KLF4促进肝癌形成的作用及机制研究

Although tumorigenes is an increasingly hot topic in oncology, its precise mechanism remains unclear. Transcription factor KLF4 (Kruppel-like factor 4) is essential for embryonic stem cell self-renewal and somatic cell reprogramming, however, the functions of Klf4 in cancer cells depending on the context are controversial. In our previous study, overexpression of KLF4 in primary liver cancer cells induced cell cycle arrest in vitro but tumor progression in vivo. Furthermore, autophagy and glycolysis were detected in parallel with cell cycle inhibition after KLF4 overexpression. The protumorigenic functions for autophagy are largely attributed to its ability to promote cancer cell survival in response to tumor hypoxia. Here we want to demonstrate an unexpected connection between autophagy and glucose metabolism that facilitates tumorigenesis driven by KLF4-mTOR signaling pathway. Overall, increased glycolysis in autophagy-competent cells facilitates KLF4-induced tumorigenesis, suggesting a unique mechanism by which autophagy may promote KLF4-driven tumorigenesis in specific metabolic contexts. Therefore, this project will use tumor cells and mouse xenograft model to investigate the signaling pathway regulating KLF4-driven tumorigenesis, focusing on autophagy and glucose metabolism. The predicted outcome of this project will provide novel ideas in tumorigenesis and new targets for cancer therapy.Transcription factor KLF4 (Kruppel-like factor 4) is essential for embryonic stem cell self-renewal and somatic cell reprogramming, however, the functions of Klf4 in cancer cells depending on the context are controversial. In our previous study, overexpression of KLF4 in primary liver cancer cells induced cell cycle arrest in vitro but tumor progression in vivo. Furthermore, autophagy was detected in parallel with cell cycle inhibition after KLF4 overexpression. The protumorigenic functions for autophagy are largely attributed to its ability to promote cancer cell survival in response to tumor hypoxia. Here we want to demonstrate an unexpected connection between autophagy and glucose metabolism that facilitates tumorigenesis driven by KLF4-mTOR signaling pathway. Overall, increased glycolysis in autophagy-competent cells promotes tumor cell survival and restricts necrosis, inflammation during energy deprivation, suggesting a unique mechanism by which autophagy may promote KLF4-driven tumorigenesis in specific metabolic contexts. Therefore, this project will use tumor cells and mouse xenograft model to investigate the signaling pathway regulating KLF4-driven tumorigenesis, focusing on autophagy and glucose metabolism. The predicted outcome of this project will provide novel ideas in tumorigenesis and new targets for liver cancer therapy.

肿瘤如何形成一直是癌症研究的热点，其具体调控机制至今不清。KLF4(Krüppel-like factor 4)是维持干细胞自我更新和参与体细胞重编程的重要转录因子，在不同部位肿瘤中的作用却存在争议。我们前期在肝癌细胞中过表达KLF4，体外细胞出现周期阻滞、自噬和糖酵解增强，体内肿瘤形成能力显著增强。近期文献报道自噬在肿瘤形成中发挥重要作用，分析前期研究结果提示：KLF4自噬糖酵解信号通路可能是肝癌形成的一个新的机制，KLF4通过mTOR信号通路诱导自噬，自噬提高肿瘤糖酵解水平促进细胞存活，限制肿瘤坏死及炎症反应以适应肿瘤生发中心微环境的乏氧状态，增强肿瘤形成能力。据此，本项目拟采用肿瘤细胞及小鼠移植瘤模型，分别从分子、细胞及动物三个水平，以自噬参与KLF4促进肝癌形成的作用为研究主线，对相关信号通路进行系统研究。通过本课题开展，为肝癌形成分子机制提供新思路、为肝癌治疗发现新靶标。

KLF4是与胚胎干细胞自我更新和多向分化潜能密切相关的基因，提示KLF4可能在肿瘤干细胞的干性维持中发挥重要作用。本课题研究发现KLF4表达水平与肝癌细胞的成瘤能力存在着一定的正相关性。过表达KLF4，肝癌细胞体外细胞周期阻滞，发生自噬，体内在裸鼠皮下移植瘤的生长速度明显增强。研究发现KLF4通过mTOR自噬信号通路维持细胞静息状态，发挥化疗耐药，促进肿瘤形成作用。在此基础上筛选出抑制KLF4的小分子化合物小白菊内脂及其类似物含笑内酯，发现含笑内酯可逆转KLF4介导的肿瘤耐药，增加肿瘤细胞对顺铂的敏感性，小白菊内脂可诱导肿瘤细胞自噬，进一步发现含笑内酯主要通过抑制KLF4促肿瘤形成作用，减少肝癌腹水形成，为临床难治性肝癌腹水治疗提供新思路，为开发KLF4作为一个新型抗肿瘤靶点提供理论依据。