To address these questions, ERα-positive (UM-SCC-12) and ERα-negative (UM-SCC-11A) laryngeal cancer cell lines were examined for the presence of ERα66; the enzymes responsible for metabolizing 25(OH)D3 (CYP24A1 and CYP27B1); the local production of 24,25(OH)2D3 and 1,25(OH)2D3; and the effect of 24R,25(OH)2D3 on cell growth and markers of metastasis. The gene discussed is CYP24A1; the disease is laryngeal carcinoma.