Change of ras-transformed NRK-cells back to normal morphology by mycalamides A and B, antitumor agents from a marine sponge.

Mycalamide A and mycalamide B, isolated as antiviral and antitumor agents from a New Zealand sponge of the genus Mycale, converted the morphology of ras-transformed NRK-cells to normal morphology at 10 and 1 ng/ml, respectively. The effect on protein synthesis suggests that these agents converted the morphology by preferentially inhibiting the biosynthesis of p21 protein.