Immune response evoked by tumor-associated NADH oxidase (tNOX) confers potential inhibitory effect on lung carcinoma in a mouse model

Tumor-associated NADH oxidase (tNOX, ENOX2), which belongs to a family of growth-related NADH oxidases, was originally identified as a plasma membrane protein of rat hepatoma and is inhibited or downregulated by several anti-cancer drugs. The objective of this study was to evaluate the anti-tumor effects of tNOX used as an immunogen against Lewis lung cancer. Human tNOX was expressed in Escherichia coli, purified by His-Tag affinity chromatography, and emulsified with the adjuvant, ISA 201 VG. Immunological analyses of the generated tNOX vaccine were performed in mice. The results of ELISA and ELISpot were significantly higher in tNOX vaccine group compared to the control group. In vivo, we examined the anti-tumor effects of mice that received the tNOX vaccine via the intraperitoneal or subcutaneous routes. Mice were vaccinated three times at 2-week intervals, challenged at 2 weeks after the final vaccination, and terminated at 34 days post-challenge. Antibody titers, tumor volume and histopathological scores were used to evaluate the anti-tumor effects of the tNOX vaccine. Our results revealed that tNOX-vaccinated mice had significantly higher antibody titers than negative control (NC) and challenge control (CC) mice. When compared to the corresponding CC groups, the intraperitoneal and subcutaneous vaccination with tNOX showed a significantly smaller tumor mass volume (P < 0.05) and a significantly lower histological lesion score (P < 0.05), respectively. Our results demonstrate that the use of a xenogeneic tNOX as an immunogen in mice activates immune responses and anti-tumor effects against Lewis lung cancer