Continuity of Tumor Microenvironmental Suppression in AOM/DSS Mice by Fucoxanthin May Be Able to Track with Salivary Glycine

Abstract

Background/Aim: Fucoxanthin (Fx) is a potent anticancer carotenoid, demonstrated by mouse cancer models. We recently showed the decrease of salivary glycine could represent an attenuation of tumor microenvironment (TME) formation in an azoxymethane/dextran sodium sulfate (AOM/DSS) colon cancer mouse model. However, it remains unclear whether the salivary glycine is an indicator for continuous TME suppression of Fx in the mice. Materials and Methods: In the present study, we time-dependently analyzed salivary metabolites in AOM/DSS mice, and investigated candidate markers to evaluate the continuous inhibition of colonic TME formation and carcinogenesis in the mice with and without Fx. Results: Fx attenuated the incidence and/or multiplicity of colonic lesions developed in AOM/DSS mice. The number of apoptosis-like cleaved caspase-3high cells was significantly increased, and colonic cancer stem cell-like CD44high/EpCAMhigh cells and cancer-associated fibroblast-like αSMAhigh cells were significantly decreased in colon mucosal tissue by Fx administration. Salivary glycine at 4, 11 and 14 weeks after the final DSS exposure in the Fx-treated mice showed successful and consecutive decreases of 0.5-, 0.4- and 0.7-fold respectively compared to that of control mice. Conclusion: Salivary glycine is a valuable indicator that could evaluate sustained efficacy of cancer chemopreventive effects of Fx in AOM/DSS mice.