DNMT1 inhibition by synergistic application of curcumin and 5-AZA-2'-deoxycytidine implicates enhanced therapeutic potential against lung adenocarcinoma

DNA methyltransferase 1 (DNMT1) is a key epigenetic regulator that maintains DNA methylation patterns during cell division, regulating gene silencing and cancer progression. Aberrant DNMT1 activity is frequently observed in many cancers including lung adenocarcinoma, contributing to epigenetic dysregulation, chromatin remodelling, and the maintenance of cancer stem-like properties. This study investigates the potential impact of targeting DNMT1 using both nucleoside and non-nucleoside inhibitors, specifically 5-AZA-2'-deoxycytidine (hereafter, 5-AZA-CdR or AZA) and curcumin. Molecular docking and MD simulations revealed that curcumin has a high binding affinity to DNMT1 (-10.3 kcal/mol), stabilizing key active site residues of DNMT1. Additionally, 5-AZA-CdR showed low but significant interactions with DNMT1. Cell culture experiments using lung adenocarcinoma cell lines exhibited that treatment of cells with both the compounds, individual and/or synergistic, inhibits DNMT1 enzyme, significantly reduces cell viability, upregulates HDACs and DNMT1-specific miRNA; along with downregulation of DNMT1, SOX2, OCT4, and NANOG. Chromatin immunoprecipitation (ChIP) assay revealed increased recruitment of HDAC1 to the DNMT1 gene promoter region, indicating that HDAC1-mediated histone deacetylation may contribute to the transcriptional silencing of the DNMT1 gene. Correlation analyses indicated a strong association between DNMT1 and SOX2 expression, suggesting an interplay between DNA methylation and pluripotency transcription factors in lung cancer progression. These findings support that, both genetic and enzymatic level inhibition of DNMT1 by AZA and curcumin perform as a double-edged sword, (i) activation of tumor suppressors, and (ii) repression of oncogenes including DNMT1, which may be considered as a better therapeutic strategy for the treatment of lung adenocarcinoma.