LEUKOCYTE ADHESION IN ANGIOGENIC BLOOD-VESSELS - ROLE OF E-SELECTIN, P-SELECTIN, AND BETA-2 INTEGRIN IN LYMPHOTOXIN-MEDIATED LEUKOCYTE RECRUITMENT IN TUMOR MICROVESSELS

Interaction of circulating leukocytes with tumor microvasculature is a critical event in the recruitment of effector cells into the tumor st roma, We have examined the ability of lymphotoxin (TNF-beta), to stimu late rolling, adhesion, and transmigration of leukocytes in angiogenic blood vessels induced by tumor spheroids of Lewis lung carcinoma (LLC ) implanted in dorsal skinfold chambers of nude mice, In the absence o f cytokine stimulation, circulating leukocytes failed to appreciably i nteract with tumor microvessels (TMV), although significant rolling an d adhesion was observed in normal vessels, However, stimulation with l ymphotoxin (LT) resulted in a rapid increase in the number of fast and slow rolling leukocytes in TMV. Treatment with anti-P-selectin mAb 5H 1 resulted in inhibition of fast rollers alone, while combination trea tment with anti-P-selectin and anti-E-selectin (9A9) mAbs effectively blocked slow rolling of leukocytes, Superfusion of the lymphotoxin-sti mulated neovasculature with leukotriene B4 (LTB4) resulted in stable c ell adhesion followed by emigration of leukocytes into the tumor strom a. LTB4-mediated adhesion and transmigration was significantly inhibit ed by treatment with anti-beta 2 mAb 2E6. These studies delineate a mu ltistep cascade of leukocyte adhesion in TMV and demonstrate that stim ulation of the neovasculature with cytokines and chemoattractants can result in P-and E-selectin-dependent rolling and beta 2-dependent stab le adhesion followed by transmigration into the tumor stroma.