Overexpression of 5-lipoxygenase and cyclooxygenase 2 in hamster and human oral cancer and chemopreventive effects of zileuton and celecoxib.
OBJECTIVE
Previous studies have suggested an important role of aberrant arachidonic acid metabolism, especially the cyclooxygenase (Cox) pathway, in oral carcinogenesis. However, it is unknown whether the 5-lipoxygenase (5-Lox) pathway contributes to oral carcinogenesis, and whether combination of inhibitors of both pathways may have synergistic or additive effects of chemoprevention.


METHODS
5-Lox expression was examined in 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster and human oral cancer tissues by immunohistochemistry, and Cox2 expression was investigated in hamster oral tissues using in situ hybridization. Zileuton (a specific 5-Lox inhibitor) and celecoxib (a specific Cox2 inhibitor), either alone or in combination, were investigated for their chemopreventive effects on the DMBA-induced hamster model at the post-initiation stage through topical application.


RESULTS
5-Lox was overexpressed during oral carcinogenesis in hamsters and humans, as well as Cox2 in the hamster tissues. In a chemoprevention study using the post-initiation DMBA model, incidence of hamster oral squamous cell carcinoma was reduced from 76.9% (20 of 26) to 45.8% (11 of 24, P < 0.05) and 32.1% (9 of 28, P < 0.01) by 3% and 6% topical zileuton, respectively; and to 57.6% (15 of 26, P > 0.05) and 50% (12 of 24, P < 0.05) by 3% and 6% topical celecoxib, respectively. When used in combination, celecoxib and zileuton (3% of each) had an additive inhibitory effect on the incidence of squamous cell carcinoma (36%, 9 of 25, P < 0.01). Other pathologic variables and the levels of leukotriene B4 and prostaglandin E2 of the hamster tissues were reduced as well.


CONCLUSIONS
The results clearly showed that both 5-Lox and Cox2 played important roles in oral carcinogenesis. Zileuton and celecoxib prevented oral carcinogenesis at the post-initiation stage through their inhibitory effects on arachidonic acid metabolism.
Li
Ning
N
Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers-State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Sood
Sandeep
S
Wang
Su
S
Fang
Mingzhu
M
Wang
Peng
P
Sun
Zheng
Z
Yang
Chung S
CS
Chen
Xiaoxin
X
D015127:9,10-Dimethyl-1,2-benzanthracene / Q000008:administration & dosage; D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000096:biosynthesis*; D016718:Arachidonic Acid / Q000378:metabolism; D002273:Carcinogens / Q000008:administration & dosage; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000503:physiopathology / Q000517:prevention & control*; D000068579:Celecoxib; D002471:Cell Transformation, Neoplastic; D018890:Chemoprevention; D006224:Cricetinae; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004195:Disease Models, Animal; D006801:Humans; D006918:Hydroxyurea / Q000031:analogs & derivatives* / Q000494:pharmacology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D008297:Male; D008565:Membrane Proteins; D008647:Mesocricetus; D009062:Mouth Neoplasms / Q000235:genetics* / Q000503:physiopathology / Q000517:prevention & control*; D009374:Neoplasms, Experimental; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D011720:Pyrazoles / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*; D015854:Up-Regulation
D002273:Carcinogens; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D016859:Lipoxygenase Inhibitors; D008565:Membrane Proteins; D011720:Pyrazoles; D013449:Sulfonamides; D016718:Arachidonic Acid; D015127:9,10-Dimethyl-1,2-benzanthracene; D001094:Arachidonate 5-Lipoxygenase; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D000068579:Celecoxib; C063449:zileuton; D006918:Hydroxyurea