Expression of Thymidylate Synthase in Non-Small Cell Lung Cancer

ABSTRACT

BACKGROUND: Thymidylate synthase (TS) catalyzes the methylation of deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP), and this is an essential step in DNA biosynthesis. The present investigation was designed to determine the expression of TS in the patients with non-small cell lung cancer (NSCLC) and to assess the possible associations between the TS status and the p53 or proliferative index (PI). METHODS: The archival tumor tissues from 56 previously untreated NSCLC patients were examined by immunohistochemistry for TS, p53 and Ki-67. RESULTS: Forty-one men and 15 women (age range 35 to 79 years, mean age 62 years) were included in this study. The TS expression was high in 40 patients (71.4%) and low in 16 patients (28.6%). The aberrant expression of p53 was detected in 35 patients (62.5%). The mean PI for all the patients was 31.4+/-12.1. The TS-high tumors tended to be more poorly differentiated (p=0.069). The TS expression by a semiquantitative fourscale grading system was significantly correlated with the PIs (p=0.003). No correlation was established between the TS expression and the p53 status (p=0.806) or survival (p=0.951). CONCLUSIONS: TS was not confirmed to be a useful marker for determining the prognosis of NSCLC patients. However, our data suggest that the tumor cells with higher TS expression have a higher proliferative activity.