SFRP4 and head and neck squamous cell carcinoma: A naturally occurring Fzd/Wnt antagonist, sFRP4, has demonstrated an increase in the sensitivity of HNSCC CSC to cisplatin through inhibition of canonical Wnt signaling pathway, whereby combinative treatment of sFRP4 and cisplatin showed a significant reduction in CSC viability to 25% lesser than treatment with cisplatin alone.