INHIBITION OF THE STATS SIGNALING NETWORK

我们之前报道过信号转导器和转录激活剂 3 (STATS) 在 SCCHN 中通过 EGFR 依赖性和 EGFR 独立途径被组成型激活。此外，组成型 STATS 激活可增强 SCCHN 存活并诱导对 EGFR 抑制的抵抗，这表明 STATS 和 STATS 信号通路的组成部分可以单独或与 EGFR 阻断组合作为重要的治疗靶点。在之前的资助期间，我们证明了激活的STATS可以选择性地用代表高亲和力血清诱导元件（hSIE）的双链“诱饵”寡脱氧核苷酸（ODN）靶向，其中STATS诱饵在体外和体内抑制SCCHN的生长。在 NCI RAID 计划的额外支持下，我们证明 STATS 诱饵在非人类灵长类动物模型中没有毒性，并制造了临床级 STATS 诱饵。匹兹堡大学进行了一项 0 期临床试验，以测试 STATS 诱饵对人类 SCCHN 的生物学效应。我们进一步证明了通过靶向抑制 Bcl-X{L} 诱导 SCCHN 细胞死亡，Bcl-X{L} 是一种抗凋亡 Bcl-2 家族成员，其在 SCCHN 中的表达受 STATS 调节，并与 化疗耐药。新结果（参见初步研究）证明了蛋白酶体在调节 SCCHN 细胞中 STATS 和 Bcl-2 家族成员的表达和功能以及 SCCHN 体外和体内增殖和存活方面的重要性。根据我们的初步研究，我们假设 STATS 诱饵会降低人类 SCCHN 中 STATS 靶基因的表达。我们进一步假设 STATS 和 EGFR/STATS 信号网络的其他成分（包括 Bcl-2 家族成员和蛋白酶体）的共同靶向将导致增强的抗肿瘤作用。在具体目标 1 中，我们将 评估 STATS 诱饵在调节正在进行的 0 期试验受试者肿瘤下游靶点方面的药效学。具体目标 2 将研究 STATS 靶向与 Bcl-2 蛋白家族、蛋白酶体和 EGFR 抑制剂联合的抗肿瘤机制。在这一目标中，我们还将在匹兹堡大学和 NCI 正在进行的 I 期合作试验中评估基线磷酸化 STATS/总 STATS 表达在调节西妥昔单抗加硼替佐米治疗反应中的作用。该试验是 SCCHN 中这些药物的首次组合。具体目标 3 将确定口服生物可利用的化合物的抗肿瘤作用，该化合物可单独阻断 STATS、古古甾酮，并在 SCCHN 临床前模型中单独或与阻断 EGFR 或蛋白酶体结合使用。总的来说，我们期望这些研究将使我们能够：a）评估 STATS 诱饵对 SCCHN 患者的影响，b）优化 EGFR/STATS 信号网络共同靶向成分的策略，以及 c）根据我们的临床前模型中的发现测试 SCCHN 患者的治疗反应机制。

We prevlously reported that Signal Transducer and Activator of Transcription 3 (STATS) is constitutively activated in SCCHN via EGFR-dependent and EGFR-independent pathways. Moreover, constitutive STATS activation enhances SCCHN survival and induces resistance to EGFR inhibition, suggesting that STATS, and components of the STATS signaling pathway, may serve as important therapeutic targets either alone or in combination with EGFR blockade. In the previous funding period, we demonstrated that activated STATS could be selectively targeted with a double-stranded "decoy" oligodeoxynucleotide (ODN) representing the high affinity serum inducible element (hSIE), where the STATS decoy inhibited the growth of SCCHN in vitro and in vivo. With additional support from the NCI RAID program we demonstrated that the STATS decoy was not toxic in a non-human primate model and manufactured clinical grade STATS decoy. A phase 0 clinical trial was implemented at the University of Pittsburgh to test the biologic effects of the STATS decoy in human SCCHN. We further demonstrated induction of SCCHN cell death via targeted inhibition of Bcl-X{L}, an antiapoptotic Bcl-2 family member whose expression in SCCHN is regulated by STATS and correlates with chemotherapy resistance. New results (see Preliminary Studies) demonstrate the importance of the proteasome in regulating the expression and function of STATS and Bcl-2 family members in SCCHN cells, as well as the proliferation and survival of SCCHN in vitro and in vivo. Based on our preliminary studies, we hypothesize that STATS decoy will decrease expression of STATS target genes in human SCCHN. We further hypothesize that co-targeting of STATS and other components of the EGFR/STATS signaling network (including Bcl-2 family members and the proteasome) will result in enhanced anti-tumor effects. In Specific Aim 1 we will assess the pharmacodynamics of the STATS decoy in modulating downstream targets in the tumors from subjects enrolled in the ongoing phase 0 trial. Specific Aim 2 will investigate anti-tumor mechanisms of STATS targeting in combination with inhibitors of the Bcl-2 protein family, the proteasome, and the EGFR. In this Aim we will also evaluate the role of baseline phospho-STATS/total STATS expression in modulating response to treatment with cetuximab plus bortezomib in an ongoing collaborative phase I trial at the University of Pittsburgh and the NCI. This trial represents the first combination of these agents in SCCHN. Specific Aim 3 will determine the anti-tumor effects of an orally bioavailable compound that blocks STATS, guggulsterone, alone and in combination with blockade of EGFR or the proteasome in SCCHN preclinical models. Collectively, we expect that these studies will allow us to: a) evaluate the effects of STATS decoy in SCCHN patients, b) optimize strategies for co-targeting components of the EGFR/STATS signaling network, and c) test mechanisms of treatment response in SCCHN patients based on findings in our preclinical models.