Visualization of Early Events in Tumor Formation of Egfp–Transfected Rat Colon Cancer Cells in Liver

Abstract

Colon cancer preferentially metastasizes to the liver. To determine cellular backgrounds of this preference, we generated an enhanced green fluorescent protein (eGFP)-expressing rat adenocarcinoma cell line (CC531s) that forms metastases in rat liver after administration to the portal vein. Intravital videomicroscopy (IVVM) was used to visualize early events in the development of tumors in livers of live animals from the time of injection of the cancer cells up to 4 days afterward. Based on information obtained with IVVM, tissue areas were selected for further analysis using confocal laser scanning microscopy (CLSM), electron microscopy (EM), and electron tomography. M any types of cancer of the gastrointestinal tract preferentially form metastases in the liver. 1 Metastasis of colon cancer in liver is found in 25% of patients at the time of colorectal resection, whereas 50% of patients eventually develop liver metastases. Approximately 90% of patients who die from colorectal cancer have liver metastases. 2 Metastasis is a multistep and dynamic process. Several steps are considered essential for the formation of metastases. These steps include detachment of cancer cells from the primary tumor, entry into the circulation and exit from the circulation at a secondary site by interactions with endothelial cells, and subsequent extravasation. 3 Completion of all these steps is considered necessary for metastasis.Two processes have been proposed to explain the high incidence of colon cancer metastasis in liver. One explanation is based on the seed-and-soil theory of Paget (1875) in which preferential adhesion of colon cancer cells (homing) forms the basis. 4,5 Alternatively, experimental data have shown that cancer cells cannot pass the liver because they are arrested physically in the too-narrow sinusoids of the liver. [6][7][8] The next steps after cancer cell arrest are also a matter of debate. Extravasation is considered the next step, but experimental data have shown that cancer cells can then either be dormant 8 or form micrometastases in the circulation. 9 Experimental end-point animal models of metastasis allow for quantification of numbers and sizes of metastases 10 but provide little information on processes that are involved in the development of metastases. Early events in metastasis were thus far not easy to study because identification of single cancer cells or micrometastases in tissues was difficult. To enable the analysis of early events in the formation of metastases, cancer cells have been transfected with the Escherichia coli ␤-galactosidase (lacZ) gene, which enables detection of micrometastases in tissue sections [11][12][13] and quantification of cancer cells in tumor tissue homogenates. 14 However, lacZ does not allow direct visualization of cancer cells in live animals, which would help us understand dynamic processes related to invasion and metastasis of cancer. 15 Green fluorescent protein is a suitable heritable marker and has been proven Abbreviations: CLSM, confocal laser scanning microsc...

Structural and functional aspects of the liver and liver sinusoidal cells in relation to colon carcinoma metastasis

“…CC531s, colon carcinoma cells, are able to kill LSECs by usage of Fas/ FasL pathway [94] (Figure 3). In vivo, destruction of the sinusoidal lining can be observed and is also confirmed by others [93][94][95] . However, when CC531s are pre-treated with IFN-, the outcome of apoptosis in cocultures is inversed.…”

Differential effects of anticoagulants on tumor development of mouse cancer cell lines B16, K1735 and CT26 in lung

“…It is likely that all three cell types have been arrested mechanically in the capillaries due to size restriction as was reported by Mook et al for colon cancer cells in rat liver [45]. Such a process cannot be inhibited by Hirudin.…”

Mechanism of the Mesenchymal–Epithelial Transition and Its Relationship with Metastatic Tumor Formation

“…Certainly, the exact reasons for these results remain to be revealed in the future, perhaps by improving the experimental metastasis models. In addition, thanks to recent advances in intravital videomicroscopy techniques, studies are shedding light on numerous critical steps in tumor metastasis (135)(136)(137)(138)(139)(140)(141)(142). Such techniques represent a powerful tool for studying fluorescently labeled proteins within individual tumor cells in animal models.…”