The EGFR protein expression and the gene copy number changes in renal cell carcinomas

Background: The epidermal growth factor receptor (EGFR) is known to be involved in many tumor promoting activities. EGFR inhibition has been tried as a therapeutic modality in many human malignancies. Methods: The expression of EGFR protein and the gene copy number changes were studied in 135 clear cell carcinomas and 16 papillary renal cell carcinomas (RCCs), and these tumors were diagnosed between 1995 and 1997. Results: An EGFR protein expression (2+ and 3+) was found in 54.1% of the clear cell RCCs and in 43.8% of the papillary RCCs. In the clear cell RCCs, its expression was associated with male gender, the tumor size (≥4 cm) and high T stages (T2 and T3), with statistical significance. Trisomy and polysomy of the EGFR gene were found in 27 (25.7%) and 40 (38.1%) of 105 clear cell RCCs, respectively. Trisomy and polysomy were correlated with an EGFR protein expression and a high clinical T stage, with statistical significance. Among 15 papillary RCCs, 13 tumors showed trisomy (86.7%) and one showed polysomy (6.7%). Amplification was not found in both the clear cell and papillary type RCCs. Conclusions: A considerable numbers of RCCs showed an overexpression of EGFR protein and increased EGFR gene copy numbers, yet the clinical significance of conducting a FISH study in RCC patients seems to be limited.