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Rosemary J Akhurst

Publications and source records attributed to Rosemary J Akhurst.

15 recordsLinked to original sources
PubMed2006

Genetic variants of Tgfb1 act as context-dependent modifiers of mouse skin tumor susceptibility.

The human TGFB1 gene is polymorphic, and genetic variants are associated with altered cancer risk. However, human genetic association studies have had variable outcomes because TGFbeta1 action is context-dependent. We used the murine skin model of chemical carcinogenesis in genetic linkage analysis of three independent Mus musculus NIH/Ola x (Mus spretus x M. musculus NIH/Ola)F1 backcrosses, to identify a skin tumor susceptibility locus, Skts14, on proximal chromosome 7. Tgfb1 maps at the peak of linkage. The mouse Tgfb1 gene is polymorphic, resulting in cis-regulated differential allelic mRNA expression between M. spretus and M. musculus in F1 mouse skin. This phenomenon is reflected in differential phospho-SMAD2 levels, downstream of TGFbeta signaling, between these two mouse species. In normal F1 mouse skin, the Tgfb1SPR allele is expressed at higher levels than the Tgfb1NIH allele, and this differential is accentuated by phorbol 12-myristate 13-acetate treatment. In benign F1 papillomas, this imbalance is reversed, possibly by selection against expression of a hyperactive Tgfb1SPR allele in TGFbeta growth-responsive tumors. We demonstrate that skin tumor susceptibility is altered by Tgfb1 gene dosage, but that manifestation of Tgfb1-linked skin tumor susceptibility in M. musculus NIH/Ola x (M. spretus x M. musculus NIH/Ola)F1 backcross mice depends on interactions with another unlinked tumor modifying locus, Skts15, that overlaps Tgfbm3 on chromosome 12. These findings illustrate the power of complex genetic interactions in determining disease outcome and have major implications to the assessment of disease risk in individuals harboring variant TGFB1 alleles.

Alleles↗
PubMed2006

Transforming growth factor-beta receptor inhibition enhances adenoviral infectability of carcinoma cells via up-regulation of Coxsackie and Adenovirus Receptor in conjunction with reversal of epithelial-mesenchymal transition.

Expression of the Coxsackie and Adenovirus Receptor (CAR) is frequently reduced in carcinomas, resulting in decreased susceptibility of such tumors to infection with therapeutic adenoviruses. Because CAR participates physiologically in the formation of tight-junction protein complexes, we examined whether molecular mechanisms known to down-regulate cell-cell adhesions cause loss of CAR expression. Transforming growth factor-beta (TGF-beta)-mediated epithelial-mesenchymal transition (EMT) is a phenomenon associated with tumor progression that is characterized by loss of epithelial-type cell-cell adhesion molecules (including E-cadherin and the tight junction protein ZO-1), gain of mesenchymal biochemical markers, such as fibronectin, and acquisition of a spindle cell phenotype. CAR expression is reduced in tumor cells that have undergone EMT in response to TGF-beta. This down-regulation results from repression of CAR gene transcription, whereas altered RNA stability and increased proteasomal protein degradation play no role. Loss of CAR expression in response to TGF-beta is accompanied by reduced susceptibility to adenovirus infection. Indeed, treatment of carcinoma cells with LY2109761, a specific pharmacologic inhibitor of TGF-beta receptor types I and II kinases, resulted in increased CAR RNA and protein levels as well as improved infectability with adenovirus. This was observed in cells induced to undergo EMT by addition of exogenous TGF-beta and in those that were transformed by endogenous autocrine/paracrine TGF-beta. These findings show down-regulation of CAR in the context of EMT and suggest that combination of therapeutic adenoviruses and TGF-beta receptor inhibitors could be an efficient anticancer strategy.

Adenoviridae↗
PubMed2006

TGFbeta inhibition of yolk-sac-like differentiation of human embryonic stem-cell-derived embryoid bodies illustrates differences between early mouse and human development.

Transforming growth factor beta (TGFbeta) plays an important role in development and maintenance of murine yolk sac vascular development. Targeted deletions of Tgfb1 and other components of this signaling pathway, such as Acvrl1, Tgfbr1 and Tgfbr2, result in abnormal vascular development especially of the yolk sac, leading to embryonic lethality. There are significant differences between murine and primate development that limit interpretation of studies from mouse models. Thus, to examine the role of TGFbeta in early human vascular development we used the model of differentiating human embryonic stem cell-derived embryoid bodies to recapitulate early stages of embryonic development. TGFbeta was applied for different time frames after initiation of embryoid body cultures to assess its effect on differentiation. TGFbeta inhibited the expression of endodermal, endothelial and hematopoietic markers, which contrasts with findings in the mouse in which TGFbeta reduced the level of endodermal markers but increased endothelial marker expression. The inhibition observed was not due to changes in proliferation or apoptosis. This marked contrast between the two species may reflect the different origins of the yolk sac hemangiogenic lineages in mouse and human. TGFbeta effects on the hypoblast, from which these cell lineages are derived in human, would decrease subsequent differentiation of hematopoietic, endothelial and endodermal cells. By contrast, TGFbeta action on murine hypoblast, while affecting endoderm would not affect the hemangiogenic lineages that are epiblast-derived in the mouse. This study highlights important differences between early human and mouse embryonic development and suggests a role of TGFbeta in human hypoblast differentiation.

Activin Receptors, Type I↗
PubMed2006

Mutations of TGFbeta signaling molecules in human disease.

The transforming growth factor beta (TGFbeta) signaling pathway regulates several biological processes including cellular proliferation, differentiation, apoptosis, migration, and extracellular matrix deposition. Ligand and receptor family members signal through two main Smad signaling branches, TGFbeta/activin to Smad2/3 (Sma and MAD-related proteins) and bone morphogenetic protein (BMP) to Smad1/5. At the molecular level, TGFbeta acts by modifying cytoskeletal organization and ultimately regulating expression of specific target genes. Germline disruption of TGFbeta signaling leads to several types of hereditary congenital malformation or dysfunction of the skeletal, muscular and/or cardiovascular systems, and to cancer predisposition syndromes. In this review, the molecular etiology of TGFbeta-associated disorders is examined, together with a discussion of clinical overlap between syndromes and possible biological explanations underlying the variable penetrance and expressivity of clinical characteristics. Increasing our understanding of the molecular etiology underlying genotype-phenotype correlations will ultimately provide a molecular-based approach that should result in better prognostic tools, smart therapeutics and individualized disease management, not only for these rare syndromes, but for more generalized disorders of the cardiovascular and musculoskeletal systems and cancer. The clinical consequence of TGFbeta signaling mutations appears to depend on environmental factors and on the basal levels of ongoing signaling transduction networks specific to each individual. In this respect, genetic background might be a central factor in determining disease outcome and treatment strategy for TGFbeta-associated diseases.

Genetic Diseases, Inborn↗
PubMed2006

TGF beta inhibition for cancer therapy.

The importance of perturbation in transforming growth factor beta (TGFbeta) signaling for the onset and progression of cancer is well established. Many tumors over express TGFbeta, and high circulating levels of TGFbeta1 in cancer patients are frequently associated with poor prognosis. TGFbeta has context-dependent biphasic action during tumorigenesis. Because of this, it is essential to take due care about the selection of patients most likely to benefit from anti-TGFbeta therapy. Anti-TGFbeta therapy aims to target both the tumor cell and the tumor microenvironment and may well have systemic effects of relevance to tumorigenesis. Extra-tumoral targets include stromal fibroblasts, endothelial and pericyte cells during angiogenesis, and the local and systemic immune systems, all of which can contribute to the pro-oncogenic effects of TGFbeta. Many different approaches have been considered, such as interference with ligand synthesis using oligonucleotides, sequestration of extracellular ligand using naturally-occurring TGFbeta binding proteins, recombinant proteins or antibodies, targeting activation of latent TGFbeta at the cell surface, or signal transduction within the cell. Consideration of which patients might benefit most from anti-TGFbeta therapy should include not only tumor responses to TGFbeta (which depend on activation of other oncogenic pathways in the cancer cell), but also germline genetic variation between individuals. Ultimately, a deep understanding of the interacting networks of signal pathways that regulate TGFbeta outcome in tumor and host cells should allow judicial choice of drugs. This review discusses the progress made in the pre-clinical and clinical testing of TGFbeta inhibitors, and discusses considerations of target populations and potential drug regimens.

Animals↗
PubMed2006

Large- and small-molecule inhibitors of transforming growth factor-beta signaling.

A variety of drugs have been developed to inhibit transforming growth factor (TGF)beta signaling. These drugs have been designed to block TGFbeta synthesis, ligand/receptor binding or receptor kinase signaling. Preclinical studies using TGFbeta inhibitors have demonstrated efficacy in reducing metastasis and have shown improvements in cytotoxic drug delivery. Results of phase I/II clinical trials of TGFbeta inhibitors in patients with glioblastoma suggest improved survival rates compared with conventional chemotherapy. The predominant cellular target, whether cancer or stromal cell, immune cell or angiogenesis, may differ between tumor types. Different individuals may show variable responses to drug therapy dependent on both germline genetic variation and the somatic mutation profile of the tumor. A deeper understanding of these issues will assist in targeting the right patients for such therapy, and in limiting unwanted side effects.

Animals↗
PubMed2005

Epistatic interactions between modifier genes confer strain-specific redundancy for Tgfb1 in developmental angiogenesis.

Tgfbm1 (chromosome 5, P = 8 x 10(-5)) and Tgfbm3 (chromosome 12, P = 6 x 10(-11)) were identified as loci that modify developmental angiogenesis of Tgfb1 -/- mice. Congenic mice validated these loci and demonstrated epistatic interaction between them. The novel locus, Tgfbm3, encompasses approximately 22 genes, colocalizes with both tumor susceptibility and atherosclerosis susceptibility loci, and is enriched in genes regulating cell growth and morphogenesis. The use of gene knockout and/or transgenic mice that predispose to a complex trait, such as vascular development/angiogenesis, facilitates the identification of modifiers by simplifying genetic analysis. Identification of genes that modify response to lack of transforming growth factor beta1 (TGFbeta1) will enhance the understanding of TGFbeta1 action in vivo and may help predict which patients would respond well to anti-TGFbeta therapy. Identification of angiogenesis-modifying genes may provide new targets for angiogenesis therapies and analysis of polymorphisms therein may contribute to assessment of risk for diseases involving angiogenesis.

Animals↗
PubMed2004

Mouse strain-dependent heterogeneity of resting limbal vasculature.

PURPOSE: Heterogeneity of the extent of angiogenesis induced by exogenous growth factors may be determined by genetic influences. Because angiogenesis is the formation of new vessels from preexisting ones, strain-related influences on naïve resting limbal vessel phenotype and gene expression were determined in mice having divergently low and high angiogenic responses. METHODS: Resting limbal vessel surface area and density and extent of bFGF-induced corneal angiogenesis were determined in C57BL/6J, BALB/cJ, F1 intercross identical with C57BL/6J X 129S3/SvIM, and 129S3/SvIM mouse strains by quantitative three-dimensional reconstruction confocal microscopy. Strain-related influences on pro- and antiangiogenic gene expression in naïve cornea were determined by quantitative real-time RT-PCR. RESULTS: The strain-dependent rank order of resting limbal vessel surface area and resting vessel density paralleled bFGF-induced neovascularization: 129S3/SvIM > BALB/cJ, F1 > C57BL/6J (P < 0.0006). Pigment epithelium-derived factor (PEDF) was increased more than 67-fold compared to Ang-2 in resting cornea of both C57BL/6J and 129S3/SvIM strains (P < 0.0001; P < 0.0001), suggesting a strongly antiangiogenic environment. The corneas of the C57BL/6J mice demonstrated 1.8-, 1.5-, and 1.7-fold increased mRNA levels for Flt-1, VEGF, and bFGF, respectively (P < 0.02; P < 0.04; P < 0.02); however, TSP-1 expression was increased 2.4-fold compared with 129S3/SvIM (P < 0.0004). CONCLUSIONS: Strain-dependent differences in the resting limbal vessel surface area and density correlated with heterogeneity in the extent of bFGF-induced angiogenesis. Differences in pro- and antiangiogenic gene expression levels in resting cornea may influence vascular limbal phenotype during quiescence and may predict susceptibility to angiogenesis-dependent diseases.

Angiopoietin-2↗
PubMed2003

Genetic modifiers interact with maternal determinants in vascular development of Tgfb1(-/-) mice.

The transforming growth factor beta signaling family is a key player in genetic and multifactorial diseases, including hereditary hemorrhagic telangiectasia (HHT), cancer, atherosclerosis and immunomodulation. HHT types 1 and 2 are caused by loss of function mutations in ENG and ACVRL1; polymorphisms in TBRI and TGFB1 are also associated with altered risks for cancer and cardiovascular diseases. There is therefore much interest in identifying factors that influence transforming growth factor beta1 (TGFbeta1) action in vivo. Here we identify a potent modifier locus, Tgfbkm2(129) (LOD=10.5, chromosome 1), that contributes over 90% of the genetic component determining survival to birth of Tgfb1(-/-) embryos in crosses between C57 and 129 mice, plus a suggestive modifier locus on chromosome 17 (LOD=3.7). Tgfb1(-/-) survival to birth (STB), in addition to dependence on embryonic Tgfbkm2 genotype, also depends on maternal effects. Fetal genotype and maternal factors interact to prevent Tgfb1(-/-) embryonic death due to defective yolk sac angiogenesis. C57 or C57/129.F1 mothers support high Tgfb1(-/-) STB rates, whereas 129 mothers do not. Strain differences in circulating maternal TGFbeta1 levels were excluded as the cause of this directional complementation. However, strong genetic support is provided for the involvement of maternal STB alleles of mitochondrial or imprinted genes that are only expressed when passed through the female lineage. Molecular identification of the functional gene(s) encoding Tgfbkm2 and its interacting maternal factors will be central to an understanding of the mode of action of TGFbeta1 in cardiovascular development.

Alleles↗
PubMed2002

Transforming growth factor-beta1 mediates cellular response to DNA damage in situ.

Transforming growth factor (TGF)-beta1 is rapidly activated after ionizing radiation, but its specific role in cellular responses to DNA damage is not known. Here we use Tgfbeta1 knockout mice to show that radiation-induced apoptotic response is TGF-beta1 dependent in the mammary epithelium, and that both apoptosis and inhibition of proliferation in response to DNA damage decrease as a function of TGF-beta1 gene dose in embryonic epithelial tissues. Because apoptosis in these tissues has been shown previously to be p53 dependent, we then examined p53 protein activation. TGF-beta1 depletion, by either gene knockout or by using TGF-beta neutralizing antibodies, resulted in decreased p53 Ser-18 phosphorylation in irradiated mammary gland. These data indicate that TGF-beta1 is essential for rapid p53-mediated cellular responses that mediate cell fate decisions in situ.

Animals↗
PubMed2002

Metastasis is driven by sequential elevation of H-ras and Smad2 levels.

Metastasis is a multistep process that involves local tumour invasion followed by dissemination to, and re-establishment at, distant sites. Here we show that during multistage tumorigenesis, discrete expression thresholds of activated Smad2 and H-ras are sequentially surpassed, driving tumour progression through distinct phases from a differentiated squamous carcinoma to a motile invasive stage, followed by an overt change from epithelial to mesenchymal cell type, finally culminating in metastatic tumour spread. Smad2 activation alone induces migration of tumour cells. Elevated H-ras levels, however, are required for nuclear accumulation of Smad2, both of which are essential for the epithelial mesenchymal transition (EMT). Having undergone EMT, fibroblastoid carcinoma cells with elevated levels of activated Smad2, gain the capability to spread to a wide variety of tissues by a further increase in Smad2 expression. These findings have far-reaching implications for the prevention of tumour growth, invasion and metastasis.

Animals↗