Defective Expression of TGFBR3 Gene and Its Molecular Mechanisms in Non-small Cell Lung Cancer Cell Lines

Background and objective It has been reported that defective expression of TGFBR3 was found in non-small cell lung cancer (NSCLC). However, its molecular mechanisms remain unclear. The aim of this study is to investigate expression of TGFBR3 in NSCLC cell lines and normal human bronchial epithelial cell (HBEpiC), and to explore potential molecular mechanisms underlying inactivation of TGFBR3 gene. Methods Western blot was performed to determine the expression of TGFBR3 in HBEpiC and NSCLC cell lines. Automatic image analysis was carried out to estimate relative expression of TGFBR3 protein. We screened for mutation of the promoter region of TGFBR3 gene using DNA direct sequencing. Bisulfite-sodium modification sequencing was used to detect the methylation status of TGFBR3 promoter. Results TGFBR3 protein level was abnormally reduced in NSCLC cell lines as compared with HBEpiC. There was significant difference in TGFBR3 expression between the highly metastatic cell line 95D and non-metastatic cell lines, including LTEP-α-2, A549 and NCI-H460. No mutation and methylation was found in upstream sites -165 to -75 of the proximal promoter of TGFBR3 in HBEpiC and NSCLC cell lines. Hypermethylation was shown in upstream sites -314 to -199 of the distal promoter of TGFBR3 in HBEpiC and NSCLC cell lines. Conclusion Reduced expression of TGFBR3 was observed in NSCLC cell lines, especially in 95D, suggesting that TGFBR3 might play an important role in development and progression of NSCLC and correlate with NSCLC invasion and migration. The methylation event occurring at TGFBR3 promoter is not a major cause for reduction of TGFBR3 expression