title: In vitro cytotoxicity of cyclodextrin-bonded birch bark extract.
abstract: Triterpenoids from birch bark, like betulin, seem to have an anticancer potential which needs to be further investigated. Aim of this study was first to explore whether a cyclodextrin-solubilised triterpenoid extract (STE) from birch bark induces selective cytotoxic effects in primary liver cancer cells compared to healthy human hepatocytes. Second, selective cytotoxicity against several tumour cell lines should be analysed. For this purpose, human liver cancer cells derived from mouse xenografts (LIXF 575), healthy human hepatocytes, and 42 different human tumour cell lines were incubated with different concentrations of STE corresponding to 4.3 µM - 137.5 µM betulin (BE). Cytotoxicity was tested with the WST-1 cell proliferation assay, apoptosis with caspase 3/7-activity, and necrosis was determined by the propidiumiodid uptake assay. The pathway of cytotoxic effects was further investigated by immunoblotting of apoptosis inducing factor (AIF) and p53. The monolayer assay was used to analyse selectivity of STE towards different tumour cell lines. STE significantly (p < 0.001) reduced viability and induced apoptosis of LIXF cells in low concentrations corresponding to 8.6 µM BE, while human hepatocytes were affected only in concentrations ≥ 68.8 µM. Cell death occurred in a p53 independent manner, and AIF was not involved. The mean IC50 in the 42 tumour cell lines corresponded to 4.3 µM BE and ranged from 2.05 µM to 8.95 µM BE content. Selectivity was, therefore, rather low. In conclusion, STE exhibits in low concentrations cytotoxicity in a broad spectrum of primary cancer cells and cancer cell lines, which is, at least in LIXF cells, induced by caspase 3/7 mediated apoptosis. STE is far less toxic in hepatocytes. The anticancer potential of STE should be further characterised and also investigated in animal models.
authors.affiliation: Center for Complementary Medicine, Department of Environmental Health Sciences, University Medical Center Freiburg, Freiburg, Germany. ankehertrampf@aol.com
authors.forename: Anke
authors.initials: A
authors.lastname: Hertrampf
authors.forename: Carsten
authors.initials: C
authors.lastname: Gründemann
authors.forename: Sebastian
authors.initials: S
authors.lastname: Jäger
authors.forename: Melanie
authors.initials: M
authors.lastname: Laszczyk
authors.forename: Torsten
authors.initials: T
authors.lastname: Giesemann
authors.forename: Roman
authors.initials: R
authors.lastname: Huber
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D029662:Betula; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003505:Cyclodextrins / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D005260:Female; D022781:Hepatocytes / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D051379:Mice; D024301:Plant Bark / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: C494829:AIFM1 protein, human; D000972:Antineoplastic Agents, Phytogenic; D051033:Apoptosis Inducing Factor; D003505:Cyclodextrins; D010936:Plant Extracts; D016159:Tumor Suppressor Protein p53; D053148:Caspase 3; D053179:Caspase 7