Stigmasterol reverses rituximab resistance in diffuse large B-cell lymphoma via the MAPK1 signaling pathway

Background: Rituximab (RIT) resistance significantly hampers the treatment efficacy in diffuse large B-cell lymphoma (DLBCL), leading to poor prognosis. We aim to investigate the potential of stigmasterol, a natural compound, to reverse RIT resistance in DLBCL through modulation of the mitogen-activated protein kinase 1 (MAPK1) signaling pathway. Methods: The RIT-resistant DLBCL model, Raji-4RH cells, was established by prolonged exposure to increasing concentrations of RIT. The effects of stigmasterol on cell viability, proliferation, migration, and invasion were assessed using Cell Counting Kit-8 (CCK-8) assays, 5-ethynyl-2'-deoxyuridine (EdU) staining, and Transwell assays. Additionally, the role of MAPK1 signaling in stigmasterol’s mechanism of action was evaluated by overexpressing MAPK1 in Raji-4RH cells, and the expression of key multidrug resistance (MDR) proteins was analyzed. Results: Stigmasterol effectively reversed RIT resistance by inhibiting cell proliferation, migration, and invasion. It induced G0/G1 cell cycle arrest and apoptosis, significantly downregulated MDR proteins P-gp, MRP5, and BCRP, and inhibited MAPK1 phosphorylation. The anti-resistance effects of stigmasterol were partially reversed by MAPK1 overexpression, confirming that MAPK1 signaling plays a critical role in its mechanism. Conclusions: Stigmasterol significantly reverses RIT resistance in DLBCL by inhibiting MAPK1 phosphorylation and downregulating MDR protein expression. These findings provide new insights into overcoming RIT resistance and support the potential of stigmasterol as a therapeutic strategy for refractory DLBCL.