INHIBITION OF NADH OXIDASE ACTIVITY AND GROWTH OF HELA-CELLS BY THE N-(4-METHYLPHENYLSULFONYL)-N'-(4-CHLOROPHENYL)UREA (LY181984) AND RESPONSE TO EPIDERMAL GROWTH-FACTOR

Right side-out plasma membrane vesicles isolated from HeLa cells exhib ited an NADH oxidase activity at their external surfaces that was inhi bited by the antitumor sulfonylurea, N-(4-methylphenylsulfonyl)-N'-(4- chlorophenyl)urea (LY 181984). Intact HeLa cells (fresh or frozen) als o exhibited an NADH oxidase activity at the external cell surface. The inhibition of this activity by LY181984 was enhanced by the addition of epidermal growth factor (EGF). The order of addition was critical. It was necessary that the LY181984 be followed by the EGF. If the EGF was administered first, the response to LY181984 was unaffected by EGF . Binding of [H-3]LY181984 to HeLa cells also was enhanced by EGF. Gro wth experiments with HeLa cells revealed a similar pattern of response to EGF. The EC,, of growth inhibition of LY181984 was about 100 mu M. However, if the LY181984 was followed by addition of 10 nM EGF, the E C(50) for LY181984 was reduced to about 30 nM which now approximated t he previously determined K-d of [H-3]LY181984 binding of 30 nM and the EC(50) of 30 nM for inhibition of NADH oxidase activity by LY181984 b y isolated vesicles of plasma membranes. The tumor-inactive sulfonylur ea N-(methylphenylsulfonyl-N'-(phenyl)urea (LY181985) was ineffective in the inhibition of NADH oxidation and of growth with HeLa cells eith er in the presence or absence of EGF.