MUC1 and neoplasm: However, we are not able to confirm the presence of endogenous MUC1-TRIM46-KRTCAP2 isoforms expressed in tumor tissue and in cancer cell lines because (1) most of the commercially available antibodies target the VNTR domain that is lacking in our fusion protein isoforms and (2) the sizes of these fusion protein isoforms are very similar to the various protein isoforms of parental MUC1, making it difficult to conclusively distinguish between the two groups.