MUC1 and malignant colon neoplasm: To investigate the specificity of the recombinant 139H2 antibody for MUC1, we performed immunoblot analysis on lysates of the methotrexate-adapted human colon cancer cell line HT29-MTX, known for its high MUC1 expression, and a MUC1 knockout of the same cell line that was previously described (see Fig 3A) (5).