A dendritic cell-based tumour vaccine for lung cancer: full-length XAGE-1b protein-pulsed dendritic cells induce specific cytotoxic T lymphocytes in vitro.

XAGE-1b is regarded as one of the most immunogenic antigens and the most promising targets for lung adenocarcinoma immunotherapy. In this study, we sought to determine whether monocyte-derived dendritic cells (DCs) pulsed with purified full-length XAGE-1b could induce specific cytotoxic T lymphocytes (CTLs) against tumour cells from patients with non-small cell lung cancer (NSCLC) in vitro. XAGE-1b mRNA expression was examined in primary cultures of lung cancer cells and normal lung epithelial cells established from fresh tissues surgically resected from 30 patients with NSCLC using reverse transcription-polymerase chain reaction (RT-PCR). XAGE-1b mRNA expression was observed in 11 of 18 (61.1%) adenocarcinomas and one of 12 (8.3%) lung cancers of other histological types (P = 0.015). The 246-base pairs XAGE-1b gene was inserted into a recombinant expression vector. Full-length XAGE-1b was then expressed in BL21 (DE3) Escherichia coli and purified by AKTA-fast performance liquid chromatography (FPLC). DCs generated from peripheral blood mononuclear cells were pulsed with XAGE-1b by incubation with the protein at an immature stage. The XAGE-1b-pulsed DCs induced CTLs following 14 days of co-culture. Finally, an adherent target detachment (ATD) assay was performed to test the cytotoxicity of the XAGE-1b-specific CTLs against cancer cells and normal lung epithelial cells. The XAGE-1b-specific CTLs had a stronger lytic effect on autologous XAGE-1b mRNA-positive cancer cells than on autologous XAGE-1b mRNA-negative cancer cells or allogenous XAGE-1b mRNA-positive cancer cells. The CTLs had no lytic activity against normal lung epithelial cells. These results can be used to develop simple and effective cancer/testis antigen-based immunotherapies for NSCLC.