TUMOR-CELL ARREST IN THE MICROCIRCULATION - LACK OF EVIDENCE FOR A LEUKOCYTE-LIKE ROLLING ADHESIVE INTERACTION WITH VASCULAR ENDOTHELIUM IN-VIVO

Hematogenous spread of tumor cells and metastasis formation in seconda ry organs are insidious aspects of cancer. In the present intravital m icroscopic study in the rabbit mesentery, we examined the in vivo flow behavior of six human tumor cell lines of different histological ari, ain. The tumor cells and human neutrophils were injected locally into a side branch of the superior mesenteric artery upstream of the observ ed microvascular area In the mesentery. None of the tumor cells behave d similar to the leukocytes of which a substantial fraction rolled alo ng the endothelium of small venules. Thus, the tumor cells passed the same venular segments without interacting with the endothelial lining. Yet, three of the tumor cell lilies (HT-29, DLD-1, and HCT-8) were st rongly positive for the oligosaccharides Lewis(x), sialyl-Lewis(x), an d sialyl-Lewis(a) which are recognized by the endothelial selectins th at mediate leukocyte rolling. On the other baud, some tumor cells were trapped in the smallest vessels and remained so throughout the experi mental period, apparently due to a discrepancy in size between tumor c ells and microvessel lumen. Taken together, our in vivo findings sugge st that initial microvascular arrest of metastasizing tumor cells is d ependent primarily on mechanical factors rather than on receptor-media ted leukocyte-like adhesive interactions. (C) 1997 Academic Press.