HIF1A and head and neck squamous cell carcinoma: As shown in Fig. 4A, hypoxia led to an elevated level of miR-5100 in the exosomes secreted by HNSCC cells, whereas HIF1α knockdown impaired the hypoxia-induced enhancement, indicating that both the cellular and exosomal miR-5100 expressions were regulated by hypoxia/HIF1α.