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 exhibited an NADH oxidase activity at their external surfaces that was inhibited by the antitumor sulfonylurea, N-(4-methylphenylsulfonyl)-N'-(4-chlorophenyl)urea (LY 181984). Intact HeLa cells (fresh or frozen) also 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. Growth 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 EC(50) for LY181984 was reduced to about 30 nM which now approximated the 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 by isolated vesicles of plasma membranes. The tumor-inactive sulfonylurea N-(methylphenylsulfonyl-N'-(phenyl)urea (LY181985) was ineffective in the inhibition of NADH oxidation and of growth with HeLa cells either in the presence or absence of EGF.