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1974. 
ADHESION MECHANISMS IN INFLAMMATION AND METASTASIS 
Michael P. Bevilacqua, M.D., Ph.D., Associate Investigator 
Dr. Bevilacqua joined the Howard Hughes Medi- 
cal Institute in the fall of 1991, after moving his 
laboratory from Brigham and Women's Hospital at 
Harvard Medical School to the University of Califor- 
nia, San Diego. Prior to this move, he spent nearly 
eight years studying the role of vascular endothe- 
lium in a variety of pathophysiological processes, 
including inflammation, thrombosis, and tumor cell 
metastasis. His studies on the mechanisms of adhe- 
sion of leukocytes and tumor cells to vascular endo- 
thelium led to the identification of two cytokine- 
inducible endothelial cell surface glycoproteins. 
The first, originally designated endothelial leuko- 
cyte adhesion molecule 1 (ELAM-1), was found to 
support the interaction of neutrophils, monocytes, 
and some lymphocytes with activated vascular endo- 
thelium. Characterization of this molecule revealed 
a type 1 transmembrane protein with an amino- 
terminal lectin-like domain, an epidermal growth 
factor (EGF) repeat, and six complement regula- 
tory-like repeats. Two other molecules cloned con- 
temporaneously with ELAM-1 were found to have a 
similar domain composition, thereby establishing a 
new family, now called selectins. 
The second molecule identified in Dr. Bevilac- 
qua's laboratory was called inducible cell adhe- 
sion molecule 110 (INCAM-110; also known as 
VCAM- 1 ) . INCAM- 110 can suppon the adhesion of 
lymphocytes and monocytes (but not neutrophils) 
as well as nonlymphoid tumor cells, including mela- 
nomas. This molecule is expressed by activated en- 
dothelium and by dendritic cell populations in lym- 
phoid tissues and skin. 
Quantitative Assessment 
of Selectin-Carbohydrate Interactions 
The selectins act in concert with other molecules 
to support adhesion of leukocytes to the blood ves- 
sel wall — a key step in the inflammatory response to 
injury and infection. The term selectin was origi- 
nally proposed to highlight the presence of the lec- 
tin domain and to emphasize the selective nature of 
the expression and function of these molecules. A 
standard nomenclature was agreed on that desig- 
nates each family member according to the cell type 
on which it was originally identified: E-selec- 
tin (previously ELAM-1), endothelium; P-selectin, 
platelets; and L-selectin, leukocytes. 
Dr. Bevilacqua has studied the ability of solution- 
phase synthetic oligosaccharides to block E-, P-, and 
L-selectin-dependent interactions in three assays of 
increasing biological complexity: 1) a competitive 
ELISA involving direct binding of selectin-immuno- 
globulin (selectin-Ig) fusion proteins to carbohy- 
drate-bearing substrates, 2) a cell-protein adhesion 
assay using immobilized selectin-Ig, and 3) a cell- 
cell adhesion assay with cytokine-activated human 
endothelial cells. 
E- and P-selectin-Ig fusion proteins bound to im- 
mobilized bovine serum albumin (BSA)-neoglyco- 
proteins containing sialyl Lewis x (sLe"; Neu5Aca2- 
3Gal^l-4[Fucal-3]GlcNAc) or sialyl Lewis a (sLe^ 
Neu5Aca2-3Gal/3l-3[Fucal-4]GlcNAc) in a Ca^+- 
dependent manner. Solution-phase sLe" tetrasac- 
charide blocked this interaction by 50% at a concen- 
tration ^750 /zM (IC50). With an IC50 ~ 220 ^tM, 
sLe" was approximately threefold more effective. 
Nonsialylated, nonfucosylated derivatives showed 
little or no activity at concentrations up to 1 mM. 
Attachment of an 8-methoxycarbonyloctyl aglycone 
in a /3 linkage to the anomeric carbon of the GlcNAc 
of sLe'' or sLe^ increased their blocking activity 
nearly twofold. In addition, replacement of the 2-A'- 
acetyl substituent of the GlcNAc by an azido or 
amino group resulted in substantial increases in ac- 
tivity, with the most potent inhibitor being amino- 
substituted sLe", which was 36-fold more active 
(IC50 » 2 1 nM) than the reducing tetrasaccharide 
sLe''. In contrast to results obtained with E-selectin- 
Ig, P-selectin-Ig binding to immobilized BSA-sLe* 
24 
