The genetically engineered drug rhCNB induces apoptosis via a mitochondrial route in tumor cells

Identification of a targeting-delivery peptide based on rhCNB

Calcineurin B subunit (CNB) is the regulatory subunit of calcineurin (CN), and its classical function is to regulate the activity of CN. Research in our laboratory has revealed that the recombinant human CNB (rhCNB) is a good antitumor candidate and can be internalized by tumor cells via TLR4 receptor complexes and targeted to tumor tissue in nude mice. However, the fragment or domain of rhCNB mediating internalization and target delivery has not been identified. To explore fragment- mediated rhCNB internalization and target delivery, we generated truncated derivatives of rhCNBs by recombinant DNA technology and examined their cellular uptake. Interactions between truncated rhCNBs and the TLR4 receptor were studied by ELISA and co-immunoprecipitation, and targeting of model tumors in nude mice was examined. The results showed that one truncated derivative, Trun3 (124-169aa), was taken up by cells and targeted tumors with almost the same efficiency as intact rhCNB. These results indicate that Trun3 (45aa) contains the major sequence responsible for rhCNB internalization and tumor targeting and might be developed for drug delivery to tumors.

Genetically engineered drug rhCNB induces apoptosis and cell cycle arrest in both gastric cancer cells and hepatoma cells

Objectives

Calcineurin B (CNB) is a regulatory subunit of calcineurin, and it has antitumor activity. In this study, we aimed to investigate the effect of recombinant human calcineurin B (rhCNB) on the proliferation of gastric cancer cells and hepatoma cells both in vitro and in vivo.

Materials and methods

Cell viability and cell proliferation were detected by MTT and BrdU assay. Flow cytometry, Western blot and immunohistochemistry were performed to determine rhCNB-induced apoptosis and cell cycle arrest. The antitumor activities of rhCNB were observed in mice tumor models.

Results

We demonstrated that rhCNB inhibits the proliferation of gastric cancer cells and hepatoma cells both in vitro and in vivo. We showed that the inhibition of cell proliferation by rhCNB is associated with apoptosis and cell cycle arrest in both tumor cell lines. Furthermore, we indicated that rhCNB promotes p53 protein expression, a potent proapoptotic factor. Meanwhile, we also exhibited that rhCNB decreases the expression of both cyclin B1 and CDK1 proteins, two proteins associated with G₂/M arrest.

Conclusion

Together, these findings suggest that rhCNB markedly inhibits tumor growth and provides guidance for its drug development.