Biomedical subjects

Ryuzo Ueda

Publications and source records attributed to Ryuzo Ueda.

At least 37 records · Page 2Linked to original sources

PubMed2006

Molecular epidemiology of hepatitis B virus in the United Republic of Tanzania.

In the United Republic of Tanzania, 457 voluntary blood donors were enrolled in hepatitis B virus (HBV) serological screening; 4.8% (22/457) carried HBsAg, 13.6% (3/22) of whom were HBeAg-positive. The mean age among HBeAg-negative carriers was 31 years. HBV DNA was detectable in 81.8% (18/22), the mean level was 3.67 (+/-1.77) log copies/ml. Genotype A was determined in 90.9% (20/22) and 18/20 were classified into subgenotype Aa (Asia/Africa). The basal core promoter, precore and partial core nucleotide sequences were analyzed in the 18 strains; T1809/T1812 ("Kozak" sequence) and A/T1888 (encapsidation signal) variants were identified in 100% and 78%, respectively. The complete genome sequencing for one of the Tanzanian strains revealed no recombination. In conclusion, HBV seroprevalence is high among general population in Tanzania, and the HBV/Aa-infection is predominant. The indicated tendency to early HBeAg seroconversion and declining of the viral load should be confirmed further in case-control studies.

Adult↗

PubMed2006

Immunoglobulin VH genes in thymic MALT lymphoma are biased toward a restricted repertoire and are frequently unmutated.

Thymic MALT lymphoma shows certain distinctive features among MALT lymphomas, such as expression of IgA isotype, consistent lack of API2-MALT1 gene fusion, and very strong association with autoimmune disease, especially Sjogren's syndrome. To help clarify the nature of the clonal lymphoid infiltrates, we analysed the usage and somatic hypermutation of the Ig heavy chain variable region (V(H)) genes in nine different cases. The V(H) rearrangement was potentially functional in all cases and was restricted to the V(H)3 family. V(H) usage was biased toward V(H)3-30 (five cases) and V(H)3-23 (three cases) segments, which have both been frequently expressed by autoimmune B cells. Somatic hypermutation was absent in five cases. Fewer than the expected replacement mutations were found in the framework regions in two cases, indicating a negative antigen selection pressure. Ongoing mutation was absent in all cases. D segment usage was varied, whereas J(H) segment usage was restricted to J(H)4. The observed patterns of V(H) usage and mutations suggested that specific antigens may play a pathologically relevant role in the genesis or progression of thymic MALT lymphoma.

Aged↗

PubMed2006

Smoking increases the treatment failure for Helicobacter pylori eradication.

PURPOSE: Treatment failure for Helicobacter pylori (H. pylori) eradication is encountered in approximately 10-20% of patients, and many studies have pointed to a link with smoking. To investigate the effects of smoking on eradication outcome, we performed a meta-analysis. METHODS: A PubMed search was performed to retrieve articles published up to August 2005. Pooled odds ratio (OR) and differences rate for H. pylori eradication failure in smokers compared with nonsmokers were used as summary statistics. Meta-regression was used for examining the source of heterogeneity. RESULTS: Twenty-two published studies (5538 patients), which provided information on eradication failure according to smoking status, were included in the analysis. The summary OR for eradication failure among smokers relative to nonsmokers was 1.95 (95% confidence interval [CI]: 1.55-2.45; P <.01). It corresponds with the differences in eradication rates between smokers and nonsmokers (8.4% [95% CI: 3.3-13.5%, P <.01]). Meta-regression analysis demonstrated that a high proportion of nonulcer dyspepsia patients in studies revealed a higher failure rate among smokers, compared with a low proportion of nonulcer dyspepsia. CONCLUSIONS: Our meta-analysis demonstrated that smoking increases the treatment failure rate for H. pylori eradication.

Anti-Bacterial Agents↗

PubMed2006

Novel subtypes (subgenotypes) of hepatitis B virus genotypes B and C among chronic liver disease patients in the Philippines.

Several hepatitis B virus (HBV) subtypes (subgenotypes), HBV/Aa (A1 : Asia/Africa), Ae (A2 : Europe), Bj (B1 : Japan) and Ba (B2 : Asia), have been reported with respect to clinical differences between patients infected with these subtypes (subgenotypes). HBV genotype distribution among patients with chronic liver diseases was investigated in the Philippines, where such studies have not been carried out previously. One hundred sera were obtained from such patients, consisting of 32 chronic hepatitis (CH), 37 cirrhosis and 31 hepatocellular carcinoma (HCC) patients. Nine complete genomes and 100 core promoter/precore genes of HBV were sequenced directly. Phylogenetic analyses revealed 51 HBV/A (Aa/A1), 22 HBV/B and 27 HBV/C strains. Interestingly, most HBV/C strains in the Philippines formed a specific cluster distinct from previous HBV/C strains (C1-4), indicating a novel subtype (subgenotype), HBV/C5. Moreover, most HBV/B strains fell within the specific cluster of the HBV/B subtype (subgenotype) B5, with viral characteristics of HBV/Ba (B2) carrying a recombination with HBV/C over the precore and core genes. Of the three genotypes, HBV/B and HBV/C were significantly more prevalent than HBV/A in cirrhosis and HCC patients (P<0.02). The prevalence of the core promoter mutations T1762/A1764 was higher in HCC patients with HBV/B and HBV/C. Multivariate analysis indicated that age [odds ratio (OR) 3.43; 95 % confidence interval (CI) 1.04-11.36; P=0.044] and the core promoter mutation (OR 14.08; 95% CI 3.62-4.74; P<0.001) were significant factors for HCC development. In conclusion, novel HBV subtypes (subgenotypes) C5 and B5 are prevalent in the Philippines, as well as HBV/Aa (A1).

Carcinoma, Hepatocellular↗

PubMed2006

Role of ABCG2 as a biomarker for predicting resistance to CPT-11/SN-38 in lung cancer.

To examine the mechanism of resistance to 7-ethyl-10-hydroxycamptothecin (SN-38) in lung cancer, we continuously exposed the non-small-cell lung cancer (NSCLC) cell line NCI-H23 to SN-38 and selected the SN-38-resistant clone H23/SN-38. After 2 months of culturing in SN-38-free conditions, H23/SN-38 cells recovered their sensitivity to SN-38 and were subsequently established as the revertant H23/SN-38REV cell line. Because H23/SN-38 cells show cross resistance to certain anticancer drugs, such as topotecan, etoposide, doxorubicin and mitoxantrone, we examined the gene and protein expression levels of drug efflux transporters of the ATP-binding cassette (ABC) family. We found that both gene and protein expression of ABCG2/BCRP (ABCG2) in H23/SN-38 cells was increased compared with that in NCI-H23 cells and H23/SN-38REV cells. The cellular accumulation of topotecan in H23/SN-38 cells was decreased compared with that in NCI-H23 and H23/SN-38REV cells, and treatment with reserpine (an inhibitor of ABCG2) increased the cellular accumulation of topotecan in H23/SN-38 cells. Furthermore, treatment with reserpine also altered the sensitivity of H23/SN-38 cells to SN-38. These results indicate that the upregulation of ABCG2 was functional, and related to the resistance of H23/SN-38 cells to SN-38. Moreover, we found that gene expression levels of ABCG2 were significantly correlated with the concentration of SN-38 for 50% cell survival in 13 NSCLC cells (r=0.592, P<0.05). The present results indicate that the induction of ABCG2 by SN-38 does confer acquired resistance to CPT-11/SN-38, but the induction of ABCG2 and subsequent drug resistance are reversible. However, the expression level of ABCG2 may be a useful indicator of CPT-11/SN-38 activity in lung cancer.

ATP Binding Cassette Transporter, Subfamily G, Mem↗

PubMed2006

Sustained activation of c-jun-N-terminal kinase plays a critical role in arsenic trioxide-induced cell apoptosis in multiple myeloma cell lines.

Multiple myeloma (MM) is a presently incurable B-cell malignancy, and newer biologically based therapies are needed. Arsenic trioxide (ATO) has been established as a therapeutic agent for relapsed acute promyelocytic leukemia patients, and has been used for MM patients in clinical trials. In this study, we investigated the role of c-jun-N-terminal kinase (JNK) in ATO-induced apoptosis in MM lines. The exogenous interleukin (IL)-6 dependent MM line, ILKM-3, and independent MM lines, U266 and XG-7, were treated with a therapeutic concentration of ATO with or without JNK inhibitor 1 (a JNK-specific inhibitor) and anisomycin (a JNK activator). Their cell growth, cell cycle, JNK activation and NF-kappaB activation were investigated. ATO induced apoptosis in U266 and ILKM-3 regardless of their exogenous IL-6 dependency. This apoptosis, accompanied with decreased mitochondrial transmembrane potential, sustained activation of JNK but not cell cycle arrest. Pretreatment of JNK inhibitor prevented ATO-induced apoptosis in ATO-sensitive lines. Combined treatment with ATO and anisomycin induced sustained activation of JNK and apoptosis in the ATO-insensitive MM line, XG-7. Results of various time period treatments of ATO showed that sustained activation of JNK was needed in ATO-induced apoptosis in MM. IkBalpha phosphorylation was not associated with ATO-sensitivity of MM lines. These findings suggest that sustained activation of JNK plays a critical role in ATO-induced apoptosis in MM cell lines. Cotreatment with ATO and the agent, which can induce sustained activation of JNK, might improve the outcome in MM therapy.

Anisomycin↗

PubMed2006

The determinants of sensitivity and acquired resistance to gemcitabine differ in non-small cell lung cancer: a role of ABCC5 in gemcitabine sensitivity.

We examined the expression levels of the multidrug resistance protein 5 (ABCC5) gene in non-small cell lung cancer (NSCLC) cell lines to clarify the relationship with the sensitivity to gemcitabine. The expression levels of ABCC5 were inversely correlated with gemcitabine sensitivity significantly (r = 0.628; P < 0.01) in 17 NSCLC cells, whereas the expression of ABCC5 in the gemcitabine-resistant NSCLC cell line H23/GEM-R was the same as that in parental NCI-H23 cells. Treatment with the ABCC5 inhibitor zaprinast altered the sensitivity to gemcitabine in ABCC5-expressing NSCLC cells. In addition, decreasing the expression of ABCC5 by small interfering RNA altered the cytotoxicity to gemcitabine. These results indicate that modulation of ABCC5 activity could be used to increase the gemcitabine sensitivity in NSCLC. Previously, we found a decreased expression of deoxycytidine kinase in H23/GEM-R cells, and further investigation in this study showed an increased expression of ribonucleotide reductase subunit 1 in H23/GEM-R cells. We therefore also examined the effect of modifying the expression of both genes on gemcitabine resistance. We found that using small interfering RNA to decrease the expression of ribonucleotide reductase subunit 1 resulted in a decreased resistance to gemcitabine in H23/GEM-R cells. Furthermore, pretreatment with pemetrexed resulted in an increased deoxycytidine kinase expression concomitant with the alteration of the resistance to gemcitabine in H23/GEM-R cells. The determinants for sensitivity and the acquired resistance in gemcitabine are quite different; nonetheless, modification of these factors may increase the efficacy of gemcitabine in the treatment of NSCLC.

Antimetabolites, Antineoplastic↗

PubMed2006

[A case of pulmonary dirofilariasis that required differentiation from nontuberculous mycobacteriosis].

A 48-year-old man was admitted with an abnormal shadow on a chest X ray. Chest X ray and CT revealed a solitary nodule in the right lung field. Mycobacterium gordonae was cultured from sputum. Tumorectomy by video-assisted thoracoscopic surgery was done for histological diagnosis, and Dirofilaria worms accompanied with epithelioid cell granuloma with necrosis were found, while no bacteria were cultured from biopsy specimen, thus we diagnosed dirofilariasis. Because a solitary nodule can be caused by either Dirofilaria species or nontuberculous mycobacteria, this case was of interest with regard to the differential diagnosis of a lung solitary nodule.

Diagnosis, Differential↗

PubMed2006

[A case of Behçet disease with multiple nodular shadows and aneurysm of the brachiocephalic trunk caused by necrotizing vasculitis].

A 36-year-old man was admitted to our hospital in 1994 because of fever, and abdominal CT showed multiple low-density areas in the liver. Although granulomas were found in a liver biopsy specimen, a definitive diagnosis could not be established. With complaints of oral and genital ulcerations and erythema nodosum, Behçet disease was diagnosed in 1995 and he was treated with colchicine and cyclosporin. In May 1997 he had fever, leg edema, and proteinuria, and a renal biopsy revealed secondary amyloidosis. Cavitary lesions were found on a chest X-ray for the first time, but these later disappeared spontaneously. In October 2002, nodular shadows, cavitary lesions, and a mediastinal tumor appeared on a chest X-ray film. The nodular shadows in the lung fields had transformed into cavity lesions, resulting in the disappearance of the shadows. Specimens obtained from an open lung biopsy showed necrotizing granulomas and destructive vasculitis of the lung, and aneurysm of the brachiocephalic trunk caused by destructive vasculitis. Because multiple nodular shadows with cavitary lesions in Behçet disease, as in this case, have never been reported, we think this is a rare case.

Aneurysm↗

PubMed2005

T1653 mutation in the box alpha increases the risk of hepatocellular carcinoma in patients with chronic hepatitis B virus genotype C infection.

BACKGROUND: Most patients with chronic hepatitis B virus infection become carriers of inactive virus after hepatitis B e antigen seroconversion; however, a subgroup of patients have persistent abnormal transaminase levels and develop hepatocellular carcinoma after seroconversion. METHODS: In an age-matched case-control study, 40 carriers of inactive virus (mean age+/-standard deviation [SD], 50.9 +/- 11.1 years), 40 patients with chronic hepatitis (mean age+/-SD, 50.2 +/- 8.9 years), and 40 patients with hepatocellular carcinoma (mean age+/-SD, 50.7 +/- 9.4 years) who were infected with hepatitis B virus genotype C and had test results positive for antibody to hepatitis B e antigen were analyzed. RESULTS: The prevalence of T1653 in the box alpha was significantly higher among patients with hepatocellular carcinoma than among carriers of inactive virus who did not have hepatocellular carcinoma (70% vs. 25%; P < .0001) or chronic hepatitis (70% vs. 35%; P = .003). Mutations in the basic core promoter region (T1762/A1764) were frequently found in all groups, regardless of clinical status (in 77.5% of carriers of inactive virus, 77.5% of patients with chronic hepatitis, and 90% of patients with hepatocellular carcinoma). In the multivariate analysis, the presence of T1653, an alanine aminotransferase level of > or = 37 U/L, and a platelet count of < 18 x 10(4) platelets/mm3 were independent predictive values for hepatocellular carcinoma (odds ratio [95% confidence interval], 5.05 [1.56-16.35], 12.56 [3.05-51.77], and 11.5 [3.47-38.21], respectively). High alpha -fetoprotein level was the only independent predictive value for T1653 in patients with hepatocellular carcinoma (odds ratio, 12.67; 95% confidence interval, 1.19-134.17]). Among patients with test results positive for antibody to hepatitis B e antigen who had hepatocellular carcinoma and were infected with different genotypes of hepatitis B virus, the prevalence of T1653 was 40%, 15%, 25%, 25%, 67%, and 23% in patients infected with hepatitis B virus genotypes Aa, Ae, Ba, Bj, C, and D, respectively (P<.05 for genotype C vs. genotypes Ae, Ba, Bj, or D). CONCLUSIONS: Our data indicate that the addition of T1653 mutation in the box alpha to the basic core promoter mutation increases the risk of hepatocellular carcinoma in patients with hepatitis B virus genotype C.

Carcinoma, Hepatocellular↗

PubMed2005

Distribution of HBV genotypes among HBV carriers in Benin:phylogenetic analysis and virological characteristics of HBV genotype E.

AIM: To determine the distribution of Hepatitis B virus (HBV) genotypes in Benin, and to clarify the virological characteristics of the dominant genotype. METHODS: Among 500 blood donors in Benin, 21 HBsAg-positive donors were enrolled in the study. HBV genotypes were determined by enzyme immunoassay and restriction fragment length polymorphism. Complete genome sequences were determined by PCR and direct sequencing. RESULTS: HBV genotype E (HBV/E) was detected in 20/21 (95.2%), and HBV/A in 1/21 (4.8%). From the age-specific prevalence of HBeAg to anti-HBe seroconversion (SC) in 19 HBV/E subjects, SC was estimated to occur frequently in late teens in HBV/E. The comparison of four complete HBV/E genomes from HBeAg-positive subjects in this study and five HBV/E sequences recruited from the database revealed that HBV/E was distributed throughout West Africa with very low genetic diversity (nucleotide homology 96.7-99.2%). Based on the sequences in the basic core promoter (BCP) to precore region of the nine HBV/E isolates compared to those of the other genotypes, a nucleotide substitution in the BCP, G1757A, was observed in HBV/E. CONCLUSION: HBV/E is predominant in the Republic of Benin,and SC is estimated to occur in late teens in HBV/E. The specific nucleotide substitution G1757A in BCP,which might influence the virological characteristics, is observed in HBV/E.

Adolescent↗

PubMed2005

Classifying genotype F of hepatitis B virus into F1 and F2 subtypes.

AIM: To explore the propriety of providing hepatitis B virus (HBV) genotypes F and H with two distinct genotypes. METHODS: Eleven HBV isolates of genotype F (HBV/F) were recovered from patients living in San Francisco, Japan, Panama, and Venezuela, and their full-length sequences were determined. Phylogenetic analysis was carried out among them along with HBV isolates previously reported. RESULTS: Seven of them clustered with reported HBV/F isolates in the phylogenetic tree constructed on the entire genomic sequence. The remaining four flocked on another branch along with three HBV isolates formerly reported as genotype H. These seven HBV isolates, including the four in this study and the three reported, had a sequence divergence of 7.3-9.5% from the other HBV/F isolates, and differed by > 13.7% from HBV isolates of the other six genotypes (A-E and G). Based on a marked genomic divergence, falling just short of > 8% separating the seven genotypes, these seven HBV/F isolates were classified into F2 subtype and the former seven into F1 subtype provisionally. In a pairwise comparison of the S-gene sequences among the 7 HBV/F2 isolates and against 47 HBV/F1 isolates as well as 136 representing the other six genotypes (A-E and G), two clusters separated by distinct genetic distances emerged. CONCLUSION: Based on these analyses, classifying HBV/F isolates into two subtypes (F1 and F2) would be more appropriate than providing them with two distinct genotypes (F and H).

Amino Acid Sequence↗

PubMed2005

ARK5 is transcriptionally regulated by the Large-MAF family and mediates IGF-1-induced cell invasion in multiple myeloma: ARK5 as a new molecular determinant of malignant multiple myeloma.

ARK5, AMP-activated protein kinase (AMPK)-related protein kinase mediating Akt signals, is closely involved in tumor progression, and its stage-associated expression was observed in colorectal cancer. In this study, we found ARK5 expression in multiple myeloma cell lines expressing c-MAF and MAFB. In addition, gene expression profiling of 351 clinical specimens revealed ARK5 expression in primary myelomas expressing c-MAF and MAFB, suggesting that ARK5 may be a transcriptional target of the Large-MAF family. Sequence analysis of the ARK5 gene promoter revealed that it contains two putative MAF-recognition element (MARE) sequences. In support of this hypothesis, ARK5 was induced when an MAFB or c-MAF expression vector was introduced into non-ARK5-expressing colon cancer cells. Furthermore, ARK5 promoter activity was dramatically decreased by mutation or deletion of MARE sequences. Chromatin immunoprecipitation assays revealed an interaction between the Large-MAF family proteins and MARE sequences in the ARK5 promoter. Moreover, in ARK5 mRNA-expressing multiple myeloma lines, but not in ARK5-negative lines, insulin-like growth factor (IGF)-1 increased invasion activity. IGF-1-induced invasion was reproduced when ARK5 was overexpressed in Burkitt's lymphoma and plasmacytoma lines. Based on results, we conclude that ARK5 is a transcriptional target of the Large-MAF family through MARE sequence and that ARK5 may in part mediate the aggressive phenotype associated with c-MAF- and MAFB-expressing myelomas.

Base Sequence↗

PubMed2005

Clinical characteristics and prognostic implications of NPM1 mutations in acute myeloid leukemia.

Recently, somatic mutations of the nucleophosmin gene (NPM1), which alter the subcellular localization of the product, have been reported in acute myeloid leukemia (AML). We analyzed the clinical significance of NPM1 mutations in comparison with cytogenetics, FLT3, NRAS, and TP53 mutations, and a partial tandem duplication of the MLL gene (MLL-TD) in 257 patients with AML. We found NPM1 mutations, including 4 novel sequence variants, in 64 of 257 (24.9%) patients. NPM1 mutations were associated with normal karyotype and with internal tandem duplication (ITD) and D835 mutations in FLT3, but not with other mutations. In 190 patients without the M3 French-American-British (FAB) subtype who were treated with the protocol of the Japan Adult Leukemia Study Group, multivariate analyses showed that the NPM1 mutation was a favorable factor for achieving complete remission but was associated with a high relapse rate. Sequential analysis using 39 paired samples obtained at diagnosis and relapse showed that NPM1 mutations were lost at relapse in 2 of the 17 patients who had NPM1 mutations at diagnosis. These results suggest that the NPM1 mutation is not necessarily an early event during leukemogenesis or that leukemia clones with NPM1 mutations are sensitive to chemotherapy.

Adolescent↗

PubMed2005

Mechanisms for the apoptosis of small cell lung cancer cells induced by anti-GD2 monoclonal antibodies: roles of anoikis.

Anti-GD2 ganglioside antibodies could be a promising, novel therapeutic approach to the eradication of human small cell lung cancers, as anti-GD2 monoclonal antibodies (mAbs) induced apoptosis of small cell lung cancer cells in culture. In this study, we analyzed the mechanisms for the apoptosis of these cells by anti-GD2 mAbs and elucidated the mechanisms by which apoptosis signals were transduced via reduction in the phosphorylation levels of focal adhesion kinase (FAK) and the activation of a MAPK family member, p38, upon the antibody binding. Knock down of FAK resulted in apoptosis and p38 activation. The inhibition of p38 activity blocked antibody-induced apoptosis, indicating that p38 is involved in this process. Immunoprecipitation-immunoblotting analysis of immune precipitates with anti-FAK or anti-integrin antibodies using an anti-GD2 mAb revealed that GD2 could be precipitated with integrin and/or FAK. These results suggested that GD2, integrin, and FAK form a huge molecular complex across the plasma membrane. Taken together with the fact that GD2+ cells showed marked detachment from the plate during apoptosis, GD2+ small cell lung cancer cells seemed to undergo anoikis through the conformational changes of integrin molecules and subsequent FAK dephosphorylation.

Anoikis↗

PubMed2005

Effect of nifedipine on C-reactive protein levels in the coronary sinus and on coronary blood flow in response to acetylcholine in patients with stable angina pectoris having percutaneous coronary intervention.

The effects of nifedipine on inflammation and endothelial function in the coronary circulation were studied in patients who had angina pectoris (n = 17). Long-term treatment with nifedipine (nifedipine CR, 20 mg/day for 4 months) decreased levels of C-reactive protein in the coronary sinus (from 0.35 +/- 0.09 mg/dl to 0.07 +/- 0.01 mg/dl, mean +/- SEM, p <0.05) and enhanced acetylcholine-induced increases in coronary blood flow. Thus, nifedipine is effective in decreasing inflammation and incresing endothelial function in the coronary circulation.

Acetylcholine↗

PubMed2005

Pharmacokinetic and pharmacodynamic comparison of fluoropyrimidine derivatives, capecitabine and 5'-deoxy-5-fluorouridine (5'-DFUR).

PURPOSE: Capecitabine is a three-step prodrug that was rationally designed to be a more effective and safer alternative to its intermediate metabolite, 5'-deoxy-5-fluorouridine (5'-DFUR). We compared the pharmacokinetics/pharmacodynamics of these drugs in metastatic breast cancer patients. METHODS: Six patients received oral capecitabine at 1657 mg/m2 twice daily and 17 received 5'-DFUR at 400 mg three times daily. Both drugs were administered for 21 days followed by a 7-day rest. RESULTS: Median daily 5'-DFUR AUC was significantly higher for capecitabine than for 5'-DFUR (81.1 vs 32.6 mmol h/l; P = 0.01). Following treatment with 5'-DFUR, the median AUC and Cmax of 5'-DFUR tended to be higher in patients with a partial response (3.83 microg h/ml and 4.88 microg/ml) and stable disease (6.46 microg h/ml and 4.96 microg/ml) than in those with disease progression (2.53 microg h/ml and 1.36 microg/ml). The AUC and Cmax of 5'-DFUR was significantly related to overall survival. CONCLUSIONS: These results support the superiority of capecitabine over 5'-DFUR.

Administration, Oral↗

PubMed2005

Enhanced natural killer cell binding and activation by low-fucose IgG1 antibody results in potent antibody-dependent cellular cytotoxicity induction at lower antigen density.

PURPOSE: Recent studies have revealed that fucose removal from the oligosaccharides of human IgG1 antibodies results in a significant enhancement of antibody-dependent cellular cytotoxicity (ADCC) via improved IgG1 binding to FcgammaRIIIa. In this report, we investigated the relationship between enhanced ADCC and antigen density on target cells using IgG1 antibodies with reduced fucose. EXPERIMENTAL DESIGN: Using EL4 cell-derived transfectants with differential expression levels of exogenous human CC chemokine receptor 4 or human CD20 as target cells, ADCC of fucose variants of chimeric IgG1 antibodies specific for these antigens were measured. We further investigated IgG1 binding to natural killer (NK) cells and NK cell activation during ADCC induction to elucidate the mechanism by which low-fucose IgG1 induces ADCC upon target cells with low antigen expression. RESULTS: Low-fucose IgG1s showed potent ADCC at low antigen densities at which their corresponding high-fucose counterparts could not induce measurable ADCC. The quantitative analysis revealed that fucose depletion could reduce the antigen amount on target cells required for constant degrees of ADCC induction by 10-fold for CC chemokine receptor 4 and 3-fold for CD20. IgG1 binding to NK cells was increased by ligating IgG1 with clustered antigen, especially for low-fucose IgG1. Up-regulation of an activation marker, CD69, on NK cells, particularly the CD56(dim) subset, in the presence of both the antibody and target cells was much greater for the low-fucose antibodies. CONCLUSIONS: Our data showed that fucose removal from IgG1 could reduce the antigen amount required for ADCC induction via efficient recruitment and activation of NK cells.

Antibody-Dependent Cell Cytotoxicity↗