IGF-I protects human oral buccal mucosal epithelial cells from sodium nitroprusside-induced apoptosis via PI3-kinase.
OBJECTIVE
Cancers of the head and neck account for the vast majority of all malignancies of the oral cavity. The insulin-like growth factor (IGF) family of proteins is well documented to have an important role in rescuing cells from apoptosis. While it is known the IGF proteins are present in normal oral epithelial and cancer cells its role is not fully understood. Our aim was to study the ability of IGFs to rescue sodium nitroprusside (SNP)-induced apoptotic normal oral epithelial cells in vitro.


METHODS
Cultured normal human oral keratinocytes (NOKs) or epithelial cells were used. Apoptosis was induced by SNP then cells were exposed to IGF-I or IGF-II to rescue them. Cell viability was assessed by ELISA (for cell death and caspase 3) and FACS analysis; post receptor effects of IGF-I or IGF-II were assessed by [(3)H] thymidine incorporation. Cell signaling events were measured by western blotting using antibodies against phosphorylated Akt or p42/p44 MAPK, and measuring PI3-K activity by ELISA.


RESULTS
SNP induced apoptosis of NOKs and activated the PI3-K/Akt survival pathway. Exposing cells to IGF proteins prevented their apoptosis. IGF-I and -II caused significant increases in PI3-K, but not MAPK, activity. SNP and LY294002, a PI3-K inhibitor, both caused a significant rise in caspase 3 release from NOKs which was reduced in the presence of IGFs.


CONCLUSIONS
The data establishes the importance of IGF-activated PI3-K in rescuing cells from apoptosis. It lends further evidence to the significance of IGF proteins in the possible development of oral cancer.
Brady
Garrett
G
Maxillofacial Department, Leeds Dental Institute, Clarendon Way, Leeds LS2 9LU, UK. garrettbrady@hotmail.com
Crean
St John
SJ
Lorenzon
Ana
A
Kapas
Supriya
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D019610:Cytoprotection / Q000187:drug effects* / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D015603:Keratinocytes / Q000187:drug effects; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D009061:Mouth Mucosa / Q000187:drug effects*; D009570:Nitriles / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D041701:Swiss 3T3 Cells
D002070:Butadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D009025:Morpholines; D009570:Nitriles; D009599:Nitroprusside; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C113580:U 0126; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one