For example, CYP3A4 exhibits high interindividual variation in hepatic expression and the 5′ region upstream of CYP3A4 has highly variable CpG methylation sites in adult livers.29 Importantly, the methylation status of single CpG positions near the proximal promoter is associated with CYP3A4 expression.29 Furthermore, many cancers exhibit varied and aberrant epigenetic profiles, affecting chemotherapy response. The gene discussed is CYP3A4; the disease is cancer.