Cyclin D2 overexpression and lack of p27 correlate positively and cyclin Einversely with a poor prognosis in gastric cancer cases

G1 cyclins and cyclic-dependent kinase (CDK) complexes play important roles in G1 cell cycle transition, and their overexpression is implicated for ne oplasia. The p27 protein (p27) negatively regulates G1 progression by bindi ng to G1 cyclins/CDK complexes and inhibits their activity, resulting in in hibition of entry to the cell cycle. We investigated overexpression of cycl in D1 (CCND1), cyclin D2 (CCND2), cyclin E (CCNE), CDK2, and CDK4, in addit ion to p27, in 260 gastric cancer cases on the basis of Western blots, reve rse transcriptase-polymerase chain reaction Southern blots, and immunohisto chemistry to clarify the roles of these proteins in tumor progression and p rognosis. Examination of 20 cases of fresh cancer and matched normal tissue s demonstrated a clear tendency for increased mRNA synthesis to be more fre quent than expected from protein levels, and a direct correlation between p 27 protein and mRNA was not found. Immunohistochemistry demonstrated 21.5%, 34.2%, 30.4%, 44.2%, and 48.0% positivity for CCND1, CCND2, CCNE, CDK2, an d CDK4, respectively, in the 260 gastric cancer cases. Overexpression of CC ND2 and CDK4 significantly correlated with tumor progression. Moreover, CCN D2 cytoplasmic staining (26.2%) appeared to be strictly linked with progres sion, whereas nuclear staining (7.8%) demonstrated an inverse correlation. Survival curves showed CCND2 (especially cytoplasmic staining) and CDK4 pos itivity to be associated with a poor prognosis and CCNE positivity with a b etter prognosis. Tumors with high p27 labeling indices (LIs) were well diff erentiated, with low levels of invasion and lymph node metastasis. p27-nega tive cases (37.3%) demonstrated a poor prognosis. Multivariate analysis rev ealed positivity for CCND2 and negativity for p27 to be independent prognos tic factors. There were no direct links among CCND2, CCNE, CDK4, and p27. T he results indicate that CCND2 cytoplasmic localization might reflect an im portant physiological role in tumor progression, whereas CCNE overexpressio n correlates with differentiation and a good prognosis, possibly because of accumulation of inactive forms of CCNE-CDK2 complexes. Loss of p27 caused by degradation activity may affect tumor cell growth in the presence of an altered extracellular matrix, facilitating metastasis. Cell-cycle-regulator y proteins appear to work independently.