A dominant-negative F-box deleted mutant of E3 ubiquitin ligase, ?-TrCP1/FWD1, markedly reduces myeloma cell growth and survival in mice.

ABSTRACT: Treatment of multiple myeloma with bortezomib can result in severe adverse effects, necessitating the development of targeted inhibitors of the proteasome. We show that stable expression of a dominant-negative F-box deleted (â??F) mutant of the E3 ubiquitin ligase, SCF?-TrCP/FWD1, in murine 5TGM1 myeloma cells dramatically attenuated their skeletal engraftment and survival when inoculated into immunocompetent C57BL/KaLwRij mice. Similar results were obtained in immunodeficient bg-nu-xid mice, suggesting that the observed effects were independent of host recipient immune status. Bone marrow stroma offered no protection for 5TGM1-â??F cells in cocultures treated with tumor necrosis factor (TNF), indicating a cell-autonomous anti-myeloma effect. Levels of p100, I?B?, Mcl-1, ATF4, total and cleaved caspase-3, and phospho-?-catenin were elevated in 5TGM1-â??F cells whereas cIAP was down-regulated. TNF also activated caspase-3 and downregulated Bcl-2, correlating with the enhanced susceptibility of 5TGM1-â??F cells to apoptosis. Treatment of 5TGM1 tumor-bearing mice with a ?-TrCP1/FWD1 inhibitor, pyrrolidine dithiocarbamate (PDTC), significantly reduced tumor burden in bone. PDTC also increased levels of cleaved Mcl-1 and caspase-3 in U266 human myeloma cells, correlating with our murine data and validating the development of specific ?-TrCP inhibitors as an alternative therapy to nonspecific proteasome inhibitors for myeloma patients.

SUBMITTER: Sharma R 

PROVIDER: S-EPMC4673288 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature