Effects of aclacinomycin B on nucleolar ultrastructure and function of RNA synthesis of human gastric cancer cells

The effects of aclacinomycin B (AcM-B) on macromolecule synthesis and nucleolar ultrastructure of human gastric cancer cells were studied by the methods of double-labelled radioactive precursor incorporation with [3H]TdR and [14C]UR as well as observation by electron microscope. AcM-B showed an inhibitory effect on synthesis of DNA and RNA. The inhibition on RNA synthesis was much stronger than that on DNA synthesis. IC50DNA and IC50RNA for AcM-B were 2.38 and 0.16μg/ml, respectively. But IC50DNA and IC50RNA for adriamycin (Adr) were quite close, 3.10 and 2.15μg/ml, respectively. AcM-B induced changes of nucleolar segregation and formation of microspheres, similar to those induced by actinomycin D, but differed from those induced by Adr. These results suggest that AcM-B has a strongly inhibitory effect on synthesis of nucleolar rRNA.