P16 and p27 Immunohistochemical Expression in Colorectal Cancer: Analysis of 128 Patients

ABSTRACT

P16 and p27 are inhibiting proteins of cyclin-dependent kinases (CDKIs) that act in the restriction points of the cellular cycle, and it avoids its progression to DNA verification and repair by the cellular apparatus. This way, there should be, physiologically, an inverse relation between the expression of these proteins and cellular proliferation. However, what is really observed are changeable amounts of p27 in normal and tumor tissues. P16 participation in tumorigenesis is controversial. The expression of p16 and p27 as a prognostic factor in colorectal cancer (CRC) patients is controversial. Objetive: To establish a correlation between p16 and p27 immunohistochemical expressions with clinical and anatomopathological variable from patients with CRC. Material and methods: descriptive and retrospective study, with 128 CRC patients, treated surgically between 2000 and 2004, with available material for immunohistochemical analysis through standardized methods. The association between categorical variables was done using Chi-square, Pearson or Fisher?s Exact tests, and the continuous variables were analyzed by t-Student. Global survival and disease-free period were calculated according to Kaplan-Meier method and the associations through log-rank test. Results: The average follow-up time of patients was 35 months. Positivity of p16 was detected in 100% of cases. Negativity of p27 in 6.3% (n=8) of cases, with a significant association (p30.05) between p27 negative and tumors located in right colon (62.5%, n=5) and mucinous (62.5%, n=5). The average global survival was 54.8 months, and the significant clinical and pathological variables associated to survival were: better for curative surgeries; better for early stages; better for well-differentiated tumors; worse for cases with sanguineous or vascular lymphatic invasion; worse for perineural invasion. Conclusions: p27 negative is more frequent in right colon...