[Study of anti-tumor effects of hyperthermia combined with hydralazine on experimental tumor]

We analyzed tumor growth delay in experimental tumors after hyperthermia alone, hydralazine (HDZ) injection alone and the combination of these modalities. We also analyzed the energy parameter (ATP/Pi ratio) obtained by 31P-MRS (magnetic resonance spectroscopy). The purpose of this study was to evaluate the usefulness of 31P-MRS as an index of anti-tumor effect. FM3A tumor cells were transplanted subcutaneously in the hind legs of C3H/He mice. We dipped the tumors into a heated circulating water bath. 31P-MRS was performed with a CSI spectrometer. The anti-tumor effect obtained with HDZ alone was insignificant, but combined treatment with hyperthermia and HDZ had a significant synergistic effect. The ATP/Pi ratios for all groups treated separately with HDZ or hyperthermia were not different from the control, but the ATP/Pi ratio decreased after combined use of these agents. There was a significant correlation between the decrease in ATP/Pi ratio and tumor growth delay. We observed a direct relation between the delay in tumor growth and the decline in ATP/Pi ratio after combined treatment with HDZ and hyperthermia. The ATP/Pi ratio 24 hr after treatment may be useful in predicting the efficacy of the combined use of HDZ and hyperthermia.