CA9 and cancer: As top acetaminophen targets interacting with cancer-related genes, we identified the PTGS2 gene that encodes cyclooxygenase 2 (COX-2), an inducible isoform that catalyzes the committed step in prostaglandin synthesis; genes CYP3A4, CYP1A1, and CYP1A2 encode the cytochrome P450 superfamily of enzymes; and gene CA9 encodes carbonic anhydrase IX.