title: In vivo tumor cell adhesion in the pulmonary microvasculature is exclusively mediated by tumor cell--endothelial cell interaction.
abstract: BACKGROUND
  Metastasis formation is the leading cause of death among colon cancer patients. We established a new in-situ model of in vivo microscopy of the lung to analyse initiating events of metastatic tumor cell adhesion within this typical metastatic target of colon cancer.
  
  
  METHODS
  Anaesthetized CD rats were mechanically ventilated and 106 human HT-29LMM and T84 colon cancer cells were injected intracardially as single cell suspensions. Quantitative in vivo microscopy of the lung was performed in 10 minute intervals for a total of 40 minutes beginning with the time of injection.
  
  
  RESULTS
  After vehicle treatment of HT-29LMM controls 15.2 +/- 5.3; 14.2 +/- 7.5; 11.4 +/- 5.5; and 15.4 +/- 6.5 cells/20 microscopic fields were found adherent within the pulmonary microvasculature in each 10 minute interval. Similar numbers were found after injection of the lung metastasis derived T84 cell line and after treatment of HT-29LMM with unspecific mouse control-IgG. Subsequently, HT-29LMM cells were treated with function blocking antibodies against beta1-, beta4-, and alphav-integrins wich also did not impair tumor cell adhesion in the lung. In contrast, after hydrolization of sialylated glycoproteins on the cells' surface by neuraminidase, we observed impairment of tumor cell adhesion by more than 50% (p < 0.05). The same degree of impairment was achieved by inhibition of P- and L-selectins via animal treatment with fucoidan (p < 0.05) and also by inhibition of the Thomson-Friedenreich (TF)-antigen (p < 0.05).
  
  
  CONCLUSIONS
  These results demonstrate that the initial colon cancer cell adhesion in the capillaries of the lung is predominantly mediated by tumor cell - endothelial cell interactions, possibly supported by platelets. In contrast to reports of earlier studies that metastatic tumor cell adhesion occurs through integrin mediated binding of extracellular matrix proteins in liver, in the lung, the continuously lined endothelium appears to be specifically targeted by circulating tumor cells.
authors.affiliation: Department of General and Visceral Surgery; University Hospital Muenster; Muenster; Germany. Peter.Gassmann@ukmuenster.de
authors.forename: Peter
authors.initials: P
authors.lastname: Gassmann
authors.forename: Mi-Li
authors.initials: ML
authors.lastname: Kang
authors.forename: Soeren T
authors.initials: ST
authors.lastname: Mees
authors.forename: Joerg
authors.initials: J
authors.lastname: Haier
mesh_terms: D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000378:metabolism; D002196:Capillaries / Q000378:metabolism / Q000473:pathology*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology*; D037502:Galectin 3 / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D007983:Lewis Blood Group Antigens / Q000378:metabolism; D008168:Lung / Q000098:blood supply*; D008175:Lung Neoplasms / Q000098:blood supply / Q000378:metabolism / Q000556:secondary*; D008297:Male; D008856:Microscopy, Fluorescence; D009360:Neoplastic Cells, Circulating / Q000378:metabolism / Q000473:pathology*; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial; D013997:Time Factors
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D015815:Cell Adhesion Molecules; D037502:Galectin 3; D016023:Integrins; D007983:Lewis Blood Group Antigens; C016467:Thomsen-Friedenreich antigen