當上皮生長因子接受體 (epidermal growth factor receptor, EGFR)因突變而持續激活的狀態下，能使得肺癌細胞對於酪胺酸激酶抑制劑 (tyrosine kinase inhibitor, TKI) 敏感；然而，往往不到一年內的時間會產生EGFR-TKI的抗藥性。研究顯示癌細胞與幹細胞有相似的生物特性，這暗示著他們兩者之間具有相同的調控訊息路徑。我們發現掌管肺幹細胞自我更新行為的轉錄因子—SOX2高度表現於肺腺癌中，並與上皮－間質細胞轉化 (epithelial-to-mesenchymal transition, EMT) 重要標記之一的VIM呈現相反的關係。另外，由聚落形成實驗 (clonogenic assay) 可以看出SOX2對具有EGFR突變之肺癌細胞生長的必要性。此外，我們發現EGFR-TKI抗藥性的產生伴隨SOX2表現量下降，並且促進EMT的發生。在突變之肺癌細胞中，經組織蛋白去乙醯酶抑制劑 (HDACs inhibitor) 處理後，使SOX2減少但誘導了EMT，因此促使EGFR-TKI抗藥性的發生。相反地，在抗cisplatin藥物的肺癌細胞中具有較高量SOX2的表現。我們的發現支持：受表觀遺傳調控所控制的SOX2，在EGFR-TKI以及cisplatin抗藥性的產生中扮演不同的角色，並可作為肺癌治療當中一具有潛力的生物標記 (biomarker)。

Activating mutations in epidermal growth factor receptor (EGFR) endows lung cancer cells sensitive to EGFR-tyrosine kinase inhibitors (EGFR-TKIs); nonetheless, EGFR-TKI resistance often occurs in less than one year. The intriguing phenomenon that cancer cells have biological features similar to stem cells suggests that cancer and stem cells may share the same regulatory signalling pathway. We found that SOX2, a master transcriptional factor controlling self-renewal of lung stem cells, was highly expressed in lung adenocarcinoma and inversely correlated with VIM, a critical maker for epithelial-to-mesenchymal transition (EMT). Clonogenic analysis showed that SOX2 was essential for cell growth in EGFR-mutated lung cancer cells. Intriguingly, we observed that development of EGFR-TKI resistance attenuated SOX2 expression while inducing EMT. Pharmacological inhibition of HDACs in EGFR-mutated lung cancer cells attenuated SOX2 expression but induced EMT, thus enhancing the development of EGFR-TKI resistance. In contrast, SOX2 expression was enhanced in cisplatin resistant lung cancer cells. Our findings support the notion that SOX2 is under epigenetic control, playing differential roles in the development of EGFR-TKI and cisplatin resistances with a potential as a biomarker for lung cancer treatment.

Introduction 1
Oncogenic addiction in lung adenocarcinoma 1
EGFR mutations and TKI targeted therapy 1
SOX2 signalling in cancer 3
EMT 4
Materials and Methods 6
TCGA database statistics 6
Cell Culture 6
Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) 6
Quantitative Real-time Polymerase Chain Reaction (Q-PCR) 7
Cell Proliferation Assay 8
Plasmid construction 8
Lentiviral Infection 8
Clonogenic Analysis 9
Immunoblotting 9
Spheroid Assay 9
Results 10
Negative correlation of SOX2 expression with EMT in lung adenocarcinoma. 10
SOX2 mediates cell proliferation in lung cancer. 11
Occurrence of EMT with loss of SOX2 expression predetermines EGFR-TKI resistance. 11
Epigenetic regulation controls EMT and SOX2 expression during EGFR-TKI resistance. 12
Involvement of SOX2 in cisplatin resistance of lung adenocarcinoma. 13
Discussion 15
Figures 19
Supplemental Figures 34
Reference 36

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