髓源抑制性细胞促进消融治疗后肝癌细胞上皮-间质转化的作用及其机制研究

Radiofrequency ablation (RFA) is one of the most important therapeutic methods for liver cancer, but those patients are prone to recurrence/metastasis after operation. The underlying mechanism remains largely unknown. A large number of studies have shown that the existence of micrometastases (mainly include tumor microthrombi and tumor satellite micronodules) is the main reason for recurrence and metastasis of liver cancer. We previously found that hematopoietic stem and progenitor cells (HSPCs) were myeloid-biased in cancer patients, and those myeloid precursors were capable of infiltrating in cancer tissues and developing into myeloid-derived suppressor cells (MDSCs) to cause tumor immune escape by inhibiting tumor-specific T cell immunity. We also observed an increased infiltration of MDSCs after ablation, which was related to epithelial-mesenchymal transition (EMT) of the liver cancer cells; and MDSCs could significantly induce tumor cells migration in vitro. We speculate that changes in tumor microenvironment after RFA can recruit/expand MDSCs, and infiltrating MDSCs eventually lead to tumor recurrence/metastasis by promoting EMT of micrometastases tumor cell. Based on these findings, we will combine clinical samples, mouse liver cancer RFA model, and previously constructed human MDSCs model to: 1) demonstrate the local microenvironment changes after RFA, and its effects on the infiltration/amplification of MDSCs in tumor microenvironment and the underlying mechanisms; 2) detect the effects and mechanisms of these MDSCs promoting EMT of the micrometastases cancer cells; 3) explore the potential clinical application of selective inhibition of MDSCs related pathways. The results obtained from this project will not only reveal the molecular mechanisms about how MDSCs promote EMT of the cancer cells, but also provide the theoretical basis for the development of MDSCs as novel target for decreasing/preventing of cancer recurrence/metastasis after RFA.

射频消融（RFA）是肝癌重要治疗手段之一，但术后易于复发/转移，其机制尚未明确。研究表明，微转移灶的存在是术后复发和转移的主因。我们前期研究发现：髓源抑制性细胞（MDSCs）能通过多种途径抑制T细胞免疫来引起免疫逃逸。我们还发现：消融后肿瘤中MDSCs的浸润明显增加，且其数量与肝癌细胞的上皮-间质转化（EMT）显著相关；体外共培养实验表明它们能够诱导肿瘤细胞迁移。我们推测：消融后肿瘤微环境的改变能趋化/扩增MDSCs；它们通过促进微转移灶肿瘤细胞的EMT，最终导致肿瘤复发/转移。以此为基础，本研究拟利用临床标本、小鼠消融模型以及人MDSCs体外模型系统研究：1）消融后肿瘤微环境的改变对MDSCs的趋化/扩增作用及其机制；2）MDSCs对肿瘤细胞EMT的作用和机制；3）选择性抑制MDSCs相关通路的潜在临床应用。研究结果将为靶向MDSCs作为降低/预防消融后复发/转移提供更充分的科学依据。

射频消融（RFA）是肝癌重要治疗手段之一，但部分患者术后易于复发/转移，其机制尚不清楚。基于前期研究发现，我们推测：消融后肿瘤微环境的改变能趋化/扩增MDSC；它们通过促进微转移灶肿瘤细胞的EMT，最终导致肿瘤复发/转移。我们首先检测了肝癌免疫微环境中免疫细胞亚群变化，发现MDSC和巨噬细胞浸润水平明显增加。在小鼠RFA治疗模型中，我们发现MDSC数量与肝内和肺部转移正相关。机制研究发现TGF-β2调控了MDSC的浸润，随后它们通过分泌可溶性因子TNF-α和IL-1β调控肿瘤细胞的侵袭转移。有意思的是，通过使用MDSC的去除剂anti-Ly6G或阻断TGF-β信号可进一步增强RFA治疗疗效。此外，我们发现原癌基因丝氨酸/苏氨酸蛋白激酶PIM2 是IFN-γ 诱导的肿瘤炎症的新型负反馈调节因子。IFN-γ 极化的促炎性巨噬细胞可通过IL-1β来诱导PIM2+癌细胞产生，并使之具备促生存、转移和抵抗T 细胞毒性和免疫治疗的能力。更重要的是，将免疫检查点阻断（ICB）与IL-1β 阻断或PIM2 激酶抑制剂相结合的治疗策略可有效且成功地诱导肿瘤消退。这些结果揭示了肝癌免疫微环境中的MDSC和巨噬细胞促肿瘤功能及其潜在调控机制，有望为RFA联合免疫治疗的治疗方案提供理论基础。