Imaging EGFR phosphorylation in intact human pancreatic carcinoma cells

Carcinoma of the pancreatic duct is a highly malignant tumor characterized by aggressive and early metastastatic growth. A high rate of tumor recurrence after surgical resection and the lack of effective chemotherapeutic approaches result in low 5-year survival rates. Overexpression of epidermal growth factor (EGF) and its receptor have been correlated to a higher tumor biological aggressiveness. We investigated EGFR RNA and protein expressions in different pancreatic carcinoma cell lines. EGFR phosphorylation was determined using acceptor photobleaching fluorescence resonance energy transfer (FRET). The imaging method allowed determination of receptor phorphorylation in intact cells without external calibration. Significant differences between the cell lines were found in EGFR expression but not in phosphorylation of EGFR without EGF stimulation. After stimulation with EGF, significant differences were found in receptor phorphorylation. EGFR expression did not correlate with EGFR phorphorylation. Since EGFR phosphorylation conveys signal transduction within cells, this molecular imaging method could be useful for the identification of patients with a high level of EGFR phosphorylation within tumor cells and, thus, to select patients for an EGFR-targeted therapy.