Differential inhibition of protein translation machinery by curcumin in normal, immortalized, and malignant oral epithelial cells.
Curcumin has shown some promise in the prevention of oral carcinogenesis by mechanism(s) that are still not completely resolved. Messenger RNA translation is mediated in eukaryotes by the eIF4F complex composed of eukaryotic translation initiation factors eIF4E, eIF4G, and eIF4A. Overexpression of some of these components or the inactivation of initiation repressor proteins (4E-BP1) has been implicated in cancer development including oral carcinogenesis by affecting cell survival, angiogenesis, and tumor growth and invasion. In this study, we examined the possibility that curcumin affects the translational machinery differently in normal, immortalized normal, leukoplakia, and malignant cells. Curcumin treatment in vitro inhibited the growth of immortalized oral mucosa epithelial cells (NOM9-CT) and the leukoplakia cells (MSK-Leuk1s) as well as in the UMSCC22B and SCC4 cells derived from head and neck squamous cell carcinoma. Curcumin only exerted minor effects on the growth of normal oral epithelial cells (NOM9). In the immortalized, leukoplakia, and cancer cells, curcumin inhibited cap-dependent translation by suppressing the phosphorylation of 4E-BP1, eIF4G, eIF4B, and Mnk1, and also reduced the total levels of eIF4E and Mnk1. Our findings show that immortalized normal, leukoplakia, and malignant oral cells are more sensitive to curcumin and show greater modulation of protein translation machinery than the normal oral cells, indicating that targeting this process may be an important approach to chemoprevention in general and for curcumin in particular.
Chakravarti
Nitin
N
Department of Thoracic/Head and Neck Medical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Kadara
Humam
H
Yoon
Do-Jun
DJ
Shay
Jerry W
JW
Myers
Jeffrey N
JN
Lotan
Dafna
D
Sonenberg
Nahum
N
Lotan
Reuben
R
D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed / Q000166:cytology / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003474:Curcumin / Q000494:pharmacology*; D039603:Eukaryotic Initiation Factor-4G / Q000037:antagonists & inhibitors / Q000378:metabolism; D039642:Eukaryotic Initiation Factors / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D009061:Mouth Mucosa / Q000187:drug effects*; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects*; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011230:Precancerous Conditions / Q000188:drug therapy* / Q000473:pathology; D014176:Protein Biosynthesis / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; C113920:EIF4G1 protein, human; D039603:Eukaryotic Initiation Factor-4G; D039642:Eukaryotic Initiation Factors; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; C031799:eIF-4B; C491395:MKNK1 protein, human; D017346:Protein Serine-Threonine Kinases; D003474:Curcumin