Expression of possible targets for new proteasome inhibitors in diffuse large B‐cell lymphoma

Abstract Objectives Investigating expression of possible targets for proteasome inhibitors in patients with diffuse large B‐cell lymphoma ( DLBCL ) and correlating the findings to clinical parameters and outcome. Methods Tumour material from 92 patients with DLBCL treated with either R‐ CHOP like ( n = 69) or CHOP like ( n = 23) regimens were stained for possible targets of proteasome inhibitors. Results The primary target molecule of bortezomib, proteasome subunit beta, type 5 ( PSMB 5), was not detected in the tumour cells in any of the cases but showed an abundant expression in cells in the microenvironment. However, the deubiquitinases ( DUB s) of the proteasome, the ubiquitin carboxyl‐terminal hydrolase L5 ( UCHL 5) and the ubiquitin specific peptidase 14 ( USP 14), were detected in the cytoplasm of the tumour cells in 77% and 74% of the cases, respectively. The adhesion regulating molecule 1 ( ADRM 1) was detected in 98% of the cases. There was no correlation between the expression of any of the studied markers and clinical outcome or GC /non‐ GC phenotype. Conclusions We suggest that UCHL 5 and/or USP 14 should be further evaluated as new targets for proteasome inhibitors in DLBCL . The lack of expression of PSMB 5 on the tumour cells might provide an explanation of the relatively poor results of bortezomib in DLBCL .