Mechanism of action and therapeutic utility of immunosuppressive oligonucleotide

表达重复TTAGGG基序的合成寡核苷酸（ODN）在哺乳动物端粒中高频出现六聚体序列后，可下调多种TLR配体引发的炎症免疫反应以及多克隆激活剂和抗原诱导的适应性免疫细胞反应。这些抑制性ODN可用于治疗以过度旺盛的免疫反应为特征的疾病，包括感染性休克和自身免疫。我们最近的研究表明，抑制性ODN在预防/治疗二氧化硅吸入引起的危及生命的炎症（急性矽肺）中也很有用。具体来说，在一个相关的小鼠模型中，抑制性ODN治疗被证明可以显著降低二氧化硅引起的死亡率和发病率。我们正在研究是否早期使用抑制性ODN进行Rx治疗也能降低对二氧化硅诱导的肺肿瘤的易感性。尽管取得了这些进展，但对抑制性ODN的细胞靶标、负责其识别/摄取的受体或其作用机制知之甚少。我们正在使用微阵列技术来鉴定基因和调控网络，使抑制性ODN能够破坏正在进行的炎症反应，并确定其体内免疫抑制活性的持续时间。从这些研究中获得的见解，我们计划确定负责识别TTAGGG基序的受体，这是抑制活性的关键。微阵列研究表明，大量基因在给予抑制性ODN后迅速下调。我们正在研究这种mRNA表达的普遍减少的调控。收集到的关于抑制性ODN的作用靶点和机制的信息将支持旨在探索其治疗效用的研究。最近的研究结果表明，全身给予抑制性ODN可以改变宿主的免疫环境，这一效应被用来降低宿主对炎症诱导的癌症的易感性。为实现这一目标，已开展了两项调查。首先，在化学诱导的小鼠皮肤癌模型中，正在评估抑制ODN的作用。一系列实验结果表明，ODN显著降低了化学诱导的乳头状瘤的发生频率和大小。此外，在乳头状瘤形成后开始治疗可减小肿瘤大小。其次，研究抑制ODN在慢性矽肺中的作用，以及随之而来的肺癌的发展，已经开始。希望通过这些研究项目确定的抑制性ODN的治疗效用可以用来显著降低宿主对肿瘤发生和进展的易感性。

Synthetic oligonucleotides (ODN) expressing repetitive TTAGGG motifs patterned after hexameric sequences present at high frequency in mammalian teleomeres down-regulate the inflammatory immune responses elicited by a broad range of TLR ligands and the adaptive immune cell responses induced by polyclonal activators and antigens. These suppressive ODN are useful in the treatment of diseases characterized by over-exuberant immune responses, including septic shock and autoimmunity. Our recent studies demonstrate that suppressive ODN are also useful in the prevention/treatment of the life-threatening inflammation caused by silica inhalation (acute silicosis). Specifically, suppressive ODN treatment was shown to significantly reduce silica-induced mortality and morbidity in a relevant murine model. We are in the process of examining whether susceptibility to silica-induced pulmonary tumors can also be reduced by early Rx with suppressive ODN. Despite this progress, very little is known about the cellular targets of suppressive ODN, the receptors responsible for their recognition/uptake, or their mechanism of action. We are using microarray technology to identify the genes and regulatory networks that enable suppressive ODN to disrupt ongoing inflammatory responses and determine the duration of their immuno-inhibitory activity in vivo. With the insight gained from these studies, we plan to identify the receptor(s) responsible for the recognition of the TTAGGG motif key to this suppressive activity. Microarray studies indicate that very large numbers of genes are rapidly down-regulated following administration of suppressive ODN. We are in the process of studying the regulation of this generalized reduction in mRNA expresssion. Information gathered on the targets and mechanism(s) of action of suppressive ODN will support studies designed to explore their therapeutic utility. Recent results suggest that systemically administered suppressive ODN can alter the hosts immune milieu, an effect being harnessed to reduce host susceptibility to inflammation-induced cancers. Two lines of investigation have been initiated to achieve this goal. First, the effect of suppressive ODN in a murine model of chemically-induced skin cancer is being evaluated. Results from a series of experiments indicates that ODN significantly reudce the frequency and size of chemically induced papillomas. Moreover, initiation of therapy after papilloma formation reduces tumor size. Second, studies examining the effect of suppressive ODN in chronic silicosis, and the attendant development of lung cancer, have been initiated. It is hoped that the therapeutic utility of suppressive ODN identified through these research program can be harnessed to significantly reduce host susceptibility to tumor development and progression.