title: Validation of bioluminescence imaging of colorectal liver metastases in the mouse.
abstract: BACKGROUND
  In mouse models for metastatic growth of colorectal carcinoma (CRC) cells in the liver, tumor growth is routinely measured by determining the area of liver tissue that has been replaced by tumor tissue (hepatic replacement area [HRA]). This technique has several major disadvantages. Modern visualization techniques make it possible to image tumor growth noninvasively. In the present report, we validated bioluminescence imaging of liver metastases by comparing it to standard HRA measurements and liver weight.
  
  
  METHODS
  BALB/c mice received an intrasplenic injection of luciferase-expressing C26 CRC cells and the spleen was subsequently removed. On days 5, 7, 9, and 11 after injection, luciferase activity was measured. After imaging, the mice were sacrificed and the livers was removed, weighed, and fixed. HRA was determined by analyzing liver tissue sections. Comparative trend analyses between luciferase activity, wet liver weight, and HRA were then performed.
  
  
  RESULTS
  Luciferase activity, wet liver weight, and HRA all increased over time. Statistical analyses showed that all three types of measurements display a highly significant degree of correlation.
  
  
  CONCLUSIONS
  The measurement of tumor growth in the liver by imaging luciferase activity correlates well with the standard method of determining the HRA and with the increase in liver weight that results from tumor growth. Given the great advantages of measuring luciferase activity over measuring HRA, we conclude that bioluminescent imaging is a reliable and superior method for measuring experimental CRC growth in the liver.
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Urecht, The Netherlands.
authors.forename: Niels
authors.initials: N
authors.lastname: Smakman
authors.forename: Anton
authors.initials: A
authors.lastname: Martens
authors.forename: Onno
authors.initials: O
authors.lastname: Kranenburg
authors.forename: Inne H M
authors.initials: IH
authors.lastname: Borel Rinkes
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000201:enzymology* / Q000473:pathology / Q000556:secondary*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000201:enzymology / Q000473:pathology*; D007267:Injections; D008099:Liver / Q000201:enzymology / Q000473:pathology; D008113:Liver Neoplasms / Q000201:enzymology* / Q000473:pathology / Q000556:secondary*; D008156:Luciferases / Q000378:metabolism; D008163:Luminescent Measurements; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D009929:Organ Size; D013154:Spleen
chemical_list: D008156:Luciferases