Search PubMed⌕ Search

Biomedical subjects

L S Young

Publications and source records attributed to L S Young.

At least 37 records · Page 2Linked to original sources
PubMed2002

CD40 activation in epithelial ovarian carcinoma cells modulates growth, apoptosis, and cytokine secretion.

BACKGROUND/AIMS: CD40, a member of the tumour necrosis factor (TNF) receptor family, is expressed on a variety of haematopoietic cells and is crucial in orchestrating both humoral and cellular immune responses. CD40 is also expressed on some carcinoma cells, where its function remains largely unknown. This study investigated the effects of CD40 ligation on ovarian carcinoma cell growth and apoptosis and on cytokine production, in addition to the role of the NF-kappa B and JNK signalling pathways. METHODS: CD40 expression was measured in epithelial ovarian carcinoma (EOC) biopsies by immunohistochemistry and in EOC cell lines by flow cytometry. To examine the effects of CD40 ligation on cell growth recombinant soluble CD40 ligand was used to stimulate EOC cell lines and growth was measured by MMT assays. Cytokine production was measured by enzyme linked immunosorbent assays interleukin 8 (IL-8) gene transcription was estimated by means of reverse transcription polymerase chain reaction. The integrity of the CD40 signalling pathway in those cell lines that did not produce cytokines in response to CD40 ligation was assessed by the detection of the transcription factor NF-kappa B by an electrophoretic mobility shift assay. To investigate the defect in the NF-kappa B pathway the phosphorylation status of I kappa B alpha was determined by an antibody specific to phosphorylated I kappa B alpha and dissociation of the I kappa B alpha-p65 complex was assessed by co-immunoprecipitation. RESULTS: CD40 is expressed in primary ovarian carcinoma biopsies and EOC cell lines. CD40 ligation resulted in growth inhibition in most of these carcinoma cell lines and was also found to promote apoptosis, with this last effect only being evident in early passage EOC cells. CD40 ligation also induced significant IL-6 and IL-8 production in most of the EOC cell lines examined and it was confirmed for IL-8 that this effect was regulated at the transcriptional level. NF-kappa B activation in response to CD40 ligation was found in three of the EOC cell lines and specific defects in the CD40 induced NF-kappa B pathway were identified in two cell lines. However, CD40 engagement induced JNK activation in all the EOC cell lines. CONCLUSIONS: These data suggest that the CD40 pathway is functional in ovarian carcinoma cells and highlight the need for further studies to provide insight into the role of CD40 in the carcinogenic process and the possible exploitation of this pathway for novel therapeutic approaches.

Antibodies, Monoclonal↗
PubMed2001

Epstein-Barr virus infection: basis of malignancy and potential for therapy.

The Epstein-Barr virus (EBV) is a human herpesvirus that is usually carried lifelong as an asymptomatic infection. EBV is the causative agent of infectious mononucleosis and has been linked to the development of several malignant tumours, including B-cell neoplasms such as Burkitt's lymphoma and Hodgkin's disease, certain forms of T-cell lymphoma, and some epithelial tumours, such as undifferentiated nasopharyngeal carcinoma and a proportion of gastric cancers. All these tumours are characterised by the presence of multiple extrachromosomal copies of the circular viral genome in the tumour cells and the expression of EBV-encoded latent genes, which appear to contribute to the malignant phenotype. An increasing understanding of the function of EBV latent genes and of the nature of the immune response to the virus is providing exciting new possibilities for the treatment of EBV-associated malignancies. For example, adoptive transfer of virus-specific cytotoxic T lymphocytes has already been of value in the treatment of EBV-positive B-cell lymphomas arising in post-transplant patients, and this approach is currently being investigated in other EBV-associated tumours. In addition, gene therapy offers the opportunity to deliver agents that might directly interfere with the function of specific EBV genes. This review summarises the role of EBV in malignancy. In particular, it focuses on the latent proteins as a basis for understanding how EBV might contribute to the process of transformation. Strategies to target EBV in tumours, potentially providing alternative therapeutic approaches, are also discussed.

Journal Article↗
PubMed2001

The Epstein-Barr virus encoded latent membrane protein 2A augments signaling from latent membrane protein 1.

The frequent coexpression of the EBV-encoded latent membrane proteins LMP1 and LMP2A/B in virus-associated tumors suggests that these two proteins may cooperate in the transformation process. While LMP2A is unable to directly activate the NF-kappaB and AP-1 pathways, we found that coexpression of LMP2A with LMP1 resulted in a significant enhancement of LMP1-mediated activation of these pathways. This enhancement was found to be critically dependent on the tyrosine residues present within the ITAM motif (Y74/Y85) and, to a lesser extent, the tyrosine at position 112 (Y112). Subsequent analysis revealed that LMP2A is able to stabilize and modulate the turnover of LMP1 by extending its half-life. This ability does not require a direct physical interaction between the two proteins but rather, results from an indirect effect of LMP2A on the turnover of the LMP1 protein. This study highlights an important role for LMP2A as a modulator of LMP1 activity in epithelial cells.

Blotting, Western↗
PubMed2001

Perspective on animal models: chronic intracellular infections.

Systemic human disease caused by organisms of the Mycobacterium avium-Mycobacterium intracellulare complex (MAC) represent a chronic intracellular infection in human hosts who are usually immunocompromised. To develop improved treatment and prophylaxis, and to obtain a better understanding of pathogenesis, we studied the beige mouse (C57 beige(+)/beige(+)) challenged orally or intravenously with a human isolate that causes lethal disease in patients with AIDS (MAC 101, serovar 1). Encouraging anti-MAC studies in animals, as reviewed here, should provide the basis for considering human trials with a promising agent. The ability of an antimicrobial agent to achieve high intracellular concentrations has correlated with the in vivo activity of several specific compounds.

Animals↗
PubMed2001

South Asian ethnicity and material deprivation increase the risk of Epstein-Barr virus infection in childhood Hodgkin's disease.

In order to further define the factors associated with the observed variations in the Epstein-Barr virus-positive rate in childhood Hodgkin's disease, we have studied the effect of material deprivation (measured by the Townsend score) and ethnic origin on the frequency of Epstein-Barr virus-positivity in 55 cases of childhood Hodgkin's disease, diagnosed between 1981 and 1999, from a multi-ethnic region of the United Kingdom. Epstein-Barr virus status was determined by immunohistochemistry for the Epstein-Barr virus-encoded latent membrane protein-1. 62% of cases were Epstein-Barr virus-positive. Ethnic group was the strongest predictor of Epstein-Barr virus-positivity, with South Asians having a more than 20-fold risk of being Epstein-Barr virus-positive compared with non-South Asians. An increased risk was still present after adjusting for deprivation. Townsend scores were significantly higher (indicating more deprivation) in the Epstein-Barr virus-positive group, particularly in males. The relative risk of Epstein-Barr virus-positivity showed a gradient with increasing Townsend score; the risk being 7-times higher in the most deprived quartile compared with the least deprived group. Although the association between Townsend score and Epstein-Barr virus-positivity was reduced after adjusting for ethnic group, the risk of Epstein-Barr virus-positivity was still 3-times higher in the most deprived compared with the least deprived quartile. In addition, cases having 2 or more siblings were 5-times as likely to be Epstein-Barr virus-positive as those from smaller families. These results provide the first evidence of a strong association between Epstein-Barr virus-positive Hodgkin's disease and South Asian children from the United Kingdom. In addition, deprivation may increase the likelihood of Epstein-Barr virus-positive disease independently of ethnicity.

Adolescent↗
PubMed2001

Natural history of cervical human papillomavirus infection in young women: a longitudinal cohort study.

BACKGROUND: Laboratory and epidemiological research suggests an association between human papillomavirus (HPV) and cervical intraepithelial neoplasia (CIN). We studied the natural history of incident cervical HPV infection and its relation to the development of CIN. METHODS: We recruited 2011 women aged 15-19 years who had recently become sexually active. We took a cervical smear every 6 months and stored samples for virological analysis. We immediately referred all women with any cytological abnormality for colposcopic assessment, but postponed treatment until there was histological evidence of progression to high-grade CIN. FINDINGS: In 1075 women who were cytologically normal and HPV negative at recruitment, the cumulative risk at 3 years of any HPV infection was 44% (95% CI 40-48): HPV 16 was the most common type. The cumulative risk at 3 years of detecting an HPV type not present in the first positive sample was 26% (20-32). 246 women had an abnormal smear during follow-up, of whom 28 progressed to high-grade CIN. The risk of high-grade CIN was greatest in women who tested positive for HPV 16 (risk ratio 8.5 [3.7-19.2]); this risk was maximum 6-12 months after first detection of HPV 16. All HPV types under consideration were associated with cytologically abnormal smears. Although abnormality was significantly less likely to be associated with low-viral-load samples, the cumulative risk at 3 years of a high-viral-load sample after a low-viral-load sample was 45% (95% CI 35-56). Five women who progressed to high-grade CIN consistently tested negative for HPV. INTERPRETATION: Our findings suggest that attempts to exploit the association between cervical neoplasia and HPV infection to improve effectiveness of cervical screening programmes might be undermined by the limited inferences that can be drawn from the characterisation of a woman's HPV status at a single point in time, and the short lead time gained by its detection.

Adolescent↗
PubMed2001

The transmembrane domains of the EBV-encoded latent membrane protein 1 (LMP1) variant CAO regulate enhanced signalling activity.

Sequence variants of the Epstein-Barr virus (EBV)-encoded latent membrane protein-1 (LMP1) have been reported in association with EBV-linked malignancies but little is known about their effects on signalling pathways and phenotype. We have examined the ability of the nasopharyngeal carcinoma (NPC)-derived variant, CAO-LMP1 to activate the transcription factors NF-kappaB and AP-1 in epithelial cells. In this study, transient expression of CAO-LMP1 was found to activate higher levels of NF-kappaB and AP-1 than the prototype B95.8-LMP1 in human embryonic kidney (HEK) 293 cells and SV40-transformed keratinocytes (SVK). In addition, pulse-chase analysis revealed that CAO-LMP1 has a longer half-life than B95.8-LMP1. Chimera studies localised these phenomena to the transmembrane domains of CAO-LMP1, suggesting that this enhanced signalling capacity may be a consequence of its prolonged half-life. The ability of CAO-LMP1 to activate higher levels of NF-kappaB and AP-1 may contribute to its potent transforming properties.

Cell Line↗
PubMed2001

Expression of cytokine and chemokine genes in Epstein-Barr virus-associated nasopharyngeal carcinoma: comparison with Hodgkin's disease.

Nasopharyngeal carcinoma (NPC) and Hodgkin's disease (HD) are characterized by their association with Epstein-Barr virus (EBV) and the presence of an intense lymphoid stroma, consisting of T lymphocytes and other reactive cells. In both entities, the tumour cells express viral proteins known to provide target epitopes for cytotoxic T-cells (CTLs), yet in vivo, the tumour cells appear to escape CTL recognition. A comparative in situ hybridization study of cytokine and chemokine gene expression in NPC and HD has been undertaken, focusing on cytokines which are known to be inducible by EBV in vitro. Hodgkin and Reed-Sternberg (HRS) cells expressed interleukin (IL)-6, IL-8, and IL-10, and the thymus and activation regulated chemokine (TARC) in 15/22, 0/22, 5/22, and 16/21 cases, respectively. In NPC, the epithelial tumour cells showed expression of IL-6 in 3/43 cases and of IL-8 in 2/40 cases. There was no detectable expression of IL-10 and TARC in these cases. These data confirm that HRS cells frequently express cytokine and chemokine genes and suggest that this may enable HRS cells to modulate the immune response in their microenvironment and to escape CTL detection. In contrast, NPC tumour cells show only rare expression of IL-6 and IL-8 and no detectable expression of IL-10 and TARC. Thus, the results suggest that the mechanisms employed by the EBV-positive tumour cells to escape immune recognition and destruction differ between HD and NPC.

Carcinoma↗
PubMed2001

Expression of the tumour necrosis factor receptor-associated factors 1 and 2 in Hodgkin's disease.

The tumour necrosis factor receptor-associated factors (TRAFs) 1 and 2 participate in the signal transduction of various members of the tumour necrosis factor receptor (TNFR) family, including TNFR1, TNFR2, CD40, CD30, and the Epstein-Barr virus (EBV)-encoded latent membrane protein-1 (LMP1). Previous in situ hybridization studies have demonstrated TRAF1 transcripts in the malignant cells of the majority of Hodgkin's disease (HD) tumours, where the expression of TRAF1 was higher in EBV-associated tumours than in their EBV-negative counterparts. In order to determine whether TRAF1 and also TRAF2 were expressed at the protein level in HD and whether there was any relationship to EBV status, immunohistochemistry has been used to detect these proteins in a series of HD specimens. TRAF1 protein was detected more frequently in Hodgkin/Reed-Sternberg (HRS) cells from EBV-positive tumours than in their EBV-negative counterparts. This difference was statistically significant (p=0.01). In contrast, TRAF2 expression by HRS cells appeared to be independent of EBV status. Using a sequential labelling approach, co-localization of LMP1 with either TRAF1 or TRAF2 was also demonstrated in HRS cells from EBV-positive tumours.

Blotting, Western↗
PubMed2001

Combined adenovirus-mediated nitroreductase gene delivery and CB1954 treatment: a well-tolerated therapy for established solid tumors.

Gene-directed enzyme prodrug therapy (GDEPT) is a refinement of cancer chemotherapy that generates a potent cell-killing drug specifically in tumor cells by enzymatic activation of an inert prodrug. We describe in vivo studies that evaluate the efficacy and safety of intratumoral (i.t.) injection of an adenovirus vector (CTL102) expressing Escherichia coli nitroreductase (NTR) combined with systemic prodrug (CB1954) treatment. A single i.t. injection of CTL102 (7.5 x 10(9) to -2 x 10(10) particles) followed by CB1954 treatment produced clear anti-tumor effects in subcutaneous (s.c.) xenograft models of four cancers that are likely candidates for GDEPT (i.e., primary liver, head and neck, colorectal and prostate). Virus dose-response studies (s.c. liver model) revealed a steep increase and subsequent rapid plateauing of both NTR gene delivery and anti-tumor efficacy. Evidence of minor virus spread (toxicity) was observed in a s.c. head and neck xenograft model. This was eliminated by passive immunization with neutralizing anti-Ad5 antibodies prior to virus injection without reducing the magnitude of the anti-tumor effect. Preexisting anti-Ad5 neutralizing antibodies may therefore be an advantage rather than an issue in the clinical use of this new therapy.

Adenoviridae↗
PubMed2001

High-level, beta-catenin/TCF-dependent transgene expression in secondary colorectal cancer tissue.

There is an urgent need for improved therapies for inoperable metastatic colon cancer. Gene-directed enzyme prodrug therapy (GDEPT) using adenovirus vectors works well in preclinical models of this disease, but successful clinical application is hampered by an inability to construct vectors that express at high levels in infected tumor cells but not in infected normal cells. Constitutive activation of beta-catenin-dependent gene expression is almost certainly a key causative event in the genesis of colon and some other cancers. Here we have exploited this oncogenic defect to design a synthetic promoter, CTP1, that, in contrast to currently available tumor-selective promoters, is both highly active in cancer cells and highly cancer-cell-specific. CTP1 directs high-level beta-galactosidase expression in freshly isolated biopsies of secondary colon cancer, but is not detectably active in associated normal liver tissue. We also demonstrate that CTP1 can direct high-level, tumor-specific therapeutic gene expression in vivo. Intratumoral injection of an adenovirus vector encoding Escherichia coli nitroreductase driven by CTP1 efficiently sensitized SW480 xenografts to the prodrug CB1954, whereas systemic vector and prodrug administration produced no apparent signs of toxicity. CTP1 may form the basis for effective, targeted gene therapy of metastatic colon cancer and other tumors with deregulated beta-catenin/T cell factor.

Adenoviridae↗
PubMed2001

LMP1 structure and signal transduction.

The oncogenic Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) has structural features and functions reminiscent of a constitutively active TNF family receptor. LMP1 aggregates at the plasma membrane and initiates the activation of signalling pathways, such as NF- kappa B, the mitogen-activated protein kinases JNK and p38, the small GTPase Cdc42 and the JAK/STAT cascade. The constitutive engagement of these signals and the characteristic molecular interactions that regulate them provide the basis for the molecular explanation of the transforming properties of this key EBV protein.

Amino Acid Sequence↗
PubMed2001

Epithelial pigment slide in contact lens wearers: a possible marker for contact lens-associated stress on corneal epithelium.

PURPOSE: To compare the incidence of epithelial pigment slide among wearers of various types of contact lenses. METHODS: Prospectively, we studied 432 eyes of 432 patients. The patients were separated into 6 groups: hard contact lens (HCL) wearers (n = 166), conventional soft contact lens (CSCL) wearers (n = 30), extended disposable lens (EDCL) wearers (n = 46), frequent replacement SCL (FRCL) wearers (n = 60), daily disposable SCL (DDCL) wearers (n = 65), and normal controls (n = 65). The incidence of prominent pigment slide, defined as spike-like epithelial opacities in the corneal limbus and longer than 1 mm from the base to the apex of the wedges-shaped process detected by slit-lamp examination, was compared in these 6 groups. The relationship between the incidence of prominent pigment slide and the length of contact lens wear was examined. RESULTS: The overall incidence of prominent pigment slide in the CSCL, EDCL, HCL, FRCL, DDCL, and normal groups was 63.3, 23.9, 13.9, 8.3, 7.7, and 4.6%, respectively. The incidence of prominent pigment slide in the CSCL and EDCL groups was significantly higher than that in the control group. A higher incidence of prominent pigment slide was correlated with longer wearing period in each group. CONCLUSIONS: The presence of epithelial pigment slide may be a marker for contact lens-associated stress to the corneal epithelium.

Biomarkers↗
PubMed2001

An autoradiographic study of regional blood flow distribution in the rat kidney during ureteric obstruction--the role of vasoactive compounds.

OBJECTIVE: To determine the changes in regional renal blood flow during ureteric obstruction and to examine the role of vasoactive mediators in effecting these changes. MATERIALS AND METHODS: Renal blood flow in Sprague-Dawley rats was assessed after periods of ureteric obstruction using a quantitative autoradiographic technique based on Kety's theory of diffusion of an inert tracer (14C-iodoantipyrine). Prostaglandins, thromboxanes and renin-angiotensin were inhibited pharmacologically using diclofenac sodium and enalapril. RESULTS: Baseline blood flow to the outer cortex, inner cortex and medulla was 807, 258 and 105 mL/100 g/min, respectively. There was an increase in outer cortical blood flow after 10 min of ureteric obstruction which became significant at 30 min (P < 0.05). There was a significant decrease in inner cortical and medullary blood flow at 30 min, to 210 and 68 mL/100 g/min, respectively (P < 0.05). Diclofenac sodium abolished the increase in outer cortical blood flow. After 24 h of unilateral ureteric obstruction, outer cortical blood flow decreased to 492 mL/100 g/min; inner cortical blood flow also decreased but to a lesser extent, to 190 mL/100 g/min. Inhibition of prostaglandins, thromboxanes and the renin-angiotensin system reduced the degree of renal vasoconstriction but there was still a significant decrease in outer cortical perfusion despite the presence of these blocking agents. CONCLUSIONS: The control of the renal vasculature involves a complex interplay between a variety of vasoactive mediators. Quantitative autoradiography offers the opportunity to evaluate changes in regional renal perfusion with high resolution and will allow a greater understanding of the pathophysiology of renal diseases.

Animals↗
PubMed2001

Nitric oxide in unilateral ureteral obstruction: effect on regional renal blood flow.

BACKGROUND: Ureteral obstruction (UO) is characterized by reduced blood flow and loss of tissue mass in the involved kidney(s). Vasoactive mediators interact to produce an initial hyperemia, followed by a sustained decrease in renal blood flow in the obstructed kidney. Nitric oxide (NO) has been shown to play a central role in the acute hyperemic response to UO. Its role in the reduced perfusion of prolonged UO is less studied. METHODS: Ureteral obstruction was achieved by ligation of the distal left ureter and maintained for 24 hours. Blood flow was studied in untreated animals and after the administration of the NO synthase (NOS) inhibitor N-mono-methyl L-arginine and the NO donor sodium nitroprusside. Tissue was collected for localization and quantitation of NOS. Serum and renal tissue L-arginine levels were measured in control and UO settings. RESULTS: Blood flow in the obstructed kidney diminished to approximately 50% of control values after 24 hours of UO. NOS blockade led to a further decrease in blood flow. Supplementation with exogenous nitrates restored renal blood flow to levels approaching control values. Serum and tissue L-arginine levels did not change with UO. NOS expression was seen to increase with increasing duration of obstruction, with staining most pronounced in the renal tubules. CONCLUSIONS: NO plays a vasodilatory role even in the hypoperfusion of prolonged UO. The administration of exogenous nitrates has a restorative effect on blood flow, suggesting therapeutic potential in UO.

Animals↗
PubMed2001

Frequent expression of the tumor necrosis factor receptor-associated factor 1 in latent membrane protein 1-positive posttransplant lymphoproliferative disease and HIV-associated lymphomas.

The tumor necrosis factor receptor-associated factor 1 (TRAF1) participates in the signal transduction of various members of the tumor necrosis factor receptor (TNFR) family, including TNFR2, CD40, CD30, and the Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1). In vitro, TRAF1 is induced by LMP1, and previous studies have suggested that expression of TRAF1 is higher in EBV-associated tumors than in their EBV-negative counterparts. To determine whether this was the case in posttransplant lymphoproliferative disease (PTLD) and related disorders, we used immunohistochemistry to analyze expression of TRAF1 in a total of 42 such lesions arising in a variety of immunosuppressive states. The specimens consisted of 22 PTLD lesions, 18 acquired immunodeficiency syndrome-associated lymphomas, including 6 primary central nervous system lymphomas, and 2 cases of Hodgkin disease. The presence of latent EBV infection was determined by EBER in situ hybridization, and expression of EBV-LMP1 was detected by immunohistochemistry. Latent EBV infection, as determined by a positive EBER signal, was detected in 36 of 42 tumors. Of the EBER-positive specimens, 30 of 36 also expressed LMP1. Twenty-four of 30 LMP1-positive tumors, including both Hodgkin disease specimens, expressed TRAF1, compared with only 3 of 12 LMP1-negative tumors. This difference was statistically significant (P <.005). These results show frequent expression of TRAF1 at the protein level in LMP1-positive PTLD and related disorders and suggest an important role for LMP1-mediated TRAF1 signaling in the pathogenesis of EBV-positive tumors arising in immunosuppressive states.

Epstein-Barr Virus Infections↗
PubMed2001

CD40 activation-induced, Fas-dependent apoptosis and NF-kappaB/AP-1 signaling in human intrahepatic biliary epithelial cells.

Fas-mediated mechanisms of apoptosis are thought to be involved in the bile duct loss that characterizes diseases such as primary biliary cirrhosis (PBC). We have previously shown that activation of CD40 on hepatocytes can amplify Fas-mediated apoptosis; in the present study, we investigated interactions between CD40 and Fas in biliary epithelial cells (BEC). We report that the bile ducts in PBC liver tissue frequently express increased levels of Fas, Fas ligand (FasL), and CD40 associated with apoptotic BEC. The portal mononuclear infiltrate contains CD40L+ve T cells and macrophages, thereby demonstrating a potential mechanism for CD40 engagement in vivo. Primary cultures of human BEC also expressed Fas, FasL, and CD40 but not CD40L protein or mRNA. Activation of CD40 on BEC using recombinant CD40L increased transcriptional expression of FasL and induced apoptosis, which was inhibited by neutralizing antibodies to either Fas or FasL. Thus, CD40-induced apoptosis of BEC is mediated through Fas/FasL. We then investigated the intracellular signals and transcription factors activated in BEC and found that NF-kappaB and AP-1 were both activated after CD40 ligation. Increased functional NF-kappaB was seen early after CD40 ligation, but returned to baseline levels after 4 h. In contrast, the rapid up-regulation of AP-1 was sustained over 24 h. This study provides further functional evidence of the ability of CD40 to induce Fas/FasL-dependent apoptosis of liver epithelial cells supporting the importance of cross-talk between tumor necrosis factor (TNF) receptor family members as an amplification step in apoptosis induction. Sustained activation of AP-1 in the absence of NF-kappaB signaling may be a critical factor in determining the outcome of CD40 engagement.

Apoptosis↗