MULT1E/mIL-12: a novel bifunctional protein for natural killer cell activation

Intratumoral expression using a NFkB-based promoter enhances IL12 antitumor efficacy

Interleukin 12 is a promising anti-cancer agent; however, IL12 systemic administration is hampered by side-effects. Although intratumoral administration of IL12 is giving promising results in clinical trials, only a small percentage of patients show a complete therapeutic response. This outcome could be improved by controlling the IL12 expression window. In this work we have tested the efficacy of a self-processing P2A and codon optimized murine IL12 (mIL12Pop) using inflammation-regulated lentivectors in a syngeneic tumor model. Our results show that implantation of cells expressing mIL12Pop employing either the strong constitutive SFFV promoter or a NFkB-based promoter reduced tumor growth, caused CD8⁺ T cell activation and increased IFNγ production. Importantly, the use of NFkBp-mIL12Pop increased the number of CD8⁺ TILs and improved the remission rate without increasing IL12-serum concentration. Further experiments suggest that there is a threshold intratumoral IL12 concentration that must be reached to trigger an efficient antitumor response and a limit that once surpassed causes detrimental systemic side effects. Altogether, these results demonstrate that using NFKBp-mIL12Pop significantly increases the overall survival of the mice. In summary, this new inflammation-regulated expression system might be useful for the development of new IL12 delivery systems with improved anti-tumor activity and limited toxicity.

Retention of functional characteristics of glutathione-S-transferase and lactate dehydrogenase-A in fusion protein

A paradigm shift toward fusion proteins to render multiple functionalities and applications on a single platform has been incurred in enzyme based diagnosis. Herein, we report development and systematic characterizations of glutathione-S-transferase (GST) and human lactate dehydrogenase A (hLDHA) in a fusion protein (GST-hLDHA) to achieve functional activities of GST and hLDHA simultaneously. The GST-pGEX-4T-2 vector system was used for cloning and purification of hLDHA, utilizing the affinity based interaction between GST and GSH in column chromatography. Bacterially purified protein was subjected to the Western blot analysis and structural analysis by circular dichroism spectroscopy, which revealed intact structural framework of the fusion construct. Kinetic characterization of the fusion GST-hLDHA protein toward GSH and NADH, suggested retention of functional activities of GST and hLDHA in fused protein as indicated by the kinetic parameters k_m and k_cat/k_m. Further analysis of effect of temperature and pH on GST-hLDHA activity revealed maximum activity around human physiological conditions (37°C and pH 8). Preservation of the structural and functional characteristics of the fusion enzyme paves the way for potential application for the detection of NADH and GSH in conjunction as biomarkers for cancer diagnosis.

Fusion Proteins of NKG2D/NKG2DL in Cancer Immunotherapy

NKG2D (natural killer group 2, member D) is an important activating receptor in natural killer (NK) cells and some T cells. NKG2D ligands (NKG2DLs) are specifically expressed on most tumor cells. The engagement of these ligands on tumor cells to NKG2D on NK cells will induce cell-mediated cytotoxicity and have target cells destroyed. This gives NKG2D/NKG2DLs great potential in cancer therapeutic application. The creation of NKG2D/NKG2DL-based multi-functional fusion proteins is becoming one of the most promising strategies in immunotherapy for cancer. Antibodies, cytokines, and death receptors have been fused with NKG2D or its ligands to produce many powerful fusion proteins, including NKG2D-based chimeric antigen receptors (CARs). In this article, we review the recent developments of the fusion proteins with NKG2D/NKG2DL ligands in cancer immunotherapy.

MICA/IL-12: A novel bifunctional protein for killer cell activation

Natural killer (NK) cells have the potential to be effective killers of tumor cells. They are governed by inhibitory and activating receptors such as NKG2D, whose ligands are normally upregulated in cells that are stressed, like cancer cells. Advanced cancer cells, however, have ways to reduce the expression of these ligands, leaving them less detectable by NK cells. Along with these receptors, NK cells also require activating cytokines, such as IL-12. A previous study in our laboratory showed that a fusion protein of the extracellular domain of mouse UL-16 binding protein-like transcript 1 (MULT1E) and mouse interleukin 12 (IL-12) can effectively activate mouse NK cells by in vitro assays and in vivo in animal tumor models. The aim of the present study was to expand the concept of developing a novel bifunctional fusion protein for enhanced NK cell activation to human killer cells. The proposed protein combines the extracellular domain of a human NKG2D ligand, MHC class I polypeptide-related sequence A (MICA) and IL-12. It is hypothesized that when expressed by tumor cells, the protein will activate human NK and other killer cells using the NKG2D receptor, and deliver IL-12 to the NK cells where it can interact with the IL-12R and enhance cytotoxicity. The fusion protein, when expressed by engineered tumor cells, indeed activated NK92 cells as measured by an increase in interferon-γ (IFN-γ) production and an increase in cytotoxicity of tumor cells. The fusion protein was also able to increase the proliferation of human peripheral blood mononuclear cells (PBMCs) and augment their production of IFN-γ. This study along with the data from the previous mouse studies suggest that the MICA/IL-12 bifunctional fusion protein represents an effective activator of killer cells for cancer treatment.