Oncogenes and Tumor Suppressors MIF Antagonist (CPSI-1306) Protects against UVB-Induced Squamous Cell Carcinoma

Macrophage migration inhibitory factor (MIF) is a homotrimeric proinflammatory cytokine implicated in chronic inflammatory diseases and malignancies, including cutaneous squamous cell carcinomas (SCC). To determinewhetherMIF inhibition could reduceUVB light–induced inflammation and squamous carcinogenesis, a small-molecule MIF inhibitor (CPSI-1306) was utilized that disrupts homotrimerization. To examine the effect of CPSI-1306 on acute UVB-induced skin changes, Skh-1 hairless mice were systemically treated with CPSI-1306 for 5 days before UVB exposure. In addition to decreasing skin thickness and myeloperoxidase (MPO) activity, CPSI1306 pretreatment increased keratinocyte apoptosis and p53 expression, decreased proliferation and phosphohistone variant H2AX (g-H2AX), and enhanced repair of cyclobutane pyrimidine dimers. To examine the effect of CPSI-1306 on squamous carcinogenesis, mice were exposed to UVB for 10 weeks, followed by CPSI-1306 treatment for 8 weeks. CPSI-1306 dramatically decreased the density of UVB-associated p53 foci in non–tumorbearing skin while simultaneously decreasing the epidermal Ki67 proliferation index. In addition to slowing the rate of tumor development, CPSI-1306 decreased the average tumor burden per mouse. Although CPSI-1306–treated mice developed only papillomas, nearly a third of papillomas in vehicle-treated mice progressed to microinvasive SCC. Thus, MIF inhibition is a promising strategy for prevention of the deleterious cutaneous effects of acute and chronic UVB exposure. Implications: Macrophage migration inhibitory factor is a viable target for the prevention of UVB-induced cutaneous SSCs. Mol Cancer Res; 12(9); 1292–302. 2014 AACR.