MAPK1 and head and neck squamous cell carcinoma: In our previous study, we identified a SNP within MAPK1/ERK2 that was potentially associated with pre-treatment pain in head and neck cancer patients29 through a comprehensive literature search and gene network analysis (Ingenuity Pathway Analysis [IPA], Ingenuity® Systems, www.ingenuity.com), as well as a genetic association analysis between the common SNPs within the IPA-derived genes and cancer pain in HNSCC patients.