Identification of Breast Cancer Serum Biomarkers: A Novel Retroviral Library Screen to Define the Breast Cancer-Soluble Ectodomain Proteome

We proposed to perform a proteomic screen of a retroviral-expressed human breast cancer cDNA library in an attempt to identify novel secreted or shed proteins as candidate soluble biomarkers in human breast cancer. Although we encountered difficulties in generating a viable cDNA library, we were able to show that C-terminal HA-epitope tagged proteins can be efficiently expressed in human breast cancer cell lines by retroviral gene transfer. In addition, human breast cancer cells have an active ectodomain sheddase machinery and are capable of releasing large amounts of over-expressed protein. Future studies will be done to perfect our retroviral expression vectors and to subclone pre-made cDNA libraries into suitable expression vectors. The original document contains color images.