PIK3CA and head and neck squamous cell carcinoma: lncRNAs play critical roles in promoting metastasis and invasion in HNSCC by inducing epithelial–mesenchymal transition, remodeling the extracellular matrix, and activating oncogenic signaling pathways, such as PI3K/AKT/mTOR, Wnt/β-catenin, and TGF-β (Figure 2).