© 2004 Foundation for Promotion of Cancer Research
Immunohistochemical Evaluation of Thymidylate Synthase (TS) and p16INK4a in Advanced Colorectal Cancer: Implication of TS Expression in 5-FU-based Adjuvant Chemotherapy
Departments of 1 Pathology and 2 Surgery, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
For reprints and all correspondence: Shingo Kamoshida, Department of Pathology, Fujita Health University School of Medicine, 1–98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470–1192, Japan. E-mail: skamo{at}fujita-hu.ac.jp
Received May 11, 2004; accepted August 16, 2004
Background: Our previous analyses on the expression of thymidylate synthase (TS) and p16INK4a in colorectal cancer patients administered 5-fluorouracil (5-FU) pre-operatively demonstrated that a high level of TS expression was a predictor of 5-FU resistance, and that the combination of a low level of TS expression and induction of p16INK4a after chemotherapy implicated chemosensitivity. The present study aimed to assess the relationship between the biological behavior of advanced colorectal cancer treated post-operatively by 5-FU-based chemotherapy and the expression of TS and p16INK4a in primary tumors.
Methods: Formalin-fixed, paraffin-embedded specimens from 132 colorectal cancers (Dukes' B, 36 cases; Dukes' C, 60 cases; and Dukes' D, 36 cases) treated by 5-FU post-operatively were immunostained for TS and p16INK4a. Antigenicities were suitably retrieved.
Results: Primary tumors expressing high levels of TS in the Dukes' C group showed a significantly shorter recurrence-free interval (RFI) (P = 0.0002). The overall survival (OS) was shorter in high TS expressors than in low TS expressors (P = 0.001). A high level of TS expression also correlated with advanced Dukes' staging and the severity of nodal metastasis (Dukes' B versus Dukes' D, P = 0.001; Dukes' C versus Dukes' D, P = 0.008; N0 versus N2, P = 0.002; N1 versus N2, P = 0.03). p16INK4a expression was not correlated with the prognosis or clinicopathological features.
Conclusions: Appropriate immunohistochemical evaluation is essentially important. We suggest that, in the Dukes' C group, a 5-FU-based regimen can be chosen as a first-line chemotherapy for low TS expressors. TS-high cancer should be treated with anti-cancer agents acting through different mechanisms. Further research should be conducted on applying TS immunostaining to the treatment strategy.
Key Words: thymidylate synthase • p16INK4a • colorectal cancer • 5-fluorouracil • adjuvant chemotherapy