The intracellular accumulation of UDP-N-acetylhexosamines is concomitant with the inability of human colon cancer cells to differentiate.

The relationship between the intracellular concentration of various nucleotides as measured by high-performance liquid chromatography analysis, and the differentiation of 2 human colon cancer cell lines was studied. HT-29 cells were induced to undergo both structural and functional enterocytic differentiation (as determined by electron microscopy and the presence of brush-border specific enzymes, respectively) by changing the carbon source or adding Na butyrate to standard tissue culture media. This differentiation occurred after the cells reached confluency when they were cultured in galactose, uridine, inosine, or without nucleosides (all in the absence of glucose) and in the presence of glucose plus Na butyrate. Cells cultured in 25 mM fructose or glucose +/- nucleosides did not differentiate. In all culture conditions where HT-29 cells did not differentite, the intracellular concentrations of 2 compounds which co-migrated with UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine rose approximately equal to 10-fold at confluency and remained elevated throughout the stationary phase, whereas their concentrations remained constant and low after confluency in cells that underwent differentiation. This indicated that the accumulation of these compounds is associated with the inability of these cells to differentiate since other nucleotides and nucleotide sugars did not change in a similar fashion. Purification of the presumed UDP-N-acetylhexosamines, followed by the identification of the products from their chemical and enzymatic hydrolysis, confirmed the identity of these two peaks. Nucleotide analysis of Caco-2 cells, which undergo enterocytic differentiation after they reach confluency even when cultured on glucose, revealed the same pattern of UDP-N-acetylhexosamine levels as differentiated HT-29 cells, with its concentration remaining relatively constant and very low, even after the cells were confluent. The significance of the accumulation of UDP-N-acetylhexosamines in cells unable to differentiate is discussed.