| Summary: | 碩士 === 國立陽明大學 === 臨床醫學研究所 === 103 === Lung cancer causes the largest number of cancer-related death in Taiwan. Previously, our lab used laser capture microdissection and cDNA microarray to profile the differentially expressed genes between in situ and invasive lung adenocarcinoma tumors, and cellular prion protein (PrPc) was found upregulated in invasive tumor cells. Similarly, the expression of cellular prion is higher in the more invasive lung cancer cell line CL1-5 than in the less invasive lung cancer cell line CL1-1. Furthermore, we have demonstrated that PrPc plays an important role in lung cancer cell migration and invasion. It was reported that PrPc is involved in cell signaling, differentiation and tumor progression; however, the regulatory mechanism that control PrPc expression in lung cancer is still largely unknown. We used promoter-reporter fusions combined with reporter assays to identify the regions of PRNP promoter that confer differential promoter activity in CL1-1 and CL1-5 cells, and used bioinformatics prediction tools to find candidate transcription factors. We have further used qRT-PCR and luciferase activity assays to verify these candidates and found that NFIL3 expression level is higher in CL1-5 than in CL1-1, and NFIL3 increases PrPc promoter activity, suggesting that NFIL3 may be a positive regulator of PrPc expression. NFIL3 is known to regulate Th17 cell differentiation and embryonic heart development; however, the roles of NFIL3 in regulating PrPc expression and tumor cell migration and invasion in lung cancer are unclear. Our results showed that the protein expression level of NFIL3 is higher in CL1-5 than in CL1-1, and overexpressing NFIL3 in CL1-1 or CL1-5 cell lines increased PrPc expression as well as cancer cell migration and invasion abilities. Furthermore, we performed chromatin immunoprecipitation and verified the binding of NFIL3 to the promoter region containing predicted NFIL3 binding sites, and luciferase assays found that NFIL3 regulates PrPc through its binding sites with PRNP promoter. We examined NFIL3 expression in clinical specimens and found that high NFIL3 expression was associated with poor survival in lung cancer patients. We will further investigate how NFIL3 regulates lung cancer cell migration and invasion through PrPc. Moreover, we will evaluate NFIL3 as a therapeutic target for lung cancer treatment.
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