PDCD1 and cervical cancer: While studies highlighting the association between E5 oncoprotein of high-risk HPV and PD-1/PD-L1 expression in cervical cancer are scarce, Kim et al. investigated the effects of E5 expression on epidermal growth factor receptor-1 (EGFR1) and vascular endothelial growth factor (VEGF) in cervical cancer cell lines (12), concluding that E5 oncoprotein activates EGFR1 thereby upregulating the expression of VEGF (9).