Pathways with higher degree values not only involve cancer pathways but also involve lipids and atherosclerosis, Kaposi’s sarcoma-associated herpesvirus infection, the PI3K–Akt signaling pathway, hepatitis B, the HIF-1 signaling pathway, endocrine resistance, EGFR tyrosine kinase inhibitor resistance, the FoxO signaling pathway, the AGE–RAGE signaling pathway in diabetic complications, apoptosis, the ErbB signaling pathway, the sphingolipid signaling pathway, the neurotrophin signaling pathway, and insulin resistance. The gene discussed is PIK3CA; the disease is hepatitis B virus infection.