NAMPT Over-Expression Recapitulates the BRAF Inhibitor Resistant Phenotype Plasticity in Melanoma
Author(s)
Audrito, Valentina; Messana, Vincenzo Gianluca; Moiso, Enrico; Vitale, Nicoletta; Arruga, Francesca; Brandimarte, Lorenzo; Gaudino, Federica; Pellegrino, Elisa; Vaisitti, Tiziana; Riganti, Chiara; Piva, Roberto; Deaglio, Silvia; ... Show more Show less![Thumbnail](/bitstream/handle/1721.1/131328/cancers-12-03855-v3.pdf.jpg?sequence=5&isAllowed=y)
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Serine–threonine protein kinase B-RAF <b>(</b><i>BRAF)</i>-mutated metastatic melanoma (MM) is a highly aggressive type of skin cancer. Treatment of MM patients using BRAF/MEK inhibitors (BRAFi/MEKi) eventually leads to drug resistance, limiting any clinical benefit. Herein, we demonstrated that the nicotinamide adenine dinucleotide (NAD)-biosynthetic enzyme nicotinamide phosphoribosyltransferase (NAMPT) is a driving factor in BRAFi resistance development. Using stable and inducible NAMPT over-expression systems, we showed that forced NAMPT expression in MM <i>BRAF</i>-mutated cell lines led to increased energy production, MAPK activation, colony-formation capacity, and enhance tumorigenicity in vivo. Moreover, NAMPT over-expressing cells switched toward an invasive/mesenchymal phenotype, up-regulating expression of ZEB1 and TWIST, two transcription factors driving the epithelial to mesenchymal transition (EMT) process. Consistently, within the NAMPT-overexpressing cell line variants, we observed an increased percentage of a rare, drug-effluxing stem cell-like side population (SP) of cells, paralleled by up-regulation of ABCC1/MRP1 expression and CD133-positive cells. The direct correlation between NAMPT expression and gene set enrichments involving metastasis, invasiveness and mesenchymal/stemness properties were verified also in melanoma patients by analyzing The Cancer Genome Atlas (TCGA) datasets. On the other hand, CRISPR/Cas9 full knock-out <i>NAMPT</i> BRAFi-resistant MM cells are not viable, while inducible partial silencing drastically reduces tumor growth and aggressiveness. Overall, this work revealed that NAMPT over-expression is both necessary and sufficient to recapitulate the BRAFi-resistant phenotype plasticity.
Date issued
2020-12-20Department
Koch Institute for Integrative Cancer Research at MITPublisher
Multidisciplinary Digital Publishing Institute
Citation
Cancers 12 (12): 3855 (2020)
Version: Final published version