N⁶-methyladenosine modification of MRP7 mRNA modulates its expression and paclitaxel sensitivity in lung...

Methylation of adenosine at the N⁶ position (m⁶A modification) is the most prevalent epitranscriptomic modification in mammals, regulating RNA stability, splicing, translation, and decay. Growing evidence has revealed that m⁶A modification is intricately linked to cancer progression. This study aimed to investigate the effects of m⁶A modification on the sensitivity of lung cancer-derived A549 cells to paclitaxel (PTX). Knockdown of methyltransferase like (METTL) 3/14, the m⁶A writer complex, increased A549 cell viability under PTX, indicating m⁶A modification enhances PTX sensitivity. METTL3/14 knockdown increased the expression of multidrug resistance-associated protein (MRP) 7, but not multiple drug resistance (MDR) 1 or MRP1, promoting PTX efflux. RNA immunoprecipitation showed that MRP7 mRNA is highly methylated at the 5'-untranslated region (UTR), coding region, and 3'-UTR. METTL3/14 knockdown stabilized MRP7 mRNA, while depletion of m⁶A readers YTHDC2 or YTHDF2 also elevated MRP7 mRNA, suggesting these readers mediate its degradation. Moreover, knockdown of the erasers fat mass and obesity-associated protein (FTO) or AlkB homolog 5 as well as treatment with entacapone, an FTO inhibitor, increased PTX sensitivity in PTX-resistant A549 cells. These results suggest that the m⁶A-dependent regulation of MRP7 expression contributes to PTX resistance, highlighting a potential therapeutic avenue in lung cancer.