Increased expression of versican in the inflammatory response to UVB- and reactive oxygen species-induced skin tumorigenesis

Excessive exposure to UV radiation is a major risk factor for developing skin cancer. UV-induced reactive oxygen species (ROS) cause accumulation of DNA damage products such as 8-oxoguanine (8-oxoG) in the skin. We have previously shown that mice lacking the repair enzyme 8-oxoguanine glycosylase (Ogg1 knockout mice) are highly susceptible to skin cancer after long-term UVB exposure. To investigate the genes involved, we performed gene profiling of Ogg1 knockout mouse skin after UVB exposure. Among the up-regulated genes in UVB-treated Ogg1 knockout mice, inflammatory response pathway-related genes were most affected. The Vcan gene, which encodes the large extracellular matrix proteoglycan versican, was continuously up-regulated in UVB-treated Ogg1 knockout mice, suggesting that versican is a mediator of skin cancer development. We examined the expression pattern of versican in skin tumors from wild-type mice and UVB-treated Ogg1 knockout mice, and also analyzed 157 sun-related human skin tumors. Versican was strongly expressed in malignant skin tumors in both mice and humans, and especially in Ogg1 knockout mice. Additionally, infiltrating neutrophils strongly colocalized with versican in UVB-treated Ogg1 knockout mouse skin. These data demonstrate that inflammatory responses, particularly neutrophil infiltration and versican up-regulation, are closely involved in UVB/ROS-induced skin tumorigenesis.