CELL CULTURE STUDY OF PROTEINS THAT BIND T-DARPP
Jonathan Castillo, Jamil Momand.
California State University, Los Angeles, Los Angeles, CA.
Approximately 25% of breast cancers overexpress the human epidermal receptor 2 (HER2/neu), a receptor in the epidermal growth-factor receptor family. Trastuzumab (Herceptin) is a humanized monoclonal antibody which targets the extracellular domain of HER2 growth-factor receptor and is approved to treat patient with HER2-positive metastatic breast cancer. Up to 70% of Her2-positive breast cancers demonstrate a response to Herceptin-based therapies, but resistance almost inevitably arises within a year of the initial response. The protein t-Darpp (tDp) is often overexpressed in resistant breast cancers and confers resistance on naïve cells. Little is known about the mechanism of tDp action. Following the work of others, we seek to determine the binding partners of tDp with the aim to understand the mechanism of the resistance phenotype. A co-immunoprecipitation of HA tagged tDp with 35S-Cys and 35S-Met labeling of SkBr3 cells stably transfected to express tDp.HA was performed. Using an anti-HA and H62 antibody, proteins interacting with tDp were pulled down. Identifying the proteins interacting with tDp will provide insight on its role in the resistance of trastuzumab and could lead to a new target for therapy and/or a biomarker for drug resistance.