marizomib and Adenocarcinoma

The novel proteasome inhibitor NPI-0052 has been shown to sensitize tumor cells to apoptosis by various chemotherapeutic drugs and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), although the mechanisms involved are not clear. We hypothesized that NPI-0052-mediated sensitization may result from NF-kappaB inhibition and downstream modulation of the metastasis inducer Snail and the metastasis suppressor/immunosurveillance cancer gene product Raf-1 kinase inhibitory protein (RKIP). Human prostate cancer cell lines were used as models, as they express different levels of these proteins. We show that NPI-0052 inhibits both NF-kappaB and Snail and induces RKIP expression, thus resulting in cell sensitization to CDDP and TRAIL. The direct role of NF-kappaB inhibition in sensitization was corroborated with the NF-kappaB inhibitor DHMEQ, which mimicked NPI-0052 in sensitization and inhibition of Snail and induction of RKIP. The direct role of Snail inhibition by NPI-0052 in sensitization was shown with Snail small interfering RNA, which reversed resistance and induced RKIP. Likewise, the direct role of RKIP induction in sensitization was revealed by both overexpression of RKIP (mimicking NPI-0052) and RKIP small interfering RNA that inhibited NPI-0052-mediated sensitization. These findings show that NPI-0052 modifies the NF-kappaB-Snail-RKIP circuitry in tumor cells and results in downstream inhibition of antiapoptotic gene products and chemoimmunosensitization. The findings also identified Snail and RKIP as targets for reversal of resistance.

Topics: Adenocarcinoma; Antineoplastic Agents; Apoptosis; Blotting, Western; Boronic Acids; Bortezomib; Cisplatin; Humans; Lactones; Leupeptins; Male; Melanoma; Membrane Potential, Mitochondrial; NF-kappa B; Phosphatidylethanolamine Binding Protein; Prostatic Neoplasms; Proteasome Inhibitors; Proto-Oncogene Proteins c-raf; Pyrazines; Pyrroles; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Snail Family Transcription Factors; TNF-Related Apoptosis-Inducing Ligand; Transcription Factors; Transfection; Tumor Cells, Cultured

In the current study, we investigate the activation of antiapoptotic signaling pathways in response to proteasome inhibitor treatment in pancreatic cancer and evaluate the use of concomitant inhibition of these pathways to augment proteasome inhibitor treatment responses.. Pancreatic cancer cell lines and mouse flank xenografts were treated with proteasome inhibitor alone or in combination with chemotherapeutic compounds (gemcitabine, erlotinib, and bevacizumab), induction of apoptosis and effects on tumor growth were assessed. The effect of bortezomib (a first-generation proteasome inhibitor) and NPI-0052 (a second-generation proteasome inhibitor) treatment on key pancreatic mitogenic and antiapoptotic pathways [epidermal growth factor receptor, extracellular signal-regulated kinase, and phosphoinositide-3-kinase (PI3K)/AKT] was determined and the ability of inhibitors of these pathways to enhance the effects of proteasome inhibition was assessed in vitro and in vivo.. Our data showed that proteasome inhibitor treatment activates antiapoptotic and mitogenic signaling pathways (epidermal growth factor receptor, extracellular signal-regulated kinase, c-Jun-NH2-kinase, and PI3K/AKT) in pancreatic cancer. Additionally, we found that activation of these pathways impairs tumor response to proteasome inhibitor treatment and inhibition of the c-Jun-NH2-kinase and PI3K/AKT pathways increases the antitumor effects of proteasome inhibitor treatment.. These preclinical studies suggest that targeting proteasome inhibitor-induced antiapoptotic signaling pathways in combination with proteasome inhibition may augment treatment response in highly resistant solid organ malignancies. Further evaluation of these novel treatment combinations in clinical trials is warranted.

Topics: Adenocarcinoma; Animals; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Bevacizumab; Blotting, Western; Boronic Acids; Bortezomib; Cell Line, Tumor; Cetuximab; Deoxycytidine; ErbB Receptors; Erlotinib Hydrochloride; Female; Gemcitabine; Humans; Lactones; Mice; Mice, Nude; Pancreatic Neoplasms; Phosphatidylinositol 3-Kinases; Protease Inhibitors; Proteasome Inhibitors; Pyrazines; Pyrroles; Quinazolines; Signal Transduction; Xenograft Model Antitumor Assays

In the current study, we examine the effects of a novel proteasome inhibitor, NPI-0052 (salinosporamide A), on proteasome function and nuclear factor-kappaB activation and evaluate its ability to enhance treatment response in colon cancer xenografts when administered orally.. The effects of treatment on nuclear factor-kappaB activation, cell cycle regulation, and apoptosis were determined. The pharmacodynamic effect of NPI-0052 on 20S proteasome function was assayed in vivo following oral and i.v. drug administration and compared with treatment with bortezomib. The effect of combined treatment with chemotherapy was determined in a colon cancer xenograft model.. We found that NPI-0052 is a potent, well-tolerated proteasome inhibitor that has pharmacodynamic properties distinct from bortezomib in that it achieves significantly higher and more sustained levels of proteasome inhibition. When combined with chemotherapy, NPI-0052 increases apoptosis and shifts cells toward G2 cell cycle arrest. When added to chemotherapy in vivo [using combinations of 5-fluorouracil (5-FU), CPT-11, Avastin (bevacizumab), leucovorin, and oxaliplatin], NPI-0052 significantly improved the tumoricidal response and resulted in a 1.8-fold increased response to CPT-11, 5-FU, and leucovorin triple-drug combination (P=0.0002, t test), a 1.5-fold increased response to the oxaliplatin, 5-FU, and leucovorin triple-drug combination (P=0.013, t test), and a 2.3-fold greater response to the CPT-11, 5-FU, leucovorin, and Avastin regimen (P=0.00057).. The high level of proteasome inhibition achieved by NPI-0052 is well tolerated and significantly improves the tumoricidal response to multidrug treatment in a colon cancer xenograft model. Further evaluation of this novel proteasome inhibitor in clinical trials is indicated.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Boronic Acids; Bortezomib; Cell Cycle; Colonic Neoplasms; Drug Administration Routes; Drug Synergism; Female; Humans; Lactones; Mice; Mice, Nude; NF-kappa B; Proteasome Endopeptidase Complex; Pyrazines; Pyrroles; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha; Xenograft Model Antitumor Assays

Topics: Actinomycetales; Adenocarcinoma; Colonic Neoplasms; Crystallography, X-Ray; Cysteine Endopeptidases; Humans; Inhibitory Concentration 50; Lactones; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Structure; Multienzyme Complexes; Protease Inhibitors; Proteasome Endopeptidase Complex; Pyrroles; Tumor Cells, Cultured