Functional variations in liver tissue during the implantation process of metastatic tumour cells

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Abstract
We have examined several properties of sinusoidal cells in the unaffected tissue of micrometastasis-containing livers. Tumour cells from either B16 melanoma (B16F10) or Lewis lung carcinoma (LLC) were injected intrasplenically in syngeneic mice and sacrified on the 7th day. Light and scanning electron microscopy (SEM) showed tumour cells in hepatic veins and sinusoids in close contact with endothelial walls and macrophages. Following quantitative analysis of SEM images from sinusoidal walls it was found that endothelial fenestrae from B16F10 or LLC-colonized livers were diffusely reduced both in size and density/Μm2 throughout the sinusoid wall, although especially affected zone 3 segments. Following the intrasplenic injection of 1 Μm fluorescent latex particles 1 h prior to sacrifice of the mice a significant reduction of the latex particle uptake by sinusoidal cells was detected in B16F10-colonized livers (27% of controls) which was in contrast to the significant increase in LLC-colonized mice (180% of controls). Despite the focal character of the tumour cell implantation process, hepatic sinusoidal cells reacted diffusely to metastatic cells. However, over liver acini, endothelial cell changes were mainly expressed in zone 3 while phagocytic properties mainly varied in zone 1 and depending on the tumour type. Although the significance of these sinusoidal changes on metastatic development is unclear, data suggests that “soil” conditions in the liver are different before and after being metastasized by tumour cells.