A survival-stratification model of human colorectal carcinomas with beta-catenin and p27kip1

BACKGROUND: The stabilization and nuclear translocation of beta-catenin are early events in the majority of sporadic colorectal carcinomas (CRC). beta-catenin up-regulates c-Myc and cyclin D1, which antagonize the association of the cyclin-dependent kinase (Cdk) inhibitor, p27(kip1), with Cdk2, thus allowing cell cycle progression through G1 to S-phase. Lack of p27 is a significant predictor of poor survival in a series of 136 CRC specimens. A combination of molecules in the same pathway may be a better prognostic factor. METHODS: The expression of beta-catenin, c-Myc, and cyclin D1 in relation to patients' survival and clinicopathologic parameters in the same series was evaluated by immunohistochemistry. RESULTS: Intense nuclear overexpression of beta-catenin, but not a lack of cell membrane or cytoplasmic expression, is a significant predictor of poor survival by both univariate (P = 0.0029) and multivariate analyses (P = 0.004, risk ratio =3.8), suggesting that beta-catenin is retained in the nucleus to function as an oncogene. None of the patients with high nuclear beta-catenin and low p27 expression survived 5 years or more whereas 65% of patients with all other combinations of the two markers survived (P < 0.0001). This combination is also a significant and independent prognostic factor (P = 0.001; risk ratio = 9.7). Overexpression of c-Myc is associated with higher mortality rates, but the expression of cyclin D1 has no prognostic significance. CONCLUSIONS: The combined expression of beta-catenin and p27 can stratify patients into markedly different survival groups, possibly via their antagonistic effects on metastasis promotion.