A novel biguanide-derivative promotes NEDD4-mediated FGFR1 ubiquitination through BMI1 to overcome osimertinib resistance in NSCLC

Osimertinib (OSI) therapy, a cornerstone in treating non-small cell lung cancer (NSCLC), has been severely limited by rapidly developing acquired resistance. Inhibition of bypass activation using a combination strategy holds promise in overcoming this resistance. Biguanides, with excellent anti-tumor effects, have recently attracted much attention for this potential. The current study investigated whether novel biguanide compounds developed by our team could overcome OSI resistance and the underlying mechanisms were explored. A comprehensive screening assay using OSI-resistant cells identified the optimal combination of biguanide compounds with OSI. Proteomics, co-immunoprecipitation mass spectrometry, RNA sequencing, and homologous recombination assays were used to elucidate the molecular mechanisms underlying combination therapy. NSCLC tumor tissues, especially OSI-resistant tissues, obtained from our clinic were used to assess the correlations between key proteins and OSI resistance. SMK-010, a highly potent biguanide compound, effectively overcame OSI resistance in vitro and in vivo. Mechanistical studies showed that BMI1/FGFR1 pathway activation is responsible for OSI resistance. Specifically, silencing BMI1 promoted NEDD4-mediated FGFR1 ubiquitination and proteasomal degradation, whereas SMK-010 treatment induced FGFR1 lysosomal degradation. This reduction in FGFR1 levels impaired homologous recombination, increased DNA damage, and surmounted OSI resistance. Analysis of clinical samples revealed overexpression of BMI1 and FGFR1 in NSCLC tissues and represented potential biomarkers for OSI resistance. These findings highlight the crucial role of the BMI1/FGFR1 axis in OSI resistance and provide a rational basis for the future clinical application of the biguanide, SMK-010, in combination with OSI.