title: Rab31 expression levels modulate tumor-relevant characteristics of breast cancer cells.
abstract: BACKGROUND
  Rab proteins constitute a large family of monomeric GTP-binding proteins that regulate intracellular vesicle transport. Several Rab proteins, including rab31, have been shown to affect cancer progression and are related with prognosis in various types of cancer including breast cancer. Recently, the gene encoding rab31 was found to be overexpressed in estrogen receptor-positive breast cancer tissue. In a previous study we found a significant association of high rab31 mRNA expression with poor prognosis in node-negative breast cancer patients. In the present study, we aimed to investigate the impact of rab31 (over)-expression on important aspects of tumor progression in vitro and in vivo.
  
  
  METHODS
  Breast cancer cells displaying low (MDA-MB-231) or no (CAMA-1) endogenous rab31 expression were stably transfected with a rab31 expression plasmid. Batch-transfected cells as well as selected cell clones, expressing different levels of rab31 protein, were analyzed with regard to proliferation, cell adhesion, the invasive capacity of tumor cells, and in vivo in a xenograft tumor model. Polyclonal antibodies directed to recombinantly expressed rab31 were generated and protein expression analyzed by immunohistochemistry, Western blot analysis, and a newly developed sensitive ELISA.
  
  
  RESULTS
  Elevated rab31 protein levels were associated with enhanced proliferation of breast cancer cells. Interestingly, weak to moderate overexpression of rab31 in cell lines with no detectable endogenous rab31 expression was already sufficient to elicit distinct effects on cell proliferation. By contrast, increased expression of rab31 in breast cancer cells led to reduced adhesion towards several extracellular matrix proteins and decreased invasive capacity through Matrigel(TM). Again, the rab31-mediated effects on cell adhesion and invasion were dose-dependent. Finally, in a xenograft mouse model, we observed a significantly impaired metastatic dissemination of rab31 overexpressing MDA-MB-231 breast cancer cells to the lung.
  
  
  CONCLUSIONS
  Overexpression of rab31 in breast cancer cells leads to a switch from an invasive to a proliferative phenotype as indicated by an increased cell proliferation, reduced adhesion and invasion in vitro, and a reduced capacity to form lung metastases in vivo.
authors.affiliation: Clinical Research Unit, Department of Obstetrics and Gynecology, Technical University of Munich, Ismaninger Str, 22, Munich 81675, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Grismayer
authors.forename: Susanne
authors.initials: S
authors.lastname: Sölch
authors.forename: Bastian
authors.initials: B
authors.lastname: Seubert
authors.forename: Thomas
authors.initials: T
authors.lastname: Kirchner
authors.forename: Sonja
authors.initials: S
authors.lastname: Schäfer
authors.forename: Gustavo
authors.initials: G
authors.lastname: Baretton
authors.forename: Manfred
authors.initials: M
authors.lastname: Schmitt
authors.forename: Thomas
authors.initials: T
authors.lastname: Luther
authors.forename: Achim
authors.initials: A
authors.lastname: Krüger
authors.forename: Matthias
authors.initials: M
authors.lastname: Kotzsch
authors.forename: Viktor
authors.initials: V
authors.lastname: Magdolen
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D004195:Disease Models, Animal; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D014183:Transplantation, Heterologous; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism
chemical_list: D000906:Antibodies; D016326:Extracellular Matrix Proteins; C484190:RAB31 protein, human; D020691:rab GTP-Binding Proteins