title: The role of MMP-1 in breast cancer growth and metastasis to the brain in a xenograft model.
abstract: BACKGROUND
  Brain metastasis is an increasingly common complication for breast cancer patients; approximately 15- 30% of breast cancer patients develop brain metastasis. However, relatively little is known about how these metastases form, and what phenotypes are characteristic of cells with brain metastasizing potential. In this study, we show that the targeted knockdown of MMP-1 in breast cancer cells with enhanced brain metastatic ability not only reduced primary tumor growth, but also significantly inhibited brain metastasis.
  
  
  METHODS
  Two variants of the MDA-MB-231 human breast cancer cell line selected for enhanced ability to form brain metastases in nude mice (231-BR and 231-BR3 cells) were found to express high levels of matrix metalloproteinase-1 (MMP-1). Short hairpin RNA-mediated stable knockdown of MMP-1 in 231-BR and 231-BR3 cells were established to analyze tumorigenic ability and metastatic ability.
  
  
  RESULTS
  Short hairpin RNA-mediated stable knockdown of MMP-1 inhibited the invasive ability of MDA-MB 231 variant cells in vitro, and inhibited breast cancer growth when the cells were injected into the mammary fat pad of nude mice. Reduction of MMP-1 expression significantly attenuated brain metastasis and lung metastasis formation following injection of cells into the left ventricle of the heart and tail vein, respectively. There were significantly fewer proliferating cells in brain metastases of cells with reduced MMP-1 expression. Furthermore, reduced MMP-1 expression was associated with decreased TGFα release and phospho-EGFR expression in 231-BR and BR3 cells.
  
  
  CONCLUSIONS
  Our results show that elevated expression of MMP-1 can promote the local growth and the formation of brain metastases by breast cancer cells.
authors.affiliation: Department of Cancer Biology, The University of Texas, MD, Anderson Cancer Center, Houston, TX 77030, USA. hliu5@mdanderson.org
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.forename: Yukinari
authors.initials: Y
authors.lastname: Kato
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Erzinger
authors.forename: Galina M
authors.initials: GM
authors.lastname: Kiriakova
authors.forename: Yongzhen
authors.initials: Y
authors.lastname: Qian
authors.forename: Diane
authors.initials: D
authors.lastname: Palmieri
authors.forename: Patricia S
authors.initials: PS
authors.lastname: Steeg
authors.forename: Janet E
authors.initials: JE
authors.lastname: Price
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology; D001932:Brain Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000556:secondary*; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000556:secondary; D020781:Matrix Metalloproteinase 1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D016211:Transforming Growth Factor alpha / Q000235:genetics / Q000378:metabolism; D014183:Transplantation, Heterologous
chemical_list: D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors; D020781:Matrix Metalloproteinase 1