Do or Die: HPV E5, E6 and E7 in Cell Death Evasion

Viral oncogenesis in cancer: from mechanisms to therapeutics

The year 2024 marks the 60th anniversary of the discovery of the Epstein-Barr virus (EBV), the first virus confirmed to cause human cancer. Viral infections significantly contribute to the global cancer burden, with seven known Group 1 oncogenic viruses, including hepatitis B virus (HBV), human papillomavirus (HPV), EBV, Kaposi sarcoma-associated herpesvirus (KSHV), hepatitis C virus (HCV), human T-cell leukemia virus type 1 (HTLV-1), and human immunodeficiency virus (HIV). These oncogenic viruses induce cellular transformation and cancer development by altering various biological processes within host cells, particularly under immunosuppression or co-carcinogenic exposures. These viruses are primarily associated with hepatocellular carcinoma, gastric cancer, cervical cancer, nasopharyngeal carcinoma, Kaposi sarcoma, lymphoma, and adult T-cell leukemia/lymphoma. Understanding the mechanisms of viral oncogenesis is crucial for identifying and characterizing the early biological processes of virus-related cancers, providing new targets and strategies for treatment or prevention. This review first outlines the global epidemiology of virus-related tumors, milestone events in research, and the process by which oncogenic viruses infect target cells. It then focuses on the molecular mechanisms by which these viruses induce tumors directly or indirectly, including the regulation of oncogenes or tumor suppressor genes, induction of genomic instability, disruption of regular life cycle of cells, immune suppression, chronic inflammation, and inducing angiogenesis. Finally, current therapeutic strategies for virus-related tumors and recent advances in preclinical and clinical research are discussed.

E5 Oncoprotein: A Key Player in Human Papillomavirus-Positive Head and Neck Cancer Pathogenesis and Therapy Resistance

Head and neck cancer (HNC) is the sixth most prevalent type of cancer worldwide and is associated with low five-year survival rates. Alcoholism and smoking are the main risk factors associated with the development of head and neck cancer (HNC). However, Human Papillomavirus (HPV) infection has been reported as a significant risk factor, particularly for the oropharyngeal subset. In these cases, patients with HPV-positive HNC exhibit a better clinical prognosis; however, resistance to chemotherapy has been frequently reported. The carcinogenic activity of HPV is related to the viral oncoproteins E5, E6, and E7. E5 has been associated with immune evasion mechanisms and modulation of the tumor microenvironment, which appears to be linked to the virus's resistance to chemotherapeutic treatments. Here, we review the potential of HPV E5 in targeted therapy for HNC and discuss relevant data regarding the activity of this oncoprotein in head and neck carcinogenesis.

Targeting the interplay between human papillomavirus oncoproteins and hedgehog signaling: assessment of chemopreventive potential of carvacrol in cervical cancer

Cervical carcinoma is the fourth most frequently diagnosed cancer and is a serious cause of increased mortality among females globally. Hedgehog/GLI signaling has now been established to play a pivotal role in imparting tumor recurrence and promoting metastasis in cervical carcinoma. HPV associated oncoproteins particularly E6/E7 concomitantly with altered signaling pathways are key determinants of cervical cancer. Nevertheless, the nexus between HPV oncogenes and Hedgehog/GLI signaling till date remains unclear. In this study, we investigated the anticancer and apoptotic potential of carvacrol against cervical cancer cells in vitro by targeting the plausible nexus between HPV oncoproteins and Hedgehog signaling. The findings from cell proliferation, LDH cytotoxicity, and morphology analysis suggested that carvacrol treatment significantly decreased the number of viable CaSki cells in a concentration and time-related manner. Morphological trademarks of cell death, including fragmentation of CaSki cell nucleus were studied by DAPI/PI and Hoechst33342 staining. The cytotoxicity of carvacrol was mediated through apoptosis, as confirmed by the Annexin V/FITC assay and caspase activation. Cell cycle analysis showed that carvacrol exerted significant impeding effects on the proliferation of CaSki cells via G0/G1 arrest. Intriguingly, carvacrol mediated the downregulation of HPV E6 and E7 oncogenes indicated its plausible role as an anti-HPV agent against HPV16+ CaSki cells. Additionally, carvacrol further restored p53 expression implicating that carvacrol may protect E6 mediated p53 protein degradation in CaSki cells. Thus, carvacrol exhibited strong antiproliferative potential by inducing apoptosis in cervical carcinoma cells via mediating the crosstalk between the downregulation of HPV oncogenes and inhibition of the hedgehog signaling pathway.

Drosophila model of HPV18-Induced pathogenesis reveals a role for E6 oncogene in regulation of NF-κB and Wnt to inhibit apoptosis

Cancers caused by high-risk human papillomavirus (HPV) remain a significant health threat resulting in more than 300,000 deaths, annually. Persistent expression of two HPV oncogenes, E6 and E7, are necessary for cancer development and progression. E6 has several functions contributing to tumorigenesis one of which is blocking programmed cell death, apoptosis. The detailed mechanism of anti-apoptosis function of E6 is not fully understood. Here, using a Drosophila model of HPV18E6 and the human UBE3A-induced pathogenesis, we show that anti-apoptotic function of E6 is conserved in Drosophila. We demonstrate that the Drosophila homologs of human NF-κB transcription factors, Dorsal and Dif are proapoptotic. They induce the expression of Wingless (Wg, the Drosophila homolog of human Wnt), leading to apoptosis. Our results indicate that E6 oncogene inhibits apoptosis by downregulating the expression of Wg, Dorsal, and Dif. Additionally, we find that Dorsal and Dif, not only promote apoptosis but also regulate autophagy and necrosis. Dorsal promotes autophagy while Dif counteracts it, inducing the formation of acidic vacuoles and necrosis. Interestingly, although E6 blocks the proapoptotic function of Dorsal and Dif, it lacks the ability to interfere with their role in apoptosis-independent cell death. Given the high conservation of NF-κB transcription factors our results provide new insight into potential mechanisms mediated by NF-κB to intervene with cell immortalization action of E6 oncoprotein in HPV-infected cells.

An exploration of the natural and acquired immunological mechanisms to high-risk human papillomavirus infection and unmasking immune escape in cervical cancer: A concise synopsis

The most common STD that triggers cervical cancer is the human papillomavirus. More than 20 types of human papillomavirus (HPV) can induce uterine cervical cancer. Almost all women acquire genital HPV infection soon after their first intercourse, with most of them clearing the virus within 3 years. An immune response is necessary to clear. The first responders to HPV infection are the innate immune system elements composed of macrophages, keratinocytes, natural killer cells, and natural killer T-lymphocytic (NKT) cells. Cytotoxic T lymphocytes (CTLs) comprise the second line of defense and kill HPV16-infected cells expressing various peptides derived from their transforming early viral oncoproteins, mainly E2•E6. Even though HPV can manage to trick away our immune systems, first of all, it is important to emphasize that HPV replication does not kill the host cells. It does not replicate viral antigens or cause inflammation. The HPV16 E6 and E7 genes suppress host cell type 1 interferons (IFNs), which are detectable after infection. The patient may have immunological tolerance; hence, there are no costimulatory signals from inflammatory cytokines like IFNs during antigen recognition. Evidence shows that HlA class I generations have been inhibited by HPV16 E5, which could protect this tumor cell from CTL attack. HPV16 E7 is responsible for initiating immunotolerance and increasing regulatory T cells (Treg) to repress immunological regression. Evasion from immune system protection plays a critical role in the outcome of persistent HPV infection and the development of cervical cancer. Vaccination against HPV16 and 18 during adolescence is the most effective method for preventing cervical cancer in women, considering the immunological processes involved.

Serum Antibodies Against the E5 Oncoprotein from Human Papillomavirus Type 16 Are Inversely Associated with the Infection and the Degree of Cervical Lesions

BACKGROUND

The humoral immune response against human papillomavirus (HPV) has been suggested as a source of biomarkers for the early detection of cervical cancer (CC). Therefore, we aimed to characterize the antibody response against HPV16 E5 in the natural history of cervical cancer and to determine its usefulness as a biomarker of HPV-associated cervical lesions.

METHODS

This study was conducted at the Cuautla General Hospital, Morelos, Mexico, with women (18 to 64 years) who agreed to participate. Samples were obtained from 335 women with cervical lesions and 150 women with negative Papanicolaou tests. HPV genotyping was performed by PCR and pyrosequencing, and anti-E5 antibodies were detected by slot blot.

RESULTS

The overall anti-E5 antibodies prevalence in the study was 17.9%, with the higher prevalence observed in the no lesion (NL, 49.4%) group, and with a downward trend according to the degree of the cervical lesion, from cervical intraepithelial neoplasia-1 (CIN1, 32.2%) to CIN2 (11.5%) and CIN3/CC (6.9%). The logistic regression model showed negative associations of anti-E5 antibodies with CIN1 (OR = 0.38), CIN2 (OR = 0.42), and CIN3/CC (OR = 0.32) groups, being statistically significant. Contrast analysis showed an inverse relationship between anti-E5 antibodies with HPV DNA and the CIN1 (OR = 0.35), CIN2 (OR = 0.39), and CIN3/CC (OR = 0.31) groups.

CONCLUSIONS

These results suggest that anti-E5 antibodies could be associated with clearance of infection in women without lesions and with CIN1 lesions since an inverse relationship was observed between the presence of HPV DNA and anti-E5 antibodies. In contrast, with progression from CIN2/CIN3 to CC, the relationship was reversed, as the anti-E5 antibodies disappeared, and the frequency of the viral genome increased.

Interplay of miR-542, miR-126, miR-143 and miR-26b with PI3K-Akt is a Diagnostic Signal and Putative Regulatory Target in HPV-Positive Cervical Cancer

Human papillomavirus accounts for 99.7% of all cervical cancer cases worldwide. The viral oncoproteins alter normal cell signaling and gene expression, resulting in loss of cell cycle control and cancer development. Also, microRNAs (miRNAs) have been reported to play a critical role in cervical carcinogenesis. Especially these are not only appropriate targets for therapeutic intervention in cervical cancer but also early diagnostic signals. The given study tries to improve the sparse knowledge on miRNAs and their role in this physiological context. Deregulated miRNAs were identified by analyzing the raw data of the well-founded GSE20592 dataset including 16 tumor/normal pairs of human cervical tissue samples. The dataset was quantified by a conservative strategy based on HTSeq and Salmon, followed by target prediction via TargetScan and miRDB. The comprehensive pathway analysis of all factors was performed using DAVID. The theoretical results were subject of a stringent experimental validation in a well-characterized clinical cohort of 30 tumor/normal pairs of cervical samples. The top 31 miRNAs and their 140 primary target genes were closely intertwined with the PI3K-Akt signaling pathway. MiR-21-3p and miR-1-3p showed a prominent regulatory role while miR-542, miR-126, miR-143, and miR-26b are directly targeting both PI3K and AKT. This study provides insights into the regulation of PI3K-Akt signaling as an important inducer of cervical cancer and identified miR-542, miR-126, miR-143, and miR-26b as promising inhibitors of the PI3K-Akt action.

Molecular aspects of cervical cancer: a pathogenesis update

Cervical cancer (CC) is a significant health problem, especially in low-income countries. Functional studies on the human papillomavirus have generated essential advances in the knowledge of CC. However, many unanswered questions remain. This mini-review discusses the latest results on CC pathogenesis, HPV oncogenesis, and molecular changes identified through next-generation technologies. Interestingly, the percentage of samples with HPV genome integrations correlates with the degree of the cervical lesions, suggesting a role in the development of CC. Also, new functions have been described for the viral oncoproteins E5, E6, and E7, resulting in the acquisition and maintenance of cancer hallmarks, including proliferation, immune response evasion, apoptosis, and genomic instability. Remarkably, E5 oncoprotein affects signaling pathways involved in the expression of interferon-induced genes and EGFR-induced proliferation, while E6 and E7 oncoproteins regulate the DNA damage repair and cell cycle continuity pathways. Furthermore, next-generation technologies provide vast amounts of information, increasing our knowledge of changes in the genome, transcriptome, proteome, metabolome, and epigenome in CC. These studies have identified novel molecular traits associated with disease susceptibility, degree of progression, treatment response, and survival as potential biomarkers and therapeutic targets.

Non-apoptotic cell death programs in cervical cancer with an emphasis on ferroptosis

BACKGROUND

Cervical cancer, a pernicious gynecological malignancy, causes the mortality of hundreds of thousands of females worldwide. Despite a considerable decline in mortality, the surging incidence rate among younger women has raised serious concerns. Immortality is the most important characteristic of tumor cells, hence the carcinogenesis of cervical cancer cells pivotally requires compromising with cell death mechanisms.

METHODS

The current study comprehensively reviewed the mechanisms of non-apoptotic cell death programs to provide possible disease management strategies.

RESULTS

Comprehensive evidence has stated that focusing on necroptosis, pyroptosis, and autophagy for disease management is associated with significant limitations such as insufficient understanding, contradictory functions, dependence on disease stage, and complexity of intracellular pathways. However, ferroptosis represents a predictable role in cervix carcinogenesis, and ferroptosis-related genes demonstrate a remarkable correlation with patient survival and clinical outcomes.

CONCLUSION

Ferroptosis may be an appropriate option for disease management strategies from predicting prognosis to treatment.

The Follow-Up Necessity in Human Papilloma Virus-Positive vs. Human Papilloma Virus-Negative Oral Mucosal Lesions: A Retrospective Study

Human papilloma virus (HPV) is known as the main cause of cervical cancer. Data also indicate its role in head-neck cancer, especially oropharyngeal cancer. The correlation between high-risk HPV and oral cancer is still controversial. HPV-related lesions of the oral cavity are frequent and, in most cases, benign. The primary aim of this study was to establish if there is a different follow-up necessity between HPV-positive compared to HPV-negative oral lesions. The secondary aim was to evaluate the recurrence of HPV-related lesions. All patients who underwent a surgical procedure of oral biopsy between 2018 and 2022, with ulterior histopathological examination and HPV typing, were examined. A total of 230 patients were included: 75 received traumatic fibroma as diagnosis, 131 HPV-related lesions, 9 proliferative verrucous leukoplakia, and 15 leukoplakia. The frequency and period of follow-up varied in relation to HPV positivity and diagnosis. This study confirms what has already been reported by other authors regarding the absence of recommendations of follow-up necessity in patients with oral mucosal lesions. However, the data demonstrate that there was a statistically significant difference in the sample analyzed regarding the follow-up of HPV-positive vs. HPV-negative patients. It also confirms the low recurrence frequency of HPV-related oral lesions.

The effects of HPV oncoproteins on host communication networks: Therapeutic connotations

Human papillomavirus (HPV) infections are a leading cause of viral-induced malignancies worldwide, with a prominent association with cervical and head and neck cancers. The pivotal role of HPV oncoproteins, E5, E6, and E7, in manipulating cellular events, which contribute to viral pathogenesis in various ways, has been extensively documented. This article reviews the influence of HPV oncoproteins on cellular signaling pathways within the host cell, shedding light on the underlying molecular mechanisms. A comprehensive understanding of these molecular alterations is essential for the development of targeted therapies and strategies to combat HPV-induced premalignancies and prevent their progress to cancer. Furthermore, this review underscores the intricate interplay between HPV oncoproteins and some of the most important cellular signaling pathways: Notch, Wnt/β-catenin, MAPK, JAK/STAT, and PI3K AKT/mTOR. The treatment efficacies of the currently available inhibitors on these pathways in an HPV-positive context are also discussed. This review also highlights the importance of continued research to advance our knowledge and enhance therapeutic interventions for HPV-associated diseases.

Comparative Analysis of Alpha and Beta HPV E6 Oncoproteins: Insights into Functional Distinctions and Divergent Mechanisms of Pathogenesis

Human papillomaviruses (HPVs) represent a diverse group of DNA viruses that infect epithelial cells of mucosal and cutaneous tissues, leading to a wide spectrum of clinical outcomes. Among various HPVs, alpha (α) and beta (β) types have garnered significant attention due to their associations with human health. α-HPVs are primarily linked to infections of the mucosa, with high-risk subtypes, such as HPV16 and HPV18, being the major etiological agents of cervical and oropharyngeal cancers. In contrast, β-HPVs are predominantly associated with cutaneous infections and are commonly found on healthy skin. However, certain β-types, notably HPV5 and HPV8, have been implicated in the development of non-melanoma skin cancers in immunocompromised individuals, highlighting their potential role in pathogenicity. In this review, we comprehensively analyze the similarities and differences between α- and β-HPV E6 oncoproteins, one of the major drivers of viral replication and cellular transformation, and how these impact viral fitness and the capacity to induce malignancy. In particular, we compare the mechanisms these oncoproteins use to modulate common cellular processes-apoptosis, DNA damage repair, cell differentiation, and the immune response-further shedding light on their shared and distinct features, which enable them to replicate at divergent locations of the human body and cause different types of cancer.