title: Potential use of alexidine dihydrochloride as an apoptosis-promoting anticancer agent.
abstract: Despite advances in surgery, radiation, and chemotherapy, novel therapeutics are needed for head and neck cancer treatment. The objective of this current study was to evaluate alexidine dihydrochloride as a novel compound lead for head and neck cancers. Using a tetrazolium-based assay, the dose required to reduce cell viability by 50% (ED50) was found to be approximately 1.8 micromol/L in FaDu (human hypopharyngeal squamous cancer) and approximately 2.6 micromol/L in C666-1 (human undifferentiated nasopharyngeal cancer) cells. In contrast, the ED50 values were much higher in untransformed cells, specifically at approximately 8.8 micromol/L in GM05757 (primary normal human fibroblast), approximately 8.9 micromol/L in HNEpC (primary normal human nasal epithelial), and approximately 19.6 micromol/L in NIH/3T3 (mouse embryonic fibroblast) cells. Alexidine dihydrochloride did not interfere with the activities of cisplatin, 5-fluorouracil, or radiation, and interacted in a less-than-additive manner. DNA content analyses and Hoechst 33342 staining revealed that this compound induced apoptosis. Alexidine dihydrochloride-induced mitochondrial damage was visualized using transmission electron microscopy. Mitochondrial membrane potential (DeltaPsiM) depolarization was detectable after only 3 hours of treatment, and was followed by cytosolic Ca2+ increase along with loss of membrane integrity/cell death. Caspase-2 and caspase-9 activities were detectable at 12 hours, caspase-8 at 24 hours, and caspase-3 at 48 hours. FaDu cell clonogenic survival was reduced to < 5% with 1 micromol/L alexidine dihydrochloride, and, correspondingly, this compound decreased the in vivo tumor-forming potential of FaDu cells. Thus, we have identified alexidine dihydrochloride as the first bisbiguanide compound with anticancer specificity.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Yip
authors.forename: Emma
authors.initials: E
authors.lastname: Ito
authors.forename: Xinliang
authors.initials: X
authors.lastname: Mao
authors.forename: P Y Billie
authors.initials: PY
authors.lastname: Au
authors.forename: David W
authors.initials: DW
authors.lastname: Hedley
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Mocanu
authors.forename: Carlo
authors.initials: C
authors.lastname: Bastianutto
authors.forename: Aaron
authors.initials: A
authors.lastname: Schimmer
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Liu
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001645:Biguanides / Q000008:administration & dosage / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology; D053143:Caspase 2 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002945:Cisplatin / Q000008:administration & dosage; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D007012:Hypopharyngeal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000502:physiology; D041681:NIH 3T3 Cells; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D001645:Biguanides; D053143:Caspase 2; D053453:Caspase 9; C001570:alexidine; D002945:Cisplatin; D005472:Fluorouracil