Nimbolide targets BCL2 and induces apoptosis in preclinical models of Waldenströms macroglobulinemia.
Neem leaf extract (NLE) has medicinal properties, which have been attributed to its limonoid content. We identified the NLE tetranorterpenoid, nimbolide, as being the key limonoid responsible for the cytotoxicity of NLE in various preclinical models of human B-lymphocyte cancer. Of the models tested, Waldenströms macroglobulinemia (WM) cells were most sensitive to nimbolide, undergoing significant mitochondrial mediated apoptosis. Notably, nimbolide toxicity was also observed in drug-resistant (bortezomib or ibrutinib) WM cells. To identify putative targets of nimbolide, relevant in WM, we used chemoinformatics-based approaches comprised of virtual in silico screening, molecular modeling and target-ligand reverse docking. In silico analysis revealed the antiapoptotic protein BCL2 was the preferential binding partner of nimbolide. The significance of this finding was further tested in vitro in RS4;11 (BCL2-dependent) tumor cells, in which nimbolide induced significantly more apoptosis compared with BCL2 mutated (Jurkat BCL2(Ser70-Ala)) cells. Lastly, intraperitoneal administration of nimbolide in WM tumor xenografted mice, significantly reduced tumor growth and IgM secretion in vivo, while modulating the expression of several proteins as seen on immunohistochemistry. Overall, our data demonstrate that nimbolide is highly active in WM cells, as well as other B-cell cancers, and engages BCL2 to exert its cytotoxic activity.
Department of Cancer Biology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Chitta
Department of Cancer Biology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Paulus
Department of Molecular Neuroscience, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Caulfield
Department of Cancer Biology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Akhtar
Department of Cancer Biology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Blake
Division of Hematology and Oncology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Ailawadhi
Department of Cancer Biology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Knight
Department of Health Science Research, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Heckman
Conrad Prebys Center for Chemical Genomics at Sanford-Burnham Medical Research Institute, La Jolla, CA, USA.
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Pinkerton
Division of Hematology and Oncology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, USA.
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Chanan-Khan
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D019169:Jurkat Cells; D036701:Limonins / Q000494:pharmacology*; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008258:Waldenstrom Macroglobulinemia / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D023041:Xenograft Model Antitumor Assays
C000595707:BCL2 protein, human; D036701:Limonins; D019253:Proto-Oncogene Proteins c-bcl-2; C042198:nimbolide