Reverse-Phase Protein Microarray (Rppa) Analysis Of Pd-L1 And Growth Factor Receptor Signal Transduction Pathways In Hormone Receptor (Hr)-Positive Primary Breast Cancer Tissue And Correlation With Relapse.

558Background: Despite considerabletreatment advances,resistance to hormone therapy remains a major clinical problem. We correlated the protein levels of multiple tyrosine kinase receptors, signal transduction pathway proteins, and PD-L1 with relapse in HR-positive, HER2-negative breast cancer. Methods: A case-control discovery Reverse-Phase Protein Array (RPPA) analysis of primary tumors from 40 HR-positive, HER2-negative breast cancer patients: 18 patients who had relapsed; and 22 patients who had not relapsed (with a minimum of 2.5 years follow-up) was conducted to evaluate the potential of a 24 analyte panel of total and phosphoproteins to predict for probability of relapse. Analytes evaluated include: PD-L1, total and phosphoproteins for EGFR, HER2, HER3, and AR; and phosphoproteins in the major downstream signaling pathways: Ras/MAPK, AKT/mTOR, and JAK/STAT. Rank sum, ROC, and multianalyte statistical analysis was conducted to correlate the FFPE analyte data with clinical outcome (relapse or not). R...