Genetic alterations in nephroblastomas and anti-proliferating effects induced by silencing of the tumor-related genes.

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To investigate how much extent beta-catenin aberration would have positive effect on tumorigenesis of nephroblastomas, normal cDNA of beta-catenin, or various types of mutated sequences were introduced into HEK293 cells derived from the embryonal kidney, and stable clones were established. Three different clones, corresponding to the normal beta-catenin sequence (WT), a point mutation at codon 45 (P45), and an interstitial deletion of the whole exon 3 of the bete-catenin gene (Δ ex3), were selected. Exogenous expressions of the introduced beta-catenins were regulated by administration of doxycycline (DOX) in these cell lines. Subsequent analyses of transcriptional activity using TOPFLASH plasmid system showed that exogenously overexpressed beta-catenins enhanced transcription of the reporter gene regulated through T-cell factor binding site in the WT and P45 cell lines, but not in the Δ ex3. Further investigation, however, failed to show increased cell proliferation in any of these three cell lines, providing no definitive supports to indicate involvement of beta-catenin aberration in the development of nephroblastic tumors.On the other hand, MYCN gene silencing experiment on a neuroblastoma cell line, NB-1, demonstrated suppressed cell proliferation property accompanied by apoptosis and differentiation of the cells. Because the MYCN gene is amplified and overexpressed in NB-1 similar to many other clinical tumors, strategy to silence this gene may lead to a new hopeful therapy