P169 SEXUAL HORMONE AND INSULIN RECEPTORS IN CHONDROCYTE CELL LINES C28/12 AND T/C-28a2 ANALYZED BY WESTERN BLOT AND RT-PCR

Abstract The tyrosine kinase pp60src is involved in several signal transduction pathways such as signalling of hematopoetic growth factors and cytokines. The viral form v-src was the first oncogene described and mutations of regulatory tyrosine residues in cellular src (c-src) have been linked to malignant transformation. However, no mutations in the gene of c-src have been described in leukemia so far, although some data of src mutations in solid tumors have been reported. The current study was undertaken to examine the role of src in acute myeloid leukemia (AML). Blood and bone marrow specimen of patients with newly diagnosed or recurrent AML treated at our institution were sampled. AML cell lines or CD34 positive cells of healthy donors served as positive and negative controls, respectively. RNA was isolated, and RT-PCR was performed using 4 different primer pairs spanning the coding region of c-src. Protein expression and phosphorylation was studied after protein extraction and Western blot analyses using src and phospho-src specific antibodies. The effect of src inhibitors PP1 and PP2 on leukemic cell proliferation was studied in human and murine cell lines. Mutational analyses of the coding region were performed using SSCP/heteroduplex and bi-directionally sequencing. In all 60 patients analyzed expression of c-src mRNA was detected by RT-PCR. Western blot analyses confirmed strong expression of src on the protein level and revealed a robust activation of the protein as determined by tyrosine phosphorylation. Inhibition of src phosphorylation by src-specific inhibitors PP1 and PP2 was detected by Western blot using an antibody specific for phospho-src. Incubation of leukemic cells with PP1 and PP2 caused significant inhibition of proliferation in a dose dependent manner. Mutational analyses as performed by SSCP/heteroduplex and bi-directionally sequencing revealed wildtype sequence in all cell lines and 60 clinical samples. In summary, pp60src is highly expressed and activated in cell lines and clinical samples of human AML. Moreover, phosphorylation of src is essential for leukemic cell proliferation. Mutations in the coding sequence of c-src causing constitutive activation could be excluded by mutational analyses of primary AML samples. These data suggest that pp60src plays a crucial role in AML and src inhibition by targeted therapy might offer a useful new approach in the treatment of AML.

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Abnormal Expression of TRAF Adapter Proteins in Waldenstrom’s Macroglobulinemia.

Blood ◽

10.1182/blood.v108.11.4640.4640 ◽

2006 ◽

Vol 108 (11) ◽

pp. 4640-4640

Author(s):

Xavier Leleu ◽

Lian Xu ◽

Zachary R. Hunter ◽

Anne-Sophie Moreau ◽

Xiaoying Jia ◽

...

Keyword(s):

Western Blot ◽

Cell Lines ◽

Blot Analysis ◽

Western Blot Analysis ◽

Low Grade ◽

Adapter Proteins ◽

Rt Pcr ◽

Growth And Survival ◽

Healthy Donors ◽

Sirna Knockdown

Abstract Background: Waldenström’s Macroglobulinemia (WM) is an incurable low-grade lymphoplasmacytic lymphoma with as yet unknown genetic basis for its pathogenesis. Several TNF family members (CD40L, APRIL and BAFF/BLYS) are known to regulate WM growth and survival. TRAFs are a novel family of adapter proteins that facilitate pro-apoptotic (TACI) or pro-survival/differentiation (CD40, BAFFR, BCMA) receptor signaling mediated by TNF family ligands. Therefore, understanding the TRAF system in WM may yield important clues about WM growth and survival. Methods: WM cell lines (BCWM.1 and WSU-WM), IgM secreting low-grade lymphoma cell lines (MEK1, RL, Namalwa), and primary bone marrow CD19+ selected lymphoplasmacytic cells (LPC) from 20 WM patients and 6 healthy donors were evaluated for TRAF (TRAF 2, 3, 5, 6) expression using semi quantitative RT-PCR and/or western blot analysis. Results: The TNF familiy receptors CD40, BAFFR, BCMA, and TACI were expressed in all cell lines tested as well as in CD19+ selected LPC from WM patients and healthy donors. Moreover, TRAF 2, 3, 5, 6 were expressed in all cell lines by both RT-PCR and western blot analysis. In contrast, we observed loss or abnormally low expression of both TRAF 2 and 5 in 6/20 (30%) patients, whilst TRAF 3 was absent or abnormally low in 3/30 (15%) patients. TRAF 6 was expressed in all patients. Among healthy donors, we observed expression of all TRAF adapter proteins. Conclusion: Up to one third of WM patients demonstrate loss of TRAF 2 and 5 adapter proteins which facilitate signaling through the pro-apoptotic receptor TACI. Ongoing studies including gene sequencing and siRNA knockdown models are delineating a role for TRAF loss in the pathogenesis of WM.

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Exploration of the Hsa-miR-1587–Protein Interaction and the Inhibition to CASK

International Journal of Molecular Sciences ◽

10.3390/ijms221910716 ◽

2021 ◽

Vol 22 (19) ◽

pp. 10716

Author(s):

Lulu Zhang ◽

Jiang Zhou ◽

Ming Xu ◽

Gu Yuan

Keyword(s):

Western Blot ◽

Cell Lines ◽

Protein Interaction ◽

Bioinformatic Analysis ◽

Rt Pcr ◽

Multiple Cancer ◽

Quadruplex Structure ◽

Physiological Processes ◽

G Quadruplex ◽

New Strategy

Hsa-miR-1587 has been found to be capable of forming G-quadruplex structures and is overexpressed in multiple cancer cell lines. Here, we explored the interactions between miR-1587 and proteins. HuProt™ human proteome microarray was utilized to screen the binding proteins, and it was discovered that CASK could bind to miR-1587 on the base of the G-quadruplex structure. Moreover, reelin and p21, which are downstream of CASK, were downregulated both transcriptionally and translationally by miR-1587, uncovered by q-RT-PCR and Western blot assays. Bioinformatic analysis was performed on STRING and Panther platforms, leading to the discovery that miR-1587 may be involved in intracellular metabolic and transcriptional physiological processes. This study explores the interaction of hsa-miR-1587 with proteins and provides a new strategy for the regulation of G-rich microRNA’s function.

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Osteonectin/SPARC Is Epigenetically Silenced in AML with MLL Gene Rearrangements and Selectively Inhibits the Growth of MLL Rearranged Cell Lines.

Blood ◽

10.1182/blood.v104.11.1106.1106 ◽

2004 ◽

Vol 104 (11) ◽

pp. 1106-1106

Author(s):

Jorge F. DiMartino ◽

Norman J. Lacayo ◽

Marie Varadi ◽

Yaddanapudi Ravindranath ◽

Ron Yu ◽

...

Keyword(s):

Gene Expression ◽

Pancreatic Cancer ◽

Western Blot ◽

Cell Lines ◽

Chromatin Remodeling ◽

Promoter Methylation ◽

Rt Pcr ◽

Growth And Survival ◽

Mll Gene ◽

Sparc Expression

Abstract Transcriptional repression by chimeric transcription factors is emerging as a common theme in leukemogenesis and as a therapeutic target for chromatin remodeling agents. We hypothesized that rearrangements involving the MLL gene result in the inappropriate silencing of growth and survival control genes subordinate to this positive epigenetic transcriptional regulator. To identify some of these genes, we used Significance Analysis of Microarrays (SAM), a supervised learning algorithm. We found significant gene expression differences between 13 patients with MLL translocations and 12 core binding factor (CBF) rearranged patients, 2 t(8;21), 10 INV16, from a Pediatric Oncology Group AML study (POG 9421). We also analyzed gene expression data from a published study of adult AML including 8 MLL rearranged patients, 11 with t(8;21) and 15 with INV16. SAM identified 10 genes, common to both datasets, that were significantly under-expressed in the MLL rearranged patients. One of the most significant genes was osteonectin, also known as secreted protein, acidic, rich in cysteine (SPARC). This gene encodes a matricellular glycoprotein with diverse functions in cell-matrix interactions. SPARC has been identified as a target of epigenetic silencing in pancreatic cancer and addition of exogenous SPARC to cancer cell lines induces growth arrest and apoptosis. To determine if leukemia cell lines could be used as a model to study the basis for SPARC silencing and its role in cell growth and survival we measured SPARC expression in AML cell lines with rearranged and germline MLL genes. By real-time quantitative reverse transcriptase PCR (Q-RT-PCR), the cell lines THP-1 (MLL-AF-9) and ML-2 (MLL-AF6) expressed SPARC mRNA levels 40 to 1000 fold lower than Kasumi-1 (t(8;21)) and KG1a. By Western blot, SPARC was easily detectable in Kasumi-1 and KG1a but undetectable in the MLL rearranged lines. Bisulfite sequencing revealed extensive methylation of CpG dinucleotides in the promoter region and first exon of SPARC in THP-1 and ML-2 but a complete lack of methylation in KG1a. Treatment with the DNA methyltransferase inhibitor 5-aza-2′deoxycytidine (DAC) restored SPARC expression to nearly normal levels in THP-1 cells by Q-RT-PCR and Western blot, suggesting that promoter methylation is critical to the silencing of this gene. To determine if SPARC was contributing to the growth inhibitory effect of DAC, cells were cultured in varying concentrations of exogenous purified SPARC. Concentrations of SPARC that reduced the growth of ML-2 and THP-1 by 30 to 40% had no effect on the growth of KG1a cells. We conclude that SPARC, a putative tumor suppressor that is epigenetically silenced in pancreatic cancer, is also silenced by promoter methylation in AML with MLL rearrangements. These studies suggest that SPARC expression may constitute a reliable pharmacodynamic endpoint for clinical studies of chromatin remodeling agents in patients with MLL rearranged AML. Whether SPARC is a direct target of MLL and how MLL rearrangements are related to SPARC silencing are the subject of future studies.

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

Blood ◽

10.1182/blood.v126.23.4213.4213 ◽

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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The tyrosine kinase src plays a crucial role in leukemic cell proliferation in AML

Journal of Clinical Oncology ◽

10.1200/jco.2007.25.18_suppl.10531 ◽

2007 ◽

Vol 25 (18_suppl) ◽

pp. 10531-10531

Author(s):

G. Schuch ◽

E. Schäfer ◽

K. Eggert ◽

S. Loges ◽

M. Görn ◽

...

Keyword(s):

Cell Proliferation ◽

Western Blot ◽

Cell Lines ◽

Crucial Role ◽

Leukemic Cell ◽

Leukemic Cells ◽

Clinical Samples ◽

Dependent Manner ◽

Rt Pcr

10531 Background: Src-family tyrosine kinases are known to be involved in signal transduction pathways of growth factors and cytokines in hematopoetic cells. While the role of other src family members has been studied widely, only few data exist about c-src in leukemia. The actual study was performed to analyze src mutations in leukemic cells and to determine the role of pp60src in leukemic cell proliferation. Methods: AML cell lines and primary samples were analyzed for expression and activation of src by RT-PCR and Western blot analyses. Mutational analyses were performed by sequencing of C-terminal cDNA from 60 AML samples. The effects of src inhibition were studied by src-specific inhibitors PP1 and PP2 or by siRNA transfection. Effetcs of src inhibition were monitored in proliferation assays and analyzes of signalling through Erk1/2 and apoptosis by annexin V staining and DNA laddering. Results: In all 60 patients analyzed expression of c-src mRNA was detected by RT-PCR. Western blot analyses confirmed strong expression of src on the protein level and revealed a robust activation of the protein as determined by tyrosine phosphorylation. Incubation of leukemic cells with PP1 and PP2 caused significant inhibition of proliferation in a dose dependent manner. Similar results were observed after transfection with specific siRNAs. Src inhibition blocked phosphorylation of pp60src, Erk1/2 and induced apoptosis in leukemic cells. Mutational analyses as performed by SSCP/heteroduplex and bi-directionally sequencing revealed wildtype sequence in cell lines and 60 clinical samples. Conclusions: In summary, pp60src is highly expressed and activated in cell lines and clinical samples of human AML. Moreover, phosphorylation of src is essential for leukemic cell proliferation. Underlying mutations in the coding sequence of c-src causing constitutive activation could be excluded. These data suggest that pp60src plays a crucial role in AML and src inhibition by targeted therapy might offer a useful new approach in the treatment of AML. No significant financial relationships to disclose.

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MEK 1/2 Inhibitor U0126 Reversed Imatinib Resistance in IM-Resistant K562R

Blood ◽

10.1182/blood.v120.21.4914.4914 ◽

2012 ◽

Vol 120 (21) ◽

pp. 4914-4914

Author(s):

Yuping Gong ◽

Juan Lin ◽

Ting Niu

Keyword(s):

Western Blot ◽

Cell Line ◽

Signaling Pathway ◽

Cell Lines ◽

Mtt Assay ◽

K562 Cell ◽

Single Agent ◽

Rt Pcr ◽

Imatinib Resistance ◽

Ic50 Values

Abstract Abstract 4914 Objective To study the anti-leukemic activity of MEK inhibitor U0126 alone or in combination with imatinib and explored the reversing mechanism to imatinib resistance in imatinib resistant K562R cell line. Methods Cytotoxicity of drug was detected by the MTT assay in the IM-sensitive cell line K562 and IM-resistant cell line K562R. Western Blot assay were employed to examine the expression of p-cAbl, p-Lyn, p-STAT5, ERK signaling pathway (p-cRaf, p-MEK, p-ERK), PI3K/AKT/mTOR signaling pathway(p-AKT, p-mTOR, p-4EBP1) and the apoptosis related proteins (Bax, Bcl2). The apoptosis rates were analyzed by Annexin V/PI double staining flow cytometry assay. The levels of lyn and erk1/2 gene were assayed by RT-PCR. Results 1. BCR-ABL-independent activation of Lyn and ERK1/2 may be the IM resistant mechanism in K562R cell line. The IC50 value of K562R cell line(1. 505±0. 459 μmol/L) inhibited by imatinib for 72 hours was higher than the values of K562(0. 159±0. 032μmol/L) and the Resistant Fold(RF)was 9. 465. Western Blot assays showed that p-Lyn, p-MEK and p-ERK of ERK pathway, p-mTOR and p-4EPB1 were over-expressed in K562R cell line relative to K562 cell line. However, the levels of p-cAbl, p-STAT5, p-Raf, p-AKT of PI3K/AKT/mTOR were similar in the K562R and K562 cell lines. The treatment of IM could reduce the expression of p-cAbl and p-MEK, but not that of p-Lyn, p-ERK, p-mTOR, p-4EBP1, and even up-regulate the p-Lyn, p-ERK, p-mTOR. The expression of Bax, Bcl2 and the apoptosis rates were the similar in both cell lines. 2. MEK1/2 inhibitor U0126 could reverse the IM resistance in K562R cell line. MTT assay showed single-agent U0126 is more sensitive to K562R than K562. The IC50 values of the two cell lines were 34. 235±5. 658 μmol/L and 85. 824±4. 474 μmol/L respectively. The combination of imatinib and U0126 markedly enhanced inhibitory effect as measured by MTT assay in K562R cell line, combination with 10μmol/L U0126, the IC50 values of IM was 0. 134±0. 059μmol/L, which reduced to 8. 9% of single IM treatment. 3. The reversing mechanism of U0126 to imatinib resistance in K562R cell line. Western Blot showed single IM up-regulated the p-Lyn and p-ERK, while U0126 reduced the expression of them, the combination of the IM and U0126 could synergisticly reduce the p-Lyn expression and neutralize the up-regulation of p-ERK caused by IM single agent. Single IM also up-regulated the p-mTOR in K562R while U0126 reduced it, single IM or U0126 had no influence on p-4EBP1 in K562R, the combination of the two drugs could synergisticly reduce the p-4EBP1 and neutralize the up-regulation of p-mTOR caused by IM single agent. IM but not U0126could reduce p-cAbl and the combination of the two was more effective than IM treatment. IM alone or combination with U0126 could not regulate p-STAT5 expression in K562R. RT-PCR showed that neither IM treatment nor its combination with U0126 could change the level of lyn and erk1, 2 gene in the cell lines. Conclusions 1. BCR-ABL-independent activation of Lyn and ERK1/2 involved in IM resistance mechanism in IM-resistant K562R cell line. Imatinib alone could up-regulated the expression of the p-Lyn, p-ERK, p-mTOR in K562R cell line. MEK1/2 inhibitor U0126 could reverse the IM resistance by reducing the expression of the p-Lyn, p-ERK, p-mTOR, p-4EBP1 of IM-resistant K562R cell line, and the combination of U0216 and Imatinib could synergisticly depress up-regulation of the p-Lyn, p-ERK, p-mTOR and p-4EBP1 caused by IM. Grant support: National Natural Science Foundation of China (No. 30770912), Foundation of the Science & Technology Department of Sichuan Province (No. 2008SZ0017). Disclosures: No relevant conflicts of interest to declare.

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Evaluation of Focal Adhesion Kinase Gene Expression in Leukemia and Cancer Cell Lines Using Combined Molecular Cytogenetic Investigations and Quantitative Real Time RT-PCR.

Blood ◽

10.1182/blood.v104.11.4282.4282 ◽

2004 ◽

Vol 104 (11) ◽

pp. 4282-4282

Author(s):

Lydia Campos ◽

Andrei Tchirkov ◽

Jerome Cornillon ◽

Mirella Mihaescu ◽

Michel Giollant ◽

...

Keyword(s):

Western Blot ◽

Focal Adhesion Kinase ◽

Cell Line ◽

Cell Lines ◽

Focal Adhesion ◽

Genomic Dna ◽

Chromosome 8 ◽

Rt Pcr ◽

Molecular Cytogenetic ◽

Chromosomal Origin

Abstract FAK (Focal Adhesion Kinase) is a non-receptor tyrosine kinase protein implicated in integrin-mediated signal pathways. The human gene fak is located on chromosome 8q near c-myc. Cells that overexpress FAK show increased migration and increased cell survival with apoptosis inhibition. The aim of the present study was to investigate the genomic or post-genomic origin of this overexpression in seven tumor cell lines with different levels of FAK expression: K562, an erythroblastic cell line; U937, a monoblastic cell line; KG1a, a poorly differenciated myeloblastic cell line; HL 60, a promyelocytic cell line; Jurkat, a lymphoblastic cell line; A549, a bronchial adenocarcinoma cell line; M4Beu, a lymph node metastasis melanoma cell line. Total or partial chromosome 8 qualitative or quantitative abnormalities and the presence of double minute chromosomes bearing coding genomic DNA fragments were investigated using both conventional cytogenetic (standard karyotype after R- and G- banding) and molecular cytogenetic such as multicolor karyotype (M-FISH), FISH and comparative genomic hybridization (CGH). The mRNA expression was investigated using quantitative real time RT-PCR and the protein level using immunocytochemistry and western blot (immunoblot) analysis. Except for the Jurkat cell line, karyotypes revealed complex modifications. FISH and M-FISH allowed to precisely identify the chromosomal origin of the genomic material on each chromosome and CGH allowed to characterize relative loss and gain of coding genomic DNA and to identify their chromosomal origin. Summarized results are shown in the following table: No detectable RT-PCR product was observed for HL60 and U937 cell lines. The preliminary results show that there was usually a good correlation between PCR data and western blot analysis. However, FAK overexpression for KG1a cell line most probably has a genomic origin, while in K562 and A549 cell lines the origin is most probably at the transcription or post-transcription level without any abnormality of chromosome 8. Dysregulation of fak gene is observed in hematopoietic as well as solid tulor cell lines, and may contribute to leukemogenesis.</CENTER> Cell line FISH 8q24-qter CGH Chr. 8 RT-PCR RT-Q-PCR Western blot RT-Q-PCR results in copy number ratio K562 Normal Normal + 130.1 ++++ KG1a Amplified enh(8)(q11qter) + 37.5 ++++ Jurkat Normal Normal + 8.7 + (low) U937 Normal enh(8)(pterqter) 0 0 0 HL60 Amplified amp(8)(q23-24) 0 0 0 M4Beu Normal Normal + 43.5 0 A549 Normal Normal + 46 ++++

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Intracellular Accumulation Of Light Chains Caused By Lenalidomide, and Mediated Via CRBN, Causes Major ER Stress and Is Implicated In The Synergistic Combination Of Imids and Proteasome Inhibitors

Blood ◽

10.1182/blood.v122.21.4434.4434 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4434-4434

Author(s):

Sinto Sebastian ◽

Yuan Xiao Zhu ◽

Esteban Braggio ◽

Sonali Panchabhai ◽

Chang-Xin Shi ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Endoplasmic Reticulum Stress ◽

Western Blot ◽

Cell Lines ◽

Light Chain ◽

Proteasome Inhibitors ◽

Rt Pcr ◽

Immunoglobulin Light Chain ◽

Knock Down ◽

Induced Apoptosis

Background The precise molecular mechanism and targets of lenalidomide specific anti-Multiple Myeloma (MM) activity remain largely unknown, although, cereblon (CRBN) has been identified as a central mediator of activity with IRF-4 acting as a downstream molecule. Lenalidomide resistance in MM cells which, despite CRBN depletion, are able to restore their IRF-4 levels suggests the existence of alternative pathways. Methods To measure apoptosis and gene expression analysis 1x 106cells were incubated with 10μm to 50μm of lenalidomide for 24 to 96 hours before they were examined by annexin-PI and FACS analysis. Gene and protein expression were measured by RT-PCR, western blot, and immunohistochemistry. For lenalidomide followed bortezomib serial studies, cells were incubated with 10μm of lenalidomide for 48 hours and later treated with bortezomib for 24 to 48 hrs. CRBN and immunoglobulin light chain knock-down were performed by lentiviral mediated shRNA. Results We found lenalidomide induces Endoplasmic reticulum stress (ERS) via accumulation of intracellular immunoglobulin proteins, but only in the presence of CRBN in a panel of MM cell lines. This accumulation of intracellular proteins resulted in ERS as documented by western blot and RT-PCR in OPM2 and MMIS cell lines. We next utilized OPM2 cells knocked down for CRBN and control, non-target (NT), and treated with different doses of lenalidomide. After three days of treatment an ERS response was occurring in OPM2-NT cells but not in CRBN knockdown cells. Using Western blot we found decreased XBP-1u and increased XBP-1s, ERS marker proteins, in CRBN positive (NT) cells after 72 hours of lenalidomide treatment, but not in CRBN knock-down cells. Another ERS marker GRP78/BiP was also clearly accumulated after lenalidomide treatment in CRBN positive cells. Inactivation of the tumor suppressor p53 by degradation is a mechanism utilized by cells to adapt to ERS has been reported. We also found that p53 protein down regulated after lenalidomide treatment in CRBN positive OPM2 and MMIS cells. We have analyzed other isogenic cell lines MM1.S (lenalidomide-sensitive) and isogenic MM1.Sres (lenalidomide-resistant) HMCLs and found that lenalidomide induces ERS in MM1.S but not MM1.Sres cells. CRBN is important for lenalidomide to induce immunoglobulin protein accumulation and ERS was further proved by over-expressing CRBN in OCI-My5 MM cell line and subsequent lenalidomide treatment. To test the effect of light chain accumulation as ER stressors, we knocked down immunoglobulin light chain lambda in human MM cell line OPM2. Knock-down of lambda light chain in OPM2 cells resulted in lenalidomide resistance and it induced endoplasmic reticulum stress mediated anti-myeloma activity. Our preliminary data reveals that lenalidomide mediated progressive ERS can positively enhance bortezomib induced apoptosis in an in-vitro MM model. We pre-treated myeloma cell lines with lenalidomide and subsequently treated with bortezomib. MM cells pre-treated with lenalidomide for two days and there after treated with bortezomib clearly shown increased sensitivity to bortezomib induced apoptosis than non-pre-lenalidomide treated cells. Conclusion Here we show that lenalidomide causes accumulation of immunoglobulin light chains, inducing progressive ER stress, resulting in anti-myeloma activity and that effect depends on the presence of CRBN. Proteasome inhibitors such as bortezomib also sensitize MM cells to endoplasmic reticulum stress-mediated apoptosis. Our data demonstrated the synergistic effect of lenalidomide and proteasome inhibitors, likely due to the augmented protein stress. This data support the use of serial therapy utilizing pre-lenalidomide treatment followed by bortezomib or carfilzomib treatment. Disclosures: Fonseca: Medtronic: Consultancy; Otsuka: Consultancy; Celgene: Consultancy; Genzyme: Consultancy; BMS: Consultancy; Lilly: Consultancy; Onyx: Consultancy, Research Funding; Binding Site: Consultancy; Millennium: Consultancy; AMGEN: Consultancy; Cylene: Research Funding; Prognostication of MM based on genetic categorization of the disease: Prognostication of MM based on genetic categorization of the disease, Prognostication of MM based on genetic categorization of the disease Patents & Royalties.

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Expression of Platelet Membrane Glycoprotein V in Human Megakaryocytes and Megakaryocytic Cell Lines: A Study Using a Novel Monoclonal Antibody against GPV

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648955 ◽

1994 ◽

Vol 72 (05) ◽

pp. 762-769 ◽

Cited By ~ 11

Author(s):

Toshiro Takafuta ◽

Kingo Fujirmura ◽

Hironori Kawano ◽

Masaaki Noda ◽

Tetsuro Fujimoto ◽

...

Keyword(s):

Monoclonal Antibody ◽

Cell Lines ◽

Immunohistochemical Analysis ◽

Specific Protein ◽

Platelet Membrane ◽

Rt Pcr ◽

Chain Reaction ◽

Flow Cytometric ◽

Polymerase Chain ◽

Megakaryocytic Cell

SummaryGlycoprotein V (GPV) is a platelet membrane protein with a molecular weight of 82 kD, and one of the leucine rich glycoproteins (LRG). By reverse transcription-polymerase chain reaction (RT-PCR), GPV cDNA was amplified from mRNA of platelets and megakaryocytic cell lines. However, since there are few reports indicating whether GPV protein is expressed in megakaryocytes as a lineage and maturation specific protein, we studied the GPV expression at the protein level by using a novel monoclonal antibody (1D9) recognizing GPV. Flow cytometric and immunohistochemical analysis indicated that GPV was detected on the surface and in the cytoplasm of only the megakaryocytes in bone marrow aspirates. In a megakaryocytic cell line UT-7, GPV antigen increased after treatment with phorbol-12-myri-state-13-acetate (PMA). These data indicate that only megakaryocytes specifically express the GPV protein among hematopoietic cells and that the expression of GPV increases with differentiation of the megakaryocyte as GPIb-IX complex.

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