title: HNRNP G and HTRA2-BETA1 regulate estrogen receptor alpha expression with potential impact on endometrial cancer.
abstract: BACKGROUND
  Estrogen receptor alpha (ERa/ESR1) expression is regulated by alternative splicing. Its most frequently detectable exon7 skipping isoform (ERaD7) is a dominant negative variant. Elevated expression of ERaD7 was already detected in endometrial cancer (EC), while its potential prognostic significance has not been characterized so far. Exon7 contains potential binding sites for the two functional splicing regulatory opponents, HNRNPG and HTRA2-BETA1 known to trigger opposite effects on EC outcome. This study served to elucidate the influence of HNRNPG and HTRA2-BETA1 on ERa exon7 splicing regulation and the impact of ERaD7 concentration on type 1 EC outcome.
  
  
  METHODS
  Functional in vitro experiments for HNRNPG and HTRA2-BETA1 in regard to the regulatory impact on endogenous and exogenous ERaD7 splicing were performed. Additionally, real-time PCR determined mRNA levels of ERaD7, HNRNPG and HTRA2-BETA1 in 116 type 1 EC patients.
  
  
  RESULTS
  HNRNPG and HTRA2-BETA1 were found to be specific regulators of ERa exon7 splicing. While HTRA2-BETA1 promoted exon7 inclusion, HNRNPG antagonized this effect by inducing exon7 skipping (p = 0.004). ERaD7 was detected in 71 out of 116 type 1 EC specimens. Statistical analyses revealed an inverse correlation between ERaD7 mRNA levels and tumor grading (p = 0.029), FIGO stage (p = 0.033) as well as lymph node metastases (p = 0.032), respectively. Furthermore, higher ERaD7 expression could be correlated to an improved disease-specific survival (p = 0.034).
  
  
  CONCLUSIONS
  Our study demonstrates antagonistic regulatory effects of HNRNPG and HTRA2-BETA1 on ERa exon7 splicing with potential impact on type 1 EC clinical outcome due to the consecutively variable expression levels of the ERa isoform D7.
authors.affiliation: Department of Obstetrics and Gynecology, University Medical Center Freiburg, Hugstetterstr 55, 79106, Freiburg, Germany. marc.hirschfeld@uniklinik-freiburg.de.|German Cancer Consortium (DKTK), Heidelberg, Germany. marc.hirschfeld@uniklinik-freiburg.de.|German Cancer Research Center (DKFZ), Heidelberg, Germany. marc.hirschfeld@uniklinik-freiburg.de.
authors.forename: Marc
authors.initials: M
authors.lastname: Hirschfeld
authors.affiliation: Department of Obstetrics and Gynecology, Tongji Hospital of Tongji University, Shanghai, China. oyy91124@hotmail.com.
authors.forename: Yi Qin
authors.initials: YQ
authors.lastname: Ouyang
authors.affiliation: Department of Obstetrics and Gynecology, University Medical Center Freiburg, Hugstetterstr 55, 79106, Freiburg, Germany. markus.jaeger@uniklinik-freiburg.de.
authors.forename: Markus
authors.initials: M
authors.lastname: Jaeger
authors.affiliation: Department of Obstetrics and Gynecology, University Medical Center Freiburg, Hugstetterstr 55, 79106, Freiburg, Germany. thalia.erbes@uniklinik-freiburg.de.
authors.forename: Thalia
authors.initials: T
authors.lastname: Erbes
authors.affiliation: Institute of Pathology, University Medical Center Freiburg, Freiburg, Germany. marzenna.orlowska-volk@uniklinik-freiburg.de.
authors.forename: Marzenna
authors.initials: M
authors.lastname: Orlowska-Volk
authors.affiliation: Institute of Pathology, University Medical Center Freiburg, Freiburg, Germany. axel.zurhausen@mumc.nl.|Department of Pathology, Maastricht University Medical Center, Maastricht, The Netherlands. axel.zurhausen@mumc.nl.
authors.forename: Axel
authors.initials: A
authors.lastname: Zur Hausen
authors.affiliation: Department of Obstetrics and Gynecology, University Medical Center Freiburg, Hugstetterstr 55, 79106, Freiburg, Germany. elmar.stickeler@uniklinik-freiburg.de.
authors.forename: Elmar
authors.initials: E
authors.lastname: Stickeler
mesh_terms: D017398:Alternative Splicing; D001665:Binding Sites; D045744:Cell Line, Tumor; D016889:Endometrial Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D047628:Estrogen Receptor alpha / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005091:Exons; D005260:Female; D006367:HeLa Cells; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011379:Prognosis; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000068103:Serine-Arginine Splicing Factors
chemical_list: C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009419:Nerve Tissue Proteins; C510272:RBMX protein, human; D016601:RNA-Binding Proteins; C097083:TRA2B protein, human; D000068103:Serine-Arginine Splicing Factors