TAT-mediated intracellular delivery of NPM-derived peptide induces apoptosis in leukemic cells and suppresses leukemogenesis in mice

Nucleophosmin (NPM) is frequently over-expressed in leukemias and other tumors. NPM has been reported to suppress oncogene-induced senescence and apoptosis and may represent a therapeutic target for cancer. We fused a NPM-derived peptide to the HIV-TAT (TAT-NPM Delta C) and found that the fusion peptide inhibited proliferation and induced apoptotic death of primary fibroblasts and preleukemic stem cells. TAT-NPM Delta C down-regulated several NF-kappa B-controlled survival and inflammatory proteins and suppressed NF-kappa B-driven reporter gene activities. Using an inflammation-associated leukemia model, we demonstrate that TAT-NPM Delta C induced proliferative suppression and apoptosis of preleukemic stem cells and significantly delayed leukemic development in mice. Mechanistically, TAT-NPM Delta C associated with wild-type NPM proteins and formed complexes with endogenous NPM and p65 at promoters of several antiapoptotic and inflammatory genes and abrogated their transactivation by NF-kappa B in leukemic cells. Thus, TAT-delivered NPM peptide may provide a novel therapy for inflammation-associated tumors that require NF-kappa B signaling for survival.