The Functional Characterization of Inhibition of DNA Binding 4 in Human Lung Adenocarcinoma Cells

• Main Authors: Hsu, Yuan-Ling, 許元玲
• Other Authors: Wang, Chi-Chung
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/39936405939666640807

碩士 === 輔仁大學 === 基礎醫學研究所碩士班 === 100 === Inhibition of DNA binding 4 (Id4) is a family member of DNA binding proteins (Ids), and it is also a dominant negative regulator of helix-loop-helix transcription factor. Previous studies have demonstrated that Id proteins would compose heterodimer with E protein to block DNA transcription and inhibit cell differentiation. It was known that Id4 has low expression in many kinds of cancers in association with promoter hypermethylation, and then was predicted to be a potential tumor suppressor. In preliminary cDNA microarray data, the expression of Id4 was negatively correlated with lung adenocarcinoma invasive ability. However, the functional roles of Id4 in lung adenocarcinoma are still unclear so far. In this study, we found that the invasion ability in different kinds of human non-small cell lung carcinoma cell lines may be inhibited by upregulation of Id4. To clarify the correlations between Id4 and metastasis, we used the low endogenous Id4-expressing CL1-5 cell line, and high endogenous Id4-inhibiting CL1-0 cell line as the experimental models. We firstly established the CL1-5-Id4 constitutively overexpressed cell clones and CL1-0 Id4 inhibited cells. The morphologies of CL1-5-Id4 cells were observed and found that they changed from mesenchymal phenotype to epithelial phenotype with the downregulation of N-cadherin and upregulation of E-cadherin. CL1-5-Id4 cells could downregulate E2A, Slug, and Twsit, which all are repressors of E-cadherin. Otherwise, the expression level of β-catenin, a transcription factor of epithelial to mesenchymal transition (EMT), was also decreased in CL1-5-Id4 cells. In addition, the migration activity and invasive ability of CL1-5-Id4 cells were decreased. The molecular mechanisms underlying the invasion inhibition were possibly through the downregulation of MMP-2 and MMP-9 protease activities. Furthermore, other cellular functions such as cell proliferation and colony formation capabilities were inhibited by Id4. In conclusion, our results suggest that Id4 may be an important suppressor of metastasis through the change of cell morphology, inhibition of cell migration and invasion. Several genes that correlate with metastasis are altered by upregulation of Id4, but the real role of Id4 in metastatic signal pathways is still unclear. To identify the molecular mechanisms of Id4 in lung cancer cell metastatic inhibition is important in the future studies.