Background:As the clinical value of cytokeratin-19 (CK19) and thymidine kinase-1 (TK1) in advanced gastrointestinal cancer remains controversial,we investigated their expression and clinical significance in this disease.Methods:A total of 171 advanced gastrointestinal cancer patients were prospectively enrolled in this study.The mRNA level of CK19 was detected using quantitative real-time reverse transcription-polymerase chain reaction (PCR) in all patients,along with a control group of fifty healthy individuals.Furthermore,detection of TK1 protein was carried out in 96 patients using a chemiluminescence dot blot assay.The primary endpoint was overall survival (OS) time.Results:Positive CK19 mRNA expression was detected in 74 (43.3％) of the 171 patients and positive TK1 expression was detected in 66 (68.8％) of the 96 patients.Furthermore,of the 96 patients,36 (37.5％) were positive for both TK1 protein and CK19 mRNA,30 (31.3％) were negative for TK1 protein,and 15 (15.6％) were negative for TK1 protein and positive for CK19 mRNA.The results indicated that patients who were positive for CK 19 mRNA expression had significantly shorter OS times than those who were negative for it (median OS 7.7 vs.9.7 months,respectively;P =0.02).Moreover,patients who were positive for CK 19 mRNA and TK1 protein expression had shorter OS times (median OS 6.1 months) than those who were positive for CK19 mRNA and negative for TK1 protein expression (median OS 9.1 months;P =0.028).Positive CK19 mRNA expression was significantly associated with shorter OS in the univariate analysis (P =0.027).Based on a multivariate Cox regression analysis,CK19 mRNA together with TK1 protein expression (P =0.024) was an independent predictor for OS in gastrointestinal cancer patients.Conclusions:Our results suggest that positive expression of CK 19 mRNA and TK 1 protein is closely correlated with poor prognosis in advanced gastrointestinal cancer.Furthermore,both CK1 9 and TK 1 are possible gastrointestinal cancer biomarkers.