ABSTRACT
The discovery of occult invasive and intra-epithelial tubal carcinomas in BRCA1 mutation carriers undergoing prophylactic surgery has implicated the fallopian tube epithelium as the source of serous cancer. However, little is known of the early molecular events of serous oncogenesis, or why cancers in BRCA1 mutation carriers are found preferentially in tissues which are responsive to reproductive hormones. We hypothesize that molecular alterations present in morphologically normal tubal epithelium from BRCA1 heterozygotes reflect the earliest events in serous carcinogenesis and may be markers of increased cancer risk as well as targets for risk reduction. Genetic profiling of microdissected tubal epithelium from histologically normal BRCA1 mutation carriers and controls was performed. We sought to define a signature which differentiated BRCA1 mutant tubal epithelium from women with low risk of developing ovarian cancer. Molecular differences between the follicular and luteal phases were prominent and, by using filtering techniques and a two-way ANOVA without a False Discovery Rate correction, we identified 440 probe sets with a more than two-fold change in gene expression related to BRCA1 mutation status. Using gene ontology and known associations to cancer pathways, we selected five genes for further analysis by qPCR and immunohistochemistry, and were able to demonstrate statistically significant differentiation of BRCA1 and control cases in an independent set of cases. The altered expression profiles in histologically normal tubal epithelium from BRCA1 heterozygotes suggest that these cells may respond differently to microenvironmental stresses.
Subject(s)
Cystadenocarcinoma, Serous/genetics , Fallopian Tube Neoplasms/genetics , Genes, BRCA1 , Mutation , Precancerous Conditions/genetics , Adult , Case-Control Studies , Cluster Analysis , Cystadenocarcinoma, Serous/metabolism , Epithelium/metabolism , Fallopian Tube Neoplasms/metabolism , Fallopian Tubes/metabolism , Female , Follicular Phase/physiology , Gene Expression Profiling/methods , Gene Expression Regulation , Heterozygote , Humans , Luteal Phase/physiology , Microdissection/methods , Middle Aged , Oligonucleotide Array Sequence Analysis/methods , Precancerous Conditions/metabolism , Signal Transduction/geneticsABSTRACT
The Drosophila tumor suppressor gene fat encodes a large cadherin that regulates growth and a form of tissue organization known as planar cell polarity (PCP). Fat regulates growth via the Hippo kinase pathway, which controls expression of genes promoting cell proliferation and inhibiting apoptosis (reviewed in). The Hippo pathway is highly conserved and is implicated in the regulation of mammalian growth and cancer development. Genetic studies suggest that Fat activity is regulated by binding to another large cadherin, Dachsous (Ds). The tumor suppressor discs overgrown (dco)/Casein Kinase I delta/epsilon also regulates Hippo activity and PCP. The biochemical nature of how Fat, Ds, and Dco interact to regulate these pathways is poorly understood. Here we demonstrate that Fat is cleaved to generate 450 kDa and 110 kDa fragments (Fat(450) and Fat(110)). Fat(110) contains the cytoplasmic and transmembrane domain. The cytoplasmic domain of Fat binds Dco and is phosphorylated by Dco at multiple sites. Importantly, we show Fat forms cis-dimers and that Fat phosphorylation is regulated by Dachsous and Dco in vivo. We propose that Ds regulates Dco-dependent phosphorylation of Fat and Fat-associated proteins to control Fat signaling in growth and PCP.
Subject(s)
Cadherins/metabolism , Casein Kinase 1 epsilon/metabolism , Cell Adhesion Molecules/metabolism , Drosophila Proteins/metabolism , Drosophila melanogaster/physiology , Amino Acid Sequence , Animals , Cadherins/genetics , Casein Kinase 1 epsilon/genetics , Casein Kinase Idelta/genetics , Casein Kinase Idelta/metabolism , Cell Adhesion Molecules/genetics , Cell Line , Cell Polarity , Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Embryonic Stem Cells/cytology , Embryonic Stem Cells/physiology , Humans , Intracellular Signaling Peptides and Proteins/genetics , Intracellular Signaling Peptides and Proteins/metabolism , Ligands , Mice , Molecular Sequence Data , Phosphorylation , Protein Isoforms/genetics , Protein Isoforms/metabolism , Protein Processing, Post-Translational , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , TransgenesABSTRACT
The formation of a multi-nucleate myofibre is directed, in Drosophila, by a founder cell. In the embryo, founders are selected by Notch-mediated lateral inhibition, while during adult myogenesis this mechanism of selection does not appear to operate. We show, in the muscles of the adult abdomen, that the Fibroblast growth factor pathway mediates founder cell choice in a novel manner. We suggest that the developmental patterns of Heartbroken/Dof and Sprouty result in defining the domain and timing of activation of the Fibroblast growth factor receptor Heartless in specific myoblasts, thereby converting them into founder cells. Our results point to a way in which muscle differentiation could be initiated and define a critical developmental function for Heartbroken/Dof in myogenesis.
