Targeting Cell Surface GRP78 as a Novel Therapy for Pancreatic Cancer

描述(申请人提供)：我们提出了一种新的治疗策略，通过靶向细胞表面葡萄糖调节蛋白GRP78(SGRP78)，这是一种应激诱导的主伴侣蛋白，在癌细胞内质网(ER)应激时主动促进到细胞表面，而不影响正常器官。胰腺导管腺癌(PDAC)是所有癌症中死亡率最高的癌症之一，其5年生存率为5%，因此迫切需要一种有效的治疗方法。这一建议是基于我们实验室和其他实验室的新证据，即在胰腺癌中，GRP78在人和小鼠的侵袭前病变和PDAC病变中都显著表达，并且sGRP78与激活的AKT共同定位在PDAC的细胞表面。我们最近发现了一种高度特异和有效的单抗MAb159，它可以靶向sGRP78，导致内吞作用，抑制PI3K/AKT通路，并通过诱导细胞凋亡来诱导肿瘤细胞死亡。我们的假设是，胰腺癌以致密的间质为特征，受到不利的微环境的影响，导致缺氧和营养缺乏。这再加上固有的高增殖和代谢变化，在癌细胞中产生内质网应激，导致GRP78上调，并积极促进GRP78表面定位，作为主要的促生存反应。靶向sGRP78的MAb159可诱导细胞表面sGRP78复合体的内吞和降解，从而为钝化AKT和潜在的其他致癌途径提供一种新的途径，以抑制胰腺癌的生长并与现有的治疗方法协同。此外，MAb159处理诱导了caspase-8的激活，表明激活了外源性细胞死亡。目的1确定MAb159在人PDAC中的作用机制，包括内吞作用、AKT激活、sGRP78与死亡诱导信号复合体的相互作用以及与吉西他滨的协同作用。基于我们令人兴奋的初步数据，MAb159不仅可以抑制并逆转人PDAC的异种移植生长，Aim 2将在PDX-1Cre；KrasG12D；p53f/+(PKC)内源性小鼠胰腺癌模型中测试MAb159单独或联合治疗的有效性，该模型概括了许多人类胰腺癌的特征，并为药物有效性提供了最有力的测试。同时，MAb159的有效性将在具有复杂遗传变化的人PDAC的原位移植模型中进行测试。综上所述，这项建议测试了两个新概念：1)sGRP78部分通过调节PI3K/AKT通路和PDAC中的死亡诱导信号复合体来促进肿瘤的增殖和存活，2)一种新的治疗剂(靶向sGRP78的MAb159)可以逆转肿瘤的生长和耐药性，同时保留正常细胞。本研究结果可应用于其他表达sGRP78并可翻译到临床的高度恶性和耐药肿瘤。

DESCRIPTION (provided by applicant): We propose a novel therapeutic strategy to combat pancreatic cancer by targeting the cell surface glucose regulated protein GRP78 (sGRP78), a stress-inducible master chaperone which is actively promoted to the cell surface upon endoplasmic reticulum (ER) stress in cancer cells, while sparing normal organs. Pancreatic ductal adenocarcinoma (PDAC) is one of deadliest of all cancers with a 5 yr survival rate of <5%, thus there is an urgent need for developing an efficacious therapy for PDAC. This proposal is based on emerging evidence from our laboratory and others that in pancreatic cancer GRP78 is prominently expressed in both human and murine pre-invasive and PDAC lesions and sGRP78 co-localizes with activated AKT at the cell surface of PDAC. We have recently discovered a highly specific and potent monoclonal antibody, MAb159, that targets sGRP78 leading to endocytosis, inhibition of the PI3K/AKT pathway, and tumor cell death by inducing apoptosis. Our hypothesis is that pancreatic cancer characterized by a dense stroma is subjected to an adverse microenvironment resulting in hypoxia and nutrient deprivation. This coupled with intrinsic high proliferation and altered metabolism, creates ER stress in the cancer cells leading to GRP78 upregulation and active promotion of GRP78 surface localization as a major pro-survival response. Targeting sGRP78 with MAb159 induces endocytosis and degradation of sGRP78 complex at the cell surface, thereby offering a novel approach to blunt AKT and potentially other oncogenic pathways to suppress tumor growth and synergize with existing therapy in pancreatic cancer. Additionally, MAb159 treatment induces caspase-8 activation, indicative of activation of extrinsic cell death. Aim 1 will determine the mechanisms o action of MAb159 in human PDAC, addressing the requirement of endocytosis, AKT activation, the interactions between sGRP78 and the death-inducing signaling complex and synergy with gemcitabine. Based on our exciting preliminary data that MAb159 not only inhibits but can regress xenograft growth of human PDAC, Aim 2 will test the efficacy of MAb159, alone or in combination therapy, in the Pdx-1Cre; KrasG12D; p53f/+ (PKC) endogenous mouse pancreatic cancer model which recapitulates many of the features of human pancreatic cancer and offers a most vigorous test for agent efficacy. In parallel, the efficacy of MAb159 will be tested in orthotopic transplantation models of human PDAC with complex genetic alterations. In summary, this proposal tests two new concepts: 1) sGRP78 promotes tumor proliferation and survival in part through regulation of the PI3K/AKT pathway and the death-inducing signaling complex in PDAC, and 2) a novel therapeutic agent (MAb159 targeting sGRP78) may reverse tumor growth and resistance while sparing normal cells. The results of this study can be readily applied to other highly malignant and resistant tumors expressing sGRP78 and translatable to the clinic.