CHRNA5 and oral cavity squamous cell carcinoma: The divergent loop structures of nicotinic acetylcholine receptor (nAChR) α3, α5, and α7 subunits (encoded by CHRNA3, CHRNA5, and CHRNA7) are involved in kinase phosphorylation and signal transduction, potentially affecting oral squamous cell carcinoma (OSCC), the most common head and neck cancer (HNC).