This, in turn, boosts the cells’ ability to pump out drugs, consequently reducing the concentration of sorafenib within tumor cells and attenuating the cytotoxicity of sorafenib and hypomethylation and subsequent upregulation of ABCB1 and ABCG2 promote paclitaxel resistance in ovarian cancer.538 Beside, DNA hypomethylation of around the transcriptional start site of human organic cation transporter-1 (hOCT1, gene SLC22A1) decreases the uptake of quinine-inhibitable sorafenib by hepatoma cells, ultimately leading to sorafenib resistance in liver cancer cells539 (Fig. 5). This evidence concerns the gene ABCG2 and hepatocellular carcinoma.