APOBEC3A and head and neck squamous cell carcinoma: Although some studies have revealed the carcinogenic role of APOBEC family members APOBEC1, APOBEC3A, APOBEC3G and APOBEC3H in esophageal cancer, breast cancer, liver cancer and head and neck squamous cell carcinoma (Yamanaka et al., 1995; Saraconi et al., 2014; Kim et al., 2020; Liu Q et al., 2020), their function in PAAD is still unclear; additionally, there are very few related studies and specific bioinformatics analysis has not been carried out.