Epigenetics of lung cancer

Uncovering Direct Targets of MiR-19a Involved in Lung Cancer Progression

Micro RNAs (miRNAs) regulate the expression of target genes posttranscriptionally by pairing incompletely with mRNA in a sequence-specific manner. About 30% of human genes are regulated by miRNAs, and a single miRNA is capable of reducing the production of hundreds of proteins by means of incomplete pairing upon miRNA-mRNA binding. Lately, evidence implicating miRNAs in the development of lung cancers has been emerging. In particular, miR-19a, which is highly expressed in malignant lung cancer cells, is considered the key miRNA for tumorigenesis. However, its direct targets remain underreported. In the present study, we focused on six potential miR-19a target genes selected by miRNA target prediction software. To evaluate these genes as direct miR-19a target genes, we performed luciferase, pull-down, and western blot assays. The luciferase activity of plasmids with each miR-19a-binding site was observed to decrease, while increased luciferase activity was observed in the presence of anti-miR-19a locked nucleic acid (LNA). The pull-down assay showed biotinylated miR-19a to bind to AGO2 protein and to four of six potential target mRNAs. Western blot analysis showed that the expression levels of the four genes changed depending on treatment with miR-19a mimic or anti-miR-19a-LNA. Finally, FOXP1, TP53INP1, TNFAIP3, and TUSC2 were identified as miR-19a targets. To examine the function of these four target genes in lung cancer cells, LK79 (which has high miR-19a expression) and A549 (which has low miR-19a expression) were used. The expression of the four target proteins was higher in A549 than in LK79 cells. The four miR-19a target cDNA expression vectors suppressed cell viability, colony formation, migration, and invasion of A549 and LK79 cells, but LK79 cells transfected with FOXP1 and TP53INP1 cDNAs showed no difference compared to the control cells in the invasion assay.

VEGF-mediated cell survival in non-small-cell lung cancer: implications for epigenetic targeting of VEGF receptors as a therapeutic approach

Aims: To evaluate the potential therapeutic utility of histone deacetylase inhibitors (HDACi) in targeting VEGF receptors in non-small-cell lung cancer. Materials & methods: Non-small-cell lung cancer cells were screened for the VEGF receptors at the mRNA and protein levels, while cellular responses to various HDACi were examined. Results: Significant effects on the regulation of the VEGF receptors were observed in response to HDACi. These were associated with decreased secretion of VEGF, decreased cellular proliferation and increased apoptosis which could not be rescued by addition of exogenous recombinant VEGF. Direct remodeling of the VEGFR1 and VEGFR2 promoters was observed. In contrast, HDACi treatments resulted in significant downregulation of the Neuropilin receptors. Conclusion: Epigenetic targeting of the Neuropilin receptors may offer an effective treatment for lung cancer patients in the clinical setting.

Epigenetic: A missing paradigm in cellular and molecular pathways of sulfur mustard lung: a prospective and comparative study

Sulfur mustard (SM, bis- (2-chloroethyl) sulphide) is a chemical warfare agent that causes DNA alkylation, protein modification and membrane damage. SM can trigger several molecular pathways involved in inflammation and oxidative stress, which cause cell necrosis and apoptosis, and loss of cells integrity and function. Epigenetic regulation of gene expression is a growing research topic and is addressed by DNA methylation, histone modification, chromatin remodeling, and noncoding RNAs expression. It seems SM can induce the epigenetic modifications that are translated into change in gene expression. Classification of epigenetic modifications long after exposure to SM would clarify its mechanism and paves a better strategy for the treatment of SM-affected patients. In this study, we review the key aberrant epigenetic modifications that have important roles in chronic obstructive pulmonary disease (COPD) and compared with mustard lung.

Identification and functional annotation of lncRNA genes with hypermethylation in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of mortality worldwide. DNA methylation is an important epigenetic modification for CRC. Although currently a number of studies about DNA methylation of protein coding genes have been carried out, only a few are about the methylation of genes encoding the long noncoding RNAs (lncRNAs). In this study, we identified 761 lncRNA genes with DNA hypermethylation in CRC using a free MethylCap-seq dataset. Integration of lncRNA expression and methylation datasets showed that the expression of lncRNAs is negatively correlated with DNA methylation (p<0.01). Co-methylation network was also constructed to annotate the functions of unknown lncRNAs. Our results showed that a total of 364 lncRNAs were annotated with at least one GO biological process term. The current data-mining work is likely to provide informative clues for biological researchers to further understand the role of lncRNAs in the development of CRC.

Lung adenocarcinoma harboring L858R and T790M mutations in epidermal growth factor receptor, with poor response to gefitinib: A case report

Lung cancer is the leading cause of mortality among malignant diseases in humans worldwide. During the last decade, molecular targeted therapies for non-small cell lung cancer using first-generation, reversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), including gefitinib, have been shown to be a promising approach for patients harboring activating mutations in EGFR. The current study reports a 77-year-old patient diagnosed with adenocarcinoma harboring L858R and T790M point mutations in the EGFR gene. The patient was treated with gefitinib as the second-line therapy, but no clinical benefit was observed. As the majority of patients with lung cancer receiving EGFR-TKI therapy acquire resistance, repeated biopsies and detection of the EGFR mutation state are beneficial for selecting appropriate treatments.