The effect of modifying the culture medium on cell polarity in a human colon carcinoma cell line

The human colonic cancer cell line HT29, when grown in DMEM, forms a morphologically unpolarized cell culture in which the cells are covered with irregular microvilli and devoid of belt zonula occludens type tight junctions. However, by modifying the culture medium and growing the cells in RPMI, a different morphology was obtained. A large number of intracellular luminae appeared and at late confluency 90-95% of cells exhibited an apical brush border after four subsequent passages. Junctional complexes and a well developed zonula occludens were revealed under the apical brush border. Immuno-electron microscopical localization of specific markers, sucrase isomaltase (SI), secretory components (SC) and beta 2 microglobulin (beta 2M) showed that SI was limited to the apical surface, whereas 2M and SC were located at the basolateral surfaces. These results indicate that modification of culture conditions affects the ability of HT29 cells to express epithelial cell polarity.