The proposed trial shall address whether Naproxen, a nonsteroidal anti-inflammatory agent in widespread clinical use primarily for the treatment of pain and inflammation, can safely and effectively be given in a once daily dose to subjects at risk for a mismatch repair deficient colon carcinoma, and how and whether it modulates a series of biomarkers and other parameters in this specific population. The trial shall be performed at the MD Anderson Cancer Center, the Dana Farber Cancer Center and the University of Michigan. All three institutions shall participate in the various aspects of the trial.