[Relationship between expression of p27 and DNA ploidy in colorectal carcinoma]

Cell cycle regulation changes in most of tumors. We can regard tumors as a kind of cell cycle diseases. p27 protein is a main negative cell cycle regulator, meantime it is an important prognosis factor of tumors. The significance of reduced expression and altered sbucelluar localization of p27 protein is unclear in progression of colorectal carcinoma. The relevance of p27 protein and DNA ploidy hasn't been reported in colorectal carcinoma. The study was designed to investigate the relationship between the expression of p27 protein and clinicopathological features, DNA ploidy in colorectal carcinoma.

The expression of p27 was observed in 40 colorectal cancer cases using immunohistochemical technique, and DNA content of cancer cells was analyzed using DNA imaging analysis system.

The high p27 expression rate was 62.5% (25/40), while low expression rate was 37.5% (15/40). Low p27 expression was significantly associated with low tumor grade. (P < 0.05). In addition to nuclear staining, 32.5% (13/40) of the carcinoma displayed p27-positive immunoreactivity in cytoplasm. Cytoplasmic localization of p27 was association with late Dukes stage(P < 0.01) and high incidence of lymph node metastases(P < 0.05). The detective rate of polyploidy cell in the patients with p27 lower expression (22.2 +/- 11.3%) was significantly higher than that with p27 higher expression (8.0 +/- 7.7%, P < 0.001).

Reduced expression and altered subcellular localization of p27 play a role in progression of colorectal carcinoma; one suppression tumor mechanism of p27 might be to prevent the acquisition of polyploid DNA content in colorectal carcinoma cells.