Aldehyde dehydrogenase 1 (ALDH1) expression is associated with a poor prognosis of bladder cancer

Aldehyde dehydrogenase 1 (ALDH1), a cancer stem cell marker, has been reported to be altered in human carcinogenesis. This study assessed the expression of ALDH1 protein in invasive vs. noninvasive bladder cancer tissues for association with clinicopathological factors and bladder cancer prognosis. Tissue samples were collected from 227 bladder cancer patients, including 118 with noninvasive and 109 with invasive bladder cancer for immunostaining of ALDH1 expression. ALDH1 expression in tumor tissues was significantly greater than that in adjacent normal tissues. ALDH1 protein was highly expressed in 29.07% (66/227) of bladder tumor tissues (i.e., 24.58% of noninvasive bladder cancer tissues vs. 33.94% of invasive bladder cancer tissues). In patients with noninvasive bladder cancer, ALDH1 protein expression was significantly associated with an advanced tumor grade and frequent tumor recurrence (P≤0.05). In patients with invasive bladder cancer, ALDH1 protein expression was significantly associated with an advanced tumor grade, stage, as well as lymph node and distant metastases (P≤0.05). After adjusting for the confounding factors, ALDH1 protein expression was significantly associated with relapse-free survival in noninvasive bladder cancer patients [HR (95% CI)=4.45 (1.32-15.04); P=0.027] and overall survival in invasive bladder cancer patients [HR (5% CI)=2.86 (1.72-8.83); P=0.020]. These data indicate that ALDH1 expression plays an important role in bladder cancer development and prognosis. Further validation of our results is warranted in a larger sample cohort, and further investigation of ALDH1 signaling and function will increase our understanding of ALDH1 in bladder cancer progression.