Inhibitor-induced counter-(up)regulation processes in gastric carcinoma: from secondary resistance mchanisms towards newly acquired tumor vulnerability

胃癌是最常见的肿瘤实体之一，也是癌症相关死亡的主要原因。在其通常处于晚期和无法手术的阶段，传统的细胞抑制学只显示出有限的疗效。虽然在其他肿瘤实体中，靶向抑制剂除了经典的化疗外，还提供了新的选择，但到目前为止，它们在胃癌中的应用仍然很大程度上不成功。例如，像MET或HER受体这样的癌基因经常过度表达，功能相关，是一个负面的预后因素。尽管临床前数据前景看好，但针对这些靶点的特定抑制剂的使用在临床上仍然令人失望。因此，个性化治疗的改进需要确定导致原发或继发耐药的因素。在这种背景下，其他致癌(非靶标)受体酪氨酸激酶(RTK)的代偿性上调可能是非常重要的。事实上，自己的初步数据表明，在开始使用一种特定的抑制剂治疗时，其他Her受体或配体的表达迅速上调。有趣的是，这种代偿性上调伴随着替代致癌RTK的过度激活，可能不仅是继发性耐药的主要原因。相反，它还可以提供新的治疗选择。在此基础上，本项目的目标是：(I)深入表征抑制剂或RNAi/基因敲除引起的致癌RTK表达的变化，通过蛋白质组学确定其他候选基因，并分析这些反(上调)调控过程的细胞和分子效应(Ii)特定抑制剂/基因敲除的有希望的组合的定义，以测试相加/协同效应(Iii)基于二次耐药诱导作为“获得性易损性”的概念的序贯疗法。与单一治疗相比，这一“二次成功概念”还可能包括与单一治疗相比剂量的减少(Iv)利用新鲜患者肿瘤的体外组织切片培养模型，对最有希望的组合和顺序治疗方案在原发肿瘤上进行验证。这也包括遗传特征和NGS诊断。除了细胞培养，还将在体外和体外(组织切片培养)进行各种2D和3D模型的研究，并将继续进行临床前的体内情况(肿瘤异种移植、患者来源的异种移植(PDX/阿凡达模型))和患者肿瘤的体外验证。前瞻性地，治疗研究也将在将在这里建立的原位异种移植/PDX模型中进行。因此，替代致癌RTK的代偿性上调和(过度)激活将不仅被分析为继发性耐药的可能原因，而应通过联合治疗来避免。相反，它将被明确地探索在序贯治疗方案中，作为提高治疗效果的新的有希望的途径。

Gastric cancer is one of the most frequent tumor entities and a leading cause of cancer-related deaths. In its often advanced and inoperable stage, conventional cytostatics show only limited efficacy. While in other tumor entities targeted inhibitors offer novel options in addition to classical chemotherapy, their use in gastric cancer has remained largely unsuccessful so far. For example, oncogenes like MET or HER receptors are often overexpressed, functionally relevant and a negative prognostic factor. Despite promising preclinical data, however, the use of specific inhibitors against these targets has remained disappointing in the clinics. Thus, the improvement of personalized therapies requires the identification of factors responsible for primary or secondary resistance. In this context, the compensatory upregulation of other oncogenic (non-target) receptor tyrosine kinases (RTKs) may well be of major importance. Indeed, own preliminary data demonstrated, upon treatment start with a specific inhibitor, the rapid upregulation of other HER receptors or ligands. Interestingly, this compensatory upregulation with concomitant (over-)activation of alternative oncogenic RTKs may not only be a major reason for secondary resistance. Rather, it could also offer novel therapeutic options. On this basis, this project aims at (i) the in-depth characterization of inhibitor- or RNAi/knockdown-induced alterations in the expression of oncogenic RTKs, the identification of other candidates by proteomics and the analysis of cellular and molecular effects of these counter-(up-)regulation processes (ii) the definition of promising combinations of specific inhibitors / knockdowns, for testing with regard to additive/synergistic effects (iii) the exploration of sequential therapy regimes, based on the concept of secondary resistance induction as “acquired vulnerability”. This „second hit concept“ with established inhibitors may also include dose reductions compared to single treatment (iv) the validation of most promising combinations and sequential therapy regimes on primary tumors, using ex vivo tissue slice culture models from fresh patient tumors. This also includes genetic characteristics and NGS diagnostics. Besides cell culture, studies will be conducted in various 2D- and 3D models in vitro and ex vivo (tissue slice-cultures) and will proceed towards the preclinical in vivo situation (tumor xenografts, patient-derived xenografts (PDX/AVATAR models)) and the ex vivo validation in patients’ tumors. Perspectively, therapy studies will also be performed in orthotopic xenograft-/ PDX models to be established here. Thus, the compensatory upregulation and (over-)activation of alternative oncogenic RTKs will not only be analyzed as possible reason for secondary resistance, to be avoided by combination therapies. Rather, it will be explicitly explored in sequential therapy regimens as novel promising avenue for enhancing therapeutic efficacies.