27-羟基胆固醇在肺腺癌转移中的作用机制研究

27-hydroxycholesterol plays important roles in cardiovascular disease,obesity and inflammation. Recently, 27-hydroxycholesterol was demonstrated to promote metastasis of breast cancer by activating liver X receptor (LXR). We found that 27-hydroxycholesterol also facilitated migration of lung adenocarcinoma, which was not totally dependent on LXR. Treatment of lung adenocarcinoma cells with 27-hydroxycholesterol up-regulated LXR and farnesoid X receptor (FXR) in a parallel manner. Based on these results, in this project, under elevated or reduced concentration of 27-hydroxycholesterol, it would be explored whether LXR and FXR play key roles in 27-hydroxycholesterol-induced metastasis of lung adenocarcinoma by single or double knockout of LXR and FXR, which could contribute to clarify the regulatory mechanism of 27-hydroxycholesterol in metastasis of lung adenocarcinoma. It would be confirmed whether 27-hydroxycholesterol links hypercholesterolemia and metastasis of lung adenocarcinoma. The data from this study not only validated the function of 27-hydroxycholesterol in mediating metastasis of lung adenocarcinoma, providing novel targets for treating lung adenocarcinoma metastasis, revealing the relation between hypercholesterolemia and lung adenocarcinoma metastasis, which would be significant for prevention and treatment of lung adenocarcinoma metastasis.

27-羟基胆固醇在心血管疾病、肥胖和炎症反应中起着重要作用。近期，27-羟基胆固醇被证实通过激活肝X受体(LXR)促进乳腺癌转移。我们发现27-羟基胆固醇同样能够促进肺腺癌细胞迁移，但并不是完全依赖于LXR的激活。27-羟基胆固醇作用肺腺癌细胞同时促进了LXR和法尼酯衍生物X受体（FXR）的表达上调。基于此，本课题拟通过体内体外敲除或过表达LXR和/或FXR，在提高和降低27-羟基胆固醇浓度的条件下，研究LXR和FXR在27-羟基胆固醇调节肺腺癌转移中的作用，明确27-羟基胆固醇在肺腺癌转移中的作用机制，确定27-羟基胆固醇在高胆固醇血症与肺腺癌转移中的侨联作用。通过本课题的研究，不仅能明确27-羟基胆固醇在肺腺癌转移中的作用机制，为治疗肺腺癌转移提供新的靶点，还有助于揭示高胆固醇血症与肺腺癌转移的关系，对预防和治疗肺腺癌转移具有重要意义。

27羟基胆固醇（27HC）在心血管疾病、肥胖和炎症反应中起着重要作用。近期，27HC被证实通过激活肝X受体(LXR)促进乳腺癌转移。我们的研究结果证实27HC在肺腺癌增殖转移中也起着关键作用。27HC促进肺腺癌细胞的增殖、迁移和侵袭，在与巨噬细胞共培养体系中，27HC进一步加速了肺腺癌的迁移和侵袭。敲低27HC合成酶CYP27A1抑制了胆固醇诱导的肺腺癌细胞迁移和侵袭，敲低27HC代谢酶CYP7B1促进胆固醇或27HC诱导的肺腺癌细胞迁移和侵袭。进一步研究显示，27HC诱导FGF2和IL-6的分泌。FGF2作用肺腺癌细胞促进NFκB的磷酸化以及PPIB和Vimentin表达，IL-6作用肺腺癌细胞促进AKT和NFκB磷酸化、PPIB、Snail和Vimentin表达。共培养体系促进了肺腺癌细胞中LXR的表达，从而放大了27HC的作用。敲低LXR明显抑制了27HC诱导的AKT磷酸化及Snail和Vimentin表达，但不影响27HC诱导的NFκB的磷酸化和PPIB表达，说明NFκB的激活和PPIB表达可能依赖于27HC诱导的FGF2和IL-6的分泌。体内实验证实，高胆固醇饮食促进了肺腺癌转移，敲低CYP27A1抑制了这一过程，而CYP7B1敲低加速了这一过程。血清代谢组学结果显示，CYP7B1敲低提升了血清中27HC的水平，同时还增加了4β羟基胆固醇（4βHC）和25羟基胆固醇（25HC）的水平。CYP27A1敲低对27HC、4βHC及25HC的分泌没有影响，但明显抑制了胆甾酮的合成。高胆固醇饮食明显促进了4βHC和25HC的分泌，抑制了胆甾酮的分泌。构建CYP27A1敲除小鼠（CYP27A-/-），与野生型小鼠相比，CYP27A1敲除明显抑制了高胆固醇诱导的肺腺癌转移，说明CYP27A1敲除阻断27HC的合成，从而抑制肺腺癌转移。此外，我们也证实27HC增强了肺腺癌细胞与巨噬细胞共培养体系诱导的破骨细胞分化，说明27HC可能加速肺腺癌的骨转移。我们的的结果说明，27HC通过激活LXR诱导肺腺癌细胞迁移和侵袭，同时27HC增加FGF2和IL-6的分泌，激活AKT和NFκB，促进PPIB、Snail和Vimentin的表达，进一步加速肺腺癌转移。高胆固醇饮食增加27HC的累积，有利于肺腺癌的转移。