Expression of the retinoblastoma gene product in renal tumors.

BACKGROUND

Alterations in the retinoblastoma (Rb) gene and its protein product have been detected in numerous solid tumor malignancies. Loss of Rb function is believed to contribute to neoplastic transformation or to the development of metastases. To define the role of Rb in renal cancer, we analyzed renal tumor specimens for molecular alterations in the Rb gene and for lack of Rb protein expression, and correlated the results to clinicopathological characteristics.

MATERIALS AND METHODS

Thirteen renal cancer cell lines, 62 primary renal tumors, and 5 metastatic renal cancers were studied by Southern blot analysis for defects in the Rb gene, and by immunohistochemistry for Rb protein expression. Results were correlated with histopathological parameters and patient survival.

RESULTS

Structural alterations in the Rb gene were not detects in any of the renal cancer cell line or primary renal tumors studied. A rearranged Rb gene was observed in 1/5 metastatic tumor specimens. Western blot analyses revealed a truncated Rb protein in one of 13 renal cancer cell lines; immunohistochemical analysis revealed Rb protein in all papillary and oncocytic tumors, and in 39/44 non-papillary tumors. Rb expression patterns did not correlate with pathological stage, histological grade or the development of metastatic disease.

CONCLUSION

Molecular alterations of the Rb gene are infrequent (<2%) in renal cancers, and Rb protein is present in the majority of primary (92%) and metastatic (100%) renal tumors. Loss of Rb expression does not appear to significantly contribute to malignant transformation or progression of renal cancers.