APOBEC3B and head and neck squamous cell carcinoma: Several studies have found that E6 can directly participate in the transcriptional upregulation of APOBEC3B [10, 13] and contribute to APOBEC3B mutation signature, which is widely found in a variety of tumors, including cervical cancer, head and neck squamous cell carcinoma, bladder cancer, and lung cancer [8, 14].