TYRPHOSTIN AG-1478 PREFERENTIALLY INHIBITS HUMAN GLIOMA-CELLS EXPRESSING TRUNCATED RATHER THAN WILD-TYPE EPIDERMAL GROWTH-FACTOR RECEPTORS

The effects of a new epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, tyrphostin AG 1478, were tested on three related hum an glioma cell lines: U87MG, which expressed endogenous wild-type (wt) EGFR, and two retrovirally infected U87MG cell populations which over expressed either wt (U87MG.wtEGFR) or truncated EGFR (U87MG. Delta EGF R). Although AG 1478 inhibited cell growth, DNA synthesis, EGFR tyrosi ne kinase activity, and receptor autophosphorylation of each cell line in a dose-dependent manner, it was significantly more potent in U87MG .Delta EGFR cells than in the other two cell lines, The increased inhi bitory response of U87MG.Delta EGFR cells was due to a greater sensiti vity of the constitutively autophosphorylated M(r) 140,000 and 155,000 Delta EGFR species to AG 1478. These results suggest that AG 1478 is a relatively specific inhibitor of the Delta EGFR, and this finding ma y have important therapeutic implications since the Delta EGFR occurs frequently in glioblastomas and in breast, lung, and ovarian cancers.