Antitumour properties of dimethylsulphoxide ruthenium (II) complexes in the Lewis lung carcinoma system

The antitumour effects of some ruthenium (II) complexes were tested in mice bearing the solid metastasizing tumour, Lewis lung carcinoma. The toxicity of trans-RuCl2 (DMSO)4 is 10-fold higher than that of its cis-isomer. Qualitatively the antitumour activity of these two complexes is comparable, although trans-isomer is more potent. Both exhibit only marginal effects on primary tumour growth while significantly lowering lung metastasis formation. The effects of trans-RuCl2 (DMSO)4 on primary tumour depend on the inoculum size, being more pronounced with low tumour inocula; significant antitumour effects can be achieved also by replacing Cl with I in the molecule. trans-RuCl2(DMSO)4 markedly reduces the number of lung metastases and particularly their volume; the reduction is comparable to that obtained with equitoxic treatments of cisplatin. Treatment with trans-RuCl2(DMSO)4 for 10 consecutive days, after surgical amputation of primary tumour, significantly prolongs the survival time of the treated mice; cisplatin, at equitoxic doses, is less effective. These data show that dimethylsulphoxide ruthenium(II) complexes possess a significant antitumour and antimetastatic activity in the Lewis lung system, also exhibiting an interesting therapeutic potential when combined with surgical amputation of the primary tumour.