Membrane association and shedding of the GPI-anchored Ca-MOv18 antigen in human ovary carcinoma cells

S. Miotti, S. Alberti, P. Facheris, L. Mantovani, M. Fornaro, M. Stella, S. Menard, S. Canevari, M. I. Colnaghi

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The antigen recognized by the MOv18 MAb (Ca-MOv18) was recently shown to be a glycosylphosphatidylinositol (GPI)-linked protein. In this report we show that GPI-anchorage is not limited to IGROV1 cells nor to other ovary carcinoma cell lines, but Ca-MOv18 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-MOv18 from IGROV1 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-MOv18 which follows bacterial PL-PLC treatment are interesting points which need to be further investigated in order to understand the physiology of the Ca-MOv18 tumor antigen.

Original languageEnglish
Pages (from-to)499-505
Number of pages7
JournalInternational Journal of Cancer
Issue number3
Publication statusPublished - 1992

ASJC Scopus subject areas

  • Cancer Research
  • Oncology


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