Notch通过炎性白介素信号调控肿瘤髓系来源抑制性细胞的产生和功能

Myeloid-derived suppressor cells (MDSCs) are immune suppressive immature myeloid cells that play an important role in tumor initiation and subsequent growth, invasion and metastasis. Proinflammatory interlukins (ILs )are key extrinsic factors for the generation and function of MDSCs. However, how the interleukin receptor-mediated signaling network effects on the generation and function of MDSCs remains unclear. With a macrophage-specific RBP-J deficiency mouse model, we have found that tumor grows faster in liver of RBP-J deficient mice than in wild type mice, accompanied with the increased tumor associated macrophages (TAMs), while the number of MDSCs increased too. Our previous studies had shown that Notch signaling can regulate both JAK/STAT and NF-κB signaling through positive and negative loop in ILs-mediated chronic inflammation, suggesting that Notch signaling might be a critical intrinsic factor to promote the expansion and function of MDSCs through the proinflammatory ILs-mediated signaling. In the current project, we intend to clarify the contribution of Notch-interleukin receptor-mediated signaling to the expansion and function of MDSCs involved in tumor development by using myeloid-specific RBP-J deficient or Notch signal-activated mice. We will also reveal the key regulation points between Notch signaling and interleukin receptor-mediated pathways for the accumulation and function of MDSCs. Furthermore, we will look for the strategies to intervene with the generation and function of MDSCs by targeting Notch and interleukin receptor-mediated pathways. Our study will explore the molecular mechanism of regulation network of Notch-interleukin receptor-mediated pathways on the generation and function of MDSCs , and finally provide new strategies and targets for the intervention of MDSCs in cancer treatment.

髓系来源抑制细胞(MDSCs)是促使肿瘤发生免疫逃逸的关键免疫抑制细胞之一。肿瘤微环境中炎性白介素是MDSCs产生和发挥功能的关键外在因素，但其信号网络如何影响MDSCs产生和功能尚不清楚。我们利用条件性基因剔除小鼠建立肝肿瘤模型时发现，Notch信号剔除导致肿瘤明显增大，同时伴随MDSCs增多。结合文献和我们前期报道Notch信号对关键促炎白介素信号下游的JAK/STAT和NF-κB途径等都具有正、反两种调节模式，提示：Notch 信号可能通过调控白介素信号参与MDSCs形成和功能。本课题拟利用多种基因修饰小鼠，进一步观察和明确Notch阻断/激活后肿瘤生长与MDSCs及关键白介素信号的关系；确定Notch信号通过白介素信号调控MDSCs形成和功能的关键结点；确定干预MDSCs抑制肿瘤生长的靶点。本研究有望揭示Notch-白介素信号调控MDSCs产生和功能的分子机制，并建立新的干预策略。

免疫治疗是目前抗肿瘤治疗的强有力手段。然而，对肿瘤病人进行免疫治疗效果往往不尽人意，主要原因是肿瘤组织中含有大量的促使肿瘤发生免疫逃逸的免疫抑制细胞。髓系来源抑制细胞(MDSCs)是促肿瘤免疫逃逸的关键免疫抑制细胞之一。研究表明肿瘤微环境中乳酸代谢可参与调节MDSCs分化和功能，但其如何影响MDSCs分化和功能以及调控的机制尚不清楚。文献和我们前期研究发现，Notch信号在髓系细胞发育和分化中发挥重要的调控作用。Notch信号是否通过影响乳酸代谢而调控MDSCs分化和功能尚未见报道。本课题拟利用已经建立的Notch信号条件性基因剔除／激活小鼠荷瘤模型，揭示和阐明Notch信号对MDSCs分化和功能的调控作用及分子机制；发现干预MDSCs分化及/或功能的关键靶点，为建立恶性肿瘤的免疫治疗新策略提供理论依据。. 我们利用髓系细胞特异性激活Notch信号的荷瘤小鼠，通过体内和体外实验发现，髓系细胞Notch信号活化通过减少M-MDSCs向G-MDSCs分化同时增加成熟TAMs分化而抑制肿瘤生长。进一步分析来自髓系细胞Notch激活和对照小鼠的骨髓来源巨噬细胞（BMDMs）RNA-sequencing数据，发现负责乳酸转运的MCT2受体在髓系细胞激活Notch组显著降低。报告基因和CHIP实验结果显示：Notch信号可通过其下游的HES1分子调控MCT2的表达。之后利用HPLC-MS和Co-IP实验，我们发现c-Jun是一个新的乳酸胞内感受器。一系列的分子生物学实验证实Notch信号可通过下调MCT2表达而抑制c-Jun对乳酸盐的摄取，进而影响下游炎性因子COX2表达，促进MDSC向成熟巨噬细胞分化。为进一步在体内验证Notch/HES1-MCT2-c-Jun信号轴调控MDSC分化对肿瘤生长的影响，我们利用移植实验过表达MCT2和使用MCT2抑制剂结合髓系细胞Notch信号活化的荷瘤小鼠均证实：髓系细胞激活Notch信号可通过抑制MCT2表达而减少MDSC对乳酸的摄入，进而促进抗肿瘤的成熟TAMs分化而抑制肿瘤生长。临床肺癌标本进一步证实Notch-Hes1-MCT2-c-Jun信号轴调控肺癌患者髓系细胞发育。上述研究为靶向髓系细胞Notch信号或乳酸代谢进行肿瘤治疗提供了新思路。