L K Ashman

University of Newcastle, Newcastle, New South Wales, Australia

Are you L K Ashman?

Claim your profile

Publications (125)607.65 Total impact

  • No preview · Article · Oct 2014 · Cancer Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Tetraspanins are transmembrane proteins that serve as scaffolds for multiprotein complexes containing, for example, integrins, growth factor receptors and matrix metalloproteases, and modify their functions in cell adhesion, migration and transmembrane signaling. CD151 is part of the tetraspanin family and it forms tight complexes with β1 and β4 integrins, both of which have been shown to be required for tumorigenesis and/or metastasis in transgenic mouse models of breast cancer. High levels of the tetraspanin CD151 have been linked to poor patient outcome in several human cancers including breast cancer. In addition, CD151 has been implicated as a promoter of tumor angiogenesis and metastasis in various model systems. Methods Here we investigated the effect of Cd151 deletion on mammary tumorigenesis by crossing Cd151-deficient mice with a spontaneously metastasising transgenic model of breast cancer induced by the polyoma middle T antigen (PyMT) driven by the murine mammary tumor virus promoter (MMTV). Results Cd151 deletion did not affect the normal development and differentiation of the mammary gland. While there was a trend towards delayed tumor onset in Cd151−/− PyMT mice compared to Cd151+/+ PyMT littermate controls, this result was only approaching significance (Log-rank test P-value =0.0536). Interestingly, Cd151 deletion resulted in significantly reduced numbers and size of primary tumors but did not appear to affect the number or size of metastases in the MMTV/PyMT mice. Intriguingly, no differences in the expression of markers of cell proliferation, apoptosis and blood vessel density was observed in the primary tumors. Conclusion The findings from this study provide additional evidence that CD151 acts to enhance tumor formation initiated by a range of oncogenes and strongly support its relevance as a potential therapeutic target to delay breast cancer progression.
    Full-text · Article · Jul 2014 · BMC Cancer
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Prostate cancer is an extremely heterogeneous disease; patients that do progress to late stage metastatic prostate cancer have limited treatment options, mostly palliative. Molecules involved in the metastatic cascade may prove beneficial in stratifying patients to assign appropriate treatment modalities and may also prove to be therapeutic anti-metastatic targets. The tetraspanin group of molecules are integral membrane proteins that associate with motility related proteins such as integrins. Clinical studies have mostly shown that reduced expression levels of the tetraspanin CD9 are correlated with tumour progression in a range of cancers. Furthermore functional studies have shown CD9 to be involved in cell motility and adhesion and that it may influence metastasis. The effects of endogenous CD9 on prostate cancer initiation and progression were analysed by crossing a Cd9(-/-) (KO) murine model with a model of de-novo developing and spontaneously metastasising prostate cancer, namely the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model. This study demonstrates for the first time that ablation of Cd9 had no detectable effect on de novo primary tumour onset, but did significantly increase metastasis to the liver but not the lungs. © 2013 Wiley Periodicals, Inc.
    Full-text · Article · Oct 2013 · International Journal of Cancer

  • No preview · Article · Aug 2013 · Cancer Research
  • L K Ashman
    [Show abstract] [Hide abstract]
    ABSTRACT: Oncogene is one of the world’s leading cancer journals. It is published weekly and covers all aspects of the structure and function of Oncogenes.
    No preview · Article · Mar 2013 · Oncogene
  • Leonie K. Ashman · Margot Zöller
    [Show abstract] [Hide abstract]
    ABSTRACT: Tetraspanins play important roles in cancer, especially in metastasis. CD82 and CD9 are frequently down-regulated on progression of epithelial cancers in humans and this has been associated with poor prognosis. In contrast, high levels of CD151 and Tspan 8 are often observed on tumour progression and have also been linked to poor patient outcome. These observations are supported by a large body of evidence from studies in vitro and in animal models. Considerable insights into the mechanisms by which tetraspanins influence tumour behaviour are now emerging. These include effects on cell-matrix and cell-cell interactions which influence migration and invasion of surrounding tissues, as well as angiogenesis. Several tetraspanins influence the function of platelets which can promote metastasis. Tetraspanins are constitutive components of exosomes, which are most important in intercellular communication. This widens the range of tetraspanin activities in physiology and pathology and may well be particularly important during spread and settlement of metastasizing tumor cells. There is hope that the understanding of how tetraspanins contribute to tumour progression indicates novel approaches to therapy.
    No preview · Chapter · Jan 2013
  • Source
    Ben T Copeland · Matthew J Bowman · Leonie K Ashman
    [Show abstract] [Hide abstract]
    ABSTRACT: Tetraspanins are integral membrane proteins that associate with motility related molecules such as integrins. Experimental studies have indicated that they may be important regulators of tumour invasion and metastasis and high expression of the tetraspanin CD151 has been linked to poor prognosis in a number of cancers. Here we show for the first time that genetic ablation of CD151 inhibits spontaneous metastasis in a transgenic mouse model of de novo tumourigenesis. To evaluate the effects of CD151 on de-novo prostate cancer initiation and metastasis, a Cd151-/- (KO) murine model was crossed with the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model. Mice were analysed for initiation of prostate tumour by palpation and primary tumours were analysed by immunohistochemistry. Liver and lungs were examined for incidence and size of spontaneous metastatic lesions by histopathology. Knocking-out Cd151 had no significant effect on prostate cancer initiation, or on expression of markers of proliferation, apoptosis or angiogenesis in primary tumours. However, it did significantly decrease metastasis in a site-specific fashion, notably to the lungs but not liver. Thus CD151 acts principally as promoter of metastasis in this model. Prostate cancer is the second highest cause of cancer related deaths in men in most western countries, with the majority of deaths attributed to late stage metastatic disease. CD151 may prove to be a valuable prognostic marker for treatment stratification and is a possible anti-metastatic target.
    Full-text · Article · Nov 2012 · Molecular Cancer Research
  • Leonie Ashman · Renate Griffith

    No preview · Article · Sep 2011 · Clinical Biochemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Vilain RE, Dudding T, Braye SG, Groombridge C, Meldrum C, Spigelman AD, Ackland S, Ashman L, Scott RJ. Can a familial gastrointestinal tumour syndrome be allelic with Waardenburg syndrome? Familial gastrointestinal stromal tumours (GISTs) are rare but otherwise well-characterized tumour syndromes, most commonly occurring on a background of germline-activating mutations in the tyrosine kinase receptor c-KIT. The associated clinical spectrum reflects the constitutive activation of this gene product across a number of cell lines, generating gain-of-function phenotypes in interstitial cells of Cajal (GIST and dysphagia), mast cells (mastocytosis) and melanocytes (hyperpigmentation). We report a three-generation kindred harbouring a c-KIT germline-activating mutation resulting in multifocal GISTs, dysphagia and a complex melanocyte hyperpigmentation and hypopigmentation disorder, the latter with features typical of those observed in Waardenburg type 2 syndrome (WS2F). Sequencing of genes known to be causative for WS [microphthalmia transcription factor (MITF), Pax3, Sox10, SNAI2] failed to show any candidate mutations to explain this complex cutaneous depigmentation phenotype. Our case report conclusively expands the clinical spectrum of familial GISTs and shows a hitherto unrecognized link to WS. Possible mechanisms responsible for this novel cause of WS2F will be discussed.
    No preview · Article · Jun 2011 · Clinical Genetics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This study was designed to determine the role of CD151 in platelet thrombus formation in vivo and define the contribution of platelet vs. endothelial CD151 in regulating platelet thrombus formation in vivo. Using intravital microscopy and ferric chloride (FeCl(3)) injury of mesenteric arterioles, we found that thrombi formed in CD151(+/-) and CD151(-/-) mice were smaller and less stable, than those formed in CD151(+/+) mice, with a tendency for embolization. Similarly, in Folt's FeCl(3)-induced carotid injury model, both CD151(+/-) and CD151(-/-) mice showed more prolonged times to 95% vessel occlusion than CD151(+/+) mice. In addition, laser-induced injury of cremaster muscle arterioles showed that thrombi formed in CD151(+/-) and CD151(-/-) mice were smaller and less stable than those formed in CD151(+/+) mice. Following platelet depletion/reconstitution with ex vivo-labeled donor platelets, platelet-depleted CD151(+/+) mice that received reconstitution with CD151(-/-) platelets had smaller thrombi that were unstable and embolized. In contrast, platelet-depleted CD151(-/-) mice that received reconstitution with CD151(+/+) platelets had normal thrombi that were stable. These data provide evidence that platelet CD151 is required for regulating thrombus formation in vivo.
    Full-text · Article · Oct 2009 · Journal of Thrombosis and Haemostasis
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A major question in immunology is how DC can display limited amounts of individual peptide-MHC complexes and still induce cross-linking of T-cell receptors to initiate cellular responses. One suggested mechanism is that MHC exists at the cell surface in high avidity multimers, and tetraspanin proteins, known to laterally associate with both MHC classes I and II, promote MHC multimerisation. To validate this theory, we tested the ability of DC deficient in either one of two typical tetraspanin molecules: CD37 or CD151 to present peptide to Ag-specific T cells. Surprisingly, although they exhibited no developmental or maturation defects, DC lacking either CD37 or CD151 expression were hyper-stimulatory to T cells. We demonstrate that CD37 and CD151 control DC-mediated T-cell activation by two different mechanisms: CD151 regulates co-stimulation whereas CD37 regulates peptide/MHC presentation. The implications of these results on the model suggesting that tetraspanins promote MHC multimerisation are discussed.
    Full-text · Article · Jan 2009 · European Journal of Immunology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The tetraspanin CD151 forms a stoichiometric complex with integrin alpha3beta1 and regulates its endocytosis. We observed that down-regulation of CD151 in various epithelial cell lines changed glycosylation of alpha3beta1. In contrast, glycosylation of other transmembrane proteins, including those associated with CD151 (e.g. alpha6beta1, CD82, CD63, and emmprin/CD147) was not affected. The detailed analysis has shown that depletion of CD151 resulted in the reduction of Fucalpha1-2Gal and bisecting GlcNAc-beta(1-->4) linkage on N-glycans of the alpha3 integrin subunit. The modulatory activity of CD151 toward alpha3beta1 was specific, because stable knockdown of three other tetraspanins (i.e. CD9, CD63, and CD81) did not affect glycosylation of the integrin. Analysis of alpha3 glycosylation in CD151-depleted breast cancer cells with reconstituted expression of various CD151 mutants has shown that a direct contact with integrin is required but not sufficient for the modulatory activity of the tetraspanin toward alpha3beta1. We also found that glycosylation of CD151 is also critical; Asn(159) --> Gln mutation in the large extracellular loop did not affect interactions of CD151 with other tetraspanins or alpha3beta1 but negated its modulatory function. Changes in the glycosylation pattern of alpha3beta1 observed in CD151-depleted cells correlated with a dramatic decrease in cell migration toward laminin-332. Migration toward fibronectin or static adhesion of cells to extracellular matrix ligands was not affected. Importantly, reconstituted expression of the wild-type CD151 but not glycosylation-deficient mutant restored the migratory potential of the cells. These results demonstrate that CD151 plays an important role in post-translation modification of alpha3beta1 integrin and strongly suggest that changes in integrin glycosylation are critical for the promigratory activity of this tetraspanin.
    Preview · Article · Nov 2008 · Journal of Biological Chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: The receptor tyrosine kinase c-KIT plays a key role in normal mast cell development. Point mutations in c-KIT have been associated with sporadic or familial mastocytosis. Two unrelated pairs of apparently identical twins affected by cutaneous mastocytosis attending the Mastocytosis Clinic at the Royal Children's Hospital, Melbourne, provided an opportunity to assess the possible contribution of c-KIT germline mutations or polymorphisms in this disease. Tissue biopsy, blood and/or buccal swab specimens were collected from 10 children with mastocytosis. To detect germline mutations/polymorphisms in c-KIT, we studied all coding exons by denaturing high pressure liquid chromatography. Exons showing mismatches were examined by direct sequencing. The influence of the substitution identified was further examined by expressing the variant form of c-KIT in factor-dependent FDC-P1 cells. In both pairs of twins, a heterozygous ATG to CTG transition in codon 541 was observed, resulting in the substitution of a methionine residue in the transmembrane domain by leucine (M541L). In each case, one parent was also heterozygous for this allele. Expression of M541L KIT in FDC-P1 cells enabled them to grow in human KIT ligand (stem cell factor, SCF) but did not confer factor independence. Compared with cells expressing wild-type KIT at a similar level, M541L KIT-expressing cells displayed enhanced growth at low levels of SCF, and heightened sensitivity to the KIT inhibitor, imatinib mesylate. The data suggest that the single nucleotide polymorphism resulting in the substitution M541L may predispose to paediatric mastocytosis.
    No preview · Article · Oct 2008 · British Journal of Dermatology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Platelets are essential for wound healing and inflammatory processes, but can also play a deleterious role by causing heart attack and stroke. Normal platelet activation is dependent on tetraspanins, a superfamily of glycoproteins that function as 'organisers' of cell membranes by recruiting other receptors and signalling proteins into tetraspanin-enriched microdomains. However, our understanding of how tetraspanin microdomains regulate platelets is hindered by the fact that only four of the 33 mammalian tetraspanins have been identified in platelets. This is because of a lack of antibodies to most tetraspanins and difficulties in measuring mRNA, due to low levels in this anucleate cell. To identify potentially platelet-expressed tetraspanins, mRNA was measured in their nucleated progenitor cell, the megakaryocyte, using serial analysis of gene expression and DNA microarrays. Amongst 19 tetraspanins identified in megakaryocytes, Tspan9, a previously uncharacterized tetraspanin, was relatively specific to these cells. Through generating the first Tspan9 antibodies, Tspan9 expression was found to be tightly regulated in platelets. The relative levels of CD9, CD151, Tspan9 and CD63 were 100, 14, 6 and 2 respectively. Since CD9 was expressed at 49000 cell surface copies per platelet, this suggested a copy number of 2800 Tspan9 molecules. Finally, Tspan9 was shown to be a component of tetraspanin microdomains that included the collagen receptor GPVI (glycoprotein VI) and integrin alpha6beta1, but not the von Willebrand receptor GPIbalpha or the integrins alphaIIbbeta3 or alpha2beta1. These findings suggest a role for Tspan9 in regulating platelet function in concert with other platelet tetraspanins and their associated proteins.
    Full-text · Article · Oct 2008 · Biochemical Journal
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: CD151, a member of the tetraspanin family of proteins, forms a stable complex with integrin alpha 3 beta 1 and regulates integrin-mediated cell-substrate adhesion. However, the molecular basis of the stable association of CD151 with integrin alpha 3 beta 1 remains poorly understood. In the present study, we show that a panel of anti-human CD151 mAbs (monoclonal antibodies) could be divided into three groups on the basis of their abilities to co-immunoprecipitate integrin alpha 3: Group-1 mAbs were devoid of sufficient activities to co-precipitate integrin alpha 3 under both low- and high-stringency detergent conditions; Group-2 mAbs co-precipitated integrin alpha 3 under low-stringency conditions; and Group-3 mAbs exhibited strong co-precipitating activities under both conditions. Group-1 mAbs in particular exhibited increased reactivity toward integrin alpha 3 beta 1-unbound CD151, indicating that the binding sites for Group-1 mAbs are partly blocked by bound integrin alpha 3 beta 1. Epitope mapping using a series of CD151 mutants with substitutions at amino acid residues that are not conserved between human and mouse CD151 revealed that Gly(176)/Gly(177), Leu(191) and Gln(194) comprise epitopes characteristic of Group-1 mAbs. Replacement of short peptide segments, each containing one of these epitopes, with those of other tetraspanins lacking stable interactions with integrin alpha 3 beta 1 demonstrated that the segment from Cys(185) to Cys(192), including Leu(191), was involved in the stable association of CD151 with integrin alpha 3 beta 1, as was the Gln(194)-containing QRD peptide. Taken together these results indicate that two consecutive segments including two Group-1 epitopes, Leu(191) and Gln(194), comprise an interface between CD151 and integrin alpha 3 beta 1, and, along with the epitope including Gly(176)/Gly(177), are concealed by bound integrin.
    Full-text · Article · Aug 2008 · Biochemical Journal
  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigated the role of the hematopoietic-specific tetraspanin superfamily member, TSSC6, in platelet function using wild-type mice and TSSC6-deficient mice. TSSC6 is expressed on the surface of murine platelets and is up-regulated by thrombin stimulation, indicating an intracellular pool of TSSC6. Immunoprecipitation/Western blot studies reveal a constitutive physical association of TSSC6 with the integrin αIIbβ3 complex under strong detergent conditions. In vivo evaluation of hemostasis by tail bleeding revealed increased bleeding time, volume of blood lost, and evidence of tail rebleeds in TSSC6 null mice, indicating unstable hemostasis. Using ex vivo techniques, we showed that TSSC6-deficient platelets exhibited impaired kinetics of clot retraction, platelet aggregation at lower doses of PAR-4, and collagen and platelet spreading on fibrinogen in the presence of normal integrin αIIbβ3 expression. TSSC6-deficient platelets showed normal alpha granule secretion, normal "inside-out" integrin αIIbβ3 signaling (fluorescein isothiocyanate [FITC]-fibrinogen and JON/A binding), and normal platelet adhesion on fibrinogen. Furthermore, we show that absence of platelet TSSC6 affects the secondary stability of arterial thrombi in vivo upon vascular injury. These data demonstrate that TSSC6 appears to regulate integrin αIIbβ3 "outside-in" signaling events in platelets and is necessary for stability of arterial thrombi in vivo.
    No preview · Article · Jul 2007 · Journal of Thrombosis and Haemostasis
  • [Show abstract] [Hide abstract]
    ABSTRACT: The tetraspanin web refers to a network of molecular interactions involving tetraspanins and other molecules. Inside the tetraspanin web, small primary complexes containing only one tetraspanin and one specific partner molecule such as CD151/alpha3beta1 integrin and CD9/CD9P-1 (FPRP) can be observed under particular conditions. Here we demonstrate that when cells are lysed with Brij97, the tetraspanins CD151 and CD9 allow and/or stabilize the interaction of their partner molecules with other tetraspanins and that their two partners associate under conditions maintaining tetraspanin/tetraspanin interactions. The tetraspanins were also found to partition into a detergent-resistant membrane environment to which the integrin alpha3beta1 was relocalized upon expression of CD151.
    No preview · Article · Nov 2006
  • R Griffith · M N Brown · A McCluskey · L K Ashman
    [Show abstract] [Hide abstract]
    ABSTRACT: Small molecule protein kinase inhibitors show great promise as anti-cancer agents, however, de novo and acquired resistance present problems. These are reviewed and illustrated using the receptor tyrosine kinase, KIT, as an example. Emerging solutions are presented, such as targeting active kinase conformations.
    No preview · Article · Nov 2006 · Mini Reviews in Medicinal Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The basement membrane protein laminin-5 supports tumor cell adhesion and motility and is implicated at multiple steps of the metastatic cascade. Tetraspanin CD151 engages in lateral, cell surface complexes with both of the major laminin-5 receptors, integrins alpha3beta1 and alpha6beta4. To determine the role of CD151 in tumor cell responses to laminin-5, we used retroviral RNA interference to efficiently silence CD151 expression in epidermal carcinoma cells. Near total loss of CD151 had no effect on steady state cell surface expression of alpha3beta1, alpha6beta4, or other integrins with which CD151 associates. However, CD151-silenced carcinoma cells displayed markedly impaired motility on laminin-5, accompanied by unusually persistent lateral and trailing edge adhesive contacts. CD151 silencing disrupted alpha3beta1 integrin association with tetraspanin-enriched microdomains, reduced the bulk detergent extractability of alpha3beta1, and impaired alpha3beta1 internalization in cells migrating on laminin-5. Both alpha3beta1- and alpha6beta4-dependent cell adhesion to laminin-5 were also impaired in CD151-silenced cells. Reexpressing CD151 in CD151-silenced cells reversed the adhesion and motility defects. Finally, loss of CD151 also impaired migration but not adhesion on substrates other than laminin-5. These data show that CD151 plays a critical role in tumor cell responses to laminin-5 and reveal promotion of integrin recycling as a novel potential mechanism whereby CD151 regulates tumor cell migration.
    Full-text · Article · Jul 2006 · Molecular Biology of the Cell
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In vivo models that recapitulate oncogene-dependent tumorigenesis will greatly facilitate development of molecularly targeted anticancer therapies. We have developed a model based on activating mutations in c-KIT in gastrointestinal stromal tumors (GISTs). This model comprises murine tumors of FDC-P1 cell lines expressing c-KIT mutations that render the tumors either responsive (V560G) or resistant (D816V) to the small-molecule c-KIT inhibitor, imatinib. Clinically, GIST response to imatinib is associated with rapid reduction in fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET), preceding changes in conventional response criteria by several weeks. Using the FDC-P1 model in small animal PET, FDG uptake into tumors expressing the c-KIT V560G mutation was significantly reduced as early as 4 hours after imatinib treatment. In contrast, no change in FDG uptake was observed in resistant c-KIT D816V-expressing tumors after 48 hours of imatinib treatment. Consistent with the PET results, expression of the glucose transporter, GLUT1, was significantly reduced in V560G tumors at 4 hours, preceding changes in markers of proliferation by several hours. In vitro, imatinib treatment of V560G cells resulted in a reduction of glucose transporter numbers at the cell surface and decreased glucose uptake well before changes in cell viability. Notably, decreased ambient glucose concentrations enhanced the cytotoxic effect of imatinib. Taken together, these data account for the rapidity and significance of the PET response to imatinib and suggest that metabolic effects may contribute to imatinib cytotoxicity. Further, the FDC-P1 model represents a very useful paradigm for molecularly targeted drug development.
    Full-text · Article · Dec 2005 · Cancer Research

Publication Stats

6k Citations
607.65 Total Impact Points


  • 2003-2014
    • University of Newcastle
      • • Faculty of Health and Medicine
      • • School of Biomedical Sciences and Pharmacy
      • • Department of Biological Sciences
      Newcastle, New South Wales, Australia
    • IMVS Pathology
      • Haematology Division
      Tarndarnya, South Australia, Australia
  • 1993-2001
    • Adelaide Cancer Centre
      Tarndarnya, South Australia, Australia
    • Richmond VA Medical Center
      Ричмонд, Virginia, United States
  • 1983-2001
    • University of Adelaide
      • • School of Medicine
      • • Discipline of Microbiology and Immunology
      Tarndarnya, South Australia, Australia
  • 1998
    • Universidad Autónoma de Madrid
      • Department of Immunology
      Madrid, Madrid, Spain
    • Ear Science Institute Australia
      Subiaco, Western Australia, Australia
  • 1995-1996
    • Virginia Commonwealth University
      • Department of Internal Medicine
      Richmond, VA, United States
  • 1992
    • Universitätsklinikum Freiburg
      • Department of Internal Medicine I
      Freiburg an der Elbe, Lower Saxony, Germany
  • 1989-1992
    • University of Vienna
      • Institute of Social Medicine
      Wien, Vienna, Austria