• Expression of the collagen-related heat shock protein HSP47 in fibroblasts treated with hyperthermia or photodynamic therapy.

      Verrico, A K; Moore, James V; Department of Experimental Radiation Oncology, Paterson Institute for Cancer Research, Christie Hospital (NHS) Trust, Manchester, UK. (1997)
      Heat shock protein (HSP) 47 is associated with collagen type I metabolism, both constitutively and after stress-inflicted injury. It has been claimed that, in contrast to hyperthermia (HT), photodynamic therapy (PDT) does not damage collagen, as measured at the level of tissue. We have studied HSP47 expression in normal murine skin fibroblasts (3T6) treated with hyperthermia or photodynamic therapy (PDT) mediated by three different photosensitizers: (1) haematoporphyrin ester (HpE), (2) meta tetra hydroxyphenyl chlorin (mTHPC) and (3) riboflavin (RB). Riboflavin is not an established photosensitizer for PDT and was chosen here because it is known to provoke collagen damage. The applied doses of the treatments were isoeffective in terms of 3T6 clonogenic cell survival. Analysis, at both transcriptional and translational levels, revealed HSP47 elevation after hyperthermia and after PDT with RB. PDT sensitized by HpE and mTHPC did not significantly alter HSP47 expression. These observations are consistent with our hypothesis that this collagen chaperone is up-regulated by laser-mediated modalities known to damage collagen (i.e. HT and RB PDT) but not by more conventional PDT treatments. Additionally, unexpected significant up-regulation of HSP47 was detected after illumination alone (no photosensitizer) of 3T6 cells at 653 nm laser light, but not at 630 nm.
    • Expression of the E.coli 3-methyladenine DNA glycosylase I gene in mammalian cells reduces the toxic and mutagenic effects of methylating agents.

      Klungland, A; Fairbairn, Leslie J; Watson, Amanda J; Margison, Geoffrey P; Seeberg, E; Biotechnology Centre of Oslo, Blindern, Norway. (1992-12)
      In order to investigate the importance of 3-methyladenine in cellular sensitivity to chemical methylating agents we have constructed retroviral vectors for the integration and expression of the Escherichia coli tag gene in mammalian cells. The tag gene encodes 3-methyladenine DNA glycosylase-1 which specifically removes 3-alkyladenines from DNA. The constructs were introduced into Chinese hamster V79 cells by liposome mediated transfection or into murine haemopoietic stem cells by cocultivation with a lipofected, virus-packaging cell line. In both cases, stable transfectants were selected for resistance to the antibiotic, G418, conferred by expression of the neo gene carried by the vector. Measurements of 3-methyladenine DNA glycosylase activity in cell extracts showed an up to 10-fold increase in cell lines with stably integrated tag gene sequences. These cell lines were significantly more resistant to the cytotoxic effects of methylmethanesulfonate and N-methyl-N-nitrosourea than their parent cell lines, indicating that 3-methyladenine repair is a limiting factor in cellular resistance to these methylating agents. Furthermore, the mutation frequency induced by methylmethanesulfonate was reduced to 50% of normal by expression of 3-methyladenine I activity in the Chinese hamster cells, indicating that m3A is not only a cytotoxic but also a premutagenic lesion in mammalian cells. It is concluded that an alkylation repair gene function of a type only thought to be present in bacteria can yield a hyperresistant phenotype when transferred to mammalian cells.
    • Expression of the E.coli ada gene in S.cerevisiae provides cellular resistance to N-methyl-N'-nitro-N-nitrosoguanidine in rad6 but not in rad52 mutants.

      Brozmanová, J; Vlcková, V; Chovanec, M; Cernáková, L; Skorvaga, M; Margison, Geoffrey P; Department of Molecular Genetics, Cancer Research Institute, Slovak Academy of Sciences, Bratislava. (1994-12-25)
      The Escherichia coli ada gene protein coding region under the control of the yeast alcohol dehydrogenase promoter in the extrachromosomally replicating yeast expression vectors pADHO6C and pVT103LO6C was introduced into the wild-type yeast strains, YNN-27 and FF-18733, and the repair deficient mutants LN-1 (rad1-1), VV-5 (rad6-1), C5-6 (rad52-1) and FF-18742 (rad52::URA3). This resulted in the expression of 3950, 1900, 1870, 1620, 1320 and 1420 fmol ada-encoded ATase/mg protein respectively: transformation with the parent vectors resulted in ATase activities of 3-17 fmol/mg protein. The wild-types, rad1-1 and rad6-1 yeast expressing the bacterial ATase showed increased resistance to the toxic and mutagenic effects of N-methyl-N'-nitro-N- nitrosoguanidine (MNNG). Expression of ATase in the rad52-1 and rad52::URA3 mutants neither complemented their sensitivity, nor reduced the mutagenic effects of this agent. These results suggest that whilst a portion of the toxic and mutagenic lesions induced by MNNG can be repaired in yeast by the E.coli Ada protein in a RAD1- and RAD6-independent manner, the RAD52 gene product may be essential for the complete functioning of the Ada ATase. This is the first suggestion of a possible cofactor requirement for ATase.
    • Expression of the E.coli ada gene in yeast protects against the toxic and mutagenic effects of N-methyl-N′-nitro-N-nitrosoguanidine

      Brozmanova, J; Kleibl, K; Vlckova, V; Skorvaga, Milan; Cernakova, L; Margison, Geoffrey P; Cancer Research Institute, Slovak Academy of Sciences, 812 32 Bratislavaa (1990)
    • Expression of the Epstein-Barr virus latent membrane protein in nasopharyngeal carcinoma biopsy specimens.

      Stewart, James P; Arrand, John R; Department of Molecular Biology, Paterson Institute for Cancer Research, Christie CRC Cancer Centre, Manchester, UK. (1993-03)
      It has been known for some time that the Epstein-Barr virus (EBV) is associated with nasopharyngeal carcinoma (NPC). The tumor cells are known to harbor EBV in a latent state. Latently-infected B cells that have become growth transformed by EBV in vitro express some 10 antigens, two of which (Epstein-Barr nuclear antigen 2 [EBNA2] and the latent membrane protein [LMP]) are associated with cellular transformation. We evaluated the expression of these two EBV antigens in NPC by probing tissue sections with monoclonal antibodies. We found that EBNA2 was not expressed and that LMP was expressed in seven of nine biopsy specimens. It is therefore postulated that either there are subsets of NPC or that LMP may be involved only in certain stages of tumor formation.
    • Expression of the GM-CSF gene after retroviral transfer in hematopoietic stem cell lines induces synchronous granulocyte-macrophage differentiation.

      Just, U; Stocking, C; Spooncer, Elaine; Dexter, T Michael; Ostertag, W; Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Universität Hamburg, Federal Republic of Germany. (1991-03-22)
      Multipotent murine stem cell lines (FDC-Pmix) depend on IL-3 for self-renewal and proliferation and can be induced to differentiate into multiple hematopoietic lineages. Single FDC-Pmix cells infected with retroviral vectors expressing GM-CSF are induced to differentiate into granulocytes and macrophages. This results in a complete loss of clonogenic cells if IL-3 is not exogenously supplied; however, multipotent variants can be selected that do not terminally differentiate if cells are kept in the presence of IL-3. Unidirectional and synchronous granulocyte and macrophage differentiation accompanied with loss of self-renewal capacity is induced when IL-3 is removed. Our data indicate that activation of the GM-CSF receptor induces differentiation of stem cells by an instructive mechanism that can be blocked by the activated IL-3 receptor. A model of how receptors can induce proliferation and cell-specific differentiation by two separate pathways is discussed.
    • Expression of the leukemia oncogene Lmo2 is controlled by an array of tissue-specific elements dispersed over 100 kb and bound by Tal1/Lmo2, Ets, and Gata factors.

      Landry, Josette-Renee; Bonadies, Nicolas; Kinston, Sarah; Knezevic, Kathy; Wilson, Nicola K; Oram, S Helen; Janes, Mary E; Piltz, Sandie; Hammett, Michelle; Carter, Jacinta; et al. (2009-06-04)
      The Lmo2 gene encodes a transcriptional cofactor critical for the development of hematopoietic stem cells. Ectopic LMO2 expression causes leukemia in T-cell acute lymphoblastic leukemia (T-ALL) patients and severe combined immunodeficiency patients undergoing retroviral gene therapy. Tightly controlled Lmo2 expression is therefore essential, yet no comprehensive analysis of Lmo2 regulation has been published so far. By comparative genomics, we identified 17 highly conserved noncoding elements, 9 of which revealed specific acetylation marks in chromatin-immunoprecipitation and microarray (ChIP-chip) assays performed across 250 kb of the Lmo2 locus in 11 cell types covering different stages of hematopoietic differentiation. All candidate regulatory regions were tested in transgenic mice. An extended LMO2 proximal promoter fragment displayed strong endothelial activity, while the distal promoter showed weak forebrain activity. Eight of the 15 distal candidate elements functioned as enhancers, which together recapitulated the full expression pattern of Lmo2, directing expression to endothelium, hematopoietic cells, tail, and forebrain. Interestingly, distinct combinations of specific distal regulatory elements were required to extend endothelial activity of the LMO2 promoter to yolk sac or fetal liver hematopoietic cells. Finally, Sfpi1/Pu.1, Fli1, Gata2, Tal1/Scl, and Lmo2 were shown to bind to and transactivate Lmo2 hematopoietic enhancers, thus identifying key upstream regulators and positioning Lmo2 within hematopoietic regulatory networks.
    • Expression of the MOZ-TIF2 oncoprotein in mice represses senescence.

      Largeot, Anne; Perez-Campo, Flor-Maria; Marinopoulou, Elli; Lie-A-Ling, Michael; Kouskoff, Valerie; Lacaud, Georges; Cancer Research UK Stem Cell Biology Group, CR-UK Manchester Institute, The University of Manchester, Wilmslow road, Manchester (2016-02-05)
      The MOZ-TIF2 translocation, which fuses monocytic leukemia zinc finger protein (MOZ) histone acetyltransferase (HAT) with the nuclear co-activator TIF2, is associated the development of acute myeloid leukemia. We recently found that in the absence of MOZ HAT activity, p16(INK4a) transcriptional levels are significantly increased, triggering an early entrance into replicative senescence. Because oncogenic fusion proteins must bypass cellular safeguard mechanisms, such as senescence and apoptosis, to induce leukemia, we hypothesized that this repressive activity of MOZ over p16(INK4a) transcription could be preserved, or even reinforced, in MOZ leukemogenic fusion proteins, such as MOZ-TIF2. We describe here that, indeed, MOZ-TIF2 silences expression of the CDKN2A locus (p16(INK4a) and p19(ARF)), inhibits the triggering of senescence, and enhances proliferation, providing conditions favorable to the development of leukemia. Furthermore, we describe that abolishing the MOZ HAT activity of the fusion protein leads to a significant increase in expression of the CDKN2A locus and the number of hematopoietic progenitors undergoing senescence. Finally, we report that inhibition of senescence by MOZ-TIF2 is associated with increased apoptosis, suggesting a role for the fusion protein in p53 apoptosis-versus-senescence balance. Our results underscore the importance of the HAT activity of MOZ, preserved in the fusion protein, for repression of CDKN2A locus transcription and the subsequent block of senescence, a necessary step for the survival of leukemic cells.
    • Expression of the ogt gene in wild-type and ada mutants of E. coli.

      Potter, P M; Kleibl, K; Cawkwell, L; Margison, Geoffrey P; Department of Carcinogenesis, Paterson Institute for Cancer Research, Christie Hospital and Holt Radium Institute, Manchester, UK. (1989-10-25)
      O6-alkylguanine (O6-AlkG) DNA alkyltransferase (ATase) and alkylphosphotriester (AlkP) ATase activity have been quantitated individually in extracts of various E. coli strains by means of ATase specific DNA substrates. O6-AlkG ATase activity was higher than AlkP ATase activity in the wild-type strains F26, AB1157 and SB229 and in the ada- mutants PJ1, PJ3, PJ5 and PJ6 indicating a 5-70 times higher level of expression of the ogt gene than the ada gene. The ada- mutant strains BS23, BS73 and GW5352 expressed O6-AlkG ATase but not AlkP ATase activity indicating expression only of the ogt gene. Southern analysis of DNA from F26, BS23, BS73, PJ1 and GW5352 showed a consistent pattern of hybridisation to an ogt probe but not to an ada probe. Exposure of E. coli to adaptive doses of N-methyl-N-nitro-N-nitroso-guanidine (MeNNG) caused an increase in AlkP ATase activity in F26, AB1156, SB229, PJ1, PJ3, PJ5 and PJ6. O6-AlkG ATase activity also increased in F26, AB1157 and SB229 but decreased to almost undetectable levels in all other strains examined except PJ3 where it remained constant. MeNNG increased ada mRNA abundance in F26 but no ada mRNA was detected in BS23, BS73 or GW5352: there was no evidence for increased ogt mRNA in any of the strains examined. In a limited survey, other bacterial strains have been shown to possess an ogt-like ATase activity.
    • Expression of the vascular endothelial growth factor receptor, KDR, in human placenta.

      Vuckovic, M; Ponting, J; Terman, B I; Niketic, V; Seif, M W; Kumar, Shant; Institute of Endocrinology, Immunology and Nutrition, Faculty of Science, University of Belgrade, Yugoslavia. (1996-04)
      Vascular endothelial growth factor (VEGF) is a heparin-binding growth factor known to act directly on vascular endothelial cells by promoting cell proliferation and permeability. To date, 3 structurally related cell surface receptors for VEGF, Flt-1, Flt-4 and KDR, have been identified and shown to be human type III receptor tyrosine kinases. The establishment of a vascular network is crucial to the development of the placenta and occurs through both angiogenesis and vasculogenesis. The signals controlling these processes are unclear. Immunohistochemical and in situ hybridisation techniques have localised VEGF in the trophoblast layers and VEGF binding to placental vascular endothelial cells and haemangioblasts has been shown, suggesting a role for VEGF and its receptors in development of the vascular network. In this study we have used specific antibodies to localise KDR and endothelial cells in 1st and 3rd trimester human placenta. The staining showed a colocalisation of KDR with endothelial cells and haemangioblasts. No staining of trophoblast cells was observed, but strong staining of the endothelial cells was seen in the villous stroma adjacent to areas of trophoblast proliferation.
    • Expression patterns of the human papillomavirus type 16 transcription factor E2 in low- and high-grade cervical intraepithelial neoplasia.

      Maitland, N J; Conway, S; Wilkinson, N S; Ramsdale, J; Morris, J R; Sanders, C M; Burns, J E; Stern, Peter L; Wells, M; Department of Biology, University of York, U.K. njm9@york.ac.uk (1998-11)
      Specific antibodies against the C-terminus of E2, produced by affinity purification of polyclonal antisera, have been used to identify the cellular populations which express the HPV 16 E2 transcription factor, in a series of formalin-fixed, paraffin-embedded cervical tissues. Cases were selected for both the presence of HPV 16 DNA (confirmed by multiple gene-specific PCR detections) and the presence of multiple grades of cervical intraepithelial neoplasia (CIN). The data indicate that E2 expression is highest in CIN I and in koilocytic lesions. Lower expression was observed in CIN II and little in CIN III lesions. In contrast, there was some restoration of E2 expression in invasive carcinomas, although the intracellular distribution was much more diffuse. The location of E2 expression to the superficial layers of the cervical epithelium, as well as the occurrence of some basal expression in CIN I, suggests that antibodies against HPV 16 E2 could be a useful adjunct to standard histological techniques for the detection of 'at-risk' patients as part of a cervical screening programme.
    • The extended family of proteoglycans: social residents of the pericellular zone.

      Gallagher, John T; CRC Department of Medical Oncology, Christie Hospital and Holt Radium Institute, Manchester, UK. (1989-12)
    • An extended Li-Fraumeni kindred with gastric carcinoma and a codon 175 mutation in TP53.

      Varley, Jennifer; McGown, Gail; Thorncroft, Mary R; Tricker, Karen J; Teare, M Dawn; Santibanez-Koref, Mauro F; Martin, J; Birch, Jillian M; Evans, D Gareth R; CRC Department of Cancer Genetics, Paterson Institute for Cancer Research, Manchester, UK. (1995-12)
      We present an extended family with Li-Fraumeni syndrome characterised by gastric and breast carcinoma, glioma, sarcoma, and leukaemia. This family showed strong evidence of linkage to TP53, and three of four tumours analysed showed loss of the wild type allele. A codon 175 missense mutation was identified in exon 5 in all available affected subjects. Counselling, screening, and issues surrounding presymptomatic testing are discussed.
    • Extended Middle East and North Africa: summary recommendations for the prevention of human papillomavirus infections and related cancers including cervical cancer.

      Seoud, M; Vaccarella, S; El-Kak, F; Sancho-Garnier, H; Jumaan, A; Kim, J; Garland, S; Stern, Peter L; LaMontagne, D; Albero, G; et al. (2013-12-30)
    • An extended set of PRDM1/BLIMP1 target genes links binding motif type to dynamic repression.

      Doody, Gina M; Care, Matthew A; Burgoyne, Nicholas J; Bradford, James R; Bota, Maria; Bonifer, Constanze; Westhead, David R; Tooze, Reuben M; Section of Experimental Haematology, Leeds Institute of Molecular Medicine, University of Leeds, Leeds LS9 7TF (2010-04-26)
      The transcriptional repressor B lymphocyte-induced maturation protein-1 (BLIMP1) regulates gene expression and cell fate. The DNA motif bound by BLIMP1 in vitro overlaps with that of interferon regulatory factors (IRFs), which respond to inflammatory/immune signals. At such sites, BLIMP1 and IRFs can antagonistically regulate promoter activity. In vitro motif selection predicts that only a subset of BLIMP1 or IRF sites is subject to antagonistic regulation, but the extent to which antagonism occurs is unknown, since an unbiased assessment of BLIMP1 occupancy in vivo is lacking. To address this, we identified an extended set of promoters occupied by BLIMP1. Motif discovery and enrichment analysis demonstrate that multiple motif variants are required to capture BLIMP1 binding specificity. These are differentially associated with CpG content, leading to the observation that BLIMP1 DNA-binding is methylation sensitive. In occupied promoters, only a subset of BLIMP1 motifs overlap with IRF motifs. Conversely, a distinct subset of IRF motifs is not enriched amongst occupied promoters. Genes linked to occupied promoters containing overlapping BLIMP1/IRF motifs (e.g. AIM2, SP110, BTN3A3) are shown to constitute a dynamic target set which is preferentially activated by BLIMP1 knock-down. These data confirm and extend the competitive model of BLIMP1 and IRF interaction.
    • Extensive amplification of single cells from CD34+ subpopulations in umbilical cord blood and identification of long-term culture-initiating cells present in two subsets.

      De Wynter, Erika A; Nadali, Gianpaolo; Coutinho, Lucia H; Testa, Nydia G; CRC Department of Experimental Haematology, Paterson Institute for Cancer Research, Withington, Manchester, United Kingdom. (1996-09)
      CD34+ cord blood cells were isolated with immunomagnetic beads and fractionated by fluorescence-activated cell sorting (FACS) into three subpopulations: CD34+38+DR+, CD34+38-DR+ and CD34+38-DR-, using antibodies specific for these cell surface markers. Cells from each of the three subsets were plated as single cells in serum-free medium supplemented with a combination of growth factor and individual cells were monitored for proliferation and the capacity to form colony-forming cells. Single cells from the CD34+38+DR+ subset showed the lowest expansion capacity, generating up to 1.1 x 10(6) cells at five weeks, while individual cells from both the CD34+38-DR+ and CD34+38-DR- subsets could be expanded up to 1.8 x 10(6) and 9.2 x 10(6) cells, respectively, over a period of six weeks. The different subpopulations also generated colony-forming cells which gave rise to erythroid, myeloid and erythroid/myeloid colonies. CD34+38-DR+ cells generated large numbers of colonies within two weeks in liquid culture, but this rapidly declined. Generation of lineage-committed colony-forming cells was better sustained in the CD34+38-DR- population and continued for up to six weeks in culture. Overall, the generation of colony-forming cells declined with time in culture, although the cell numbers continued to expand. However, when the same populations were plated on irradiated bone marrow stroma, both the CD34+38-DR+ and the CD34+38-DR- cells were capable of producing granulocytemacrophage colony-forming cells (GM-CFCs) for 10 to 12 weeks. As hemopoiesis was sustained for almost three months, it appears that these populations were significantly enriched in long-term culture-initiating cells (LTC-ICs). Although both populations generated GM-CFCs, the CD34+38-DR- cells sustained production of higher numbers of colony-forming cells than the CD34+38-DR+ population. These results demonstrate that cells from cord blood can be efficiently monitored at the single-cell level for proliferation, expansion and colony-forming capacity. Furthermore, at least two populations of LTC-ICs can be distinguished in cord blood CD34+38- cells by the differential expression of the HLA-DR antigen.
    • External quality assurance of circulating tumor cell enumeration using the CellSearch(®) system: a feasibility study.

      Kraan, J; Sleijfer, S; Strijbos, M; Ignatiadis, M; Peeters, D; Pierga, J; Farace, F; Riethdorf, S; Fehm, T; Zorzino, L; et al. (2011-03)
      Circulating tumor cells (CTCs) are cells that have detached from solid tumors and entered the blood. CTCs can be detected, among others, by semi-automated immunomagnetic enrichment and image cytometry using CellSearch® (Veridex, Raritan, NJ). We studied the feasibility of external quality assurance (EQA) of the entire CellSearch procedure from blood draw to interpretation of results in multiple laboratories.
    • External validation of survival of lung cancer patients due to setup uncertainties towards the heart

      Brink, C.; Bernchou, U.; Bertelsen, A.; Hansen, O.; Schytte, T.; Holloway, L.; Van Herk, Marcel; Johnson-Hart, Corinne; Price, Gareth J; Aznar, Marianne Camille; et al. (2020)
      Purpose or Objective The impact on survival due to heart toxicity for lung cancer patients treated with radiotherapy (RT) has been difficult to quantify, due to correlations between dose to heart and lung with tumor burden. A possible measure that indicates enhanced dose to heart but does not correlate with the other risk factors is the deviation between actual and planned daily distance between isocenter and heart. The average of this daily distance (DeltaD), which can be obtained from CBCT scans, will for positive values indicate larger separation of target and heart and thus reduced heart dose during delivery. DeltaD has previously been reported to impact survival [Johnson-Hart et al IJROBP 2018]. The aim of the current study is to undertake an external validation of this finding in another institution Material and Methods All patients treated in the validation department from April 2010 to end 2015 with daily CBCT, planned dose of 60-66 Gy in 2 Gy fractions and for which a heart delineation was available were collected for analysis. Standard clinical IGRT procedure utilized two registrations for each CBCT 1) tumor region (mask) and 2) overall anatomy (clipbox). The first was used for patient positioning while the latter was used for overall validation of the anatomy. The latter is representative of the heart position, while the first represents the tumor position hence the treatment isocenter. The difference between the registrations can thus be used to estimate the daily shift of the heart relative to the isocenter. Based on clinical data (performance status, GTV volume, Age, T and N stage, histology, tumor stage and dose) a base Cox model predicting survival was created using Lasso for parameter selection. Impact of continuous variable DeltaD was tested by adding DeltaD to the base Cox model. All analyses were performed in R v. 3.6.1. Results 300 patients were included. DeltaD did not correlate statistically significant with any of the clinical factors. Range of DeltaD was -0.6 cm to 0.7 cm. Figure 1 shows Kaplan-Meier plots of patients with positive versus negative DeltaD. It is seen that a split of the curves occurs around 16 months after the start of RT. The base Cox model included performance status, ln(GTV volume) and Age. DeltaD was included in the base model using time dependent Cox regression for which DeltaD effectively was zero until 16 months after RT. This resulted in a statistically significant regression constant of DeltaD of - 1.63 per cm (HR=0.195) with p-value of 0.017 Conclusion As in the original study this validation study demonstrates significant impact on survival due to estimated setup errors in the direction of the heart, even with daily online IGRT corrections. This indicates that dose to heart impacts survival for these patients. However, in contrast to the original study the effect of DeltaD only starts 16 months after RT. This difference in the two studies might reflect differences in treatment or patient cohorts at the two centers, and calls for additional external validation.
    • Extracellular matrix degradation and remodeling in development and disease.

      Lu, Pengfei; Takai, K; Weaver, V; Werb, Z; Breakthrough Breast Cancer Research Unit, Paterson Institute for Cancer Research and Wellcome Trust Centre for Cell Matrix Research, University of Manchester, United Kingdom. (2011-12)
      The extracellular matrix (ECM) serves diverse functions and is a major component of the cellular microenvironment. The ECM is a highly dynamic structure, constantly undergoing a remodeling process where ECM components are deposited, degraded, or otherwise modified. ECM dynamics are indispensible during restructuring of tissue architecture. ECM remodeling is an important mechanism whereby cell differentiation can be regulated, including processes such as the establishment and maintenance of stem cell niches, branching morphogenesis, angiogenesis, bone remodeling, and wound repair. In contrast, abnormal ECM dynamics lead to deregulated cell proliferation and invasion, failure of cell death, and loss of cell differentiation, resulting in congenital defects and pathological processes including tissue fibrosis and cancer. Understanding the mechanisms of ECM remodeling and its regulation, therefore, is essential for developing new therapeutic interventions for diseases and novel strategies for tissue engineering and regenerative medicine.
    • The extracellular matrix of human amniotic epithelium: ultrastructure, composition and deposition.

      Aplin, J; Campbell, S; Allen, Terence D; University of Manchester, St Mary's Hospital, Manchester M13 0JH, UK. (1985-11)
      Ultrastructural comparisons have been made between human amnion extracellular matrix in tissue and cell culture. Immunochemical analysis of matrix deposited by monolayers of cultured amnion epithelial cells has also been undertaken. The basal cell surfaces are highly invaginated with an associated basal lamina that is more electron dense at the distal tips of basal cell processes where hemidesmosomes are frequent. Immediately below the lamina densa is a zone rich in collagen bundles. In the underlying stroma two types of fibril predominate, one striated of 50 nm diameter and one of 18 nm diameter. The observations suggest that at gestational term the epithelial cells are still active in the production of matrix. Secretion appears to occur into invaginations in the basal cell surface where a loosely organized mixture of stromal-type and basal laminal-type aggregates is formed. In culture on plastic, cells also deposit a mixture of basal laminal (type IV collagen + laminin) and stromal (collagens type I + III) components as well as fibronectin. However, segregation into a true basal lamina with underlying stroma does not occur in vitro, suggesting the need for an organized subcellular template to complete matrix morphogenesis. The in vitro and in vivo evidence suggest that the epithelium contributes to the subjacent dense collagenous zone as well as to the basal lamina.