SIRT4通过影响肿瘤微环境调控非小细胞肺癌生物学行为的分子机制

Loss of contact inhibition is most frequently invoked in the onset of cancer, whereas inflammatory microenvironment has been considered as an important regulator in the context of development. SIRT4 is well-known for its deacetylase activity in mitochondrial energy metabolism. We have demonstrated that SIRT4 was decreased in lung cancer tissues and closely associated with poor survival. Overexpression of SIRT4 inhibited lung cancer cell proliferation, arrested the cell cycle at G1 stage and repressed cell invasion and migration. SIRT4 was highly expressed at confluent status and cell density-dependence. Importantly, NF-κB pathway activity appeared to be hampered and its downstream inflammatory cytokines release decreased by SIRT4 expression. Therefore, we hypothesized that SIRT4 inhibited mitochondrial functions to regain lung cancer cell contact inhibition and prevented the development mediated by inflammatory microenvironment through NF-κB pathway. We will bidirectionally regulate SIRT4 expression and adopt MTT, flow cytometry assay and confocal microscopy to detect the effect of SIRT4 on cell mitochondrial energy and cell contact inhibition. Through the experiments of cell co-culture, cell adhesion experiments and Matrigel Angiogenesis assay, we will clarify that SIRT4 prevent the malignant behaviors of lung cancer cells under inflammatory stimulation. We will also use immortalization assay, animal model and clinical samples to explore the clinical and theoretical value of SIRT4 in regulating tumor microenvironment.

细胞失去接触抑制被认为是肿瘤发生的起始而炎性微环境则促进肿瘤恶性发展。SIRT4是与细胞线粒体能量代谢有关的抑癌因子。我们已经证实SIRT4在肺癌中低表达并与不良预后有关，过表达SIRT4能够抑制肺癌细胞增殖和侵袭迁移能力。SIRT4使肺癌细胞周期停滞于G1期，并且在NIH3T3细胞融合状态和细胞密度增加时表达增加；SIRT4能够抑制NF-κB信号通路和炎性因子的释放。故我们提出假说：SIRT4能够抑制线粒体能量产生而恢复肿瘤细胞的接触抑制，并且能够抑制炎性微环境的促癌作用。我们拟双向调控SIRT4，MTT、荧光共聚焦和流式等技术检测细胞融合之后增殖能力和线粒体能量的变化；利用细胞共培养、细胞粘附和Matrigel血管生成等实验技术检测炎性因子刺激下SIRT4对细胞恶性生物学行为的影响；体外转化细胞实验、小鼠成瘤实验和检测临床标本分析SIRT4影响肿瘤微环境抑制肺癌发生发展的临床意义。

SIRT4 属于sirtuins 家族成员之一，定位于线粒体，已被证实其与恶性肿瘤密切相关。我们在前期研究中已经证实SIRT4在肺癌中低表达，且通过抑制线粒体活动而抑制肺癌细胞的恶性生物学行为，但其是否参与调节肿瘤微环境的作用尚未见报道。本研究首次证实SIRT4通过调节线粒体能量代谢而介导YAP缺失诱导的肺癌细胞接触抑制，更为重要的是，我们证实SIRT4 能够通过NF-κB 通路抑制炎性因子的释放，破坏炎性因子对肺癌细胞的促恶作用。综上所述，本课题所阐明的SIRT4 作为抑癌因子既能够恢复肿瘤细胞的接触抑制，更能够抑制肿瘤炎性微环境对肿瘤的恶性促进作用，不仅有助于深入挖掘SIRT4 抑制肺癌作用的潜能和分子机制，更为其可能成为未来临床早期诊断和有效防治肺癌的新靶点提供理论依据和基础可行性。