Activity assay of epidermal growth factor receptor tyrosine kinase inhibitors in triple-negative breast cancer cells using peptide-conjugated magnetic beads.

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer with limited treatment options. Epidermal growth factor receptor I (EGFR) has emerged as a promising target in TNBC. Limited success of the EGFR kinase inhibiting small molecules in clinical trials may be attributed in part to inaccuracy in identifying EGFR signatures in patient tumors. In light of the absence of a simple correlation between EGFR expression and its degree of activation, a simple and reliable tool that can quantify EGFR kinase activity in tumor samples may be of therapeutic value in predicting patient-specific EGFR targeted therapies. This study reports the development of an assay that can quantitatively profile EGFR kinase activities and inhibitor sensitivities in TNBC cell lysates by using peptide reporters covalently tethered to magnetic beads in a controlled orientation. The use of magnetic beads provides rapid sample handling and easy product isolation. The potential of this approach was demonstrated by screening a set of five clinically relevant EGFR tyrosine kinase inhibitors. Formatted for microwell plates, this magnetic bead-based kinase assay may be used as a complementary approach for direct high-throughput screening of small molecule inhibitors.