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Hu Q, Chang X, Yan R, Rong C, Yang C, Cheng S, Gu X, Yao H, Hou X, Mo Y, Zhao L, Chen Y, Dinlin X, Wang Q, Fang S. (-)-Epigallocatechin-3-gallate induces cancer cell apoptosis via acetylation of amyloid precursor protein. Med Oncol 2014; 32:390. [PMID: 25452172 DOI: 10.1007/s12032-014-0390-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2014] [Accepted: 11/18/2014] [Indexed: 11/29/2022]
Abstract
Epigenetic modifications are involved in cancer pathogenesis, and HDACis are considered potential therapeutic agents. We and others have shown the inhibitory activity of EGCG on HDAC1. But little is known about the effect of EGCG as on epigenetic regulation in cancer. Here, we try to demonstrate that EGCG acts as an HDACi downregulated APP expression, which was pathophysiologically upregulated in cancers and exerts a key role in cancer cell growth. We used PC-12 cells, SK-N-SH cells and primary tumor tissues for our analysis. Male 4-week-old athymic nude mice were used for heterotopic tumor growth assay. We employed Western blotting analysis to detect Bcl-2, Bax, APP, caspase-3, caspase-7, HDAC1 and H4Ac. We used AnnexinV-FITC and TUNEL staining for apoptosis detection. Tumor tissues were examined by immunohistochemical staining. We demonstrated that EGCG suppresses the growth of xenografted adrenal pheochromocytoma. Flow cytometry analysis and TUNEL staining showed that EGCG induced the apoptosis. Treatment with EGCG resulted in decrease in Bcl-2 but increase in Bax and activated caspase-3 and caspase-7. HDAC inhibitor EGCG leaded to hyperacetylated histone H4 by immunofluorescence. EGCG decreased APP levels by immunofluorescence staining and Western blot analysis. Silencing specific to HDAC1 leaded to caspase-3 and caspase-7 activation and cleavage. Our results are the first to demonstrate a functional interaction between EGCG and APP in suppression tumor growth, and provide a new epigenetic effects of EGCG on antitumor.
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Affiliation(s)
- Qian Hu
- Department of Oncology, Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University, Guangzhou, 510120, China
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Muscal JA, Thompson PA, Horton TM, Ingle AM, Ahern CH, McGovern RM, Reid JM, Ames MM, Espinoza-Delgado I, Weigel BJ, Blaney SM. A phase I trial of vorinostat and bortezomib in children with refractory or recurrent solid tumors: a Children's Oncology Group phase I consortium study (ADVL0916). Pediatr Blood Cancer 2013; 60:390-5. [PMID: 22887890 PMCID: PMC3511610 DOI: 10.1002/pbc.24271] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 07/03/2012] [Indexed: 12/22/2022]
Abstract
BACKGROUND A pediatric Phase I trial was performed to determine the maximum-tolerated dose, dose-limiting toxicities (DLTs), and pharmacokinetics (PK) of vorinostat and bortezomib, in patients with solid tumors. PROCEDURE Oral vorinostat was administered on days 1-5 and 8-12 of a 21-day cycle (starting dose 180 mg/m(2) /day with dose escalations to 230 and 300 mg/m(2) /day). Bortezomib (1.3 mg/m(2) i.v.) was administered on days 1, 4, 8, and 11 of the same cycle. PK and correlative biology studies were performed during Cycle 1. RESULTS Twenty-three eligible patients [17 male, median age 12 years (range: 1-20)] were enrolled of whom 17 were fully evaluable for toxicity. Cycle 1 DLTs that occurred in 2/6 patients at dose level 3 (vorinostat 300 mg/m(2) /day) were Grade 2 sensory neuropathy that progressed to Grade 4 (n = 1) and Grade 3 nausea and anorexia (n = 1). No objective responses were observed. There was wide interpatient variability in vorinostat PK parameters. Bortezomib disposition was best described by a three-compartment model that demonstrated rapid distribution followed by prolonged elimination. We did not observe a decrease in nuclear factor-κB activity or Grp78 induction after bortezomib treatment in peripheral blood mononuclear cells from solid tumor patients. CONCLUSION The recommended Phase 2 dose and schedule is vorinostat (230 mg/m(2) /day PO on days 1-5 and 8-12) in combination with bortezomib (1.3 mg/m(2) /day i.v. on days 1, 4, 8, and 11 of a 21-day cycle) in children with recurrent or refractory solid tumors.
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Affiliation(s)
- Jodi A. Muscal
- Texas Children’s Cancer Center and Department of Pediatrics, Baylor College of Medicine, Houston, TX
| | - Patrick A. Thompson
- Texas Children’s Cancer Center and Department of Pediatrics, Baylor College of Medicine, Houston, TX
| | - Terzah M. Horton
- Texas Children’s Cancer Center and Department of Pediatrics, Baylor College of Medicine, Houston, TX
| | | | | | | | - Joel M. Reid
- Department of Oncology, Mayo Clinic, Rochester, MN
| | | | - Igor Espinoza-Delgado
- Cancer Therapy Evaluation Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, Bethesda, MD
| | - Brenda J. Weigel
- Department of Pediatrics, Hematology-Oncology, University of Minnesota, Minneapolis, MN
| | - Susan M. Blaney
- Texas Children’s Cancer Center and Department of Pediatrics, Baylor College of Medicine, Houston, TX
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Tanaka T. Preclinical cancer chemoprevention studies using animal model of inflammation-associated colorectal carcinogenesis. Cancers (Basel) 2012; 4:673-700. [PMID: 24213461 PMCID: PMC3712717 DOI: 10.3390/cancers4030673] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 06/14/2012] [Accepted: 07/06/2012] [Indexed: 12/21/2022] Open
Abstract
Inflammation is involved in all stages of carcinogenesis. Inflammatory bowel disease, such as ulcerative colitis and Crohn’s disease is a longstanding inflammatory disease of intestine with increased risk for colorectal cancer (CRC). Several molecular events involved in chronic inflammatory process are reported to contribute to multi-step carcinogenesis of CRC in the inflamed colon. They include over-production of free radicals, reactive oxygen and nitrogen species, up-regulation of inflammatory enzymes in arachidonic acid biosynthesis pathway, up-regulation of certain cytokines, and intestinal immune system dysfunction. In this article, firstly I briefly introduce our experimental animal models where colorectal neoplasms rapidly develop in the inflamed colorectum. Secondary, data on preclinical cancer chemoprevention studies of inflammation-associated colon carcinogenesis by morin, bezafibrate, and valproic acid, using this novel inflammation-related colorectal carcinogenesis model is described.
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Affiliation(s)
- Takuji Tanaka
- Cytopatholgy Division, Tohkai Cytopathology Institute, Cancer Research and Prevention (TCI-CaRP), 5-1-2 Minami-uzura, Gifu 500-8285, Japan.
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Fung KYC, Lewanowitsch T, Henderson ST, Priebe I, Hoffmann P, McColl SR, Lockett T, Head R, Cosgrove LJ. Proteomic analysis of butyrate effects and loss of butyrate sensitivity in HT29 colorectal cancer cells. J Proteome Res 2009; 8:1220-7. [PMID: 19195990 DOI: 10.1021/pr8009929] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Butyrate, a fermentation product of the large bowel microflora, is potentially protective against the development of colorectal cancer. In vitro, butyrate has been shown to induce apoptosis and inhibit proliferation in numerous cancer cell lines, including colorectal cancer. Although these tumor suppressing properties of butyrate are well-documented in experimental systems, the mechanisms underlying the induction of these effects are not fully understood. Understanding these mechanisms in cancer cells, as well as the pathways involved in a cell's ability to overcome them and progress toward malignancy, is vital to determine therapeutic approaches for disease management. We have developed a colorectal cancer cell line (HT29-BR) that is less responsive to the apoptotic effects of butyrate through sustained exposure of HT29 cells to 5 mM butyrate and have used proteomics to investigate the mechanisms involved in the development of butyrate insensitivity. Proteomic analysis identified a number of cellular processes in HT29 and HT29-BR cells influenced by butyrate including remodeling of the actin cytoskeleton, inhibition of protein biosynthesis and dysregulation of the cell stress response. We describe novel roles for butyrate in the induction of its tumor suppressing effects and outline potential cellular pathways involved in the development of butyrate insensitivity in the HT29-BR cell population.
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Affiliation(s)
- Kim Y C Fung
- CSIRO Preventative Health Flagship, Australia, CSIRO, Human Nutrition, Adelaide, Australia, CSIRO, Division of Molecular and Health Technologies, Adelaide, Australia
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Drexler HCA. Synergistic apoptosis induction in leukemic cells by the phosphatase inhibitor salubrinal and proteasome inhibitors. PLoS One 2009; 4:e4161. [PMID: 19129918 PMCID: PMC2613525 DOI: 10.1371/journal.pone.0004161] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 12/06/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Cells adapt to endoplasmic reticulum (ER)-stress by arresting global protein synthesis while simultaneously activating specific transcription factors and their downstream targets. These processes are mediated in part by the phosphorylation-dependent inactivation of the translation initiation factor eIF2alpha. Following restoration of homeostasis protein synthesis is resumed when the serine/threonine-protein phosphatase PP1 dephosphorylates and reactivates eIF2alpha. Proteasome inhibitors, used to treat multiple myeloma patients evoke ER-stress and apoptosis by blocking the ER-associated degradation of misfolded proteins (ERAD), however, the role of eIF2alpha phosphorylation in leukemic cells under conditions of proteasome inhibitor-mediated ER stress is currently unclear. METHODOLOGY AND PRINCIPAL FINDINGS Bcr-Abl-positive and negative leukemic cell lines were used to investigate the functional implications of PP1-related phosphatase activities on eIF2alpha phosphorylation in proteasome inhibitor-mediated ER stress and apoptosis. Rather unexpectedly, salubrinal, a recently identified PP1 inhibitor capable to protect against ER stress in various model systems, strongly synergized with proteasome inhibitors to augment apoptotic death of different leukemic cell lines. Salubrinal treatment did not affect the phosphorlyation status of eIF2alpha. Furthermore, the proapoptotic effect of salubrinal occurred independently from the chemical nature of the proteasome inhibitor, was recapitulated by a second unrelated phosphatase inhibitor and was unaffected by overexpression of a dominant negative eIF2alpha S51A variant that can not be phosphorylated. Salubrinal further aggravated ER-stress and proteotoxicity inflicted by the proteasome inhibitors on the leukemic cells since characteristic ER stress responses, such as ATF4 and CHOP synthesis, XBP1 splicing, activation of MAP kinases and eventually apoptosis were efficiently abrogated by the translational inhibitor cycloheximide. CONCLUSIONS Although PP1 activity does not play a major role in regulating the ER stress response in leukemic cells, phosphatase signaling nevertheless significantly limits proteasome inhibitor-mediated ER-stress and apoptosis. Inclusion of specific phosphatase inhibitors might therefore represent an option to improve current proteasome inhibitor-based treatment modalities for hematological cancers.
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Affiliation(s)
- Hannes C A Drexler
- Department of Vascular Cell Biology, Max Planck Institute for Molecular Biomedicine, Muenster, Germany.
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Abstract
After in vitro maturation, the unfertilized pig oocytes underwent the process called ageing. This process involves typical events such as fragmentation, spontaneous parthenogenetic activation or lysis. Inhibition of histone deacetylase, using its specific inhibitor trichostatin A (TSA), significantly delayed the maturation of pig oocytes cultured in vitro. The ageing of oocytes matured under the effect of TSA is the same as the ageing in oocytes matured without TSA. The inhibition of histone deacetylase during oocyte ageing significantly reduced the percentage of fragmented oocytes (from 30% in untreated oocytes to 9% in oocytes aged under the effect of 100 nM of TSA). Oocytes matured in vitro and subsequently aged for 1 day under the effects of TSA retained their developmental capacity. After parthenogenetic activation, a significantly higher portion (27% vs. 15%) of oocytes developed to the blastocyst stage after 24 h ageing under 100 nM TSA when compared with oocytes activated after 24 h ageing in a TSA-free medium. The parthenogenetic development in oocytes aged under TSA treatment is similar to the development of fresh oocytes (29% of blastocyst) artificially activated immediately after in vitro maturation.
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Myc regulates aggresome formation, the induction of Noxa, and apoptosis in response to the combination of bortezomib and SAHA. Blood 2008; 112:2917-26. [PMID: 18641367 DOI: 10.1182/blood-2007-12-130823] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The histone deacetylase inhibitor SAHA enhances cell death stimulated by the proteasome inhibitor bortezomib (BZ) by disrupting BZ-induced aggresome formation. Here we report that Myc regulates the sensitivity of multiple myeloma (MM) cells to BZ + SAHA-induced cell death. In MM cells, Myc expression directly correlated with intracellular ER content, protein synthesis rates, the percentage of aggresome-positive cells, and the sensitivity to BZ + SAHA-induced cell death. Accordingly, Myc knockdown markedly reduced the sensitivity of MM cells to BZ + SAHA-mediated apoptosis. Furthermore, activation of Myc was sufficient to provoke aggresome formation and thus sensitivity to BZ + SAHA, and these responses required de novo protein synthesis. BZ + SAHA-mediated stimulation of apoptosis includes the induction of the proapoptotic BH3-only protein Noxa as well as endoplasmic reticular stress, a disruption of calcium homeostasis, and activation of capase-4. Finally, knockdown studies demonstrated that both caspase-4 and Noxa play significant roles in Myc-driven sensitivity to BZ + SAHA-induced apoptosis. Collectively, our results establish a mechanistic link between Myc activity, regulation of protein synthesis, increases in HDAC6 expression and aggresome formation, induction of Noxa, and sensitivity to BZ + SAHA-induced apoptosis. These data suggest that MM patients with elevated Myc activity may be particularly sensitive to the BZ + SAHA combination.
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Yu C, Friday BB, Yang L, Atadja P, Wigle D, Sarkaria J, Adjei AA. Mitochondrial Bax translocation partially mediates synergistic cytotoxicity between histone deacetylase inhibitors and proteasome inhibitors in glioma cells. Neuro Oncol 2008; 10:309-19. [PMID: 18445700 PMCID: PMC2563053 DOI: 10.1215/15228517-2007-063] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 09/11/2007] [Indexed: 11/19/2022] Open
Abstract
The effects of combining histone deacetylase (HDAC) inhibitors and proteasome inhibitors were evaluated in both established glioblastoma multiforme (GBM) cell lines and short-term cultures derived from the Mayo Clinic xenograft GBM panel. Coexposure of LBH589 and bortezomib at minimally toxic doses of either drug alone resulted in a striking induction of apoptosis in established U251, U87, and D37 GBM cell lines, as well as in GBM8, GBM10, GBM12, GBM14, and GBM56 short-term cultured cell lines. Synergism of apoptosis induction was also observed in U251 cells when coexposing cells to other HDAC inhibitors, including LAQ824 and trichostatin A, with the proteasome inhibitor MG132, thus demonstrating a class effect. In U251 cells, bortezomib alone or in combination with LBH589 decreased Raf-1 levels and suppressed Akt and Erk activation. LBH589 or bortezomib alone increased expression of the cell cycle regulators p21 and p27. Additionally, the combination, but not the individual agents, markedly enhanced JNK activation. Synergistic induction of apoptosis after exposure to LBH589 and bortezomib was partially mediated by Bax translocation from the cytosol to the mitochondria resulting from Bax conformational changes. Bax translocation precedes cytochrome c release and apoptosis, and selective down-regulation of Bax using siRNA significantly mitigates the cytotoxicity of LBH589 and bortezomib. This combination regimen warrants further preclinical and possible clinical study for glioma patients.
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Affiliation(s)
- Chunrong Yu
- Departments of Oncology (B.B.F.), Laboratory Medicine and Pathology (L.Y.), Thoracic Surgery (D.W.), and Radiation Oncology (J.S.), Mayo Clinic, Rochester, MN; Novartis Institutes for Biomedical Research (P.A.), Boston, MA; Department of Medicine, Roswell Park Cancer Institute (C.Y., A.A.A.), Buffalo, NY; USA
| | - Bret B. Friday
- Departments of Oncology (B.B.F.), Laboratory Medicine and Pathology (L.Y.), Thoracic Surgery (D.W.), and Radiation Oncology (J.S.), Mayo Clinic, Rochester, MN; Novartis Institutes for Biomedical Research (P.A.), Boston, MA; Department of Medicine, Roswell Park Cancer Institute (C.Y., A.A.A.), Buffalo, NY; USA
| | - Lin Yang
- Departments of Oncology (B.B.F.), Laboratory Medicine and Pathology (L.Y.), Thoracic Surgery (D.W.), and Radiation Oncology (J.S.), Mayo Clinic, Rochester, MN; Novartis Institutes for Biomedical Research (P.A.), Boston, MA; Department of Medicine, Roswell Park Cancer Institute (C.Y., A.A.A.), Buffalo, NY; USA
| | - Peter Atadja
- Departments of Oncology (B.B.F.), Laboratory Medicine and Pathology (L.Y.), Thoracic Surgery (D.W.), and Radiation Oncology (J.S.), Mayo Clinic, Rochester, MN; Novartis Institutes for Biomedical Research (P.A.), Boston, MA; Department of Medicine, Roswell Park Cancer Institute (C.Y., A.A.A.), Buffalo, NY; USA
| | - Dennis Wigle
- Departments of Oncology (B.B.F.), Laboratory Medicine and Pathology (L.Y.), Thoracic Surgery (D.W.), and Radiation Oncology (J.S.), Mayo Clinic, Rochester, MN; Novartis Institutes for Biomedical Research (P.A.), Boston, MA; Department of Medicine, Roswell Park Cancer Institute (C.Y., A.A.A.), Buffalo, NY; USA
| | - Jann Sarkaria
- Departments of Oncology (B.B.F.), Laboratory Medicine and Pathology (L.Y.), Thoracic Surgery (D.W.), and Radiation Oncology (J.S.), Mayo Clinic, Rochester, MN; Novartis Institutes for Biomedical Research (P.A.), Boston, MA; Department of Medicine, Roswell Park Cancer Institute (C.Y., A.A.A.), Buffalo, NY; USA
| | - Alex A. Adjei
- Departments of Oncology (B.B.F.), Laboratory Medicine and Pathology (L.Y.), Thoracic Surgery (D.W.), and Radiation Oncology (J.S.), Mayo Clinic, Rochester, MN; Novartis Institutes for Biomedical Research (P.A.), Boston, MA; Department of Medicine, Roswell Park Cancer Institute (C.Y., A.A.A.), Buffalo, NY; USA
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Choi MR, Najafi F, Safa AR, Drexler HCA. Analysis of changes in the proteome of HL-60 promyeloid leukemia cells induced by the proteasome inhibitor PSI. Biochem Pharmacol 2008; 75:2276-88. [PMID: 18468579 DOI: 10.1016/j.bcp.2008.03.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 03/19/2008] [Accepted: 03/20/2008] [Indexed: 02/07/2023]
Abstract
Proteasome inhibitors display potent anti-neoplastic and anti-angiogenic properties both in vitro and in vivo. The mechanisms, however, by which proteasome inhibitors kill tumor cells are still fairly elusive as is the molecular basis of resistance to treatment. To address these questions, we employed a high-throughput Western blotting procedure to analyze changes in a subproteome of approximately 800 proteins in the promyelocytic leukemia cell line HL-60 upon treatment with the proteasome inhibitor PSI (Z-Ile-Glu(OtBu)-Ala-Leu-aldehyde) and correlated the changes of selected target proteins with the changes in two multidrug-resistant HL-60 variants. In total, 105 proteins were upregulated more than 1.5-fold after PSI treatment, while 79 proteins were downregulated. Activation of caspases-3 and -8, modulation of members of the Bcl-2 family as well as stimulation of stress signaling pathways was prominent during HL-60 apoptosis. We also identified changes in the abundance of proteins previously not known to be affected by proteasome inhibitors. In contrast, two multidrug-resistant HL-60 cell lines, overexpressing either MRP1 or P-glycoprotein were largely resistant to PSI-induced apoptosis and could not be resensitized by the pharmacological inhibitors of the drug efflux pumps MK571 or PSC833. Drug resistance was also independent of the upregulation of Bad. Overexpression of multidrug resistance proteins, P-glycoprotein and MRP-1 is thus not sufficient to explain resistance of HL-60 cells to treatment with proteasome inhibitor PSI, which remains more closely related to a low level of Bax expression and to the inability to activate JNK. Alternative routes to the acquisition of resistance to PSI have therefore to be considered.
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Affiliation(s)
- Mi-Ran Choi
- Max Planck Institute for Molecular Biomedicine, Department for Vascular Cell Biology, Roentgenstr. 20, 48149 Muenster, Germany.
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Heider U, Metzler IV, Kaiser M, Rosche M, Sterz J, Rötzer S, Rademacher J, Jakob C, Fleissner C, Kuckelkorn U, Kloetzel PM, Sezer O. Synergistic interaction of the histone deacetylase inhibitor SAHA with the proteasome inhibitor bortezomib in mantle cell lymphoma. Eur J Haematol 2007; 80:133-42. [DOI: 10.1111/j.1600-0609.2007.00995.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Emanuele S, Lauricella M, Carlisi D, Vassallo B, D'Anneo A, Di Fazio P, Vento R, Tesoriere G. SAHA induces apoptosis in hepatoma cells and synergistically interacts with the proteasome inhibitor Bortezomib. Apoptosis 2007; 12:1327-38. [PMID: 17351739 DOI: 10.1007/s10495-007-0063-y] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Histone deacetylase (HDAC) inhibitors represent a promising group of anticancer agents. This paper shows that the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) stimulated at 5-10 microM apoptosis in human hepatoma HepG2 and Huh6 cells, but was ineffective in primary human hepatocytes (PHH). In HepG2 cells SAHA induced the extrinsic apoptotic pathway, increasing the expression of both FasL and FasL receptor and causing the activation of caspase-8. Moreover, SAHA enhanced the level of Bim proteins, stimulated alternative splicing of the Bcl-X transcript with the expression of the proapoptotic Bcl-Xs isoform, induced degradation of Bid into the apoptotic factor t-Bid and dephosphorylation and inactivation of the anti-apoptotic factor Akt. Consequently, SAHA caused loss of mitochondrial transmembrane potential, release of cytochrome c from mitochondria, activation of caspase-3 and degradation of PARP. Interestingly, a combination of suboptimal doses of SAHA (1 microM) and bortezomib (5-10 nM), a potent inhibitor of 26S proteasome, synergistically induced apoptosis in both HepG2 and Huh6 cells, but was ineffective in PHH. Combined treatment increased with synergistic effects the expression levels of c-Jun, phospho-c-Jun and FasL and the production of Bcl-Xs. These effects were accompanied by activation of Bid, caspase-8 and 3. In conclusion, SAHA stimulated apoptosis in hepatoma cells and exerted a synergistic apoptotic effect when combined with bortezomib. In contrast, these treatments were quite ineffective in inducing apoptosis in PHH. Thus, our results suggest the potential application of the SAHA/bortezomib combination in clinical trials for liver cancer.
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Affiliation(s)
- S Emanuele
- Dipartimento di Scienze Biochimiche, Università di Palermo, Policlinico, Palermo, Italy
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