[Effects of cisplatin, carboplatin, etoposide and human hepatocyte growth factor on the colony formation of four human liver cancer cell lines]

Antitumor activity of cisplatin, carboplatin, etoposide, or human hepatocyte growth factor (hHGF), was compared by examining the colony formation ability of four liver cancer cell lines (PLC/PRF/5 and HuH-7, hepatocellular carcinoma; HuH-6 and HepG2, hepatoblastoma). Antitumor activity was evaluated from the drug concentration causing 50% cell death by a colony assay. PLC/PRF/5 cells were most effectively killed by cisplatin and etoposide, HuH-7 cells by cisplatin and carboplatin, HuH-6 cells by etoposide, and Hep G2 cells by cisplatin. These results indicate that among four liver cancer cell lines, the three were the most sensitive to cisplatin, the two were to etoposide and the only one cell line was to carboplatin. There was no significant relationship between each drug and types of liver cancer. Combined treatment with cisplatin (0.01-1.0 microgram/ml) and etoposide (0.1 microgram/ml) showed synergistic cytotoxic effects on the colony formation of PLC/PRF/5 cells, while combination of carboplatin (0.01-0.1 microgram/ml) and etoposide (0.1 microgram/ml) caused subadditive cytotoxic effects. hHGF stimulated the colony formation of HuH-6 cells, while it inhibited that of Hep G2 cells. The treatment of HuH-6 with cisplatin and hHGF showed a higher cell survival percentage compared with the treatment with cisplatin alone. On the other hand, cell survival of Hep G2 cells was remarkably decreased by the combined treatment with cisplatin and hHGF.

Establishment and characterization of a SV40 T-antigen immortalized epithelial-like cell line derived from the newborn rat colorectum and its malignant transformation by the ras oncogene

Epithelial-like cells from the colorectum of one-day-old newborn rats were immortalized by transfection with the simian virus 40 (SV40) T-antigen gene, and a cell line OUMS-25 was established. The cells were positive for the SV40 T-antigen, and immunoreactive to a colonic epithelial cell monoclonal antibody and a keratin-18 monoclonal antibody. Ultrastructural studies revealed the presence of microvilli on the cell surface and desmosomes between the adjacent cells. Karyotypic analysis showed that OUMS-25 cells were aneuploid. Cloning efficiency of the cells was 0.01% in soft agar. However, the cells were not tumorigenic in the syngeneic newborn rats. The cells were further transformed by transfection with the cloned activated c-Ha-ras oncogene containing a point mutation within codon 61. Characteristics of the activated-c-Ha-ras transfected cells (OUMS-25/RAS) were different in some respects from those of the parent cells (OUMS-25). OUMS-25/RAS cells demonstrated more malignant morphology, elevated cloning efficiency in soft agar, and tumorigenicity. This is the first report on the immortalization and malignant transformation of colorectal epithelial-like cells by transfection with a combination of SV40 T-antigen gene and cloned activated c-Ha-ras oncogene.

Immortalization of epithelial-like cells from human liver tissue with SV40 T-antigen gene

The cells derived from the human embryo liver tissue were transfected with a plasmid pSV3neo containing both the large and small T-antigen gene of the early region of simian virus 40 (SV40), and two cell strains, OUMS-21 and -22, were obtained. OUMS-22 cells, to date, have reached over 100 population doublings through a culture crisis and are considered to have become an immortal cell line. However, OUMS-21 cells failed to become an immortal cell line. Both OUMS-21 and -22 cells were SV40 T-antigen-positive, epithelial-like, and immunoreactive against an anti-keratin 18 monoclonal antibody but against neither an anti-vimentin nor an anti-von Willebrandt factor VIII monoclonal antibody. The staining pattern of cytokeratin in these cells was similar to that in the differentiated human hepatoblastoma and hepatocellular carcinoma cell lines but not to that in the human cholangiocellular carcinoma cell lines. OUMS-21 and -22 cells expressed neither alpha-fetoprotein nor albumin mRNAs. These cells showed no tyrosine aminotransferase activity. However, both OUMS-21 and -22 cells were sensitive to cytotoxicity of aflatoxin B1, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, and benzo[a]pyrene, whereas human embryo lung fibroblasts were insensitive to the cytotoxicity of these carcinogens. These findings suggest that OUMS-21 and -22 cells may arise from undifferentiated liver stem cells or from hepatocytes that lost their ability to express the liver-specific functions prior to immortalization. Both OUMS-21 and -22 cells expressed glutathione S-transferase pi (GST-pi) mRNA. The expression of GST-pi mRNA highly increased in OUMS-22 cells with their immortalization. Karyotypic analysis showed that numerical and structural aberrations of the chromosomes were profound, but neither specific events nor marker chromosomes were found in OUMS-21 and -22 cells. Both OUMS-21 and -22 cells could grow in soft agar, but they were not tumorigenic when transplanted into nude mice.

Effects of antioxidants on survival of adult rat hepatocytes under various oxygen tensions in serum-free primary culture

Effects of antioxidants, such as superoxide dismutase, vitamin C, vitamin E, 4-(0-benzylphenoxy)-N-methylbutylamine hydrochloride (bifemelane), and selenite on survival of adult rat hepatocytes were examined under normoxic and hyperoxic conditions in serum-free primary culture. The tested antioxidants, except for vitamin C, significantly increased the survival rate of hepatocytes under the normoxic condition (under air). Thus, even the normoxic culture condition is hyperoxic for hepatocytes. Elevation of oxygen tension (40% O2) caused severe morphologic degeneration of hepatocytes and remarkable decrease in the survival rate of the cells. Addition of the antioxidants effectively protected hepatocytes from the morphologic degeneration, and significantly improved the survival of the cells under the hyperoxic condition. These findings indicate that the antioxidants can maintain the long-term survival of hepatocytes in serum-free primary culture.