MUC1 and cancer: However, a preliminary experiment revealed that SN-101 interacts with native MUC1 expressed on the surface of cultured cancer cells, HER2 negative human breast cancer OCUB-M cells33 (Fig. 4e), whereas SN-101 shows a weak inhibitory effect on the proliferation of OCUB-M cells (IC50 = 0.6 mg mL−1).