Association between human papillomavirus and Epstein - Barr virus DNA and gene promoter methylation of RB1 and CDH1 in the cervical lesions: a transversal study

Investigating the role of Epstein-Barr virus and human papillomavirus types 16 and 18 co-infections in cervical disease of Iranian women

Introduction

High-risk human papillomaviruses (HR-HPVs) are known to contribute to cervical cancer (CC), but the role of Epstein-Barr virus (EBV) in this process remains unclear, despite EBV's widespread detection in premalignant and malignant cervical tissues.

Methods

In this cross-sectional study of 258 cervical samples, including both formalin-fixed paraffin-embedded (FFPE) and fresh cervical tissues, the presence and viral load of HR-HPVs (HPV-16 and HPV-18) and EBV were evaluated in Iranian women with cervical intraepithelial neoplasia (CIN), squamous cell carcinoma (SCC), and a cervicitis control group using real-time PCR.

Results

The study revealed a significant correlation between disease severity and both increased HPV-16 positivity and HPV-16 and HPV-18 co-infection (p<0.001). Interestingly, the control group had a higher frequency of EBV-positive cases than SCC/CIN groups (p<0.001). HPV-16 DNA load increased with disease severity (P<0.001), while HPV-18 showed no significant difference (P=0.058). The control group had a higher EBV DNA load compared to SCC/CIN groups (P=0.033). HPV-16 increased the risk of CIN II, CIN III, and SCC, while HPV-18 increased the risk of CIN II and CIN III. Notably, EBV was associated with a lower risk of CIN groups and SCC.

Conclusions

No significant difference in EBV co-infection with HPV-16/18 was found, failing to support the hypothesis that EBV is a cofactor in CC. However, high EBV viral load in the control group suggests a potential "hit and run hypothesis" role in CC progression. This hypothesis suggests that EBV may contribute briefly to the initiation of CC with an initial impact but then becomes less actively involved in its ongoing progression.

The Prevalence of Epstein-Barr Virus in Normal, Premalignant, and Malignant Uterine Cervical Samples in Iran

INTRODUCTION

It is suggested that Epstein-Barr virus (EBV) may play an important role in cervical cancer development. Most studies found a higher rate of EBV in cervical cancer samples in comparison to premalignant and normal groups. In this regard, this study aimed to investigate the prevalence of EBV in cervical samples.

METHODS

In total, 364 samples from 179 healthy subjects, 124 women with premalignant lesions, and 61 patients with cervical cancer were investigated using nested-PCR.

RESULTS

The mean age ± SE was 54.1 ± 13.4 in women with cervical cancer, 36.1 ± 9.4 among women with premalignant lesions, and 36.6 ± 11.5 in healthy individuals. In total, 290 out of 364 samples were human papillomavirus (HPV) positive and the following HPV genotypes were detected among them: HPV 16/18 was found in 43.1%, 23.9%, and 65.5% of normal, premalignant, and malignant samples, respectively, and other high-risk types were detected in 56.9% of normal, 76.1% of premalignant, and 34.5% of malignant samples. The prevalence of EBV was found to be 9.8%, 2.4%, and 2.8% in cervical cancer, premalignant lesions, and normal specimens, respectively, and the difference was statistically significant (p = 0.028). The overall frequency of coinfection between EBV and HPV was shown to be 3.6%. The coinfection was more prevalent among HPV 16/18-infected samples than other high-risk HPVs (6.6 vs. 2.9%) although the difference was not reached a statistically significant difference (p = 0.23).

CONCLUSION

Our findings indicated that EBV could play an important role as a cofactor in the progression of cervical cancer. However, future studies with larger sample sizes and the expression analysis of EBV transcripts or proteins are mandatory.

Coinfections with additional oncoviruses in HPV+ individuals: Status, function and potential clinical implications

Oncovirus infections account for an estimated 12%-20% of human cancers worldwide. High-risk human papillomavirus (HPV) infection is the etiological agent of some malignancies such as cervical, oropharyngeal, anal, penile, vaginal, and vulvar cancers. However, HPV infection is not the only cause of these cancers or may not be sufficient to initiate cancer development. Actually, certain other risk factors including additional oncoviruses coinfections have been reported to increase the risk of patients exposed to HPV for developing different HPV-related cancers. In the current review, we summarize recent findings about coinfections with different oncoviruses in HPV+ patients from both clinical and mechanistic studies. We believe such efforts may lead to an interesting direction for improving our understanding and developing new treatments for virus-induced cancers.

Association between human herpesvirus infection and cervical carcinoma: a systematic review and meta-analysis

BACKGROUND

Cervical cancer (CC) is one of the most common gynecologic tumors among women around the world. Although the etiological role of human papillomavirus (HPV) in CC is well established, other factors in CC carcinogenesis remains unclear. Here, we performed a systematic review and meta-analysis to explore the association between infections of human herpesvirus (HHVs) and CC risk.

METHODS

Embase and PubMed databases were utilized to search the relevant studies. The revised JBI Critical Appraisal Tool was used to assess the quality of the included studies. Prevalence and odds ratios (ORs) with 95% confidence intervals (CI) were calculated to evaluate the association between viral infection and CC or precancerous cervical lesions (PCL).

RESULTS

Totally 67 eligible studies involving 7 different HHVs were included in meta-analysis. We found an increased risk of CC or PCL that was associated with the overall infection of HHVs (CC, OR = 2.74, 95% CI 2.13-3.53; PCL, OR = 1.95, 95% CI 1.58-2.41). Subgroup analysis showed a trend towards positive correlations between herpes simplex virus type 2 (HSV-2) infection and CC (OR = 3.01, 95% CI 2.24 to 4.04) or PCL (OR = 2.14, 95% CI 1.55 to 2.96), and the same is true between Epstein-Barr virus (EBV) infection and CC (OR = 4.89, 95% CI 2.18 to 10.96) or PCL (OR = 3.55, 95% CI 2.52 to 5.00). However, for HSV-1 and cytomegalovirus (HCMV), there was no association between viral infection and CC or PCL. By contrast, the roles of HHV-6, HHV-7, and Kaposi sarcoma-associated herpesvirus (KSHV) in cervical lesions were unclear due to the limited number of studies.

CONCLUSIONS

This study provided evidence that HHVs infection as a whole increase the risk of CC incidence. In addition, some types of HHVs such as EBV and HSV-2 may serve as potential targets in the development of new interventions or therapeutic strategies for cervical lesions.

[Influence of E-cadherin methylation on prognosis in children with acute lymphoblastic leukemia]

OBJECTIVES

To study the significance of E-cadherin and the association between E-cadherin methylation status and prognosis in children with acute lymphoblastic leukemia (ALL) by examining the mRNA and protein expression of E-cadherin and its gene methylation status in bone marrow mononuclear cells of children with ALL.

METHODS

The samples of 5 mL bone marrow blood were collected from 42 children with ALL who were diagnosed for the first time at diagnosis (pre-treatment group) and on day 33 of induction chemotherapy (post-treatment group). RT-qPCR, Western blot, and methylation-specific PCR were used to measure the mRNA and protein expression of E-cadherin and the methylation level of the E-cadherin gene. The changes in each index after induction chemotherapy were compared.

RESULTS

The mRNA and protein expression levels of E-cadherin in the post-treatment group were significantly higher than those in the pre-treatment group (P<0.05), while the positive rate of E-cadherin gene methylation in the post-treatment group was significantly lower than that in the pre-treatment group (P<0.05). At the end of the test, the children with negative methylation had significantly higher overall survival rate and event-free survival rate than those with positive methylation (P<0.05).

CONCLUSIONS

E-cadherin expression is associated with the development of ALL in children, and its decreased expression and increased methylation level may indicate a poor prognosis.

PCR Detection of Epstein-Barr Virus (EBV) DNA in Patients with Head and Neck Squamous Cell Carcinoma, in Patients with Chronic Tonsillitis, and in Healthy Individuals

Epstein-Barr virus (EBV) is a common virus worldwide that is an etiologic agent in the development of many diseases, including cancer. Recent reports have shown the association of EBV with tumorigenesis in head and neck squamous cell carcinoma (HNSCC). Moreover, EBV has been reported to be present in tonsillar tissues, which suggests a close relationship between viral infections and tonsillar diseases, including chronic tonsillitis. The aim of the study was to analyze the prevalence of EBV DNA in 86 patients with HNSCC, in 70 patients with chronic tonsillitis, and in 144 healthy individuals (control group) and the associations between EBV infection and clinicopathological and demographic characteristics and the use of stimulants in all study groups. The objective of this study was also to analyze the prevalence of coinfection with human papillomavirus (HPV). After prior DNA isolation, EBV detection was performed using an EBV kit by real-time polymerase chain reaction. The prevalence of EBV infection in patients with HNSCC, patients with chronic tonsillitis, and the control group was 47.7%, 60%, and 24.3%, respectively. Compared to controls, a significantly higher prevalence of EBV in patients with chronic tonsillitis and HNSCC may suggest that EBV is a potential risk factor. No association was found between EBV infection and demographic or clinical data. Further studies are warranted due to inconclusive reports that were mainly related to geographic distribution, sample type, and detection technique. Considering the prevalence of the virus and the risk of serious diseases, attention should be paid to screening diagnosis and prevention of the infection.

Characterization of High-Risk HPV/EBV Co-Presence in Pre-Malignant Cervical Lesions and Squamous Cell Carcinomas

High-risk human papillomaviruses (HR-HPVs) are the etiological agents of cervical cancer. However, a low proportion of HR-HPV-infected women finally develop this cancer, which suggests the involvement of additional cofactors. Epstein−Barr virus (EBV) has been detected in cervical squamous cell carcinomas (SCCs) as well as in low- (LSIL) and high-grade (HSIL) squamous intraepithelial lesions, although its role is unknown. In this study, we characterized HR-HPV/EBV co-presence and viral gene expression in LSIL (n = 22), HSIL (n = 52), and SCC (n = 19) from Chilean women. Additionally, phenotypic changes were evaluated in cervical cancer cells ectopically expressing BamHI-A Rightward Frame 1 (BARF1). BARF1 is a lytic gene also expressed in EBV-positive epithelial tumors during the EBV latency program. HPV was detected in 6/22 (27.3%) LSIL, 38/52 (73.1%) HSIL, and 15/19 (78.9%) SCC cases (p < 0.001). On the other hand, EBV was detected in 16/22 (72.7%) LSIL, 27/52 (51.9%) HSIL, and 13/19 (68.4%) SCC cases (p = 0.177). HR-HPV/EBV co-presence was detected in 3/22 (13.6%) LSIL, 17/52 (32.7%) HSIL, and 11/19 (57.9%) SCC cases (p = 0.020). Additionally, BARF1 transcripts were detected in 37/55 (67.3%) of EBV positive cases and in 19/30 (63.3%) of HR-HPV/EBV positive cases. Increased proliferation, migration, and epithelial-mesenchymal transition (EMT) was observed in cervical cancer cells expressing BARF1. Thus, both EBV and BARF1 transcripts are detected in low- and high-grade cervical lesions as well as in cervical carcinomas. In addition, BARF1 can modulate the tumor behavior in cervical cancer cells, suggesting a role in increasing tumor aggressiveness.

High-Risk Human Papillomavirus and Epstein-Barr Virus Coinfection: A Potential Role in Head and Neck Carcinogenesis

Simple Summary

A subset of carcinomas that arise in the head and neck region show a viral etiology. In fact, a subgroup of oropharyngeal cancers are caused by some types of human papillomavirus (HPV), so-called high-risk (HR)-HPVs, whereas undifferentiated nasopharyngeal carcinomas are etiologically related to Epstein–Barr virus (EBV). However, studies have reported the presence of both HR-HPV and EBV in some types of head and neck cancers. In this review, we discuss the potential contribution and role of HR-HPV/EBV coinfection in head and neck carcinogenesis, as well as the mechanisms that are potentially involved. In addition, HR-HPV/EBV interaction models are proposed.

Abstract

High-risk human papillomaviruses (HR-HPVs) and Epstein–Barr virus (EBV) are recognized oncogenic viruses involved in the development of a subset of head and neck cancers (HNCs). HR-HPVs are etiologically associated with a subset of oropharyngeal carcinomas (OPCs), whereas EBV is a recognized etiological agent of undifferentiated nasopharyngeal carcinomas (NPCs). In this review, we address epidemiological and mechanistic evidence regarding a potential cooperation between HR-HPV and EBV for HNC development. Considering that: (1) both HR-HPV and EBV infections require cofactors for carcinogenesis; and (2) both oropharyngeal and oral epithelium can be directly exposed to carcinogens, such as alcohol or tobacco smoke, we hypothesize possible interaction mechanisms. The epidemiological and experimental evidence suggests that HR-HPV/EBV cooperation for developing a subset of HNCs is plausible and warrants further investigation.

The Role of Coinfections in the EBV-Host Broken Equilibrium

The Epstein–Barr virus (EBV) is a well-adapted human virus, and its infection is exclusive to our species, generally beginning in the childhood and then persisting throughout the life of most of the affected adults. Although this infection generally remains asymptomatic, EBV can trigger life-threatening conditions under unclear circumstances. The EBV lifecycle is characterized by interactions with other viruses or bacteria, which increases the probability of awakening its pathobiont capacity. For instance, EBV infects B cells with the potential to alter the germinal center reaction (GCR)—an adaptive immune structure wherein mutagenic-driven processes take place. HIV- and Plasmodium falciparum-induced B cell hyperactivation also feeds the GCR. These agents, along with the B cell tropic KSHV, converge in the ontogeny of germinal center (GC) or post-GC lymphomas. EBV oral transmission facilitates interactions with local bacteria and HPV, thereby increasing the risk of periodontal diseases and head and neck carcinomas. It is less clear as to how EBV is localized in the stomach, but together with Helicobacter pylori, they are known to be responsible for gastric cancer. Perhaps this mechanism is reminiscent of the local inflammation that attracts different herpesviruses and enhances graft damage and chances of rejection in transplanted patients. In this review, we discussed the existing evidence suggestive of EBV possessing the potential to synergize or cooperate with these agents to trigger or worsen the disease.

The role of HPV-induced epigenetic changes in cervical carcinogenesis (Review)

Cervical cancer is associated with infection by certain types of human papillomaviruses (HPVs), and this affects women worldwide. Despite the improvements in prevention and cure of HPV-induced cervical cancer, it remains the second most common type of cancer in women in the least developed regions of the world. Epigenetic modifications are stable long-term changes that occur in the DNA, and are part of a natural evolutionary process of necessary adaptations to the environment. They do not result in changes in the DNA sequence, but do affect gene expression and genomic stability. Epigenetic changes are important in several biological processes. The effects of the environment on gene expression can contribute to the development of numerous diseases. Epigenetic modifications may serve a critical role in cancer cells, by silencing tumor suppressor genes, activating oncogenes, and exacerbating defects in DNA repair mechanisms. Although cervical cancer is directly related to a persistent high-risk HPV infection, several epigenetic changes have been identified in both the viral DNA and the genome of the infected cells: DNA methylation, histone modification and gene silencing by non-coding RNAs, which initiate and sustain epigenetic changes. In the present review, recent advances in the role of epigenetic changes in cervical cancer are summarized.

Identification of miPEP133 as a novel tumor-suppressor microprotein encoded by miR-34a pri-miRNA

Background

Very few proteins encoded by the presumed non-coding RNA transcripts have been identified. Their cellular functions remain largely unknown. This study identifies the tumor-suppressor function of a novel microprotein encoded by the precursor of miR-34a. It consists of 133 amino acid residues, thereby named as miPEP133 (pri-microRNA encoded peptide 133).

Methods

We overexpressed miPEP133 in nasopharyngeal carcinoma (NPC), ovarian cancer and cervical cancer cell lines to determine its effects on cell growth, apoptosis, migration, or invasion. Its impact on tumor growth was evaluated in a xenograft NPC model. Its prognostic value was analyzed using NPC clinical samples. We also conducted western blot, immunoprecipitation, mass spectrometry, confocal microscopy and flow cytometry to determine the underlying mechanisms of miPEP133 function and regulation.

Results

miPEP133 was expressed in normal human colon, stomach, ovary, uterus and pharynx. It was downregulated in cancer cell lines and tumors. miPEP133 overexpression induced apoptosis in cancer cells and inhibited their migration and invasion. miPEP133 inhibited tumor growth in vivo. Low miPEP133 expression was an unfavorable prognostic marker associated with advanced metastatic NPC. Wild-type p53 but not mutant p53 induced miPEP133 expression. miPEP133 enhanced p53 transcriptional activation and miR-34a expression. miPEP133 localized in the mitochondria to interact with mitochondrial heat shock protein 70kD (HSPA9) and prevent HSPA9 from interacting with its binding partners, leading to the decrease of mitochondrial membrane potential and mitochondrial mass.

Conclusion

miPEP133 is a tumor suppressor localized in the mitochondria. It is a potential prognostic marker and therapeutic target for multiple types of cancers.

Role of Epstein-Barr Virus and Human Papillomavirus Coinfection in Cervical Cancer: Epidemiology, Mechanisms and Perspectives

High-risk human papillomavirus (HR-HPV) is etiologically associated with the development and progression of cervical cancer, although other factors are involved. Epstein-Barr virus (EBV) detection in premalignant and malignant tissues from uterine cervix has been widely reported; however, its contribution to cervical cancer development is still unclear. Here, a comprehensive analysis regarding EBV presence and its potential role in cervical cancer, the frequency of EBV/HR-HPV coinfection in uterine cervix and EBV infection in tissue-infiltrating lymphocytes were revised. Overall, reports suggest a potential link of EBV to the development of cervical carcinomas in two possible pathways: (1) Infecting epithelial cells, thus synergizing with HR-HPV (direct pathway), and/or (2) infecting tissue-infiltrating lymphocytes that could generate local immunosuppression (indirect pathway). In situ hybridization (ISH) and/or immunohistochemical methods are mandatory for discriminating the cell type infected by EBV. However, further studies are needed for a better understanding of the EBV/HR-HPV coinfection role in cervical carcinogenesis.

Prevalence of human papillomavirus (HPV) in Brazil: A systematic review and meta-analysis

OBJECTIVES

This study aimed to estimate the prevalence of genital, anal and oral HPV infection in Brazil through systematic review and meta-analysis.

METHODS

We searched EMBASE, LILACS, MEDLINE, Web of Science and SciELO from inception to December 2018. Original research articles that assessed the prevalence of genital (i.e., cervical, penile), anal and oral HPV infection in Brazil were selected in pairs by independent authors. No sex, age, HPV vaccination, language or date restrictions were applied. HPV prevalence was estimated and stratified according to risk factors population and by geographic area throughout the country. The study prevalence was pooled using a random effects model. Analysis was performed using R (version 3.5.2), packages meta version 4.9-4 and metaphor 2.0-0. This review is registered on PROSPERO under protocol number CRD42016032751.

RESULTS

We identified 3,351 references. After the screening process, 139 of them were eligible for this systematic review (57,513 total participants). Prevalence of cervical HPV was 25.41% (95% CI 22.71-28.32). Additionally, prevalence was 36.21% (95% CI 23.40, 51.33) in the penile region, 25.68% (95%CI 14.64, 41.04) in the anal region, and 11.89% (95%CI 6.26, 21.43) in the oral region. Subgroup analysis showed prevalence in each anatomic site was higher in high-risk populations.

CONCLUSION

The prevalence of HPV is high in the Brazilian population and varies by population risk and anatomic body site, with lower rates in the oral cavity compared to that in the cervical, penile and anal region. Studies on HPV have primarily been developed to evaluate infection and cancer in the cervical region. There is a profound lack of HPV data in many geographic regions of Brazil and for different anatomic sites.

Epigenetic inactivation of tumour suppressor coding and non-coding genes in human cancer: an update

Cancer cells undergo many different alterations during their transformation, including genetic and epigenetic events. The controlled division of healthy cells can be impaired through the downregulation of tumour suppressor genes. Here, we provide an update of the mechanisms in which epigenetically altered coding and non-coding tumour suppressor genes are implicated. We will highlight the importance of epigenetics in the different molecular pathways that lead to enhanced and unlimited capacity of division, genomic instability, metabolic shift, acquisition of mesenchymal features that lead to metastasis, and tumour plasticity. We will briefly describe these pathways, focusing especially on genes whose epigenetic inactivation through DNA methylation has been recently described, as well as on those that are well established as being epigenetically silenced in cancer. A brief perspective of current clinical therapeutic approaches that can revert epigenetic inactivation of non-coding tumour suppressor genes will also be given.

The Role of Epstein-Barr Virus in Cervical Cancer: A Brief Update

Epstein–Barr virus (EBV) belongs to the group of gamma-herpes viruses and was the first recognized human oncovirus. EBV is responsible for infectious mononucleosis and multiple lymphoid and epithelial malignancies including B-cell lymphomas (Burkitt lymphoma, Hodgkin lymphoma, and post-transplant lymphoproliferative disorder), various T-cell/NK lymphoproliferative disorders, nasopharyngeal carcinoma, and gastric carcinoma, respectively. In addition, the presence of EBV has been documented in other cancers including breast, prostate, oral, and salivary gland carcinomas. The presence and role of EBV in cervical cancer and its precursor lesions (CIN) have also been described, but the results from the literature are inconsistent, and the causal role of EBV in cervical cancer pathogenesis has not been established yet. In the present review, we briefly surveyed and critically appraised the current literature on EBV in cervical cancer and its variants (lymphoepithelioma-like carcinoma) as well as its precursor lesions (CIN). In addition, we discussed the possible interactions between EBV and human papilloma virus as well as between EBV and immune checkpoint regulators (PD-L1). Though further studies are needed, the available data suggest a possible causal relationship between EBV and cervical cancer pathogenesis.

Using Methylation-Specific PCR to Study RB1 Promoter Hypermethylation

It has increasingly been considered crucial the understanding of DNA methylation of Tumor Suppressor Gene (TSG) promoters, such as that of retinoblastoma 1 gene (RB1), and its role during carcinogenesis. We present a detailed and optimized protocol of the methylation-specific PCR (MSP) technique to study RB1 gene promoter hypermethylation.

CDH1 promoter methylation in patients with cervical carcinoma: a systematic meta-analysis with trial sequential analysis

AIM

This study was performed to evaluate the correlation between CDH1 promoter methylation and cervical cancer.

METHODS

Trial sequential analysis was conducted to evaluate the required information size.

RESULTS

A total of 15 studies with 950 cervical cancers and 829 controls were identified. CDH1 promoter methylation was higher in cervical cancer than in cervical intraepithelial neoplasia lesions and normal cervical tissues. Subgroup analysis of ethnicity showed that CDH1 promoter methylation correlated with cervical cancer in Caucasians, but not in Asians. CDH1 promoter methylation was higher in cervical cancer cytology samples than in normal cytology samples. It was higher in squamous cell carcinoma than adenocarcinoma, but was not correlated with tumor stage, grade and overall survival.

CONCLUSION

CDH1 promoter methylation may be correlated with cervical cancer carcinogenesis, especially for Caucasians. It was associated with histological subtypes. Trial sequential analysis showed that more studies are needed.

Association between Epstein-Barr virus (EBV) and cervical carcinoma: A meta-analysis

OBJECTIVES

Human papillomavirus (HPV) has been implicated as a major factor in cervical carcinogenesis. However, many pieces of evidence gathered over the last two decades suggest Epstein-Barr virus (EBV) plays a secondary role in this process. The purpose of the present meta-analysis was to determine whether the presence of EBV infection increases the risk of cervical carcinoma.

METHODS

Based on 25 articles, the analysis yielded a 33.44% overall pooled prevalence of EBV.

RESULTS

The pooled prevalence was higher in patients with carcinoma (43.63%) than in healthy patients (19.0%) or patients with cervical intraepithelial neoplasia 1 (CIN1) (27.34%) or CIN2/3 (34.67%). Co-infection with EBV and HPV displayed a similar pattern. EBV infection was significantly and positively associated with lesion grade in cervical epithelia and was more prevalent in malignant lesions. Moreover, cervical carcinoma occurred four times as often among EBV positive women as in women without EBV infection (OR=4.01 [1.87-8.58]; p<0.001).

CONCLUSIONS

The existence of EBV(+)HPV(-) carcinomas, the confirmed expression of latent oncoproteins (EBNA1, EBNA2, LMP1) and EBERs in tumor cells, and the association of EBV with the integration of high-risk-HPV DNA in malignant specimens point to EBV as a co-factor (so far underestimated) in the genesis and/or progression of cervical carcinoma. However, further studies are necessary before the link between EBV and cervical carcinoma can be established.

The conundrum of the Epstein-Barr virus-associated gastric carcinoma in the Americas

Epstein-Barr virus-associated gastric carcinoma shows a higher prevalence in the Americas than Asia. We summarize all studies of Epstein Barr virus-associated gastric carcinoma in the Americas, focusing on host characteristics, environmental associations and phylogeographic diversity of Epstein-Barr virus strains. In the Americas, the prevalence of Epstein Barr virus-associated gastric carcinoma is 11.4%, more frequent in males and portray predominantly diffuse-type histology. EBERs, EBNAs, BARTs and LMP are the highest expressed genes; their variations in healthy individuals may explain the phylogeographic diversity of Epstein-Barr virus across the region. Gastric cancer cases harbor exclusively the western genotype (subtype D and kept Xho I site), suggesting a disrupted co-evolution between the pathogen and its host. Epstein-Barr virus-associated gastric carcinoma molecular subtype cases from The Cancer Genome Atlas display PIK3CA gene mutations, amplification of JAK2, PD-L1 and PD-L2 and CpG island methylator phenotype, leading to more extensive methylation of host and viral genomes than any other subtypes from the study. Environmental conditions include negative- and positive- associations with being firstborn child and smoking, respectively. A marginal association with H. pylori has also been reported. Lymphoepithelioma-like carcinoma is associated with Epstein Barr virus in 80%-86% of cases, most of which have been included as part of Epstein Barr virus-associated gastric carcinoma series (prevalence 1.1%-7.6%). Whether these cases represent a variant of Epstein-Barr virus-associated gastric carcinoma is discussed. We propose novel research strategies to solve the conundrum of the high prevalence of Epstein-Barr virus-associated gastric carcinoma in the Americas.

Putative biomarkers for cervical cancer: SNVs, methylation and expression profiles

Cervical cancer is primarily caused by Human papillomavirus (HPV) infection, but other factors such as smoking habits, co-infections and genetic background, can also contribute to its development. Although this cancer is avoidable, it is the fourth most frequent type of cancer in females worldwide and can only be treated with chemotherapy and radical surgery. There is a need for biomarkers that will enable early diagnosis and targeted therapy for this type of cancer. Therefore, a systems biology pipeline was applied in order to identify potential biomarkers for cervical cancer, which show significant reports in three molecular aspects: DNA sequence variants, DNA methylation pattern and alterations in mRNA/protein expression levels. CDH1, CDKN2A, RB1 and TP53 genes were selected as putative biomarkers, being involved in metastasis, cell cycle regulation and tumour suppression. Other ten genes (CDH13, FHIT, PTEN, MLH1, TP73, CDKN1A, CACNA2D2, TERT, WIF1, APC) seemed to play a role in cervical cancer, but the lack of studies prevented their inclusion as possible biomarkers. Our results highlight the importance of these genes. However, further studies should be performed to elucidate the impact of DNA sequence variants and/or epigenetic deregulation and altered expression of these genes in cervical carcinogenesis and their potential as biomarkers for cervical cancer diagnosis and prognosis.

The interaction between human papillomavirus and other viruses

The etiological role of human papillomavirus (HPV) in anogenital tract and head and neck cancers is well established. However, only a low percentage of HPV-positive women develop cancer, indicating that HPV is necessary but not sufficient in carcinogenesis. Several biological and environmental cofactors have been implicated in the development of HPV-associated carcinoma that include immune status, hormonal changes, parity, dietary habits, tobacco usage, and co-infection with other sexually transmissible agents. Such cofactors likely contribute to HPV persistent infection through diverse mechanisms related to immune control, efficiency of HPV infection, and influences on tumor initiation and progression. Conversely, HPV co-infection with other factors may also harbor anti-tumor effects. Here, we review epidemiological and experimental studies investigating human immunodeficiency virus (HIV), herpes simplex virus (HSV) 1 and 2, human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), BK virus (BKV), JC virus (JCV), and adeno-associated virus (AAV) as viral cofactors in or therapeutic factors against the development of genital and oral HPV-associated carcinomas.

Methylation pattern of CDH1 promoter and its association with CDH1 gene expression in cytological cervical specimens

Cervical cancer is the fourth leading cause of cancer mortality in females worldwide. Infection with high-risk human papillomavirus (HPV) is essential but insufficient to cause cervical cancer, and the clearance of HPV infection is mediated by the immune system. The deficit of molecules responsible for adhesion may play a role in the development of cervical cancer. E-cadherin is encoded by the cadherin 1 (CDH1) gene, and is involved in cell adhesion by forming adherens junctions. The aim of present study was to investigate the methylation pattern of the CDH1 promoter and to identify the association between CDH1 promoter hypermethylation, CDH1 gene expression and HPV infection in cervical specimens obtained from 93 patients with low-grade squamous intraepithelial lesions (SILs), high-grade SILs or squamous cell carcinomas, and from 47 patients with normal cervical cytology (HPV-negative). The methylation pattern of the CDH1 promoter was investigated by methylation-specific polymerase chain reaction and quantitative pyrosequencing. CDH1 gene expression was measured by relative quantification. CDH1 methylation was significantly higher in both types of lesions and in cervical cancer than in normal samples, and CDH1 gene expression was significantly reduced during SIL progression (P=0.0162). However, the influence of HPV infection or HPV E6 expression on the methylation pattern of the CDH1 gene or its gene expression levels could not be confirmed. The present results support that the methylation of the CDH1 gene is age-related in patients with cervical lesions (P=0.01085), and therefore, older patients could be more susceptible to cancer than younger patients. The important methylation of the CDH1 promoter occurred near the transcription factor binding sites on nucleotides -13 and +103, which are close to the translational start codon. These results suggest that methylation at these sites may be an important event in the transcriptional regulation of E-cadherin, and in patients harboring these methylated cytosines, this event may facilitate HPV-driven carcinogenesis.

BLCAP arrests G₁/S checkpoint and induces apoptosis through downregulation of pRb1 in HeLa cells

BLCAP (bladder cancer-associated protein) gene exhibited tumor suppressor function in different tumors and is regarded as a candidate tumor suppressor gene; however, the mechanism by which BLCAP exerts its function remains elusive. This study investigated the functional association between BLCAP and proliferation or apoptosis in cervical cancer cells, to identify the functional motifs of BLCAP. The BLCAP-shRNA expression vector based on pRNA-U6.1/Hygro plasmid was used to specifically inhibit BLCAP activity in HeLa cells. The optimal shRNA plasmid was selected to knock down BLCAP expression and the biological effects were investigated. The effects on cell cycle and apoptosis were detected by flow cytometric or Annexin V-FITC staining analysis. The gene expression profiles of HeLa cells transfected with blcap-wt and BLCAP-shRNA were analyzed using human signal pathway gene Oligochips. The levels of protein expression and interaction of BLCAP with Rb1 proteins were determined by western blotting and Co-IP assays. The site-specific mutagenesis assay was used to identify amino acid residues important for BLCAP. Significantly differentially expressed genes were found by gene Oligo chips analysis. These genes were all correlated with proliferation, cell cycle and apoptosis. The results of western blotting and Co-IP assays confirmed that overexpression of BLCAP could interact with Rb1 and inhibit Rb1 phosphorylation. Further investigation revealed that SAXX mutation in the key regions of BLCAP suppressed the function of BLCAP and significantly increased the level of phosphorylated Rb1 protein. Here our findings suggested that the functional association of BLCAP and Rb1 might play important roles in proliferation and apoptosis of HeLa cells. It suggested that BLCAP could be a novel therapeutic target for cervical cancer.