Antitumour action of 5,6-dimethylxanthenone-4-acetic acid in rats bearing chemically induced primary mammary tumours

Abstract Purpose To evaluate the antitumour activity of 5,6- dimethylxanthenone-4-acetic acid (DMXAA), a vascular disrupting agent currently under phase II clinical trials in combination with cancer chemotherapy, in rats bearing chemically induced primary mammary tumours. Methods Tumours were induced in female Wistar rats by injection of N-nitroso-N-methylurea at 100 mg/ kg subcutaneously. A clinically relevant single dose of DMXAA (1,800 mg/m2) was given to animals when tumours were measurable. Tumour volume, extent of necrosis and cytokine proWles were measured. Results Compared with the control group, DMXAA treatment signiWcantly delayed tumour doubling time and extended the time from treatment to euthanasia. Four of Wve DMXAA-treated animals showed necrosis involving 3.7-41.2% of the area of the tumour section at 24 h compared with none of four control animals (P < 0.028, Chi-square test). Intratumoural levels of TNFx, IL-6, VEGF and IL-1x were increased 4 h after DMXAA treatment. Conclusions This study shows for the Wrst time that DMXAA has signiWcant in vivo antitumour activity against non-transplanted autochthonous tumours and in a host species other than the mouse.