scholarly journals MLN4924, a Protein Neddylation Inhibitor, Suppresses the Growth of Human Chondrosarcoma through Inhibiting Cell Proliferation and Inducing Endoplasmic Reticulum Stress-Related Apoptosis

2018 ◽  
Vol 20 (1) ◽  
pp. 72 ◽  
Author(s):  
Meng-Huang Wu ◽  
Ching-Yu Lee ◽  
Tsung-Jen Huang ◽  
Kuo-Yuan Huang ◽  
Chih-Hsin Tang ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Endoplasmic Reticulum ◽  
Mouse Model ◽  
Cell Viability ◽  
Er Stress ◽  
Cell Lines ◽  
Cell Cycles ◽  
Chondrosarcoma Cell ◽  
Xenograft Mouse Model ◽  
Human Chondrosarcoma

Chondrosarcoma, a heterogeneous malignant bone tumor, commonly produces cartilage matrix, which generally has no response to conventional therapies. Studies have reported that MLN4924, a NEDD8-activating enzyme inhibitor, achieves antitumor effects against numerous malignancies. In this study, the suppressive effects of MLN4924 on human chondrosarcoma cell lines were investigated using in vitro and in vivo assays, which involved measuring cell viability, cytotoxicity, apoptosis, proliferation, cell cycles, molecule-associated cell cycles, apoptosis, endoplasmic reticulum (ER) stress, and tumor growth in a xenograft mouse model. Our results demonstrated that MLN4924 significantly suppressed cell viability, exhibited cytotoxicity, and stimulated apoptosis through the activation of caspase-3 and caspase-7 in chondrosarcoma cell lines. Furthermore, MLN4924 significantly inhibited cell proliferation by diminishing the phosphorylation of histone H3 to cause G2/M cell cycle arrest. In addition, MLN4924 activated ER stress–related apoptosis by upregulating the phosphorylation of c-Jun N-terminal kinase (JNK), enhancing the expression of GRP78 and CCAAT-enhancer-binding protein homologous protein (CHOP, an inducer of endoplasmic ER stress–related apoptosis) and activating the cleavage of caspase-4. Moreover, MLN4924 considerably inhibited the growth of chondrosarcoma tumors in a xenograft mouse model. Finally, MLN4924-mediated antichondrosarcoma properties can be accompanied by the stimulation of ER stress–related apoptosis, implying that targeting neddylation by MLN4924 is a novel therapeutic strategy for treating chondrosarcoma.

scholarly journals EGFRvIII Promotes Cell Survival during Endoplasmic Reticulum Stress through a Reticulocalbin 1-Dependent Mechanism

Cancers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1198
Author(s):  
Juliana Gomez ◽  
Zammam Areeb ◽  
Sarah F. Stuart ◽  
Hong P. T. Nguyen ◽  
Lucia Paradiso ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Viability ◽  
Er Stress ◽  
Cell Survival ◽  
Glioblastoma Cells ◽  
Over Expression ◽  
Stress Markers ◽  
Apoptotic Protein ◽  
Novel Association ◽  
Reduced Activity

Reticulocalbin 1 (RCN1) is an endoplasmic reticulum (ER)-residing protein, involved in promoting cell survival during pathophysiological conditions that lead to ER stress. However, the key upstream receptor tyrosine kinase that regulates RCN1 expression and its potential role in cell survival in the glioblastoma setting have not been determined. Here, we demonstrate that RCN1 expression significantly correlates with poor glioblastoma patient survival. We also demonstrate that glioblastoma cells with expression of EGFRvIII receptor also have high RCN1 expression. Over-expression of wildtype EGFR also correlated with high RCN1 expression, suggesting that EGFR and EGFRvIII regulate RCN1 expression. Importantly, cells that expressed EGFRvIII and subsequently showed high RCN1 expression displayed greater cell viability under ER stress compared to EGFRvIII negative glioblastoma cells. Consistently, we also demonstrated that RCN1 knockdown reduced cell viability and exogenous introduction of RCN1 enhanced cell viability following induction of ER stress. Mechanistically, we demonstrate that the EGFRvIII-RCN1-driven increase in cell survival is due to the inactivation of the ER stress markers ATF4 and ATF6, maintained expression of the anti-apoptotic protein Bcl-2 and reduced activity of caspase 3/7. Our current findings identify that EGFRvIII regulates RCN1 expression and that this novel association promotes cell survival in glioblastoma cells during ER stress.

Abstract P118: Inhibition of Endoplasmic Reticulum Stress Prevents Intracranial Aneurysmal Rupture in a Mouse Model

Hypertension ◽  
2017 ◽  
Vol 70 (suppl_1) ◽  
Author(s):  
Daisuke Kudo ◽  
Hajime Furukawa ◽  
Satoru Eguchi ◽  
Tomoki Hashimoto
Keyword(s):  
Endoplasmic Reticulum ◽  
Angiotensin Ii ◽  
Mouse Model ◽  
Er Stress ◽  
Intracranial Aneurysms ◽  
Vehicle Group ◽  
Systemic Hypertension ◽  
Aneurysmal Rupture ◽  
Rupture Rate ◽  
Salt Hypertension

Background: Aneurysmal subarachnoid hemorrhage (SAH) can cause significant mortality and morbidity. To develop a therapy for prevention of intracranial aneurysmal rupture and subsequent SAH, it is important to clarify the mechanism of intracranial aneurysmal rupture. Stimulation of the renin-angiotensin system (RAS) causes hypertension and cardiovascular remodeling. Recent evidence shows that angiotensin II enhances endoplasmic reticulum (ER) stress and inhibition of ER stress prevents angiotensin II-induced vascular remodeling but not hypertension in mice. RAS has also been implicated in intracranial aneurysms. We have previously shown that angiotensin II receptor blocker (losartan) prevented intracranial aneurysmal rupture in a mouse model without affecting systemic hypertension. To clarify the mechanism of intracranial aneurysmal rupture via RAS, we have tested our hypothesis that inhibition of ER stress prevents intracranial aneurysmal rupture in a mouse model. Method: We used a mouse model of intracranial aneurysms in which spontaneous aneurysmal rupture causes neurologic symptoms. Intracranial aneurysms were induced in wild type mice by a single stereotactic injection of elastase (35mU) into the cerebrospinal fluid at right basal cistern and deoxycorticosterone (DOCA)-salt hypertension. Vehicle or 4-phenylbutyric acid (PBA, ER stress inhibitor , 100mg/kg/day) was subcutaneously injected into all mice once a day. To detect aneurysmal rupture, we performed daily neurological examinations. Symptomatic mice were euthanized immediately when they developed neurological symptoms, and all asymptomatic mice were euthanized 21 days after aneurysm induction. The incidence of aneurysms and rupture rate were compared between vehicle group and PBA group. Results: The incidence of aneurysms was not significantly different between two groups (100% in vehicle, 20 of 20 vs. 87% in PBA, 20 of 23, p=0.09). However, rupture rate was significantly lower in the PBA group (60%, 12 of 20) than the vehicle group (95%, 19 of 20). (p=0.008). Conclusion: Inhibition of ER stress reduced aneurysmal rupture in a mouse model of intracranial aneurysm induced by combination of elastase injection and DOCA-salt hypertension.

LncRNA PCAT18/miR-301a/TP53INP1 axis is involved in gastric cancer cell viability, migration and invasion

2020 ◽  
Vol 168 (5) ◽  
pp. 547-555
Author(s):  
Jin Dou ◽  
Daoyuan Tu ◽  
Haijian Zhao ◽  
Xiaoyu Zhang
Keyword(s):  
Gastric Cancer ◽  
Cell Proliferation ◽  
Cell Viability ◽  
Cell Lines ◽  
Underlying Mechanism ◽  
Migration And Invasion ◽  
Invasion And Migration ◽  
Proliferation And Metastasis ◽  
And Migration ◽  
Cell Proliferation And Metastasis

Abstract MiR-301a is as an oncogene involved in the regulation of gastric cancer (GC) progression, but the underlying mechanism is unclear. This study was to explore the lncRNA PCAT18/miR-301a/TP53INP1 axis in regulating the GC cell proliferation and metastasis. In the present study, GC tissues and cell lines were collected for the detection of PCAT18 expression. Herein, we found that PCAT18 is significantly decreases in human GC tissues and five GC cell lines. Overexpression of PCAT18 inhibits cell viability, invasion and migration of GC cells and tumour growth of GC xenograft tumours. PCAT18 negatively regulates the expression level of miR-301a. The interaction between PCAT18 and miR-301a is confirmed by RIP and RNA pull down. MiR-301a mimic increases cell viability and promotes cell migration and invasion and reverses the inhibitory action of PCAT18. TP53INP1 expression is negatively regulated by miR-301a and TP53INP1/miR-301a is involved in GC viability, migration and invasion. The promoting of PCAT18 on TP53INP1 expression is abolished by miR-301a overexpression. In conclusion, lncRNA PCAT18 acts as a tumour suppressor for GC and lncRNA PCAT18, miR-301a and TP53INP1 comprise a signal axis in regulating GC cell proliferation, migration and invasion.

scholarly journals Endoplasmic Reticulum Stress Is Involved in Baicalin Protection on Chondrocytes From Patients With Osteoarthritis

Dose-Response ◽  
2018 ◽  
Vol 16 (4) ◽  
pp. 155932581881063 ◽  
Author(s):  
Jiangang Cao ◽  
Yu Zhang ◽  
Tianyi Wang ◽  
Bo Li
Keyword(s):  
Oxidative Stress ◽  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Cell Viability ◽  
Er Stress ◽  
Messenger Rna ◽  
Cell Counting ◽  
Protective Effects ◽  
Gene Expressions ◽  
Protein Levels

Osteoarthritis (OA) affects elderly population worldwide and endoplasmic reticulum (ER) stress is known to be positively correlated with OA development. Previous reports prove the cytoprotective effects of baicalin on chondrocytes, whereas the mechanisms are hardly reported. Hence, we aimed to investigate the links between OA, ER stress, and baicalin. Chondrocytes from patients with OA were subjected to H2O2 treatment with or without baicalin pretreatment, and cell viability was assessed via Cell Counting Kit-8. Messenger RNA (mRNA) amounts of apoptosis-related genes (Bax, Bcl-2, and Caspase-3), extracellular matrix (ECM)-related genes (Collange I, Collange II, Aggrecan, and Sox9) and ER stress hallmarks (binding immunoglobulin protein [BiP] C/EBP homologous protein [CHOP]) were evaluated via quantitative real-time PCR. Bax, Bcl-2, BiP, and CHOP protein levels were analyzed via Western blot. Baicalin suppressed the changes in cell viability and apoptosis-related gene expressions caused by H2O2. Reactive oxygen species and glutathione/oxidized glutathione assay showed that H2O2 enhanced oxidative stress. Baicalin suppressed H2O2-induced downregulation of mRNA expression of ECM-related genes. Moreover, baicalin reduced H2O2-stimulated increase in oxidative stress and the expression of ER stress hallmarks. Endoplasmic reticulum stress inducer abolished the protective activities, whereas ER stress inhibitor did not exhibit extra protective effects. Baicalin pretreatment protected patient-derived chondrocytes from H2O2 through ER stress inhibition.

scholarly journals Endoplasmic reticulum stress regulates cell injury in lipopolysaccharide-induced nerve cells

2020 ◽  
Vol 48 (9) ◽  
pp. 030006052094976
Author(s):  
Min Li ◽  
Ying Zhang ◽  
Jixing Wang
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Viability ◽  
Er Stress ◽  
Cell Apoptosis ◽  
Caspase 3 ◽  
Cell Injury ◽  
Cell Counting ◽  
Tunel Staining ◽  
Dependent Manner ◽  
Stress Markers

Objective Sepsis-associated encephalopathy (SAE) is a common complication of sepsis, and excessive endoplasmic reticulum (ER) stress is closely correlated with the cell injury caused by sepsis. This study aimed to analyze the possible role of ER stress in SAE cell models. Methods PC12 and MES23.5 cells were treated with increasing concentrations of lipopolysaccharides (LPS). The Cell Counting Kit-8 assay was used to detect cell viability and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was performed to assess cell apoptosis. In addition, the protein expression levels of ER stress markers [GRP78, CHOP, inositol-requiring enzyme 1 (IRE1), and PKR-like ER kinase (PERK)] and apoptosis-related proteins (Bax, Bcl-2, caspase-3, and cleaved caspase-3) were analyzed using western blotting. Results LPS treatment activated ER stress markers in both the PC12 and MES23.5 cells. The overexpression of GRP78 significantly reduced cell viability and enhanced cell apoptosis in a time-dependent manner. An ER stress inhibitor, 4-PBA, significantly enhanced cell viability and inhibited the cell apoptosis induced by LPS. Therefore, an enhanced unfolded protein response (UPR) and UPR suppression may regulate cell apoptosis. Conclusions UPR was shown to be involved in regulating LPS-induced neuron injury. UPR could be a potential therapeutic target in SAE.

scholarly journals Akebia trifoliate (Thunb.) KoidzSeed Extract Inhibits the Proliferation of Human Hepatocellular Carcinoma Cell Lines via Inducing Endoplasmic Reticulum Stress

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Wen-Li Lu ◽  
Hong-Yan Ren ◽  
Cao Liang ◽  
Yuan-Yuan Zhang ◽  
Ji Xu ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Main Trend ◽  
G1 Phase ◽  
Cell Viability Assay ◽  
Cell Cycles ◽  
Viability Assay ◽  
M Phase ◽  
Stress Related Genes

Akebia Fructus has long been used for hepatocellular carcinoma (HCC) in China, while the molecular mechanism remains obscure. Our recent work found thatAkebia trifoliate (Thunb.) Koidzseed extract (ATSE) suppressed proliferation and induced endoplasmic reticulum (ER) stress in SMMC-7721. The present study aimed to throw more light on the mechanism. ER stress occurred after ATSE treatment in HepG2, HuH7, and SMMC-7721 cells, manifested as ER expansion, and SMMC-7721 was the most sensitive kind in terms of morphology. Cell viability assay showed that ATSE significantly inhibited cells proliferation. Flow cytometry analysis indicated that ATSE leads to an upward tendency of G0/G1 phase and a reduced trend of the continuous peak after G2/M phase in HepG2; ATSE promoted apoptosis in HuH7 and a notable reduction in G0/G1 phase; ATSE does not quite influence cell cycles of SMMC-7721. Western blot analysis showed an increased trend of the chosen ER stress-related proteins after different treatments but nonsignificantly; only HYOU1 and GRP78 were decreased notably by ATSE in HuH7. Affymetrix array indicated that lots of ER stress-related genes’ expressions were significantly altered, and downward is the main trend. These results suggest that ATSE have anticancer potency in HCC cells via partly inducing ER stress.

Activation of the Endoplasmic Reticulum (ER) Unfolded Protein Response (UPR) in Aggressive B-Cell Lymphomas.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2038-2038
Author(s):  
Olga Balague ◽  
Luis Colomo ◽  
Armando Lopez-Guillermo ◽  
Elias Campo ◽  
Antonio Martinez
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factors ◽  
Western Blot ◽  
Er Stress ◽  
B Cell ◽  
Cell Lines ◽  
Plasma Cell ◽  
Plasma Cells ◽  
Lymphoid Tissues ◽  
B Cell Lymphomas

Abstract BACKGROUND The UPR is a prosurvival pathway activated in cells under ER stress induced by the accumulation of unfolded proteins. UPR activation in B cells normally occurs during the differentiation to antibody secreting plasma cells and requires XBP1activation. XBP-1 is a member of the TREB family of transcription factors that exists in the endoplasmic reticulum (ER) as a 33kDa protein, and in the nucleus as an active 50kDa transcription factor. The UPR stimulates two different ER proteins, ATF-6 and Ire-1, to increase XBP-1 transcription and XBP-1 mRNA splicing resulting in the accumulation of the active 50kDa nuclear protein. Moreover XBP1 is a target of proteosome inhibitors and is related to the aggressive behaviour of some carcinomas. The role of the activation of XBP-1 in lymphomas is still unknown. DESIGN: Reactive lymphoid tissues and 25 neoplastic human B-cell lines representing different stages of B-cell development were studied for XBP-1 expression by western blot and XBP-1, PAX-5, Blimp-1/prdm1, MUM-1/IRF-4 and ICSBP1/IRF-8 by immunohistochemistry. XBP-1 activation was assessed in 225 B-cell lymphomas from the archives of the laboratory of pathology by western blot, RT-PCR and immunohistochemistry . To further evaluate whether XBP-1 activation was related to the plasmacytic program or to ER stress signals we analyzed the cell lines by Western blot for XBP-1 and ATF-6 expression. RESULTS We characterize XBP-1 expression in reactive lymphoid tissues, 25 human cell lines and 225 B-cell tumors. In nearly all tonsillar lymphoid cells XBP-1 was detected as a cytoplasmic protein with a paranuclear dot pattern. Nuclear positivity was observed only in scattered centrocytes in the light zone of the germinal centers and in plasma cells, always coexpressed with plasma cell related transcription factors as MUM-1/IRF-4 and Blimp1/prdm1. Active p50XBP-1 was found in 24/25 cell lines by western blot regardless ATF-6 expression and confirmed by immunohistochemistry . Moreover p50XBP1 was found in 27/31(87%) plasmacytomas, 36/64(56%) DLBCL-ABC and in 3/10(30%) DLBCL-GCB and 22/43(51%) plasmablastic lymphomas. Intriguingly, p50XBP1 was detected also in 2/11(18%)BL and 4/25(16%)MCL with blastic features. CONCLUSIONS.XBP-1 is activated in a subset of follicular centre cells committed to plasma cell differentiation and in plasma cells.UPR prosurvival pathways in the neoplastic cell lines are activated independently of the extent of the ATF-6 activation.p50XBP1 is mostly activated in aggressive B-cell lymphomas regardless to the plasmacytic differentiation of the tumours. Thus, p50XBP-1 may be a new molecular target in the treatment of aggressive B-cell malignancies.

Establishment and Characterization of Bortezomib-Resistant Myeloma Cell Lines: A Possible Role of Mutated Proteasome β5 Subunit in Preventing the Accumulation of Unfolded Protein, Which Is Otherwise Followed by Catastrophic Endoplasmic Reticulum (ER) Stress.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3772-3772
Author(s):  
Masaki Ri ◽  
Shinsuke Iida ◽  
Takayuki Nakashima ◽  
Hideyuki Miyazaki ◽  
Fumiko Mori ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Point Mutation ◽  
Cell Lines ◽  
Binding Pocket ◽  
Protein Accumulation ◽  
Misfolded Protein ◽  
Unique Point ◽  
Resistant Cells

Abstract Abstract 3772 Poster Board III-708 [Purpose] Bortezomib (BTZ), a proteasome inhibitor, has been introduced into the treatment of multiple myeloma (MM). It shows remarkable response against both relapsed/refractory and newly diagnosed MM. However, it is often encountered that BTZ treatment achieves very short duration of response and permits early drug resistance. Therefore, understanding the mechanisms underlying this drug resistance is necessary to develop novel treatments to overcome this problem. [Materials & Methods] We established two stable BTZ-resistant MM cell lines, KMS-11/BTZ and OPM-2/BTZ, whose IC50 values were respectively 24.7- and 16.6-fold higher than their parental cell lines, under continuous exposure to BTZ. Using these resistant cells, we investigated on their proteasome activity, the alteration of proteasome β5 subunit (PSMB5) gene, misfolded protein accumulation, endoplasmic reticulum (ER) stress, and apoptosis signals including BH3 only proteins in comparison with their parental cells at clinically achievable concentration of BTZ treatment. [Results & Discussion] No activation of caspase -3,-8, and -9 and BH3 only protein, Noxa, which were initially up-regulated in BTZ-treated cells, were noted in BTZ-resistant cells even in the presence of BTZ. These results indicate avoidance of fatal intracellular stress may block transcriptional activation of Noxa in resistant cells at an early phase after BTZ exposure. In gel shift assay detecting NF-kB-DNA complexes, BTZ-resistant cells maintained constitutive NF-kB activation, whereas their parental cells lost its activity in the presence of BTZ. In addition, cellular proteasome activities including chymotrypsin-like and caspase-like activity were markedly inhibited by BTZ treatment in parental cells, and moderately also in BTZ-resistant cells, when detected by fluorogenic substrates specific for each proteasome activity. While time-dependent accumulation of ubiquitinated proteins was prevented only in BTZ-resistant cells, but not in their parental cells after BTZ exposure. Resistance was partly explained by the presence of a unique point mutation, G322A, in the gene encoding PSMB5 in both BTZ-resistant cell lines, which substituted Thr for Ala at the codon 49 in amino acid level. This constitution has been reported to gives rise to the conformational change of BTZ-binding pocket in β5 subunit, which results in partial disruption of the contact between BTZ and chymotrypsin-like active site. Furthermore, BTZ-resistant and parental MM cells had nearly equal expression of cytoplasmic and ER chaperons, however, only BTZ-resistant cells could prevent misfolded protein accumulation and therefore avoid fatal ER stress represented as activation of CHOP and of caspase-4, -12 after BTZ treatment. [Conclusion] Two kinds of stable BTZ-resistant MM cell lines were established, which acquired the unique point mutation (G322A) in BTZ-binding pocket of PSMB5, prevented the accumulation of misfolded proteins probably via reduced affinity of 26S proteasome to BTZ and avoided the development of catastrophic ER stress unlike their parental cells. These cell lines will provide better understanding of the underlying mechanisms of the BTZ-resistance, and will lead to the development of novel treatment strategies for overcoming BTZ-resistance in the patients with MM. Disclosures: Iida: JANSSEN PHARMACEUTICAL: Honoraria; KYOWA KIRIN: Research Funding. Nakashima:KYOWA KIRIN: Employment. Miyazaki:KYOWA KIRIN: Employment. Shiotsu:KYOWA KIRIN: Employment.

Anti-Myeloma Effects of the Janus Kinase 2 (JAK2) Inhibitor SAR503 Alone and in Combination Treatment

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4986-4986
Author(s):  
Haiming Chen ◽  
Mingjie Li ◽  
Jennifer Li ◽  
Kevin Delijani ◽  
Danielle Rauch ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Tumor Cell ◽  
Cell Viability ◽  
Tumor Cells ◽  
Cell Lines ◽  
Drug Exposure ◽  
Single Agent ◽  
Janus Kinase ◽  
Gm Csf ◽  
Jak2 Inhibitor

Abstract Abstract 4986 Background: Janus kinase 2 (JAK2) is a cytoplasmic tyrosine kinase that carries out a series of cascading signals via signal transducer and activator of transcription (STAT)s, mitogen-activated protein kinase (MAPK), and phosphorylation of PI3K. Activation of the JAK2 pathway plays an important role in both normal and malignant hematopoiesis. The JAK pathway ha been shown to play a key role in multiple myeloma (MM). JAK2 has been specifically implicated in signaling by members of the type II cytokine receptor family (interferon [IFN] receptor), GM-CSF receptor (IL-3R, IL-5R, and GM-CSF-R), gp130 receptor family interleukin-6 (IL-6R) and single chain receptors (Epo-R, Tpo-R, GH-R, and PRL-R). IFN-α inhibits MM cell proliferation in association with cell cycle arrest at G1 and limits the clonogenic growth of both MM cell lines and primary MM patient specimens. SAR503 (Sanofi-Aventis) is a potent, highly selective JAK2 inhibitor. Thus, we evaluated the anti-MM effects of SAR503 as a single agent and in combination with other anti-MM drugs and evaluated gene and protein expression in MM cells exposed to these drugs. Experiment design: The MM cell lines RPMI8226, U266, and MM1s were cultured in RPMI1640 with standard nutrition supplements. Bone marrow aspirates were obtained from MM patients following informed consent. Bone marrow mononuclear cells (BMMCs) were isolated by using density-gradient centrifugation with Histopaque-1077 (Sigma, St Louis). Cells were plated in 96 well plates at a concentration of 6 × 104 cells/100 ml/well, and incubated for 24 hours prior to drug treatment, after which time the drugs were added in replicates of six for 48 hours. BMMCs were incubated in the presence of media, SAR503, doxorubicin, melphalan, dexamethasone, bortezomib, or IFN-α alone or the combination of SAR503 with one of these anti-MM agents. Following the 48-hour drug incubation, cell viability was assessed utilizing the cell proliferation MTS assay. For gene expression studies, total RNA was isolated MM tumor cells with or without drug exposure. RNA was reverse-transcribed into cDNA and amplified using the Thermo-Script RT-PCR System and PCR performed again using the GeneAmp PCR System 9700. Protein phosphorylation of MM tumor cells with or without drug exposure was determined with Western blot analysis. Results: SAR503 alone inhibited MM tumor cell proliferation in a concentration-dependent fashion. The 50% growth inhibition (IC50) of cells from MM cell lines at 48 hours varied (IC50: RPMI8226 1mM; U266 0. 5mM; MM1s 10mM). IC50 of primary MM tumor cells treated with SAR503 ranged from approximately 5 to 10mM in different patients. Notably, the combination of SAR503 and either doxorubicin or melphalan showed markedly reduced cell viability compared to either drug alone in all three MM cell lines and primary tumor cells from MM patients. Since this effect may have resulted from decreased cell proliferation due to inhibition of the JAK2 pathway and cell cycle arrest or increased cell death, we further determined cell apoptosis of MM tumor cells treated with SAR503 alone by using flow cytometric analysis to detect Annexin V and propidium iodide (PI) staining. Our data showed SAR503 increased MM tumor cell apoptosis in a concentration-dependent fashion. The combination of SAR503 and dexamethasone or bortezomib only slightly reduced tumor cell viability in both MM cell lines and primary MM tumor cells more than single agent treatment, and the combination of SAR503 with IFN-α did not enhance the anti-MM effects compared to single drug treatment. Notably, RT-PCR results showed marked decreases in both AKT1 and mTOR gene expression in MM tumor cells treated with SAR503. Conclusion: The combination of the JAK2 inhibitor SAR503 with doxorubicin or melphalan markedly reduces MM tumor cell viability more than single agent treatment. The results from these studies suggest that enhanced anti-MM activity may be observed when SAR503 is combined with conventional treatment for MM. We are currently evaluating the anti-MM effects of SAR503 in these combination treatments in vivo using our MM xenograft models. Disclosures: Berenson: Onyx: Consultancy, Honoraria, Speakers Bureau.

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