The contribution of CYP27B1 to 25D3 activities in EGFR mutant lung cancer has not been investigated previously but is important to understand because CYP27B1 expression is significantly decreased in EGFR mutant lung cancer cells and xenografts by erlotinib (supplemental microarray data in [19]), which is used as first-line therapy in patients diagnosed with EGFR mutant lung cancer [20]. The gene discussed is CYP27B1; the disease is lung carcinoma.