title: L-carnitine is an endogenous HDAC inhibitor selectively inhibiting cancer cell growth in vivo and in vitro.
abstract: L-carnitine (LC) is generally believed to transport long-chain acyl groups from fatty acids into the mitochondrial matrix for ATP generation via the citric acid cycle. Based on Warburg's theory that most cancer cells mainly depend on glycolysis for ATP generation, we hypothesize that, LC treatment would lead to disturbance of cellular metabolism and cytotoxicity in cancer cells. In this study, Human hepatoma HepG2, SMMC-7721 cell lines, primary cultured thymocytes and mice bearing HepG2 tumor were used. ATP content was detected by HPLC assay. Cell cycle, cell death and cell viability were assayed by flow cytometry and MTS respectively. Gene, mRNA expression and protein level were detected by gene microarray, Real-time PCR and Western blot respectively. HDAC activities and histone acetylation were detected both in test tube and in cultured cells. A molecular docking study was carried out with CDOCKER protocol of Discovery Studio 2.0 to predict the molecular interaction between L-carnitine and HDAC. Here we found that (1) LC treatment selectively inhibited cancer cell growth in vivo and in vitro; (2) LC treatment selectively induces the expression of p21(cip1) gene, mRNA and protein in cancer cells but not p27(kip1); (4) LC increases histone acetylation and induces accumulation of acetylated histones both in normal thymocytes and cancer cells; (5) LC directly inhibits HDAC I/II activities via binding to the active sites of HDAC and induces histone acetylation and lysine-acetylation accumulation in vitro; (6) LC treatment induces accumulation of acetylated histones in chromatin associated with the p21(cip1) gene but not p27(kip1) detected by ChIP assay. These data support that LC, besides transporting acyl group, works as an endogenous HDAC inhibitor in the cell, which would be of physiological and pathological importance.
authors.affiliation: Protein Modification and Degradation Lab, Department of Pathophysiology, Guangzhou Medical College, Guangdong, People's Republic of China.
authors.forename: Hongbiao
authors.initials: H
authors.lastname: Huang
authors.forename: Ningning
authors.initials: N
authors.lastname: Liu
authors.forename: Haiping
authors.initials: H
authors.lastname: Guo
authors.forename: Siyan
authors.initials: S
authors.lastname: Liao
authors.forename: Xiaofen
authors.initials: X
authors.lastname: Li
authors.forename: Changshan
authors.initials: C
authors.lastname: Yang
authors.forename: Shouting
authors.initials: S
authors.lastname: Liu
authors.forename: Wenbin
authors.initials: W
authors.lastname: Song
authors.forename: Chunjiao
authors.initials: C
authors.lastname: Liu
authors.forename: Lixia
authors.initials: L
authors.lastname: Guan
authors.forename: Bing
authors.initials: B
authors.lastname: Li
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.forename: Change
authors.initials: C
authors.lastname: Zhang
authors.forename: Xuejun
authors.initials: X
authors.lastname: Wang
authors.forename: Q Ping
authors.initials: QP
authors.lastname: Dou
authors.forename: Jinbao
authors.initials: J
authors.lastname: Liu
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002331:Carnitine / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002843:Chromatin / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D062105:Molecular Docking Simulation; D009369:Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D002843:Chromatin; D050759:Cyclin-Dependent Kinase Inhibitor p21; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D012333:RNA, Messenger; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000255:Adenosine Triphosphate; D006655:Histone Deacetylases; D002331:Carnitine