Interactions between the proteasome inhibitor carfilzomib and the HDAC inhibitors vorinostat and SNDX-275 were examined in mantle cell lymphoma (MCL) cells in vitro and in vivo. Co-administration of very low, marginally toxic carfilzomib concentrations (e.g., 3–4 nM) with minimally lethal vorinostat or SNDX-275 concentrations induced sharp increases in mitochondrial injury and apoptosis in multiple MCL cell lines and primary MCL cells. Enhanced lethalitly was associated with JNK1/2 activation, increased DNA damage (induction of λH2A.X), and ERK1/2 and AKT1/2 inactivation. Co-administration of carfilzomib and HDACIs induced a marked increase in ROS generation, and G2M arrest. Significantly, the free radical scavenger TBAP blocked carfilzomib/HDACI-mediated ROS generation, λH2A.X formation, JNK1/2 activation, and lethality. Genetic (shRNA) knock down of JNK1/2 significantly attenuated carfilzomib/HDACI-induced apoptosis, but did not prevent ROS generation or DNA damage. Carfilzomib/HDACI regimens were also active against bortezomib-resistant MCL cells. Finally, carfilzomib/vorinostat co-administrationo resulted in a pronounced reduction in tumor growth compared to single agent treatment in a MCL xenograft model associated with enhanced apoptosis, λH2A.X formation, and JNK activation. Collectively, these findings suggest that carfilzomib/HDACI regimens warrants attention in MCL.

Human papillomaviruses (HPVs) are causative agents in almost all cervical carcinomas. HPVs are also causative agents in head and neck cancer, the cases of which are increasing rapidly. Viral replication activates the DNA damage response (DDR) pathway; associated proteins are recruited to replication foci, and this pathway may serve to allow for viral genome amplification. Likewise, HPV genome double-strand breaks (DSBs) could be produced during replication and could lead to linearization and viral integration. Many studies have shown that viral integration into the host genome results in unregulated expression of the viral oncogenes, E6 and E7, promoting HPV-induced carcinogenesis. Previously, we have demonstrated that DNA-damaging agents, such as etoposide, or knocking down viral replication partner proteins, such as topoisomerase II β binding protein I (TopBP1), does not reduce the level of DNA replication. Here, we investigated whether these treatments alter the quality of DNA replication by HPV16 E1 and E2. We confirm that knockdown of TopBP1 or treatment with etoposide does not reduce total levels of E1/E2-mediated DNA replication; however, the quality of replication is significantly reduced. The results demonstrate that E1 and E2 continue to replicate under genomically-stressed conditions and that this replication is mutagenic. This mutagenesis would promote the formation of substrates for integration of the viral genome into that of the host, a hallmark of cervical cancer.

Interactions between the the irreversible proteasome inhibitor carfilzomib (CFZ) and the pan-BH3 mimetic obatoclax (Obato) were examined in GC- and ABC-DLBCL cells. Co-treatment with minimally toxic concentrations of CFZ (i.e., 2–6 nM) and sub-toxic concentrations of obato (0.05–2.0μM) synergistically increased apoptosis in multiple DLBCL cell lines and increased lethality toward primary human DLBCL but not normal CD34+ cells. Synergistic interactions were associated with sharp increases in caspase-3 activation, PARP cleavage, phospho-JNK induction, up-regulation of Noxa, and AKT dephosphorylation. Combined treatment also diminished CFZ-mediated Mcl-1 up-regulation while immunoprecipitation analysis revealed reduced associations between Bak and Mcl-1/Bcl-xL, and Bim and Mcl-1. The CFZ/Obato regimen triggered translocation, conformational change and dimerization of Bax and activation of Bak. Genetic interruption of JNK and Noxa by shRNA knockdown, ectopic Mcl-1 expression, or enforced activation of AKT significantly attenuated CFZ/Obato-mediated apoptosis. Notably, co-administration of CFZ/Obato sharply increased apoptosis in multiple bortezomib-resistant DLBCL models. Finally, in vivo administration of CFZ and Obato to mice inoculated with SUDHL4 cells substantially suppressed tumor growth, activated JNK, inactivated AKT, and increased survival compared to the effects of single agent treatment. Together, these findings argue that a strategy combining CFZ and Obato warrants attention in DLBCL.

determined that Girija Dasmahapatra, the first author of the above-mentioned article, engaged in research misconduct by falsifying and/or fabricating data that appeared in the 2012 article (2). Specifically, respondent reused, and/or relabeled Western blot panels and mouse images and claimed they represented different controls and/or experimental results in: Figs. 3A (JNK and Tubulin), 3B (Tubulin-scram), 3D (Tubulin-pUSE-AKT cl.3), and 6B (CFZ þ obato; ref. 2). The matter was reviewed by members of the AACR Publications staff and the MCT editors, who agree that the figure manipulation present in the article merits retraction.

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<p>PDF file - 117K</p>

<div>Abstract<p>Interactions between the irreversible proteasome inhibitor carfilzomib and the pan-BH3 mimetic obatoclax were examined in germinal center (GC)- and activated B-cell–diffuse large B-cell lymphoma (ABC-DLBCL) cells. Cotreatment with minimally toxic concentrations of carfilzomib (i.e., 2–6 nmol/L) and subtoxic concentrations of obatoclax (0.05–2.0 μmol/L) synergistically increased apoptosis in multiple DLBCL cell lines and increased lethality toward primary human DLBCL but not normal CD34⁺ cells. Synergistic interactions were associated with sharp increases in caspase-3 activation, PARP cleavage, p-JNK induction, upregulation of Noxa, and AKT dephosphorylation. Combined treatment also diminished carfilzomib-mediated Mcl-1 upregulation whereas immunoprecipitation analysis revealed reduced associations between Bak and Mcl-1/Bcl-xL and Bim and Mcl-1. The carfilzomib/obatoclax regimen triggered translocation, conformational change, and dimerization of Bax and activation of Bak. Genetic interruption of c-<i>jun</i>-NH₂-kinase (JNK) and Noxa by short hairpin RNA knockdown, ectopic Mcl-1 expression, or enforced activation of AKT significantly attenuated carfilzomib/obatoclax-mediated apoptosis. Notably, coadministration of carfilzomib/obatoclax sharply increased apoptosis in multiple bortezomib-resistant DLBCL models. Finally, <i>in vivo</i> administration of carfilzomib and obatoclax to mice inoculated with SUDHL4 cells substantially suppressed tumor growth, activated JNK, inactivated AKT, and increased survival compared with the effects of single-agent treatment. Together, these findings argue that a strategy combining carfilzomib and obatoclax warrants attention in DLBCL. <i>Mol Cancer Ther; 11(5); 1122–32. ©2012 AACR</i>.</p></div>

<div>Abstract<p>Interactions between the proteasome inhibitor carfilzomib and the histone deacetylase (HDAC) inhibitors vorinostat and SNDX-275 were examined in mantle cell lymphoma (MCL) cells <i>in vitro</i> and <i>in vivo</i>. Coadministration of very low, marginally toxic carfilzomib concentrations (e.g., 3–4 nmol/L) with minimally lethal vorinostat or SNDX-275 concentrations induced sharp increases in mitochondrial injury and apoptosis in multiple MCL cell lines and primary MCL cells. Enhanced lethality was associated with c-<i>jun</i>-NH,-kinase (JNK) 1/2 activation, increased DNA damage (induction of λH2A.X), and ERK1/2 and AKT1/2 inactivation. Coadministration of carfilzomib and histone deacetylase inhibitors (HDACI) induced a marked increase in reactive oxygen species (ROS) generation and G₂–M arrest. Significantly, the free radical scavenger tetrakis(4-benzoic acid) porphyrin (TBAP) blocked carfilzomib/HDACI-mediated ROS generation, λH2A.X formation, JNK1/2 activation, and lethality. Genetic (short hairpin RNA) knockdown of JNK1/2 significantly attenuated carfilzomib/HDACI-induced apoptosis, but did not prevent ROS generation or DNA damage. Carfilzomib/HDACI regimens were also active against bortezomib-resistant MCL cells. Finally, carfilzomib/vorinostat coadministration resulted in a pronounced reduction in tumor growth compared with single agent treatment in an MCL xenograft model associated with enhanced apoptosis, λH2A.X formation, and JNK activation. Collectively, these findings suggest that carfilzomib/HDACI regimens warrant attention in MCL. <i>Mol Cancer Ther; 10(9); 1686–97. ©2011 AACR</i>.</p></div>