Targeting MIC shedding to revive host NKG2D-mediated immune response in prostate

描述（由申请人提供）：在前列腺癌中，靶向MIC脱落恢复宿主nkg2d介导的免疫反应nkg2d介导的肿瘤排斥反应已经在实验动物模型中得到了很好的证明。在人类中，由于人类NKG2D配体，MHC I类链相关分子MICA和MICB家族（统称为MIC）的肿瘤脱落，该系统无效。强有力的证据表明，MIC的肿瘤脱落会对nkg2d介导的免疫产生多重负面影响，并提示这是肿瘤逃避免疫破坏和进展的机制之一。肿瘤脱落MIC的机制尚不完全清楚，尽管有多种酶被证明参与其中。然而，由于这些酶的功能复杂性，在临床上使用抑制剂靶向MIC脱落治疗癌症可能不可行。我们的长期目标是确定抑制MIC脱落的最佳策略，并最终利用nkg2d介导的抗肿瘤免疫作为前列腺癌和其他MIC阳性肿瘤的潜在治疗方法。在我们已经完成的研究中，我们已经表明，防止MIC脱落导致体内前列腺肿瘤排斥反应。最近，我们在MIC的a3结构域中定义了一个对调节MIC脱落至关重要的11-aa基序（脱落基序），并生成了一个单链抗体（scFv），通过靶向脱落基序来抑制MIC脱落。在这项提议中，我们特别假设IL-15激动剂靶向MIC脱落与NKG2D介导的免疫反应的扩增相关，可以减缓前列腺癌的进展。我们的实验重点是揭示11-aa脱落基序作为治疗靶点的机制，并评估我们的新抗体靶向MIC脱落与nkg2d介导的免疫反应扩增相关的治疗效果。我们的具体目标是：1)阐明脱落基序调节MIC脱落的机制，并作为抑制MIC脱落的治疗靶点；2)确定持续肿瘤细胞表面MIC刺激对NK细胞NKG2D功能的影响以及IL-15激动剂在此背景下的影响；3)评价抗体介导抑制MIC脱落联合IL-15激动剂对前列腺肿瘤发生和发展的治疗作用。如果我们的抗体与IL-15激动剂联合抑制MIC脱落可以在动物模型中成功地利用宿主抗肿瘤免疫反应，那么这种治疗策略可以很容易地转化为前列腺癌的临床试验。此外，这些试剂还可以进一步设计用于临床应用。此外，由于MIC的脱落在许多恶性肿瘤中都很明显，因此本研究的结果将对癌症治疗具有广泛的临床意义。

DESCRIPTION (provided by applicant): Targeting MIC Shedding to Revive Host NKG2D-mediated Immune Response in Prostate Cancer NKG2D-mediated tumor rejection has been well demonstrated in experimental animal models. In humans, the system is not effective due to tumor shedding of the human NKG2D ligands, the MHC class I chain-related family of molecules MICA and MICB (collectively termed MIC). Strong evidence has demonstrated that tumor shedding of MIC results in multiple negative effects on NKG2D-mediated immunity and suggested that it is one of the mechanisms by which tumors escape immune destruction and progress. The mechanisms by which tumors shed MIC are not fully understood, although a diverse group of enzymes have been shown to be involved. However, the functional complexity of these enzymes may not make it clinically feasible to use inhibitors to target MIC shedding for cancer therapy. Our long-term goal is to define optimal strategies to inhibit MIC shedding and ultimately to harness NKG2D-mediated anti-tumor immunity as potential therapies for prostate cancer and other MIC-positive tumors as well. In our accomplished studies, we have shown that preventing MIC shedding resulted in prostate tumor rejection in vivo. Recently we have defined an 11-aa motif (shedding motif) in the a3 domain of MIC that is critical for regulating MIC shedding and generated a single chain antibody (scFv) that inhibits MIC shedding by targeting the shedding-motif. In this proposal, we specifically hypothesize that targeting MIC shedding in association with amplification of NKG2D- mediated immune responses by IL-15 agonists can attenuate prostate cancer progression. The experimental focus of proposal is to elicit the mechanisms by which the 11-aa shedding-motif is a therapeutic target and to evaluate the therapeutic impacts of targeting MIC shedding with our novel antibody in association with amplification of NKG2D-mediated immune response. Our specific Aims are: 1) to elucidate the mechanisms by which the shedding-motif regulating MIC shedding and is a therapeutic target to inhibit MIC shedding; 2) to define the impact of persistent tumor cell surface MIC stimulation on NKG2D function in NK cells and the impact of IL-15 agonist in this context; 3) To evaluate the therapeutic impact of antibody-mediated inhibition of MIC shedding combined with IL-15 agonists in prostate tumorigenesis and progression. If we show that inhibiting MIC shedding with our antibody in combination of IL-15 agonist can successfully harness host anti- tumor immune responses in animal models, the treatment strategy can be readily translated into clinical trials for prostate cancer. In addition, the reagents can be further engineered for the clinical application. Furthermore, as shedding of MIC was evident in many malignancies, the outcomes of this proposed research will have broad clinical implications for cancer therapy.