Expression of the 11p13 Wilms' tumor gene, WT1, correlates with histologic category of Wilms' tumor.

Homozygous inactivation of WT1, a Wilms' tumor gene located on chromosome 11 at p13, is believed to predispose to Wilms' tumor and therefore may be a common occurrence in this cancer. The expression of this gene in primary Wilms' tumors was examined by northern and quantitative RNA slot blot analysis and compared with clinical, histologic, and molecular features of each case. The characteristic 3.2 kb RNA was readily detected in most primary tumors although there was marked variation in the level of WT1-specific transcripts. No abnormal-sized RNA products were detected and expression of WT1 was not coordinated with that of several other oncofetal genes: N-myc, insulinlike growth factor 2 (IGF-2), and c-myc. The relative abundance of WT1-specific RNA did correlate with the histologic category of Wilms' tumor such that those tumors with heterologous differentiation have, in general, lower relative levels of WT1 transcripts than those tumors without heterologous differentiation. These results further establish the heterogeneity of Wilms' tumor with respect to the expression of tumor-associated oncofetal genes and suggest a relationship between WT1 expression and cellular differentiation.