Lysophosphatidic acid-mediated resistance in ovarian carcinoma

浆液性卵巢癌预后不良，是女性癌症死亡的第五大原因，主要是由于临床成功的一线辅助化疗后肿瘤的再生长和耐药肿瘤细胞的选择。潜在的机制在很大程度上仍然是难以捉摸的，但可能涉及化疗耐药肿瘤细胞和球体漂浮在腹腔积液（腹水）。在粘附到浆膜后，这些细胞通过间皮侵入，并且在与细胞外基质接触时增殖以形成跨体腔转移。肿瘤相关巨噬细胞（tumor-associated macrophages，TAMs）促进了肿瘤的进展和治疗耐药性。人浆液性卵巢癌是一种独特的实验系统，它不仅可以从腹水中分离出大量的原发性肿瘤细胞和免疫细胞，而且可以在自体腹水中培养这些细胞，而不需要任何人工添加剂。使用该系统，我们已经能够从单个未经治疗的患者的腹水中分离出化学抗性以及化学敏感的肿瘤细胞球状体。此外，化学敏感球体的化学疗法导致化学抗性细胞的选择，从而为研究原发性和治疗诱导的抗性提供系统。比较RNA-Seq实验导致溶血磷脂酸（LPA）受体基因LPAR 3与化学抗性的关联，并将LPAR 6鉴定为TAM特异性受体基因。LPA的酶促生成是一种已知的不良临床结果的介质，其严重依赖于分泌的磷脂酶A2和自分泌运动因子。我们的RNA-Seq分析表明，TAM以比肿瘤细胞高得多的水平表达编码这些酶（PLA 2G 7，ENPP 2）的几个基因，这表明两种细胞类型在LPA介导的信号传导中的合作。基于这些观察结果，我们提出解决以下具体目标：（i）我们将系统地研究肿瘤细胞、TAM和腹水中的LPA信号传导组分，并将研究与肿瘤复发的潜在关联（Reinartz）。(ii)我们将通过建立转录信号网络和分析特定信号组分的功能来定义这些细胞中LPAR触发的信号通路（Müller）。(iii)我们将讨论LPA信号通路在化疗耐药性和基质相互作用中的作用（Müller）。(iv)我们将分析LPA在TAM极化中的作用以及肿瘤细胞和TAM在共培养系统中LPA产生和信号传导中的假定合作（Reinartz）。最终，本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卵巢癌辅助治疗的改进提供基础。

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.