In experiments comparing the expression of tropomyosins in various human breast cancer cell lines with untransformed MCF10A breast epithelial cells we observed that the LC24 antibody that was raised against sequences in the carboxy-terminal domain of the TPM4 gene detected the well-characterized LMW Tpm4 isoform, Tpm4.2, but also a protein with the same mobility as a HMW tropomyosin (Figure 1A). Here, TPM4 is linked to breast carcinoma.