Tietje Ashlee, Yang Xi, Yu Xianzhong, Wei Yanzhang
Division of Science, Southern Wesleyan University, Central, SC 29634, USA.
Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
Oncol Rep. 2017 Mar;37(3):1889-1895. doi: 10.3892/or.2017.5375. Epub 2017 Jan 16.
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.
自然杀伤（NK）细胞有潜力成为有效的肿瘤细胞杀手。它们受抑制性和激活性受体调控，如NKG2D，其配体通常在应激细胞（如癌细胞）中上调。然而，晚期癌细胞有办法降低这些配体的表达，使它们较难被NK细胞检测到。除了这些受体，NK细胞还需要激活性细胞因子，如白细胞介素12（IL-12）。我们实验室之前的一项研究表明，小鼠UL-16结合蛋白样转录物1（MULT1E）的胞外域与小鼠白细胞介素12（IL-12）的融合蛋白，通过体外试验和动物肿瘤模型体内试验，能有效激活小鼠NK细胞。本研究的目的是将开发新型双功能融合蛋白以增强NK细胞激活的概念扩展到人类杀伤细胞。所提出的蛋白结合了人类NKG2D配体、主要组织相容性复合体I类多肽相关序列A（MICA）的胞外域和IL-12。据推测，当由肿瘤细胞表达时，该蛋白将利用NKG2D受体激活人类NK细胞和其他杀伤细胞，并将IL-12传递给NK细胞，在那里它可以与IL-12受体相互作用并增强细胞毒性。当由工程化肿瘤细胞表达时，融合蛋白确实激活了NK92细胞，这通过干扰素-γ（IFN-γ）产生的增加和肿瘤细胞细胞毒性的增加来衡量。融合蛋白还能够增加人类外周血单个核细胞（PBMC）的增殖并增强其IFN-γ的产生。这项研究以及之前小鼠研究的数据表明，MICA/IL-12双功能融合蛋白是一种用于癌症治疗的有效杀伤细胞激活剂。
