Use of surface-enhanced Raman scattering to quantify EGFR markers uninhibited by cetuximab antibodies.

Epidermal growth factor receptor (EGFR) has been recognized as an important prognostic marker expressed in cancer cells because its activation is associated with key features of cancer including tumor growth, survival, angiogenesis, and metastasis. Cetuximab is the first monoclonal antibody drug that targets EGFR overexpressed in cancer cells. It easily binds to EGFR, thereby down-regulating the receptor, blocking EGFR-mediated tyrosine kinase activity, and inhibiting cellular proliferation. Thus, EGFR-cetuximab binding can be quantified to monitor receptor status and the prognosis of cancer therapy. In this work, we report using SERS imaging to assess the inhibitory effect of cetuximab on EGFR expressed on cancer cells. From SERS mapping images using silica-encapsulated gold nanotags, the localized spatial distribution of EGFR that was not inhibited by cetuximab could be determined. Furthermore, EGFR expression could be accurately quantified through the statistical analysis of surface-enhanced Raman scattering (SERS) spectral data. Our experimental data demonstrate the feasibility of SERS imaging to improve the prognostic efficacy of cetuximab treatment.