Validation of bioluminescence imaging of colorectal liver metastases in the mouse

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carcinoma (CRC) cells in the liver, tumor growth is routinely measured by determining the area of liver tissue that has been replaced by tumor tissue (hepatic replacement area [HRA]).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. 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. 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. 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.