and KMS-11 were co-cultured for 12 or 24 hours with the nucleoside analog bromodeoxyuridine (BrdU), then fixed, permeabilized, and stained with CT7-33, a monoclonal antibody (mAb) to CT7, or M3H67 (to MAGE-A3), followed by a phycoerythrin (PE)-conjugated secondary mAb. The cells were then treated with DNAse and stained with a fluoroisothiocyanate (FITC)-conjugated mAb against BrdU. Proliferating cells that incorporated BrdU into their DNA exhibited high FITC fluorescence. For mAb M3H67, dual color analysis of this population showed that greater than 99% demonstrated a significant shift in PE fluorescence in all three of these cell lines as measured by Mean Fluorescence Index (MFI= geometric mean fluorescence [specific primary antibody]/mean fluorescence [no primary antibody], table 1). For CT7-33 mAb, greater than 85% demonstrated a shift in two of three lines (U266 and KMS-11), but not in RPMI-8226. For all three of these cell lines, dual color analysis of the BrdU-low population demonstrated less than 65% staining with either type I MAGE mAb. Interestingly, RT-PCR with CT7-specific primers of total RNA from RPMI-8226 revealed a product of lower molecular weight than expected, suggesting that a gene deletion occurred in this cell line possibly resulting in a stop codon, decreased translation, or decreased protein stability. This PCR product is being sequenced to determine the nature of the deletion. These results demonstrate that type I MAGE proteins are expressed in proliferating myeloma cells and are molecular markers of this population. These data suggest that novel therapeutics such as vaccines that target type I MAGE may preferentially eliminate the cycling myeloma cells, resulting in long-term cures. Table 1. Type I MAGE expression in proliferating (BrdU+) myeloma cells Cell line MFI CT7-33 MFI M3H67 U266 65.8 62.5 KMS-11 9.9 48.4 RPMI-8226 3.1 12.3

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Crispr Sgrnas Genome-Wide Screen Identifies the Proteasome Regulatory Subunit PSMC6 As a Bortezomib Resistance Gene in Human Multiple Myeloma Cells

Blood ◽

10.1182/blood.v126.23.450.450 ◽

2015 ◽

Vol 126 (23) ◽

pp. 450-450 ◽

Cited By ~ 1

Author(s):

Chang-Xin Shi ◽

Klaus M Kortum ◽

Yuan Xiao Zhu ◽

Patrick Jedlowski ◽

Esteban Braggio ◽

...

Keyword(s):

Multiple Myeloma ◽

Next Generation Sequencing ◽

Er Stress ◽

Cell Line ◽

Cell Lines ◽

Myeloma Cells ◽

Human Multiple Myeloma ◽

Rpmi 8226 ◽

Generation Sequencing ◽

Specific Inhibitors

Abstract Background: The proteasome inhibitor Bortezomib (BTZ) is an efficient treatment option for both, newly diagnosed and relapsed/refractory multiple myeloma (MM). Despite the effectiveness, most patients eventually acquire drug resistance for reasons not fully understood Materials and methods: To better understand BTZ resistance mechanism we used a CRISPR library (GeCKO V2) targeting 19052 human genes, trying to identify genes responsible for BTZ resistance. CRISPR sgRNAs targeting the ERN1-XBP1 pathway were used as positive controls. We first infected RPMI 8226 myeloma cell line expressing Cas9 with the CRISPR library packaged into lenti-vectors and selected for resistance to BTZ. Surviving cells were subjected to next generation sequencing. Based on the initial screen results we constructed a second CRISPR sgRNA library including 31 genes, each gene targeted with four sgRNAs. After the second round screening and subsequent sequencing, we selected the top 20 genes for individual validation. Results: Proteasome regulatory gene PSMC6 was identified as the only reproducible gene conferring BTZ resistance. Interestingly, the same gene was independently found by a second group using a CRISPR approach (Sheffer M et al. ASH Abstract 273, 2014). Resistance was reproducible using a PSMC6 knockout by three individual CRISPR sgRNAs targeting exonic regions and one pair of SgRNA targeting intron region flanking exon for the deletion of exon one. PSMC6 knockout was verified by PCR and Sanger sequencing. Sensitivity to BTZ was rescued by over expression of PSMC6 cDNA in RPMI 8226 cells harboring a deletion of PSMC6 exon 1. MM cells lacking PSMC6 also developed resistance against Carfilzomib. Resistance was reproduced on a second MM cell line, KMS11. We did not see any significant difference of toxicity in PSMC6 deleted cells for other chemicals tested (tunicamycin, staurosporine, dexamethasone and melphalan). We demonstrated that the sensitivity of chymotrypsin-like activity of proteasome against BTZ was significantly reduced in cells lacking PSMC6. Consequently, MM cells without the PSMC6 gene were relatively resistant to apoptosis induced by BTZ, which was verified by Western blot for caspase 8 degradation and luminescent assay for caspase 3/7 activities. Clinically we could not correlate the PSMC6 expression level with the outcome of BTZ treatment in BTZ naive patients using publically available gene expression data. We initially used CRISPR sgRNAs targeting ER stress pathway (ERN1 and XBP1) as a positive control. However we could not derive any resistant cells from the experiment. We also could not identify any sgRNAs targeting the ERN1-XBP1 pathway from our whole exome screen and next generation sequencing. Since this contradicts published data, we decided to knockout ERN1 and XBP1 genes individually. Clones of cells with successful knockout of ERN1 in three cell lines (RPMI 8226, KMS11 and JJN3) and XBP1 in two cell lines (RPMI 8226 and KMS11) were tested for response to BTZ and Carfilzomib , however we did not find any drug response difference between the knockout and parent cells. We also found that the ERN1-XBP1 knockout cells did not show difference in response to ERN1 specific inhibitors (4u8C and STF-038010) and ER stress inducers (tunicamycin and thapsigargin) compared to parental cells. Conclusions: Human multiple myeloma cells lacking the PSMC6 gene develop significant resistance to apoptosis induced by BTZ. We have however not found a correlation of PSMC6 expression levels with outcome to BTZ treatment in BTZ naïve patients. We are therefore currently investigating the PSMC6 mutation rate in relapsed MM patients after proteasome treatment. In contrast to previous reports showing that progenitor MM cells lacing XBP-1 or ERN-1 invoked BTZ resistance, we were not able to demonstrate a change in sensitivity after full CRISPR knock out of either ERN1 or XBP1. It has long been believed that ERN1-XBP1 pathway plays an important role for MM treatment, leading to the development of ERN1 specific inhibitors. However, we demonstrated that the toxicity of two ERN1-specific inhibitors appears independent of the ERN1-XBP1 pathway. We also demonstrated that the toxicity of two important ER stress inducers, tunicamycin and thapsigargin, is independent of the ERN1-XBP1 pathway. Disclosures Stewart: Celgene: Consultancy; Oncospire Inc.: Equity Ownership; BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy.

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Reduced Response of IRE1α/Xbp-1 Signaling Pathway to Bortezomib Contributes to Drug Resistance in Multiple Myeloma Cells

Tumori Journal ◽

10.5301/tj.5000554 ◽

2016 ◽

Vol 103 (3) ◽

pp. 261-267 ◽

Cited By ~ 4

Author(s):

Xiaoxuan Xu ◽

Junru Liu ◽

Beihui Huang ◽

Meilan Chen ◽

Shiwen Yuan ◽

...

Keyword(s):

Multiple Myeloma ◽

Drug Resistance ◽

Signaling Pathway ◽

Cell Lines ◽

Resistance Mechanism ◽

Proteasome Inhibition ◽

Myeloma Cells ◽

Potential Marker ◽

Rpmi 8226 ◽

Basic Level

Purpose Proteasome inhibition with bortezomib eliminates multiple myeloma (MM) cells by partly disrupting unfolded protein response (UPR). However, the development of drug resistance limits its utility and resistance mechanism remains controversial. We aimed to investigate the role of IRE1α/Xbp-1 mediated branch of the UPR in bortezomib resistance. Methods The expression level of Xbp-1s was measured in 4 MM cell lines and correlated with sensitivity to bortezomib. LP1 and MY5 cells with different Xbp-1s level were treated with bortezomib; then pivotal UPR regulators were compared by immunoblotting. RPMI 8226 cells were transfected with plasmid pEX4-Xbp-1s and exposed to bortezomib; then apoptosis was determined by immunoblotting and flow cytometry. Bortezomib-resistant myeloma cells JJN3.BR were developed and the effect on UPR signaling pathway was determined. Results By analyzing 4 MM cell lines, we found little correlation between Xbp-1s basic level and bortezomib sensitivity. Bortezomib induced endoplasmic reticulum stress-initiated apoptosis via inhibiting IRE1α/Xbp-1 pathway regardless of Xbp-1s basic level. Exogenous Xbp-1s reduced cellular sensitivity to bortezomib, suggesting the change of Xbp-1s expression, not its basic level, is a potential marker of response to bortezomib in MM cells. Furthermore, sustained activation of IRE1α/Xbp-1 signaling pathway in JJN3.BR cells was identified. Conclusions Our data indicate that reduced response of IRE1α/Xbp-1 signaling pathway to bortezomib may contribute to drug resistance in myeloma cells.

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Biochemical Basis for Interactions Between Thalidomide and Inhibitors of the Isoprenoid Biosynthetic Pathway in Multiple Myeloma Cells

Blood ◽

10.1182/blood.v112.11.2635.2635 ◽

2008 ◽

Vol 112 (11) ◽

pp. 2635-2635

Author(s):

Sarah A. Holstein ◽

Huaxiang Tong ◽

Raymond J. Hohl

Keyword(s):

Multiple Myeloma ◽

Cell Lines ◽

Annexin V ◽

Differential Sensitivity ◽

Parp Cleavage ◽

Myeloma Cells ◽

Protein Isoprenylation ◽

Geranylgeranyl Transferase ◽

Synthase Inhibitor ◽

Rpmi 8226

Abstract Introduction: The isoprenoid biosynthetic pathway (IBP) is responsible for the production of key sterol and nonsterol species, including farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) which serve as substrates for protein isoprenylation reactions. Several agents known to target the IBP have been observed to have cytotoxic effects in multiple myeloma cells. Thalidomide (Thal) has emerged as an effective agent for treating multiple myeloma. While Thal has been noted to have a variety of direct and indirect effects on myeloma cells, the precise mechanism of action remains unknown. Aim: We examined interactions between inhibitors of the IBP and Thal in multiple myeloma cells. The mechanisms underlying the observed differential sensitivity to these agents were explored. Methods: Studies were performed in three human multiple myeloma cell lines (RPMI-8226, U266, H929). Cytotoxicity was assessed via MTT assays, while apoptosis induction was determined by Annexin V staining and evaluation of PARP cleavage. Western blot analysis was used to evaluate inhibition of protein isoprenylation. Intracellular FPP and GGPP levels were measured via enzymatic coupling to fluorescently-tagged peptides, HPLC fractionation and fluorescence detection. Pharmacologic manipulation of the IBP was achieved with the following agents: lovastatin (Lov) as an HMG-CoA reductase inhibitor, zoledronic acid (ZA) as a FPP synthase inhibitor, digeranyl bisphosphonate (DGBP) as a GGPP synthase inhibitor, FTI-277 as a farnesyl transferase inhibitor (FTI), and GGTI-286 as a geranylgeranyl transferase I inhibitor (GGTI). Results: Addition of Thal to Lov (at both 24 & 48h), zoledronic acid (at 48h), or DGBP (at 24 & 48h) in RPMI-8266 cells results in marked enhancement in cytotoxicity. Isobologram analysis could not be performed as Thal by itself does induce cytotoxicity in MTT assays. Although Lov induces cytotoxicity in a concentration- and time-dependent manner in the U266 and H929 cells, the addition of Thal did not result in increased cytotoxicity. Neither ZA nor DGBP induced cytotoxicity in the U266 cell line, while the H929 cell line showed effects only at 48 hours. Addition of Thal to FTI or GGTI did not result in enhanced cytotoxicity in tested cell lines. Annexin V experiments confirmed enhanced induction of apoptosis in RPMI-8226 cells incubated with the combination of Thal/Lov or Thal/DGBP. Add-back experiments revealed that the enhanced cytotoxicity/induction of apoptosis observed with the addition of Thal could be prevented with the addition of mevalonate or GGPP in Lov-treated cells or GGPP in DGBP-treated cells. PARP cleavage was demonstrated in RPMI-8226 and H929 cells treated with Lov or DGBP (with or without Thal) and in U266 cells treated with Lov. As expected, Lov resulted in the accumulation of unmodified forms of proteins normally farnesylated (Ras) and geranylgeranylated (Rap1a and Rab6) in these cells. Interestingly however, while DGBP led to accumulation of unmodified Rap1a and Rab6 in RPMI-8226 and H929 cells, no effect was seen in the U266 line. Examination of intracellular levels of FPP and GGPP revealed that the U266 line has markedly larger pools of FPP (8.5-fold) and GGPP (2.7-fold) compared to RPMI-8226 and that treatment with DGBP only partially depletes U266 cells of GGPP. Conclusions: These studies demonstrate an interaction between thalidomide and IBP inhibitors in multiple myeloma cells. These effects appear dependent on depletion of GGPP. Since treatment with a geranylgeranyl transferase-I inhibitor does not produce similar results, this suggests that substrates of geranylgeranyl transferase-II, such as the Rab proteins, may play critical roles in myeloma pathophysiology. The finding that intracellular levels of FPP and GGPP vary markedly amongst cell lines explains differential sensitivity of these cells to pharmacologic manipulation of the IBP and may also influence sensitivity to chemotherapeutic agents. Further studies will determine the extent to which isoprenoid pool sizes vary in primary samples and may ultimately allow for the identification of multiple myeloma patients who would benefit from the addition of an IBP inhibitor to their treatment plan. Figure Figure

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PKC412 Shows Strong Anti-myeloma effects in in-Vitro-Studies

Blood ◽

10.1182/blood.v112.11.5172.5172 ◽

2008 ◽

Vol 112 (11) ◽

pp. 5172-5172

Author(s):

Ahmet H Elmaagacli ◽

Michael Koldehoff ◽

Nina K Steckel ◽

Dietrich Beelen

Keyword(s):

Multiple Myeloma ◽

Mrna Expression ◽

Cell Line ◽

Cell Lines ◽

Interleukin 6 ◽

Proliferation Rate ◽

In Vitro Studies ◽

Apoptosis Rate ◽

Rpmi 8226

Abstract Background. The protein kinase C (PKC) inhibitor PKC412 (N-benzylstaurosporine) is a derivate of the naturally occurring alkaloid staurosproine and has been shown to inhibit the conventional isoforms of PKC (alfa, beta1, beta2 and gamma). PKC412 has been shown to have an antitumor effect on non-small cell lung cancer and acute leukemia with FLT3 mutations, but little is known about its effect on multiple myeloma up to date. Methods. Since PKC is also an inhibitor of a tyrosin kinase which is associated with VEGF, and inhibits the release of Interleukin-6, TNF alfa, and that of growth factor dependent C-FOS, we postulated that PKC412 might have also strong anti-myeloma features. Here we evaluated the anti-myeloma effect of PKC412 in the multiple myeloma cell lines INA-6, OPM-2 and RPMI 8226 by measuring its effect on their proliferation rate, the apoptosis rate and the Interleukin-6 mRNA expression. Results. PKC412 showed strong anti-myeloma effects in all three celllines. 50nM of PKC412 was enough to drop the proliferation rate in all three cell lines under 10% compared to untreated cells(p<0.01). The apoptosis rate increased in INA cell line up to 2,5 times and in RPMI cell line up to 3 times (p<0.05), whereas only a moderate increase was observed in the OPM2 cell line with 500nM of PKC412. As expected, the IL-6 mRNA expression decreased after PKC412 treatment in all three cell lines more than 50%. The addition of Bevacizumab to PKC412 in RPMI and OPM-2 cell lines did not increased the apoptosis rate significantly, whereas the addition of short-interference RNA (RNAi) against VEGF increased the apoptosis rate in RPMI 8226 cells about 20% (p<0.05) and in OPM-2 cells up to 30% (p<0.01) compared to PKC412 alone, which was also associated concordantly with a further reduction of the proliferation rate in RPMI and OPM-2 cells up to 30%. Conclusions. PKC412 shows strong anti-myeloma effects and might be effective also in the treatment of patients with multiple myeloma. These in-vitro studies might encourage to initiate clinical trials with PKC412 in patients with multiple myeloma.

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Dual Antitumoral and Bone Antiresorptive Effect Of The Pan-Pim Kinase Inhibitor, LGH447, In Multiple Myeloma

Blood ◽

10.1182/blood.v122.21.4435.4435 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4435-4435

Author(s):

Teresa Paíno ◽

Antonio Garcia-Gomez ◽

Lorena González-Méndez ◽

Laura San-Segundo ◽

Montserrat Martín-Sánchez ◽

...

Keyword(s):

Multiple Myeloma ◽

Cell Lines ◽

Kinase Inhibitor ◽

Annexin V ◽

Myeloma Cells ◽

Pim Kinases ◽

Castilla Y Leon ◽

Ic50 Values ◽

Rpmi 8226 ◽

Resorptive Activity

Introduction Multiple myeloma (MM) is characterized by the accumulation of malignant plasma cells in the bone marrow (BM) and is closely associated with osteolytic lesions, in part due to an increase in the bone-resorptive activity and number of osteoclasts (OCs). The activation of survival pathways in myeloma cells could be the cause of treatment failure rendering the disease incurable. Pim kinases are a family of survival serine/threonine kinases composed of three members (Pim1, Pim2 and Pim3) that are overexpressed in MM cells and may have a role in MM pathogenesis. However, little is known about the role of Pim kinases in OCs and its involvement in myeloma bone disease. Here, we have evaluated the preclinical activity of a new pan-Pim kinase inhibitor, LGH447, on MM cells and OCs. Cell lines, primary samples, material and methods LGH447 was provided by Novartis Pharmaceuticals. The human MM cell lines MM1S, MM1R, RPMI-8226 (or RPMI-8226-luc), RPMI-LR5, MM144, NCI-H929, OPM-2, U266, U266-Dox4 and U266-LR7 were employed. PBMCs from healthy volunteers were used to generate OCs, whereas primary mesenchymal stromal cells (MSCs) were obtained from bone marrow aspirates of MM patients. Cell viability was studied using MTT colorimetric assay or bioluminescence. Apoptosis was measured by annexin-V staining. For cell cycle analysis, propidium iodide staining was used. OC formation was assessed by enumeration of multinucleated (≥3) TRAP-positive cells and OC resorption was assessed on calcium-coated slides. Immunoblotting, quantitative PCR and immunofluorescence were used to further investigate the mechanism of action of LGH447. Results All MM cell lines expressed the three isoforms of Pim kinases with higher levels of Pim2. The dose-response curves to LGH447 after a 48 hour treatment revealed two groups of MM cell lines with regard to sensitivity to this drug: high sensitive, with IC50 values ranging from 0.2 to 3.3 µM (MM1S, MM1R, RPMI-8226, MM144, U266 and NCI-H929); and low sensitive, with IC50 values >7 µM (OPM-2, RPMI-LR5, U266-Dox4 and U266-LR7). Our results indicated that LGH447 promoted apoptosis in myeloma cells as shown by the increase in annexin-V positive cells and by the cleavage of initiator (caspases 8 and 9) and effector caspases (caspases 3 and 7) and of PARP. LGH447 also blocked the cell cycle in MM cells as demonstrated by the increase in G0-G1 and the decrease in S-G2-M phases. Importantly, LGH447 was also able to overcome the growth advantage conferred to RPMI-8226-luc cells by co-culture with MSCs or OCs. Regarding the mechanisms involved in these effects, LGH447 inhibited the mTOR pathway, demonstrated by a decreased phosphorylation of the downstream mTOR effectors, 4EBP1 and S6 in residues Thr37/46 and Ser235/236, respectively. Interestingly, LGH447 also inhibited OC formation and resorption activity. LGH447 treatment of human pre-OCs diminished the expression of key molecules involved in OC differentiation (p-Erk1/2 and NFATc1) and function [CAII (carbonic anhidrase II), CLCN7 (chloride channel 7), ATP6V1A (vacuolar-H+-ATPase catalytic subunit A1) and MMP9 (matrix metalloproteinase 9)] and also disrupted the F-actin ring necessary for OC effective resorption. Conclusion Overall, our results demonstrate that both MM cells and OCs are targets of the pan-Pim kinase inhibitor, LGH447. Therefore, the inhibition of Pim kinases could potentially provide a dual benefit in myeloma patients as a consequence of cytotoxic effects exerted on MM cells and an anti-resorptive activity on bone. This work was supported by funding from the Fundación Española de Hematología y Hemoterapia (AG-G), Centro en Red de Medicina Regenerativa y Terapia Celular de Castilla y León, the RTICC-Hematology Group (RD12/0036/0058), Spanish FIS (PI12/02591) and the Junta de Castilla y León, Gerencia Regional de Salud (GRS 862/A/13). Disclosures: Off Label Use: LGH447 is a pan-Pim kinase inhibitor (Novartis Pharmaceuticals). It has been used for pre-clinical studies in multiple myeloma.

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YM155 Exerts Potent Cytotoxic Activity Against Quiescent (G0/G1) Multiple Myeloma and Bortezomib Resistant Cells Via Inhibition of Mcl-1 and Survivin

Blood ◽

10.1182/blood.v126.23.3023.3023 ◽

2015 ◽

Vol 126 (23) ◽

pp. 3023-3023

Author(s):

Miyuki Ookura ◽

Tatsuya Fujii ◽

Shinji Kishi ◽

Hiroko Shigemi ◽

Naoko Hosono ◽

...

Keyword(s):

Multiple Myeloma ◽

Protein Expression ◽

Cytotoxic Activity ◽

Cell Line ◽

Cell Lines ◽

Inhibitory Effect ◽

Myeloma Cells ◽

Ic50 Value ◽

Induced Apoptosis ◽

Resistant Cells

Abstract Multiple myeloma (MM) is a molecularly heterogeneous hematologic malignancy and remains mostly incurable despite the recent improvement of treatment strategies by several novel agents. Therefore, it is important to develop more efficacious drug against MM. YM155, a novel small molecule suppressant of survivin, shows anti-proliferative activities against various human cancer cells. YM155 was identified in a survivin gene promoter assay by high throughput screening of chemical libraries. In the present study, we investigated the cytotoxic mechanism of YM155 against human myeloma cells including bortezomib (BTZ) resistant cells (U266/BTZ). Three myeloma cell lines, U266, KMS-11 and KMS-12, were employed. YM155 inhibited the cell growth of these cell lines with the IC50 value of below 5 nM. YM155 suppressed the expression of mRNA and protein of survivin. We also found that YM155 inhibited the protein expression of Mcl-1, as an essential anti-apoptotic protein for survival of myeloma cells. In addition, we observed that YM155 markedly suppressed the phosphorylation of STAT3, which is known as transcription factor of Mcl-1. When KMS-12 cells were incubated with IL-6, phosphorylation of STAT3 and upregulation of Mcl-1 protein were observed. Treatment of KMS-12 with YM155 inhibited these events and eventually induced apoptosis in KMS-12 cells. Interestingly, inhibitory effect of YM155 on Mcl-1 protein expression was much stronger than that on survivin. RQ-PCR analysis indicated that the level of Mcl-1 mRNA was not affected after YM155 treatment. Immunoblot analysis showed that proteasome inhibitor MG-132 blocked the inhibition of Mcl-1 expression by YM155, suggesting that proteasome-mediated degradation is involved in YM155-induced Mcl-1 downregulation. MM is a low-growth-fraction disease and low proliferation of MM seems to contribute to resistance to various anticancer drugs. To determine whether YM155 shows cytotoxic effect against quiescent (G0/G1) MM cells, U266 were cultured in low-serum medium to enrich the G0/G1 population. Dual-parametric flow cytometric analysis using Hoechest33342 and the RNA specific dye pyronin Y revealed that YM155 potently induced cell death of quiescent (G0/G1) MM cells. In quiescent MM cells, inhibitory effect of YM155 on Mcl-1 protein expression was much stronger than that on survivin. We also examined whether similar effect of YM155 could be observed in primary MM cells. The majority of primary MM cells from patients was found to be in quiescent phase by cell-cycle analysis. YM155 showed similar cytotoxic activity against primary MM cells. In contrast, Ara-C, the S-phase specific anticancer drug, never killed quiescent primary MM cells. We established BTZ-resistant MM cell line (U266/BTZ). The IC50 value was 45-fold higher than its parental cell line. DNA sequencing data indicated that U266/BTZ cells possess a point mutation, G322A, in the gene encoding the proteasome beta-5 subunit. YM155 almost equally exhibited cytotoxic activity against U266/BTZ compared with parental cells. U266/BTZ displayed significantly lowered amounts of bcl-2, survivin and aurora-B kinase proteins. Interestingly, U266/BTZ overexpressed the Mcl-1 protein. Treatment with YM155 rapidly suppressed Mcl-1 protein expression and induced apoptosis. These data suggest that overexpression of Mcl-1 may contribute to bortezomib resistance and downregulation of Mcl-1 by YM155 could overcome it. In conclusion, our data indicate that YM155 may exert robust cytotoxic activity against quiescent (G0/G1) MM and bortezomib resistant cells via inhibition of Mcl-1 and survivin. Disclosures No relevant conflicts of interest to declare.

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A Role for Syntenin-1 in Multiple Myeloma Cell Survival

Blood ◽

10.1182/blood-2018-99-113594 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1008-1008

Author(s):

Tyler Moser-Katz ◽

Catherine M. Gavile ◽

Benjamin G Barwick ◽

Sagar Lonial ◽

Lawrence H. Boise

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Cell Death ◽

Cell Survival ◽

Cell Lines ◽

Plasma Cells ◽

Surface Expression ◽

Myeloma Cell ◽

Myeloma Cells ◽

Rpmi 8226

Abstract Multiple myeloma is the second most common hematological malignancy in the U.S. with an estimated 30,700 new diagnoses in 2018. It is a clonal disease of plasma cells that, despite recent therapeutic advances, remains incurable. Myeloma cells retain numerous characteristics of normal plasma cells including reliance on survival signals in the bone marrow for long term viability. However, malignant transformation of plasma cells imparts the ability to proliferate, causing harmful bone lesions in patients, and in advanced stages independence of the bone-marrow microenvironment. Therefore, we are investigating the molecular mechanisms of myeloma cell survival that allow them to become extramedullary. We identified syntenin-1 (SDCBP) as a protein involved in myeloma cell survival and a potential therapeutic target. Syntenin-1 is an adapter protein that has been shown to regulate surface expression of several transmembrane proteins by binding with membrane phospholipids and mediating vesicular trafficking of proteins throughout the cell. Syntenin-1 regulates the surface expression of CD138, a plasma/myeloma cell marker. Syntenin-1 has been shown to regulate apoptosis in numerous cancer cell lines including breast cancer, glioma, and pancreatic cancer but its role in multiple myeloma survival has not been studied. To determine if syntenin-1 expression has an effect on myeloma cell survival, we utilized the CoMMpass dataset (IA12), a longitudinal study of myeloma patients that includes transcriptomic analysis throughout treatment. We found that patients with the highest expression of syntenin-1 mRNA (top quartile) had significantly worse overall survival, progression-free survival, and a shorter response duration than those in the bottom quartile of expression. To determine if syntenin-1 has a role in myeloma cell survival, we used short hairpin RNA to knock down syntenin-1 (shsyn) in RPMI 8226 and MM1.s myeloma cell lines. We then determined the amount of cell death using Annexin-V staining flow cytometry four days following lentiviral infection. We found increased cell death in syntenin-1-silenced cells compared to our empty vector control in both RPMI 8226 (control=42.17%, shsyn=71.53%, p=0.04) and MM1.s cell lines (control=8.57%, shsyn=29.9%, p=0.04) suggesting that syntenin-1 is important for myeloma cell survival. Syntenin-1 contains two PDZ domains that allow it to bind to receptor proteins via their corresponding PDZ-binding motifs. We therefore wanted to look at correlation of syntenin-1 expression with CD138 and CD86, two PDZ-binding domain containing proteins expressed on the surface of myeloma cells. Using the CoMMpass dataset, we found patients with high expression of syntenin-1 had a median expression of CD86 that was twice as high as the total population (P<0.0001) while syntenin-1-low patients expressed CD86 at levels that were half as much as the population (P<0.0001). In contrast, there was no clear relationship between syntenin-1 and CD138 mRNA expression. Indeed if one takes into account all patients, there is a positive correlation between CD86 and syntenin-1 expression (r=0.228, P<0.0001) while there is a negative correlation between CD138 and syntenin-1 (r=-0.1923, P<0.0001). The correlation with CD86 but not CD138 suggests a previously undescribed role for syntenin-1 in myeloma cells. Our lab has previously shown that expression of CD86 is necessary for myeloma cell survival, and signals via its cytoplasmic domain to confer drug resistance. Silencing syntenin-1 results in a decrease in CD86 surface expression. However, there is no change in CD86 transcript or total cellular CD86 protein levels in our shsyn treated cells. Moreover, knockdown of CD86 resulted in increased protein expression and transcript levels of syntenin-1. Taken together, these data suggest that syntenin-1 may regulate CD86 expression on the cell surface. Our data supports a novel role for syntenin-1 in myeloma cell viability and as a potential regulator of CD86 surface expression. The role of syntenin-1 has not previously been explored in multiple myeloma and determining its molecular function is warranted as it may be an attractive target for therapeutic treatment of the disease. Disclosures Lonial: Amgen: Research Funding. Boise:AstraZeneca: Honoraria; Abbvie: Consultancy.

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Sphingolipids as a novel target for the treatment of multiple myeloma.

Journal of Clinical Oncology ◽

10.1200/jco.2013.31.15_suppl.e19534 ◽

2013 ◽

Vol 31 (15_suppl) ◽

pp. e19534-e19534

Author(s):

Yubin Kang ◽

Jagadish Kummetha Venketa

Keyword(s):

Multiple Myeloma ◽

Cell Death ◽

Cell Line ◽

Cell Lines ◽

Apoptotic Cell ◽

Myeloma Cell ◽

Sphingolipid Metabolism ◽

Myeloma Cell Line ◽

Myeloma Cells ◽

Novel Target

e19534 Background: Multiple myeloma (MM) is the second most common hematological malignancy in the United States and accounts for ~10,600 deaths annually. MM remains an incurable disease and almost all patients will eventually relapse and become refractory to currently available therapeutic agents. There is an unmet need for better understanding the disease’s molecular pathways and for identifying novel therapeutic targets. Sphingolipid metabolism is being increasingly recognized as a key pathway in tumor cell proliferation and in tumor sensitivity to anticancer drugs. We hypothesize that altered sphingolipid metabolism plays an important role in the pathogenesis of MM, thus providing a novel target in the treatment of MM. Methods: We first assayed sphingolipid metabolism including sphingolipid metabolites and sphingolipid metabolizing genes in myeloma cell lines, in freshly isolated human primary CD138+myeloma cells, and in publically available dataset. We then tested the efficacy of the selective SK2 inhibitor (ABC294640) and the SK2 shRNA in killing myeloma cells in vitro. Results: 1) Compared to immortalized B cells, the levels of pro-apoptotic ceramides were decreased whereas the proliferative sphingosine 1-phosphate (S1P) was increased in myeloma cell lines. 2) The expression of several key sphingolipid-metabolizing genes including sphingosine kinase (SK) 1 and 2 was altered in freshly isolated human primary bone marrow myeloma cells and in publically available microarray dataset. 3) The selective SK2 inhibitor (ABC294640) induces apoptotic cell death and inhibits myeloma cell growth with an IC50of ~20 μM in 9 myeloma cell lines. 4) Interestingly, OPM-1 myeloma cell line was extremely sensitive to ABC294640 with an IC50of <5 µM whereas U266 myeloma cell line was resistant to ABC294640. SK2 shRNA induced apoptotic cell death in OPM-1, but not in U266 cells. We are currently investigating the molecular mechanisms underlying the resistance of U266 myeloma cells to ABC294640. Conclusions: Our data demonstrated that sphingolipid metabolism provides an attractive target in the treatment of refractory/relapased multiple myeloma.

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Efficacy Of ABT-199 In Multiple Myeloma

Blood ◽

10.1182/blood.v122.21.4453.4453 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4453-4453 ◽

Cited By ~ 1

Author(s):

Shannon M. Matulis ◽

Cathy Sharp ◽

Ajay K. Nooka ◽

Jonathan L. Kaufman ◽

Sagar Lonial ◽

...

Keyword(s):

Multiple Myeloma ◽

Cell Line ◽

Cell Lines ◽

Research Funding ◽

Plasma Cells ◽

Survival Rates ◽

Specific Inhibitor ◽

Small Subset ◽

Potent Inducer ◽

Myeloma Cells

Great strides have been made in the last 15 years in the treatment of multiple myeloma, with FDA approval of both IMIDs and proteasome inhibitors, 10-year survival rates are now achievable in around 25% of patients. However, for the remaining 75%, disease relapse due to drug resistance remains a significant clinical concern. Therefore novel therapeutic approaches to be used in combination with the current active agents are required. The Bcl-2 family of proteins regulates apoptosis and presents an exciting target for therapy. We have demonstrated that myeloma cell lines can be dependent on the anti-apoptotic protein Mcl-1 or can be co-dependent on Mcl-1 and Bcl-2/xL for survival. The distinction between Mcl-1 dependence and co-dependence is the distribution of the pro-apoptotic BH3-only protein Bim. In Mcl-1-dependent lines, Bim is primarily associated with Mcl-1. In contrast in the co-dependent lines, Bim is either predominately associated with Bcl-2/xL or when it is released from Bcl-2/xL it cannot bind to Mcl-1 because of the presence of the Mcl-1 inhibitor, Noxa. This renders these cells sensitive to the Bcl-2/xL inhibitor ABT-737. We have confirmed these findings in freshly isolated patient samples and demonstrated that among the 5 patient samples tested, Bim was associated with both Mcl-1 and Bcl-xL and the cells were sensitive to ABT-737. This suggests that co-dependence on Mcl-1 and Bcl-2/xL may be a common phenomena in myeloma. However, given the adverse effects seen with Bcl-xL inhibition, ABT-737 or the related compound Navitoclax may be difficult to use for the treatment of multiple myeloma. However, ABT-199, a Bcl-2-specific inhibitor, has been developed and we report on preclinical testing in multiple myeloma. Freshly isolated plasma cells from 3 myeloma patients were treated with either ABT-737 or ABT-199 for 24 h and IC50s for each drug were compared. In each patient sample, the plasma cells were less sensitive to ABT-199 than to ABT-737 (MM49: 199 IC50 1.4 μM vs. 737 IC50 0.9 μM; MM51: 199 IC50 0.34 μM vs. 737 IC50 0.07 μM; MM52: 199 IC50 1.3 μM vs. 737 IC50 0.25 μM), and only MM51 was truly sensitive to ABT-199. CoIP studies in MM51 revealed very little Bim bound to Mcl-1 and none bound to Bcl-xL, suggesting the majority of the Bim present in the cell must be bound to Bcl-2. These data suggest that myeloma cells are more likely to be co-dependent on Mcl-1 and Bcl-xL for survival than Mcl-1 and Bcl-2. However Bcl-2 dependence can exist in myeloma. We also performed dose curves in 4 multiple myeloma cells lines, representing 4 different Bim binding patterns and sensitivity to ABT-737. 8226, MM.1s, and KMS18 are all co-dependent cell lines (sensitive to ABT-737), while KMS11 is Mcl-1 dependent. Of these cell lines, KMS18 is the only one with the majority of Bim bound to Bcl-2, therefore should be sensitive to ABT-199. Surprisingly this was not the case. 8226 was the only cell line that was sensitive to ABT-199 (IC50 2.2 μM), while MM1.s, KMS18, and KMS11 were insensitive with IC50s of 6.2 μM, 6.8 μM, and 24.7 μM respectively. In order to gain a mechanistic understanding of these data, we performed CoIP studies to determine the pattern of Bim binding to Mcl-1, Bcl-xL, and Bcl-2 following treatment with ABT-199. We found in KMS18 cells, upon treatment, Bim is released from Bcl-2 and bound by Mcl-1 thereby preventing apoptosis. We have already demonstrated that very little Bim is bound to Bcl-2 in KMS11 and MM.1s, which is consistent with the lack of sensitivity in these cell lines. However in 8226 cells, the high expression of Noxa prevents the Bim released from Bcl-2 from binding to Mcl-1, thereby promoting apoptosis. Silencing of Noxa in this cell line raises the IC50 of ABT-199 2-fold. Next we investigated the effectiveness of combining ABT-199 with the proteasome inhibitor carfilzomib, which has been shown to be a potent inducer of Noxa. A synergistic response to this drug combination was seen in KMS18 cells. CoIP studies revealed that in the presence of Cz, the Bim released from Bcl-2 by ABT-199 could no longer bound to Mcl-1, and was free to activate Bak and Bax. Only additive responses were seen in 8226, MM.1s and KMS11 cell lines. Taken together these data suggest ABT-199 alone may only be an effective treatment for multiple myeloma in a small subset of patients. However, combining it with either Noxa inducers or Mcl-1 inhibitors could be a promising approach for the treatment of this disease. Disclosures: Kaufman: Jansenn: Consultancy; Millennium Pharmaceuticals: Consultancy; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Onyx: Consultancy; Merck: Research Funding. Lonial:Millennium: Consultancy; Celgene: Consultancy; Novartis: Consultancy; BMS: Consultancy; Sanofi: Consultancy; Onyx: Consultancy. Boise:Onyx Pharmaceuticals: Consultancy.

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Analysis of Intratumor Heterogeneity in Multiple Myeloma Using Methylcellulose Clonogenic Assays.

Blood ◽

10.1182/blood.v104.11.2346.2346 ◽

2004 ◽

Vol 104 (11) ◽

pp. 2346-2346

Author(s):

Bonnie K. Arendt ◽

Raphael Fonseca ◽

Gregory Ahmann ◽

Diane F. Jelinek

Keyword(s):

Multiple Myeloma ◽

Cell Growth ◽

Cell Line ◽

Cell Lines ◽

Growth Regulation ◽

Myeloma Cell ◽

Intratumor Heterogeneity ◽

Parental Cell Line ◽

Myeloma Cells ◽

Igf I

Abstract Multiple myeloma (MM) is a fatal disease characterized by the accumulation of malignant plasma cells in the bone marrow. Although progress has been made in better understanding growth control of this disease, effective treatment of MM patients with this disease is likely complicated by the extensive patient to patient variability that exists, as well variability within the tumor population itself. Thus, there is abundant evidence that intraclonal or intratumor heterogeneity exists in myeloma as revealed by morphologic and phenotypic heterogeneity in primary myeloma cells isolated from a single patient. We have had a long-standing interest in the growth regulation of myeloma cells and have hypothesized, along with other investigators, that there may only be a subset of myeloma cells that exhibits extensive proliferative potential. Understanding how cellular compartments within the malignant clone, as defined by identical immunoglobulin variable region sequence, may vary in growth regulation properties in isolation or in the company of less proliferative tumor cell subsets is key to understanding disease progression and how to better target the putative proliferative subset in myeloma. In this study, we have used a methylcellulose clonogenic assay to study intraclonal heterogeneity in a panel of human MM cell lines. Each of these cell lines, DP-6, KAS-6/1, KP-6, and, exhibit a variable response to IL-6 and IGF-I, and our goal was to evaluate growth responsiveness of individual subclones from each of these cell lines. Myeloma cell lines were plated at a concentration of 200-1000 cells in 1 ml Methocult H4533 in 35 mm gridded dishes with or without various cytokines. Following 3 weeks of culture, colonies were scored and those consisting of >40 cells were isolated, expanded, and studied further. Of interest, subclones isolated from each of the cell lines displayed significant differences in growth response to various cytokines in addition to specific morphologic and phenotypic differences. In this regard, results emerging from the DP-6 cell line were particularly intriguing. We have previously shown that the DP-6 cell line displays a proliferative response to both IL-6 and IGF-I and expresses autocrine IL-6 at a low level. Analysis of the growth properties of individual DP-6 clones revealed the existence of DP-6 cells (clone 1-15) that proliferate at a rapid rate in the apparent absence of exogenous growth factors. Whereas a neutralizing antibody to IL-6 did not inhibit cell growth, addition of a blocking antibody to the IGF-IR, (αIR3), completely blocked growth factor independent proliferation. Phenotypic analysis also displayed variation between the parental cell line and its subclone. For instance, the parental DP-6 cells largely expressed CD45 at a high level, whereas the clone 1-15 did not. Finally, we have also further characterized MM cell line subclones by gene profiling and FISH (fluorescence in situ hybridization) analysis to link specific phenotype and genotypes with patterns of cell growth. These results provide additional evidence that intratumor heterogeneity exists in myeloma. These studies further demonstrate how growth regulation may vary considerably among cellular subsets of the malignant population. Understanding what factors regulate the balance of specific myeloma cell subpopulations is key to an understanding of tumor progression. In summary, these studies provide a necessary foundation for future studies of the growth potential of subsets found in primary MGUS, SMM and MM patient samples.

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