Cyclin D1 expression and retinoblastoma gene protein (pRB) expression in esophageal squamous cell carcinoma

Purpose: Alterations in the cell cycle regulatory cyclin/retinoblastoma protein (pRB) pathway play a important role in tumor progression in esophageal squamous cell carcinoma (ESCC). In the present study, we evaluated the prognostic significance of the combined analysis of cyclin D1 and pRB in ESCC retrospectively. Methods: Immunoreactivities of cyclin D1 and pRB were evaluated in 148 surgically resected ESCC by use of monoclonal antibodies. Disease-free survival of patients was compared among the four subgroups according to the phenotypes of cyclin D1 and pRB expressions. Results: High immunoreactivities of pRB and cyclin D1 were detected in 64.2% and 40.5% of tumors, respectively. The loss of pRB expression and overexpression of cyclin D1 correlated with short survival. However, these factors were not detected as independently prognostic in multivariate analysis. In 107 surviving patients who underwent curative operation, co-expressed pRB and cyclin D1 (pRB+/cyclin D1+: 29 patients) were correlated with unfavorable prognosis (disease-free 5-year survival rate: 42.7%) and high cancer recurrence rate (44.8%) compared with that of 40 patients with pRB+/cyclin D1- tumors (70.5% and 27.5%). The disease-free 5-year survival rate of patients with pRB+/cyclin D1- tumors was significantly better than that of other groups (P=0.001). However, the disease-free 5-year survival rate of 29 patients with pRB+/cyclin D1+ tumors was equivalent to that of 29 patients with pRB-/cyclin D1- tumors (48.3%), and that of nine patients with pRB-/cyclin D1+ tumors (22.2%, P=0.237). Conclusions: Our results suggest that overexpression of cyclin D1 may suppress pRB function, and that combined analysis of pRB and cyclin D1 may be a useful parameter of patient prognosis in ESCC.