Epstein's group measured UNC-45A's effect on myosin and actin activity by comparing the activity observed in cells from a highly metastatic cancer cell line with that seen in cells from the same line in which UNC-45A production had been blocked. The difference was substantial, strongly suggesting that high levels of UNC-45A drove the cells' high rate of proliferation and invasion of other tissues.

Further exploring the details of UNC-45A, the UTMB team discovered that the protein actually exists in two slightly different isoforms, one made up of 944 amino acids and the other of 929 amino acids. While these two isoforms interacted similarly with myosin, the breast cells' protein breakdown apparatus attacked the 944 amino acid-isoform much more vigorously than the 929 amino-acid isoform; as a result, the 929 amino-acid isoform was found in much greater levels.

"In the breast cancer cells, you get a disregulation of the two, because the larger one gets turned over more rapidly than the smaller one, and we can actually see this very dramatically," Epstein said.

Source: University of Texas Medical Branch at Galveston