Abstract
BACKGROUND/OBJECTIVE: Ultraviolet (UV) B radiation leads to DNA damage by generating cyclobutane pyrimidine dimers (CPDs). UVB-induced CPDs can also result in immune suppression, which is a major risk factor for non-melanoma skin cancer (NMSC). UVB-induced CPDs are repaired by nucleotide repair mechanisms (NER) mediated by xeroderma pigmentosum complementation group A (XPA). The purpose of this study was to investigate the use of TH as a chemopreventive agent against the development of skin cancer. METHOD: SKH-1 hairless mice were exposed were fed with TH (0.1% v/v) for two weeks and exposed to a single dose of UVB (180 mJ/cm(2)). Dorsal skin was harvested 24 h post-UVB exposure for evaluation of DNA damage and repair. Lymph nodes were also harvested to prepare single cell suspension for flow cytometric evaluation. For carcinogenesis experiments, SKH-1 hairless mice were given TH (0.1% v/v) ad libitum and exposed to UVB (180 mJ/cm(2)) thrice a week for 30 weeks. RESULTS: Feeding SKH-1 hairless mice with TH (0.1% v/v) for two weeks prior to a single dose of UVB (180 mJ/cm(2)) led to a significant increase in XPA in skin and DNA repair cytokines IL-12 and IL-23 in draining lymph nodes. Furthermore, when subjected to the photocarcinogenesis protocol; mice fed with TH developed significantly fewer tumors in comparison to mice fed on drinking water. CONCLUSIONS: Our data demonstrate that TH has a protective effect against UVB-induced DNA damage, immune suppression, and skin cancer. Future studies will further investigate the potential of TH as a preventive treatment for NMSC.