Human papillomavirus oncoproteins and apoptosis (Review)

Novel equid papillomavirus from domestic donkey

BACKGROUND

Papillomaviruses can be of great medical importance as they infect humans and animals such as Equus species, other livestock and pets. They are responsible for several papillomas and benign tumours in their host.

OBJECTIVES

To describe a novel equid papillomavirus detected in oral swab samples collected from donkeys (Equus asinus) found on the Northwest plateau of China.

STUDY DESIGN

Cross-sectional.

METHODS

Swab samples collected from the oral mucosa of 32 donkeys in the Gansu Province of China, were subjected to viral metagenomic analysis to detect the presence of Papillomavirus. After de novo assembly, a novel papillomavirus genome designated as Equus asinus papillomavirus 3 (EaPV3) was identified in the studied samples. Additional bioinformatic analysis of the assembled genome was done using the Geneious prime software (version 2022.0.2).

RESULTS

The complete circular genome of EaPV3 is 7430 bp in length with a GC content of 50.8%. The genome was predicted to contain five ORFs coding for three early proteins (E7, E1, and E2) and two late proteins (L1 and L2). Phylogenic analysis of the nucleotide sequences of the concatenated amino acid sequences of the E1E2L1L2 genes revealed that EaPV3 is most closely related to Equus asinus papillomavirus 1 (EaPV1). The genome analysis of EaPV3 revealed similar genome organisation with other equine papillomavirus and the presence of E7 papillomavirus oncoprotein.

MAIN LIMITATIONS

Since there were no warts in the oral cavity of the donkeys in this study, and no biopsy samples taken, we are unable to conclusively link the novel virus to any clinical condition in the donkeys.

CONCLUSIONS

The Comparative characterisation of EaPV3 and its closest relatives, as well as phylogenetic analysis demonstrated that it is a novel virus specie that clusters within the Dyochipapilloma PV genus.

Possibilities of skin coat color-dependent risks and risk factors of squamous cell carcinoma and deafness of domestic cats inferred via RNA-seq data

The transcriptome data of skin cells from domestic cats with brown, orange, and white coats were analyzed using a public database to investigate the possible relationship between coat color-related gene expression and squamous cell carcinoma risk, as well as the mechanism of deafness in white cats. We found that the ratio of the expression level of genes suppressing squamous cell carcinoma to that of genes promoting squamous cell carcinoma might be considerably lower than the theoretical estimation in skin cells with orange and white coats in white-spotted cat. We also found the possibility of the frequent production of KIT lacking the first exon (d1KIT) in skin cells with white coats, and d1KIT production exhibited a substantial negative correlation with the expression of SOX10, which is essential for melanocyte formation and adjustment of hearing function. Additionally, the production of d1KIT was expected to be due to the insulating activity of the feline endogenous retrovirus 1 (FERV1) LTR in the first intron of KIT by its CTCF binding sequence repeat. These results contribute to basic veterinary research to understand the relationship between cat skin coat and disease risk, as well as the underlying mechanism.

HPV16E1 downregulation altered the cell characteristics involved in cervical cancer development

The primary causes of cervical cancer are human papillomavirus type 16 (HPV16) and/or other high-risk (Hr -) HPV infections. Hr-HPVE5, E6, and E7 have been identified as oncoproteins that play roles in the development of cancer. However, other HPV proteins, especially E1, may also be involved in cancer development. In this study, the role of HPV16E1 in cervical carcinogenesis was examined by siRNA knockdown experiments using SiHa cells as a model. The results showed that HPV16E1 regulated P-FOXO3a and HPV16E7 expression. Various cell functions associated with the hallmarks of cancer, including cell viability, colony formation, invasion, and anchorage-independent cell growth, were altered when HPV16E1 was downregulated. However, no effect on cell migration and apoptosis properties was found. Moreover, HPV16E1 downregulation resulted in an increase in cisplatin susceptibility. In conclusion, this is the first demonstration that HPV16E1 might be regarded as a possible novel oncoprotein involved in several processes related to oncogenesis.

Ferroptosis: Mechanism and potential applications in cervical cancer

Ferroptosis is a distinct form of cell death mechanism different from the traditional ones. Ferroptosis is characterized biochemically by lipid peroxidation, iron accumulation, and glutathione deficiency. It has already demonstrated significant promise in antitumor therapy. Cervical cancer (CC) progression is closely linked to iron regulation and oxidative stress. Existing research has investigated the role of ferroptosis in CC. Ferroptosis could open up a new avenue of research for treating CC. This review will describe the factors and pathways and the research basis of ferroptosis, which is closely related to CC. Furthermore, the review may provide potential future directions for CC research, and we believe that more studies concerning the therapeutic implications of ferroptosis in CC will come to notice.

A novel multi-epitope vaccine of HPV16 E5E6E7 oncoprotein delivered by HBc VLPs induced efficient prophylactic and therapeutic antitumor immunity in tumor mice model

Human papilloma virus type 16 (HPV16) is the most prevalent etiologic agent associated with cervical cancer, and its early proteins E5, E6 and E7 play important roles in cervical epithelium transformation to cervical intraepithelial neoplasia and even cervical cancer. Hence, these oncoproteins are ideal target antigens for developing immunotherapeutic vaccines against HPV-associated infection and cervical cancer. Currently, multi-epitope vaccines have been a promising strategy for immunotherapy for viral infection or cancers. In this study, the E5aa28-46, E6aa37-57 and E7aa26-57 peptides were selected and linked to form a novel multi-epitopes vaccine (E765m), which was inserted into the major immune dominant region (MIR) of hepatitis B virus core antigen (HBc) to construct a HBc-E765m chimeric virus-like particles (cVLPs). The immunogenicity and immunotherapeutic effect of the cVLPs vaccine was evaluated in immunized mice and a tumor-bearing mouse model. The results showed that HBc-E765m cVLPs elicited high E5-, E6- and E7- specific CTL and serum IgG antibody responses, and also relatively high levels of the cytokines IFN-γ, IL-4 and IL-5. More importantly, the cVLPs vaccine significant suppressed tumor growth in mice bearing E5-TC-1 tumors. Our findings provide strong evidence that this novel HBc-E765m cVLPs vaccine could be a candidate vaccine for specific immunotherapy in HPV16-associated cervical intraepithelial neoplasia or cervical cancer.

Molecular Mechanisms of HIV Protease Inhibitors Against HPV-Associated Cervical Cancer: Restoration of TP53 Tumour Suppressor Activities

Cervical cancer is a Human Papilloma virus-related disease, which is on the rise in a number of countries, globally. Two essential oncogenes, E6 and E7, drive cell transformation and cancer development. These two oncoproteins target two of the most important tumour suppressors, p53 and pRB, for degradation through the ubiquitin ligase pathway, thus, blocking apoptosis activation and deregulation of cell cycle. This pathway can be exploited for anticancer therapeutic interventions, and Human Immunodeficiency Virus Protease Inhibitors (HIV-PIs) have attracted a lot of attention for this anticancer drug development. HIV-PIs have proven effective in treating HPV-positive cervical cancers and shown to restore impaired or deregulated p53 in HPV-associated cervical cancers by inhibiting the 26S proteasome. This review will evaluate the role players, such as HPV oncoproteins involved cervical cancer development and how they are targeted in HIV protease inhibitors-induced p53 restoration in cervical cancer. This review also covers the therapeutic potential of HIV protease inhibitors and molecular mechanisms behind the HIV protease inhibitors-induced p53-dependent anticancer activities against cervical cancer.

HPV-induced cancers: preclinical therapeutic advancements

INTRODUCTION

High-risk HPV infections are related to several epithelial cancers. Despite the availability of prophylactic vaccines, HPV infections are still responsible for about 5% of all human malignancies worldwide. While therapeutic vaccines are ongoing clinical trials, genotoxic agents and surgical interventions represent current clinical treatments, with no specific anti-HPV drugs yet available in the clinics.

AREAS COVERED

We offer a comprehensive report of small molecules in preclinical studies proposed as potential anticancer agents against HPV-driven tumors. Given the importance of HPV oncoproteins for cancer maintenance, particularly E6 and E7, we present a classification of both non-targeted and targeted agents, with a further subdivision of the latter into two categories according to their either direct or indirect activity against viral protein functions.

EXPERT OPINION

Prophylactic vaccines can prevent the insurgence of HPV-related cancers, but have no effect against pre-existing infections. Moreover, their high cost, genotype-restricted effect and the growing worldwide distrust for vaccines make the availability of a specific drug an unmet medical need. Different viral early proteins emerge as ideal candidates for drug development. We highlight the most promising strategies and address future challenges in this field to herald the prospect of a specific therapeutic regimen against HPV-related cancers.

Lipid metabolism and oxidative stress in HPV-related cancers

High-risk human papillomavirus (HR-HPVs) are associated with the development of cervical, anus, vagina, vulva, penis, and oropharynx cancer. HR-HPVs target and modify the function of different cell biomolecules such as glucose, amino acids, lipids, among others. The latter induce cell proliferation, cell death evasion, and genomic instability resulting in cell transformation. Moreover, lipids are essential biomolecules in HR-HPVs infection and cell vesicular trafficking. They are also critical in producing cellular energy, the epithelial-mesenchymal transition (EMT) process, and therapy resistance of HPV-related cancers. HPV proteins induce oxidative stress (OS), which in turn promotes lipid peroxidation and cell damage, resulting in cell death such as apoptosis, autophagy, and ferroptosis. HR-HPV-related cancer cells cope with OS and lipid peroxidation, preventing cell death; however, these cells are sensitized by OS, which could be used as a target for redox therapies to induce their elimination. This review focuses on the role of lipids in HR-HPV infection and HPV-related cancer development, maintenance, resistance to therapy, and the possible treatments associated with lipids. Furthermore, we emphasize the significant role of OS in lipid peroxidation to induce cell death through apoptosis, autophagy, and ferroptosis to eliminate HPV-related cancers.

Proteomics Analysis of Andrographolide-Induced Apoptosis via the Regulation of Tumor Suppressor p53 Proteolysis in Cervical Cancer-Derived Human Papillomavirus 16-Positive Cell Lines

Regardless of the prophylactic vaccine accessibility, persistent infections of high-risk human papillomaviruses (hr-HPVs), recognized as an etiology of cervical cancers, continues to represent a major health problem for the world population. An overexpression of viral early protein 6 (E6) is linked to carcinogenesis. E6 induces anti-apoptosis by degrading tumor suppressor proteins p53 (p53) via E6-E6-associated protein (E6AP)-mediated polyubiquitination. Thus, the restoration of apoptosis by interfering with the E6 function has been proposed as a selective medicinal strategy. This study aimed to determine the activities of andrographolide (Androg) on the disturbance of E6-mediated p53 degradation in cervical cancer cell lines using a proteomic approach. These results demonstrated that Androg could restore the intracellular p53 level, leading to apoptosis-induced cell death in HPV16-positive cervical cancer cell lines, SiHa and CaSki. Mechanistically, the anti-tumor activity of Androg essentially relied on the reduction in host cell proteins, which are associated with ubiquitin-mediated proteolysis pathways, particularly HERC4 and SMURF2. They are gradually suppressed in Androg-treated HPV16-positive cervical cancer cells. Collectively, the restoration of p53 in HPV16-positive cervical cancer cells might be achieved by disruption of E3 ubiquitin ligase activity by Androg, which could be an alternative treatment for HPV-associated epithelial lesions.

Viral Manipulation of the Host Epigenome as a Driver of Virus-Induced Oncogenesis

Tumorigenesis due to viral infection accounts for a high fraction of the total global cancer burden (15–20%) of all human cancers. A comprehensive understanding of the mechanisms by which viral infection leads to tumor development is extremely important. One of the main mechanisms by which viruses induce host cell proliferation programs is through controlling the host’s epigenetic machinery. In this review, we dissect the epigenetic pathways through which oncogenic viruses can integrate their genome into host cell chromosomes and lead to tumor progression. In addition, we highlight the potential use of drugs based on histone modifiers in reducing the global impact of cancer development due to viral infection.

Whole Genomic Analysis and Comparison of Two Canine Papillomavirus Type 9 Strains in Malignant and Benign Skin Lesions

Papillomaviruses (PVs) usually cause benign proliferative lesions in the stratified epithelium of various animal species. However, some high-risk types of PVs have been proven to lead to malignant transformations. In dogs, several canine papillomaviruses (CPVs) have been identified in malignant lesions and are suggested as one of the risk factors for the development of squamous cell carcinomas (SCCs). In the present study, the full genomes of two CPV9 strains from recurrent SCCs of Dog 1 and skin viral papilloma (viral plaque) of Dog 2 were sequenced. Alignment of the two CPV9 sequences with the genome of the reference CPV9 strain (accession no. JF800656.1) derived from a solitary pigmented plaque was performed. Compared with the reference strain, a 27 bp in-frame insertion in the E1 gene was identified in both CPV9 strains in this study. In comparison with the CPV9 strains derived from benign lesions, the CPV9 from the SCCs of Dog 1 exhibited a 328 bp deletion at the 3′ end of the E2 and spacer sequence, which encoded a truncated deduced E2 protein and a chimeric E8^E2 protein. However, there was no difference in the mRNA expression levels of viral oncoproteins of E6 and E7 between the two CPV9 cases, suggesting that the oncogenesis of CPV9 for malignant transformation might be different from that of human papillomaviruses. The roles of E2 and E8^E2 deleted CPV9 in the oncogenesis of benign and malignant lesions should be further investigated.

Human Papillomaviruses and Epstein-Barr Virus Interactions in Colorectal Cancer: A Brief Review

Human papillomaviruses (HPVs) and the Epstein-Barr virus (EBV) are the most common oncoviruses, contributing to approximately 10%-15% of all malignancies. Oncoproteins of high-risk HPVs (E5 and E6/E7), as well as EBV (LMP1, LMP2A and EBNA1), play a principal role in the onset and progression of several human carcinomas, including head and neck, cervical and colorectal. Oncoproteins of high-risk HPVs and EBV can cooperate to initiate and/or enhance epithelial-mesenchymal transition (EMT) events, which represents one of the hallmarks of cancer progression and metastasis. Although the role of these oncoviruses in several cancers is well established, their role in the pathogenesis of colorectal cancer is still nascent. This review presents an overview of the most recent advances related to the presence and role of high-risk HPVs and EBV in colorectal cancer, with an emphasis on their cooperation in colorectal carcinogenesis.

Phenotype-based discovery of a HeLa-specific cytotoxic molecule that downregulates HPV-mediated signaling pathways via oxidative damage

Selective bioactive compounds have emerged as major players in chemical biology for their potential in disrupting diverse biological pathways with minimal adverse effects. Using phenotypic screening, we identified an anti-cancer agent, SB2001, with a highly specific cytotoxicity toward HeLa human cervical cancer cells. The subsequent mechanistic study revealed that SB2001 induced apoptotic cell death through restoring p53 function and suppressed the human papillomavirus (HPV)-mediated oncoprotein signaling pathway via oxidative damage in HeLa cells. SB2001 also selectively induced HeLa-specific tumor regression without any adverse effects in an in vivo tumor xenograft model, demonstrating its potential as a promising chemical probe.

Novel Approaches for Vaccination Against HPV-Induced Cancers

To date, more than 5 % of all cancers are as a result of human papillomavirus (HPV) infection, and this incidence is increasing. Early recognition of disease is associated with good survival, but late presentation results in devastating consequences. Prevention is better than cure, and there are now successful prophylactic vaccination programmes in place. We discuss these and the prospect of therapeutic vaccinations in the near future to address a growing need for improved therapeutic options.

Brd4 inhibition suppresses HPV16 E6 expression and enhances chemoresponse: A potential new target in cervical cancer therapy

Although a vast amount of research underlines the roles of the HR HPV E6 and E7 oncogenes in HPV-induced carcinogenesis of cervical cancer, it remains unclear whether these oncogenes are also involved in the resistance of the cancer against chemotherapy. We examined the role of the HPV16 E6 oncogene in cisplatin resistance by analyzing its expression in newly established cisplatin-sensitive versus -resistant cervical cancer cell lines (CC7, CC10). Resistant variants were obtained by interval exposure treatment with 1-2 μM cisplatin for 8-9 months. Our results demonstrate that the expression level of HPV16 E6 directly correlates with the extent of cisplatin resistance in novel as well as established (SiHa) drug resistant cervical cancer cell lines. Overexpression of HPV16 E6 in cisplatin-naïve cells rendered these cells more resistant to cisplatin. Reducing E6 expression by JQ1 treatment reversed the drug resistant phenotype and strongly enhanced chemoresponse only in HPV-positive cisplatin-resistant variants and not in HPV-negative C33A cervical cancer cells. The level of E6 directly correlated with the extent of cisplatin sensitivity and was shown to be increased in newly established drug-resistant cell line variants, while reducing E6 expression using Brd4-inhibitors enhanced chemoresponse when co-delivered with cisplatin. Inhibition of Brd4 could represent a new therapeutic option by increasing treatment response in cervical cancer cells and might allow lower cisplatin dosages, thus reducing negative side effects.

Smokeless tobacco extract inhibits proliferation and promotes apoptosis in oral mucous fibroblasts

The consumption of smokeless tobacco extract (STE) is growing rapidly, and it has been implicated in several human diseases including diabetes, inflammation and a number of types of cancer. The toxicity of STE requires evaluation, as it is known to induce numerous public health issues. To investigate whether STE serves a role in cultured human oral mucosa fibroblasts (hOMFs), the present study examined HOMF morphology with inverted microscopy and immunofluorescence staining. The cell viability was measured with MTT assays, which detected the cell apoptosis rate via flow cytometry. The activities of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were measured via flow cytometry and commercial kits, subsequent to exposing the cells to various concentrations of STE. Reverse transcription quantitative polymerase chain reaction and western blot analyses were used to demonstrate that the mRNA and the protein expression levels of cell cycle-associated genes (cyclin-dependent kinase inhibitor 1 and cyclin D1), apoptosis-associated genes [B cell lymphoma 2 (Bcl-2) and Bcl-2-associatied X protein], tumor protein (p53), nuclear factor kappa light chain enhancer of activated B cells (NF-κB)-transcription factor (p65) signaling pathways, NF-E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H: quinoneoxidoreductase1 (NQO1). The results indicated that the hOMF cells were positive for cytokeratin staining. STE induced G1-S cell cycle progression and cell apoptosis by regulating the cell cycle or apoptosis-associated proteins. STE treatment increased the concentrations of ROS and MDA, and decreased the concentrations of SOD and CAT. STE unregulated phosphorylated-p53, NF-κB p65, Nrf2, HO-1, and NQO1 expression levels in the hOMF cells. The present study demonstrated that STE appears to promote oral disease.

Targeting Head and Neck Cancer by Vaccination

Head and neck cancer (HNC) is a heterogeneous group of squamous cell cancers that affect the oral cavity, pharynx, and larynx. Worldwide, it is the sixth most common cancer but in parts of Southern and South-East Asia, HNC is one of the most common cancers. A significant proportion of HNC is driven by human papillomavirus (HPV) infection, whereas HPV-independent HNC is associated with alcohol, smoking, and smokeless tobacco consumption. Here, we review the past and present experience of targeting HNC with vaccination focusing on HPV-derived antigens as well as non-viral antigens for HPV-negative HNC. Novel therapeutic approaches for HNC will focus not only on effective vaccine platforms but will also target the stroma-rich immunosuppressive microenvironment found in those tumours.

C33-A cells transfected with E6*I or E6*II the short forms of HPV-16 E6, displayed opposite effects on cisplatin-induced apoptosis

The HPV-16 E6/E7 bicistronic immature transcript produces 4 mature RNAs: the unspliced HPV-16 E6/E7^pre-mRNA product and 3 alternatively spliced mRNAs. The 3 spliced mRNAs encode short forms of the E6 oncoprotein, namely E6*I, E6*II and E6^E7. In this study we showed that transfection of C-33A cells with monocistronic constructs of these cDNAs fused to GFP, produced different effects on apoptosis, after the treatment with cisplatin. Transfection of C-33A cells with the full-length E6-GFP oncoprotein resulted in a 50% decrease in cell death, while the transfection with the E6*I-GFP construct showed only a 25% of diminution of cell death, compared to the control cells. Transfection with the E6^E7-GFP or E7-GFP construct had no effect on the number of the apoptotic cells, compared with control cells. Conversely, transfection with the E6*II construct resulted in higher cell death than the control cells. Taken together, these results suggested that E6*I or E6*II, the short forms of HPV-16 E6, displayed opposite effects on cisplatin-induced apoptosis, when transfected in C-33A cells.

Polo-like kinase 3 and phosphoT273 caspase-8 are associated with improved local tumor control and survival in patients with anal carcinoma treated with concomitant chemoradiotherapy

We have recently shown that caspase-8 is a new substrate of Polo-like kinase 3 (Plk3) that phosphorylates the protein on residue T273 thereby promoting its pro-apoptotic function. In the present study we aimed to investigate the clinical relevance of Plk3 expression and phosphorylation of caspase-8 at T273 in patients with anal squamous cell carcinoma (SSC) treated with 5-fluorouracil and mitomycin C-based chemoradiotherapy (CRT). Immunohistochemical detection of the markers was performed in pretreatment biopsy specimens of 95 patients and was correlated with clinical/histopathologic characteristics including HPV-16 virus load/p16^INK4a expression and cumulative incidence of local and distant failure, cancer specific survival (CSS), and overall survival (OS). We observed significant positive correlations between Plk3 expression, pT273 caspase-8 signal, and levels of HPV-16 virus DNA load/p16^INK4a detection. Patients with high scores of Plk3 and pT273 caspase-8 showed increased local control (p = 0.011; p = 0.001), increased CSS (p = 0.011; p = 0.013) and OS (p = 0.024; p = 0.001), while the levels of pT273 caspase-8 were significantly associated (p = 0.033) with distant metastases. In multivariate analyses Plk3 expression remained significant for local failure (p = 0.018), CSS (p = 0.016) and OS (p = 0.023). Moreover, a combined HPV16 DNA load and Plk3 or pT273 caspase-8 variable revealed a significant correlation to decreased local failure (p = 0.001; p = 0.009), increased CSS (p = 0.016; p = 0.023) and OS (p = 0.003; p = 0.003). In conclusion these data indicate that elevated levels of Plk3 and pT273 caspase-8 are correlated with favorable clinical outcome in patients with anal SCC treated with concomitant CRT.

A novel arylbenzofuran induces cervical cancer cell apoptosis and G1/S arrest through ERK-mediated Cdk2/cyclin-A signaling pathway

7-hydroxy-5,4'-dimethoxy-2-arylbenzofuran (Ary) is purified from Livistona. It has been demonstrated to have anticancer activity to various tumors in including cervical cancer, but its mechanism is still unclear. In the present, we show that Ary induces cervical cancer cells apoptosis through mitochondria degradation and mediates cervical cancer cell arrest. Further, Ary-inducing cell cycle G1/S-phase arrest is associated with increased cyclin A2 and cyclin dependent kinase 2 (Cdk2) proteins. Knockdown of cyclin A2 using small interfering RNA (siRNA), and inhibiting Cdk2 activity with flavopiridol, strikingly reduced G1/S-phase arrest. Moreover, Ary sustainedly induced phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2). And ERK1/2 phosphorylation inhibition using specific inhibitor U0126 effectively suppressed cyclin A2 expression, and reduced G1/S-phase arrest induced by Ary. All the experiments in vitro and in vivo verified that Ary has an anticancer effect on cervical cancer. These data provide novel evidences that Ary induces cervical cancer cells apoptosis through mitochondria degradation and cell G1/S-phase arrest. These findings also suggest that ERK-mediated Cdk2/cyclin A signaling pathway is involved in Ary-induced G1/S-phase arrest.

Identification of (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamate-nitrostyrene hybrid as potent antiproliferative and apoptotic inducing agent against cervical cancer cell lines

The present study seeks to describe the design and synthesis of six new Michael adducts of (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamate with nitrostyrenes and their in vitro antiproliferative activity against human cervical cancer cell lines [HeLa (HPV 18 positive), CaSki (HPV 16 positive) and ViBo (HPV negative) cervical cancer cell lines]. Virtual screening of the physicochemical properties of all compounds have also been presented. All the compounds exploited significant antiproliferative activity on the three cervical cancer cell lines. Compound 8a was found to be most potent, displaying in vitro antiproliferative activity against HeLa, CaSki and ViBo cervical cancer cell lines superior to Cisplatin and Paclitaxel with IC₅₀ values 0.99 ± 0.007, 2.36 ± 0.016 and 0.73 ± 0.002 μM respectively. In addition, compound 8a did not trigger the necrosis cell death to the test cancer cell lines. Further mechanistic study revealed that compound 8a could inhibit the cancer cell proliferation by inducing apoptosis through caspase-3 activation. Moreover, cell cycle analysis indicated that compound 8a could arrest the cell cycle at the G1 phase for HeLa and CaSki cancer cells. At the predetermined IC₅₀ values on cancer cells, compound 8a did not induce any necrotic (cytotoxic) death to the normal human lymphocytes. In the present design, (1S,4S)-2,5-diazabicyclo[2.2.1]heptane system was found to be superior than the piperazine counterpart 11.

Negative correlation between X-linked inhibitors of apoptosis and second mitochondria-derived activator of caspase expression levels in cervical carcinoma and cervical intraepithelial neoplasia

X-linked inhibitors of apoptosis (XIAP) and second mitochondria-derived activator of caspase (Smac) have been widely reported to serve roles in the development of cervical carcinoma. The present study analyzed the associations between the expression levels of XIAP and Smac in normal cervical epithelium, cervical intraepithelial neoplasia (CIN) and cervical carcinoma. Immunohistochemistry staining of formalin-fixed, paraffin-embedded tissue sections was performed in order to analyze the expression levels of XIAP and Smac in 15 cases of normal cervical tissues, 69 cases of CIN and 76 cases of cervical carcinoma. All the tissue samples were confirmed by pathological diagnosis. The association of XIAP and Smac expression levels was analyzed using one-way analysis of variance, χ² tests and Spearman's ρ for the nonparametric bi-variant correlation analysis. Overall survival was determined using the log-rank test and Kaplan-Meier survival curves. The expression level of XIAP was increased in CIN and cervical carcinoma tissues compared with normal cervical tissues, whereas Smac demonstrated a converse expression pattern to XIAP in these tissues. The positive staining level of XIAP protein was increased in grade 3 CIN compared with that in grade 1–2 CIN, and was significantly higher in the less-differentiated tissue of cervical carcinoma compared with the well- or medium-differentiated tissues (P<0.05). The staining level was also significantly increased in cervical carcinoma with stage 2b-3 compared with tissues from stage 1–2a carcinoma (P<0.05). The expression levels of Smac were in opposition to these results. XIAP was associated with pelvic lymph node metastasis, whereas no association was identified with Smac expression. The expression level of XIAP was significantly and negatively associated with cell survival time in cervical carcinoma, whereas the expression level of Smac was significantly and positively associated with cell survival time in cervical carcinoma. Therefore, XIAP and Smac may participate in the development of cervical cancer. The expression levels of XIAP and Smac were significantly and inversely associated. This may be useful in early diagnosis, evaluation of surgery and chemotherapy and the prognosis of cervical carcinoma.

Modulation of DNA methylation by human papillomavirus E6 and E7 oncoproteins in cervical cancer

Human papillomaviruses (HPVs) are double stranded circular DNA viruses that infect cutaneous and mucosal epithelial cells. Almost 99% of cervical cancer has a HPV infection. The early oncoproteins E6 and E7 are important in this cellular transformation process. Epigenetic mechanisms have long been known to result in decisive alterations in DNA, leading to alterations in DNA-protein interactions, alterations in chromatin structure and compaction and significant alterations in gene expression. The enzymes responsible for these epigenetic modifications are DNA methyl transferases (DNMTs), histone acetylases and deacetylases. Epigenetics has an important role in cancer development by modifying the cellular micro environment. In this review, the authors discuss the role of HPV oncoproteins E6 and E7 in modulating the epigenetic mechanisms inside the host cell. The oncoproteins induce the expression of DNMTs which lead to aberrant DNA methylations and disruption of the normal epigenetic processes. The E7 oncoprotein may additionally directly bind and induce methyl transferase activity of the enzyme. These modulations lead to altered gene expression levels, particularly the genes involved in apoptosis, cell cycle and cell adhesion. In addition, the present review discusses how epigenetic mechanisms may be targeted for possible therapeutic interventions for HPV mediated cervical cancer.

Immunotherapeutic Effects of Dendritic Cells Pulsed with a Coden-optimized HPV 16 E6 and E7 Fusion Gene in Vivo and in Vitro

BACKGROUND

Cervical cancer is the second most common cause of cancer related death of women. Persistent HPV infection, especially with high-risk types such as HPV16 and HPV18, has been identified to be the primary cause of cervical cancer. E6 and E7 are the major oncoproteins of high-risk HPVs, which are expressed exclusively in HPV infected tissues, and thereby represent ideal therapeutic targets for immunotherapy of cervical cancer.

MATERIALS AND METHODS

In this work, we used recombinant adenovirus expressing coden-optimized HPV16 E6 and E7 fusion protein (Ad-ofE6E7) to prime dendritic cells (DC-ofE6E7), to investigate the ability of primed DC vaccine in eliciting antitumor immunity in vitro and vivo.

RESULTS

Our results indicated that DC-ofE6E7 vaccine co-culturing with splenocytes could strongly induce a tumor-specific cytotoxic T lymphocyte (CTL) response and kill the TC-1 cells effectively in vitro. Moreover, DC-ofE6E7 vaccine induced protective immunity against the challenge of TC-1 cancer cells in vivo.

CONCLUSIONS

The results suggested that the HPV16 ofE6E7 primed DC vaccine has potential application for cervical cancer immunotherapy.

Epigenetic Pathways of Oncogenic Viruses: Therapeutic Promises

Cancerous transformation comprises different events that are both genetic and epigenetic. The ultimate goal for such events is to maintain cell survival and proliferation. This transformation occurs as a consequence of different features such as environmental and genetic factors, as well as some types of infection. Many viral infections are considered to be causative agents of a number of different malignancies. To convert normal cells into cancerous cells, oncogenic viruses must function at the epigenetic level to communicate with their host cells. Oncogenic viruses encode certain epigenetic factors that lead to the immortality and proliferation of infected cells. The epigenetic effectors produced by oncogenic viruses constitute appealing targets to prevent and treat malignant diseases caused by these viruses. In this review, we highlight the importance of epigenetic reprogramming for virus-induced oncogenesis, with special emphasis on viral epigenetic oncoproteins as therapeutic targets. The discovery of molecular components that target epigenetic pathways, especially viral factors, is also discussed.

Genetic susceptibility to cervical cancer: role of common polymorphisms in apoptosis-related genes

Cervical cancer is a common malignancy which poses a significant health burden among women, especially those living in the developing countries. Although human papillomavirus (HPV) infection has been unequivocally implicated in the etiopathogenesis of the cancer, it alone is not adequate to contribute to the malignant transformation of cervical cells. Most HPV infections regress spontaneously, and only a small proportion of women have persistent infections which eventually lead to malignancy. This suggests that interplays between HPV infection and other cofactors certainly exist during the process of cervical carcinogenesis, which synergistically contribute to the differential susceptibility of an individual to the malignancy. Undoubtedly, host genetic factors represent a major element involved in such a synergistic interaction, and accumulating evidence suggests that polymorphisms in apoptosis-related genes play an important role in the genetic susceptibility to cervical cancer. This review consolidates the recent literatures on the role of common polymorphisms in apoptosis-related genes in genetic susceptibility to cervical cancer.

A new arylbenzofuran derivative functions as an anti-tumour agent by inducing DNA damage and inhibiting PARP activity

We previously reported that 7-hydroxy-5, 4'-dimethoxy-2-arylbenzofuran (HDAB) purified from Livistona chinensis is a key active agent. The present study investigated the function and molecular mechanism of HDAB. HDAB treatment of cervical cancer cells resulted in S phase arrest and apoptosis, together with cyclin A2 and CDK2 upregulation. Cyclin A2 siRNA and a CDK inhibitor efficiently relieved S phase arrest but increased the apoptosis rate. Mechanistic studies revealed that HDAB treatment significantly increased DNA strand breaks in an alkaline comet assay and induced ATM, CHK1, CHK2 and H2A.X phosphorylation. Wortmannin (a broad inhibitor of PIKKs) and CGK733 (a specific ATM inhibitor), but not LY294002 (a phosphatidylinositol 3-kinase inhibitor) or NU7026 (a DNA-PK specific inhibitor), prevented H2A.X phosphorylation and γH2A.X-positive foci formation in the nuclei, reversed S phase arrest and promoted the HDAB-induced apoptosis, suggesting that HDAB is a DNA damaging agent that can activate the ATM-dependent DNA repair response, thereby contributing to cell cycle arrest. In addition, molecular docking and in vitro activity assays revealed that HDAB can correctly dock into the hydrophobic pocket of PARP-1 and suppress PARP-1 ADP-ribosylation activity. Thus, the results indicated that HDAB can function as an anti-cancer agent by inducing DNA damage and inhibiting PARP activity.

Human Beta-papillomavirus infection and keratinocyte carcinomas

Although the role of oncogenic human Alpha-papillomaviruses (HPVs) in the development of mucosal carcinomas at different body sites (eg cervix, anus, oropharynx) is fully recognized, a role for HPV in keratinocyte carcinomas (KCs; basal and squamous cell carcinomas) of the skin is not yet clear. KCs are the most common cancers in Caucasians, with the major risk factor being ultraviolet (UV) light exposure. A possible role for Beta-HPV types (BetaPV) in the development of KC was suggested several decades ago, supported by a number of epidemiological studies. Our current review summarizes the recent molecular and histopathological evidence in support of a causal association between BetaPV and the development of KC, and outlines the suspected synergistic effect of viral gene expression with UV radiation and immune suppression. Further insights into the molecular pathways and protein interactions used by BetaPV and the host cell is likely to extend our understanding of the role of BetaPV in KC.

Are human polyomaviruses co-factors for cancers induced by other oncoviruses?

Presently, 12 human polyomaviruses are known: BK polyomavirus (BKPyV), JCPyV, KIPyV, WUPyV, Merkel cell polyomavirus (MCPyV), HPyV6, HPyV7, Trichodysplasia spinulosa-associated polyomavirus, HPyV9, HPyV10, STLPyV and HPyV12. In addition, the non-human primate polyomavirus simian virus 40 (SV40) seems to circulate in the human population. MCPyV was first described in 2008 and is now accepted to be an etiological factor in about 80% of the rare but aggressive skin cancer Merkel cell carcinoma. SV40, BKPyV and JCPyV or part of their genomes can transform cells, including human cells, and induce tumours in animal models. Moreover, DNA and RNA sequences and proteins of these three viruses have been discovered in tumour tissue. Despite these observations, their role in cancer remains controversial. So far, an association between cancer and the other human polyomaviruses is lacking. Because human polyomavirus DNA has been found in a broad spectrum of cell types, simultaneous dwelling with other oncogenic viruses is possible. Co-infecting human polyomaviruses may therefore act as a co-factor in the development of cancer, including those induced by other oncoviruses. Reviewing studies that report co-infection with human polyomaviruses and other tumour viruses in cancer tissue fail to detect a clear link between co-infection and cancer. Directions for future studies to elaborate on a possible auxiliary role of human polyomaviruses in cancer are suggested, and the mechanisms by which human polyomaviruses may synergize with other viruses in oncogenic transformation are discussed.