PT  - JOURNAL ARTICLE
AU  - Tony W. H. Li
AU  - Hui Peng
AU  - Heping Yang
AU  - Steven Kurniawidjaja
AU  - Parizad Panthaki
AU  - Yuhua Zheng
AU  - José M. Mato
AU  - Shelly C. Lu
TI  - <em>S</em>-Adenosylmethionine and Methylthioadenosine Inhibit <em>β</em>-Catenin Signaling by Multiple Mechanisms in Liver and Colon Cancer
AID  - 10.1124/mol.114.095679
DP  - 2015 Jan 01
TA  - Molecular Pharmacology
PG  - 77--86
VI  - 87
IP  - 1
4099  - http://molpharm.aspetjournals.org/content/87/1/77.short
4100  - http://molpharm.aspetjournals.org/content/87/1/77.full
SO  - Mol Pharmacol2015 Jan 01; 87
AB  - S-Adenosylmethionine (SAMe), the principal methyl donor that is available as a nutritional supplement, and its metabolite methylthioadenosine (MTA) exert chemopreventive properties against liver and colon cancer in experimental models. Both agents reduced β-catenin expression on immunohistochemistry in a murine colitis-associated colon cancer model. In this study, we examined the molecular mechanisms involved. SAMe or MTA treatment in the colitis-associated cancer model lowered total β-catenin protein levels by 47 and 78%, respectively. In an orthotopic liver cancer model, increasing SAMe levels by overexpressing methionine adenosyltransferase 1A also reduced total β-catenin levels by 68%. In both cases, lower cyclin D1 and c-Myc expression correlated with lower β-catenin levels. In liver (HepG2) and colon (SW480, HCT116) cancer cells with constitutively active β-catenin signaling, SAMe and MTA treatment inhibited β-catenin activity by excluding it from the nuclear compartment. However, in liver (Huh-7) and colon (RKO) cancer cells expressing wild-type Wnt/β-catenin, SAMe and MTA accelerated β-catenin degradation by a glycogen synthase kinase 3-β–dependent mechanism. Both agents lowered protein kinase B activity, but this was not mediated by inhibiting phosphoinositide 3-kinase. Instead, both agents increased the activity of protein phosphatase 2A, which inactivates protein kinase B. The effect of MTA on lowering β-catenin is direct and not mediated by its conversion to SAMe, as blocking this conversion had no influence. In conclusion, SAMe and MTA inhibit Wnt/β-catenin signaling in colon and liver cancer cells regardless of whether this pathway is aberrantly induced, making them ideal candidates for chemoprevention and/or chemotherapy in these cancers.