Ceramide plays a prominent role in MDA-7/IL-24-induced cancer-specific apoptosis.
Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) uniquely displays broad cancer-specific apoptosis-inducing activity through induction of endoplasmic reticulum (ER) stress. We hypothesize that ceramide, a promoter of apoptosis, might contribute to mda-7/IL-24 induction of apoptosis. Ad.mda-7-infected tumor cells, but not normal cells, showed increased ceramide accumulation. Infection with Ad.mda-7 induced a marked increase in various ceramides (C16, C24, C24:1) selectively in prostate cancer cells. Inhibiting the enzyme serine palmitoyltransferase (SPT) using the potent SPT inhibitor myriocin (ISP1), impaired mda-7/IL-24-induced apoptosis and ceramide production, suggesting that ceramide formation caused by Ad.mda-7 occurs through de novo synthesis of ceramide and that ceramide is required for mda-7/IL-24-induced cell death. Fumonisin B1 (FB1) elevated ceramide formation as well as apoptosis induced by Ad.mda-7, suggesting that ceramide formation may also occur through the salvage pathway. Additionally, Ad.mda-7 infection enhanced expression of acid sphingomyelinase (ASMase) with a concomitant increase in ASMase activity and decreased sphingomyelin in cancer cells. ASMase silencing by RNA interference inhibited the decreased cell viability and ceramide formation after Ad.mda-7 infection. Ad.mda-7 activated protein phosphatase 2A (PP2A) and promoted dephosphorylation of the anti-apoptotic molecule BCL-2, a downstream ceramide-mediated pathway of mda-7/IL-24 action. Pretreatment of cells with FB1 or ISP-1 abolished the induction of ER stress markers (BiP/GRP78, GADD153 and pospho-eIF2alpha) triggered by Ad.mda-7 infection indicating that ceramide mediates ER stress induction by Ad.mda-7. Additionally, recombinant MDA-7/IL-24 protein induced cancer-specific production of ceramide. These studies define ceramide as a key mediator of an ER stress pathway that may underlie mda-7/IL-24 induction of cancer-specific killing.
Sauane
Moira
M
Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, Virginia.
Su
Zao-Zhong
ZZ
Dash
Rupesh
R
Liu
Xiang
X
Norris
James S
JS
Sarkar
Devanand
D
Lee
Seok-Geun
SG
Allegood
Jeremy C
JC
Dent
Paul
P
Spiegel
Sarah
S
Fisher
Paul B
PB
D017209:Apoptosis / Q000187:drug effects; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival; D002518:Ceramides / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D037341:Fumonisins / Q000494:pharmacology; D006801:Humans; D007378:Interleukins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D054648:Protein Phosphatase 2 / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034622:RNA Interference; D011994:Recombinant Proteins / Q000378:metabolism; D051102:Serine C-Palmitoyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000378:metabolism; D013109:Sphingomyelins / Q000378:metabolism; D013312:Stress, Physiological; D013997:Time Factors; D014161:Transduction, Genetic; D015854:Up-Regulation; D000099180:Interleukin-24
D002518:Ceramides; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; D005229:Fatty Acids, Monounsaturated; D037341:Fumonisins; D007378:Interleukins; D054648:Protein Phosphatase 2; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D051102:Serine C-Palmitoyltransferase; D013108:Sphingomyelin Phosphodiesterase; D013109:Sphingomyelins; D000099180:Interleukin-24; C000717247:HSPA5 protein, human; C056933:fumonisin B1; C001996:thermozymocidin