Characterization of human Fab antibody fragments specific to LMP1 (HLEAFab) in nasopharyngeal carcinoma for potential molecular diagnosis and therapeutic applications.

In view of the previously demonstrated clinical role of the anti-latent membrane protein 1 (LMP1) immunoconjugate HLEAFab-MMC in the treatment of advanced nasopharyngeal carcinoma (NPC), reliable detection of LMP1 expression is of key importance. The aim of this study was to investigate LMP1 status in NPC. Tissue samples from 36 cases were analyzed by immunohistochemistry (IHC) and in situ hybridization for LMP1 and BNLF1 (LMP1 gene) expression, respectively. The results showed LMP1 expression in 20/36 (55.6%) cases in the HLEAFab group compared with 22/36 (61.1%) cases in the S12 group (purified mouse anti-human latent membrane protein 1 monoclonal antibody). The positive staining for LMP1 in the tumor cell membranes exhibited uniformity between HLEAFab and S12. BNLF1 was observed to be amplified in 19/36 NPC patients (52.8%). The sensitivities of HLEAFab-IHC-positivity and S12-IHC-positivity for amplification were 84.2 and 89.5%, respectively. Positive expression of LMP1 was present in a significant proportion of the NPC samples. The present findings provide an important strategy for molecular therapy targeting LMP1 in NPC patients.