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). The gene discussed is CHRNA4; the disease is head and neck cancer.