The Efficacy of Therapeutic DNA Vaccines Expressing the Human Papillomavirus E6 and E7 Oncoproteins for Treatment of Cervical Cancer: Systematic Review

Cervical cancer is recognized as a serious public health problem since it remains one of the most common cancers with a high mortality rate among women despite existing preventative, screening, and treatment approaches. Since Human Papillomavirus (HPV) was recognized as the causative agent, the preventative HPV vaccines have made great progress over the last few years. However, people already infected with the virus require an effective treatment that would ensure long-term survival and a cure. Currently, clinical trials investigating HPV therapeutic vaccines show a promising vaccine-induced T-cell mediated immune response, resulting in cervical lesion regression and viral eradication. Among existing vaccine types (live vector, protein-based, nucleic acid-based, etc.), deoxyribonucleic acid (DNA) therapeutic vaccines are the focus of the study, since they are safe, cost-efficient, thermostable, easily produced in high purity and distributed. The aim of this study is to assess and compare existing DNA therapeutic vaccines in phase I and II trials, expressing HPV E6 and E7 oncoproteins for the prospective treatment of cervical cancer based on clinical efficacy, immunogenicity, viral clearance, and side effects. Five different DNA therapeutic vaccines (GX-188E, VGX-3100, pNGVL4a-CRT/E7(detox), pNGVL4a-Sig/E7(detox)/HSP70, MEDI0457) were well-tolerated and clinically effective. Clinical implementation of DNA therapeutic vaccines into treatment regimen as a sole approach or in combination with conservative treatment holds great potential for effective cancer treatment.

Coordinated action of human papillomavirus type 16 E6 and E7 oncoproteins on competitive endogenous RNA (ceRNA) network members in primary human keratinocytes

Background miRNAs and lncRNAs can regulate cellular biological processes both under physiological and pathological conditions including tumour initiation and progression. Interactions between differentially expressed diverse RNA species, as a part of a complex intracellular regulatory network (ceRNA network), may contribute also to the pathogenesis of HPV-associated cancer. The purpose of this study was to investigate the global expression changes of miRNAs, lncRNAs and mRNAs driven by the E6 and E7 oncoproteins of HPV16, and construct a corresponding ceRNA regulatory network of coding and non-coding genes to suggest a regulatory network associated with high-risk HPV16 infections. Furthermore, additional GO and KEGG analyses were performed to understand the consequences of mRNA expression alterations on biological processes. Methods Small and large RNA deep sequencing were performed to detect expression changes of miRNAs, lncRNAs and mRNAs in primary human keratinocytes expressing HPV16 E6, E7 or both oncoproteins. The relationships between lncRNAs, miRNAs and mRNAs were predicted by using StarBase v2.0, DianaTools-LncBase v.2 and miRTarBase. The lncRNA-miRNA-mRNA regulatory network was visualized with Cytoscape v3.4.0. GO and KEEG pathway enrichment analysis was performed using DAVID v6.8. Results We revealed that 85 miRNAs in 21 genomic clusters and 41 lncRNAs were abnormally expressed in HPV E6/E7 expressing cells compared with controls. We constructed a ceRNA network with members of 15 lncRNAs – 43 miRNAs – 358 mRNAs with significantly altered expressions. GO and KEGG functional enrichment analyses identified numerous cancer related genes, furthermore we recognized common miRNAs as key regulatory elements in biological pathways associated with tumorigenesis driven by HPV16. Conclusions The multiple molecular changes driven by E6 and E7 oncoproteins resulting in the malignant transformation of HPV16 host cells occur, at least in part, due to the abnormal alteration in expression and function of non-coding RNA molecules through their intracellular competing network.

The Major Constituent of Green Tea, Epigallocatechin-3-Gallate (EGCG), Inhibits the Growth of HPV18-Infected Keratinocytes by Stimulating Proteasomal Turnover of the E6 and E7 Oncoproteins

Epigallocatechin-3-gallate (EGCG), the primary bioactive polyphenol in green tea, has been shown to inhibit the growth of human papilloma virus (HPV)-transformed keratinocytes. Here, we set out to examine the consequences of EGCG treatment on the growth of HPV18-immortalised foreskin keratinocytes (HFK-HPV18) and an authentic HPV18-positive vulvar intraepithelial neoplasia (VIN) clone, focusing on its ability to influence cell proliferation and differentiation and to impact on viral oncogene expression and virus replication. EGCG treatment was associated with degradation of the E6 and E7 oncoproteins and an upregulation of their associated tumour suppressor genes; consequently, keratinocyte proliferation was inhibited in both monolayer and organotypic raft culture. While EGCG exerted a profound effect on cell proliferation, it had little impact on keratinocyte differentiation. Expression of the late viral protein E4 was suppressed in the presence of EGCG, suggesting that EGCG was able to block productive viral replication in differentiating keratinocytes. Although EGCG did not alter the levels of E6 and E7 mRNA, it enhanced the turnover of the E6 and E7 proteins. The addition of MG132, a proteasome inhibitor, to EGCG-treated keratinocytes led to the accumulation of the E6/E7 proteins, showing that EGCG acts as an anti-viral, targeting the E6 and E7 proteins for proteasome-mediated degradation.

E6 and E7 oncoproteins: Potential targets of cervical cancer

: Cervical cancer (CC) is the fourth leading cancer in women in the age group 15-44 globally. Experimental as well as epidemiological studies identified that type16 and 18 HPV cause 70% of precancerous cervical lesions as well as cervical cancer worldwide by bringing about genetic as well as epigenetic changes in the host genome. The insertion of the HPV genome triggers various defense mechanisms including the silencing of tumor suppressor genes as well as activation of oncogenes associated with cancer metastatic pathway. E6 and E7 are small oncoproteins consisting of 150 and 100 amino acids respectively. These oncoproteins affect the regulation of the host cell cycle by interfering with p53 and pRb. Further these oncoproteins adversely affect the normal functions of the host cell by binding to their signaling proteins. Recent studies demonstrated that E6 and E7 oncoproteins are potential targets for CC. Therefore, this review discusses the role of E6 and E7 oncoproteins in metastasis and drug resistance as well as their regulation, early oncogene mediated signaling pathways. This review also uncovers the recent updates on molecular mechanisms of E6 and E7 mediated phytotherapy, gene therapy, immune therapy, and vaccine strategies as well as diagnosis through precision testing. Therefore, understanding the potential role of E6/E7 in metastasis and drug resistance along with targeted treatment, vaccine, and precision diagnostic strategies could be useful for the prevention and treatment of cervical cancer.

Epitome mapping of E6 and E7 proteins from high-risk oncogenic HPV types 16, 18 and 45

Background It is crucial to reveal entire epitomes of more target homologous proteins and specificity of each mapped B cell epitope (BCE) within them for the development of high-risk (hr-) human papillomavirus (HPV) type-specific diagnostic reagents. Methods Recombinant E6 and -E7 oncoproteins from HPV16/18/45 were immunized mice to prepare Rabbit antisera. Overlapping 16mer/8mer-peptides for two rounds of antigenic peptide and fine BCE motif mapping were expressed as GST188 fusion proteins. Fine BCEs were delineated by Western blot and sequence alignment. Results In this work, we decoded six epitomes of E6 and E7 oncoproteins from three HPV types 16, 18 and 45 that are the most common hr-HPVs in cervical cancer patients worldwide, in which total 35 fine BCEs (8, 6 and 4 for E6; 7, 6 and 4 for E7) were mapped using rabbit antisera to respective recombinant proteins. The specificity of each mapped BCE among 20 defined or possible hr-HPVs was delineated by sequence alignment based on BCE minimal motif. According to similarities of immune responses to E6/E7 existed among rabbit and humans, 7 human-recognizing (HR) BCE motifs in HR-peptides of HPV16/18-E6 and E7 proteins were delimitated by comparing with corresponding rabbit-recognizing BCEs. Also, the unique BCE distribution within three delineated E7 epitomes was confirmed, in which almost mapped BCEs were clustered at the first half of the molecules, suggesting that it may be a common characteristic of hr-HPV E7 proteins. Conclusions The results would form the basis for identifying HR-BCEs and developing serodiagnostic reagents used in HPV-based cervical cancer screening and HPV-positive women managing.

HPV Oncoproteins and the Ubiquitin Proteasome System: A Signature of Malignancy?

Human papillomavirus (HPV) E6 and E7 oncoproteins are critical for development and maintenance of the malignant phenotype in HPV-induced cancers. These two viral oncoproteins interfere with a plethora of cellular pathways, including the regulation of cell cycle and the control of apoptosis, which are critical in maintaining normal cellular functions. E6 and E7 bind directly with certain components of the Ubiquitin Proteasome System (UPS), enabling them to manipulate a number of important cellular pathways. These activities are the means by which HPV establishes an environment supporting the normal viral life cycle, however in some instances they can also lead to the development of malignancy. In this review, we have discussed how E6 and E7 oncoproteins from alpha and beta HPV types interact with the components of the UPS, and how this interplay contributes to the development of cancer.

Synthesis and Evaluation of Anisomelic acid-like Compounds for the Treatment of HPV-Mediated Carcinomas

The vast majority of cervical and 75% of oropharyngeal carcinomas are triggered by infection with a type of high-risk oncogenic human papillomavirus (HPV). It is well-known that E6 and E7 oncoproteins are critical for viral-induced cancer, and hence, they represent valuable targets for therapeutic intervention in HPV-mediated cancers. Our earlier research on the cembranoid, anisomelic acid (AA) showed that, AA has the potential to induce apoptosis in HPV cells by the depletion of E6 and E7 oncoproteins. The present study describes the structure-activity relationship and the evaluation of synthetic AA like compounds, i.e simplified cembranoid-like structures, as HPV inhibitors against some papilloma cell lines. Both from experimental and computational results, we observed that these compounds induced apoptosis by the same E6/E7-based mechanism as AA, but at earlier time points, thus being far more effective than AA. Further, the data indicated that only part of the structure of AA is required for the molecular action. Based on these results, we identified some novel and potential compounds for specific treatment of HPV-associated carcinomas.