title: Expression profiling of the influence of RAS mutants on the TGFB1-induced phenotype of the pancreatic cancer cell line PANC-1.
abstract: Expression profiling analyses were used to elucidate the functional relevance of RAS proteins in mediating the effect of TGFB1 on the transcriptional phenotype of the pancreatic cancer cell line PANC-1. Despite the presence of one mutated KRAS2 allele in parental PANC-1 pancreatic cancer cells, RAS-dependent signal transduction remained susceptible to stimulation by EGF and TGFB1. To analyze the impact of RAS proteins on the TGFB1-induced transcriptional phenotype, we used PANC-1 cells stably transfected with a dominant negative HRAS(S17N) mutant or with a constitutively active KRAS2(G12V) mutant. TGFB1 treatment of mock-transfected PANC-1 cells led to an expression profile suggestive of epithelial-mesenchymal transdifferentiation (EMT). Profiling of the HRAS(S17N)-expressing clone demonstrated that induction of endogenous RAS activity by TGFB1 is required for the development of the TGFB1-induced transcriptional phenotype of PANC-1 cells. The expression of the KRAS2(G12V) mutant by itself repressed transcription of markers of epithelial differentiation and induced transcription of several extracellular matrix-associated genes. This effect was not enhanced further by TGFB1 treatment. In contrast, transcript levels of genes associated with proliferation and cell cycle progression did not appear to be the primary targets of the synergism between the RAS- and TGFB1-dependent cascades. The introduction of the dominant negative and the constitutively active RAS mutants induced partly overlapping and partly inverse effects on the TGFB1-induced expression profile of PANC-1 cells. Additional mechanisms such as the induction of autocrine loops and the use of different RAS isoforms or alternate, ERK-independent signaling pathways may be involved in the interaction between the RAS- and the TGFB1-dependent signaling cascades.
authors.affiliation: Department of Internal Medicine I, University of Ulm, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Fensterer
authors.forename: Klaudia
authors.initials: K
authors.lastname: Giehl
authors.forename: Malte
authors.initials: M
authors.lastname: Buchholz
authors.forename: Volker
authors.initials: V
authors.lastname: Ellenrieder
authors.forename: Anita
authors.initials: A
authors.lastname: Buck
authors.forename: Hans A
authors.initials: HA
authors.lastname: Kestler
authors.forename: Guido
authors.initials: G
authors.lastname: Adler
authors.forename: Peter
authors.initials: P
authors.lastname: Gierschik
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gress
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D016000:Cluster Analysis; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000235:genetics; D020869:Gene Expression Profiling / Q000379:methods* / Q000706:statistics & numerical data; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D009154:Mutation / Q000235:genetics* / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods / Q000706:statistics & numerical data; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000473:pathology*; D010641:Phenotype; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics* / Q000502:physiology; D011994:Recombinant Proteins / Q000235:genetics; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology*; D053773:Transforming Growth Factor beta1; D018631:ras Proteins
chemical_list: D016895:Culture Media, Serum-Free; D004273:DNA, Neoplasm; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins