Analyses of these cell lines revealed that a loss of squalene epoxidase expression (SQLE, aka squalene monooxygenase, ALK+ ALCL cells), through hypermethylation of its promoter region, or 3-ketosteroid reductase expression (HSD17B7, U937 cells), through a mutational defect, rendered the cells auxotrophic for cholesterol. The gene discussed is ALK; the disease is anaplastic large cell lymphoma.