The Effects of Mutant p21 Protein on DNA & Protein Synthesis in the Cultured Colon Cancer Cell Lines

Choi, Hoon; Chang, Suk Kyun

Abstract

PURPOSE
The products of the ras oncogene are proteins of 188 or 189 amino acids and 21,000 molecular weights, termed simply p21 proteins. But the exact roles of c-ras proteins in cell proliferation and differentiation as well as in neoplastic transformation are little understood. The purpose of this study is to investigate the function of the p21 protein to the human colon cancer cell lines according to the exposure time and dosage of p21.
METHODS
The authors divided tumor cell lines into 3 groups as follows; group 1 (control, colon cancer cell lines without administration of p21 or polyclonal antibody), group 2 (administration of p21 with labelling of 3H-thymidine and leucine), group 3 (simultaneous administration of p21 protein and polyclonal antibody with labelling of 3H-thymidine and 3H-leucine). After deciding the most effective dose of p21 protein and culture time with target cells in preliminary studies, the morphologic changes of target cells with administration of p21 protein and the p21 expression and interaction with anti-p21 polyclonal antibody were examined by phase contrast microscopy each other.
RESULTS
The results were obtained as follows: 1. The most effective dose of the p21 with the colon cancer cell in increase uptake of 3H-thymidine and 3H-leucine were 50 ng but there were some differences in culture time of the 3H-leucine; 96 hours in SBA-1, 72 hours in HT-29 and 120 hours in SW-1116. 2. The increase uptakes of the 3H-thymidine by the different dosage of p21, 50 ng vs 200 ng were 131% (50 ng), 160% (200 ng) in SBA-1, 203% (50 ng), 123% (200 ng) in HT-29, and 127% (50 ng), 189% (200 ng) in SW-1116; and increase uptakes of 3H-leucine were 130% (50 ng), 159% (200 ng) in SBA-1, 113% (50 ng), 165% (200 ng), and 164% (50 ng), 169% (200 ng) in SW-1116. 3. There were some cellular proliferation and morphological changes of the colon cancer cells such as ruffling of the cell membrane, vesicle formation or rounding of the cell after administration of the mutant p21, but such changes were not observed after simultaneous administration of the mutant p21 and anti-p21 polyclonal antibody.
CONCLUSIONS
The role of p21 protein has not been to make manifest wholly. In our study, the p21 protein induce the cell proliferation and morphological changes.