Modulation of Tumor Microenvironment for Improved Therapy of Pancreatic Cancer

摘要 对治疗药物的耐药性是胰腺癌（PC）高致死率的主要原因。 血流不充分和不均匀以及阻塞性促纤维增生间质间室是主要的 阻碍治疗药物的递送和瘤内分布，是肿瘤发生的外在决定因素 治疗耐药的可能性。PC细胞的内在耐药性是由一个独特的药物群体决定的 抵抗癌症干细胞。因此，血流和细胞外基质的选择性调节可导致 改善治疗剂向肿瘤中的递送，而CSC的消除可以改善治疗剂的敏感性。 肿瘤细胞进行化疗。内皮素（ET）-1水平升高和两种ET受体过度表达 (ETAR和ETBR）在肿瘤中观察到。重要的是，ET-1是一种强有力的血管调节剂，可诱导 通过ETAR的血管收缩被认为是肿瘤血流异质性的重要因素， 肿瘤的我们的初步研究表明ET-轴的组分在胰腺肿瘤中表达， TME的各种成分，包括肿瘤细胞、血管和基质细胞以及CSC。此外，针对 ETAR与特异性抑制剂BQ 123选择性地增强异种移植物的灌注并减少缺氧 PC肿瘤，而在自体肿瘤（在PC的KPC小鼠模型中）中， 双特异性抑制剂（波生坦）导致结缔组织增生的显著抑制。我们还观察到ET- 1通过ETBR对小鼠胰腺星状细胞发挥促纤维化作用。我们假设：“连续的 ETBR和ETAR抑制可调节基质和灌注，以增强递送、分布和功效 在临床上，abraxane和吉西他滨的组合将更有效， ET轴的调制”。提出了三个具体目标。目标1中的研究将确定选择性 ETAR和ETBR拮抗剂BQ 123和BQ 788，对大分子（ABX）的递送和分布， 基于小分子（GEM）的治疗剂。将研究放射性标记ABX和GEM的生物分布 用于肿瘤摄取的定量估计。此外，我们将破译ET轴介导的机制作用， 在结缔组织增生的背景下，PC中癌症和基质细胞之间的相互作用。目标2中提议的研究将 确定ET-轴靶向对ABX+GEM在体外（使用独特的癌细胞- 星状细胞共培养物和肿瘤类器官培养物）和体内使用基因工程小鼠（KPC） PC的模型。最后，目标3旨在临床评价安全性并进行初步疗效筛选 联合ET-轴拮抗剂波生坦与FDA批准的联合治疗吉西他滨（GEM）加 Abrexane（ABX）治疗PC患者。总之，拟定的研究将证明以下方法的临床前可行性： 通过靶向单个信号传导轴消除治疗抗性的外在和内在决定因素， 临床确定ET-轴拮抗作用与批准的化疗方案联合的安全性， PC.从这三个目标产生的数据将构成未来致命PC的I/II期临床试验的基础。

ABSTRACT Resistance to therapeutic agents is the predominant cause of high lethality of pancreatic cancer (PC). Inadequate and heterogeneous blood flow and obstructive desmoplastic stromal compartment are the major impediments to the delivery and intratumoral distribution of therapeutic agents and are the extrinsic determinants of therapy resistance in PC. Intrinsic chemoresistance of PC cells is dictated by a unique population of drug resistant cancer stem cells. Hence selective modulation of blood flow and extracellular matrix can lead to improved delivery of therapeutic agents into the tumors, while elimination of CSCs can improve the sensitivity of tumor cells to chemotherapy. Elevated endothelin (ET)-1 levels and overexpression of the two ET receptors (ETAR and ETBR) are observed in tumors. Importantly, ET-1 is a strong vasomodulator and induces vasoconstriction via ETAR is believed to be an important contributor to the tumor blood flow heterogeneity in tumors. Our preliminary studies indicate that the components of ET-axis are expressed in pancreatic tumors in various components of TME including tumor cells, blood vessel and stromal cells and CSCs. Further, targeting of ETAR with a specific inhibitor BQ123 selectively enhanced perfusion and reduced hypoxia in xenograft PC tumors, while prolonged inhibition of ET-axis in autochthonous tumors (in KPC mouse model of PC) with dual specificity inhibitor (Bosentan) resulted in marked inhibition of desmoplasia. We also observed that ET- 1 exerts pro-fibrogenic effects on murine pancreatic stellate cells via ETBR. We hypothesize that: “Sequential inhibition of ETBR and ETAR can modulate stroma and perfusion for enhanced delivery, distribution and efficacy of therapeutic agents and clinically, combination of abraxane and gemcitabine will be more efficacious with the modulation of ET axis”. Three specific aims are proposed. Studies in Aim 1 will determine the effect of selective ETAR and ETBR antagonists BQ123 and BQ788, on the delivery and distribution of macromolecule (ABX) and small molecule-based (GEM) therapeutic agents. Biodistribution of radiolabeled ABX and GEM will be studied for quantitative estimation of tumor uptake. Further, we will decipher the mechanistic role of ET-axis-mediated cross-talk between cancer and stromal cells in PC in the context of desmoplasia. Studies proposed in Aim 2 will determine the impact of ET-axis targeting on the efficacy of ABX+GEM both in vitro (using unique cancer cell- stellate cell co-cultures and tumor organoid cultures) and in vivo using genetically engineered mouse (KPC) model of PC. Finally, Aim 3 is designed to clinically evaluate the safety and perform initial screening for efficacy of combining the ET-axis antagonist Bosentan with FDA-approved combination therapy Gemcitabine (GEM) plus Abrexane (ABX) in PC patients. Altogether, the proposed studies will demonstrate the preclinical feasibility of eliminating both extrinsic and intrinsic determinants of therapy resistance by targeting a single signaling axis and clinically determine the safety of combining ET-axis antagonism with approved chemotherapeutic regimens of PC. The data generated from the three aims will form the basis of future Phase 1/II clinical trials in lethal PC.