MELANOMA CELL-ADHESION TO INJURED ARTERIOLES - MECHANISMS OF STABILIZED TETHERING

An isolated perfused vessel model was used to examine the mechanisms u nderlying the adhesive interactions between circulating tumor cells an d subendothelial matrix in denuded arterioles. Arterioles ranging from 70 to 100 mu m in diameter were isolated from rat mesentery, transfer red to an isolated vessel chamber, cannulated on both ends with glass micropipettes, and perfused with media containing 10(6) hamster melano ma (RPMI 1856) cells/ml, In a second group of arterioles, the endothel ium was denuded by running 2 mi of air through the vessel lumen, Since the tumor cells did not adhere to the vessel wall when perfused at ph ysiologically relevant shear rates, perfusate flow was stopped and the tumor cells were allowed to settle onto the vessel wall for 20 min, A fter counting the number of tumor cells that settled onto the arteriol ar wall, perfusate flow was re-initiated and unattached cells were was hed away, The number of cells remaining adherent were counted and the percentage of adherent cells (relative to the total number of cells th at settled on to the vessel wall during the period of no-how) were cal culated and compared among different groups, We observed that tumor ce lls are much more adhesive to denuded arterioles than to intact arteri oles. To determine the mechanisms responsible for the adhesive interac tions that become established and stabilized during the period of dow reduction, denuded arterioles were treated with fibronectin antiserum or Arg-Gly-Asp (RGD) peptides, Both treatments significantly reduced t umor cell adhesion to denuded arterioles. In subsequent studies, melan oma cells were treated with a transglutaminase inhibitor, mono-dansylc adaverine (MDC), which reduced the ability of adherent tumor cells to withstand the anti-adhesive effects of a subsequent increase in perfus ate flow rate after the period of no-flow. Our data suggest that tumor cells adhere to fibronectin in the subendothelial matrix in denuded a rterioles by an RGD-dependent mechanism, Moreover, our observations ar e consistent with the concept that a transglutaminase-catalysed reacti on acts to stabilize the adhesive interactions between subendothelial matrix components and melanoma cells during the period of flow stasis such that the cells are able to withstand subsequent substantial incre ases in wall shear rate and remain adherent.