Rapid Colon Carcinoma Cell Adhesion and Extravasation within the Hepatic Microcirculation Is Mediated by Beta1-Integrins but Not Selectins
Abstracts
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Purpose: Organ-specific tumor cell adhesion within the microcirculation of host organs is an important step in the metastatic cascade. Circulating tumor cells have to adhere within the microcirculatory vessels, quickly stabilize their adhesion and probably leave the circulation to avoid toxic effects of hydrodynamic shear forces of circulating blood. Using intravital fluorescence microscopy we investigated tumor cell adhesion within hepatic microcirculation in rats. The role of integrins and selectins was anaylzed during adhesion and extravasation of colon carcinoma cells. Methods: HT-29 (human) and CC531 (rat) colon carcinoma cells were fluorescence labeled by CalceinAM. Single cell suspensions were injected i.a. in Sprague-Dawley rats. Adhesive interactions were observed by intravital fluorescence microscopy at the liver surface for 30 min regarding localization within the vascular tree and the time course of these interactions. Furthermore, effects of inhibition of integrin- and selectin-mediated cell adhesion were investigated. Results: Autofluorescence of liver parenchyma was sufficient for distinction of hepatic sinusoids. Within 2 min after injection first cells adhered to hepatic microvessels. "Rolling" was never observed. 93% of the cells adhered to vessels with a lumen larger the tumor cell diameter leaving remaining vessel lumen after cell adhesion. First cells that had left the microcirculation were found after 5 min. After the 30 min observation period 87% of the cells had migrated into the liver parenchyma. Pretreatment of the carcinoma cells with anti-integrin antibodies resulted in a significant reduction of the numer of adherent cells. In contrast, removal of sialylated selectin ligands by sialidase treatment did not affect these adhesive interactions. Conclusions: Our results demonstrated in an in vivo model that metastatic colon carcinoma cell adhesion to host organs appears to be mediated by specific interactions of adhesion molecules rather than mechnical lodgement of the cells within the microvascular tree. Colon carcinoma cells rapidly migrated into the liver parenchyma after sucessfull adhesion within the sinusoids. Inhibition of integrins, but not selectins resulted in loss of cell adhesion to the vessel wall. |
