High cholesterol diet mainly promoted colonization of tumor cells in lung tissue, which was restrained by Cyp27A1 knockdown and strengthened by Cyp7B1 knockdown (Figs. 6C, 6s-B), consistent with Hematoxylin and Eosin (HE) staining (Fig. 6D). The gene discussed is CYP27A1; the disease is neoplasm.