S‐adenosyl L‐methionine inhibits azoxymethane‐induced colonic aberrant crypt foci in F344 rats and suppresses human colon cancer Caco‐2 cell growth in 3D culture

Abstract

S-adenosyl L-methionine (SAM) is a universal methyl group donor to various intermediary metabolites, hormones, proteins, neurotransmitters, phospholipids and nucleic acids. Deficiency of folate, which plays a role in the synthesis of SAM leads to increased risk for colon cancer. This study tested the effectiveness of SAM supplementation in protecting against azoxymethane (AOM)-induced colon carcinogenesis in male F344 rats. We also tested the effect of SAM on cyclooxygenase-2 (COX-2) in a macrophage cell line. Further, we developed a 3-D culture model using Caco-2 cells to test the effect of SAM on tumor spheroid size and number. Groups of rats were given the experimental diet containing either 0-, 400- or 800-ppm SAM, 1 week before the first AOM injection and continued until 8 weeks. In the control group, AOM produced a substantial number of aberrant crypt foci (ACF) (96 +/- 8). Dietary administration of SAM significantly reduced the number of total ACF (400 ppm SAM, 68 +/- 7.3, p < 0.01 and 800 ppm SAM, 57 +/- 7.1, p < 0.001). SAM significantly decreased AOM-induced colonic multicrypt foci in a dose-dependent manner. Suppression of Lipopolysaccharide (LPS) induced COX-2 protein expression was observed in a RAW264.7 cell line. We established growth of Caco-2 cells as spheroids, in a 3D matrix of collagen and matrigel. Treatment with SAM decreased both size and number of spheroids in a dose-dependent manner (p < 0.0001). These observations demonstrate for the first time that SAM can reduce the occurrence of ACF in AOM treated male F344 rats and suppress formation of human tumor spheroids and expression of COX-2.