IMPLANTATION OF HUMAN COLORECTAL-CARCINOMA CELLS IN THE LIVER STUDIEDBY IN-VIVO FLUORESCENCE VIDEOMICROSCOPY

In vivo fluorescence videomicroscopy (IVFM) was used to analyse the be havior of weakly and highly metastatic human colorectal carcinoma (CRC ) cells during implantation in the liver. A highly metastatic human CR C cell line, CX-1, and a weakly metastatic line, Clone A, were double- labeled with rhodamine B isothiocyanate-dextran (Rd-Dx) to locate cell s and with calcein AM to assess cell metabolic activity in an experime ntal metastasis model, Double-labeled CRC cells (2.0 x 10(6)) were inj ected into the spleens of groups of nude mice and the livers observed by IVFM over the next 72 h. CRC cells were implanted within 30 s after injection into either portal venules or the proximal third of hepatic sinusoids. Approximately 0.5% of CRC cells traversed the liver throug h portal-central venous shunts and implanted in the lung. The number o f CX-1 cells in the liver was similar to that of Clone A cells during the first 12 h, However, more CX-1 cells than Clone A cells remained i n the liver at 24 h and were in groups of 8-12 cells whereas only a fe w, single Clone A cells were detected in the liver at 72 h, Not all Cl one A cells are committed to die within 4 h of implantation because ce lls harvested 4 h after hepatic implantation proliferated normally in vitro when removed from the hepatic microenvironment. Since the stress of mechanical deformation during implantation may cause differences i n cell survival, CX-1 and Clone A cells were passed through filters wi th 8 mu m pores in vitro at 10-15 cm of water pressure to recreate the trauma of hepatic implantation. Approximately 50% of both CX-1 and Cl one A cells were lysed. Furthermore, both CRC lines remained metabolic ally active when co-cultivated with liver cells for at least 24 h in v itro. Thus, the difference in metastatic potential between the two CRC lines may reside in their response to the combination of mechanical i mplantation and subsequent growth in the liver parenchyma.