Inhibition by guanidino compounds of the growth of spontaneous mammary tumours in SHN mice

The D-form of lombricine extracted from the earthworm was previously found to inhibit the growth of spontaneous mammary tumours of mice. In the present study, the anti-mammary tumour effects of guanidino compounds, of which structures resembled those of lombricine, i.e., guanidine-sulfate (Guanidine), 2-guanidinoethanol sulfate (2-GEt), 4-guanidino-1-butanol sulfate (4-GBt), guanidinoethylphosphate (GEP). opheline (OPHE) and the L-form of lombricine (L-Lom), were investigated in relation to their structures. In Experiment I, each guanidino compound was suspended in olive oil at the concentration of 0.3 mg/0.05 ml, and was injected subcutaneously for 10 days to SHN mice bearing spontaneous mammary tumours. 2-GEt, GEP, OPHE and L-Lom markedly inhibited mammary tumour growth, but Guanidine and 4-GBt did not. In Experiment II, the two compounds examined, 2-GEt and GEP, also significantly inhibited mammary tumour growth when given in drinking water (0.003%) for 10 days, while the effects were much weaker than those of the injected compounds. These results indicate that the existence and the length of the ethylene group are important to antitumour activity and that the site of the antitumour activity in guanidino compounds is the guanidinoethyl group. These compounds are also suggested to be more effective when administered subcutaneously rather than intragastrically.