title: Is tail vein injection a relevant breast cancer lung metastasis model?
abstract: BACKGROUND
  TWO MOST COMMONLY USED ANIMAL MODELS FOR STUDYING BREAST CANCER LUNG METASTASIS ARE: lung metastasis after orthotopic implantation of cells into the mammary gland, and lung implantations produced after tail vein (TV) injection of cells. Tail vein injection can produce lung lesions faster, but little has been studied regarding the differences between these tumors, thus, we examined their morphology and gene expression profiles.
  
  
  METHODS
  Syngeneic murine mammary adenocarcinoma, 4T1-luc2 cells, were implanted either subcutaneously (Sq), orthotopically (OS), or injected via TV in Balb/c mice. Genome-wide microarray analyses of cultured 4T1 cells, Sq tumor, OS tumor, lung metastases after OS (LMet), and lung tumors after TV (TVt) were performed 10 days after implantation.
  
  
  RESULTS
  Bioluminescence analysis demonstrated different morphology of metastases between LMet and TVt, confirmed by histology. Gene expression profile of cells were significantly different from tumors, OS, Sq, TVt or LMet (10,350 probe sets; FDR≤1%; P<0.0001). Sq tumors were significantly different than OS tumors (700 probe sets; FDR≤15%; P<0.01), and both tumor types (Sq and OS) were significantly different than LMet (1,247 probe sets; >1.5-fold-change; P<0.01), with no significant difference between TVt and LMet.
  
  
  CONCLUSIONS
  There were significant differences between the gene profiles of cells in culture and OS versus LMet, but there were no differences between LMet versus TVt. Therefore, the lung tumor generated by TVt can be considered genetically similar to those produced after OS, and thus TVt is a relevant model for breast cancer lung metastasis.
authors.affiliation: Division of Surgical Oncology, Department of Surgery, Virginia Commonwealth University School of Medicine, and the Massey Cancer Center Richmond, Virginia, USA.
authors.forename: Omar M
authors.initials: OM
authors.lastname: Rashid
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nagahashi
authors.forename: Suburamaniam
authors.initials: S
authors.lastname: Ramachandran
authors.forename: Catherine I
authors.initials: CI
authors.lastname: Dumur
authors.forename: Julia C
authors.initials: JC
authors.lastname: Schaum
authors.forename: Akimitsu
authors.initials: A
authors.lastname: Yamada
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Aoyagi
authors.forename: Sheldon
authors.initials: S
authors.lastname: Milstien
authors.forename: Sarah
authors.initials: S
authors.lastname: Spiegel
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Takabe
keywords: Breast cancer; animal model; lung metastasis; metastasis model; microarray