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Membrane association and shedding of the GPI‐anchored Ca‐MOv18 antigen in human ovary carcinoma cells
Author(s) -
Miotti S.,
Alberti S.,
Facheris P.,
Mantovani L.,
Fornaro Mara,
Stella Manuela,
Ménard S.,
Canevari S.,
Colnaghi M. I.
Publication year - 1992
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910510326
Subject(s) - antigen , biology , monoclonal antibody , microbiology and biotechnology , phospholipase c , cell culture , radioimmunoassay , ovarian carcinoma , immunofluorescence , chinese hamster ovary cell , biochemistry , antibody , ovarian cancer , receptor , immunology , cancer , genetics
The antigen recognized by the MOvl8 MAb (Ca‐MOvl8) was recently shown to be a glycosylphosphatidylinositol (GPI)‐linked protein. In this report we show that GPI‐anchorage is not limited to IGROVI cells nor to other ovary carcinoma cell lines, but Ca‐MOvl8 was also found to be sensitive to phosphatidylinositol‐specific phospholipase C (PI‐PLC) treatment on fresh ovarian cancer cells. Furthermore, we found a heterogeneous sensitivity of Ca‐MOv18 to PI‐PLC cleavage, not only among the different cells studied but also in different experiments performed on the same cell line, during extended periods of time in culture. Sensitivity to PI‐PLC cleavage was determined by immunofluorescence on live cells and by double‐determinant radioimmunoassay of the antigen released in the supernatant. The specificity of the PI‐PLC cleavage was demonstrated as follows: (a) TX114 solubilized Ca‐MOv18 shifts from the detergent to the aqueous phase after treatment with PI‐PLC; (b) on membrane preparations, PI‐PLC specifically released a fraction of the antigen, which is distinct from the weakly associated form released by high‐salt treatment; (c) Ca‐MOvI8 from IGROVI expressed the cross‐reacting determinant (CRD), which is characteristic of GPI‐linked molecules. The absence of CRD expression on the spontaneously released protein and the possibility of artificially inducing antigen shedding during the resynthesis of Ca‐MOvI8 which follows bacterial PI‐PLC treatment are interesting points which need to be further investigated in order to understand the physiology of the Ca‐MOvI8 tumor antigen.