Transcription Factor Homeobox D9 Drives the Malignant Phenotype of HPV18-Positive Cervical Cancer Cells via Binding to the Viral Early Promoter

Abstract

Persistent infections with two types of human papillomaviruses (HPV), HPV16 and HPV18, are the most common cause of cervical cancer (CC). Two viral early genes, E6 and E7, are associated with tumor development, and expressions of E6 and E7 are primarily regulated by a single viral promoter: P97 in HPV16 and P105 in HPV18. We previously demonstrated that the homeobox D9 (HOXD9) transcription factor is responsible for the malignancy of HPV16-positive CC cell lines via binding to the P97 promoter. Here, we investigated whether HOXD9 is also involved in the regulation of the P105 promoter using two HPV18-positive CC cell lines, SKG-I and HeLa. Following the HOXD9 knockdown, cell viability was significantly reduced, and E6 expression was suppressed and was accompanied by increased protein levels of P53, while mRNA levels of TP53 did not change. E7 expression was also downregulated and, while mRNA levels of RB1 and E2F were unchanged, mRNA levels of E2F-target genes, MCM2 and PCNA, were decreased, which indicates that the HOXD9 knockdown downregulates E7 expression, thus leading to an inactivation of E2F and the cell-cycle arrest. Chromatin immunoprecipitation and promoter reporter assays confirmed that HOXD9 is directly associated with the P105 promoter. Collectively, our results reveal that HOXD9 drives the HPV18 early promoter activity to promote proliferation and immortalization of the CC cells.

Integrated computational analysis reveals HOX genes cluster as oncogenic drivers in head and neck squamous cell carcinoma

“…Various genetic alterations have been found unique to HPV-positive oral squamous cell carcinoma (OSCC), including distinctive mutational signatures, overall mutational burden, frequent copy number changes, and candidate driver events 59 . The abnormal expression of HOX genes has been positively correlated with HPV infection in HPV-associated cancer types such as cervical squamous cell carcinoma (CESC) and HNSCC 48 , 60 , 61 . With regards to the HPV-associated HNSCC, HOXB13, HOXC5, HOXC6, HOXC9, and HOXD11 were differentially expressed between HPV-positive and HPV-negative HNSCC ( p < 0.05, Supplementary Table S5 ).…”

Homeobox D9 drives the malignant phenotypes and enhances the Programmed death ligand-1 expression in non-small cell lung cancer cells via binding to Angiopoietin-2 promoter

“…Dysregulation of G1 cell cycle progression leads to tumor cell proliferation [33]. A previous study indicated that knockdown of HOXD9 increased the number of cells at the G1 phase by downregulating expression of the G1 checkpoint-related genes [14]. Furthermore, HOXD9 inhibition could enhance the expression of p53 [9], a key player in the cell cycle for repairing DNA damage [34].…”

“…Clinically, elevated levels of HOXD9 have been detected in various cancers, such as glioblastomas [8], cervical cancer [9], colorectal carcinoma [10], gastric cancer [11], hepatocellular carcinoma [12], and esophageal squamous cell carcinomas [13]. Deletion of HOXD9 could inhibit tumor cell proliferation and cause cell cycle G1 arrest, as well as weaken tumor-forming capacity [10][11][12]14]. Moreover, HOXD9 silencing induced apoptosis of tumor cells by activating the p53 pathway [9].…”

Special Issue: “Management of Early Stage Cervical Cancer”

“…From 2000, different studies showed that HOXD9 regulates the early promoter of HPV16. Hayashi et al confirmed its role even in the regulation of HPV18, implementing the results in the research of a target therapy especially for the worse prognoses HPV-related histotypes [ 22 ].…”