[Characterization of renal cell carcinoma: current topics]

This article reviewed relatively new findings of renal cancer concerning epidemiology, molecular and cytogenic analysis for carcinogenesis, and immunological analysis. In recent years, increasing numbers of renal cancer have been found incidentally by ultrasonography or computerized tomography. These incidental tumors were detected at earlier stages and the prognosis was improved. The incidence of renal cancers detected incidentally by ultrasonic mass survey in a restricted area (incidental cancer) was 0.06%, which is much higher than the incidence of clinical renal cancers. Moreover, the incidence of renal cancers found in Japanese autopsy specimens (latent cancer) was 0.77%, which was extremely high. Moreover, the frequency of cancer multicentricity in kidneys removed for renal cancers was 0.07% by examining 100 kidneys. To investigate the biological characteristics of incidental and latent cancers including multicentric daughter tumors is a key point in determining the surgical indications. Specific oncogenes participating in the carcinogenesis of renal cancer have not been found so far, but c-myc oncogene was overexpressed in renal cancers. The deletion of 3 p chromosome was very often observed in renal cancers. The suppressor gene for carcinogens of renal cancer may be localized in 3p region. Renal cancer produced a transforming growth factor-alpha (TGF-alpha), which bound to epidermal growth factor receptor (EGFR) and upregulated the expression of EGFR and TGF-alpha. The autocrine loop of TGF-alpha and EGFR may stimulate the growth of renal cancer. Renal cancer patients had immunological reactions to autologous tumor cells in their sera, then renal tumors expressed class 1 (individually unique) antigens or class 2 (cancer shared) antigens. Immunological therapy may be useful for renal cancer. Finally, antiproliferative and antitumor effect of interferon alpha in renal cancer correlated reversely with the expression of F 33 antigen, which is expressed only in renal glomerulus and proximal tubule. We could discriminate the responder from the nonresponder for immunotherapy with interferon alpha. These findings could lead to the development of new modalities for renal cancer.