WILD-TYPE P53 GENE-INDUCED MORPHOLOGICAL-CHANGES AND GROWTH SUPPRESSION IN HEPATOMA-CELLS

The human hepatocellular carcinoma (HCC) cell line, HLF, expresses onl y mutant-type p53 (mt-p53), which has an amino acid substitution at th e 244th residue from glycine to alanine. HLF cells were transfected wi th wild-type p53 (wt-p53) cDNA construct pC53-SN3, mt-p53 cDNA constru ct pC53-SCX [which differs by a single nucleotide, resulting in alanin e instead of valine at the 143rd residue in p53 (p53-143)], or pCMV-Ne o-Bam, as a control, by a liposome method. After G418 selection? three wt-p53 stable transformants (WT), four mt-p53 transformants (MT), and three control vector transformants (VT) were obtained. We analyzed th e cell growth and morphological changes of these transformants under d ifferent culture conditions [fetal calf serum (FCS). 10%, 1%, and 0%]. Whereas no difference from control in the growth rate and morphology was observed under the 10% FCS conditions, serum starvation induced re markable phenotypical changes in all three WTs, but not in the other t ransformant. Corresponding to these phenotypical changes, the transcri ptional activity of wt-p53 was increased more than nine fold. These re sults indicated that serum starvation would induce wt-p53 biological f unction. which is tightly linked to morphological changes and growth s uppression. To induce these changes, the introduction of the wt-p53 ge ne itself was not sufficient, and additional triggering, i.e., serum s tarvation, was indispensable.