In seeming contradiction with those described above, an additional level of complexity was added to lipid raft-mediated effects on ErbB function by studies demonstrating upregulation of cholesterol biosynthesis and elevated cholesterol levels in lipid rafts of human lung and breast cancer cell lines treated with EGFR tyrosine kinase inhibitors (TKI), which correlated with resistance to this treatment. The gene discussed is EGFR; the disease is breast carcinoma.