Abstract
Combinations of proteasome inhibitors and histone deacetylases (HDAC) inhibitors appear to be the most potent to produce synergistic cytotoxicity in preclinical trials. We have recently confirmed that L-carnitine (LC) is an endogenous HDAC inhibitor. In the current study, the anti-tumor effect of LC plus proteasome inhibitor bortezomib (velcade, Vel) was investigated both in cultured hepatoma cancer cells and in Balb/c mice bearing HepG2 tumor. Cell death and cell viability were assayed by flow cytometry and MTS, respectively. Gene, mRNA expression and protein levels were detected by gene microarray, quantitative real-time PCR and Western blot, respectively. The effect of Vel on the acetylation of histone H3 associated with the p21(cip1) gene promoter was examined by using ChIP assay and proteasome peptidase activity was detected by cell-based chymotrypsin-like (CT-like) activity assay. Here we report that (i) the combination of LC and Vel synergistically induces cytotoxicity in vitro; (ii) the combination also synergistically inhibits tumor growth in vivo; (iii) two major pathways are involved in the synergistical effects of the combinational treatment: increased p21(cip1) expression and histone acetylation in vitro and in vivo and enhanced Vel-induced proteasome inhibition by LC. The synergistic effect of LC and Vel in cancer therapy should have great potential in the future clinical trials.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetylation / drug effects
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Animals
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Antineoplastic Agents / pharmacology*
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Boronic Acids / pharmacology*
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Bortezomib
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Carnitine / pharmacology*
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Caspases / metabolism
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Cell Death / drug effects
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Cell Proliferation / drug effects
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Chromatin / metabolism
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Cyclin-Dependent Kinase Inhibitor p21 / genetics
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Cyclin-Dependent Kinase Inhibitor p21 / metabolism
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Drug Synergism
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Endoplasmic Reticulum Stress / drug effects
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Enzyme Activation / drug effects
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Hep G2 Cells
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Histone Deacetylase Inhibitors / pharmacology*
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Histones / metabolism
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Humans
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Male
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Mice
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Models, Biological
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Poly(ADP-ribose) Polymerases / metabolism
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Proteasome Inhibitors / pharmacology*
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Pyrazines / pharmacology*
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RNA, Small Interfering / metabolism
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Unfolded Protein Response / drug effects
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Xenograft Model Antitumor Assays
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bcl-2-Associated X Protein / metabolism
Substances
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Antineoplastic Agents
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Boronic Acids
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Chromatin
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Cyclin-Dependent Kinase Inhibitor p21
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Histone Deacetylase Inhibitors
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Histones
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Proteasome Inhibitors
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Pyrazines
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RNA, Small Interfering
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bcl-2-Associated X Protein
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Bortezomib
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Poly(ADP-ribose) Polymerases
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Caspases
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Carnitine
Grants and funding
This work was supported by the National High Technology Research and Development Program of China (Project 2006AA02Z4B5), National Natural Science Foundation of China (Project 81070033, 30770835, 81170608, 81072091) (to JL, PT, and CZ); Projects (9251018201002, 94510018201003604) of Guangdong Province Natural Science Foundation; Projects from Foundation for Distinguished Young Talents in Higher Education of Guangdong and the Foundation of Guangzhou Medical College for Doctor Scientists (2011C24), and projects from Guangzhou Municipal Education Commission (10A057S, 08A108) (to JL, HH and CZ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.