Cisplatin induces endoplasmic reticulum stress and nucleus-independent apoptotic signaling.
DNA damage is believed to be the main cause of the antiproliferative effect of cisplatin, a cornerstone agent in anticancer therapy. However, cisplatin can be expected to react also with nucleophiles other than DNA. Using enucleated cells (cytoplasts) we demonstrate here that cisplatin-induced apoptotic signaling may occur independently of DNA damage. Cisplatin-induced caspase-3 activation in cytoplasts required calcium and the activity of the calcium-dependent protease calpain. It is known that calpain activation may be associated with endoplasmic reticulum (ER) stress, suggesting that the ER is a cytosolic target of cisplatin. Consistent with this hypothesis, cisplatin induced calpain-dependent activation of the ER-specific caspase-12 in cytoplasts as well as in intact cells. Cisplatin also induced increased expression of Grp78/BiP, another marker of ER stress. By contrast, the DNA-damaging topoisomerase II inhibitor etoposide did not induce apoptotic signaling in cytoplasts nor ER stress in intact cells. We have thus identified a novel mechanism of action of cisplatin. The results have implications for the understanding of resistance mechanisms as well as the unique efficiency of this drug.
Mandic
Aleksandra
A
Department of Oncology-Pathology, CancerCenterKarolinska, Karolinska Institute and Hospital, S-171 76 Stockholm, Sweden.
Hansson
Johan
J
Linder
Stig
S
Shoshan
Maria C
MC
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002945:Cisplatin / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D004249:DNA Damage; D004721:Endoplasmic Reticulum / Q000187:drug effects*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005434:Flow Cytometry; D006360:Heat-Shock Proteins; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D005047:Etoposide; C505407:CASP3 protein, human; D002154:Calpain; D053148:Caspase 3; D020169:Caspases; D002945:Cisplatin; D002118:Calcium