APEX1 and melanoma: To further verify whether the increased expression of Ref-1 is involved in BRAFi resistance in BRAFV600E PTC, we treated PTC cell lines (BCPAP and K-1, both harboring the BRAFV600E mutation) and a melanoma cell line (A375, harboring the BRAFV600E mutation) with different concentrations of vemurafenib for IC50 testing, and the results showed a higher sensitivity in the melanoma cell line (IC50A375 = 56.46 nM) than in the PTC cell lines (IC50BCPAP = 31.36 μM, IC50K-1 = 36.62 μM) (Fig. 2E).