PTGS2 and cancer: We are motivated to work with lower doses of aspirin ( ≤ 500 mg/ml) under short-term treatment and controlled conditions, as patients under high dosage intakes often incur adverse reactions, such as bleeding.68 In anti-cancer studies, it was shown that low doses of aspirin ( < 500 mg/day) has little or no activity against COX-2,80 an observation that was also reflected in our studies (Fig. 6e).