Cyclin D2, but not cyclin D1, overexpression closely correlates with gastric cancer progression and prognosis.

Expression of cyclins D1 and D2, as well as cyclin-dependent kinase 4 (cdk4), was investigated by means of immunohistochemistry in 455 gastric cancer cases. Additional western blotting was performed for four breast cancer and four gastric cancer cell lines and 35 fresh frozen gastric cancer samples, to confirm the cyclin D1, D2, and cdk4 data. Cyclin D1 was restricted to the nucleus of cancer cells with a few exceptions, whereas cyclin D2 was present in both cell compartments, but predominantly in the cytoplasm. Cdk4 was intermediately expressed. Cyclin D1 was overexpressed in 93 cases (20.4 per cent) and cyclin D2 in 105 (23.0 per cent). In the cyclin D2 cases, this correlated with greater age (p=0.0004), better differentiation (p=0.0023), greater depth of cancer invasion (p=0. 003), the presence of lymph node metastasis (p=0.0014), vascular invasion by cancer cells (p< 0.0001), and poor prognosis (p< 0.0001), while cyclin D1 did not correlate with any of these except age (p=0.00193). Multivariate analysis revealed cyclin D2 overexpression to be an independent prognostic factor, in addition to depth of cancer invasion and lymph node status. Cdk4 overexpression was linked to cyclin D1, but not cyclin D2 overexpression. The results indicate that cyclin D2 up-regulation plays an important role in the progression and prognosis of gastric cancer independently of cdk4, whereas cyclin D1 overexpression does not.