抑制NF-kappaB/c-MET信号提高肺癌对EGFR抑制剂与放疗联合治疗的敏感性的机制研究

Molecular target therapy with EGFR inhibitor has brought a revolution to lung cancer therapy. Since irradiation has been shown to be able to enhance EGFR expression in lung cancer cells, combined therapy with EGFR inhibitor and radiation seems to be one of the best therapeutic strategy against lung cancer in theory. However, the results of clinical trials with this combination were not as satisfactory as expected. This indicates that unknown mechanism was responsible for resistance to EGFR inhibitor, radiation, or both. Previously, we have reported that HGF induces EGFR inhibitor resistance in lung cancer cells by activating c-MET receptor and the downstream PI3K/Akt pathway. More recently, we reported that c-MET and PI3K/Akt activation were related to cancer radioresistance. In the present study, we are going to explore the role of c-MET in the combined therapy with EGFR inhibitor and radiation in lung cancer. In the preliminary experiments, we have found that radiation enhanced the activation and expression of c-MET receptor, which could be reversed by inhibition of NF-kappa B signaling. Interestingly, inhibition of NF-kappa B could not abrogate radiation-induced EGFR activation and overexpression. This data indicated that radiation-induced aberrant activation of c-MET, but not EGFR, were mediated by NF-kappa B signaling pathway. On the other hand, inhibition of c-MET successfully increased the susceptibility to EGFR inhibitor in radiation pretreated lung cancer cells. In future study, we will employ techniques including in vitro cell experiments, gene silence, xenograft mouse models, and immunohistochemistry with tumor tissues from patients, to obtain strong evidences of NF-kappa B/c-MET relating to sensitivity of the combination of EGFR inhibitor and radiation. This study may provide scientific basis to novel therapeutic strategy against lung cancer with higher efficacy.

EGFR抑制剂带了来肺癌治疗的革命。由于放射能够提高肺癌细胞EGFR的表达，EGFR抑制剂联合放疗成为理论上最佳治疗模式之一。然而临床实验的疗效并不令人满意，因此提高肺癌对放疗与EGFR抑制剂联合治疗的敏感性有着重要意义。我们已经报道了HGF通过c-MET途径诱导EGFR抑制剂耐药。同时，我们还报道了c-MET的活化与辐射抵抗相关。本项目旨在探讨c-MET在EGFR抑制剂与放疗联合治疗中的作用。初步研究发现：放射提高了c-MET分子的活化与表达进而促进放射抵抗，而抑制NF-kappaB信号则可逆转这一过程。另一方面，抑制c-MET信号可提高放射后的肺癌细胞对EGFR抑制剂的敏感性。本项目拟采用体外培养、基因沉默、小鼠肿瘤模型以及组织标本染色等技术，旨在获得NF-kappaB/c-MET参与放射联合EGFR抑制剂敏感性的可靠证据，为开发新的肺癌治疗模式提供科学依据。

放射治疗抵抗、EGFR酪氨酸激酶抑制剂耐药以及治疗相关性肺毒性、肺损伤，是一直以来影响肺癌治疗的严重问题。有研究表明NF-κB与放疗抵抗相关。因此，在我们的研究中试图探索NF—KB在放疗敏感性、EGFR-TKIs敏感性以及放疗介导肺损伤中的作用，同时也探索了放疗对EGFR-TKIs敏感性的影响。我们通过体外实验以及体内实验，使用NF-κB激酶抑制剂IMD 0354以及p65缺失模型来探明NF-κB通路对放疗敏感性以及EGFR-TKIs敏感性的影响；同时利用放疗诱导致肺纤维化小鼠模型探索IMD 0354对肺损伤的保护作用。在我们的实验结果中发现，放疗可以促进表达并激活MET信号，从而使得肺癌细胞对放疗或是EGFR-TKIs靶向药物产生抵抗；在使用药物(IMD 0354)或使用小干扰siRNA敲除p65来抑制NF-κB信号通路，就可以在体内及体外模型中恢复肺癌细胞对放疗或是EGFR-TKIs亦或是其二者联合效果的敏感性，并且发现这种敏感性的恢复是过逆转MET活化实现的；此外，在小鼠放射性肺损伤/纤维化模型中IMD 0354可以显著的降低肺部毒性。这些发现暗示着抑制NF—KB信号通路可以改善肺癌放疗以及靶向药物EGFR-TKIs的敏感性，同时也可以降低肺癌治疗时的放射性肺损伤。上述内容发表于International Journal of Cancer。. 除上述发现外，我们在EGFR-TKI耐药性促进肺癌的免疫逃逸的机制上也进行了探讨，我们发现EGFR-TKI获得性耐药通过上调PD-L1表达来促进肺癌的免疫逃逸。PI3K-Akt，MAPK和NF-κB信号通路以及AP-1参与了不同EGFR-TKI耐药机制诱导的PD-L1的上调。这可能部分解释了EGFR-TKI敏感性和耐药性肿瘤中PD-L1状态的不同，并揭示了PD-L1在EGFR-TKI耐药性NSCLC中的调控机制。上述内容发表于Molecular Cancer。另一方面，我们还尝试探讨了抗血管生成药物贝伐单抗联合和PARP抑制剂在KRAS突变型结直肠癌中的效果。我们发现，贝伐单抗治疗小鼠皮下瘤模型后能够导致的肿瘤微环境乏氧的产生，诱导肿瘤细胞同源重组修复受损，使肿瘤细胞对PARP抑制剂奥拉帕尼更为敏感。提示贝伐单抗和奥拉帕尼的组合可能为KRAS突变型结直肠癌患者提供潜在的治疗方法。上述研究结果正在投稿中。