Functional properties of WT1.
WT1 encodes a zinc finger transcription factor that is inactivated in a subset of Wilms' tumors. We have recently shown that introduction of wild-type WT1 into a Wilms' tumor-derived cell line, RM1, results in growth suppression, consistent with its function as a tumor suppressor gene. WT1-mediated growth suppression was also observed in other cells derived from embryonal tumors, including two osteosarcoma cell lines, U2OS and Saos-2, notable for the respective presence or absence of wild-type p53. To further characterize the functional properties of WT1, multiple U2OS and Saos-2 cell lines were established, expressing either wild-type WT1 splicing variants or naturally occurring mutants under control of a tightly regulated tetracycline repressable promoter. Induction of WT1 in these cells resulted in programmed cell death. This effect was preferentially mediated by WT1 isoform B (encoding alternative splice I, lacking alternative splice II "KTS"), and it was independent of p53, occurring in both U2OS and Saos-2 cells. WT1-mediated apoptosis was associated with transcriptional repression of the epidermal growth factor receptor (EGFR) and reduced synthesis of endogenous EGFR protein synthesis. Constitutive expression of EGFR abrogated WT1-mediated cell death. We conclude that wild-type WT1 can induce apoptosis in embryonal cancer cells, presumably through the withdrawal of required growth factor survival signals, and that EGFR is a physiological target gene for WT1.
Haber
D A
DA
Harvard Medical School, Charlestown, Massachusetts.
Englert
C
C
Maheswaran
S
S
D017398:Alternative Splicing; D017209:Apoptosis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000502:physiology*; D066246:ErbB Receptors / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D016162:Genes, Wilms Tumor / Q000235:genetics*; D016158:Genes, p53 / Q000235:genetics; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D012516:Osteosarcoma / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D025721:WT1 Proteins; D009396:Wilms Tumor / Q000235:genetics*; D016335:Zinc Fingers / Q000502:physiology*
D004268:DNA-Binding Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025721:WT1 Proteins; D066246:ErbB Receptors