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Clin Cancer Res. 2008 Feb 15;14(4):1059-64. doi: 10.1158/1078-0432.CCR-07-1513.

Thymidylate synthase expression in gastroenteropancreatic and pulmonary neuroendocrine tumors.

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Thoracic Oncology Unit, Pathology Division, Department of Clinical and Biological Sciences, University of Torino, San Luigi Hospital, Torino, Italy.



The predictive role of the quantification of thymidylate synthase (TS) in tumors treated with antifolate drugs, such as 5-fluorouracil (5-FU), has been extensively reported in a variety of human tumors. Neuroendocrine tumors (NET) represent potential targets of antifolate agents, but no data on TS expression level in these tumors are currently available.


A series of 116 NETs were collected, including 58 gastroenteropancreatic (GEP) and 58 lung NETs. In 24 well-differentiated GEP neuroendocrine carcinomas (WD-NEC), a 5-FU-based treatment was given. Total RNA was extracted from microdissected paraffin blocks. TS mRNA quantification was done by real-time PCR, whereas protein expression was evaluated by immunohistochemistry.


By means of both quantification by real-time PCR and immunohistochemistry, a higher TS expression in pulmonary small cell lung cancer and large cell NEC compared with typical and atypical carcinoids was observed (P < 0.01). Similarly, in GEP tumors, a higher TS expression in poorly differentiated carcinomas than both WD-NEC and benign tumors (P < 0.01) was found. In patients with WD-NEC treated with 5-FU, high TS mRNA levels were associated with shorter time to progression (P = 0.002) and overall survival (P = 0.04). This negative prognostic role was confirmed in multivariate analysis adjusting for major prognostic variables (P = 0.01). No association between TS mRNA and survival was observed in WD-NEC patients not receiving 5-FU.


This study, for the first time, (a) reports the differential TS expression in the spectrum of NETs and (b) indicates TS as a possible predictive marker of treatment efficacy in WD-NEC patients treated with 5-FU.

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