Loss of E2F1 Extends Survival and Accelerates Oral Tumor Growth in HPV-Positive Mice

Role of E2F transcription factor in Oral cancer: Recent Insight and Advancements

The family of mammalian E2F transcription factors (E2Fs) comprise of 8 members (E2F1-E2F8) classified as activators (E2F1-E2F3) and repressors (E2F4-E2F8) primarily regulating the expression of several genes related to cell proliferation, apoptosis and differentiation, mainly in a cell cycle-dependent manner. E2F activity is frequently controlled via the retinoblastoma protein (pRb), cyclins, p53 and the ubiquitin-proteasome pathway. Additionally, genetic or epigenetic changes result in the deregulation of E2F family genes expression altering S phase entry and apoptosis, an important hallmark for the onset and development of cancer. Although studies reveal E2Fs to be involved in several human malignancies, the mechanisms underlying the role of E2Fs in oral cancer lies nascent and needs further investigations. This review focuses on the role of E2Fs in oral cancer and the etiological factors regulating E2Fs activity, which in turn transcriptionally control the expression of their target genes, thus contributing to cell proliferation, metastasis, and drug/therapy resistance. Further, we will discuss therapeutic strategies for E2Fs, which may prevent oral tumor growth, metastasis, and drug resistance.

FNDC3B and BPGM Are Involved in Human Papillomavirus-Mediated Carcinogenesis of Cervical Cancer

Human papillomavirus (HPV)-mediated cervical carcinogenesis is a multistep progressing from persistent infection, precancerous lesion to cervical cancer (CCa). Although molecular alterations driven by viral oncoproteins are necessary in cervical carcinogenesis, the key regulators behind the multistep process remain not well understood. It is pivotal to identify the key genes involved in the process for early diagnosis and treatment of this disease. Here we analyzed the mRNA expression profiles in cervical samples including normal, cervical intraepithelial neoplasia (CIN), and CCa. A co-expression network was constructed using weighted gene co-expression network analysis (WGCNA) to reveal the crucial modules in the dynamic process from HPV infection to CCa development. Furthermore, the differentially expressed genes (DEGs) that could distinguish all stages of progression of CCa were screened. The key genes involved in HPV-CCa were identified. It was found that the genes involved in DNA replication/repair and cell cycle were upregulated in CIN compared with normal control, and sustained in CCa, accompanied by substantial metabolic shifts. We found that upregulated fibronectin type III domain-containing 3B (FNDC3B) and downregulated bisphosphoglycerate mutase (BPGM) could differentiate all stages of CCa progression. In patients with CCa, a higher expression of FNDC3B or lower expression of BPGM was closely correlated with a shorter overall survival (OS) and disease-free survival (DFS). A receiver operating characteristic (ROC) analysis of CIN and CCa showed that FNDC3B had the highest sensitivity and specificity for predicting CCa development. Taken together, the current data showed that FNDC3B and BPGM were key genes involved in HPV-mediated transformation from normal epithelium to precancerous lesions and CCa.

HPV shapes tumor transcriptome by globally modifying the pool of RNA binding protein-binding motif

Human papillomavirus (HPV) positive head and neck cancer displayed specific transcription landscape but the underlying molecular mechanisms are not fully determined. Here, we interestingly found that HPV infection could globally elongate the 3’-untranslated regions (3’UTRs) in the majority of alternative polyadenylation (APA)-containing genes. Counterintuitively, the 3’UTR elongation does not affect their resident gene expression. Rather, they significantly increase the number of binding sites for RNA-binding proteins (RBPs) and subsequently upregulate a group of oncogenic genes by absorbing RBPs. A significant fraction of HPV affected genes are regulated through such mechanism that is 3’UTR-mediated recruitment of RBPs. As an example, we observed that HPV infection increases the length of 3’UTR of RBM25 transcript and hence recruits much more RNA binding protein including FUS and DGCR8. Consequently, in the absence of FUS and DGCR8 regulation, PD-1 was rescued and up-regulated after HPV infection. Taken together, our findings not only suggest a novel paradigm of how oncogenic viruses shape tumor transcriptome by modifying the 3’UTR, but also present a previously unrecognized layer of APA—RBP interplay in this molecular hierarchy. Modification of the pool of RBP-binding motif might expand our understandings into virus-associated carcinogenesis.

Profiling of tRNA Halves and YRNA Fragments in Serum and Tissue From Oral Squamous Cell Carcinoma Patients Identify Key Role of 5' tRNA-Val-CAC-2-1 Half

Oral squamous cell carcinoma (OSCC) is the most common type of head and neck cancer and, as indicated by The Oral Cancer Foundation, kills at an alarming rate of roughly one person per hour. With this study, we aimed at better understanding disease mechanisms and identifying minimally invasive disease biomarkers by profiling novel small non-coding RNAs (specifically, tRNA halves and YRNA fragments) in both serum and tumor tissue from humans. Small RNA-Sequencing identified multiple 5' tRNA halves and 5' YRNA fragments that displayed significant differential expression levels in circulation and/or tumor tissue, as compared to control counterparts. In addition, by implementing a modification of weighted gene coexpression network analysis, we identified an upregulated genetic module comprised of 5' tRNA halves and miRNAs (miRNAs were described in previous study using the same samples) with significant association with the cancer trait. By consequently implementing miRNA-overtargeting network analysis, the biological function of the module (and by "guilt by association," the function of the 5' tRNA-Val-CAC-2-1 half) was found to involve the transcriptional targeting of specific genes involved in the negative regulation of the G1/S transition of the mitotic cell cycle. These findings suggest that 5' tRNA-Val-CAC-2-1 half (reduced in serum of OSCC patients and elevated in the tumor tissue) could potentially serve as an OSCC circulating biomarker and/or target for novel anticancer therapies. To our knowledge, this is the first time that the specific molecular function of a 5'-tRNA half is specifically pinpointed in OSCC.

The Modifying Effect of a Functional Variant at the miRNA Binding Site in E2F1 Gene on Recurrence of Oropharyngeal Cancer Patients with Definitive Radiotherapy

Human papillomavirus (HPV) activates E2F1-driven transcription via the E7-RB-E2F1 pathway. A polymorphism in the 3' UTR of E2F1 gene may disrupt a binding site for miRNA and may affect its transcription level, thus modifying the susceptibility to radiotherapy and outcomes through this pathway. We evaluated the association of a polymorphism at the 3'UTR miRNA binding site of E2F1 gene (rs3213180) with risk of recurrence of SCCOP in a cohort of 1008 patients. Log-rank test and univariate and multivariable Cox models were used to evaluate the associations. Compared with patients with E2F1-rs3213180 GG homozygous genotype, the patients with E2F1-rs3213180GC+CC variant genotypes had significantly better disease-free survival (log-rank P<.001) and decreased risk of SCCOP recurrence (HR, 0.4, 95% CI, 0.3-0.5) after multivariable adjustment. Furthermore, among patients with HPV16-positive tumors, the patients with E2F1-rs3213180 GC+CC variant genotypes had significantly better disease-free survival rates (log-rank P<.001) and lower recurrence risk than those with E2F1-rs3213180 GG homozygous genotype (HR, 0.2, 95% CI, 0.1-0.4). Our findings suggest that E2F1-rs3213180 polymorphism may modulate the risk of recurrence in SCCOP patients, particularly for patients with HPV16-positive tumors of SCCOP. However, future larger population and functional studies are warranted to validate these results.

A functional variant at the miRNA binding site in E2F1 gene is associated with risk and tumor HPV16 status of oropharynx squamous cell carcinoma

Human papillomavirus (HPV) activates E2F1-driven transcription via the E7-RB1-E2F pathway. Genetic polymorphisms in the 3' untranslated region (UTR) targeted by miRNAs can affect the regulation of target genes and individual cancer risk. Thus, we hypothesized that a polymorphism at the 3'UTR miRNA binding site of E2F1 gene (rs3213180) was associated with risk of oral squamous cell carcinoma (OSCC) and tumor HPV status of oropharynx squamous cell carcinoma (OPSCC). We determined the E2F1rs3213180 polymorphism and HPV16 L1 serology of 325 OSCC patients and 335 controls, and tumor HPV16 status of 552 OPSCC. Logistic regression models were used to calculate associations of E2F1rs3213180 polymorphism with risk of HPV-associated OSCC and tumor HPV status of OPSCC. The risk of HPV-associated OSCC was modified by the E2F1rs3213180 polymorphism. Patients with both HPV seropositivity and the Ins/Del or Ins/Ins genotype of E2F1rs3213180 had the highest risk of OSCC, while the lowest risk was detected in patients with HPV seronegativity and the Del/Del genotype. A similar and more prominent effect was detected in OPSCC, but not in oral cavity squamous cell carcinoma (OCSCC) patients. Notably, that effect trend was pronounced in never-smokers and never-drinkers. Furthermore, the patients with the E2F1rs3213180 Ins/Del or Ins/Ins genotype were 2.9 times more likely to have HPV-positive tumors than those with the Del/Del genotype. Our results suggest that the E2F1rs3213180 polymorphism may influence susceptibility to HPV-associated OSCC, particularly for OPSCC, never-smokers and never-drinkers, but not for patients with OCSCC. Additional larger population and functional studies are warranted to confirm our findings. © 2016 Wiley Periodicals, Inc.