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Cea, Michele,Cagnetta, Antonia,Fulciniti, Mariateresa,Tai, Yu-Tzu,Hideshima, Teru,Chauhan, Dharminder,Roccaro, Aldo,Sacco, Antonio,Calimeri, Teresa,Cottini, Francesca,Jakubikova, Jana,Kong, Sun-Young American Society of Hematology 2012 Blood Vol.120 No.17
<B>Abstract</B><P>Malignant cells have a higher nicotinamide adenine dinucleotide (NAD+) turnover rate than normal cells, making this biosynthetic pathway an attractive target for cancer treatment. Here we investigated the biologic role of a rate-limiting enzyme involved in NAD+ synthesis, Nampt, in multiple myeloma (MM). Nampt-specific chemical inhibitor FK866 triggered cytotoxicity in MM cell lines and patient MM cells, but not normal donor as well as MM patients PBMCs. Importantly, FK866 in a dose-dependent fashion triggered cytotoxicity in MM cells resistant to conventional and novel anti-MM therapies and overcomes the protective effects of cytokines (IL-6, IGF-1) and bone marrow stromal cells. Nampt knockdown by RNAi confirmed its pivotal role in maintenance of both MM cell viability and intracellular NAD+ stores. Interestingly, cytotoxicity of FK866 triggered autophagy, but not apoptosis. A transcriptional-dependent (TFEB) and independent (PI3K/mTORC1) activation of autophagy mediated FK866 MM cytotoxicity. Finally, FK866 demonstrated significant anti-MM activity in a xenograft-murine MM model, associated with down-regulation of ERK1/2 phosphorylation and proteolytic cleavage of LC3 in tumor cells. Our data therefore define a key role of Nampt in MM biology, providing the basis for a novel targeted therapeutic approach.</P>
Tai, Yu-Tzu,Chang, Betty Y.,Kong, Sun-Young,Fulciniti, Mariateresa,Yang, Guang,Calle, Yolanda,Hu, Yiguo,Lin, Jianhong,Zhao, Jian-Jun,Cagnetta, Antonia,Cea, Michele,Sellitto, Michael A.,Zhong, Mike Y. American Society of Hematology 2012 Blood Vol.120 No.9
<B>Abstract</B><P>Bruton tyrosine kinase (Btk) has a well-defined role in B-cell development, whereas its expression in osteoclasts (OCs) further suggests a role in osteoclastogenesis. Here we investigated effects of PCI-32765, an oral and selective Btk inhibitor, on osteoclastogenesis as well as on multiple myeloma (MM) growth within the BM microenvironment. PCI-32765 blocked RANKL/M-CSF-induced phosphorylation of Btk and downstream PLC-γ2 in OCs, resulting in diminished TRAP5b (ED50 = 17nM) and bone resorption activity. PCI-32765 also inhibited secretion of multiple cytokines and chemokines from OC and BM stromal cell cultures from both normal donors (ED50 = 0.5nM) and MM patients. It decreased SDF-1-induced migration of MM cells, and down-regulated MIP1-α/CCL3 in MM cells. It also blocked MM cell growth and survival triggered by IL-6 or coculture with BM stromal cells or OCs in vitro. Importantly, PCI-32765 treatment significantly inhibits in vivo MM cell growth (P < .03) and MM cell-induced osteolysis of implanted human bone chips in SCID mice. Moreover, PCI-32765 prevents in vitro colony formation by stem-like cells from MM patients. Together, these results delineate functional sequelae of Btk activation mediating osteolysis and growth of MM cells, supporting evaluation of PCI-32765 as a novel therapeutic in MM.</P>