Abstract: Objective To investigate the expression of aldehyde dehydrogenase 1A1 （ALDH1A1） and aldehyde dehydrogenase 6A1 （ALDH6A1） in hilar cholangiocarcinoma tissues and their clinical significance.
Methods Forty-nine cases of hilar cholangiocarcinoma tissues and 10 cases of tumor-adjacent tissues were enrolled from 2005 to 2007. The expression of ALDH1A1 and ALDH6A1 was detected by immunohistochemical SP staining. The correlation of their expression and clinicopathological features as well as prognosis was evaluated. Results The high expression rates of ALDH1A1 and ALDH6A1 were 69.4％ （34／49） and 44.9％（22／49），higher than 30.0％ （3／10） and 10.0％ （1／10） in tumor-adjacent tissues respectively （P＜0.05）. The expression of ALDH1A1 and ALDH6A1 were related to lymph node metastasis （P＜0.05）， but not to gender， age， TNM staging， tumor size， the depth of tumor invasion and nervous invasion （P＞0.05）. The median progressionfree survival （PFS） and median overall survival （OS） of ALDH1A1high expression patients were shorter than those of ALDH1A1low expression patients （12 months vs. 32 months， 12 months vs. 42 months，both P＜0.05）. The median OS of ALDH6A1high expression patients was shorter than that of ALDH6A1low expression patients （16 months vs. 23 months，P＜0.05）， whereas there was no significant difference between median PFS of ALDH6A1high expression and ALDH6A1low expression patients （15 months vs. 22 months，P＞0.05）. Cox multivariate analysis revealed that the depth of invasion and lymph node metastasis were independent factors influencing PFS， and the depth of invasion， lymph node metastasis and ALDH1A1 expression were independent factors influencing OS. Conclusion ALDH1A1 and ALDH6A1 were significantly upregulated in hilar cholangiocarcinoma tissues， and their expression is associated with the development of hilar cholangiocarcinoma. ALDH1A1 may be a new biomarker for predicting the prognosis of hilar cholangiocarcinoma.