title: Infrared radiation does not enhance the frequency of ultraviolet radiation-induced skin tumors, but their growth behaviour in mice.
abstract: There is increasing concern about the interaction between infrared radiation (IR) and ultraviolet radiation (UVR) with regard to carcinogenesis because prolonged solar exposure is associated with an increased cumulative load not only of UVR but also of IR. We recently demonstrated that IR-pretreatment reduces UVR-induced apoptosis. As this might support the survival of UVR-damaged cells and thus carcinogenesis, we performed an in vivo photocarcinogenesis study. One group of mice were treated with IR prior to each UVR exposure; additional groups were treated with IR or UVR alone. IR alone did not induce skin cancer. UVR-induced tumor formation was not enhanced in IR-pretreated mice, but, in contrast, seemed to occur with delay. This correlated with a reduction of p53 mutated clones in the skin. However, once developed, tumors in IR-pretreated mice grew faster which was confirmed by their enhanced Ki-67 expression. The enhanced aggressiveness of tumors derived from IR-pretreated mice was associated with a higher prevalence of sarcomas than epithelial tumors. Hence, the impact of IR on UVR-induced carcinogenesis has to be interpreted with caution. Although IR may delay the onset of UVR-induced tumors, it might contribute to a worse outcome by shifting these tumors into a more aggressive phenotype.
authors.affiliation: Department of Dermatology, University Kiel, Schittenhelmstrasse 7,Kiel, Germany. cjantschitsch@dermatology.uni-kiel.de
authors.forename: Christian
authors.initials: C
authors.lastname: Jantschitsch
authors.forename: Michael
authors.initials: M
authors.lastname: Weichenthal
authors.forename: Akira
authors.initials: A
authors.lastname: Maeda
authors.forename: Ehrhardt
authors.initials: E
authors.lastname: Proksch
authors.forename: Thomas
authors.initials: T
authors.lastname: Schwarz
authors.forename: Agatha
authors.initials: A
authors.lastname: Schwarz
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000209:etiology* / Q000473:pathology; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects; D004249:DNA Damage; D005260:Female; D016158:Genes, p53 / Q000235:genetics; D007259:Infrared Rays / Q000009:adverse effects*; D053208:Kaplan-Meier Estimate; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D009381:Neoplasms, Radiation-Induced / Q000209:etiology* / Q000473:pathology; D012509:Sarcoma / Q000209:etiology* / Q000473:pathology; D012878:Skin Neoplasms / Q000209:etiology* / Q000473:pathology; D013472:Sunlight / Q000009:adverse effects; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D019394:Ki-67 Antigen