CYP3A5功能新解: 抑制肺腺癌侵袭转移及分子机制

CYP3A5, one of the cytochrome P450 superfamily members, is involved in the metabolism of drugs, exogenous carcinogens, and endogenous molecules. Previous studies mainly focused on the role of CYP3A5 polymorphism in the etiology of carcinogenesis, pharmacokinetics of anti-cancer drugs, or clinical prognoses. However, the potential physiological function of CYP3A5 in tumor progression remains largely unknown. In our present study, the expression of CYP3A5 was found frequently down-regulated in microarray and clinical lung adenocarcinoma tissues in comparison with their matched non-tumor tissues. Tumors with reduced level of CYP3A5 were more likely to have aggressive characteristics, which was associated with shorter overall survival time and time to disease recurrence. Exogenous expression of CYP3A5 dramatically suppressed migration and invasion of A549 cells in vitro. We thus hypothesized that CYP3A5 might manipulate the progressive and metastatic phenotypes of lung adenocarcinoma. By screening with the Cancer Signaling Phospho Antibody Array and validation with experimental results from lung adenocarcinoma cell lines and tissues, we identified AKT as the potential CYP3A5-targeting signaling. To further investigate the underlying mechanism of CYP3A5 regulating AKT signaling, we performed western blotting and observed the selective inhibition of AKT phosphorylation at Ser473 (instead of Thr308) residue in CYP3A5-stable cells, which was hypothesized to be regulated in an mTORC2-dependent manner. Morever elevated ROS level presented in CYP3A5-stable cells, and ROS was found to inhibit mTORC2 kinase activity without affecting the complex integrity in A549 cells. CYP3A5-induced ROS accumulation was therefor supposed as the key factor for the inhibition of mTORC2 kinase activity and p-AKT(S473) inactivation. Collectively, these findings promoted us to hypothesize that CYP3A5 might play an important role in the regulation of lung adenocarcinoma proression and metastasis via enhancing ROS level and in turn arresting mTORC2/p-AKT (S473) signaling. In this proposal we firstly design to investigate the anti-metastatic function of CYP3A5 in lung adenocarcinoma both in vitro and in vivo. We next plan to perform plasmids transfection experiments to evaluate whether AKT signaling was necessary for CYP3A5-mediated inhibition of lung adenocarcinoma metastasis. Finally we will demonstrate the underlyng mechanism of CYP3A5 regulating AKT signaling by application of si-Rictor and anti-oxidants. This study might provide a new idea for lung adenocarcinoma treatment in the future.

CYP3A5传统功能为参与内外源物质代谢。前期发现CYP3A5在肺腺癌组织中较癌旁低表达，且在侵袭性肺腺癌组织中表达更低；CYP3A5低表达预示较差预后；过表达CYP3A5抑制肺腺癌细胞迁移及侵袭。提示CYP3A5可能具有抑制肺腺癌侵袭转移新功能。前期同时发现CYP3A5选择性抑制AKT(S473)激活致AKT信号通路下调；CYP3A5致细胞内ROS升高，ROS可单纯抑制mTORC2激酶活性。我们因此提出CYP3A5通过ROS单纯抑制mTORC2激酶活性，选择性抑制AKT(S473)活化，阻断AKT信号通路，抑制肺腺癌侵袭转移的科学假想。本研究拟采用体外、体内实验论证CYP3A5抑制肺腺癌侵袭转移新功能；通过质粒瞬转实验论证CYP3A5经AKT信号通路抑制肺腺癌侵袭转移；应用siRNA及工具药物研究CYP3A5靶向ROS/mTORC2调控AKT通路分子机制。本研究可为肺腺癌治疗提供新思路。

研究背景：肺腺癌侵袭转移仍是临床治疗的难点。前期发现肺腺癌中CYP3A5可能是潜在抑癌基因，本项目将研究CYP3A5在肺腺癌中的生物学功能并阐明其分子机制。.研究内容：应用网络大数据及临床样本研究了患者CYP3A5癌和癌旁的差异表达；应用有随访资料的组织芯片研究了CYP3A5的表达和临床病理特征及预后的关系；体内、体外实验研究CYP3A5的生物学功能；应用信号通路芯片筛选并经肺腺癌稳转细胞株验证CYP3A5调控的信号通路及具体分子机制。.研究结果：应用TCGA及GEO数据库筛选及临床样本验证发现，与癌旁正常组织相比肺腺癌组织中CYP3A5表达显著下调；且CYP3A5低表达预示更具侵袭性的临床病理特征及较差的临床预后，是导致总生存时间和无瘤生存时间缩短的独立危险因素；体内、外实验研究表明过表达CYP3A5能够显著抑制肺腺癌细胞株的侵袭及转移；通过信号通路芯片筛选、细胞水平验证及交叉拯救实验，发现CYP3A5抑制肺腺癌侵袭转移依赖于Smad1信号通路；进一步机制研究发现CYP3A5与ATOH8的相互作用可能是抑制Smad1磷酸化的上游分子机制。.研究结论：CYP3A5通过与ATOH8相互作用抑制Smad1信号通路，进而抑制肺腺癌侵袭转移；CYP3A5可可作为肺腺癌治疗的潜在新靶标。