Abstract. The present study investigated the potential association between matrix metalloproteinase-9 (MMP-9) expression and the pathogenesis of bladder cancer. The present study reviewed previous studies published in Chinese and English using predefined selection criteria, which identified high-quality studies concerning MMP-9 and bladder cancer. Statistical analyses of the data were conducted using Comprehensive Meta-Analysis software version 2.0. In total, 23 case-control studies were selected, which consisted of 1,040 bladder cancer patients and 244 healthy controls. The expression rates and protein levels of MMP-9 were significantly increased in bladder cancer patients compared with the healthy controls, which was demonstrated using immunohistochemistry (IHC) and enzyme-linked immunosorbent assay-based methods. Furthermore, the expression rate of MMP-9 in histological G1/G2 grade bladder cancer tumors was significantly decreased compared with G3 tumors. Subgroup analysis based on ethnicity demonstrated that the rate of MMP-9 protein expression between bladder cancer patients and healthy controls was significantly different in African, Asian and Caucasian patients, which was identified using IHC. The MMP-9 protein levels in bladder cancer patients and healthy controls were significantly different between Asian and Caucasian patients, but not African patients. The differences between MMP-9 expression in ethnic groups were also evident in the expression rate of MMP-9 identified in histological G1/G2 grade tumors in Asian and Caucasian patients compared with G3 grade tumors, which was not evident in African patients. In conclusion, the present meta-analysis results markedly indicate that MMP-9 expression is associated with clinicopathological features of bladder cancer, suggesting that MMP-9 may be a useful biomarker in the diagnosis and clinical management of bladder cancer, and may be a valuable therapeutic target.
IntroductionWorldwide, bladder cancer is the 7th most common cancer in men and the 17th most common cancer in women (1). Notably, in the developed world, bladder cancer ranks as the 4th and 9th most common cancer in men and women, respectively (2). An estimated 375,000 bladder cancer cases are reported each year around the world, with 68,810 novel cases and ~14,100 mortalities reported in the United States in 2013 (3). Transitional cell carcinoma is the most frequently occurring type of bladder cancer. Other bladder cancer types consist of adenocarcinoma, squamous cell carcinoma and small cell bladder cancer (4,5). Notably, the incidence of bladder cancer increases with age, particularly in men (6). Bladder cancer arises as a result of multistep alterations, among which metastasis is crucial (7). Epidemiological studies have demonstrated that several environmental factors may contribute to bladder cancer risk, including smoking, chronic inflammation, radiation exposure, anticancer drugs and aromatic amines, which are contained in dyes (6,8). The treatment of bladder cancer is based on multiple para...