title: Ibandronate increases the expression of the pro-apoptotic gene FAS by epigenetic mechanisms in tumor cells.
abstract: There is growing evidence that aminobisphosphonates like ibandronate show anticancer activity by an unknown mechanism. Biochemically, they prevent posttranslational isoprenylation of small GTPases, thus inhibiting their activity. In tumor cells, activated RAS-GTPase, the founding member of the gene family, down-regulates the expression of the pro-apoptotic gene FAS via epigenetic DNA-methylation by DNMT1. We compared ibandronate treatment in neoplastic human U-2 osteosarcoma and in mouse CCL-51 breast cancer cells as well as in the immortalized non-neoplastic MC3T3-E1 osteoblastic cells. Ibandronate attenuated cell proliferation in all cell lines tested. In the neoplastic cells we found up-regulation of caspases suggesting apoptosis. Further we found stimulation of FAS-expression as a result of epigenetic DNA demethylation that was due to down-regulation of DNMT1, which was rescued by re-isoprenylation by both geranylgeranyl-pyrophosphate and farnesylpyrophosphate. In contrast, ibandronate did not affect FAS and DNMT1 expression in MC3T3-E1 non-neoplastic cells. Data suggest that bisphosphonates via modulation of the activity of small-GTPases induce apoptosis in neoplastic cells by DNA-CpG-demethylation and stimulation of FAS-expression. In conclusion the shown epigenetic mechanism underlying the anti-neoplastic activity of farnesyl-transferase-inhibition, also explains the clinical success of other drugs, which target this pathway.
authors.affiliation: Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Center Meidling, 1st Medical Department, Hanusch Hospital, Vienna, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Thaler
authors.forename: S
authors.initials: S
authors.lastname: Spitzer
authors.forename: H
authors.initials: H
authors.lastname: Karlic
authors.forename: C
authors.initials: C
authors.lastname: Berger
authors.forename: K
authors.initials: K
authors.lastname: Klaushofer
authors.forename: F
authors.initials: F
authors.lastname: Varga
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000009:adverse effects / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects*; D004164:Diphosphonates / Q000009:adverse effects / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D044127:Epigenesis, Genetic / Q000187:drug effects; D005260:Female; D020868:Gene Silencing; D006801:Humans; D000077557:Ibandronic Acid; D008297:Male; D051379:Mice; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012516:Osteosarcoma / Q000188:drug therapy*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects*; D019014:fas Receptor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D009363:Neoplasm Proteins; D019014:fas Receptor; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; D000077557:Ibandronic Acid