A study of MUC1 mucin in tumor progression and immune modulation

by Zimmermann, Gabrielle Lee

Introduction: Mucins are large molecular weight glycoproteins present on the apical surface of normal epithelial ceils. Cancer-associated mucins, such as MUC1, are underglycosyIated and are often present over the entire surface of the cell due to a loss of polarity. These cancer-associated rnucins contain novel epitopes that can be potentially recognized as foreign by the immune system and they have been the focus of many forms of irnmunotherapy. There are many models in the literature to show that human MUCl mucin is imrnunogenic in rnice, but these relied on the rejection of MUCl positive tumors and did not allow the investigation of the role of MUCl in tumor progression. Purpose: The purpose of this thesis research was to establish a relevant tumor mode1 to study the mechanisms of tumor progression and immune modulation by MUC 1. Methods: A murine rnammary adenocarcinorna ceIl line, 410.4, was transfected with a 42 tandem repcat of human MUCl cDNA. The resultant transfectants were sorted by FACS into a high ce11 surface MUCl expresser (GZHi) and a low ce11 surface MUCL expresser (GZLo). The stability and efficacy of these ce11 Iines as a tumor mode1 was then tested by injecting them subcutaneously into different strains of rnice and monitoring himor progression, metastases, survival, ce11 surface MUCl stability, serum MUCl mucin levels and anti-MUCI antibody levels. The ability of either ce11 surface or soluble MUCl mucin to interfere with murine immune responses was tested both in vitro and in vivo using standard CTL, NK, T-ce11 proliferation and IFN-y production assays. Results: GZHi tumors, while stable in vitro, showed a loss of MUCl expression in vivo; the rnice showed longer survival and had negligible semm MUCl rnucin levels. GZLo challenged rnice showed shorter survivd and many showed rapidy incresing serum MUCl mucin levels pnor to death. In vitro,it was shown that soluble MUCl, rather than ce11 surface MUCI, had an effect on inhibiting CTL kiliing of targets as well as decreasing IFN-y production in T ce11 proliferation assays. Conclusions: The GZLo ce11 Iine represents a relevant tumor ce11 to be used in animal models to study the imrnunomodulatory role of MUCl mucin and to evaiuate cancer vaccine candidates.