Relationship between immunohistochemical evaluation of thymidylate synthase and proliferating cell nuclear antigen labeling index in gastrointestinal carcinoma

We undertook this study to clarify the effect of immunohistochemical expression of thymidylate synthase (TS) on proliferative activity of carcinoma lesions in patients with gastrointestinal carcinoma. TS was immunohistochemically evaluated in 53 gastric carcinoma and 51 colorectal carcinoma patients using anti-TS polyclonal antibody. Proliferative activity represented by proliferating cell nuclear antigen (PCNA) labeling index (LI) was also immunohistochemically estimated using monoclonal antibody PC10. Then, the correlation between TS expression and PCNA LI was investigated. Both in gastric and colorectal carcinoma, the PCNA LIs of the high-TS group were significantly higher than those of the low-TS group. In gastric carcinoma, the PCNA LIs of the high-TS group were higher than those of the low-TS group in differentiated adenocarcinoma, in the depth of mucosal and/or submucosal layer, in cases without lymph node metastasis, and notwithstanding lymphatic or venous invasion. In colorectal carcinoma, PCNA LIs of the high-TS group were higher than those of the low-TS group in well differentiated adenocarcinoma, in the depth of serosa, in cases with lymph node metastasis, in cases with lymphatic invasion, and notwithstanding venous invasion. Immunohistochemical expression of TS was correlated with the proliferative activity represented by PCNA LI, but was not identical with PCNA LI.