Bcl-2 siRNA augments taxol mediated apoptotic death in human glioblastoma U138MG and U251MG cells.
The anti-neoplastic drug taxol binds to beta-tubulin to prevent tumor cell division, promoting cell death. However, high dose taxol treatment may induce cell death in normal cells too. The anti-apoptotic molecule Bcl-2 is upregulated in many cancer cells to protect them from apoptosis. In the current study, we knocked down Bcl-2 expression using cognate siRNA during low-dose taxol treatment to induce apoptosis in two human glioblastoma U138MG and U251MG cell lines. The cells were treated with either 100 nM taxol or 100 nM Bcl-2 siRNA or both for 72 h. Immunofluorescent stainings for calpain and active caspase-3 showed increases in expression and co-localization of these proteases in apoptotic cells. Fluorometric assays demonstrated increases in intracellular free [Ca(2+)], calpain, and caspase-3 indicating augmentation of apoptosis. Western blotting demonstrated dramatic increases in the levels of Bax, Bak, tBid, active caspases, DNA fragmentation factor-40 (DFF40), cleaved fragments of lamin, fodrin, and poly(ADP-ribose) polymerase (PARP) during apoptosis. The events related to apoptosis were prominent more in combination therapy than in either treatment alone. Our current study demonstrated that Bcl-2 siRNA significantly augmented taxol mediated apoptosis in different human glioblastoma cells through induction of calpain and caspase proteolytic activities. Thus, combination of taxol and Bcl-2 siRNA offers a novel therapeutic strategy for controlling the malignant growth of human glioblastoma cells.
George
Joseph
J
Department of Neurosciences, Medical University of South Carolina, 96 Jonathan Lucas Street, Charleston, SC, 29425, USA.
Banik
Naren L
NL
Ray
Swapan K
SK
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000235:genetics; D053148:Caspase 3 / Q000235:genetics; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005455:Fluorescent Antibody Technique; D005909:Glioblastoma / Q000188:drug therapy / Q000473:pathology*; D006801:Humans; D020287:In Situ Nick-End Labeling; D017239:Paclitaxel / Q000494:pharmacology* / Q000627:therapeutic use; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D034741:RNA, Small Interfering / Q000494:pharmacology* / Q000627:therapeutic use
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D045304:Cytochromes c; D002154:Calpain; D053148:Caspase 3; D017239:Paclitaxel; D002118:Calcium