Intratumoral heterogeneous expression of thymidylate synthase in gastric cancer.

BACKGROUND/AIMS: Thymidylate synthase (TS) is reported to be a predictive factor of survival in gastric cancer patients. Its heterogeneous expression has been observed in various cancerous lesions but has not been assessed intratumorally. The aim of this study was to determine the most pertinent site for investigating intratumoral TS expression for the prediction of survival.

METHODOLOGY

TS staining grade was evaluated at the center (CT), the horizontal edge (HT) and the vertical edge (VT) of the tumor, and TS protein level was determined by ELISA at CT and HT. Proliferating cell nuclear antigen (PCNA) was examined for proliferation markers in all tumor samples.

RESULTS

TS expression at HT and VT was significantly higher than at CT. A positive correlation was observed between TS protein level and PCNA-Labeling Index at HT, but not at CT. The survival rate of the high TS group was poor compared with the low TS group at HT and VT, but not at CT.

CONCLUSIONS

The horizontal edge of the tumor (HT) is the most pertinent site for the evaluation of TS expression in gastric cancer; it could prove especially useful in the presurgical estimation of prognosis through biopsy samples.