Integrated Bioinformatic and Experimental Analysis of PTEN and DNMT1 Regulation in NSCLC

Background/Objectives: Loss of phosphatase and tensin homolog (PTEN) activity is a frequent feature of non-small-cell lung cancer (NSCLC), and epigenetic repression may contribute to its reduced expression. This study investigated the effects of 5-aza-2'-deoxycytidine (5-aza-dC) on PTEN, DNA methyltransferase 1 (DNMT1), PTEN promoter methylation-specific amplification patterns, and miR-148a-3p expression in NSCLC models. Methods: Publicly available cancer-genomics datasets were analyzed to compare PTEN and DNMT1 transcript abundance and to assess the association between PTEN methylation and transcript abundance in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). A549 and H460 cells were exposed to 2.5 or 5 µM 5-aza-dC for 72 h. Reverse-transcription quantitative PCR (RT-qPCR), Western blotting, methylation-specific PCR (MSP-PCR), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were used to evaluate RNA expression, protein abundance, methylation-specific amplification, and metabolic activity, respectively. Results: Bioinformatic analyses showed lower PTEN and higher DNMT1 expression in both NSCLC subtypes, together with inverse associations between PTEN methylation and transcript abundance. In both cell lines, 5-aza-dC reduced MTT metabolic activity and DNMT1 expression. PTEN mRNA and protein abundance increased significantly at 5 µM, whereas no significant changes were detected at 2.5 µM. MSP-PCR revealed persistent heterogeneous PTEN methylation-specific amplification patterns without clear evidence of progressive promoter demethylation. miR-148a-3p exhibited a biphasic response in A549 cells but remained unchanged in H460 cells. Conclusions: These findings support an association between 5-aza-dC exposure, increased PTEN expression, and reduced DNMT1 expression in NSCLC cells. Quantitative methylation analysis and mechanistic validation are required to clarify the contribution of miR-148a-3p to this regulatory association.