Methotrexate resistance and its regulatory mechanisms in pediatric tumors and beyond

Methotrexate (MTX) is a critical antimetabolite drug in treating various pediatric diseases, including acute lymphoblastic leukemia (ALL), non-Hodgkin lymphoma (NHL), brain tumors, osteosarcoma, inflammatory myofibroblastic tumor (IMT), juvenile scleroderma (JS), and juvenile idiopathic arthritis (JIA). MTX acts as a folate antagonist by inhibiting dihydrofolate reductase (DHFR), an enzyme essential for the synthesis of tetrahydrofolate. This disruption impairs DNA synthesis, repair, and cellular replication, particularly affecting rapidly dividing cells. Despite its efficacy, MTX resistance poses significant challenges, particularly in pediatric oncology, where it undermines the ability to achieve sustained therapeutic effects, resulting in reduced therapeutic efficacy and poor prognosis. The mechanisms of MTX resistance encompassed reduced enzyme activity pivotal for MTX metabolism, enhanced expression of efflux transporters, genetic variations, and alterations in signaling pathways. Multifaceted strategies have been explored to overcome MTX resistance. Combination therapies with ginger extract, gold nanoparticles, and arsenic trioxide (ATO) have been investigated to augment MTX’s cytotoxic effects. Synergies with mTOR inhibitors and MDM2 inhibitors have demonstrated enhanced outcomes in ALL. In JIA, targeting ATP-binding cassette (ABC) transporters and modulating transforming growth factor‑β (TGF-β) signaling pathways have emerged as promising approaches. For osteosarcoma, emphasis on autophagy pathways and non-coding RNAs influencing chemotherapy sensitivity could enhance MTX effectiveness. This review delineates MTX's therapeutic roles, elucidates its resistance mechanisms, and discusses current and potential strategies for managing MTX resistance to bolster treatment effectiveness in pediatric tumors and other diseases. This knowledge base could underpin further research and development of personalized treatments to optimize MTX's clinical benefits.