Lysophosphatidic acid-mediated resistance in ovarian carcinoma

浆液性卵巢癌预后很差，在女性癌症死亡中排名第五，这主要是由于临床成功的一线辅助化疗和选择耐药肿瘤细胞后肿瘤的再生长所致。其潜在机制在很大程度上仍不清楚，但很可能涉及化疗耐药的肿瘤细胞和漂浮在腹水(腹水)中的球体。在黏附到浆膜后，这些细胞通过间皮细胞侵入，与细胞外基质接触后增殖，形成跨腔转移瘤。多条证据表明，肿瘤相关巨噬细胞(TAM)促进了肿瘤的进展和治疗耐药。人浆液性卵巢癌是一种独特的实验系统，因为它不仅可以从腹水中分离出大量的原发肿瘤细胞和免疫细胞，而且提供了在没有任何人工添加剂的情况下在自体腹水中培养这些细胞的机会。使用这个系统，我们已经能够从个别未经治疗的患者的腹水中分离出化疗耐药以及化疗敏感的肿瘤细胞球体。此外，化疗敏感的球体导致了化疗耐药细胞的选择，从而为研究原发耐药和治疗诱导耐药提供了系统。比较序列分析发现，溶血磷脂酸受体基因LPAR3与化疗耐药有关，LPAR6是所特有的受体基因。LPA的酶促生成严重依赖于磷脂酶A2和自体趋化蛋白的分泌，LPA是临床上已知的不良预后的介体。我们的RNA-Seq分析表明，TAMs表达这些酶(PLA2G7，ENPP2)的几个基因的水平比肿瘤细胞高得多，这表明两种细胞在LPA介导的信号转导中存在合作。基于这些观察，我们建议解决以下具体目标：(I)我们将系统地研究肿瘤细胞中的LPA信号成分，我们将通过建立转录信号网络和分析特定信号成分的功能(Müller)来定义这些细胞中LPAR触发的信号通路。(Iii)我们将讨论LPA信号通路在化疗耐药和基质相互作用中的作用(Müller)。(Iv)我们将分析LPA在TAMs极化中的作用，以及肿瘤细胞和TAMs在共培养系统中LPA生成和信号传递中的可能合作(Reinartz)。该项目的目标是为针对LPA信号网络的药物的最佳临床开发和改进卵巢癌的辅助治疗提供基础。

Serous ovarian carcinoma has a dire prognosis and ranks fifth as the cause of death from cancer in women, mainly due to the regrowth of tumors after clinically successful first-line adjuvant chemotherapy and the selection for resistant tumor cells. The underlying mechanisms remain largely elusive, but are likely to involve chemoresistant tumor cells and spheroids floating in the peritoneal effusion (ascites). After adhesion to serous membranes, these cells invade through the mesothelium and upon contact with the extracellular matrix proliferate to form transcoelomic metastases. Multiple lines of evidence suggest that both tumor progression and therapy resistance are promoted by tumor-associated macrophages (TAMs).Human serous ovarian carcinoma represents a unique experimental system, since it not only allows the isolation of large numbers of primary tumor cells and immune cells from ascites, but also provides the opportunity to culture these cells in autologous ascites fluid without any artificial additives. Using this system, we have been able to isolate from the ascites of individual untreated patients chemoresistant as well as chemosensitive tumor cell spheroids. Moreover, chemotherapy of the chemosensitive spheroids results in the selection of chemoresistant cells, thus providing systems for the studying both primary and therapy-induced resistance. Comparative RNA-Seq experiments led to the association of the lysophosphatidic acid (LPA) receptor gene LPAR3 with chemoresistance, and identified LPAR6 as a TAM-specific receptor gene. The enzymatic generation of LPA, a known mediator of poor clinical outcome, is critically dependent on secreted phospholipases A2 and autotaxin. Our RNA-Seq analyses showed that TAMs express several genes coding for these enzyme (PLA2G7, ENPP2) at much higher levels than tumor cells, pointing to a cooperation between both cell types in LPA-mediated signaling. Based on these observations we propose to address the following specific goals:(i) We will systematically study LPA signaling components in tumor cells, TAMs and ascites fluid and will investigate potential associations with tumor relapse (Reinartz).(ii) We will define LPAR-triggered signaling pathways in these cells by establishing transcriptional signaling networks and analyzing the function of specific signaling components (Müller).(iii) We will address the role of LPA signaling pathways in chemoresistance and matrix interaction (Müller).(iv) We will analyze the role of LPA in the polarization of TAMs and the putative cooperation of tumor cells and TAMs in LPA generation and signaling in co-culture systems (Reinartz).Ultimately, the goal of this project is to provide the basis for an optimal clinical development of drugs directed at the LPA signaling network and an improvement of the adjuvant therapy of ovarian cancer.