title: Anticancer activities of selected species of North American lichen extracts.
abstract: Cancer is the second leading cause of human deaths in the USA. Despite continuous efforts to treat cancer over the past 50 years, human mortality rates have not decreased significantly. Natural products, such as lichens, have been good sources of anticancer drugs. This study reports the cytotoxic activity of crude extracts of 17 lichen species against Burkitt's lymphoma (Raji) cells. Out of the 17 lichen species, extracts from 14 species showed cytotoxicity against Raji cells. On the basis of IC50 values, we selected Xanthoparmelia chlorochroa and Tuckermannopsis ciliaris to study the mechanism of cell death. Viability of normal lymphocytes was not affected by the extracts of X. chlorochroa and T. ciliaris. We found that extracts from both lichens decreased proliferation, accumulated cells at the G0 /G1 stage, and caused apoptosis in a dose-dependent manner. Both lichen extracts also caused upregulation of p53. The T. ciliaris extract upregulated the expression of TK1 but X. chlorochroa did not. We also found that usnic, salazinic, constictic, and norstictic acids were present in the extract of X. chlorochroa, whereas protolichesterinic acid in T. ciliaris extracts. Our data demonstrate that lichen extracts merit further research as a potential source of anticancer drugs.
authors.affiliation: Department of Biology, Brigham Young University, Provo, UT, USA; M. L. Bean Life Science Museum, Brigham Young University, Provo, UT, USA.
authors.forename: Gajendra
authors.initials: G
authors.lastname: Shrestha
authors.forename: Atif M
authors.initials: AM
authors.lastname: El-Naggar
authors.forename: Larry L
authors.initials: LL
authors.lastname: St Clair
authors.forename: Kim L
authors.initials: KL
authors.lastname: O'Neill
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001572:Benzofurans; D045744:Cell Line, Tumor / Q000187:drug effects; D002470:Cell Survival; D006801:Humans; D020128:Inhibitory Concentration 50; D007783:Lactones; D008011:Lichens / Q000737:chemistry*; D008214:Lymphocytes / Q000187:drug effects; D015394:Molecular Structure; D012459:Salicylates; D013937:Thymidine Kinase / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014481:United States
chemical_list: D000970:Antineoplastic Agents; D001572:Benzofurans; D007783:Lactones; D012459:Salicylates; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C553078:norstictic acid; C116675:salazinic acid; C073339:usnic acid; C095781:protolichesterinic acid; D013937:Thymidine Kinase; C092717:thymidine kinase 1; D015107:4-Butyrolactone
keywords: Burkitt's lymphoma; anticancer; cytotoxicity; lichen; natural products