Sulindac inhibits colorectal tumour growth, but not prostaglandin synthesis in the rat

We have determined the dose-response relationship between sulindac administ ration and inhibition of tumour growth in the rat. The effect of tumour-inh ibiting doses of sulindac on the production of prostaglandin E in rumours a nd macroscopically normal colon was then examined. Growth of pre-existing t umours was significantly reduced following administration of sulindac at 0. 1 (P = 0.004), 1 (P = 0.01), 3 (P < 0.001) and 10 mg/kg b.d. (P = 0.002) fo r 4 weeks. There was no significant difference in prostaglandin E synthesis between tumours from control rats and those treated with sulindac at eithe r 3 or 10 mg/kg b.d. (P = 0.09 and 0.4, respectively). Prostaglandin E synt hesis was reduced by 33 and 32% in macroscopically normal tissue from these treatment groups. These data show that sulindac inhibits tumour growth at low doses and do nor support a role for the inhibition of prostaglandin syn thesis, by sulindac, in the inhibition of tumour growth.