Expression of second class of KIP protein p57(KIP2) in human colorectal carcinoma

p57(KIP2), the second class of KIP family protein, is one of the negative r egulators of the cell cycle. To elucidate the role of p57(KIP2) in colorect al normal mucosa and cancer, we examined the expression of p57(KIP2) protei n in 110 pairs of colorectal non-tumor and cancer tissues. Immunohistochemi cal analysis showed that p57(KIP2) was weakly detected in the normal coloni c epithelium and lymph follicles. A unique expression pattern of p57(KIP2) was exclusively noted in the elastic fibers within the walls of relatively large blood vessels (diameter >100 mum). In cancer tissues, p57(KIP2) prote in was localized mainly in nuclei. Using the mean percentage of nuclear p57 (KIP2) expression (25%) as the cut-off value, we divided our cases into tho se with high expression (n= 44, 40%) and low expression (n=66, 60%) of p57( KIP2) among 110 colorectal cancer cases tested. The clinical and pathologic al survey showed a significant correlation between low expression of p57(KI P2) and large tumor size (p <0.05) or the presence of tumors in females (p< 0.01). Survival analysis showed that p57(KIP2) expression did not influence prognosis. RT-PCR analysis was also performed using RNA extracts from 6 co lorectal cancer tissues. When the levels of p57(KIP2) mRNAs were compared w ith expression of p57(KIP2) protein, a clear correlation was found, suggest ing that expression of the p57(KIP2) protein may be regulated at the transc ription level. The present study revealed p57(KIP2) expression in colorecta l cancer and suggests that p57(KlP2),ay not play a central role in the prog ression of colorectal cancer.