Expression of alpha-methylacyl-CoA racemase correlates with histopathologic grading in noninvasive bladder cancer

Alpha-methylacyl-CoA racemase (AMACR, p504S), an enzyme involved in cellular energy metabolism by the oxidation of branched-chain fatty acids, is a biomarker that is known to be overexpressed in prostatic and colorectal carcinoma as well as in papillary renal cell carcinoma. We aimed to correlate its immunohistochemically detected expression with histopathological grading in noninvasive bladder cancer in order to hint at a so far unknown role of AMACR in the pathobiology of this tumor entity. Therefore, a cohort of 163 patients (mean age 65.3 years) diagnosed with noninvasive bladder cancer was immunohistochemically investigated in terms of AMACR expression. There was variable positive AMACR staining in 52 (31.9%) of the cases investigated. All tumors were graded by three independent clinical histopathologists according to the 1973 World Health Organization (WHO) and the 1998 WHO/International Society of Urological Pathology (ISUP) system. We found a significant positive correlation between AMACR expression and higher tumor grades using both histopathologic grading schemes. These novel findings clearly allow including high-grade noninvasive bladder carcinomas in the group of AMACR-positive neoplasms and might reflect a so far unknown role of AMACR racemase in the pathobiology and tumor cell energy metabolism of the latter tumor entity.