Human papillomavirus E5 protein, the undercover culprit of tumorigenesis

Human papillomavirus (HPV) is the most common viral infection of the reproductive tract worldwide. It has been well documented that the HPV oncoproteins E6 and E7 play important roles in cancer progression and maintenance. However, the high risk HPV E5 protein is also demonstrated to affect some cellular pathway and signaling in human cell lines. In this letter we argue for the need of further investigation and suggest that the HPV E5 protein should be acknowledged as an oncoprotein of HPV.