title: In vitro cytotoxicity against different human cancer cell lines of laticifer proteins of Calotropis procera (Ait.) R. Br.
abstract: This work evaluated the in vitro cytotoxic activity of laticifer proteins (LP) recovered from the latex of the medicinal plant Calotropis procera. The LP displayed considerable cytotoxicity with IC(50) values ranging from 0.42 to 1.36 microg/ml to SF295 and MDA-MB-435 cell lines, respectively. In healthy peripheral blood mononuclear cells exposed to LP (10 microg/ml) for 72 h, no noticeable effects on viability or cell morphology were seen. The fractionating of LP on an ion exchange chromatography gave rise to a new fraction (PI) that retained almost all cytotoxicity. The cytotoxic effects of both LP and PI were diminished when previously treated with pronase, or 2-mercaptoethanol, suggesting a protein nature of active molecules, however, pre-incubation with dithiothreitol (DTT) only reduced PI activity. PI did not exhibit cysteine proteinase activity, indicating that cysteine proteinases, abundantly found in LP, are not implicated in LP cytotoxicity. In this study, using HL-60 cell as a model, LP was shown to inhibit DNA synthesis. This is probably due to alterations in the topology of DNA, since it was observed that LP is able to interfere in topoisomerase I activity by somehow acting upon DNA. LP provoked reduction in cell number but it did not cause any significant increase in the number of non-viable cells. These findings corroborated with the morphologic analysis, where cells treated with LP showed morphology of apoptotic process with abundant vacuoles, chromatin condensation and fragmentation of the nuclei. The results of this study suggests that LP is a target for DNA topoisomerase I triggering apoptosis in cancer cell lines.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Campus do Pici, Caixa Postal 6033, CEP 60.451-970, Fortaleza, Ceará, Brazil.
authors.forename: Jefferson
authors.initials: J
authors.lastname: Soares de Oliveira
authors.forename: Daniel
authors.initials: D
authors.lastname: Pereira Bezerra
authors.forename: Cleverson Diniz
authors.initials: CD
authors.lastname: Teixeira de Freitas
authors.forename: José
authors.initials: J
authors.lastname: Delano Barreto Marinho Filho
authors.forename: Manoel
authors.initials: M
authors.lastname: Odorico de Moraes
authors.forename: Claudia
authors.initials: C
authors.lastname: Pessoa
authors.forename: Letícia Veras
authors.initials: LV
authors.lastname: Costa-Lotufo
authors.forename: Márcio Viana
authors.initials: MV
authors.lastname: Ramos
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry* / Q000494:pharmacology*; D031107:Calotropis / Q000737:chemistry*; D045744:Cell Line, Tumor; D004226:Dithioerythritol / Q000494:pharmacology; D006801:Humans; D008623:Mercaptoethanol / Q000494:pharmacology; D010940:Plant Proteins / Q000737:chemistry* / Q000494:pharmacology*; D011402:Pronase / Q000494:pharmacology
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D010940:Plant Proteins; D008623:Mercaptoethanol; D004226:Dithioerythritol; D011402:Pronase