Novel noninvasive marker of regression of clear cell renal cell carcinoma (ccRCC).

Abstract

Objective: Analyzing protein kinase C (PKC) alpha, iota, and zeta as well as levels of Mxi-2 and Vim3 in regressive clear cell renal carcinomas (ccRCCs) and urine samples.

Material and methods: Fresh samples of ccRCCs (predominantly pT1a/b) with different degrees of regression (<10%, 30%, 50%, and 70%) vs normal renal tissue and oncocytomas were studied by Western blot, using antibodies of different PKC isoforms. Urine samples from these tumors were analyzed by ELISA (PKC isoforms, Mxi-2, and Vim3).

Results: With increasing degree of regression beyond 10%, nuclear Mxi-2 and Vim3 were highly overexpressed in fresh tumor samples. In urine samples, Vim3 was significantly overexpressed in oncocytoma and downregulated in RCCs with 70% regression. Western blot analysis shows that PKC alpha and iota levels were significantly increased in fresh tumor tissue samples (tumors with 30% regression). PKC zeta was expressed in normal kidney and significantly increased in oncocytoma but not found in ccRCCs. In patients' urines, Mxi-2 was significantly reduced (regression > 50%), while PKC isoform alpha was significantly increased by advanced regression rate. PKC iota in patients' urine was overexpressed in oncocytoma and reduced in all ccRCC urines.

Conclusion: Tumor regression in ccRCC tissue shows strong nuclear overexpression of Mxi-2, Vim3, and PKC alpha and iota. In respective urines, PKC alpha was overexpressed; PKC iota was decreased. Mxi-2 and Vim3 decreased with increasing regression rates. These reagents could serve as noninvasive ccRCC markers for regression.