NQO1 and lung cancer: Since miR-155 can upregulate NQO1 and HO-1 through activation of the Nrf2 signaling pathway to promote cellular redox homeostasis and cell survival23,24, it appears that miR-155 may also mediate the resistance of A549R lung cancer cells to ATO by activating the Nrf2 signaling pathway and its downstream target genes.