An episomally maintained MDR1 gene for gene therapy

Potential applications of the MDR1 multidrug transporter in gene therapy include protecting sensitive bone marrow cells against cytotoxic drugs during cancer chemotherapy and serving as a dominant selectable marker when coexpressed with a corrective passenger gene. To address safety concerns associated with integrating viral systems, such as retroviruses, we tested the feasibility of maintaining a nonvirally delivered MDR1 gene (pEpiHaMA) episomally. An MDR1 vector containing the Epstein-Barr virus (EBV) origin of replication (OriP) and its nuclear retention protein (EBNA-1) was transfected into human (KB-3-1) cells. MDR1 was expressed at a higher level in cells carrying the episomal vector, pEpiHaMA, compared with the vector lacking sequences needed for episomal maintenance (pHaMA). Furthermore, more drug-resistant KB-3-1 colonies were obtained on selection after transfection with pEpiHaMA. These observations correlated with longer maintenance of episomes in cells transfected with pEpiHaMA. In addition, episomes could still be recovered for more than 1 month from tumor explants in nude mice that were injected with pEpiHaMA-liposome complexes after drug selection, suggesting that these constructs can be maintained extrachromosomally in vivo.

Intracellular domains of mouse connexin26 and -30 affect diffusional and electrical properties of gap junction channels

To evaluate the influence of intracellular domains of connexin (Cx) on channel transfer properties, we analyzed mouse connexin (Cx) Cx26 and Cx30, which show the most similar amino acid sequence identities within the family of gap junction proteins. These connexin genes are tightly linked on mouse chromosome 14. Functional studies were performed on transfected HeLa cells stably expressing both mouse connexins. When we examined homotypic intercellular transfer of microinjected neurobiotin and Lucifer yellow, we found that gap junctions in Cx30-transfected cells, in contrast to Cx26 cells, were impermeable to Lucifer yellow. Furthermore, we observed heterotypic transfer of neurobiotin between Cx30-transfectants and HeLa cells expressing mouse Cx30.3, Cx40, Cx43 or Cx45, but not between Cx26 transfectants and HeLa cells of the latter group. The main differences in amino acid sequence between Cx26 and Cx30 are located in the presumptive cytoplasmic loop and C-terminal region of these integral membrane proteins. By exchanging one or both of these domains, using PCR-based mutagenesis, we constructed Cx26/30 chimeric cDNAs, which were also expressed in HeLa cells after transfection. Homotypic intercellular transfer of injected Lucifer yellow was observed exclusively with those chimeric constructs that coded for both cytoplasmic domains of Cx26 in the Cx30 backbone polypeptide chain. In contrast, cells transfected with a construct that coded for the Cx26 backbone with the Cx30 cytoplasmic loop and C-terminal region did not show transfer of Lucifer yellow. Thus, Lucifer yellow transfer can be conferred onto chimeric Cx30 channels by exchanging the cytoplasmic loop and the C-terminal region of these connexins. In turn, the cytoplasmic loop and C-terminal domain of Cx30 prevent Lucifer yellow transfer when swapped with the corresponding domains of Cx26. In chimeric Cx30/Cx26 channels where the cytoplasmic loop and C-terminal domains had been exchanged, the unitary channel conductance was intermediate between those of the parental channels. Moreover, the voltage sensitivity was slightly reduced. This suggests that these cytoplasmic domains interfere directly or indirectly with the diffusivity, the conductance and voltage gating of the channels.

Hyperfractionated re-irradiation using a 3-dimensional conformal technique for locally recurrent carcinoma of the nasopharynx; preliminary results

To evaluate the efficacy of hyperfractionated re-irradiation using a three-dimensional conformal radiotherapy (3-D CRT) technique in patients with locally recurrent carcinoma of the nasopharynx. Four patients with locally recurrent nasopharyngeal cancer were retreated with a hyperfractionated schedule using a 3-D CRT technique. Re-irradiation was delivered in 1.1-1.2 Gy fractions twice per day (BID), with interfraction intervals of more than 6 hours. The total dose ranged from 59.4 to 69.2 Gy. A 3-D CRT technique with 5- or 6-field coplanar and/or non-coplanar beams were employed during the entire treatment procedure. All four patients achieved complete remission of locally recurrent lesions, with marked improvement of subjective symptoms, immediately after re-irradiation. All are alive and well without evidence of disease after limited follow-up periods, which range from 7 to 20 months. So far, there have been no radiation-induced neurologic complications. Four patients with locally recurrent carcinoma of the nasopharynx were successfully treated by hyperfractionated re-irradiation using a 3-D CRT technique. A relatively high re-irradiation dose of more than 60 Gy may be safely delivered with no serious acute or late radiation-induced complications in patients with local recurrences and who were initially treated with doses greater than 70 Gy.

Acetylation of HIV-1 Tat by CBP/P300 increases transcription of integrated HIV-1 genome and enhances binding to core histones

The HIV-1 Tat protein is required for viral replication and is a potent stimulator of viral transcription. Although Tat has been extensively studied in various reductive paradigms, to date there is little information as to how this activator mediates transcription from natural nucleosomally packaged long terminal repeats. Here we show that CREB-binding protein (CBP)/p300 interacts with the HIV-1 Tat protein and serves as a coactivator of Tat-dependent HIV-1 gene expression on an integrated HIV-1 provirus. The site of acetylation of Tat was mapped to the double-lysine motif in a highly conserved region, (49)RKKRRQ(54), of the basic RNA-binding motif of Tat. Using HLM1 cells (HIV-1(+)/Tat(-)), which contain a single copy of full-length HIV-1 provirus with a triple termination codon at the first AUG of the Tat gene, we find that only wild type, and not K50A, K51A, or K50A/K51A alone or in combination of ectopic CBP/p300, is able to produce full-length infectious virions, as measured by p24 gag ELISAs. Tat binds CBP/p300 in the minimal histone acetyltransferase domain (1253-1710) and the binding is stable up to 0.85 M salt wash conditions. Interestingly, wild-type peptide 41-54, and not other Tat peptides, changes the conformation of the CBP/p300 such that it can acquire and bind better to basal factors such as TBP and TFIIB, indicating that Tat may influence the transcription machinery by helping CBP/p300 to recruit new partners into the transcription machinery. Finally, using biotinylated wild-type or acetylated peptides, we find that acetylation decreases Tat's ability to bind the TAR RNA element, as well as to bind basal factors such as TBP, CBP, Core-Pol II, or cyclin T. However, the acetylated Tat peptide is able to bind to core histones on a nucleosome assembled HIV-1 proviral DNA.

Respiratory syncytial virus stimulation of vascular endothelial cell growth Factor/Vascular permeability factor

We hypothesized that respiratory syncytial virus (RSV)-induced pathologies could be mediated, in part, by vascular active cytokines elaborated during virus infection. To address this hypothesis, we determined whether RSV stimulated vascular endothelial cell growth factor (VEGF)/vascular permeability factor (VPF) elaboration in vitro. Supernatants from unstimulated A549 cells and normal human bronchial epithelial cells contained modest levels of VEGF. In contrast, supernatants from RSV-infected cells contained elevated levels of VEGF/VPF. This stimulation was seen after as little as 2 h, was still prominent after 48 h, and, by immunoblot, was specific for the 165- and 121-amino acid isoforms of VEGF/VPF. It was not associated with significant cell cytotoxicity or alterations in VEGF messenger RNA. It did, however, require new protein biosynthesis. In accordance with these findings, the 165- and 121-amino acid isoforms of VEGF/VPF were also found in the nasal washings from patients with RSV infections. These studies demonstrate that RSV is a potent stimulator of VEGF/VPF elaboration and that, in vitro, this stimulation is mediated via a noncytotoxic translational and/or post-translational biosynthetic mechanism. VEGF/VPF may play an important role in the pathogenesis of RSV-induced disorders.

Anti-Vascular endothelial growth factor treatment augments tumor radiation response under normoxic or hypoxic conditions

Recent studies in experimental animals have shown that combining antiangiogenic therapy with radiation can enhance tumor response. Whether this enhancement is mainly attributable to angiogenesis inhibition, endothelial cell radiosensitivity, tumor cell apoptosis, or a decrease in the number of hypoxic cells (improved oxygenation) is not known. We designed this study to discern the role of tumor oxygenation. We chose an anti-vascular endothelial growth factor (anti-VEGF) monoclonal antibody (mAb) which has a known target, human VEGF. We also measured interstitial fluid pressure (IFP) to test the hypothesis that the decreased vascular permeability induced by the anti-VEGF mAb can lower IFP. The effect of anti-VEGF mAb on vascular density, partial oxygen tension (pO2), and apoptosis was also measured. Athymic NCr/Sed nu/nu mice bearing 6-mm xenograft of the human glioblastoma multiforme (U87), or colon adenocarcinoma (LS174T) were treated with anti-VEGF mAb injected i.p. on alternate days for a total of six injections at a dosage of 100 microg/injection/mouse. For combined anti-VEGF and radiation, single radiation doses were given under normal blood flow (20 and 30 Gy) or clamped hypoxic conditions (30 and 40 Gy) 24 h after the sixth injection of mAb. The inhibition of the growth of U87 and LS174T tumors by the anti-VEGF mAb was associated with a significant reduction in tumor vascular density and a relatively small increase in the number of apoptotic cells. Compared with size-matched controls, IFP decreased by 74% in LS174T, and 73% in U87 in mice treated with anti-VEGF mAb. After antibody treatment PO2 increased significantly in U87, but did not change in LS174T tumors. Combined treatment induced in U87 tumors a tumor-growth delay (TGD) which was greater than additive; in LS174T except for the 40-Gy hypoxic group, the effect was only additive. In both U87 and LS174T the TGD induced by the antibody was independent of oxygen levels in the tumor at the time of radiation. The fact that the increase in TGD occurred under both normoxic and hypoxic conditions suggests that anti-VEGF mAb treatment can compensate for the resistance to radiation induced by hypoxia.

IL-13 stimulates vascular endothelial cell growth factor and protects against hyperoxic acute lung injury

Hyperoxia is an important cause of acute lung injury. To determine whether IL-13 is protective in hyperoxia, we compared the survival in 100% O(2) of transgenic mice that overexpress IL-13 in the lung and of nontransgenic littermate controls. IL-13 enhanced survival in 100% O(2). One hundred percent of nontransgenic mice died in 4-5 days, whereas 100% of IL-13-overexpressing mice lived for more than 7 days, and many lived 10-14 days. IL-13 also stimulated VEGF accumulation in mice breathing room air, and it interacted with 100% (2) to increase VEGF accumulation further. The 164-amino acid isoform was the major VEGF moiety in bronchoalveolar lavage from transgenic mice in room air, whereas the 120- and 188-amino acid isoforms accumulated in these mice during hyperoxia. In addition, antibody neutralization of VEGF decreased the survival of IL-13-overexpressing mice in 100% (2). These studies demonstrate that IL-13 has protective effects in hyperoxic acute lung injury. They also demonstrate that IL-13, alone and in combination with 100% (2), stimulates pulmonary VEGF accumulation, that this stimulation is isoform-specific, and that the protective effects of IL-13 are mediated, in part, by VEGF.

IL-11 selectively inhibits aeroallergen-induced pulmonary eosinophilia and Th2 cytokine production

IL-11 is a pleiotropic cytokine that induces tissue remodeling with subepithelial fibrosis when expressed in the airway. Its effects on the Th2-dominated airway inflammation that is characteristic of asthma, however, are poorly understood. To characterize the effects of IL-11 on Th2 tissue inflammation, we compared the inflammatory responses elicited by OVA in sensitized mice in which IL-11 is overexpressed in a lung-specific fashion (CC10-IL-11) with that in transgene- wild-type littermate controls. Transgene- and CC10-IL-11 transgene+ mice had comparable levels of circulating Ag-specific IgE after sensitization. OVA challenge of sensitized transgene- mice caused airway and parenchymal eosinophilic inflammation, Th2 cell accumulation, and mucus hypersecretion with mucus metaplasia. Exaggerated levels of immunoreactive endothelial cell VCAM-1, mucin (Muc) 5ac gene expression and bronchoalveolar lavage and lung IL-4, IL-5, and IL-13 protein and mRNA were also noted. In contrast, OVA challenge in CC10-IL-11 animals elicited impressively lower levels of tissue and bronchoalveolar lavage inflammation, eosinophilia, and Th2 cell accumulation, and significantly lower levels of VCAM-1 and IL-4, IL-5, and IL-13 mRNA and protein. IL-11 did not cause a comparable decrease in mucus hypersecretion, Muc 5ac gene expression, or the level of expression of RANTES, monocyte chemoattractant protein-2, or monocyte chemoattractant protein-3. In addition, IL-11 did not augment IFN-gamma production demonstrating that the inhibitory effects of IL-11 were not due to a shift toward Th1 inflammation. These studies demonstrate that IL-11 selectively inhibits Ag-induced eosinophilia, Th2 inflammation, and VCAM-1 gene expression in pulmonary tissues.

Functional expression of the murine connexin 36 gene coding for a neuron-specific gap junctional protein

The mouse connexin 36 (Cx36) gene was mapped on chromosome 2 and an identical transcriptional start site was determined in brain and retina on exon I. Rabbit polyclonal antibodies to the presumptive cytoplasmic loop of the Cx36 protein recognized in immunohistochemical analyses Cx36 expression in the retina, olfactory bulb, hippocampus, inferior olive and cerebellum. In olivary neurons strong punctate labeling at dendritic cell contacts and weaker labeling in the cytoplasm of dendrites were shown by immuno electron microscopy. After expression of mouse Cx36 cDNA in human HeLa cells, neurobiotin transfer was increased 1.8-fold and electrical conductance at least 15-fold compared to untransfected HeLa cells. No Lucifer Yellow transfer was detected in either untransfected or Cx36 transfected HeLa cells. Single Cx36 channels in transfected HeLa cells showed a unitary conductance of 14.3 + or - 0. 8 pS. The sensitivity of Cx36 channels to transjunctional voltage was low in both HeLa-Cx36 cells and Xenopus oocytes expressing mouse Cx36. No increased transfer of neurobiotin was detected in heterotypic gap junctions formed by Cx36 and 9 other connexins expressed in HeLa cells. Our results suggest that Cx36 channels function as electrical synapses for transmission of electrical and metabolic signals between neurons in the central nervous system.

SUMO-1 modification of Mdm2 prevents its self-ubiquitination and increases Mdm2 ability to ubiquitinate p53

Mdm2 is an E3 ubiquitin ligase for the p53 tumor suppressor protein. We demonstrate that Mdm2 is conjugated with SUMO-1 (sumoylated) at Lys-446, which is located within the RING finger domain and plays a critical role in Mdm2 self-ubiquitination. Whereas mutant Mdm2(K446R) is stabilized, it elicits increased degradation of p53 and concomitant inhibition of p53-mediated apoptosis. In vitro sumoylation of Mdm2 abrogates its self-ubiquitination and increases its ubiquitin ligase activity toward p53. Radiation caused a dose- and time-dependent decrease in the degree of Mdm2 SUMO-1 modification, which is inversely correlated with the levels of p53. Our results suggest that the maintenance of the intrinsic activity of a RING finger E3 ubiquitin ligase is sumoylation dependent and that reduced Mdm2 sumoylation in response to DNA damage contributes to p53 stability.

Combined analysis of germline polymorphisms of p53, GSTM1, GSTT1, CYP1A1, and CYP2E1: relation to the incidence rate of cervical carcinoma

BACKGROUND

The authors established the genotype frequencies of cytochrome P450 (CYP1A1/MspI, CYP2E1/PstI, and CYP2E1/DraI), glutathione-S-transferase (GSTM1 and GSTT1), and p53 (exon 4/AcclI and intron 3/16-base pair duplication) gene polymorphisms in cervical carcinoma patients and controls and evaluated the association between the specific genotype or genotype combinations of these polymorphisms and the risk of cervical carcinoma.

METHODS

In this case-control study, the genotypes of 181 human papillomavirus (HPV)-16 or HPV-18 positive cervical carcinoma patients and 1-to-1 age-matched controls were determined using a polymerase chain reaction-based technique.

RESULTS

Among these polymorphisms, the individuals carrying arginine/proline genotypes of p53 showed a 9.5-fold increase of cervical carcinoma risk (95% confidence interval [CI], 4.9-18.6) compared with those individuals carrying arginine/arginine genotypes. The frequency of overall GSTT1 null genotypes also was significantly higher in cervical carcinoma patients compared with that of GSTT1 positive genotypes (P = 0.003; odds ratio [OR] = 1.9; 95% CI, 1.2-2.9). The genotype combination of p53 and GST played a more important role in describing the relative risk of cervical carcinoma. The individuals carrying both the arginine/proline genotype of p53 and the null genotype of GSTT1 showed a 3.5-fold increase of cervical carcinoma risk (95% CI, 1.8-7.1) compared with those individuals carrying both the arginine/arginine genotype of p53 and the GSTT1 positive genotype. In the patients who were stratified into the two age groups, the null genotypes of GSTT1 (69.1% vs. 45.5%; P = 0.016) and GSTM1 (61.8% vs. 40.0%; P = 0.028) in cervical carcinoma were significantly overrepresented in the younger age subgroup (age 40 years or younger) compared with those of controls. Especially in this age group, the individuals carrying both null genotypes of GSTT1 and GSTM1 showed a 17.8-fold increase of cervical carcinoma risk (95% CI, 2.2-141.0) compared with the individuals carrying both positive genotypes of GSTT1 and GSTM1.

CONCLUSIONS

The results of the current study suggested that the arginine/proline genotype of p53, independently or in conjunction with the GSTT1 null genotype, could affect the genetic susceptibility for cervical carcinoma, and HPV positive women carrying both null genotypes of GSTT1 and GSTM1 have an increased risk of cervical carcinoma developing before age 40 years.

Neoadjuvant chemotherapy and radiation for inoperable carcinoma of the maxillary antrum: a matched-control study

A matched-control study comparing standard radiotherapy versus neoadjuvant chemotherapy and radiation was undertaken to clarify the effects of neoadjuvant systemic chemotherapy for locally advanced squamous cell carcinoma of the maxillary antrum. Thirty-four patients with inoperable maxillary cancer were treated with neoadjuvant chemotherapy and radiotherapy (Group II). Before starting radiotherapy, all patients in Group II received two or three cycles of neoadjuvant chemotherapy consisting of cisplatin and a 5-day continuous infusion of 5-fluorouracil with or without intravenous injection of vinblastine. Radiation doses ranged from 66 Gy to 75 Gy (median, 70 Gy). The response rate, patterns of failure, toxicity, and survival for Group II were compared with those for 34 stage-matched patients treated with radiation alone (Group I). Despite a higher response rate to neoadjuvant chemotherapy, the recurrence rate and patterns of treatment failure were not influenced by the addition of neoadjuvant chemotherapy. In most cases, neoadjuvant chemotherapy did not interfere with subsequent radiotherapy, and radiation-induced late complications occurred equally in both treatment groups. After a median follow-up of 48 months, there was no significant difference in 5-year actuarial survival or disease-free survival between the two treatment groups. Radiation alone for inoperable maxillary cancer was clearly suboptimal for improving local control and survival rate, but neoadjuvant chemotherapy in addition to standard radiotherapy failed to demonstrate any therapeutic advantage over radiation alone.

Partially mismatched related-donor bone marrow transplantation for pediatric patients with acute leukemia: younger donors and absence of peripheral blasts improve outcome

PURPOSE

To extend access to bone marrow transplantation (BMT), we used partially mismatched related donors (PMRD) for pediatric patients with acute leukemia. In this report we sought to determine pretransplantation factors that might predict outcome.

PATIENTS AND METHODS

Of 67 such patients, 43 had acute lymphocytic leukemia and 24 had acute myelogenous leukemia. At the time of transplantation, 41 patients were in relapse. Donors included 40 parents, 24 siblings, and three cousins. HLA disparity of two to three major antigens was detected in two thirds of the donor-recipient pairs. Conditioning therapy, including total-body irradiation and chemotherapy followed by graft-versus-host disease (GvHD) prophylaxis with partial T-cell depletion of the graft using T10B9 or OKT3, was combined with posttransplantation immunosuppression.

RESULTS

Estimated probability (EP) of engraftment was 0.96 and was not affected by donor-antigen mismatch (AgMM; P =.732). EP of grades 2 to 4 acute GvHD was 0.24 and was not affected by recipient AgMM (P =.796). EP of disease-free survival was 0.26 at 3 years but improved to 0.45 when donors were younger than 30 years (P<.001). EP of relapse at 3 years was 0.41 and reduced with younger donors' age. For patients who were in relapse at the time of transplantation, absence of blasts was associated with a lower relapse rate (0.46 v. 0.84; P =. 083), similar to that of patients in remission.

CONCLUSION

PMRD-BMT in pediatric leukemia resulted in high engraftment and low GvHD rates. To improve outcomes, younger donors should be sought, and clinicians should attempt to reduce peripheral blasts in patients who are in relapse.

The role of single nucleotide polymorphisms (SNPs) in understanding complex disorders and pharmacogenomics

INTRODUCTION

In the last two years, there has been an increasing interest in single nucleotide polymorphisms (SNPs). They have been hailed as the most common polymorphism found in the human genome and are believed to be responsible for 90% of all inter-individual variation. Efforts are now directed at the large-scale identification and archiving of SNPs in the human genome. Not only are they useful markers for population divergence studies, SNPs can be utilised as markers in studies of complex diseases and pharmacogenomics.

METHODS

Traditional methods for identifying SNPs, as well as methods for large-scale detection and genotyping of SNPs currently being developed, are briefly discussed in this review. Such developments will facilitate and enhance the process of identifying and characterising genes and their functions.

RESULTS

The utility of SNPs in identifying genes contributing to pharmacogenetic variation and increased risk of a complex disease is discussed. The role of SNPs in influencing drug response in different individuals is also presented.

CONCLUSIONS

In helping to unravel the genetic basis of complex diseases and inter-individual variation in drug response, SNPs will catalyse the transition into a new age of medicine in which medical care is tailored to the individual's genetic profile.

Combined analysis of germline polymorphisms of p53, GSTM1, GSTT1, CYP1A1, and CYP2E1: relation to the incidence rate of cervical carcinoma

BACKGROUND

The authors established the genotype frequencies of cytochrome P450 (CYP1A1/MspI, CYP2E1/PstI, and CYP2E1/DraI), glutathione-S-transferase (GSTM1 and GSTT1), and p53 (exon 4/AcclI and intron 3/16-base pair duplication) gene polymorphisms in cervical carcinoma patients and controls and evaluated the association between the specific genotype or genotype combinations of these polymorphisms and the risk of cervical carcinoma.

METHODS

In this case-control study, the genotypes of 181 human papillomavirus (HPV)-16 or HPV-18 positive cervical carcinoma patients and 1-to-1 age-matched controls were determined using a polymerase chain reaction-based technique.

RESULTS

Among these polymorphisms, the individuals carrying arginine/proline genotypes of p53 showed a 9.5-fold increase of cervical carcinoma risk (95% confidence interval [CI], 4.9-18.6) compared with those individuals carrying arginine/arginine genotypes. The frequency of overall GSTT1 null genotypes also was significantly higher in cervical carcinoma patients compared with that of GSTT1 positive genotypes (P = 0.003; odds ratio [OR] = 1.9; 95% CI, 1.2-2.9). The genotype combination of p53 and GST played a more important role in describing the relative risk of cervical carcinoma. The individuals carrying both the arginine/proline genotype of p53 and the null genotype of GSTT1 showed a 3.5-fold increase of cervical carcinoma risk (95% CI, 1.8-7.1) compared with those individuals carrying both the arginine/arginine genotype of p53 and the GSTT1 positive genotype. In the patients who were stratified into the two age groups, the null genotypes of GSTT1 (69.1% vs. 45.5%; P = 0.016) and GSTM1 (61.8% vs. 40.0%; P = 0.028) in cervical carcinoma were significantly overrepresented in the younger age subgroup (age 40 years or younger) compared with those of controls. Especially in this age group, the individuals carrying both null genotypes of GSTT1 and GSTM1 showed a 17.8-fold increase of cervical carcinoma risk (95% CI, 2.2-141.0) compared with the individuals carrying both positive genotypes of GSTT1 and GSTM1.

CONCLUSIONS

The results of the current study suggested that the arginine/proline genotype of p53, independently or in conjunction with the GSTT1 null genotype, could affect the genetic susceptibility for cervical carcinoma, and HPV positive women carrying both null genotypes of GSTT1 and GSTM1 have an increased risk of cervical carcinoma developing before age 40 years.

Internal cleavage of hepatitis C virus NS3 protein is dependent on the activity of NS34A protease

The nonstructural protein NS3 of the hepatitis C virus (HCV) is indispensable for virus replication and a multifunctional enzyme that contains three catalytic activities such as serine protease, helicase, and NTPase. Here, we demonstrated that the internal cleavage of the HCV NS3 protein occurs in various mammalian cells such as HepG2, COS-7, and NIH3T3. As is observed for the internal cleavage mechanism of the NS3 protein of dengue virus 2, the internal processing of HCV NS3 protein was catalyzed by the active NS3 serine protease and NS4A, but not NS3 alone. From the data acquired from extensive site-directed mutagenesis, we observed that the NS3 protein was internally cleaved at two different sites, FCH(1395) ||S(1396)KK and IPT(1428) ||S(1429)GD, within RNA helicase domain. The internal cleavage of NS3 protein by NS34A protease was also confirmed in a different isolate of HCV-1b strain. In addition, in vitro transforming assays demonstrated that the internal cleavage product of NS3, NS3a-1, appeared to have higher oncogenic potential than does intact NS3. Taken together, our results suggest that the internal cleavage of NS3 may be associated with the replication and oncogenesis of HCV.

The c-myc locus is a common integration site in type B retrovirus-induced T-cell lymphomas

Type B leukemogenic virus (TBLV) induces rapidly appearing T-cell leukemias. TBLV insertions near the c-myc gene were detectable in 2 of 30 tumors tested, whereas 80% of the tumors showed c-myc overexpression. TBLV insertions on chromosome 15 (including a newly identified locus, Pad7) may cause c-myc overexpression by cis-acting effects at a distance.

Effect of ABC transporters on HIV-1 infection: inhibition of virus production by the MDR1 transporter

The MDR1 multidrug transporter P-gp (P-glycoprotein) is an efflux pump that extrudes diverse hydrophobic drugs and peptides from cells. Since the entry of HIV-1 into cells involves an initial interaction of the viral gp41 hydrophobic peptide with the plasma membrane, a potential effect of P-gp on HIV-1 infectivity was explored. Virus production was greatly decreased when P-gp was overexpressed at the surface of a continuous CD4(+) human T-leukemic cell line (12D7) infected with HIV-1(NL4-3), a T-tropic molecular clone of HIV-1. P-gp overexpression did not significantly alter the surface expression or distribution of either the HIV-1 receptor CD4 or the coreceptor CXCR4. Reduction of HIV-1 infectivity in P-gp-expressing cells occurred both during the fusion of viral and plasma membranes and at subsequent step(s) in the HIV-1 life cycle.

Adsorption of a mixture of Thiobacillus thiooxidans and Thiobacillus ferrooxidans onto copper-containing furnace dust

The Langmuir adsorption parameter X(Am) of a mixture of culture of Thiobacillus ferrooxidans and Thiobacillus thiooxidans indicates that these bacteria have preferential and competitive adsorption sites on furnace dust. The constant K(A) of the mixture significantly larger than that of each component, suggesting that a synergistic effect may occur in the binding of these bacteria to the dust.

Clinical significance of neck node metastasis in squamous cell carcinoma of the maxillary antrum

PURPOSE

To further clarify the clinical significance of neck node metastasis in squamous cell carcinoma of the maxillary sinus (maxillary SCC).

MATERIALS AND METHODS

The medical charts of the 116 patients with maxillary SCC were retrospectively reviewed. Twelve patients (10.3%) presented initially with neck node metastases, and 14 (13.5%) of 104 node-negative patients subsequently developed regional recurrence during the follow-up period. The high-risk factors for neck node metastasis, patterns of regional failure, and survival for node-positive patients were analyzed with the patient cohort that had largely been treated with radiation alone.

RESULTS

Of the various factors, the tumor extension to the nasopharynx or oral cavity was the statistically significant determinants predictive of neck node metastasis at the initial diagnosis. During the follow-up period, regional failure was far less common than local failure (19.0% v 68.1%), and the majority of regional failures were accompanied by local recurrences. The oral cavity extension and control status of local disease were the high-risk factors for subsequent development of regional recurrence in node-negative patients. The overall 5-year survival rate for node-positive patients (16.7%) showed a poorer outcome compared with that for node-negative patients (31.3%), but it was similar to that of T4N0 patients (26.6%). Although patients who subsequently developed neck node recurrence during follow-up represented a dismal prognosis, uncontrolled local diseases in these patients still remained a major problem, resulting in a poor prognosis.

CONCLUSIONS

Despite an unfavorable prognosis of patients with neck node metastasis, an aggressive trial to achieve maximum local control of the primary tumor was considered to be more important than elective neck treatments.

Effect of eradication of Helicobacter pylori on the benign gastric ulcer recurrence--a 24 month follow-up study

OBJECTIVES

To evaluate the effect of eradication of Helicobacter pylori (H. pylori) on the recurrence of benign gastric ulcer (BGU) in the patients with BGU.

METHODS

This study was performed for 40 H. pylori-positive BGU patients cured of BGU and H. pylori eradicated, and for 25 H. pylori-positive patients (non-eradicated group) who were not treated with H. pylori eradication regimen or H. pylori was not eradicated. Four different methods--CLOtest, microscopy of Gram stained mucosal smear, culture and histology of modified Giemsa staining--were taken for identifying colonization of H. pylori before treatment, and 4 weeks after completion of triple therapy. For the control group in which triple therapy was not tried, follow-up gastroscopy was done to confirm the healing of the ulcer. To detect BGU recurrence, the gastroscopy was performed at 6, 12, 18, and 24 months after therapy.

RESULTS

In the non-eradicated group, the BGU recurrence rate was 16% within 6 months, 40% within 1 year, 56% within 18 months and 60% within 2 years. The respective recurrence rates in the 40 patients in whom the bacteria had been eradicated were 0%, 7.5%, 10% and 10% (4 patients), respectively. Among the four BGU-recurred patients in whom H. pylori had been eradicated, one patient was found to have BGU recurring with H. pylori positive again in one year, and another two patients had NSAIDs ingestion history.

CONCLUSION

The eradication of H. pylori in patients with BGU reduces the recurrence of BGU. In addition, the major causes of BGU recurrence look like NSAIDs ingestion and reinfection of H. pylori.

Molecular cloning and functional expression of the mouse gap junction gene connexin-57 in human HeLa cells

A new mouse connexin gene has been isolated that codes for a connexin protein of 505 amino acid residues. Based on the predicted molecular mass of 57.115 kDa, it has been designated connexin-57. Similar to most other mouse connexin genes, the coding region of connexin-57 is not interrupted by introns and exists in the mouse genome as a single-copy gene. Within the connexin family, this new gene shows highest sequence identity to porcine connexin-60 in the alpha group of connexins. The connexin-57 gene was mapped to a position on mouse chromosome 4, 30 centimorgans proximal to a cluster of previously mapped connexin genes. Low levels of connexin-57 mRNA were detected in skin, heart, kidney, testis, ovary, intestine, and in the mouse embryo after 8 days post coitum, but expression was not detected in brain, sciatic nerve or liver. In order to analyze gene function, the connexin-57 coding region was expressed by transfection in human HeLa cells, where it restored homotypic intercellular transfer of microinjected neurobiotin. Heterotypic transfer was observed between HeLa connexin-57 transfectants and HeLa cells, expressing murine connexin-43, -37, or -30.3. Double whole-cell voltage clamp analyses revealed that HeLa-connexin-57 transfectants expressed about 10 times more channels than parental HeLa cells. Voltage gating by transjunctional and transmembrane voltages as well as unitary conductance ( approximately 27 picosiemens) were different from intrinsic connexin channels in parental HeLa cells.