Discovery of berberine that targetedly induce autophagic degradation of both BCR-ABL and BCR-ABL T315I through recruiting LRSAM1 for overcoming imatinib-resistance

Purpose: Imatinib, the breakpoint cluster region protein (BCR)/Abelson murine leukemia viral oncogene homolog (ABL) inhibitor, is widely used to treat chronic myeloid leukemia (CML). However, imatinib resistance develops in many patients. Therefore, new drugs with improved therapeutic effects are urgently needed. Berberine (BBR) is a potent BCR-ABL inhibitor for imatinib-sensitive and -resistant CML. Experimental Design: Protein structure analysis and virtual screening were used to identify BBR targets in CML. Molecular docking analysis, surface plasmon resonance imaging (SPRi), nuclear magnetic resonance (NMR) assays, and thermoshift assays were performed to confirm the BBR target. The change in BCR-ABL protein expression after BBR treatment was assessed by western blotting. The effects of BBR were assessed in vitro in cell lines, in vivo in mice, and in human CML bone marrow cells as a potential strategy to overcome imatinib resistance. Results: We discovered that BBR bound to the protein tyrosine kinase (PTK) domain of BCR-ABL. BBR inhibited the activity of BCR-ABL and BCR-ABL with the T315I mutation, and it also degraded these proteins via the autophagic lysosome pathway by recruiting E3 ubiquitin-protein ligase LRSAM1. BBR inhibited the cell viability and colony formation of CML cells and prolonged survival in CML mouse models with imatinib sensitivity and resistance. Conclusions: The results show that BBR directly binds to and degrades BCR-ABL and BCR-ABL T315I via the autophagic lysosome pathway by recruiting LRSAM1. The use of BBR is a new strategy to improve the treatment of CML patients with imatinib sensitivity or resistance.