Vorinostat and sorafenib increase CD95 activation in gastrointestinal tumor cells through a Ca(2+)-de novo ceramide-PP2A-reactive oxygen species-dependent signaling pathway.
The targeted therapeutics sorafenib and vorinostat interact in a synergistic fashion to kill carcinoma cells by activating CD95, and this drug combination is entering phase I evaluation. In this study, we determined how CD95 is activated by treatment with this drug combination. Low doses of sorafenib and vorinostat, but not the individual drugs, rapidly increased reactive oxygen species (ROS), Ca(2+), and ceramide levels in gastrointestinal tumor cells. The production of ROS was reduced in Rho zero cells. Quenching ROS blocked drug-induced CD95 surface localization and apoptosis. ROS generation, CD95 activation, and cell killing was also blocked by quenching of induced Ca(2+) levels or by inhibition of PP2A. Inhibition of acidic sphingomyelinase or de novo ceramide generation blocked the induction of ROS; however, combined inhibition of both acidic sphingomyelinase and de novo ceramide generation was required to block the induction of Ca(2+). Quenching of ROS did not affect drug-induced ceramide/dihydro-ceramide levels, whereas quenching of Ca(2+) reduced the ceramide increase. Sorafenib and vorinostat treatment radiosensitized liver and pancreatic cancer cells, an effect that was suppressed by quenching ROS or knockdown of LASS6. Further, sorafenib and vorinostat treatment suppressed the growth of pancreatic tumors in vivo. Our findings show that induction of cytosolic Ca(2+) by sorafenib and vorinostat is a primary event that elevates dihydroceramide levels, each essential steps in ROS generation that promotes CD95 activation.
Park
Margaret A
MA
Department of Biochemistry, Virginia Commonwealth University, Richmond, Virginia 23298-0035, USA.
Mitchell
Clint
C
Zhang
Guo
G
Yacoub
Adly
A
Allegood
Jeremy
J
Häussinger
Dieter
D
Reinehr
Roland
R
Larner
Andrew
A
Spiegel
Sarah
S
Fisher
Paul B
PB
Voelkel-Johnson
Christina
C
Ogretmen
Besim
B
Grant
Steven
S
Dent
Paul
P
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001557:Benzenesulfonates / Q000008:administration & dosage / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism; D005770:Gastrointestinal Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000077157:Sorafenib; D000077337:Vorinostat; D019014:fas Receptor / Q000378:metabolism*
D001557:Benzenesulfonates; D002518:Ceramides; D006877:Hydroxamic Acids; D010671:Phenylurea Compounds; D011725:Pyridines; D017382:Reactive Oxygen Species; D019014:fas Receptor; D009536:Niacinamide; D000077337:Vorinostat; D000077157:Sorafenib; D002265:Carboxylic Ester Hydrolases; C119357:protein phosphatase methylesterase-1; D002118:Calcium