Detection of epidermal growth factor receptor mRNA in peripheral blood: A new marker of circulating neoplastic cells in bladder cancer patients

Despite the large number of studies performed in solid tumors, few attempts at molecular detection of urothelial cells in blood have been made. Specifically, only uroplakin II (UP-II) and cytokeratin 20 (CK-20) have been suggested as tumor markers in the blood of bladder cancer patients. Epidermal growth factor receptor (EGFR) mRNA expression was found in the blood of patients with some types of carcinoma; nevertheless, its expression has been never investigated in the blood of patients with urothelial tumors. We used a EGFR-based reverse transcription-PCR assay for the detection of tumoral cells in the blood of 27 patients with bladder cancer, in 30 healthy donors, and in 9 patients with cystitis. EGFR expression was compared with that of known markers of circulating epithelial cells, CK-19 and CK-20, and to a urothelial-specific marker, UP-II. Analysis by reverse transcription-PCR and Southern blot hybridization showed no evidence of EGFR and UP-II mRNA expression in any of the samples used as controls. Analysis of healthy donors showed mRNA expression for CK-19 and CK-20 in 6 of 30 and in 4 of 30 samples, respectively. All patients with cystitis resulted negative for EGFR expression, whereas 3 of 9, 2 of 9, and 3 of 9 were found expressing CK-19, CK-20, and UP-II, respectively. Among blood samples from tumoral patients, 74% had EGFR mRNA and 41% had positive signals for CK-19, whereas positivity for CK-20 and UP-II was found in 15% and 37% of patients, respectively. These results seem to indicate that EGFR mRNA in the blood may be a useful tumor marker in bladder cancer patients, as well as in other patients with epithelial tumors.