Mucin production by colon cancer cells cultured in serum‐free medium

Although many colon cancer cell lines are available for study, few of them exhibit differentiated properties. When cultured in medium containing fetal bovine serum, WiDr cells (WiDr-FBS) show an undifferentiated phenotype: growth as a multilayer of cells adherent to plastic and lack of polarization, brush border, and mucin vacuoles. In contrast, WiDr cells cultured in a chemically-defined serum-free medium containing insulin, transferrin and selenium (WiDr-ITS) grow as clusters of nonadherent cells with abundant desmosomes and tight junctions, microvilli and electron-lucid vacuoles. As WiDr-FBS cells, WiDr-ITS are not polarized. WiDr-ITS cells show a marked enhancement in mucin synthesis as demonstrated by: periodic acid-Schiff and Alcian blue stains, electron microscopy, immunohistochemistry using monoclonal antibodies (MAbs) reactive with mucin-associated epitopes, immune electron microscopy and immunochemical analysis using Western blots. In comparison with WiDr-FBS cells, WiDr-ITS cells showed strong expression of Tn, sialyl-Tn, blood group A and CEA. When mouse MAbs were used, higher levels of the MUCI gene product were detected in WiDr-ITS than in WiDr-FBS cells. The full spectrum of phenotypic changes was observed after I month of culture in ITS medium, and transfer of WiDr-ITS cells to FBS medium was accompanied by a partial phenotypic reversal, suggesting that these phenotypic changes result from an adaptative--rather than selective--process.