PIK3CA and cancer: In mammals, miR-124 participates in the development and progression of cancer, nervous system, and host–pathogen: miR-124 inhibits cell proliferation in hepatocellular carcinoma by targeting PIK3CA and plays important roles in many cancers via the inhibition of PI3K/Akt pathway (19); miR-124 in the brain plays a key role in neurogenesis, neuronal differentiation, and synaptic plasticity in adults (20, 21); and miR-124 has a broad spectrum antiviral activity against influenza A virus (IAV) and respiratory syncytial virus (RSV) (22).