Abstract
MicroRNAs (miRNAs) play a pivotal role in carcinogenesis. Dysregulation of miRNAs, both oncogenic miRNAs and tumour-suppressive miRNAs, is closely associated with cancer development and progression. The levels of miRNAs could be changed epigenetically by DNA methylation in the 5′ untranslated region (UTR) of pre-mature miRNAs. To investigate whether DNA methylation alters the expression of miR-129 in lung cancer, we did DNA methylation assays and found that 5′ UTR region of miR-129-2 gene was absolutely methylated in both A549 and SPCA-1 lung cancer cells, but totally un-methylated in 95-D cells. The expression of miR-129 was restored by 5-Aza-2’-deoxycytidine (DAC), a de-methylation agent, in both A549 and SPCA-1 cells, resulting in attenuated cell migration and invasion ability, and decreased protein level of NF-κB, which indicates the involvement of NF-κB pathway. To further illustrate the roles of miR-129 in lung tumourigenesis, we overexpressed miR-129 in lung cancer cells by transfection of miR-129 mimics, and found arrested cell proliferation at G2/M phase of cell cycle and inhibited cell invasion. These findings strongly suggest that miR-129 is a tumour suppressive miRNA, playing important roles in the development and progression of human lung cancer.
Highlights
Lung cancer, including small-cell lung carcinoma (SCLC) and non-SCLC (NSCLC), is the leading cause of cancer-related mortality worldwide, with a 5-year survival rate of less than 15% [1,2,3].microRNAs, a class of small non-coding RNAs in animals and plants, averaging 20 to 24 nucleotides, are known to bind to the 30 untranslated regions (UTRs) of target mRNAs, resulting in mRNAs degradation or translational inhibition, through which miRNAs control a wide variety of physiological processes in normal cells, including proliferation, differentiation and apoptosis [4]
Vol 19, No 9, 2015 either miR-129 overexpressing or hypomethylated lung cancer cells, and verified that Valosin-containing protein (VCP) gene is a target of miR-129
We found that there was a clear band of 188 bp in 95-D cells amplified with un-methylated primers, whereas no band was found with methylated primers (Fig. S1B)
Summary
Lung cancer, including small-cell lung carcinoma (SCLC) and non-SCLC (NSCLC), is the leading cause of cancer-related mortality worldwide, with a 5-year survival rate of less than 15% [1,2,3].microRNAs (miRNAs), a class of small non-coding RNAs in animals and plants, averaging 20 to 24 nucleotides, are known to bind to the 30 untranslated regions (UTRs) of target mRNAs, resulting in mRNAs degradation or translational inhibition, through which miRNAs control a wide variety of physiological processes in normal cells, including proliferation, differentiation and apoptosis [4]. The results showed a notably elevated protein level of E-cadherin, an active suppressor of invasion for many epithelial cancers, as compared with control cells (Fig. 4B). A549 cells transfected with miR-129 mimics or the control for miR-129 mimics were collected after 48 hrs, and examined for the expression levels of selected genes using specific primers.
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