Deficient deletion of apoptotic cells by macrophage migration inhibitory factor (MIF) overexpression accelerates photocarcinogenesis.
Chronic ultraviolet (UV) exposure can increase the occurrence of p53 mutations, thus leading to a dysregulation of apoptosis and the initiation of skin cancer. Therefore, it is extremely important that apoptosis is induced quickly after UV irradiation, without any dysregulation. Recent studies have suggested a potentially broader role for macrophage migration inhibitory factor (MIF) in growth regulation via its ability to antagonize p53-mediated gene activation and apoptosis. To further elucidate the possible role of MIF in photocarcinogenesis, the acute and chronic UVB effect in the skin was examined using macrophage migration inhibitory factor transgenic (MIF Tg) and wild-type (WT) mice. The MIF Tg mice exposed to chronic UVB irradiation began to develop skin tumors after approximately 14 weeks, whereas the WT mice began to develop tumors after 18 weeks. A higher incidence of tumors was observed in the MIF Tg in comparison with the WT mice after chronic UVB irradiation. Next, we clarified whether the acceleration of photo-induced carcinogenesis in the MIF Tg mice was mediated by the inhibition of apoptosis There were fewer sunburned cells in the epidermis of the MIF Tg mice than the WT mice after acute UVB exposure. The epidermis derived from the MIF Tg mice exhibited substantially decreased levels of p53, bax and p21 after UVB exposure in comparison with the WT mice. Collectively, these findings suggest that chronic UVB exposure enhances MIF production, which may inhibit the p53-dependent apoptotic processes and thereby induce photocarcinogenesis in the skin.
Honda
Ayumi
A
Department of Dermatology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Sugitani, Toyama 930-0194, Japan.
Abe
Riichiro
R
Yoshihisa
Yoko
Y
Makino
Teruhiko
T
Matsunaga
Kenji
K
Nishihira
Jun
J
Shimizu
Hiroshi
H
Shimizu
Tadamichi
T
D000818:Animals; D017209:Apoptosis; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000032:analysis; D004249:DNA Damage; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008263:Macrophage Migration-Inhibitory Factors / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D008822:Mice, Transgenic; D009381:Neoplasms, Radiation-Induced / Q000209:etiology*; D012878:Skin Neoplasms / Q000209:etiology*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D014466:Ultraviolet Rays / Q000009:adverse effects*; D051028:bcl-2-Associated X Protein / Q000502:physiology
C494827:Bax protein, mouse; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D008263:Macrophage Migration-Inhibitory Factors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein