title: Prevention of upper aerodigestive tract cancer in zinc-deficient rodents: inefficacy of genetic or pharmacological disruption of COX-2.
abstract: Zinc deficiency in humans is associated with an increased risk of upper aerodigestive tract (UADT) cancer. In rodents, zinc deficiency predisposes to carcinogenesis by causing proliferation and alterations in gene expression. We examined whether in zinc-deficient rodents, targeted disruption of the cyclooxygenase (COX)-2 pathway by the COX-2 selective inhibitor celecoxib or by genetic deletion prevent UADT carcinogenesis. Tongue cancer prevention studies were conducted in zinc-deficient rats previously exposed to a tongue carcinogen by celecoxib treatment with or without zinc replenishment, or by zinc replenishment alone. The ability of genetic COX-2 deletion to protect against chemically-induced forestomach tumorigenesis was examined in mice on zinc-deficient versus zinc-sufficient diet. The expression of 3 predictive biomarkers COX-2, nuclear factor (NF)-kappa B p65 and leukotriene A(4) hydrolase (LTA(4)H) was examined by immunohistochemistry. In zinc-deficient rats, celecoxib without zinc replenishment reduced lingual tumor multiplicity but not progression to malignancy. Celecoxib with zinc replenishment or zinc replenishment alone significantly lowered lingual squamous cell carcinoma incidence, as well as tumor multiplicity. Celecoxib alone reduced overexpression of the 3 biomarkers in tumors slightly, compared with intervention with zinc replenishment. Instead of being protected, zinc-deficient COX-2 null mice developed significantly greater tumor multiplicity and forestomach carcinoma incidence than wild-type controls. Additionally, zinc-deficient COX-2-/- forestomachs displayed strong LTA(4)H immunostaining, indicating activation of an alternative pathway under zinc deficiency when the COX-2 pathway is blocked. Thus, targeting only the COX-2 pathway in zinc-deficient animals did not prevent UADT carcinogenesis. Our data suggest zinc supplementation should be more thoroughly explored in human prevention clinical trials for UADT cancer.
authors.affiliation: Department of Molecular Virology, Immunology, and Medical Genetics, Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA. louise.fong@osumc.edu
authors.forename: Louise Y Y
authors.initials: LY
authors.lastname: Fong
authors.forename: Yubao
authors.initials: Y
authors.lastname: Jiang
authors.forename: Maurisa
authors.initials: M
authors.lastname: Riley
authors.forename: Xianglan
authors.initials: X
authors.lastname: Liu
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Smalley
authors.forename: Denis C
authors.initials: DC
authors.lastname: Guttridge
authors.forename: John L
authors.initials: JL
authors.lastname: Farber
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000633:toxicity; D002294:Carcinoma, Squamous Cell / Q000139:chemically induced / Q000209:etiology / Q000517:prevention & control*; D000068579:Celecoxib; D051546:Cyclooxygenase 2 / Q000172:deficiency* / Q000187:drug effects / Q000235:genetics; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D004938:Esophageal Neoplasms / Q000139:chemically induced / Q000517:prevention & control; D006258:Head and Neck Neoplasms / Q000139:chemically induced / Q000209:etiology / Q000517:prevention & control*; D007150:Immunohistochemistry; D017572:Leukotriene A4 / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000494:pharmacology; D014062:Tongue Neoplasms / Q000139:chemically induced / Q000517:prevention & control; D051996:Transcription Factor RelA / Q000378:metabolism; D015032:Zinc / Q000172:deficiency*
chemical_list: D002273:Carcinogens; D052246:Cyclooxygenase 2 Inhibitors; D017572:Leukotriene A4; D011720:Pyrazoles; D013449:Sulfonamides; D051996:Transcription Factor RelA; D051546:Cyclooxygenase 2; C489691:Ptgs2 protein, rat; D015032:Zinc; D000068579:Celecoxib