N6-methyladenosine modification regulates imatinib resistance of gastrointestinal stromal tumor by enhancing the expression of multidrug transporter MRP1

N⁶-methyladenosine (m⁶A) is a frequently occurring mRNA modification, which regulates mRNA stability, splicing, and translation. However, its role in drug resistance of gastrointestinal stromal tumor (GIST) is not known. Here, we report that m⁶A modification levels are elevated in imatinib-resistant GIST cells and tissues, and that methyltransferase METTL3 is one of the main protein responsible for this aberrant modification. Increased METTL3 levels contributed to imatinib resistance and worse progression-free survival of GIST patients. Mechanistic studies revealed that METTL3-mediated m⁶A modification of the 5'UTR of the multidrug transporter MRP1 mRNA promoted drug resistance of GIST by stimulating MRP1 mRNA translation, via binding with YTHDF1 and eEF-1. Further, METTL3 transcription in imatinib resistant GIST cells was activated by ETV1, leading to the increased m⁶A methylation of MRP1 mRNA. This is the first report showing a novel regulatory mechanism whereby ETV1, METTL3, and the YTHDF1/eEF-1 complex mediate the translation of MRP1 mRNA in an m⁶A-dependent manner to regulate the intracellular concentration of imatinib and drug resistance of GIST. These findings highlight MRP1 as a new potential therapeutic target for imatinib resistance of GIST.