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Biomedical subjects

Tim Oliver

Publications and source records attributed to Tim Oliver.

16 recordsLinked to original sources
PubMed2006

Efficient dendritic cell priming of T lymphocytes depends on the extracellular matrix protein mindin.

Rho guanosine triphosphatases (GTPases) regulate multiple aspects of dendritic cell (DC) function, but what regulates the expression of Rho GTPases in DCs is unknown. Here, we show that the extracellular matrix protein mindin regulates the expression of Rho GTPases in DCs. Mindin(-/-) mice displayed defective CD4+ T-cell priming and impaired humoral immune responses to T-dependent antigens. Mindin(-/-) DCs had reduced expression of Rac1/2 and impaired priming capacity owing to inefficient engagement with T lymphocytes. Ectopic Rac1 expression restored the priming capability of Mindin(-/-) DCs. Furthermore, we show that DC adhesion to mindin matrix was blocked by antibodies to alpha4, alpha5 and beta1 integrins. DCs lacking beta1 integrin had reduced adhesion to mindin matrix, decreased expression of Rac1/2 and impaired priming capacity. These results suggest that mindin-integrin interactions play a key role in regulating Rho GTPase expression in DCs and DC priming of T lymphocytes.

Animals↗
PubMed2006

Evidence that autocrine signaling through Bmpr1a regulates the proliferation, survival and morphogenetic behavior of distal lung epithelial cells.

Lung development requires reciprocal epithelial/mesenchymal interactions, mediated by signaling factors such as Bmps made in both cell populations. To address the role of Bmp signaling in the epithelium, we have exploited the fact that Bmp receptor type Ia (Alk3) is expressed in the epithelium during branching morphogenesis. Deletion of Bmpr1a in the epithelium with an Sftpc-cre transgene leads to dramatic defects in lung development. There is reduced epithelial proliferation, extensive apoptosis, changes in cell morphology and extrusion of cells into the lumen. By E18.5, there are fewer Type II cells than normal, and the lung contains large fluid-filled spaces. If cell death is prevented by making embryos homozygous null for the proapoptotic gene, Bax, the epithelial cells that are rescued can apparently differentiate, but normal morphogenesis is not restored. To determine whether Bmps made by the epithelium can function in an autocrine manner, mesenchyme-free endoderm was cultured in Matrigel with Fgfs. Under these conditions, the mutant epithelium fails to undergo secondary budding. Abnormal development was also seen when Bmp4 was specifically deleted in the epithelium using the Sftpc-cre transgene. Our results support a model in which Bmp signaling primarily regulates the proliferation, survival and morphogenetic behavior of distal lung epithelial cells.

Animals↗
PubMed2006

Risk and presenting features of prostate cancer amongst African-Caribbean, South Asian and European men in North-east London.

OBJECTIVE: To determine whether there are ethnic differences in the incidence and presenting features of all patients with prostate cancer presenting in North-east London, UK. PATIENTS AND METHODS: All newly diagnosed men with prostate cancer between 1999 and 2000 who were resident in the East London and City Health Authority were identified from various sources. Key clinical features were extracted from hospital records. The age-adjusted incidence rates for European, South Asian and African-Caribbean patients were calculated using census denominator data. RESULTS: For men aged >50 years the annual age-adjusted incidence rates (95% confidence interval) were 213 (186-240), 647 (504-789) and 199 (85-310) for the European, African-Caribbean and South Asian patients, respectively. African-Caribbean men had a three times greater risk (risk ratio 3.07, 2.40-3.93, P < 0.001) than European men. South Asian men had a lower risk of prostate cancer but this could have been compatible with chance. There was no evidence of marked ethnic differences for prostate-specific antigen levels, clinical staging and Gleason scores. CONCLUSION: The greater risk of prostate cancer for African-Caribbean men in South-east England is consistent with data from the USA and the Caribbean. Future work needs to determine whether this risk differs according to country of origin, and which genetic and/or environmental risk factors might be important in explaining these observations.

Africa↗
PubMed2006

Three-dimensional imaging of xenograft tumors using optical computed and emission tomography.

The physical basis and preliminary applications of optical computed tomography (optical-CT) and optical emission computed tomography (optical-ECT) are introduced, as new techniques with potential to provide unique 3D information on a variety of aspects of tumor structure and function. A particular focus here is imaging tumor micro-vasculature, and the spatial distribution of viable tumor cells, although the techniques have the potential for much wider application. The principle attractiveness of optical-CT and optical-ECT are that high resolution (<20 microm) and high contrast co-registered 3D images of structure and function can be acquired for relatively large intact samples. The unique combination of high contrast and resolution offers advantages over micro-CT and micro-MRI, and the lack of requirement for sectioning offers advantages over confocal microscopy, conventional microscopy, and histological sectioning techniques. Optical-CT/ECT are implemented using in-house custom apparatus and a commercial dissecting microscope capable of both transmission and fluorescence imaging. Basic studies to characterize imaging performance are presented. Negligible geometrical distortion and accurate reconstruction of relative attenuation coefficients was observed. Optical-CT and optical-ECT are investigated here by application to high resolution imaging of HCT116 xenograft tumors, about 1 cc in dimension, which were transfected with constitutive red fluorescent protein (RFP). Tumor microvasculature was stained in vivo by tail vein injection of either passive absorbing dyes or active fluorescent markers (FITC conjugated lectin). Prior to imaging, the tumors were removed (ex vivo) and optically cleared in a key process to make the samples amenable to light transmission. The cleared tumors were imaged in three modes (i) optical-CT to image the 3D distribution of microvasculature as indicated by absorbing dye, (ii) optical-ECT using the FITC excitation and emission filter set, to determine microvasculature as indicated by lectin-endothelial binding, and (iii) optical-ECT using the DSRed2 filter set to determine the 3D distribution of viable tumor as indicated by RFP emission. A clear correlation was observed between the independent vasculature imaging modes (i) and (ii) and postimaging histological sections, providing substantial validation of the optical-CT and optical-ECT techniques. Strong correlation was also observed between the RFP imaging of mode iii, and modes i and ii, supporting the intuitive conclusion that well-perfused regions contain significant viable tumor. In summary, optical-CT and optical-ECT, when combined with new optical clearing techniques, represent powerful new imaging modalities with potential for providing unique information on the structure and function of tumors.

Animals↗
PubMed2005

Comparison of serum FSH and Inhibin B levels between adult male dizygotic and monozygotic twins.

BACKGROUND: FSH hypersecretion occurs in mothers of dizygotic (DZ) twins. Twinning is inherited via both sexes and transmitted through the female. FSH hypersecretion may thus occur in male DZ twins. METHODS: We assayed FSH and its counter-regulatory hormone, Inhibin B, in 108 adult male DZ and 100 monozygotic (MZ) twins (as controls) and compared our results to published norms. RESULTS: Inhibin B was elevated and higher in DZ compared with MZ twins with similar FSH. CONCLUSION: The normal FSH: Inhibin B endocrine feedback axis is different in adult male DZ twins. This contributes to the theory that the answer to human DZ twinning lies in the actions of FSH and Inhibin, and in their mutual interaction.

Adult↗
PubMed2005

Using reconfigurable hardware to accelerate multiple sequence alignment with ClustalW.

Aligning hundreds of sequences using progressive alignment tools such as ClustalW requires several hours on state-of-the-art workstations. We present a new approach to compute multiple sequence alignments in far shorter time using reconfigurable hardware. This results in an implementation of ClustalW with significant runtime savings on a standard off-the-shelf FPGA.

Computers↗
PubMed2005

Overexpression of genes on 16q associated with cisplatin resistance of testicular germ cell tumor cell lines.

Testicular germ-cell tumors (TGCTs) show exquisite sensitivity to cisplatin-based chemotherapy, and therefore this is considered a good model system for studying the mechanism of chemotherapy resistance. Although the genetic alterations related to TGCT have been well studied, little is known about the genetic basis of chemotherapy resistance, which occurs in a small proportion of TGCTs. In this study, we investigated genomic and expression differences between three cisplatin-sensitive and their paired cisplatin-resistant lines using combined whole-genome screen approaches. Comparative genomic hybridization (CGH) analysis on chromosomes revealed genetic differences between the resistant and parent cell lines in each pair, but did not show any consistent chromosome changes in all three lines. Microarray CGH analysis generated some additional information of DNA copy number gains and losses including some important oncogenes, tumor-suppressor genes, and drug-resistance-related genes. However, no consistent genomic region changes were found in the three cell lines. Interestingly, when comparative expressed sequence hybridization, a technique for gene expression profiling along chromosomes, was applied, we discovered a consistently overexpressed chromosomal region in all three resistant lines compared with their parent lines. The minimum overlapping chromosomal region is at 16q22-23. Further definition of genes in this chromosomal region will aid our understanding of the mechanism of cisplatin resistance and may offer novel therapeutic targets.

Antineoplastic Agents↗
PubMed2005

A combination of molecular cytogenetic analyses reveals complex genetic alterations in conventional renal cell carcinoma.

Here we report the complex pattern of genomic imbalances and rearrangements in a panel of 19 renal cell carcinoma cell lines detected with molecular cytogenetic analysis. Consistent heterogeneity in chromosome number was found, and most cell lines showed a near-triploid chromosome complement. Several cell lines showed deletions of the TP53 (alias p53), CDKN2A (alias p16), and VHL genes. Multiplex fluorescence in situ hybridization (M-FISH) analysis revealed chromosome 3 translocated to several other partners chromosomes, as well as breakage events commonly affecting chromosomes 1, 5, 8, 10, and 17. The most common abnormality detected with comparative genomic hybridization (CGH) was deletions of chromosome 3p, with loss of the RASSF1, FHIT, and p44S10 loci frequently involved. CGH gain of 5q showed overrepresentation of the EGR1 and CSF1R genes. Recurrent alterations to chromosome 7 included rearrangement of 7q11 and gains of the EGFR, TIF1, and RFC2 genes. Several lines exhibited rearrangement of 12q11 approximately q14 and overrepresentation of CDK4 and SAS loci. M-FISH revealed several other recurrent translocations, and CGH findings included loss of 9p, 14q, and 18q and gain of 8q, 12, and 20. Further genomic microarray changes included loss of MTAP, IGH@, HTR1B, and SMAD4 (previously MADH4) and gains of MYC and TOP1. An excellent correlation was observed between the genomic array and FISH data, demonstrating that this technique is effective and accurate. The aberrations detected here may reflect important pathways in renal cancer pathogenesis.

Carcinoma, Renal Cell↗
PubMed2005

The changing presentation of germ cell tumours of the testis between 1983 and 2002.

OBJECTIVE: To prospectively investigate the presentation of germ cell tumours (GCTs) of the testis in terms of stage or histology, as the incidence of this disease in increasing. PATIENTS AND METHODS: Patients diagnosed with GCT of the testis between 1983 and 2002 were categorised into three periods depending on the date of diagnosis of the GCT, and the presentational characteristics assessed. RESULTS There was a significant increase in the proportion of patients presenting with stage I disease (59% to 78%) and seminoma (43% to 58%) over this period. There was also a significant reduction in the size of the primary tumour (5 to 4 cm). CONCLUSION: A greater proportion of patients with GCT are presenting with stage I seminoma, the reasons for which are unclear, although earlier diagnosis through improved awareness of GCT may be important.

Adolescent↗
PubMed2004

Cannabis-induced cytotoxicity in leukemic cell lines: the role of the cannabinoid receptors and the MAPK pathway.

Delta9-Tetrahydrocannabinol (THC) is the active metabolite of cannabis. THC causes cell death in vitro through the activation of complex signal transduction pathways. However, the role that the cannabinoid 1 and 2 receptors (CB1-R and CB2-R) play in this process is less clear. We therefore investigated the role of the CB-Rs in mediating apoptosis in 3 leukemic cell lines and performed microarray and immunoblot analyses to establish further the mechanism of cell death. We developed a novel flow cytometric technique of measuring the expression of functional receptors and used combinations of selective CB1-R and CB2-R antagonists and agonists to determine their individual roles in this process. We have shown that THC is a potent inducer of apoptosis, even at 1 x IC(50) (inhibitory concentration 50%) concentrations and as early as 6 hours after exposure to the drug. These effects were seen in leukemic cell lines (CEM, HEL-92, and HL60) as well as in peripheral blood mononuclear cells. Additionally, THC did not appear to act synergistically with cytotoxic agents such as cisplatin. One of the most intriguing findings was that THC-induced cell death was preceded by significant changes in the expression of genes involved in the mitogen-activated protein kinase (MAPK) signal transduction pathways. Both apoptosis and gene expression changes were altered independent of p53 and the CB-Rs.

Cannabinoids↗
PubMed2004

Effect of haemopoietic growth factors on cancer cell lines and their role in chemosensitivity.

The recombinant growth factors (GFs) erythropoietin (Epo) and granulocyte-macrophage colony stimulating factor (GM-CSF) have important roles in the management of cancer patients. However, the effects of these GFs at a cellular level are not well understood. We examined the effect of GFs alone, and in combination with cytotoxic chemotherapy, in a panel of seven cell lines. Flow cytometric analysis showed varying levels of receptor expression, which correlated with phosphorylated MAPK expression. Additionally, there were also concomitant increases in BCL-2 protein levels in those cells with high levels of MAPK activation. Although culturing cells with Epo or GM-CSF did not alter cell viability by themselves, GF pretreatment in cell lines expressing higher receptor levels resulted in a reduced magnitude of cell kill following exposure to cytotoxic IC50 concentrations of cisplatin. Subsequent co-culture with either the MEK inhibitor U0126 or the GM-CSF antagonist E21R negated this induced resistance to cytotoxic chemotherapy, confirming the importance of the GF receptor as well as MAPK in mediating these effects. These results suggest that the use of GFs during chemotherapy may be detrimental in those cancers expressing higher levels of the specific receptor. Conversely, our results also suggest that GFs are safe to use in chemotherapeutic regimens if the cancer cells do not overexpress the particular receptor.

Antineoplastic Agents↗
PubMed2002

Prognostic factors for relapse in stage I seminoma managed by surveillance: a pooled analysis.

PURPOSE: Several management options are available to patients with stage I seminoma, including adjuvant radiotherapy, surveillance, and adjuvant chemotherapy. We performed a pooled analysis of patients from the four largest surveillance studies to better delineate prognostic factors associated with disease progression. PATIENTS AND METHODS: Individual patient data were obtained from each center (Princess Margaret Hospital, Danish Testicular Cancer Study Group, Royal Marsden Hospital, and Royal London Hospital) for 638 patients. Tumor characteristics (size, histologic subtype, invasion of rete testis, and tumor invasion into small vessels [SVI]) as well as age at diagnosis were analyzed for prognostic importance for relapse. RESULTS: With a median follow-up of 7.0 years (range, 0.02 to 17.5 years), 121 relapses were observed for an actuarial 5-year relapse-free rate (RFR) of 82.3%. On univariate analysis, tumor size (RFR: 4 cm, 76%; P =.003), rete testis invasion (RFR: 86% [absent] v 77% [present], P =.003), and the presence of SVI (RFR: 86% [absent] v 77% [present], P =.038) were predictive of relapse. On multivariate analysis, tumor size ( 4 cm, hazard ratio 2.0; 95% confidence interval [CI], 1.3 to 3.2) and invasion of the rete testis (hazard ratio 1.7; 95% CI, 1.1 to 2.6) remained as important predictors for relapse. CONCLUSION: We have identified size of primary tumor and rete testis invasion as important prognostic factors for relapse in patients with stage I seminoma managed with surveillance. This information will allow patients and clinicians to choose management based on a more accurate assessment of an individual patient's risk of relapse. In addition, it will allow clinicians to tailor follow-up protocols based on risk of occult disease.

Adult↗