Surface plasmon resonance-biosensor detects the diversity of responses against epidermal growth factor in various carcinoma cell lines

Surface plasmon resonance (SPR) biosensor detects intracellular signaling events as a change of the angle of resonance (AR). We previously reported that the activation of epidermal growth factor receptor (EGFR) on keratinocytes causes a unique triphasic change of AR, whereas the activation of other receptors, such as IgE receptor and adenosine A3 receptor on mast cells, causes a transient monophasic increase of AR. To study the mechanism of AR changes induced by EGFR activation, we introduced wild and mutated EGFR cDNAs into Chinese hamster ovary (CHO) cells and analyzed changes of AR in response to EGF. CHO cells expressing wild-type EGFR showed a triphasic change of AR, whereas cells expressing kinase-dead EGFR (K721M) showed minimum change of AR. A phosphatidylinositol 3-kinase inhibitor, wortmannin, attenuated the third phase of AR change in CHO cells expressing wild-type EGFR. The pattern of AR change was independent on the concentration of EGF. We also analyzed changes of AR with a nontumorigenic keratinocyte cell line, HaCaT, and several cell lines of carcinoma to explore the feasibility of SPR biosensor as a tool for clinical diagnosis. The activation of HaCaT cells and one out of six carcinoma cell lines showed a full triphasic change of AR. In contrast, five out of the six cell lines showed mono- or bi-phasic change of AR. These results suggest that EGF induces the SPR signals via the phosphorylation of EGFR, and provide a possibility that the SPR biosensor could be applied to the real-time detection and diagnosis of malignant tumors.