Hedgehog信号通路通过细胞自噬调控神经胶质细胞瘤生长的分子机制

The etiology of glioma is tightly linked to aberrant Hedgehog (Hh)/GLI activity. However, the activation mechanism of Hh/GLI pathway, as well as subsequent induction of proliferation and apoptosis resistance have not been completely elucidated. In our preliminary studies, level of GLI2 DNA methylation at promoter region was found to be much lower in glioma tissues than adjacent normal tissues. Furthermore, blockade of Hh signaling pathway resulted in inhibited proliferation and increased antophagy. Gene microarray technique allowed us to discover elevated expression of IκBα and BNIP3 and diminished NFκB in glioma cells. Therefore, we speculate that GLI2 DNA methylation at promoter region may contribute to aberrant activation of Hh/Gli signaling pathway. Hh signaling pathway may regulate autophagy through "GLI2-IκBα/NFκB-BNIP3" signaling axis. This project aims to study the effect and epigenetic mechanisms of aberrant activation of Hh/Gli signaling pathway in proliferation and survival of glioma cells, find new target genes regulated by GLI2, and investigate roles of "GLI2-IκBα/NFκB-BNIP3" signaling axis in autophagy. These findings will provide new insights into molecular mechanisms of cancer progression and identify potential targets for therapeutic intervention.

Hedgehog-GLI（Hh）信号通路在神经胶质瘤中异常活化，但导致其异常活化以及异常活化诱导细胞增殖、凋亡抵抗的机制尚不明确。我们最近发现神经胶质瘤中转录因子GLI2启动子区甲基化程度明显低于癌旁组织；阻断Hh通路抑制神经胶质瘤细胞增殖并导致细胞自噬增高。此外基因芯片发现：抑制Hh通路后神经胶质瘤细胞中IκBα表达增加，NFκB表达减少，同时BNIP3表达增加。据此推测：GLI2启动子区低甲基化导致Hh通路异常活化；Hh通路通过"GLI2-IκBα/NFκB-BNIP3"信号轴调控细胞自噬，影响肿瘤细胞存活。本项目以神经胶质瘤为研究对象，研究导致GLI2异常活化的表观遗传学机制；发掘受GLI2调控的新靶基因；从分子、细胞及整体层面采用多种手段阐明Hh通路通过"GLI2-IκBα/NFκB-BNIP3"信号轴调控细胞自噬影响肿瘤细胞存活的分子机制。该项研究将为神经胶质瘤治疗提供理论依据。

Hedgehog（Hh）信号通路在胚胎发育中发挥重要作用，有报道显示Hh信号通路异常活化与神经胶质瘤等多种肿瘤关系密切。.Gli2是Hh信号通路的重要转录因子，其下游靶基因在不同组织中具有特异性。在本项研究中，我们在神经胶质瘤中鉴定了多个Hh/Gli2的靶基因，其中ARHGEF16是一个Gli2的直接靶基因。我们通过体内、体外实验验证了Hh信号异常活化可以促进神经胶质瘤的生长，同时我们发现该作用依赖于Gli2下游靶基因ARHGEF16。我们还鉴定了ARHGEF16的相互作用蛋白CKAP5，我们发现ARHGEF16促进神经胶质瘤生长的功能依赖于CKAP5。同时，我们发现自噬相关基因如LC3、p62等也受Hh信号调控，抑制Hh信号能诱导细胞自噬。.基于本基金的支持，我们还鉴定了一个SMO调控因子Arl13b。Arl13b通过结合SMO，调控SMO的稳定性、运输和定位，促进胃癌在体内、体外的生长、侵袭和迁移。临床数据表明，Arl13b在胃癌肿瘤组织中高表达，并与胃癌患者的预后有相关性。另外，我们还与美国杜兰大学医学院卢华教授合作，鉴定了肝癌中p53的功能获得性突变R249S，发现了新的CDK4-PIN1-p53(R249S)-c-Myc信号通路。.本研究项目在理论上有助于拓展我们对Hh信号通路转导过程的认识，在实际上将有助于阐明Hh信号通路在肿瘤发展过程中的作用和分子机制，为肿瘤的诊疗提供新的靶点，推动肿瘤的转化医学和精准医疗研究。