Modulation of mucin synthesis by γ-interferon in human colon adenocarcinoma cells

Objectives: Recombinant human interferon has been shown to enhance the expression of histocompatibility antigens and certain tumor-associated antigens in a variety of carcinoma cell lines. Since many tumor-associated antigens are mucins, we investigated the effect of recombinant human γ-interferon on mucin production and secretion by colon cancer cell lines. Methods: Control and γ-interferon-treated cells were labeled with [³H]glucosamine in DMEM-H16 medium with 5% FCS for 24 h. Analysis was performed by gel filtration on Sepharose CL-4B columns, and the high-molecular-weight glycoprotein eluted at the void volume from the cytosol and medium was counted (expressed as dpm/4 × 10⁶ cells). In another experiment the void volume was compared to concentration curves of standard mucins (expressed as mg/10⁷ cells). Results: γ-Interferon increased mucin synthesis in HT-29 and LIM-6 cells, but not in LS174T and CACO2 cells. In HT-29 and LIM-6 cells, mucin synthesis was induced by γ-interferon in a dose-dependent manner. The percentage of mucin secreted into the medium was also increased. Conclusion: The heterogeneity of response of human colon cancer cell lines to γ-interferon by mucin production may limit the specific role of γ-interferon as a modulator of mucin-type tumor-associated antigens.