Wild-type p53 gene-induced morphological changes and growth suppression in hepatoma cells

Sorafenib suppresses the cell cycle and induces the apoptosis of hepatocellular carcinoma cell lines in serum-free media

To suppress the invasion of hepatocellular carcinoma (HCC) cells into surrounding connective tissues during metastasis, we investigated the usefulness of sorafenib. In order to search for model cell lines, cell numbers were counted to reveal cell lines with the potential to proliferate in serum-free media. Cell proliferation and cell motility were analyzed with the MTS and wound assay, respectively. 5-Bromo-2'-deoxyuridine (BrdU) labeling and mitotic and apoptotic indices were analyzed to assess the cell cycle and apoptosis. The expression levels of cyclin D1 and the cleavage of caspase-3 were analyzed by Western blotting. HLF cells exhibited growth in the serum-free medium, while the other cell lines examined did not. Sorafenib suppressed the cell proliferation and motility of the HLF cells in the serum-free media. Both indices of BrdU and mitotic potential decreased and the apoptotic index was increased in the serum-free media with sorafenib, suggesting that the cell cycle was suppressed and apoptosis was induced. The expression levels of cyclin D1 decreased and the cleavage of caspase-3 was noted in the serum-free media with sorafenib. Sorafenib may be suitable for molecular therapy to suppress the metastasis of HCC.

Identification and functional characterization of a novel unspliced transcript variant of HIC-1 in human cancer cells exposed to adverse growth conditions

The wild-type p53 gene has been widely implicated in the regulation of hypermethylated in cancer-1 (HIC-1) transcription, a master growth regulatory gene with multiple promoters and, consequently, multiple alternatively spliced transcripts. We investigated the role of p53 (wild type and mutant, both endogenous and exogenous) in modulating the various HIC-1 transcripts. We discovered a novel unspliced HIC-1 transcript, identified as "f" in leukocytes and in the human cell lines U87MG (wild-type p53), U373MG (mutant p53), MCF-7 (wild-type p53), HeLa (p53 degraded by HPV18-E6 oncoprotein), and Saos-2 (p53 null). This transcript is initiated from a new transcription start site and has an intervening stop codon that would result in a possibly truncated 22-amino-acid polypeptide. When U87MG (wild-type p53) and MCF-7 cells (wild-type p53) were exposed to adverse growth conditions of serum starvation or treated with the chemotherapeutic agent cisplatin, cells underwent apoptosis and cell cycle arrest accompanied by increase in p53 and HIC-1 transcript levels. Although the increase of the HIC-1-spliced transcripts followed the increase of p53, increase in f transcript coincided with declining p53 and HIC-1 transcript and protein levels. Moreover, the levels of HIC-1 f transcript were not induced by exogenously transfected wild-type p53 in p53-mutated U373MG and p53-null Saos-2 cells, unlike the spliced transcripts that code for full-length HIC-1 protein. These findings suggest a working model wherein the status of f transcript, which is not under direct transcriptional control of wild-type p53, may influence the level of HIC-1 protein in cancer cells.