E2F Transcription Factor 1 Activates FKBP Prolyl Isomerase 4 to Promote Angiogenesis in Cervical Squamous Cell Carcinoma Via the PI3K/AKT Signaling Pathway

Angiogenesis, namely the formation of blood vessels, is crucial for tumor growth, metastasis and development. E2F transcription factor 1 (E2F1) has been linked to tumorigenesis in several human cancers. This work examines the role of E2F1 and its downstream targets in angiogenesis in cervical squamous cell carcinoma (CSCC). E2F1 was predicted as a candidate oncogene in CSCC using a GSE63514 dataset. Increased E2F1 expression was detected in CSCC tumor samples and cell lines by RT-qPCR, immunohistochemistry, and western blot assays. E2F1 downregulation reduced the angiogenesis activity of HUVECs and the invasiveness of CSCC cells. In vivo, E2F1 knockdown also reduced the xenograft tumor growth and promoted tumor necrosis in mice. FKBP prolyl isomerase 4 (FKBP4) was identified as a target of E2F1. E2F1 bound to FKBP4 promoter for transcriptional activation. Further upregulation of FKBP4 blocked the tumor-suppressive role of E2F1 silencing. FKBP4 was enriched in the PI3K/Akt signaling. In cells and xenograft tumors, the E2F1/FKBP4 axis promoted PI3K and Akt phosphorylation. Activation of the PI3K/Akt signaling restored the angiogenesis activity in cells blocked by E2F1 silencing. In summary, this work demonstrates that E2F1 promotes FKBP4 transcription to activate the PI3K/Akt pathway, which augments the angiogenesis and invasiveness of CSCC.