[Increased anti-tumor activity of chemotherapeutic agents combined with direct current against murine transplanted tumors].

The antitumor activity of direct current was studied in mice which were transplanted fibrosarcoma (FSa) into the right thigh. Mice were inserted electrodes into tumor and normal tissue surrounding the tumor, and treated with constant current. The direct current therapy (D.C.T.) (0.6 mA, 120 min) alone was effective to regress tumor, but tumor was not eradicated by D.C.T. alone. Cyclophosphamide (CPA, 100 mg/kg) could markedly reduce the FSa tumor size, but all tumor regrew finally. When D.C.T. was combined with CPA (100 mg/kg), the therapeutic response of FSa tumor was enhanced in mice which were inserted cathode into tumor. For example, in mice receiving direct current (0.6 mA, 120 minutes), the cure rate was 70% compared with 30% by the anode in tumor. Using cure rate assay, D.C.T. and about half dose of CPA could give the similar treatment results as the full dose of CPA alone. That is, D.C.T. will be able to reduce the dose of chemotherapeutic agents. Combination of D.C.T. and doxorubicin was not so effective as CPA, but showed the similar results. The experimental results suggest that D.C.T. alters the drug distribution in the tumor and makes the drugs more effective.