Cutaneous T-cell lymphoma (CTCL) is characterized by constitutive activation of nuclear factor kB (NF-kB), which plays a crucial role in the survival of CTCL cells and their resistance to apoptosis. NF-kB activity in CTCL is inhibited by the proteasome inhibitor bortezomib; however, the mechanisms remained unknown. In this study, we investigated mechanisms by which bortezomib suppresses NF-kB activity in CTCL Hut-78 cells. We demonstrate that bortezomib and MG132 suppress NF-kB activity in Hut-78 cells by a novel mechanism that consists of inducing nuclear translocation and accumulation of IkBa (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha), which then associates with NF-kB p65 and p50 in the nucleus and inhibits NF-kB DNA binding activity. Surprisingly, however, while expression of NF-kB-dependent antiapoptotic genes cIAP1 and cIAP2 is inhibited by bortezomib, expression of Bcl-2 is not suppressed. Chromatin immunoprecipitation indicated that cIAP1 and cIAP2 promoters are occupied by NF-kB p65/50 heterodimers, whereas Bcl-2 promoter is occupied predominantly by p50/50 homodimers. Collectively, our data reveal a novel mechanism of bortezomib function in CTCL and suggest that the inhibition of NF-kB-dependent gene expression by bortezomib is gene specific and depends on the subunit composition of NF-kB dimers recruited to NF-kB-responsive promoters. Mol Cancer Res; 9(2); 183-94. Ó2011 AACR.

Extracellular matrix (ECM) degrading matrix metalloproteinases (MMPs) lead to ECM turnover, a key event in cancer growth and progression. The tissue inhibitors of matrix metalloproteinases (TIMPs) limit the activity of MMPs, which suggests their use for cancer gene therapy. Here we report that systemic administration of naked TIMP-4 DNA signi®cantly inhibited Wilms' tumor growth in nude mice. TIMP-4, whose expression was lost in Wilms' tumor, inhibited the growth of G401 Wilms' tumor cells at a concentration lower than those required for MMP inhibition. This inhibition was associated with internalization of exogenous recombinant TIMP-4. Electroporation-mediated intramuscular injection of TIMP-4 expression plasmid resulted in sustained plasma TIMP-4 levels and signi®cant tumor suppression. Our data demonstrate a tumor suppressive eect of TIMP-4 against Wilms' tumor and the potential utility of intramuscular delivery of TIMP gene for treatment of kidney derived cancers. Oncogene (2001) 20, 4337 ± 4343.