Synadenium umbellatum Pax. promotes cell cycle arrest and induces apoptosis in K-562 leukemia cells

Abstract

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disease that shows apoptosis resistance. The introduction of imatinib mesylate has revolutionized the treatment of CML, but imatinib resistance may develop at any time and inevitably leads to disease progression. Synadenium umbellatum Pax. belongs to the Euphorbiaceae family and is popularly used in Brazil for the treatment of cancer. The cytotoxicity of Euphorbiaceae is associated with the ability of these plants and their bioactive compounds to induce apoptotic tumor cell death. Therefore, we aimed to investigate the cytotoxicity and the mechanisms of death induced by S. umbellatum extract in leukemic cells. S. umbellatum cytotoxicity was evaluated by trypan blue exclusion assay and flow cytometric analysis of the cell cycle; the mechanisms involved in K-562 cell death were investigated by light microscopy and flow cytometry. The results demonstrate that S. umbellatum is cytotoxic to leukemic cells in a concentration-dependent manner. Morphological analysis revealed that S. umbellatum treatment induced K-562 cell death by an apoptotic pathway. Furthermore, data indicate ROS overproduction, alterations in mitochondrial membrane potential, phosphatidylserine externalization and activation of caspase 9. Taken together, the results demonstrate that S. umbellatum extract arrested the cell cycle and triggered apoptosis at several levels in K-562 cells. A leucemia mielóide crônica (LMC) é uma doença mieloproliferativa clonal, que apresenta resistência à apoptose. A introdução do mesilato de imatinibe revolucionou o tratamento da LMC, porém a resistência ao imatinibe pode ser desenvolvida em qualquer tempo e, inevitavelmente, leva à progressão da doença. Synadenium umbellatum Pax. pertence à família Euphorbiaceae e é usado popularmente no Brasil para o tratamento do câncer. A citotoxicidade das Euphorbiaceae está associada com a capacidade dessas plantas e seus compostos bioativos em induzir apoptose em células tumorais. Portanto, este trabalho teve como objetivo investigar a citotoxicidade e os mecanismos de morte induzidos por S. umbellatum em células leucêmicas. A citotoxicidade de S. umbellatum foi avaliada pelo ensaio de exclusão do azul de tripano e a análise do ciclo celular foi feita por citometria de fluxo. Os mecanismos envolvidos na morte celular das células K-562 foram investigados por microscopia óptica e por citometria de fluxo. Os resultados demonstraram que S. umbellatum é citotóxico para células leucêmicas de uma maneira dependente da concentração. A análise morfológica revelou que o tratamento com S. umbellatum induziu as célula K-562 à morte por via apoptótica. Além disso, os dados indicam aumento de ERO S , alterações no potencial de membrana mitocondrial, externalização da fosfatidilserina e ativação de caspase 9. Em conjunto, os resultados demonstram que S. umbellatum promoveu retenção do ciclo celular das células K-562 e induziu estas células à morte por apoptose.

4-Nerolidylcatechol: apoptosis by mitochondrial mechanisms with reduction in cyclin D1 at G0/G1 stage of the chronic myelogenous K562 cell line

“… 2011 ; Mota et al. 2012 ). In addition, BCR-ABL-expression in K562 cells presents resistance to apoptosis induced by conventional chemotherapeutics and allows for the evaluation of several cellular and molecular events concurrently, which justifies the use of this valuable cellular model in drug discovery (Huang et al.…”

Enriched Terpenes Fractions of the Latex of Euphorbia umbellata Promote Apoptosis in Leukemic Cells

“…This effect has been observed for the hexane extract of the latex from E. umbellata and other matrices obtained from Euphorbia species, against leukemia cell lineages. [10,12,14,25,26] The cell cycle analysis demonstrated that the treatment with Dcm increased S and G2/M population (compared with the negative control), as observed to doxorubicin ( Figure 4). Similar data already demonstrated the same effect of doxorubicin in HL-60 cell and some lymphoma cell line cycle, showing an increase of S and G2/M phase cell population, which appears to be related with the upregulation of cyclin B1 and cyclin A2, and expression of topoisomerase IIα.…”

“…[26] On the other hand, Luz et al [14] described that hexane extract from the latex of E. umbellata promoted cell cycle arrest in phase G0/G1 for Jurkat cells, and a similar result was obtained for Jurkat cells treated with chloroform extract from E. umbellata barks and K-562 cells treated with E. umbellata aerial parts extracts. [10,12] Probably these changes in the cycle arrest can be related with the concentration of the compounds in the vegetal matrix used in these experiments. [26] Other mechanisms studied include the analysis of mitochondrial transmembrane potential and caspases activation.…”

“…Extracts from the aerial parts of E. umbellata were able to increase by 15 % the activity of caspase 9, in K-562 cells, and in a similar way, an extract from E. formosana elevated the cleavage of caspase 3 from 2.4 to 3.7-fold, in THP-1. [10,31] Some other mechanisms that could be related to cytotoxic effect of diterpenes include inhibition of the activity of topoisomerase II and/or DNA synthesis, induction of apoptosis through either the inhibition of IL-6-induced and STAT3 activation or the inhibition of the NF-кB signaling pathway, [21] and interaction with the cell membrane (altered cell adhesion, modification in activities of cell receptors, enhanced intake of 2deoxyglucose and other nutrients, induction of arachidonic acid release and prostaglandin synthesis, inhibition of binding of epidermal growth factor to cell surface receptors, and altered lipid metabolism). [33] To triterpenes could be suggested segregation/down regulation of TGF-β receptor inside membrane rafts, [34] induction of apoptosis, and inhibition of expression of genes associated with cell proliferation, survival, angiogenesis and inflammation (such as cyclin D1, EGFR, bcl-2, survivin, VEGF, VEGFR, p65, NF-кB, TNF, STAT3, TLR and PI3K/Akt/mTOR).…”