Antitumor effect of cisplatin or the combined treatment with Zn(II)PPIX and/or cisplatin in mice transplanted with control or HO-1 overexpressing B16F10 tumors. C57Bl/6 mice were inoculated with 1 × 106 of HO-1 overexpressing (B1) or mock-transfected (B5E) cells. On day 7 after inoculation of tumor cells mice were treated with cisplatin at a dose of 2.5, 5.0 or 7.5 mg/kg administered i.p. [A and B] or with cisplatin (5 mg/kg in a single i.p. injection) and 50 mg/kg of Zn(II)PPIX administered i.p. for 7 consecutive days [C and D]. Graphs show the influence of the treatment on the growth of melanoma in mice. *P < 0.05 (two way Student's t-test) in comparison with controls.