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[The role of p21 (wafl/cip1) in human colorectal carcinoma cell apoptosis].

OBJECTIVE
To investigate the role of basal expression p21 and stress-stimulated p21 in preventing apoptosis of human colorectal carcinoma cells DLD1 after treatment of adriamycin, roentgenotherapy and gene therapy of p53.


METHODS
A human colorectal carcinoma cell line DLD1 whose p21 expression can be controlled by isopropyl-beta-D-thiogalactoside (IPTG) was established. The morphology, DNA fragmentation and survival rates of two kinds of DLD1 cells expressing or not expressing p21 were observed after treatment with adriamycin, X-ray and transient transfection of p53. The cells in S stage were incubated with [3H] thymidine so as to examine the relationship between apoptosis and cell cycle.


RESULTS
(1) p21 may be one of the most important stress-stimulated proteins in the cells, which can be induced by the p53-dependent pathway and the p53-independent pathway as well. (2) Basal expression of p21 plays an important antiapoptosis role in carcinoma cells after stress-treatment. In contrast, stress-stimulated p21 plays a minor role in preventing apoptosis.


CONCLUSION
Basal expression of p21 plays a more important antiapoptosis role than stress-stimulated p21 in carcinoma cells.