EVIDENCE FOR HOMOLOGY OF NORMAL AND NEOPLASTIC HUMAN PLACENTAL ALKALINE-PHOSPHATASES AS DETERMINED BY MONOCLONAL-ANTIBODIES TO THE CANCER-ASSOCIATED ENZYME

  • 1 January 1985
    • journal article
    • research article
    • Vol. 45  (7) , 3268-3273
Abstract
The HeLa TCRC-1 human adenocarcinoma cell line expresses a form of alkaline phosphatase that is similar to the common S-variant of placental alkaline phosphatase (PLAP) on the basis of electrophoretic mobility, catalytic properties and reactivity with polyclonal antibodies. More sensitive probes of changes in protein structure than polyclonal antibodies are monoclonal antibodies (MAb) which recognize individual antigenic sites on molecules. MAb to HeLa TCRC-1 cells were produced and those which bound to the alkaline phosphatase expressed by the cancer cells were selected. Seven MAb were obtained and characterized by (a) fine specificity analysis using allelic variants of PLAP and other human alkaline phosphatase isozymes, (b) Ig isotype, and (c) relative binding affinities to PLAP from 2 sources, placental tissue and HeLa TCRC-1 cells. The 7 MAb bind the enzymes from both sources with equal affinity indicating a high degree of structural homology if not identity the normal S-variant of PLAP and its cancer-associated counterpart. Most of the MAb to cancer cell surface-bound PLAP express either IgG2a or IgG2b heavy-chain isotypes, a higher incidence of these classes of IgG than was observed with the purified and soluble PLAP immunogen which yields MAb predominantly of the IgG1 isotype. Some of these antibodies, like the ones prepared from purified PLAP, recognize differences between allelic variants.