LE(Y) GLYCOLIPID ACTS AS A COFACTOR FOR TUMOR PROCOAGULANT ACTIVITY

We have generated a monoclonal antibody (MAb), FS01, which inhibits th e procoagulant activity (CCA-1) produced by a human squamous cell carc inoma cell line, LK52. Expression of the antigen recognized by FS01 MA b in various cancer cell lines correlated well with the procoagulant a ctivities of the expressing cell lines. Our objective was to character ize the molecule reacting with FS01 MAb and to analyze its involvement in the CCA-1 procoagulant activity. The molecule was identified as a glycolipid and found to be involved in the procoagulant activity becau se both procoagulant activity and reactivity to FS01 MAb were lost aft er endoglycoceramidase treatment of CCA-1. Furthermore, FS01 MAb recog nized the Lewis Y (Le(y)) antigen. To confirm the involvement of a gly colipid incorporating the Le(y) antigen in the procoagulant activity, we attempted to purify CCA-1 from LK52 culture supernatant. In one of the purification steps, a fraction containing low procoagulant activit y (CCA-1p) separated from the Le(y)-positive fraction (CCA-1c). Althou gh CCA-1c alone did not show procoagulant activity, the procoagulant a ctivity of CCA-1p was augmented by CCA-1c and this augmentation was in hibited by FS01 MAb. Furthermore, CCA-1c enhanced the procoagulant act ivity of 33 cell lines tested as well as CCA-1p. In addition, purified Le(y) glycolipid from canine intestine augmented the procoagulant act ivity of CCA-1p, and this augmentation also could be inhibited by FS01 MAb. We conclude that Le(y) glycolipid is a co-factor for the procoag ulant activity derived from cancer cells. (C) 1997 Wiley-Liss, Inc.