Organspezifische Adhäsion metastatischer humaner Kolonkarzinomzellen in unterschiedlichen Targetorganen in vivo

Abstract

Introduction: The colonisation of different target organs by metastatic tumor cells is a multi-step, non-random process involving tumor cell adhesion within the microcirculation as a rate limiting factor. To determine the adhesion mediating molecules and structures we examined adhesive interactions of human colon carcinoma cells by in vivo microscopy within the microcirculation of liver, lung, and kidney as potential target organs. Materials and methods: Fluorescence labelled single cell suspensions (10⁶ cells/ml) of metastatic human colon carcinoma cells (HT-29 LMM) were intra-cardially injected into male CD-rats (250g). In some experiments cells were treated prior to injection with unspecific mouse IgG, function-blocking anti-integrin antibodies or neuraminidase (1U/ml; 30 min.) to remove all sialylated glycoproteins. Integrin- and sialylated glycoprotein expression was determined by flow-cytometry (FACS). Using in vivo fluorescence microscopy initial adhesive interactions of circulating tumor cells within the microcirculation of potential traget organs were semi-quantitatively evaluated for 30 min. The numbers given are means +/− SD and groups were compared by student’s t-test. Results: Circulating tumor cells could pass the microcirculation of all examined organs without size restricted mechanical arrest. In lung and liver, specific tumor cell adhesion could be observed leaving a remaining vessel lumen. In the kidney no adhesive tumor cells were found. In the liver, anti-β1-integrin (n = 11) and anti-β4-intergin (n = 7) antibodies significantly reduced the number of arrested cells by appox. 50% (p < 0.05–0.001), but neuraminidase treatment inhibited to approx. 20% (p < 0.001) compared to IgG controls. In the lung, anti-integrin-β1 (n = 8) or anti-integrin-β4 (n = 10) antibody treatment did not significantly influence initial tumor cell adhesion. In contrast, neuraminidase (n = 8) significantly reduced metastatic tumor cell adhesion (p < 0.05). Conclusion: As adhesion selectively occurs in organs that are frequently targeted as metastatic sites, cell adhesion represents a rate limiting step for metastases formation of colorectal cancer. While obviously tumor cells can directly adhere to extracellular matrix components via integrins within the hepatic sinusoids, in the lung initial adhesive interaction seems to be exclusively mediated be endothelial selectins binding to sialylated glycoproteins on tumor cells.