Soluble expression, rapid purification, and characterization of human interleukin-24 (IL-24) using a MBP-SUMO dual fusion system in Escherichia coli.

Interleukin-24 (IL-24), a cytokine belonging to the IL-10 family, can selectively induce apoptosis in a broad range of tumor cells without harming normal cells. The efficient and soluble expression of bioactive recombinant IL-24 in Escherichia coli remains an obstacle because of aggregation and insufficient yield. In this study, a fusion of the small ubiquitin-related modifier (SUMO) or maltose-binding protein (MBP) has shown potential in facilitating the produce of IL-24. Thus, a new construct for MBP-SUMO-IL-24 expression would be a promising approach. Our results showed that the MBP-SUMO-IL-24 fusion protein was efficiently expressed as a soluble protein. SUMO protease-mediated cleavage at the SUMO/IL-24 junction released the recombinant IL-24 from the fusion protein. In addition, a His6 tag fused upstream of SUMO allowed for one-step purification through nickel affinity chromatography. Cleavage of the MBP-SUMO tag on the column resulted in the release of purified IL-24 and simplified the purification process. The final yield of IL-24 with approximately 90 % purity was 19 mg/L in flask fermentation. In vitro activity assays demonstrated that the purified IL-24 could induce apoptosis in MCF-7 breast cancer cells, but not normal NHLF cells, in a dose-dependent manner. In summary, we developed a novel method to express soluble and bioactive IL-24 protein in prokaryotic cells.