MiR-29a/DNMT3A axis participates in Dihydroartemisinin's suppression on lung adenocarcinoma: Implications for overcoming acquired resistance to EGFR-TKIs.

Dihydroartemisinin (DHA), the traditional antimalarial agent, has attracted significant interest as potential anticancer drug, yet its underlying mechanisms are incompletely understood. Herein, we showed that DNA methyltransferase 3 alpha (DNMT3A), a de novo DNA methyltransferase was substantially inhibited by DHA in both in vitro and in vivo lung adenocarcinoma settings. Overexpression of DNMT3A effectively counteracted DHA's inhibition on the proliferation of HCC827 and A549 cells. Intriguingly, DNMT3A was observed to be up-regulated in Gefitinib-resistant HCC827 (HCC827/GR) cells as compared with parental Gefitinib-hypersensitive HCC827 cells. DNMT3A overexpression effectively counteracted the inhibition of Gefitinib on HCC827 cells. Conversely, si-RNA mediated DNMT3A knockdown generated considerable inhibitory effects on HCC827/GR cells, and further increased Gefitinib sensitivity. Furthermore, combination of DHA and Gefitinib generated significant synergistic effects on the suppression of cell viability and induction of apoptosis of both HCC827 and HCC827/GR cells. Finally, our results showed that DHA effectively up-regulated the expression of miR-29a. Transfection with miR-29a mimics substantially suppressed DNMT3A expression whereas with miR-29a inhibitor effectively up-regulated DNMT3A in HCC827 and A549 cells. Furthermore, miR-29a inhibitor effectively restored DHA's suppression on DNMT3A expression in both cell lines. Overall, these data demonstrate that DHA has therapeutic effects on lung adenocarcinoma by down-regulating DNMT3A through miR-29a. Understanding of this mechanism will have implications for overcoming acquired resistance in epidermal growth factor receptor (EGFR) - targeted therapy by using tyrosine kinase inhibitors (TKIs).