Inhibition of tumor growth by COX-2 and IDO inhibitors in vivo . (A) MCF-7 or MCF-7-COX2 (8 × 106) cells mixed with RMF-EG (6 × 106) cells were inoculated into the fourth mammary fat pads of 6-week-old female nude mice. Before inoculation of the cancer cell/fibroblast mixture, all mice were primed with 6 mg/kg of 17β-estradiol twice a week for 3 weeks. Measurement of tumor growth was begun at 4 weeks after injection, and tumor volume was continuously monitored. The difference between the groups was evaluated by repeated measures two-way ANOVA analysis. n.s., no significance. *P < 0.01. (B) After 10 weeks, mice injected with MCF-COX-2 and RMF-EG cells were randomly divided into four groups that received vehicle (DMSO), NS-398 (10 mg/kg), L-1-methy-tryptophan (10 mg/kg), or both inhibitors 5 times per week. Two weeks later, animals were killed, and tumors were isolated from mice.