A comparison of the mechanisms of action of VP-16-213 and podophyllotoxin.

A comparison of the mechanism of action of VP 16-213 and podophyllotoxin has revealed that although both drugs inhibit nucleoside uptake in HeLa cells, they exhibit other biological properties which are quite distinct. Podophyllotoxin inhibits microtubule assembly in vitro while VP-16-213 has no effect in this system. VP-16-213 induces single-stranded breaks in DNA in HeLa cells, an effect which may explain the cytoxicity of VP-16-213. In contrast to VP-16-213-treated cells, cells treated with podophyllotoxin maintain DNA integrity and show no evidence of single-stranded breaks.