Autophagy is involved in cytotoxic effects of crotoxin in human breast cancer cell line MCF-7 cells

Abstract

Aim: To investigate the role of crotoxin (CrTX)‐induced autophagy in the death of MCF‐7 cells, a caspase‐3‐deficient, human breast cancer cell line. Methods: Cultured MCF‐7 cells were treated with various doses of CrTX, a phospholipase A2 (PLA2) isolated from the venom of the South American rattlesnake, Crotalus durissus terrificus. The cytotoxicity of CrTX in the presence and absence of caspase inhibitors was measured with methyl thiazolyl tetrazolium (MTT) and lactate dehydrogenase (LDH) leakage assays. The activation of autophagy was determined with transmission electron microscope and monodansylcadaverin (MDC) labeling. The upregulation of lysosomal enzymes, the release of cyto‐chrome c (cyto‐c), and the nuclear translocation of the apoptosis inducing factor (AIF) were examined by immunoblotting and immunofluorescence. Results: CrTX inhibited the viability of MCF‐7 cells in a dose‐ and time‐dependent manner. CrTX‐activated autophagy was revealed by punctuate MDC labeling, and an increase in the formation of autophagosomes as well as apoptosis, as evidenced by nuclear condensation and fragmentation. The activation of cathepsin B, D, and L, in addition to the release of cytochrome c and the relocation of AIF into nuclei, were observed after CrTX treatment. Autophagy inhibitors 3‐methyladenine (3‐MA), NH4Cl, and the pan‐caspase inhibitor, Z‐Val‐Ala‐Asp‐fluoromethylketone (Z‐Vad‐fmk), attenuated CrTX‐induced cell death. Conclusion: An autophagic mechanism contributes to the apoptosis of MCF‐7 cells induced by CrTX.

Anti-tumor activity of CrTX in human lung adenocarcinoma cell line A549

“…Previous studies have suggested that CrTX induces autophagy in human breast cancer MCF7 cells as a main mechanism for CrTX-induced cytotoxic effects [16] . In this study, we determined that CrTX induced cell apoptosis and cell cycle arrest in lung cancer A549 cells, suggesting distinct mechanisms for various types of cells.…”

Azithromycin reduces the viability of human bronchial smooth muscle cells

“…9 However, there is evidence that autophagy and apoptosis are not mutually exclusive. [24][25][26] Whether stress conditions will lead the cell to autophagy or apoptosis depends on the nature, intensity and duration of the effect, as well as the cell type and energy condition of the cell at the time that it received the effect. 27 Furthermore, although azithromycin displayed a dose-response effect on rabbit tracheal SMC proliferation, in concentrations 10 À6 -10 À5 M, 9 such a dose-dependent effect could not be observed on human bronchial SMCs.…”

Cisplatin-induced macroautophagy occurs prior to apoptosis in proximal tubules in vivo

“…Mizushima et al confirmed that over-expression of a fusion protein between green fluorescent protein and light chain 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 4 and in other cases induces apoptosis or type-2 programmed cell death [6][7][8]. Chronic myocardial ischemia/reperfusion injury induces autophagy increment and apoptosis decrement [9].…”