肺癌微环境自主神经纤维新生激活氧化应激防御通路Nrf2/ARE——放疗抵抗新机制

Tumor microenvironment is of utmost importance in regulating the radioresistance of cancer cells. Researchers currently find that there exists plenty of autonomic nerve fibers within the lung cancer microenvironment, and in those organs and glands full of autonomic nerve fibers, the incidence of primary or metastatic cancer is relatively high. Besides, the abnormal organ rhythm due to dysfunction of autonomic nerve system increases in the risk of both cancer incidence and cancer mortality. These findings suggest that there are close associations between autonomic nerves and cancers. A recent study demonstrates that lung cancers were infiltrated by autonomic nerves which contributing to cancer proliferation and dissemination. A clinical retrospective analysis indicates that acetylcholine receptors when activated by nicotine could finally lead to radioresistance of lung cancer, while oral intake of beta-adrenergic receptors (beta-AR) antagonist sensitizes lung cancer patient to irradiation. Our previous study revealed in the lung tissues that both beta-adrenergic receptors and acetylcholine receptors were found expressed on the cell membranes, once these receptors were activated, the radiosensitivity of lung cancer cells was significantly decreased. In addition, autonomic nerve fibers were also found to activate the key pathway of cellular stress -- Nrf2/ARE. Taken together, the current proposal hypothesizes that neurotransmitters released from autonomic nerve fibers out of the lung cancer microenvironment can activate the beta-adrenergic receptors and acetylcholine receptors expressed on cancer cells, which in turn stimulates Nrf2/ARE pathway, and finally results in significant radioresistance of lung cancer cells. Our proposal aims to reveal the role of autonomic nerve fibers in the induction of radioresistance for lung cancer cells by employing in vitro and in vivo nerve ablation methods, as well as to explore its underlying mechanisms through investigation on the receptors/Nrf2/ARE pathway. We anticipate that our above estimated results could initiate the development of new possible strategies to reverse lung cancer radioresistance by targeting autonomic nerve system.

肿瘤微环境是决定放射敏感性的关键因素之一。新近发现肺癌微环境中存在丰富的自主神经新生纤维支配，与肿瘤关系极为密切：自主神经丰富的内脏和腺体恰好是肿瘤好发和转移部位，且自主神经紊乱致使器官节律异常可致肿瘤发生和死亡风险增加。研究发现肺癌微环境高密度的自主神经新生纤维及递质可促进肿瘤增殖播散，抗拒凋亡；临床回顾研究提示服用β受体阻滞剂可显著增加肺癌放疗疗效；我们预实验也证实肺癌组织中存在自主神经，表达β受体和胆碱受体，且介导肺癌细胞放射抗拒。自主神经纤维还可激活细胞应激防御的关键通路Nrf2/ARE。由此推测：肺癌微环境中自主神经释放递质作用于β受体和胆碱受体，激活氧化应激防御通路Nrf2/ARE，导致放疗抵抗。本项目通过离断支配肺的自主神经，研究自主神经对肺癌放疗抵抗的作用，进一步观察是否由受体及下游Nrf2/ARE通路介导，并探讨逆转放疗抵抗的新方法。

肿瘤的免疫微环境是近年来备受瞩目的制约放疗疗效的关键因素，而越来越多的研究表明，自主神经纤维支配是肿瘤免疫微环境中极为重要的组成部分，调控着肿瘤微环境中的免疫状态。本研究中，聚焦自主神经递质儿茶酚胺与放疗敏感性的关系，探究其对肿瘤微环境的影响。我们的研究发现，非小细胞肺癌（NSCLC）患者放疗前血浆去甲肾上腺素（NE）含量在放疗敏感及放疗不敏感患者间差异表达（放疗敏感组VS放疗不敏感组：435.39 pg/mL VS 533.85 pg/mL，p = 0.0112），且在接受SBRT放疗的NSCLC患者中更明显（放疗敏感组VS放疗不敏感组：393.21 pg/mL VS 569.45 pg/mL，p = 0.0004）。通过小鼠皮下移植瘤模型，发现TGFβ1在NE介导放射抗拒中发挥了关键作用，肿瘤微环境中蓄积的TGFβ1抑制放疗后瘤体内CD8+T细胞应答，进一步通过体外实验证明NE是通过活化ERK-AP-1通路刺激NSCLC自分泌TGFβ1。此外，我们还探究了交感神经递质在调控肿瘤相关巨噬细胞极化影响肺癌血管新生中的作用，从另一方面阐述了交感神经递质对肿瘤对肿瘤微环境的影响。本研究为神经递质介导NSCLC放疗抵抗提供理论依据，也为NSCLC放射增敏提供了特异性新机制、新靶点，具有十分重要的临床意义。