Studying EMT in Breast Cancer
In addition to global proteomic screening strategies, protein profiling also encompasses more focused and informed experimental strategies. Epithelial to mesenchymal transition (EMT) refers to the process by which epithelial cells lose their cell-cell junctions, exhibit spindle cell morphology, and acquire increased cellular motility.
In breast cancer, EMT facilitates invasion of surrounding tissues and correlates closely with cancer invasiveness, metastasis, and relapse. A group led by Randolph Elble, Ph.D., of Southern Illinois University’s School of Medicine is focusing on the role played in EMT by members of the hCLCA family of calcium-activated chloride channel regulators.
In addition to the role suggested by their name, these proteins also function as secreted metalloproteinases, and their loss indicates an increased risk of metastasis. “Our studies were based on observations of apparent EMT in knockdown cell lines,” he explained.
“To determine whether attenuation of CLCA2 and 4 really caused EMT, we assessed expression levels of proteins associated with epithelial or mesenchymal phenotypes by Western blot.”
The transition from epithelial to mesenchymal phenotype takes about two weeks following knockdown of CLCA2 or 4, and can be confirmed by observing delocalization of E-cadherin from cell-cell junctions. “We could quantify proteins over a wide range of expression using a Li-Cor Odyssey fluorescent scanner,” said Dr. Elble.
The group found that loss of these proteins is associated with transition to a mesenchymal phenotype in breast cancer, raising an inherent paradox: “Most metalloproteases promote the very processes that CLCA2 and 4 inhibit,” Dr. Elble pointed out.
He anticipates that the work may have considerable clinical payoff. “Clinically, we found that the loss of CLCA2 expression in primary breast tumors presages a greater risk of metastasis, and we are currently investigating the therapeutic potential of the secreted form of the protease.”