title: Protective role of Toll-like receptor 4 during the initiation stage of cutaneous chemical carcinogenesis.
abstract: Toll-like receptors (TLR) activate multiple steps in inflammatory reactions in innate immune responses. They also activate signals that are critically involved in the initiation of adaptive immune responses. Many tumorigenic chemicals have been associated with endotoxin hypersensitivity mediated through TLR4. To determine the role of TLR4 in cutaneous skin carcinogenesis, we treated TLR4-deficient C3H/HeJ mice and the TLR4-normal C3H/HeN mice with the carcinogenic polyaromatic hydrocarbon 7,12-dimethylbenz(a)anthracene (DMBA). TLR4-deficient C3H/HeJ mice developed more tumors relative to the TLR4-normal C3H/HeN mice. Both C3H/HeN and C3H/HeJ mice developed a T-cell-mediated immune response to topically applied DMBA. Interestingly, the cell-mediated immune response was mediated by IFN-gamma in C3H/HeN mice and by interleukin (IL)-17 in C3H/HeJ mice. Moreover, C3H/HeN mice had elevated circulating levels of IFN-gamma following topical application of DMBA, whereas IL-17 was elevated in C3H/HeJ mice. The results of this study indicate that TLR4 plays an important role in the prevention of DMBA skin tumorigenesis and that this is associated with differences in the T-cell subtype activated. Efforts to divert the cell-mediated immune response from one that is IL-17 mediated to one that is IFN-gamma mediated may prove to be beneficial in the prevention of DMBA-induced cutaneous tumors.
authors.affiliation: Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, 1670 University Boulevard, VH 566A, P. O. Box 202, Birmingham, AL 35294-0019, USA. nabiha@uab.edu
authors.forename: Nabiha
authors.initials: N
authors.lastname: Yusuf
authors.forename: Tahseen H
authors.initials: TH
authors.lastname: Nasti
authors.forename: J Alan
authors.initials: JA
authors.lastname: Long
authors.forename: Mohammed
authors.initials: M
authors.lastname: Naseemuddin
authors.forename: Alan P
authors.initials: AP
authors.lastname: Lucas
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Craig A
authors.initials: CA
authors.lastname: Elmets
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000818:Animals; D002273:Carcinogens / Q000633:toxicity; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019610:Cytoprotection / Q000235:genetics*; D003877:Dermatitis, Contact / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D018664:Interleukin-12 / Q000378:metabolism; D053759:Interleukin-23 / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D018345:Mice, Knockout; D009389:Neovascularization, Pathologic / Q000235:genetics; D012878:Skin Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000517:prevention & control*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000502:physiology*
chemical_list: D002273:Carcinogens; D053759:Interleukin-23; D051197:Toll-Like Receptor 4; D018664:Interleukin-12; D015127:9,10-Dimethyl-1,2-benzanthracene