title: Geranylgeranyl diphosphate synthase inhibition induces apoptosis that is dependent upon GGPP depletion, ERK phosphorylation and caspase activation.
abstract: Bisphosphonates are diphosphate analogs that inhibit the intermediate enzymes of the mevalonate pathway. Here, we compared the effects of a farnesyl diphosphate synthase inhibitor, zoledronate, and a geranylgeranyl diphosphate synthase (GGDPS) inhibitor, digeranyl bisphosphonate (DGBP), on lymphocytic leukemia cell proliferation and apoptosis. Both zoledronate and DGBP inhibited proliferation with DGBP doing so more potently. DGBP was markedly less toxic than zoledronate toward the viability of healthy human peripheral blood mononuclear cells. Addition of GGPP, but not farnesyl diphosphate (FPP), prevented the anti-proliferative effects of DGBP. Both GGPP and FPP partially rescued the effects of zoledronate. Co-treatment with DGBP and zoledronate was antagonistic. To further assess the effects of the bisphosphonates, we analyzed annexin V and propidium iodide staining via flow cytometry and found that DGBP induced apoptosis more potently than zoledronate. Western blots show that DGBP treatment altered expression and membrane affinity of some but not all geranylgeranylated small GTPases, activated caspases and increased ERK phosphorylation. Importantly, the anti-proliferative effects of DGBP were blocked by treatment with a caspase inhibitor and by treatment with a MEK inhibitor. Together, our findings indicate that DGBP is a more potent and selective compound than zoledronate in inducing apoptosis mediated through pathways that include caspases and MEK/ERK. These findings support the further development of GGDPS inhibitors as anticancer therapeutics.
authors.affiliation: Department of Pharmaceutical Sciences, University of Connecticut, School of Pharmacy, Storrs, CT, USA.
authors.forename: Sherry S
authors.initials: SS
authors.lastname: Agabiti
authors.affiliation: Department of Pharmaceutical Sciences, University of Connecticut, School of Pharmacy, Storrs, CT, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Pharmaceutical Sciences, University of Connecticut, School of Pharmacy, Storrs, CT, USA.|Institute for Systems Genomics, University of Connecticut, Storrs, CT, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wiemer
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004164:Diphosphonates / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D051231:Farnesyltranstransferase / Q000037:antagonists & inhibitors*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D019169:Jurkat Cells; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008798:Mevalonic Acid / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects*; D011106:Polyisoprenyl Phosphates / Q000378:metabolism / Q000494:pharmacology*; D012717:Sesquiterpenes / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology; D000077211:Zoledronic Acid
chemical_list: D004164:Diphosphonates; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; D013729:Terpenes; C518651:digeranyl bisphosphonate; D000077211:Zoledronic Acid; C004808:farnesyl pyrophosphate; D051231:Farnesyltranstransferase; D020169:Caspases; C002963:geranylgeranyl pyrophosphate; D008798:Mevalonic Acid