ABSTRACT
Loss of heterozygosity of chromosome 16q occurs in 17-25% of Wilms' tumors. Two cadherin genes mapping to 16q22 were chosen as candidate gens: E-CAD, encoding epithelial cadherin, because it is involved in kidney development and it was recently reported to be a WT1 target; and KSP-CAD because it encodes a kidney-specific cadherin. By RT-PCR analysis in a series of 39 Wilms' tumors, we identified a very low expression of E-CAD and KSP-CAD in 72% and 95% of the tumors, respectively. To ascertain whether down-expression of these genes could be related to WT1 alterations in tumors, we looked for a relationship between WT1 and CAD expression. Our data suggest (i) the existence of alternative mechanisms for regulating E-CAD expression, and (ii) that E-CAD does not belong to the WT1 pathway that is altered in Wilms' tumorigenesis.
Subject(s)
Cadherins/biosynthesis , Kidney Neoplasms/metabolism , WT1 Proteins/biosynthesis , Wilms Tumor/metabolism , Cadherins/genetics , Chromosomes, Human, Pair 16/genetics , Down-Regulation , Gene Expression Regulation, Neoplastic , Humans , Kidney/metabolism , Kidney Neoplasms/genetics , Loss of Heterozygosity , Protein Isoforms , WT1 Proteins/genetics , Wilms Tumor/geneticsABSTRACT
Wilms' tumour (WT) or nephroblastoma is the most frequent kidney cancer in children. In a previous study, we reported alterations to WT1 transcription in 90% of WT tested, with decreased exon 5 +/- isoform ratio being the most frequent alteration (56% of WT). We now report an approach based on cDNA profiling of tumour pools to identify genes likely to be dysregulated in association with a decreased WT1 exon 5 +/- ratio. We compared the expression profiles of pools of tumours classified according to whether this isoform imbalance was present (five tumours) or not (four tumours), using Atlas Cancer cDNA expression arrays. Fourteen of 588 genes tested displayed specific up-regulation (CCND2, PCNA, N-MYC, E2F3, TOP2A, PAK1, DCC and PCDH2) or down-regulation (VEGF, IGFBP5, TIMP3, ARHB, C-FOS and CD9) in the pool of tumours with decreased exon 5 +/- ratio. These results were validated by RT-PCR analysis of four genes (CCND2, PCNA, VEGF and IGFBP5). We extended the analysis of VEGF expression to 51 tumours by real-time RT-PCR and ascertained differential expression of this gene associated with WT1 expression pattern. Moreover, our results suggest that the VEGF expression level may be of prognosis relevance for relapsed patients.
