Tween-80 alters natural resistance of sarcoma-180 to bouvardin (NSC 259968)

Sarcoma-180 tumour (S-180) exhibits natural resistance to bouvardin (NSC 259968), a protein synthesis inhibitor that also inhibits RNA and DNA synthesis when administered over a range of non-toxic doses using 0.9% NaCl as a vehicle. However, using Tween-80 as a vehicle, there is a substantial enhancement of cytotoxicity and a subsequent increase in the life span of animals bearing the S-180 tumour. This observation was substantiated in vitro by exposing S-180 cells to 10(-6)M bouvardin in the presence and absence of Tween-80. Bouvardin, 10(-6)M, in the absence of Tween-80, inhibited the incorporation of [3H]uridine by 46%, whereas the presence of Tween-80 resulted in a 66% inhibition of uridine incorporation.