Cysteine Protease Network in Tumor Progression and Therapy

描述（由申请人提供）：我们首次报道了Legumain（一种溶酶体半胱氨酸蛋白酶）在大多数啮齿动物和人实体瘤中通过肿瘤细胞以及基质细胞高度表达。我们发现Legumain的表达是由缺氧诱导的，并且在肿瘤发展的早期发生。我们证明豆荚蛋白通过复杂而精确地调节组织蛋白酶和半胱天冬酶网络来增强肿瘤细胞的侵袭/转移并保护细胞免于凋亡。Legumain是哺乳动物中唯一的天冬酰胺酰内肽酶，具有半胱天冬酶样催化位点。半胱天冬酶在植物中不存在，并且据报道豆荚蛋白是植物细胞凋亡的效应蛋白酶。Legumain通过与细胞表面整合素结合并激活MMP-2和组织蛋白酶L，促进肿瘤细胞的侵袭和转移。我们在哺乳动物中证明了豆荚蛋白的进化获得了抗凋亡活性。Legumain通过半胱天冬酶9的催化失活以及通过结合和调节组织蛋白酶B活性来防止组织蛋白酶B激活Bid，从而保护细胞免于程序性细胞死亡。我们已经报道了在肿瘤微环境（TME）中靶向仅由豆荚蛋白激活的细胞不可渗透的前药的策略。在这里，我们证明了在TME中通过高亲和力、细胞不可渗透的天冬酰胺酰内肽酶抑制剂（AEPI-1）抑制豆类蛋白抑制血管生成和肿瘤细胞侵袭/转移。AEPI-1治疗的肿瘤表现出细胞外基质的深刻解体和胶原蛋白含量的显著减少，并导致药物渗透和保留增强。鉴于豆类蛋白的高度限制性特异性及其在肿瘤发展中的功能，我们正在寻求一种假设驱动的方法来推进以下癌症治疗策略。1.将细胞不可渗透的豆类激活的前药靶向肿瘤微环境（TME）并开发基于紫杉醇的前药。2.用细胞不可渗透的AEPI抑制TME中的豆荚蛋白，以抑制肿瘤侵袭/转移和血管生成。3.提高AEPI的细胞渗透性以进一步抑制细胞内豆荚蛋白并使耐药肿瘤细胞对凋亡敏感。施用细胞可渗透的AEPI可能会延长AEPI的功效，但可能导致毒性。我们将评估细胞不可渗透和可渗透的AEPI与现有癌症治疗的协同作用。

DESCRIPTION (provided by applicant): We first reported that legumain, a lysosomal cysteine protease, is highly expressed in majority of rodent and human solid tumors by tumor as well as stromal cells. We found legumain expression is induced by hypoxia and occurs early during tumor development. We demonstrated that legumain enhances tumor cell invasion/ metastasis and protects cells from apoptosis through complex and precise regulation of cathepsin and caspase network. Legumain is the only asparaginyl endopeptidase in mammals and it has a caspase-like catalytic site. The caspases are absent in plants, and legumain was reported to be the effector protease for plant cell apoptosis. Legumain contributes to tumor cell invasion and metastasis through binding to cell surface integrins and activate both MMP-2 and cathepsin L. We demonstrated in mammals legumain evolved to obtain an anti-apoptotic activity. Legumain protects cells from programmed cell death by catalytic inactivation of caspase 9 and by preventing Bid activation by cathepsin B through binding and modulating cathepsin B activity. We have reported the strategy of targeting cell-impermeable prodrug activated only by legumain in the tumor microenvironment (TME). Here, we demonstrated inhibition of legumain in TME by a high affinity, cell impermeable asparaginyl endopeptidase inhibitor (AEPI-1) suppress angiogenesis and tumor cell invasion/metastasis. AEPI-1 treated tumors demonstrated a profound disorganization of extracellular matrix and a significant reduction of collagen content and resulted in enhanced drug penetration and retention. Given the highly restrictive specificity of legumain and its functions in tumor development, we are pursuing a hypothesis-driven approach to advance following strategies as cancer therapies. 1. Targeting cell-Impermeable legumain-activated prodrug to the tumor microenvironment (TME) and developing a paclitaxel based prodrug. 2. Inhibiting legumain in the TME with a cell-impermeable AEPI to suppress tumor invasion/metastasis and angiogenesis. 3. Improving cell permeability of AEPI to further inhibit intracellular legumain and sensitize resistant tumor cells to apoptosis. Administration of cell permeable AEPI will likely extend AEPI efficacy, but may lead to toxicity. We will evaluate both cell- impermeable and permeable AEPIs for synergy with established cancer therapies.