Thymidylate synthase expression and p21(WAF1)/p53 phenotype of colon cancers identify patients who may benefit from 5-fluorouracil based therapy

Abstract

Background: Studies on the expression of thymidylate synthase (TS) in colorectal cancers (CRCs) have failed to provide unequivocal prognostic or predictive information. Here, we assessed the prognostic significance of TS expression in Astler-Coller stage B2 and C CRCs defined by a p21(WAF1)/p53 immunophenotype in patients subjected to 5-fluorouracil (5FU)-based adjuvant therapy.

Methods: A cohort of 189 CRCs was asssessed for TS, p21(WAF1) and p53 expression on tissue microarrays using immunohistochemistry, and associations with disease-free survival (DFS) and overall survival (OS) of the patients were assessed using univariate and multivariate analyses.

Results: TS expression led to the stratification of patients with colon cancer, but not rectal cancer, with immunophenotypes other than p21(WAF1)+/p53- (referred to as P&P) into subgroups characterized by a worse (P&P TS+) and a better (P&P TS-) DFS and OS, in univariate (P = 0.006 and P = 0.005, respectively) and multivariate (P = 0.0004 and P = 0.002, respectively) analyses. The p21(WAF1)+/p53- immunophenotype was associated with a favorable prognosis, irrespective of TS expression.

Conclusions: The strong association observed between the P&P TS+ immunophenotype and a worse DFS and OS suggests a predictive significance of TS expression for 5FU-based adjuvant therapy in patients with colon cancers exhibiting the P&P immunophenotype. In addition, our findings suggest that the appropriate target for assessment of TS expression as a prognostic/predictive marker is a subgroup of colon cancers with an immunophenotype other than p21(WAF1)+/p53-, and that only in this subgroup high TS expression is associated with an unfavorable DFS and OS. Therefore, we suggest that assessing TS expression in conjunction with p21(WAF1)/p53 immunophenotyping of colon cancers may improve the selection of patients suitable for 5FU-based adjuvant chemotherapy.

Fig. 1

p53, TS and p21 immunostaining of representative colorectal cancer cores. a High expression of p53 in nuclei of tumor cells. b Marked fragment of the core from Fig. 1a at high magnification showing p53-positive (brown) nuclei in almost all cancer cells. c Low TS expression (brown) in nuclei of tumor cells. d p21 nuclear expression in tumor cells

Fig. 2

Distribution of p53 histoscores in the study group (n = 189)

Fig. 3

Distribution of TS histoscores in the study group (n = 189)

Fig. 4

DFS of patients with stage B2 + C colorectal carcinomas (n = 189) categorized according to TS expression. TS stratifies patients with P&P immunophenotype (i.e., p21+/p53+, p21-/p53-and p21−/p53+): P&P TS + versus P&P TS-curves, P = 0.02. The P&P TS + curve differs also from other curves, i.e., from the p21+/p53−TS + curve (P = 0.0004) and from the p21+/p53−TS− curve (P = 0.02). TS does not significantly stratifiy patients with a p21+/p53− immunophenotype (P = 0.80). p21 = p21^WAF1

Fig. 5

OS of patients with stage B2 + C colorectal carcinomas (n = 189) categorized according to TS expression. TS stratifies patients with a P&P immunophenotype (i.e., p21+/p53+, p21−/p53− and p21−/p53+): P&P TS + versus P&P TS− curves, P = 0.005. The P&P TS + curve differs also from other curves, i.e., from the p21+/p53-TS + curve (P = 0.0003) and from the p21+/p53−TS− curve (P = 0.05). TS does not significantly stratifiy patients with a p21+/p53− immunophenotype (P = 0.85). p21 = p21^WAF1

Fig. 6

DFS of patients with stage B2 + C colon carcinoma (n = 96) categorized according to TS expression. TS stratifies patients with a P&P immunophenotype (i.e., p21+/p53+, p21−/p53− and p21−/p53+): P&P TS + versus P&P TS− curves, P = 0.006. The P&P TS + curve differs also from other curves, i.e., from the p21+/p53-TS + curve (P = 0.0005) and from the p21+/p53−TS− curve (P = 0.007). TS does not significantly stratifiy patients with a p21+/p53− immunophenotype. p21 = p21^WAF1

Fig. 7

OS of patients with stage B2 + C colon carcinoma (n = 96) categorized according to TS expression. TS stratifies patients with a P&P immunophenotype (i.e., p21+/p53+, p21−/p53− and p21−/p53+): P&P TS + versus P&P TS− curves, P = 0.005. The P&P TS + curve differs also from other curves, i.e., from the p21+/p53-TS + curve (P = 0.005) and from the p21+/p53− TS− curve (P = 0.003). TS does not significantly stratifiy patients with a p21+/p53-immunophenotype. p21 = p21^WAF1

Fig. 8

Schematic algorithm for determining the prognostic significance of nuclear TS expression in patients with stage B2 + C colon cancer subjected to 5FU-based adjuvant chemotherapy