Sialyl Lewis' (sLe(x)) is an important tumor-associated carbohydrate antigen present on the cell surface glycoconjugates involved in leukocyte migration and cancer metastasis. We report the formation of sLe(x) epitope in butyrate-treated human pancreatic adenocarcinoma cells expressing MUCI and core 2 N-acetylglucosaminyltransferase (C2GnT). Butyrate treatment stimulates not only the transgene but also a group of endogenous glycosyltransferase genes involved in the synthesis of sLex. Current finding raises a concern about the proposed use of butyrate as a cancer therapeutic agent. (c) 2007 Elsevier Inc. All rights reserved.