Medicine, Dentistry & Health Sciences Collected Works - Research Publications
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ItemMucin 1 (MUC1) is a novel partner for MAL2 in breast carcinoma cells(BMC, 2009-01-28)BACKGROUND: The MAL2 gene, encoding a four-transmembrane protein of the MAL family, is amplified and overexpressed in breast and other cancers, yet the significance of this is unknown. MAL-like proteins have trafficking functions, but their molecular roles are largely obscure, partly due to a lack of known binding partners. METHODS: Yeast two-hybrid screening of a breast carcinoma cDNA expression library was performed using a full-length MAL2 bait, and subsequent deletion mapping experiments were performed. MAL2 interactions were confirmed by co-immunoprecipitation analyses and confocal microscopy was employed to compare protein sub-cellular distributions. Sucrose density gradient centrifugation of membranes extracted in cold Triton X-100 was employed to compare protein distributions between Triton X-100-soluble and -insoluble fractions. RESULTS: The tumor-associated protein mucin 1 (MUC1) was identified as a potential MAL2 partner, with MAL2/MUC1 interactions being confirmed in myc-tagged MAL2-expressing MCF-10A cells using co-immunoprecipitation assays. Deletion mapping experiments demonstrated a requirement for the first MAL2 transmembrane domain for MUC1 binding, whereas the MAL2 N-terminal domain was required to bind D52-like proteins. Confocal microscopy identified cytoplasmic co-localisation of MUC1 and MAL2 in breast cell lines, and centrifugation of cell lysates to equilibrium in sucrose density gradients demonstrated that MAL2 and MUC1 proteins were co-distributed between Triton X-100-soluble and -insoluble fractions. However co-immunoprecipitation analyses detected MAL2/MUC1 interactions in Triton X-100-soluble fractions only. Myc-MAL2 expression in MCF-10A cells was associated with both increased MUC1 detection within Triton X-100-soluble and -insoluble fractions, and increased MUC1 detection at the cell surface. CONCLUSION: These results identify MUC1 as a novel MAL2 partner, and suggest a role for MAL2 in regulating MUC1 expression and/or localisation.
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ItemNumerical and functional defects of blood dendritic cells in early- and late-stage breast cancer(NATURE PUBLISHING GROUP, 2007-10-30)The generation of antitumour immunity depends on the nature of dendritic cell (DC)-tumour interactions. These have been studied mostly by using in vitro-derived DC which may not reflect the natural biology of DC in vivo. In breast cancer, only one report has compared blood DC at different stages and no longitudinal evaluation has been performed. Here we conducted three cross-sectional and one one-year longitudinal assessments of blood DC in patients with early (stage I/II, n=137) and advanced (stage IV, n=36) disease compared to healthy controls (n=66). Patients with advanced disease exhibit markedly reduced blood DC counts at diagnosis. Patients with early disease show minimally reduced counts at diagnosis but a prolonged period (1 year) of marked DC suppression after tumour resection. While differing in frequency, DC from both patients with early and advanced disease exhibit reduced expression of CD86 and HLA-DR and decreased immunostimulatory capacities. Finally, by comparing a range of clinically available maturation stimuli, we demonstrate that conditioning with soluble CD40L induces the highest level of maturation and improved T-cell priming. We conclude that although circulating DC are compromised by loco-regional and systemic breast cancer, they respond vigorously to ex vivo conditioning, thus enhancing their immunostimulatory capacity and potential for immunotherapy.
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ItemSuppressor of cytokine signalling gene expression is elevated in breast carcinoma(NATURE PUBLISHING GROUP, 2003-08-04)Cytokines are important for breast cell function, both as trophic hormones and as mediators of host defense mechanisms against breast cancer. Recently, inducible feedback suppressors of cytokine signalling (SOCS/JAB/SSI) have been identified, which decrease cell sensitivity to cytokines. We examined the expression of SOCS genes in 17 breast carcinomas and 10 breast cancer lines, in comparison with normal tissue and breast lines. We report elevated expression of SOCS-1-3 and CIS immunoreactive proteins within in situ ductal carcinomas and infiltrating ductal carcinomas relative to normal breast tissue. Significantly increased expression of SOCS-1-3 and CIS transcripts was also shown by quantitative in situ hybridisation within both tumour tissue and reactive stroma. CIS transcript expression was elevated in all 10 cancer lines, but not in control lines. However, there was no consistent elevation of other SOCS transcripts. CIS protein was shown by immunoblot to be present in all cancer lines at increased levels, mainly as the 47 kDa ubiquitinylated form. A potential proliferative role for CIS overexpression is supported by reports that CIS activates ERK kinases, and by strong induction in transient reporter assays with an ERK-responsive promoter. The in vivo elevation of SOCS gene expression may be part of the host/tumour response or a response to autocrine/paracrine GH and prolactin. However, increased CIS expression in breast cancer lines appears to be a specific lesion, and could simultaneously shut down STAT 5 signalling by trophic hormones, confer resistance to host cytokines and increase proliferation through ERK kinases.
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ItemSpontaneous apoptosis of blood dendritic cells in patients with breast cancer(BMC, 2006)INTRODUCTION: Dendritic cells (DCs) are key antigen-presenting cells that play an essential role in initiating and directing cellular and humoral immunity, including anti-tumor responses. Due to their critical role in cancer, induction of DC apoptosis may be one of the central mechanisms used by tumors to evade immune recognition. METHODS: Spontaneous apoptosis of blood DCs (lineage negative HLA-DR positive cells) was assessed in peripheral blood mononuclear cells (PBMCs) using Annexin-V and TUNEL assays immediately after blood collection. The role of tumor products was assessed by culturing cells with supernatants derived from breast cancer cell lines (TDSN) or PBMCs (PBMC-SN, as a control). The capacity of DC stimulation to prevent apoptosis was assessed by incubating DC with inflammatory cytokines, poly I:C, IL-12 or CD40 ligand (CD40L) prior to culture with TDSN. Apoptosis was determined by flow cytometry and microscopy, and Bcl-2 expression determined by intracellular staining. RESULTS: In this study we document the presence of a significantly higher proportion of apoptotic (Annexin-V+ and TUNEL+) blood DCs in patients with early stage breast cancer (stage I to II; n = 13) compared to healthy volunteers (n = 15). We examined the role of tumor products in this phenomenon and show that supernatants derived from breast cancer lines induce apoptosis of blood DCs in PBMC cultures. Aiming to identify factors that protect blood DC from apoptosis, we compared a range of clinically available maturation stimuli, including inflammatory cytokines (tumor necrosis factor-alpha, IL-1beta, IL-6 and prostaglandin (PG)E2 as a cytokine cocktail), synthetic double-stranded RNA (poly I:C) and soluble CD40 ligand. Although inflammatory cytokines and poly I:C induced robust phenotypic maturation, they failed to protect blood DCs from apoptosis. In contrast, CD40 stimulation induced strong antigen uptake, secretion of IL-12 and protected blood DCs from apoptosis through sustained expression of Bcl-2. Exogenous IL-12 provided similar Bcl-2 mediated protection, suggesting that CD40L effect is mediated, at least in part, through IL-12 secretion. CONCLUSION: Cumulatively, our results demonstrate spontaneous apoptosis of blood DCs in patients with breast cancer and confirm that ex vivo conditioning of blood DCs can protect them from tumor-induced apoptosis.
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ItemAberrant mucin assembly in mice causes endoplasmic reticulum stress and spontaneous inflammation resembling ulcerative colitis(PUBLIC LIBRARY SCIENCE, 2008-03)BACKGROUND: MUC2 mucin produced by intestinal goblet cells is the major component of the intestinal mucus barrier. The inflammatory bowel disease ulcerative colitis is characterized by depleted goblet cells and a reduced mucus layer, but the aetiology remains obscure. In this study we used random mutagenesis to produce two murine models of inflammatory bowel disease, characterised the basis and nature of the inflammation in these mice, and compared the pathology with human ulcerative colitis. METHODS AND FINDINGS: By murine N-ethyl-N-nitrosourea mutagenesis we identified two distinct noncomplementing missense mutations in Muc2 causing an ulcerative colitis-like phenotype. 100% of mice of both strains developed mild spontaneous distal intestinal inflammation by 6 wk (histological colitis scores versus wild-type mice, p < 0.01) and chronic diarrhoea. Monitoring over 300 mice of each strain demonstrated that 25% and 40% of each strain, respectively, developed severe clinical signs of colitis by age 1 y. Mutant mice showed aberrant Muc2 biosynthesis, less stored mucin in goblet cells, a diminished mucus barrier, and increased susceptibility to colitis induced by a luminal toxin. Enhanced local production of IL-1beta, TNF-alpha, and IFN-gamma was seen in the distal colon, and intestinal permeability increased 2-fold. The number of leukocytes within mesenteric lymph nodes increased 5-fold and leukocytes cultured in vitro produced more Th1 and Th2 cytokines (IFN-gamma, TNF-alpha, and IL-13). This pathology was accompanied by accumulation of the Muc2 precursor and ultrastructural and biochemical evidence of endoplasmic reticulum (ER) stress in goblet cells, activation of the unfolded protein response, and altered intestinal expression of genes involved in ER stress, inflammation, apoptosis, and wound repair. Expression of mutated Muc2 oligomerisation domains in vitro demonstrated that aberrant Muc2 oligomerisation underlies the ER stress. In human ulcerative colitis we demonstrate similar accumulation of nonglycosylated MUC2 precursor in goblet cells together with ultrastructural and biochemical evidence of ER stress even in noninflamed intestinal tissue. Although our study demonstrates that mucin misfolding and ER stress initiate colitis in mice, it does not ascertain the genetic or environmental drivers of ER stress in human colitis. CONCLUSIONS: Characterisation of the mouse models we created and comparison with human disease suggest that ER stress-related mucin depletion could be a fundamental component of the pathogenesis of human colitis and that clinical studies combining genetics, ER stress-related pathology and relevant environmental epidemiology are warranted.
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ItemMucin Dynamics in Intestinal Bacterial Infection(PUBLIC LIBRARY SCIENCE, 2008-12-17)BACKGROUND: Bacterial gastroenteritis causes morbidity and mortality in humans worldwide. Murine Citrobacter rodentium infection is a model for gastroenteritis caused by the human pathogens enteropathogenic Escherichia coli and enterohaemorrhagic E. coli. Mucin glycoproteins are the main component of the first barrier that bacteria encounter in the intestinal tract. METHODOLOGY/PRINCIPAL FINDINGS: Using Immunohistochemistry, we investigated intestinal expression of mucins (Alcian blue/PAS, Muc1, Muc2, Muc4, Muc5AC, Muc13 and Muc3/17) in healthy and C. rodentium infected mice. The majority of the C. rodentium infected mice developed systemic infection and colitis in the mid and distal colon by day 12. C. rodentium bound to the major secreted mucin, Muc2, in vitro, and high numbers of bacteria were found in secreted MUC2 in infected animals in vivo, indicating that mucins may limit bacterial access to the epithelial surface. In the small intestine, caecum and proximal colon, the mucin expression was similar in infected and non-infected animals. In the distal colonic epithelium, all secreted and cell surface mucins decreased with the exception of the Muc1 cell surface mucin which increased after infection (p<0.05). Similarly, during human infection Salmonella St Paul, Campylobacter jejuni and Clostridium difficile induced MUC1 in the colon. CONCLUSION: Major changes in both the cell-surface and secreted mucins occur in response to intestinal infection.