ODC1 and malignant colon neoplasm: Although there is a significant reduction in tumor volume in the combination groups, one possible reason might be that Sulindac and NO-Sulindac act on polyamine metabolism in a different manner other than the mechanism of DFMO inhibition of ODC activity, in that previous studies have shown that Sulindac induces SSAT, a gene-encoding enzyme involved in polyamine catabolism and export in colon cancer cells [37].