scholarly journals Endoplasmic Reticulum Stress is Involved in DFMO Attenuating Isoproterenol-Induced Cardiac Hypertrophy in Rats

2016 ◽  
Vol 38 (4) ◽  
pp. 1553-1562 ◽  
Author(s):  
Yan Lin ◽  
Xiaojie Zhang ◽  
Wei Xiao ◽  
Bo Li ◽  
Jun Wang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Cardiac Hypertrophy ◽  
Western Blot ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Cardiac Fibrosis ◽  
Regulation Of Gene Expression ◽  
Tunel Staining

Background/Aims: Studies performed in experimental animals have shown that polyamines contribute to several physiological and pathological processes, including cardiac hypertrophy. This involves an increase in ornithine decarboxylase (ODC) activity and intracellular polyamines associated with regulation of gene expression. Difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, has attracted considerable interest for its antiproliferative role, which it exerts through inhibition of the polyamine pathway and cell turnover. Whether DFMO attenuates cardiac hypertrophy through endoplasmic reticulum stress (ERS) is unclear. Methods: Myocardial hypertrophy was simulated by isoproterenol (ISO). Polyamine depletion was achieved using DFMO. Hypertrophy was estimated using the heart/body index and atrial natriuretic peptide (ANP) gene expression. Cardiac fibrosis and apoptosis were measured by Masson and TUNEL staining. Expression of ODC and spermidine/spermine N1-acetyltransferase (SSAT) were analyzed via real-time PCR and Western blot analysis. Protein expression of ERS and apoptosis factors were analyzed using Western blot analysis. Results: DFMO treatments significantly attenuated hypertrophy and apoptosis induced by ISO in cardiomyocytes. DFMO down-regulated the expression of ODC, glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), cleaved caspase-12, and Bax and up-regulated the expression of SSAT and Bcl-2. Finally, these changes were partially reversed by the addition of exogenous putrescine. Conclusion: The data presented here suggest that polyamine depletion could inhibit cardiac hypertrophy and apoptosis, which is closely related to the ERS pathway.

scholarly journals Effects of Apoptin-Induced Endoplasmic Reticulum Stress on Lipid Metabolism, Migration, and Invasion of HepG-2 Cells

2021 ◽  
Vol 11 ◽  
Author(s):  
Yilong Zhu ◽  
Yiquan Li ◽  
Bing Bai ◽  
Chao Shang ◽  
Jinbo Fang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Metabolism ◽  
Endoplasmic Reticulum Stress ◽  
Western Blot ◽  
Er Stress ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Migration And Invasion ◽  
Expression Levels

In this study, we investigated the effects of Apoptin-induced endoplasmic reticulum (ER) stress on lipid metabolism, migration and invasion of HepG-2 cells, and preliminarily explored the relationship between endoplasmic reticulum stress, lipid metabolism, migration, and invasion. The effects of Apoptin on ER function and structure in HepG-2 cells were determined by flow cytometry, fluorescence staining and western blotting by assessing the expression levels of ER stress related proteins. The effects of Apoptin on HepG-2 cells’ lipid metabolism were determined by western blot analysis of the expression levels of triglyceride, cholesterol, and lipid metabolism related enzymes. The effects of Apoptin on HepG-2 cells’ migration and invasion were studied using migration and invasion assays and by Western-blot analysis of the expression of proteins involved in migration and invasion. The in vivo effects of endoplasmic reticulum stress on lipid metabolism, migration and invasion of HepG-2 cells were also investigated by immunohistochemistry analysis of tumor tissues from HepG2 cells xenografted nude mice models. Both in vitro and in vivo experiments showed that Apoptin can cause a strong and lasting ER stress response, damage ER functional structure, significantly change the expression levels of lipid metabolism related enzymes and reduce the migration and invasion abilities of HepG-2 cells. Apoptin can also affect HepG-2 cells’ lipid metabolism through endoplasmic reticulum stress and the abnormal expression of enzymes closely related to tumor migration and invasion. These results also showed that lipid metabolism may be one of the main inducements that reduce HepG-2 cells’ migration and invasion abilities.

scholarly journals Long non-coding RNA MALAT1 enhances the apoptosis of cardiomyocytes through autophagy inhibition by regulating TSC2-mTOR signaling

2019 ◽  
Vol 52 (1) ◽  
Author(s):  
Hao Hu ◽  
Jiawei Wu ◽  
Xiaofan Yu ◽  
Junling Zhou ◽  
Hua Yu ◽  
...  
Keyword(s):  
Western Blot ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Noncoding Rna ◽  
Mtor Signaling ◽  
Cardiomyocyte Apoptosis ◽  
Tunel Staining ◽  
Promoter Regions ◽  
Related Proteins ◽  
Autophagy Inhibition

Abstract Background Our previous study showed that knockdown of long noncoding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) attenuated myocardial apoptosis in mouse acute myocardial infarction (AMI). This study aims to explore whether MALAT1 enhanced cardiomyocyte apoptosis via autophagy regulation and the underlying mechanisms of MALAT1 regulating autophagy. Methods Cardiomyocytes were isolated from neonatal mice and then stimulated with hypoxia/reoxygenation (H/R) injury to mimic AMI. The autophagy level was assessed using GFP-LC3 immunofluorescence and western blot analysis of autophagy-related proteins. RNA pull-down and RNA immunoprecipitation (RIP) was performed to analyze the binding of MALAT1 and EZH2. Chromatin immunoprecipitation (ChIP) assay was performed to analyze the binding of TSC2 promoter and EZH2. The cell apoptosis was evaluated using TUNEL staining and western blot analysis of apoptosis-related proteins. Results H/R injury increased MALAT1 expression in cardiomyocytes. Furthermore, MALAT1 overexpression inhibited, whereas MALAT1 knockdown enhanced the autophagy of cardiomyocytes. Moreover, MALAT1 overexpression recruited EZH2 to TSC2 promoter regions to elevate H3K27me3 and epigenetically inhibited TSC2 transcription. Importantly, TSC2 overexpression suppressed mTOR signaling and then activated the autophagy. Further results showed that MALAT1 inhibited proliferation and enhanced apoptosis of cardiomyocytes through inhibiting TSC2 and autophagy. Conclusion These findings demonstrate that the increased MALAT1 expression induced by H/R injury enhances cardiomyocyte apoptosis through autophagy inhibition by regulating TSC2-mTOR signaling.

Secretoneurin is a potential paracrine factor from lactotrophs stimulating gonadotropin release in the goldfish pituitary

2010 ◽  
Vol 299 (5) ◽  
pp. R1290-R1297 ◽  
Author(s):  
E. Zhao ◽  
Caleb L. Grey ◽  
Dapeng Zhang ◽  
Jan A. Mennigen ◽  
Ajoy Basak ◽  
...  
Keyword(s):  
Gene Expression ◽  
Western Blot ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Time Course ◽  
Pcr Analysis ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Paracrine Factor ◽  
Lh Release

Secretoneurin (SN) is a functional neuropeptide derived from the evolutionarily conserved part of precursor protein secretogranin II (SgII). In the time course study, SN (10 nM) stimulates luteinizing hormone (LH) production and secretion after 6 h of static incubation of goldfish pituitary cells. Due to the existence of SN-immunoreactivity (SN-IR) in goldfish lactotrophs, endogenous SN might exert a paracrine effect on LH in the pituitary. In an in vitro immunoneutralization experiment, coincubation with anti-SN antiserum reduces the stimulatory effect of salmon gonadotropin-releasing hormone (sGnRH) on LH release by 64%. Using Western blot analysis, we demonstrate that sGnRH significantly increases the expression of the major SgII-derived peptide (∼57 kDa, with SN-IR) and prolactin (PRL) after 12 h in the static culture of goldfish pituitary cells. Furthermore, there exists a significant correlation between the levels of these two proteins ( R = 0.76, P = 0.004). Another ∼30 kDa SgII-derived peptide containing SN is only observed in sGnRH-treated pituitary cells. Consistent with the Western blot analysis results, real-time RT-PCR analysis shows that a 12-h treatment with sGnRH induced 1.6- and 1.7-fold increments in SgII and PRL mRNA levels, respectively. SgII gene expression was also associated with PRL gene expression ( R = 0.66; P = 0.02). PRL cells loaded with the calcium-sensitive dye, fura 2/AM, respond to sGnRH treatment with increases in intracellular Ca2+ concentration level, suggesting a potential mechanism of GnRH on PRL cells and thus SgII processing and SN secretion. Taken together, endogenous lactotroph-generated SN, under the control of hypothalamic GnRH, exerts a paracrine action on neighboring gonadotrophs to stimulate LH release.

Myc-epitope tagged proteins detected with the 9E10 antibody in immunofluorescence and immunoprecipitation assays but not in Western blot analysis

1998 ◽  
Vol 76 (1) ◽  
pp. 125-128 ◽  
Author(s):  
Huizhou Fan ◽  
Cristy Villegas ◽  
Arthur K Chan ◽  
Jim A Wright
Keyword(s):  
Gene Expression ◽  
Monoclonal Antibody ◽  
Recombinant Protein ◽  
Western Blot ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Immunofluorescence Assay ◽  
Expression Vectors ◽  
Epitope Recognition ◽  
In Cells

A human Myc epitope is frequently used to tag proteins for expression experiments in nonhuman cells. We used the monoclonal 9E10 antibody specific for this epitope to analyse the expression of four proteins carrying the Myc tag in cells transfected with expression vectors. While all four proteins can be detected by immunofluorescence and immunoprecipitation assays, surprisingly, only two proteins could be detected in Western blot analysis, indicating that epitope recognition by the monoclonal antibody can be blocked in some membrane-retained ectopic proteins. Other techniques such as immunofluorescence and immunoprecipitation assays can be successfully used with the 9E10 antibody to determine potential expression of Myc-tagged proteins.Key words: recombinant protein, Myc epitope, 9E10, Western blot, gene expression, immunofluorescence assay, immunoprecipitation.

scholarly journals EfficientIn VitroTRAIL-Gene Delivery in Drug-Resistant A2780/DDP Ovarian Cancer Cell Line via Magnetofection

2011 ◽  
Vol 2011 ◽  
pp. 1-7
Author(s):  
Fang Li ◽  
Sumei Niu ◽  
Jing Sun ◽  
Huaishi Zhu ◽  
Qiujie Ba ◽  
...  
Keyword(s):  
Gene Expression ◽  
Ovarian Cancer ◽  
Western Blot ◽  
Cancer Cells ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Gene Transfection ◽  
Ovarian Cancer Cells ◽  
Drug Resistant

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) presents great promise as an anticancer agent for human cancer therapy. In this study, a magnetofection agent (polyMAG-l000) was evaluated forin vitrodelivery of TRAIL gene towards drug-resistant A2780/DDP ovarian cancer cells. Transfection experiments showed that polyMAG-l000 was able to transfect A2780/DDP cellsin vitro, leading to a higher level of TRAIL gene expression in the presence of a static magnetic field as compared to other transfection agent, such as Lipofectamine 2000. TRAIL gene expression in the A2780/DDP cells was also confirmed by Western blot analysis. Moreover, the TRAIL gene expression exhibited remarkable decrease in the cell viability, as determined by MTT assay. Importantly, PolyMAG-l000-mediated TRAIL gene transfection in the presence of anticancer drug cisplatin (CDDP) induced much higher percentages of apoptotic A2780/DDP cells, compared to TRAIL gene transfection or CDDP treatment alone. A further study by Western blot analysis indicated that cytochromecrelease and caspase-9 cleavage pathway were associated with the initiation of the apoptosis in A2780/DDP cells. The results of this study indicate that polyMAG-l000 can be used as an efficient agent for TRAIL gene transfection in ovarian cancer cells.

Abstract 268: Myofilament Tyrosine Phosphorylation by Src Kinase is upregulated in ErbB2 Transgenic Mice

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Mingguo Xu ◽  
Genaro A Ramirez-Correa ◽  
Zongming Fu ◽  
Polina S Shah ◽  
Frances Belmonte ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Cardiac Hypertrophy ◽  
Western Blot ◽  
Cell Signaling ◽  
Light Chain ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Troponin I ◽  
Src Kinase ◽  
Post Translational Modification

Objectives: Tyrosine (Tyr) phosphorylation of the myofilament is an emerging, and potentially important, post-translational modification in cardiomyopathy. ErbB2, a Tyr receptor kinase, was overexpressed in transgenic mice (ErbB2-Tg) resulting in significant cardiac hypertrophy. We hypothesize that the development of cardiac hypertrophy in ErbB2-Tg is associated with increased myofilament Tyr phosphorylation and may implicate myofilament Tyr phosphorylation in cardiac hypertrophy. Methods: Proteins were isolated from ErbB2-Tg and Ntg heart homogenates ( n =4 per group). Reduction/alkylation was followed by trypsinization. Resulting peptides were desalted in C 18 columns and lyophilized. Phosphorylated Tyr (p-Tyr) enrichment was performed on 20 mg of peptides using a p-Tyr Mouse mAb kit (Cell Signaling). Immuno-precipitated and desalted peptides were analyzed by LC-MS/MS (Orbitrap Elite, Thermo). Raw data were searched with Mascot 2.3. Label-free quantification with MS1 extracted ion chromatograms was performed using Skyline. Western blot analysis for total and phosphorylated Src kinase was performed per manufacturer’s protocol (Cell Signaling). Results: We found a total of 286 p-Tyr modified peptides in ErbB2-Tg compared to 226 in control NTg mice. Over 70 p-Tyr sites on myofilament protein were up-regulated in ErbB2-Tg, including troponin I, myosin heavy chain, titin, α-tropomyosin, myosin-binding protein-C3, myosin regulatory light chain-2 and myosin light chain-1. We used PhosphoMotif Finder to search the potential responsible kinase. Most of the p-Tyr sites were consistent with Src kinase motifs. Furthermore, Western blot analysis showed that total, and phospho-Src (Y416) expression was increased in ErbB2-Tg mice. Conclusion: We concluded that these novel p-Tyr sites on myofilament proteins are increased in ErbB2-Tg mice and correlate with up-regulated Src kinase activity. Thus increased tyrosine myofilament phosphorylation may be involved in the development of cardiac hypertrophy. Since ErbB2 is a therapeutic target of trastuzumab therapy this may also have translational implications to ameliorate off target effects of cancer treatment.

Abstract 352: MicroRNAs Play A Crucial Role In The Induction Of Endothelial-to-Mesenchymal Transition-Mediated Cardiac Fibrosis.

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Varun Nagpal ◽  
Mesut Eren ◽  
Marissa A Michaels ◽  
Douglas E Vaughan
Keyword(s):  
Western Blot ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Human Heart ◽  
Cardiac Fibrosis ◽  
Primary Cultures ◽  
Human Myocardium ◽  
Tgf Beta ◽  
Mesenchymal Transition ◽  
Endothelial To Mesenchymal Transition

Introduction: Fibroblast-like cells derived from aberrant activation of endothelial-to-mesenchymal transition (EndMT) are an important contributor to cardiac fibrosis. TGF-beta signaling plays a pivotal role in the induction of EndMT and cardiac fibrosis. Our recent studies have shown that specific miRNAs are differentially regulated during TGF-beta-induced EndMT and blocking TGF-beta-receptor I (TbetaR1) kinase inhibits TGF-beta-induced EndMT. Hypothesis: We hypothesize that miRNAs that promote EndMT will potentially exacerbate cardiac fibrosis, and knockdown of these miRNAs will attenuate EndMT-mediated cardiac fibrosis. Results and Methods: We investigated the levels of miRNAs and profibrotic markers in the failing human myocardium compared to healthy human heart tissue. Our results indicate that miRNAs upregulated during EndMT were significantly elevated in the failing human myocardium. In addition, failing human myocardium exhibited significant upregulation of profibrotic markers including alpha-SMA, Col1 and PAI-1. Next, primary cultures of mouse cardiac endothelial cells treated with TGF-beta or SB431542 (TbetaR1 kinase inhibitor) were evaluated for EndMT markers using bright field microscopy, fluorescence microscopy, western blot analysis and qRT PCR. We observed that blocking TbetaR1 kinase by SB431542 inhibits specific miRNAs which were upregulated during TGF-beta-induced EndMT. In addition, in silico analysis revealed that these miRNAs target key TGF-beta effectors, which was further confirmed by western blot analysis. Furthermore, overexpression of specific miRNAs using mimics resulted in the induction of EndMT. Next, miRNA mimics in combination with TGF-beta substantially potentiated TGF-beta-induced EndMT. Finally, knockdown of these miRNAs using inhibitors or Cy3-tagged antagomiRs significantly attenuated TGF-beta-induced cardiac EndMT. Conclusions: Our results indicate that TbetaR1 kinase-induced expression of miRNAs is involved in cardiac EndMT. Thus, miRNAs may promote profibrotic signaling in EndMT-derived fibroblast-like cells, which may contribute to fibrogenesis in the human heart.

PIP4KIIα Gene Silencing by Lentivirus-Mediated Delivery of shRNA in Human K562 Cells,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3200-3200
Author(s):  
Tânia Regina Zaccariotto ◽  
Daniela Maria Ribeiro ◽  
Joao Machado-Neto ◽  
Magnun N N Santos ◽  
Carolina Lanaro ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Expression ◽  
Western Blot ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Globin Gene ◽  
K562 Cells ◽  
Globin Genes ◽  
Qrt Pcr ◽  
Globin Gene Expression

Abstract Abstract 3200 Background: Phosphatidylinositol-phosphate-kinase type II alpha (PIP4KIIα) belongs to a family of lipid kinases responsible for the production of a variety of lipid second messengers, such as PI4,5P2 (phosphatidylinositol 4,5-biphosphate), and appears to be implicated in the regulation of gene expression, pre-mRNA processing and mRNA export. In a previous study, two transcripts, PIP4KIIα and β-globin, were found to be overexpressed in reticulocytes from two siblings with Hb H disease, suggesting a possible relationship between this enzyme and the production of globins, particularly β-globin. Recently, we established a gene expression pattern for PIP4KIIα in healthy individuals during in vitro erythropoiesis and observed a gradual increase in the expression of this gene during erythroid differentiation similar to that observed for globin genes, reinforcing the hypothesis of a relationship between PIP4KIIα and globin expression. Aim: To investigate the effects of PIP4KIIα gene silencing on the expression of α- and γ-globin genes in human K562 cells. Methods: Two different human K562 cells cultures were transduced with a lentiviral vector encoding PIP4KIIα-specific shRNA or non-relevant control shRNA. After transduction the positive cells were selected by adding puromycin to the culture and collected 2, 6, 8 and 10 days later to analyze gene and protein expression. PIP4KIIα and α- and γ-globin gene expression was assessed by qRT-PCR and quantified using the equation RQ=2−ΔΔCt. Western blot analysis was performed to determine PIP4KIIα protein expression. β-actin and GAPDH were used as endogenous controls in the qRT-PCR, and β-actin in the Western blot. Results: Analysis of the results showed that there was a statistically significant reduction in PIP4KIIα mRNA levels in knockdown cells (79%) (0.208 ± 0.048; p<0.0001) compared with the control culture. Western blot analysis corroborated these findings. PIP4KIIα silencing resulted in an 18% (0.927 ± 0.244; p=0.09) and 44% (0.625 ± 0.124; p=0.03) reduction in the expression of α- and γ-globin genes, respectively, compared with the control. Conclusion: Although the reduction in α-globin gene expression did not achieve statistical significance, our results revealed alterations in α- and γ-globin gene expression in PIP4KIIα knockdown cells, suggesting a parallelism between the expression of PIP4KIIα and globin genes and reinforcing the hypothesis that the former may be involved in regulation of the latter. This work was supported by FAPESP, CNPq and INCTS. Disclosures: No relevant conflicts of interest to declare.

Abstract 281: Resveratrol Enhances Cholesterol Efflux Through PPAR-γ--Dependent Signaling Pathways in Human Macrophages

2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Ofek Y Hai ◽  
Iryna Voloshyna ◽  
Michael J Littlefield ◽  
Steven Carsons ◽  
Allison B Reiss
Keyword(s):  
Gene Expression ◽  
Western Blot ◽  
Gene Silencing ◽  
Signaling Pathways ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Cholesterol Efflux ◽  
Foam Cell Formation ◽  
Mrna Levels ◽  
Ppar Γ

Introduction: We previously reported that resveratrol, a plant derived polyphenol with numerous cardioprotective properties, improves cholesterol homeostasis by upregulating the expression of reverse cholesterol transport (RCT) proteins critical for preventing lipid overload and macrophage foam cell formation. However, the mechanism(s) by which resveratrol exerts this effect are unclear. The present study explores a possible mechanism for the atheroprotective actions of resveratrol on cholesterol metabolism. Hypothesis: We hypothesize that the anti-atherogenic effects of resveratrol are mediated through PPAR-γ dependent signaling pathways leading to upregulation of RCT proteins and enhanced cholesterol efflux. Methods: THP-1 macrophages, a pertinent model for atherosclerosis, were incubated for 20h with resveratrol (10μM) with/without the specific PPAR-γ antagonist GW6992 (1μM). Alternatively, cells were transfected with 100 nM of human PPAR-γ small interfering RNA (siRNA) for gene silencing prior to resveratrol treatment. Total RNA was isolated, converted to cDNA, and evaluated by QRT-PCR. Each reaction was done in triplicate. Western blot analysis was performed to confirm results of gene expression. Results: Resveratrol significantly increased expression of PPAR-γ, ABCA1, and 27-hydroxylase mRNA (mean±SEM, 136.2±8.5%, 168.3±9.2%, and 171.7±11.0% of control respectively, P<0.001). PPAR-γ gene silencing and PPAR-γ antagonist GW6992 effectively reduced PPAR-γ message by 90.4% and 54.7%, respectively (P<0.001). Both pharmacological blockade and gene knockdown of PPAR-γ nullified resveratrol effects on cholesterol efflux proteins. In cells treated with GW6992, mRNA levels of ABCA1 and 27-hydroxylase were decreased to 66.1±3.3% and 55.0±2.9% of control, respectively (P<0.001). Similarly, PPAR-γ silencing resulted in downregulation of ABCA1 and 27-hydroxylase expression to the level of control, which is significantly lower than in resveratrol treated cells (P<0.001). Data from gene expression studies were subsequently confirmed by Western blot analysis. Conclusions: We propose here a mechanistic model for the atheroprotective effects of resveratrol. Our data strongly suggests that resveratrol regulates cholesterol efflux and intracellular cholesterol processing via the PPAR-γ/LXR-α pathway.

Prima-1Met Combined with Bortezomib Has Synergistic Anti-Myeloma Activity By Modulation of Apoptosis and Cell Cycle Regulating Genes

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4213-4213
Author(s):  
Priya Khoral ◽  
Robert J Guo ◽  
Jahangir Abdi ◽  
Hong Chang
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Western Blot ◽  
Real Time ◽  
Cell Lines ◽  
Blot Analysis ◽  
Drug Combination ◽  
Western Blot Analysis ◽  
Rt Pcr ◽  
Novel Therapeutic

Abstract INTRODUCTION Multiple Myeloma (MM) is a plasma-cell malignancy characterized by dismal prognosis and a high level of relapse, thus novel therapeutic approaches are needed. PRIMA-1Met is a novel small molecule showing anti-tumour activity and currently in clinical phase I-II trials. We recently demonstrated that PRIMA-1Met has potent anti-MM activity in vitro and in vivo. Bortezomib (BTZ) is a proteasome inhibitor that has been successfully used for treating some cases of relapsed MM. The aim of the current study is to determine whether PRIMA-1Met could be used in combination with BTZ to enhance the cytotoxic effects in myeloma cells. METHODS Using three different MM cell lines (LP1, U266 and 8226), we established dose response curves for both PRIMA-1Met and BTZ, and tested drug cytotoxicity using MTT assays. We then tested drug cytotoxicity of a range of concentrations of the drugs in combination. The Chou Talay method was used to determine whether or not the drug combinations were synergistic. A gene expression array was used to investigate the mechanism of the drug combination's effects. Total RNA was isolated from MM cell pellets, then synthesized cDNAs were applied to real time RT-PCR gene expression arrays containing 84 genes of interest. The genes selected were involved in apoptotic as well as cell growth and proliferation pathways. After normalization to 4 different housekeeping genes, fold changes in gene expression were analyzed in both drug treated and control samples using the 2-ΔΔCt algorithm. Western blot analysis was used to further investigate proteins of interest. RESULTS Cell viability of 8226, LP1 and U266 cells treated with individual concentrations of PRIMA-1Met (10uM) and BTZ (10nM) was on average 65%, 45% and 72.5%, respectively. However, combination of above doses reduced viability to 20% in 8226 and LP1, and to 40% in U266. The Chou Talay method identified this drug combination as synergistic in 2 out of the three tested cell lines, with Combination Index (CI) values of 0.72 in 8226 and 0.582 in U266. The gene expression analysis in real time RT-PCR indicated that the drug combination resulted in downregulation of genes involved in cell cycle and proliferation (CCND1, CDK4, CDK6, CDK2, IGFIR), genes from the Bcl-2 family of apoptosis regulation (Bcl-2, Bcl-XL, Mcl-1), as well as MDM2 from the p53 signalling pathway, and MYC, which is involved in both apoptosis and cell cycle progression. Western blot analysis revealed up-regulation of cleaved caspase-3 and -9, implying involvement of the intrinsic apoptotic pathway in the drug combination's activity. CONCLUSION Our results reveal that PRIMA-1Met synergistically enhances the anti-MM effect of BTZ, leading to a significantly higher level of MM cell death. Real time RT-PCR gene array analysis offers some insight into the mechanism of this combination's effect, implicating apoptotic, cell cycle and growth regulating genes. Our study provides framework for further evaluation of this drug combination as a novel therapeutic strategy in MM. Disclosures No relevant conflicts of interest to declare.

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