Point mutation of C-terminal region of CD20 molecule predicts rituximab-induced complement-dependent cytotoxicity and clinical response to rituximab in non-Hodgkin’s lymphoma

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 7563-7563 ◽  
Author(s):  
Y. Terui ◽  
Y. Mishima ◽  
Y. Mishima ◽  
M. Yokoyama ◽  
K. Hatake ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Laser Scanning ◽  
Transmembrane Domain ◽  
Point Mutations ◽  
K562 Cells ◽  
Cytoplasmic Domain ◽  
Laser Scanning Confocal Microscopy ◽  
Cytoplasmic Domains ◽  
Isolated Cells ◽  
Cd20 Expression

7563 Background: Although rituximab is commonly used as induction and maintenance therapy for malignant lymphoma, some patients become refractory to treatment and the mechanism of resistance is unclear. The aim of this study was to investigate the relationship between CD20 mutations and rituximab resistance. Methods: To investigate whether CD20 mutations affect response to rituximab, fresh CD19+ lymphoma cells were isolated from the lymph nodes, or bone marrow of 68 patients with NHL. The cells were subsequently sorted by flow cytometry. RNA was prepared from the isolated cells and RT-PCR was performed. The PCR products were sequenced, subcloned into an expression vector pTARGET, transfected into K562 cells. CD20 expression was examined by flow cytometry and laser scanning confocal microscopy. Results: In all 68 patients, overall response rate (CR+CRu+PR) to rituximab was 91.2% (62/68), but t four cases became PD after PR. DNA sequence analysis revealed that point mutations were mostly observed in three CD20 domains - extracellular/cytoplasmic domains, the third transmembrane domain and the C-terminal cytoplasmic domain. Two cases had point mutations in extracellular/cytoplasmic domains, one patient had point mutations in the transmembrane domain, four cases showed point mutations in the C-terminal cytoplasmic domain and six cases had non-specific CD20 mutations, which did not affect CD20 expression. 56 patients showed no mutations of CD20 gene. CD20 expression was very weak in patients with point mutations in the C-terminal cytoplasmic domain, whereas expression was increased in patients with point mutations in the transmembrane domain. Conclusions: Point mutations in CD20 may cause rituximab resistance and identification of CD20 mutations upon diagnosis may help to predict a patient’s response to rituximab. No significant financial relationships to disclose.

Identification of CD20 Mutations in Malignant Lymphoma: Can They Be Predictors of Response to Rituximab?.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 288-288 ◽  
Author(s):  
Yasuhito Terui ◽  
Takuma Sakurai ◽  
Yuji Mishima ◽  
Yuko Mishima ◽  
Natsuhiko Sugimura ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Malignant Lymphoma ◽  
Laser Scanning ◽  
Transmembrane Domain ◽  
Point Mutations ◽  
K562 Cells ◽  
Cytoplasmic Domain ◽  
Isolated Cells ◽  
Mammalian Expression ◽  
Cd20 Expression

Abstract Purpose: Although rituximab is commonly used as induction and maintenance therapy for CD20+ malignant lymphoma, some patients become refractory to treatment and the mechanism of resistance is unclear. The aim of this study was to investigate the relationship between CD20 mutations and rituximab resistance. Methods: To investigate whether CD20 mutations affect the response to rituximab, fresh CD19+ lymphoma cells were isolated from the lymph nodes, peripheral blood or bone marrow of 48 patients with NHL using magnetic activated cell sorting (MACS). CD19+/CD20+ cells were subsequently sorted by flow cytometry. RNA was prepared from the isolated cells and RT-PCR was performed. The resulting PCR products were sequenced, subcloned into the mammalian expression vector pTARGET, transfected into K562 cells and CD20 expression was examined by flow cytometry and laser scanning confocal microscopy. Results: In all 48 patients, overall response rate (CR+CRu+PR) to rituximab was 93.8% (45/48), but two cases became PD after PR. DNA sequence analysis revealed that point mutations were mostly observed in two CD20 domains - the third transmembrane domain and the C-terminal cytoplasmic domain. One patient had point mutations in the transmembrane domain, three cases showed point mutations in the C-terminal cytoplasmic domain and six cases had non-specific CD20 mutations, which did not affect CD20 expression. Thirty-eight patients showed no mutations of CD20 gene. CD20 expression was very weak in patients with point mutations in the C-terminal cytoplasmic domain, whereas expression was increased in patients with point mutations in the transmembrane domain. Conclusions: This study suggests that point mutations in CD20 may cause rituximab resistance and identification of CD20 mutations upon diagnosis may help to predict a patient’s response to rituximab.

scholarly journals Integrin cytoplasmic domains mediate inside-out signal transduction

1994 ◽  
Vol 124 (6) ◽  
pp. 1047-1059 ◽  
Author(s):  
TE O'Toole ◽  
Y Katagiri ◽  
RJ Faull ◽  
K Peter ◽  
R Tamura ◽  
...  
Keyword(s):  
K562 Cells ◽  
Cytoplasmic Domain ◽  
Alpha Subunit ◽  
Affinity Binding ◽  
Cell Type ◽  
Cytoplasmic Domains ◽  
High Affinity Binding ◽  
High Affinity ◽  
Energy Dependent ◽  
Inside Out

We analyzed the binding of fibronectin to integrin alpha 5 beta 1 in various cells; in some cells fibronectin bound with low affinity (e.g., K562 cells) whereas in others (e.g., CHO), it bound with high affinity (Kd approximately 100 nM) in an energy-dependent manner. We constructed chimeras of the extracellular and transmembrane domains of alpha IIb beta 3 joined to the cytoplasmic domains of alpha 5 beta 1. The affinity state of these chimeras was assessed by binding of fibrinogen or the monoclonal antibody, PAC1. The cytoplasmic domains of alpha 5 beta 1 conferred an energy-dependent high affinity state on alpha IIb beta 3 in CHO but not K562 cells. Three additional alpha cytoplasmic domains (alpha 2, alpha 6A, alpha 6B) conferred PAC1 binding in CHO cells, while three others (alpha M, alpha L, alpha v) did not. In the high affinity alpha chimeras, cotransfection with a truncated (beta 3 delta 724) or mutated (beta 3(S752-->P)) beta 3 subunit abolished high affinity binding. Thus, both cytoplasmic domains are required for energy-dependent, cell type-specific affinity modulation. In addition, mutations that disrupted a highly conserved alpha subunit GFFKR motif, resulted in high affinity binding of ligands to alpha IIb beta 3. In contrast to the chimeras, the high affinity state of these mutants was independent of cellular metabolism, cell type, and the bulk of the beta subunit cytoplasmic domain. Thus, integrin cytoplasmic domains mediate inside-out signaling. Furthermore, the highly conserved GFFKR motif of the alpha subunit cytoplasmic domain maintains the default low affinity state.

Visualization of doxorubicin-induced oxidative stress in isolated cardiac myocytes

1996 ◽  
Vol 271 (5) ◽  
pp. H2079-H2085 ◽  
Author(s):  
N. Sarvazyan
Keyword(s):  
Laser Scanning ◽  
Laser Scanning Confocal Microscopy ◽  
Live Cells ◽  
Isolated Cells ◽  
Scanning Confocal Microscopy ◽  
Adult Rat ◽  
Rat Hearts ◽  
Isolated Cardiac Myocytes ◽  
Fluorescence Images ◽  
A New Technique

The paper presents high-resolution fluorescence images obtained using laser-scanning confocal microscopy. Isolated cells from adult rat hearts were preloaded with 2',7'-dichlorofluorescin (an oxidant-sensitive fluorescent probe) and exposed to doxo- rubicin, an important anticancer drug with prominent cardioxicity. Fluorescence images were collected from live cells simultaneously on two channels: 1) 515-530 nm emission range was used to monitor an increase in dichlorofluorescein, the oxidized product of dichlorofluorescein, and 2) emission > 610 nm was used to visualize the intracellular distribution of doxorubicin. The images reveal intracellular oxidation close to the mitochondria after only 20 min of exposure of isolated cardiomyocytes to 40-160 microM doxorubicin. The data confirm an oxidative mechanism of doxorubicin cardiotoxicity and demonstrate the capability of a new technique to monitor intracellular oxidation in living cardiomyocytes.

scholarly journals The two phenylalanines in the GFFKR motif of the integrin α6A subunit are essential for heterodimerization

1997 ◽  
Vol 328 (2) ◽  
pp. 529-537 ◽  
Author(s):  
A. Annemieke DE MELKER ◽  
Duco KRAMER ◽  
Ingrid KUIKMAN ◽  
Arnoud SONNENBERG
Keyword(s):  
Point Mutations ◽  
K562 Cells ◽  
Cytoplasmic Domain ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Α Subunit ◽  
Focal Contacts ◽  
Arginine Residues ◽  
A Site ◽  
Laminin 1

The membrane-proximal domain of the integrin α subunit contains a conserved motif of five amino acid residues, GFFKR. We deleted this motif from the human α6A subunit and found that in COS-7 cells this mutant cannot associate with the β1 subunit and is retained in the endoplasmic reticulum. Point mutations in the GFFKR motif of the glycine residue or the two highly charged amino acids, or deletion of the lysine and arginine residues, had no effect on the ability of α6 to interact with β1 and to be expressed at the cell surface. In contrast, by replacing either of the two phenylalanines with alanine, or by deletion of both of these residues, α6 was incapable of associating with β1. The α6 point mutants that associated with β1 were expressed in K562 cells and their responsiveness to integrin-activating factors was determined. None of these transfectants bound spontaneously to laminin-1, but binding could be induced by either PMA or the stimulating anti-β1 antibody TS2/16 to the same extent as that of the wild-type transfectant. The ability of these mutants to initiate focal-contact formation in CHO cells plated on laminin-1 substrates also appeared to be unaltered. Thus the behaviour of α6 mutants involving the glycine, lysine or arginine residues was indistinguishable from that of wild-type α6 both in inside-out and outside-in signalling. In contrast, deletion of the cytoplasmic domain of α6 C-terminal of the GFFKR motif resulted in a loss of responsiveness of α6β1 to PMA stimulation and formation of focal contacts on laminin-1. However, this mutant was targeted to focal contacts formed by other integrins, even when they had not bound ligand. Together, these results suggest that the two phenylalanine residues of the GFFKR motif provide a site for interaction of the α6A subunit with β1, whereas the cytoplasmic domain C-terminal of this motif is involved in the regulation of bidirectional signalling via α6Aβ1.

Induction of Gamma Globin and Erythrocyte Anion Exchane Protein in BFU-E Cultured in the Presence of Hydroxyurea.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3755-3755
Author(s):  
Gloria A. Green ◽  
Beau R. Braden ◽  
Obianuju Mba ◽  
Stacy A. Chivira ◽  
Laleh Ramezani ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Confocal Microscopy ◽  
Laser Scanning ◽  
Laser Scanning Confocal Microscopy ◽  
Band 3 ◽  
Band 3 Protein ◽  
Erythroid Progenitors ◽  
Gamma Globin ◽  
Scanning Confocal Microscopy ◽  
Reactive Mechanism

Abstract Hydroxyurea (HU) an S-phase specific cytotoxic agent has been used for the treatment of patients with sickle cell hemoglobinopathy and beta-thalassemias. The clinical efficacy of HU is due primarily to increases in fetal hemoglobin (HbF) levels. HU increases the %HbF and the %F cells. The HU reactive mechanism(s) in erythroid cells, however, have not been clearly defined. Patients receiving HU therapy develop subpopulations of macrocytic erythrocytes. Our previous studies demonstrate that sickle cell patients treated with HU develop subpopulations of RBCs that express greater relative levels of the erythrocyte anion exchange protein (AE1) per cell as compared with untreated individuals. We propose that part of the HU reactive mechanism will include the upmodulation of non-gamma globin erythroid proteins that contribute to the macrocytic structures. As part of our investigation of the development of RBCs expressing increased band 3 protein per cell, we have examined the possibility that HU induced AE1 synthesis can be detected in vitro using cultured erythroid progenitors. To investigate HU induced protein synthesis as a function of HU concentration, erythroid progenitors were cultured in semisolid media containing different concentrations of HU [0–40 micromolar] then assayed for AE1(band 3) and gamma globin. BFU-E were scored and harvested after 15 days in culture, then assayed. The change in the frequency of cells positive for band 3 protein was determined by flow cytometry, these cells were then assessed by laser scanning confocal microscopy. Results show that the frequency of cells positive for band 3 protein was greater in colonies grown in hydroxyurea as compared to controls. The band-3 upmodulation appears to plateau at 12.5 micromolar HU. These cells were assessed for dual and single stains by laser scanning confocal microscopy. Both band-3 protein and spectrin were detected. Laser scanning confocal microscopy revealed spectrin in the majority of cells; both band 3 and spectrin were detected in forty percent of the cells cultured in 12.5 micromolar HU. Band 3 protein detected by Western blots was increased [1–1.5 fold] over untreated control BFU-E harvested during the same time period. Secondly, the presence of band 3 protein and gamma globin in BFU-E was detected using two-color flow cytometry. BFU-E were cultured in increasing concentrations of HU. Colonies were permeabilized, and then labeled with tricolor-conjugated-anti-gamma globin. These cells were subsequently labeled with monoclonal anti-band 3 and PE-labeled anti-mouse antibody. Results show 2–3 fold increase in the % band 3 plus gamma globin positive cells over untreated cells. Collectively, these results suggest that part of the mechanism of HU action in erythroid cells involves the induction of erythroid structural proteins concordant with the induction of gamma globin.

scholarly journals MicroRNA Quantitation During Dendritic Cell Endocytosis Using Imaging Flow Cytometry: Key Factors and Requirements

2018 ◽  
Vol 51 (2) ◽  
pp. 793-811
Author(s):  
Qiang Tong ◽  
Ying Zhu ◽  
Dandan Zhang ◽  
Qing Cai ◽  
Wenchun Qu ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Laser Scanning ◽  
Laser Scanning Confocal Microscopy ◽  
Key Factors ◽  
Argonaute 2 ◽  
Scanning Confocal Microscopy ◽  
Imaging Flow Cytometry ◽  
Microscopy Method ◽  
Stimulation Of

Background/Aims: MicroRNA (miRNA)-induced suppression of dendritic cells (DCs) has been implicated in many diseases. Therefore, accurate monitoring of miRNA endocytosis by DCs is important for understanding the role of miRNAs in many diseases. Recently, a method for measuring the co-localization of Argonaute 2 (AGO2)-associated miRNAs on laser-scanning confocal microscopy method was proposed to localize the miRNAs. But its definition was limited by the number of observed cells through its accuracy. Methods: In this study, a method based on imaging flow cytometry was developed to localize miR-590-5p with fluorescent probes in DCs. miR-590-5p proven to play an important role in tumor immunity. This method enabled the quantification, visualization and localization of the fluorescence intensity in 30,000 individual cells. Results: Using this method, the DCs with different endocytotic ability were distinguished. The behaviour of miR-590-5p during endocytosis under the stimulation of tumor antigen in DCs was observed, binding to its cognate target mRNA and degradation in DCs. Conclusion: This method based on imaging flow cytometry provide an additional method to study miRNA processing in DCs, which makes it a valuable addition to existing miRNA research techniques.

scholarly journals Mutational Analysis, Using a Full-Length Rubella Virus cDNA Clone, of Rubella Virus E1 Transmembrane and Cytoplasmic Domains Required for Virus Release

1999 ◽  
Vol 73 (6) ◽  
pp. 4622-4630 ◽  
Author(s):  
Jiansheng Yao ◽  
Shirley Gillam
Keyword(s):  
Cdna Clone ◽  
Rubella Virus ◽  
Transmembrane Domain ◽  
Virus Assembly ◽  
Cytoplasmic Domain ◽  
Full Length ◽  
Virus Yield ◽  
Virus Release ◽  
Cytoplasmic Domains ◽  
Virus Budding

ABSTRACT We report on the construction of a full-length cDNA clone, pBRM33, derived from wild-type rubella virus M33 strain. The RNA transcripts synthesized in vitro from pBRM33 are highly infectious, and the viruses produced retain the phenotypic characteristics of the parental M33 virus in growth rate and plaque size. This cDNA clone was used to study the role of E1 transmembrane and cytoplasmic domains in virus assembly by site-directed mutagenesis. Three different alanine substitutions were introduced in the transmembrane domain of E1. These included substitution of leucine 464, cysteine 466, cysteine 467, and both cysteines 466 and 467 to alanine. In the E1 cytoplasmic domain, cysteine 470 and leucine 471 were altered to alanine. We found that these mutations did not significantly affect viral RNA replication, viral structural protein synthesis and transport, or E2/E1 heterodimer formation. Except for the substitution of cysteine 470, these mutations did, however, lead to a reduction in virus release. Substitution of cysteine 467 in the transmembrane region and of leucine 471 in the cytoplasmic domain dramatically reduced virus yield, resulting in the production of only 1 and 10% of the parental virus yield, respectively, in a parallel infection. These data show that E1 transmembrane and cytoplasmic domains play an important role in late stages of virus assembly, possibly during virus budding, consistent with earlier studies indicating that the E1 cytoplasmic domain may interact with nucleocapsids and that this interaction drives virus budding.

Isolated integrin β3 subunit cytoplasmic domains require membrane anchorage and the NPXY motif to recruit to adhesion complexes but do not discriminate between β1– and β3-positive complexes

2005 ◽  
Vol 94 (07) ◽  
pp. 155-166 ◽  
Author(s):  
Lionel Ponsonnet ◽  
Alessandro Foletti ◽  
Gian Carlo Alghisi ◽  
Curzio Rüegg
Keyword(s):  
Endothelial Cells ◽  
Transmembrane Domain ◽  
Focal Adhesions ◽  
Cytoplasmic Domain ◽  
Β Subunit ◽  
Cytoplasmic Domains ◽  
Npxy Motif ◽  
Covalently Linked ◽  
Focal Structures ◽  
Adhesion Complex

SummaryIntegrin adhesion receptors consist of non-covalently linked α and β subunits each of which contains a large extracellular domain, a single transmembrane domain and a short cytoplasmic tail. Engaged integrins recruit to focal structures globally termed adhesion complexes. The cytoplasmic domain of the β subunit is essential for this clustering. β1 and β3 integrins can recruit at distinct cellular locations (i.e. fibrillar adhesions vs focal adhesions, respectively) but it is not clear whether individual β subunit cytoplasmic and transmembrane domains are by themselves sufficient to drive orthotopic targeting to the cognate adhesion complex. To address this question, we expressed fulllength β3 transmembrane anchored cytoplasmic domains and truncated β3 cytoplasmic domains as GFP-fusion constructs and monitored their localization in endothelial cells. Membrane-anchored full-length β3 cytoplasmic domain and a β3 mutant lacking the NXXY motif recruited to adhesion complexes, while β3 mutants lacking the NPXY and NXXY motifs or the transmembrane domain did not. Replacing the natural β subunit transmembrane domain with an unrelated (i.e. HLA-A2 α chain) transmembrane domain significantly reduced recruitment to adhesion complexes. Transmembrane anchored β3 and cytoplasmic domain constructs, however, recruited without discrimination to β1– and β3-rich adhesions complexes. These findings demonstrate that membrane anchorage and the NPXY (but not the NXXY) motif are necessary for β3 cytoplasmic domain recruitment to adhesion complexes and that the natural transmembrane domain actively contributes to this recruitment. The β3 transmembrane and cytoplasmic domains alone are insufficient for orthotopic recruitment to cognate adhesion complexes.

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