The effect of verapamil on the anti-tumour action of mitozantrone and doxorubicin against renal carcinoma cells in vitro.
 Ten renal carcinomas were established in culture and their sensitivity to mitozantrone +/- verapamil, as measured by (75Se) selenomethionine incorporation, was studied.
 The 5 tumours with spread beyond the kidney were those in which sensitivity to mitozantrone was enhanced by verapamil.
 With 4 of the 10 tumours and 1 further carcinoma, similar experiments were performed using doxorubicin.
 This drug was more active, its anti-tumour action being related to concentration.
 Verapamil was more effective in potentiation of doxorubicin and this action increased in proportion to the concentration of verapamil added.
