Site-directed mutagenesis of human papillomavirus 18 promoter elements and tissue-specific expression in cervical carcinoma cells

Insights into expression and localization of HPV16 LCR-associated transcription factors and association with LCR activity in HNSCC

Human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) encompasses a heterogeneous group of malignancies characterized by diverse clinical manifestations. Notably, HPV-positive HNSCC exhibits a more favorable prognosis, particularly when the virus is transcriptionally active. This study aimed to elucidate the role of key transcription factors in activating the HPV long control region (LCR), responsible for its oncogenic potential. Utilizing immunoblotting and immunofluorescence techniques, we analyzed the expression and nuclear localization of LCR-associated transcription factors in HPV-negative and HPV-positive HNSCC cell lines. High expression of JunB and low expression of Fra-1, pSTAT3(S727), SP1, and SOX2 were observed in HPV-positive HNSCC cells. Transcriptomic analysis corroborated these findings, revealing differential expression of transcription factors in HPV-positive lesions. Moreover, the study identified strong correlation of LCR-specific transcription factors with HNSCC patient survival. Evaluation of HPV16 LCR reporter activity further underscored the heterogeneous nature of HNSCC, with some HPV-negative cell lines exhibiting comparable LCR activity to HPV-positive counterparts. These findings elucidate the intricate regulatory mechanisms underlying HPV-associated HNSCC and provide insights into potential prognostic markers and therapeutic targets.

Methylation at 3'LCR of HPV16 can be affected by patient age and disruption of E1 or E2 genes

CpG methylation at early promoter of HPV16 DNA, in the 3' end of the Long Control Region (3'LCR), has been associated to the presence of episomal forms of viral genome and, consequently, intact E1 and E2 ORFs. The DNA methylation would block the access of E2 viral protein to the E2 binding sites at early-promoter. However, is still unclear if methylation at 3'LCR of HPV16 DNA can also vary depending of other tumor characteristics in addition to viral DNA physical state. In this study, we evaluate whether the methylation level at the five CpG located at 3'LCR of HPV16 is associated to patient age and E1 and/or E2 ORFs integrity. DNA pyrosequencing was used to measure the methylation level in 69 invasive cervical cancer samples obtained from biopsies of patients attended at Brazilian National Institute of Cancer (INCA). PCR amplifications were performed to assess disruption status of E1 and E2 genes of HPV16. The methylation average per sample ranged widely, from <1 to 88.00%. Presence of intact E1/E2 genes and patient age were positively associated with average methylation in both bivariate analyses (p=0.003 and p=0.006, respectively), and multivariate analysis (p=0.002 and p=0.021, respectively), adjusted for tumor type (squamous cell carcinomas or adenocarcinomas) and HPV16 lineage. These findings showed that presence of intact E1/E2 open reading frames was associated with high levels of DNA methylation, and older patients showed higher levels of methylation than younger ones independently of viral genome disruption.