Expression of HER‐2/neu in renal‐cell carcinoma. Correlation with histologic subtypes and differentiation

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Abstract
Twenty‐four renal‐cell carcinomas (RCC) and corresponding non‐neoplastic kidney tissue were examined for amplification and expression of the HER‐2/neu gene. Gene amplification was examined by slot‐blot analysis, mRNA expression by in situ hybridization and Northern blot analysis, and protein expression by immunohistochemistry. Northern‐blot analysis revealed lower expression of HER‐2/neu mRNA in clear‐cell (p < 0.001) and compact (p < 0.001) tumor subtypes, while chromophilic, chromophobic and tubulo‐papillary subtypes did not show significant differences in HER‐2/neu gene expression, as compared with non‐neoplastic kidney tissues. HER‐2/neu gene expression was not significantly associated with tumor stage. Low differentiation (G3) was associated with lower HER‐2/neu gene expression, but the number of G3 cases was too small for statistical analysis. HER‐2/neu gene amplification was not found in any of the tumors. The results of in situ hybridization and immunohistochemistry generally agreed with those of Northernblot analysis. We conclude that HER‐2/neu gene expression correlates with Thoenes' classification of RCC and may be inversely related to tumor differentiation; it is probably not involved in progression of RCC, in contrast to carcinomas of other locations (e.g. breast, ovary).