Relationship between HLA class I antigen processing machinery component expression and the clinicopathologic characteristics of bladder carcinomas

The goal of this study was to analyze protein expression of antigen processing machinery (APM) components in bladder carcinoma (BC), and to assess the clinical significance of defects in their expression. Tissue from 167 cystectomies for primary BC was used to create a tissue microarray. 128 tumors were urothelial carcinoma (UC). Immunohistochemistry was performed using 14 monoclonal antibodies to APM components (beta 2-microglobulin, calnexin, calreticulin, delta, Z, MB1, LMP2, LMP7, LMP10, HLA class I heavy chain, tapasin, TAP1, TAP2 and ERp57) and MHC class I-related antigen (MICA). Sections of normal urothelium from six subjects were used as controls. All APM components except MB1, LMP2 and TAP2 had significantly lower staining in UC than in normal urothelium. No significant differences were found in APM component scores between different grades of UC. Squamous cell carcinoma had the highest scores, with UC intermediate and other types of BC lowest. High-stage UC demonstrated significantly lower staining for calnexin, LMP2, LMP7 and LMP10 than low-stage UC. With mean 3.6 years follow up, significantly worse survival was associated with a higher delta score in UC (P = 0.038) and a lower calreticulin score in all tumor types (P = 0.028). Most APM components were downregulated in UC. High-stage UC had lower scores for immunoproteasome components compared to low-stage UC. Delta and calreticulin protein expression was associated with survival in UC and in all types of BC, respectively. These findings suggest that APM defects play a role in the clinical course of BC and should be considered in developing immunotherapeutic approaches for its control.