title: Differential expression of hypoxia and (lymph)angiogenesis-related genes at different metastatic sites in breast cancer.
abstract: BACKGROUND
  Breast cancer can metastasize via lymphatic and hematogenous pathways. Hypoxia and (lymph)angiogenesis are closely related processes that play a pivotal role in the tumor progression and metastasis. The aim of this study was to compare expression of hypoxia and (lymph)angiogenesis-related genes between primary breast tumors and metastases in different tissues.
  
  
  METHODS
  A gene list of 269 hypoxia and (lymph)angiogenesis-related genes was composed and validated using Onto-Express, Pathway-express and Ingenuity software. The expression of these genes was compared in microarray data of 62 samples of primary tumors and metastases of 31 patients with breast cancer retrieved from Gene Expression Omnibus. Similarity between samples was investigated using unsupervised hierarchical clustering analysis, principal component analysis and permutation testing. Differential gene expression between primary tumors and metastases and between metastases from different organs was analyzed using Kruskall-Wallis and Mann-Whitney statistics.
  
  
  RESULTS
  Unsupervised hierarchical cluster analysis demonstrated that hypoxia and (lymph)angiogenesis-related gene expression was more similar between samples from the same patient, than between samples from the same organ. Principal component analysis indicated that 22.7% and 7.0% of the total variation in the gene list was respectively patient and organ related. When differences in gene expression were studied between different organs, liver metastases seemed to differ most from the other secondary sites. Some of the best characterized molecules differentially expressed were VEGFA, PDGFRB, FGF4, TIMP1, TGFB-R1 and collagen 18A1 (precursor of endostatin). To confirm the results of these experiments at the protein level, immunohistochemical experiments were performed with antibodies for VEGFA and MMP-2.
  
  
  CONCLUSIONS
  Our results suggest that hypoxia and (lymph)angiogenesis-related gene expression is more dependent on the characteristics of the primary tumor than on the characteristics of the organs that bear the metastasis. However, when different organs are compared, the expression in liver metastases differs most from other metastatic sites and primary tumors, possibly due to organ-specific angiogenic and lymphangiogenic responses to metastasis-related hypoxia.
authors.affiliation: Translational Cancer Research Group (Lab Pathology, University of Antwerp/University Hospital Antwerp, Oncology Center, General Hospital, St.-Augustinus), Wilrijk, Antwerp 2610, Belgium.
authors.forename: Gert G
authors.initials: GG
authors.lastname: Van den Eynden
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Van Laere
authors.forename: Ilse
authors.initials: I
authors.lastname: Van der Auwera
authors.forename: Leen
authors.initials: L
authors.lastname: Gilles
authors.forename: J Lance
authors.initials: JL
authors.lastname: Burn
authors.forename: Cecile
authors.initials: C
authors.lastname: Colpaert
authors.forename: Peter
authors.initials: P
authors.lastname: van Dam
authors.forename: Eric A
authors.initials: EA
authors.lastname: Van Marck
authors.forename: Luc Y
authors.initials: LY
authors.lastname: Dirix
authors.forename: Peter B
authors.initials: PB
authors.lastname: Vermeulen
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics*; D015687:Cell Hypoxia / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D042583:Lymphangiogenesis / Q000235:genetics*; D009362:Neoplasm Metastasis / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D025341:Principal Component Analysis