Increased susceptibility of breast cancer cells to stress mediated inhibition of protein synthesis.
Protein synthesis is a tightly controlled process, and its deregulation plays an important role in tumorigenesis. Protein synthesis remains poorly understood with very few well-identified validated targets for therapeutic purposes. In this study, we use nitric oxide (NO), which suppresses protein synthesis by inactivating eukaryotic initiation factor 2-alpha (eIF2-alpha), to examine the mechanism by which low and high oxidative stress inhibits protein synthesis. In breast cancer cells, low NO stress induced heme-regulated inhibitor (HRI) activation, which facilitated gradual decline in short half-life proteins. High NO stress induced HRI and protein kinase R (PKR) activation, leading to a sharp decline in protein synthesis as accessed by a decline in short and long half-life proteins and dramatic morphologic changes. In contrast, human mammary epithelial (HME) and Ras transfected untransformed HME (MCF-10A1 neo N) cells were less susceptible to NO-induced inhibition of protein synthesis and cytostasis. Our results suggest that NO-induced cytostasis in breast cancer cells was due to PKR activation and increased phosphorylation of eIF2-alpha, whereas the reduced susceptibility of normal mammary epithelial cells to NO could be due to the inaccessibility of PKR, which is bound to inhibitor p58.
Pervin
Shehla
S
Department of Obstetrics and Gynecology, David Geffen School of Medicine at University of California, Los Angeles, USA. spervin@mednet.ucla.edu
Tran
An H
AH
Zekavati
Shaghayegh
S
Fukuto
Jon M
JM
Singh
Rajan
R
Chaudhuri
Gautam
G
D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001940:Breast / Q000166:cytology / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D015852:Eukaryotic Initiation Factor-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology; D011905:Genes, ras / Q000502:physiology; D006418:Heme / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D047468:Immunoprecipitation; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D010766:Phosphorylation / Q000187:drug effects; D014176:Protein Biosynthesis / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism
D016895:Culture Media, Serum-Free; D015852:Eukaryotic Initiation Factor-2; D016166:Free Radical Scavengers; D016877:Oxidants; D034741:RNA, Small Interfering; D009569:Nitric Oxide; D006418:Heme; D006861:Hydrogen Peroxide; D019892:eIF-2 Kinase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D006152:Cyclic GMP