TABLE 1.
Effect of cytostatic drugs on rRNA synthesis and nucleolar integrity
Substances are divided into nine classes. The mode and the efficiency of rRNA synthesis inhibition are depicted together with the potential of drug-mediated nucleolar phenotype induction. Transcription: inhibition of the 47 S rRNA; early processing: inhibition of 32 S rRNA precursor; late processing: inhibition of mature 28 S and 18 S rRNA. “Caps,” “spots,” and “necklace” indicate nucleolar protein translocation phenotypes. The inhibitory effect of drugs on rRNA synthesis was rated as follows: (−) little or no effect <50%; (+) 50–90% inhibition; (++) >90% inhibition; (+++) >90% inhibition occurs with 4 or less doublings of concentrations. The concentrations relevant to inhibit rRNA synthesis with 50 and 80% (IC50/IC80) efficiency are shown and compared to the mean clinical concentrations applied per kg body mass, roughly calculated as described under “Experimental Procedures.”
