TRANSCRIPTOME 2002: From Functional Genomics to Systems
Identification of Putative Genes Involved in Cell Transformation
Andrei M. Mikheev, Svetlana A. Mikheeva, Vivian Li, Jeffrey Delrow and Helmut Zarbl, Fred Hutchinson Cancer Research Center, Seattle, WA
We previously described the isolation of two independent, non-tumorigenic variants of the HeLa cervical carcinoma cell line following exposure to the mutagen ethylmetansulfonate. Unlike the parental HeLa cells, the HA and HF revertants were unable to form colonies in semi-solid medium and failed to induce subcutaneous tumors upon injection into nude mice. The levels of E6 and E7 DNA, RNA and protein in the revertants were unaltered compared to HeLa cells. The levels of p53 were increased in HA and HF cells due to protein stabilisation. Using cDNA microarray hybridization, we identified genes differentially expressed between the revertants and Hela cells. Among identified genes, we found insulin growth factor binding receptor 3 (IGFBP-3) and Dickkopf-1 (DKK-1) upregulated in both revertants. Ectopic expression of either gene in Hela cells inhibited soft agar growth. Although human papillomavirus ectopic over-expression of E6/E7oncogene decreased IGFBP-3 protein levels in the revertants, IGFBP-3 and DKK -1 mRNA levels were unresponsive to E6/E7 expression. These results suggested that p53 independent activation of the DKK-1 and IGFBP-3 genes contributed to phenotypic reversion of Hela cell transformation. The HeLa revertant model is useful for identification of putative suppressors of cell transformation.
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