Topical treatment of calcipotriol, a TSLP inducer (75), blocks skin cancer development in mice in a TSLP-dependent manner, and synergistically with 5-fluorouracil (5-FU) induces an effective CD4+ T cell-mediated immunity against actinic keratosis, which is a precursor to cutaneous squamous cell carcinoma in humans (190). The gene discussed is TSLP; the disease is actinic keratosis.