Paclitaxel induces apoptosis in Saos-2 cells with CD95L upregulation and Bcl-2 phosphorylation.
We examined the effect of paclitaxel on human osteoblastic cells Saos-2 to determine if paclitaxel can affect proliferation and apoptosis. We used a p53-negative cell line in order to mimic the loss of function frequently observed at the clinical level. Paclitaxel induced cell death in a dose- and time-dependent manner. Marked nuclear condensation and fragmentation of chromatin were observed by Hoechst 33258 stain, DNA ladder formation, electron microscopy, and flow cytometry at concentrations as low as 100 nM, a concentration which can be achieved by infusion in human plasma. At 100 nM, paclitaxel induced a G2 arrest at 8 h of treatment. The cells then continued to accumulate in G2 until 72 h when the percentage of apoptotic events reached 54%. At the molecular level, Bcl-2 protein was phosphorylated at 16 h and PARP protein was cleaved, indicating the activation of caspase-3-like proteases. Caspase inhibitors Z-VAD-FMK and Z-DEVD-FMK rescued Saos-2 cells from paclitaxel-induced apoptosis. CD95 expression was constantly high, while CD95L showed a threefold increase in expression. This suggests that, following the G2 arrest, apoptosis is induced through the CD95/CD95L system.
Pucci
B
B
Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.
Bellincampi
L
L
Tafani
M
M
Masciullo
V
V
Melino
G
G
Giordano
A
A
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology / Q000502:physiology*; D020169:Caspases / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D053222:Fas Ligand Protein; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D008854:Microscopy, Electron; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D012516:Osteosarcoma / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects; D019014:fas Receptor / Q000378:metabolism
D000972:Antineoplastic Agents, Phytogenic; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D019014:fas Receptor; D020169:Caspases; D017239:Paclitaxel