In vitro cytotoxicity against different human cancer cell lines of laticifer proteins of Calotropis procera (Ait.) R. Br.
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.
Soares de Oliveira
Jefferson
J
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Campus do Pici, Caixa Postal 6033, CEP 60.451-970, Fortaleza, Ceará, Brazil.
Pereira Bezerra
Daniel
D
Teixeira de Freitas
Cleverson Diniz
CD
Delano Barreto Marinho Filho
José
J
Odorico de Moraes
Manoel
M
Pessoa
Claudia
C
Costa-Lotufo
Letícia Veras
LV
Ramos
Márcio Viana
MV
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
D000972:Antineoplastic Agents, Phytogenic; D010940:Plant Proteins; D008623:Mercaptoethanol; D004226:Dithioerythritol; D011402:Pronase