Breast cancer, cytomegalovirus and Epstein-Barr virus: a nested case-control study

The association between infectious agents and breast cancer: a review of the epidemiologic evidence

PURPOSE

Several viruses have been casually linked to human cancers, including cervical, nasopharyngeal, liver, sarcoma, and Merkel cell carcinomas. However, the etiologic contribution of viral infections to breast cancer, the number one incident cancer among women worldwide, is not well established. Among studies exploring associations of viruses with breast cancer, potential linkages have been identified between breast cancer and five viruses: beta retrovirus, (i.e., mouse mammary tumor virus), human papillomavirus, Epstein Barr virus. bovine leukemia virus, and human cytomegalovirus.

METHODS

In this review, we provide a comprehensive evaluation of epidemiological ecologic, case-control, case-only, and cohort studies investigating these associations. We discuss results from several existing reviews and meta-analyses, evaluate epidemiological studies published in the past five years, and assess the relationship between these viruses and breast tumor clinicopathological factors.

RESULTS

The strongest epidemiological evidence for a viral role in breast cancer exists for MMTV and HPV, though limitations include lack of prospective studies for MMTV and potential detection bias in HPV studies. Viral detection challenges have limited studies of EBV and HCMV. Fewer studies have evaluated BLV, and though it has been associated with higher risk of breast cancer, sample sizes are quite small.   CONCLUSION: While epidemiologic evidence exists for an association between these five viruses and breast cancer, various methodological issues and lack of prospective studies preclude robust conclusions. Future research should prioritize establishing a temporal relationship between infection and disease, minimizing misclassification of detection assays, and further exploring the influence of co-infections.

Influenza virus infection enhances tumour-specific CD8+ T-cell immunity, facilitating tumour control

Influenza A virus (IAV) can cause severe respiratory infection leading to significant global morbidity and mortality through seasonal epidemics. Likewise, the constantly increasing number of cancer diseases is a growing problem. Nevertheless, the understanding of the mutual interactions of the immune responses between cancer and infection is still very vague. Therefore, it is important to understand the immunological cross talk between cancer and IAV infection. In several preclinical mouse models of cancer, including melanoma and colorectal cancer, we observed that IAV infection in the lung significantly decreased the tumour burden. Concomitantly, tumour-specific CD8+ T-cells are strongly activated upon infection, both in the tumour tissue and in the lung. CD8+ T-cell depletion during infection reverses the reduced tumour growth. Interestingly, IAV infection orchestrated the migration of tumour-specific CD8+ T-cells from the tumour into the infected lung. Blocking the migration of CD8+ T-cells prevented the anti-tumoural effect. Thus, our findings show that viral respiratory infection has significant impact on the anti-tumour CD8+ T-cell response, which will significantly improve our understanding of the immunological cross talk between cancer and infection.

The association of human cytomegalovirus with biomarkers of inflammation and immune activation in breast cancer

BACKGROUND

The presence of human cytomegalovirus (HCMV) in breast cancer has been reported, suggesting a potential association between HCMV infection and breast carcinogenesis.

OBJECTIVE

To evaluate the association between HCMV infection and immune activation and inflammatory markers in breast cancer.

METHODS

HCMV DNA was detected from all patients using real-time PCR, Anti HCMV IgM and IgG antibodies were measured. IL-17 and IL-22 concentrations were detected by ELISA. Assessment of NLR and PLR was done, and cell proliferation was assessed using MTT assay.

RESULTS

The results revealed a significantly increased prevalence of anti-HCMV IgG and HCMV DNA in patients compared to both benign and control groups where positive HCMV prevalence was significantly associated with vascular invasion, proliferation rate, high neutrophil-to-lymphocyte ratio (NLR), and elevated IL-17 serum level. Furthermore, we demonstrated that increased serum IL-17 in patients was markedly associated with tumor stage, vascular invasion, and high NLR.

CONCLUSION

It can be concluded that HCMV infection may have vital roles in breast cancer pathogenesis. Moreover, altered peripheral blood cells and cytokines may result in disordered immune response in breast cancer patients.

Molecular Detection of Human Cytomegalovirus in Breast Cancer of Iranian Women Using Real-Time PCR

Background: The role of carcinogenic viruses in developing breast cancer has not yet been identified. Many studies have examined the association between breast cancer and human cytomegalovirus (HCMV), but conflicting results have been reported. Objectives: The aim of this study was to evaluate the levels of IgM & IgG antibodies against HCMV by identifying the viral genome in the breast tissue of women with breast cancer. Methods: A total of 60 patients with breast cancer and 60 healthy individuals (40 cases with fibroadenoma and 20 healthy samples) were selected. Serum levels of IgM & IgG antibodies against HCMV were measured by ELISA, and after DNA extraction from the breast tissue, the presence of the cytomegaloviruses (CMV) genome was assessed by Real-Time PCR. Results: Real-time PCR results showed that 20 samples of breast cancer tissue and 5 samples of fibroadenoma were positive for CMV genome (P = 0.001, OR: 5.50, CI 95%: 1.90 - 15.89). All samples had CMV-IgG antibody in their serum, but their mean serum level was higher in the cancer group (48.27 ± 15.99 U/mL) than the control group (40.11 ± 18.01 U/mL) (P = 0.004). However, CMV-IgM anti-viral antibody was positive in 5 cases with cancer and 3 cases in the control group. The mean serum concentration of this antibody was higher in the cancer group (6.60 ± 6.75 U/mL) than the control group (4.92 ± 3.03 U/mL) (P = 0.099). Conclusions: Increased serum levels of anti-CMV antibodies in patients with cancer, as well as the presence of viral genomes in some cases, indicate the carcinogenesis effect of the virus.

Productive Infection of Human Breast Cancer Cell Lines with Human Cytomegalovirus (HCMV)

Breast cancer is the leading cause of cancer deaths among women worldwide. There are many known risk factors for breast cancer, but the role of infectious disease remains unclear. Human cytomegalovirus (HCMV) is a widespread herpesvirus that usually causes little disease. Because HCMV has been detected in breast tumor biopsy samples and is frequently transmitted via human breast milk, we investigated HCMV replication in breast tumor cells. Four human breast cancer cell lines with different expression profiles for the key diagnostic markers of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), were infected with a bacterial artificial chromosome-derived HCMV clinical strain TB40/E tagged with green fluorescent protein (GFP). Fluorescence microscopy confirmed that all four breast cancer cell lines supported virus entry. RNA was isolated from infected cells and the expression of immediate early (UL123), early (UL54), and late (UL111A) genes was confirmed using PCR. Viral proteins were detected by immunoblotting, and viral progeny were produced during the infection of breast tumor cells, as evidenced by subsequent infection of fibroblasts with culture supernatants. These results demonstrate that breast tumor cells support productive HCMV infection and could indicate that HCMV replication may play a role in breast cancer progression.

Bystander Memory T Cells and IMiD/Checkpoint Therapy in Multiple Myeloma: A Dangerous Tango?

In this review article we discuss the role of the memory T cells in multiple myeloma (MM) and how they may influence immune responses in patients that received immunomodulating drugs and check point therapy.

Cytomegalovirus and cancer-related mortality in the national health and nutritional examination survey

PURPOSE

Cytomegalovirus (HCMV) is a common viral infection that shapes lifelong immunity. A history of infection with HCMV has been associated with many chronic diseases, including cancer. In addition, prospective cohort studies have established that HCMV is associated with all-cause mortality. However, there are limited data regarding HCMV and cancer mortality.

METHODS

Data were obtained from the National Health and Nutrition Examination Survey (NHANES) III study (1988-1994): subjects aged 18 to 98, who had HCMV serology results, did not report having cancer at baseline, and were eligible for mortality follow-up (n = 14,498). Mortality was ascertained until December 2011 using National Death Index (NDI) linkage.

RESULTS

The unadjusted risk of all-cancer mortality was higher in HCMV seropositive individuals (HR 2.74, 95% CI 2.05-3.64). This association was attenuated after adjusting for age (HR 1.39, 95% CI 1.02-1.92), and other covariates (age, sex, race/ethnicity, smoking status, BMI, education, and C-reactive protein (CRP); HR 1.21, 95% CI 0.91-1.81). There was a statistically significant interaction between HCMV and sex (p = 0.01): HCMV seropositivity was associated with increased cancer mortality in men (HR 1.65, 95% CI 0.99-2.73) but not in women (HR 0.95, 95% CI 0.59-1.54).

CONCLUSION(S)

Consistent with prior reports, HCMV seropositivity may be associated with an increased risk of cancer-related mortality but the association is partially driven by socioeconomic status and other risk factors. Future research is needed to determine whether HCMV is a risk factor for cancer, as well as identify the specific cancer types where HCMV increases mortality.

The human cytomegalovirus-encoded G protein-coupled receptor UL33 exhibits oncomodulatory properties

Herpesviruses can rewire cellular signaling in host cells by expressing viral G protein-coupled receptors (GPCRs). These viral receptors exhibit homology to human chemokine receptors, but some display constitutive activity and promiscuous G protein coupling. Human cytomegalovirus (HCMV) has been detected in multiple cancers, including glioblastoma, and its genome encodes four GPCRs. One of these receptors, US28, is expressed in glioblastoma and possesses constitutive activity and oncomodulatory properties. UL33, another HCMV-encoded GPCR, also displays constitutive signaling via Gα_q, Gα_i, and Gα_s proteins. However, little is known about the nature and functional effects of UL33-driven signaling. Here, we assessed UL33's signaling repertoire and oncomodulatory potential. UL33 activated multiple proliferative, angiogenic, and inflammatory signaling pathways in HEK293T and U251 glioblastoma cells. Notably, upon infection, UL33 contributed to HCMV-mediated STAT3 activation. Moreover, UL33 increased spheroid growth in vitro and accelerated tumor growth in different in vivo tumor models, including an orthotopic glioblastoma xenograft model. UL33-mediated signaling was similar to that stimulated by US28; however, UL33-induced tumor growth was delayed. Additionally, the spatiotemporal expression of the two receptors only partially overlapped in HCMV-infected glioblastoma cells. In conclusion, our results unveil that UL33 has broad signaling capacity and provide mechanistic insight into its functional effects. UL33, like US28, exhibits oncomodulatory properties, elicited via constitutive activation of multiple signaling pathways. UL33 and US28 might contribute to HCMV's oncomodulatory effects through complementing and converging cellular signaling, and hence UL33 may represent a promising drug target in HCMV-associated malignancies.

Breast cancer and cytomegalovirus

PURPOSE

To determine whether cytomegalovirus is causally associated with breast cancer and whether cytomegalovirus should be categorised as an oncogenic virus.

METHODS

We undertook a review of published epidemiological and laboratory studies, using established causal criteria: Bradford Hill criteria to determine whether cytomegalovirus is associated with breast cancer; and Evans/Mueller criteria to determine whether cytomegalovirus should be categorised as an oncogenic virus.

RESULTS

Although there are inconsistencies in the findings of published epidemiological and laboratory studies, these may be explained by factors such as: differences in timing of blood samples, differences in selection of cases and controls, or high cytomegalovirus seroprevalence among participants in the epidemiological studies; and, in the laboratory studies, differences in sample preparations, age of sample, whether or not paired breast cancer and normal breast tissue samples were used, differences in the tests, primers and/or antibodies used, differences in histological types of breast cancer studied, and/or features of the virus.

CONCLUSIONS

Overall, the results of published studies of cytomegalovirus and breast cancer suggest cytomegalovirus is a causal factor for at least some types of breast cancer. If the evidence for a link between cytomegalovirus and breast cancer continues to strengthen, further research could lead to: targeted screening; therapy using antiviral drugs; and, perhaps, primary prevention of a significant proportion of breast cancer. Vaccination against viruses has already been shown to be effective in preventing cervix and liver cancer; cytomegalovirus vaccines are already under development.

Protein and DNA evidences of HCMV infection in primary breast cancer tissues and metastatic sentinel lymph nodes

BACKGROUND AND OBJECTIVE

Breast cancer is the leading cause of death in women worldwide. There are evidences that human cytomegalovirus (HCMV) infection is associated with several malignant tumors. This study aims to investigate the infection of human cytomegalovirus (HCMV) in a large sample of breast cancer patients, and conduct a correlation analysis of clinical and pathological factors, to provide evidence for whether HCMV infection is associated with breast cancer development, progression and metastasis.

MATERIALS AND METHODS

A total of 438 tissue samples (including breast cancer tissue, paracancerous tissue and sentinel lymph node [SLN] tissue) obtained from 146 patients who were diagnosed with breast cancer and intraoperatively underwent unilateral axillary SLN biopsy at the Affiliated Hospital of Qingdao University from June 2013 to June 2014 were included into this study. These tissue samples were divided into two groups: SLN positive group and SLN negative group. The clinical information is collated and numbered. Normal breast tissues of 40 patients with cyclomastopathy were taken as controls. The expressions of HCMV immediate-early (IE) and late antigen (LA) proteins of breast cancer tissues, paracancerous tissues, SLN tissues and normal breast tissues were analyzed by immunohistochemistry, and HCMV infection of the samples was graded according to the percentage of the positive cells, and HCMV IE2 mRNA expression was detected by reverse transcription polymerase chain reaction. The clinical data were collated and statistically analyzed.

RESULTS

HCMV IE and LA proteins were highly expressed in all breast cancer tissue samples. IE proteins were detected in 47.9% (70/146) of paracancerous tissue samples, and LA proteins were detected in 53.4% (78/146) of paracancerous tissue samples. IE and LA proteins were expressed in 92.6% of metastatic SLN samples (62/68) and in most of the tumor cells. Inflammatory cells in 60% (42/70) of non-metastatic samples were positive for HCMV. HCMV DNA was present in 100% of breast cancer tissue samples, 50% of paracancerous tissue samples, and 91% of metastatic SLN samples; but this was not present in HCMV negative and non-metastatic SLN samples. Differences in HCMV infection, and estrogen receptor-α, progesterone receptor, Elston classification, Ki67 percentage, Her-2 and Luminal type and other clinical indicators were not statistically significant.

CONCLUSION

HCMV infection is common in breast cancer tissues, paracancerous tissues and SLN tissues. The severity of HCMV infection varied markedly with tissue type. HCMV infection might be associated with metastasis and invasion of breast cancer. The expression of HCMV IE2 was associated to breast cancer and lymph node metastasis. The expression level of estrogen receptor-α was related to HCMV infection.

An integrative functional genomics framework for effective identification of novel regulatory variants in genome-phenome studies

BACKGROUND

Genome-phenome studies have identified thousands of variants that are statistically associated with disease or traits; however, their functional roles are largely unclear. A comprehensive investigation of regulatory mechanisms and the gene regulatory networks between phenome-wide association study (PheWAS) and genome-wide association study (GWAS) is needed to identify novel regulatory variants contributing to risk for human diseases.

METHODS

In this study, we developed an integrative functional genomics framework that maps 215,107 significant single nucleotide polymorphism (SNP) traits generated from the PheWAS Catalog and 28,870 genome-wide significant SNP traits collected from the GWAS Catalog into a global human genome regulatory map via incorporating various functional annotation data, including transcription factor (TF)-based motifs, promoters, enhancers, and expression quantitative trait loci (eQTLs) generated from four major functional genomics databases: FANTOM5, ENCODE, NIH Roadmap, and Genotype-Tissue Expression (GTEx). In addition, we performed a tissue-specific regulatory circuit analysis through the integration of the identified regulatory variants and tissue-specific gene expression profiles in 7051 samples across 32 tissues from GTEx.

RESULTS

We found that the disease-associated loci in both the PheWAS and GWAS Catalogs were significantly enriched with functional SNPs. The integration of functional annotations significantly improved the power of detecting novel associations in PheWAS, through which we found a number of functional associations with strong regulatory evidence in the PheWAS Catalog. Finally, we constructed tissue-specific regulatory circuits for several complex traits: mental diseases, autoimmune diseases, and cancer, via exploring tissue-specific TF-promoter/enhancer-target gene interaction networks. We uncovered several promising tissue-specific regulatory TFs or genes for Alzheimer's disease (e.g. ZIC1 and STX1B) and asthma (e.g. CSF3 and IL1RL1).

CONCLUSIONS

This study offers powerful tools for exploring the functional consequences of variants generated from genome-phenome association studies in terms of their mechanisms on affecting multiple complex diseases and traits.

Oncogenic Viruses and Breast Cancer: Mouse Mammary Tumor Virus (MMTV), Bovine Leukemia Virus (BLV), Human Papilloma Virus (HPV), and Epstein-Barr Virus (EBV)

Background

Although the risk factors for breast cancer are well established, namely female gender, early menarche and late menopause plus the protective influence of early pregnancy, the underlying causes of breast cancer remain unknown. The development of substantial recent evidence indicates that a handful of viruses may have a role in breast cancer. These viruses are mouse mammary tumor virus (MMTV), bovine leukemia virus (BLV), human papilloma viruses (HPVs), and Epstein–Barr virus (EBV-also known as human herpes virus type 4). Each of these viruses has documented oncogenic potential. The aim of this review is to inform the scientific and general community about this recent evidence.

The evidence

MMTV and human breast cancer—the evidence is detailed and comprehensive but cannot be regarded as conclusive. BLV and human breast cancer—the evidence is limited. However, in view of the emerging information about BLV in human breast cancer, it is prudent to encourage the elimination of BLV in cattle, particularly in the dairy industry. HPVs and breast cancer—the evidence is substantial but not conclusive. The availability of effective preventive vaccines is a major advantage and their use should be encouraged. EBV and breast cancer—the evidence is also substantial but not conclusive. Currently, there are no practical means of either prevention or treatment. Although there is evidence of genetic predisposition, and cancer in general is a culmination of events, there is no evidence that inherited genetic traits are causal.

Conclusion

The influence of oncogenic viruses is currently the major plausible hypothesis for a direct cause of human breast cancer.

Breast Cancer Association with Cytomegalo Virus-A Tertiary Center Case-Control Study

PURPOSE

Cytomegalo virus is a ubiquitous virus often associated with congenital infections. Some studied have claimed an association between infection with this virus and development of breast cancer. The aim of this prospective research was to study the difference in Cytomegalo virus sero-positivity among patients with breast cancer and benign breast diseases, and thereby to prove any association.

MATERIALS AND METHODS

This was a hospital based Case-Control study conducted at the General Surgery wards of our hospital, a tertiary level public sector health care institution. This study was done on 130 patients with breast swellings who underwent surgical excision of their lumps over a 1-year period. Patients with histologically proven malignancies were selected as cases while proven benign cases were deemed to be the controls. IgG and IgM antibodies to Cytomegalo virus were checked in the patients from both groups.

RESULTS

All of the studied patients turned out to be positive for Immunoglobulin G against Cytomegalo virus while all the patients were found to be negative for Immunoglobulin M. There was no difference in the antibody titers among the benign and malignant cases in the study. Logistic regression calculation was also carried out including the study parameters and other known risk factors.

CONCLUSIONS

We conclude that there is no association between Cytomegalo virus sero-positivity and breast cancer. Another conclusion is that the studied adult population has been exposed to Cytomegalo virus in some point of their lives. Further studies of a larger magnitude are essential to confirm our results.

Non-oncogenic Acute Viral Infections Disrupt Anti-cancer Responses and Lead to Accelerated Cancer-Specific Host Death

In light of increased cancer prevalence and cancer-specific deaths in patients with infections, we investigated whether infections alter anti-tumor immune responses. We report that acute influenza infection of the lung promotes distal melanoma growth in the dermis and leads to accelerated cancer-specific host death. Furthermore, we show that during influenza infection, anti-melanoma CD8⁺ T cells are shunted from the tumor to the infection site, where they express high levels of the inhibitory receptor programmed cell death protein 1 (PD-1). Immunotherapy to block PD-1 reverses this loss of anti-tumor CD8⁺ T cells from the tumor and decreases infection-induced tumor growth. Our findings show that acute non-oncogenic infection can promote cancer growth, raising concerns regarding acute viral illness sequelae. They also suggest an unexpected role for PD-1 blockade in cancer immunotherapy and provide insight into the immune response when faced with concomitant challenges.

Detection of Human Cytomegalovirus in Malignant and Benign Breast Tumors in Egyptian Women

INTRODUCTION

Previous studies have reported a role for human cytomegalovirus (HCMV) in breast carcinogenesis. We sought to assess the role of HCMV infection in the development and/or progression of breast cancer (BC) among Egyptian patients.

PATIENTS AND METHODS

The study included 61 patients with BC cases. Of these 61 patients, 40 had been assessed for HCMV in the blood, BC tissue samples, and adjacent non-neoplastic tissue samples, and 21 had been assessed for HCMV in the tissue only. Tissue samples from 20 patients with fibroadenoma (FA) were also included. As a control group, 41 blood samples obtained from healthy women with no history of cancer were used as a blood control group. HCMV was assessed using enzyme-linked immunosorbent assay, real-time polymerase chain reaction (PCR), and immunohistochemistry (IHC).

RESULTS

A significant difference was found in the index value for the anti-CMV IgG antibodies between the BC patients and the control group (P = .001). Using real-time PCR, HCMV DNA was detected in 11 of 61 BC tissues (18%) compared with 1 of 20 FA tissues (5%). HCMV DNA was present in 8 of the 40 plasma samples (20%). Regarding the viral proteins, 21 of 61 samples (34.4%) were positive for early/immediate early (E/IE) and 49 (80.3%) were positive for PP65 expression by IHC. The concordance between the results obtained by the different assays was low. CMVPP65 expression was significantly associated with E/IE protein expression in the malignant and FA groups (P < .001).

CONCLUSION

The presence of CMV proteins and DNA in BC tissues suggests a role for this virus. However, the basic criteria to support a causal association of HCMV with BC were not fulfilled.

Clinical study on the relationship between hepatitis B virus infection and risk of breast cancer: a large sized case-control and single center study in southwest of China

Purpose

Chronic hepatitis C virus (HCV) infection is reported to be associated with early-onset breast cancer, while, as a hepadnavirus, hepatitis B virus(HBV) infection is more common than HCV in China. In this article, it is aimed to study the relationship between HBV infection and risk of breast cancer in China.

Methods

The clinical data of 2452 cases of initially diagnosed breast cancer and 1926 cases of benign breast disease (as controls) with the consecutive reports of HBV serological markers and liver function tests, available in the Electronic Medical Records of the Breast Cancer Center of Chongqing, the southwest of China, from January 2011 to March 2015, were collected for analysis.

Results

The average age of the initially diagnosed breast cancer patients was 50.3±11.3 years with the age peaking about 40- 49yeaers (39.7%). The positive rate (8.2%) of hepatitis B surface antigen in breast cancer patients was relatively higher than that (7.8%) in controls (P>0.05). While, the positive rate (66.4%)of hepatitis B core antibody in breast cancer patients was significantly higher than that (53.7%) in controls (P<0.05), so were the similar results in the age groups of 40-49 years, after multiple layer analysis stratified by age and compare HBV markers adjusting age with binary logistic regression. Meanwhile, the status of albumin, aminotransferase and aspartate transaminase (41.4 g/L, 22.9 U/L, 22.0 U/L) in breast cancer patients were significantly poorer than those (44.1 g/L,16.8 U/L, 19.2 U/L) in controls (P<0.05).

Conclusions

Exposure to HBV infection may be a risk factor for breast cancer and may be also related to the earlier age onset of breast cancer (peaked around 40-49 years) among Chinese females.

Does Regular Exercise Counter T Cell Immunosenescence Reducing the Risk of Developing Cancer and Promoting Successful Treatment of Malignancies?

Moderate intensity aerobic exercise training or regular physical activity is beneficial for immune function. For example, some evidence shows that individuals with an active lifestyle exhibit stronger immune responses to vaccination compared to those who are inactive. Encouragingly, poor vaccine responses, which are characteristic of an ageing immune system, can be improved by single or repeated bouts of exercise. In addition, exercise-induced lymphocytosis, and the subsequent lymphocytopenia, is thought to facilitate immune surveillance, whereby lymphocytes search tissues for antigens derived from viruses, bacteria, or malignant transformation. Aerobic exercise training is anti-inflammatory and is linked to lower morbidity and mortality from diseases with infectious, immunological, and inflammatory aetiologies, including cancer. These observations have led to the view that aerobic exercise training might counter the age-associated decline in immune function, referred to as immunosenescence. This article summarises the aspects of immune function that are sensitive to exercise-induced change, highlighting the observations which have stimulated the idea that aerobic exercise training could prevent, limit, or delay immunosenescence, perhaps even restoring aged immune profiles. These potential exercise-induced anti-immunosenescence effects might contribute to the mechanisms by which active lifestyles reduce the risk of developing cancer and perhaps benefit patients undergoing cancer therapy.

Evaluation of human cytomegalovirus antigen expression in invasive breast carcinoma in a population of Iranian patients

Background

The role of human cytomegalovirus (HCMV) in the development of breast carcinoma is questionable. The aim of this study was to evaluate the expression of the immediate early antigen (IE) of HCMV in breast carcinoma and its association with some clinicopathologic factors in a population of Iranian patients.

Methods

Formalin-fixed and paraffin-embedded tissue blocks from the pathology laboratories of the Azahra and Shahid Beheshti hospitals, Isfahan, Iran, from 2013 to 2016, were used in the study. We used immunohistochemistry and real-time PCR to detect the IE-antigen of HCMV in breast carcinoma, normal tissue adjacent to carcinoma, and normal tissue from mammoplasty specimens.

Results

A total of 96 samples were evaluated: 70 invasive breast carcinoma of different histologic subtypes and 26 mammoplasty normal breast tissues. All the samples were negative for IE-antigen expression. No relationship was seen between breast cancer and HCMV in this study.

Conclusions

The results of this study failed to show any relationship between HCMV and the development of breast carcinoma.

Low Expression of Estrogen Receptor-α and Progesterone Receptor in Human Breast Cancer Tissues Is Associated With High-Grade Human Cytomegalovirus Protein Expression

BACKGROUND

The underlying mechanisms for breast cancer (BC) are largely unknown. We investigated possible correlations between the expression levels of human cytomegalovirus (HCMV) proteins and established histopathological markers of BC, including expression of estrogen receptor (ER)-α, the progesterone receptor (PgR), and HER2.

MATERIALS AND METHODS

We retrospectively examined paraffin-embedded biopsy specimens of BC (n = 62), ductal carcinoma in situ (n = 19), and adjacent normal breast tissue (n = 42) for HCMV immediate-early protein (IE), HCMV late antigen, HCMV DNA and RNA, and investigated possible correlations between them and expression of ER-α, PgR, and HER2.

RESULTS

HCMV DNA and RNA were detected in all examined infiltrating BCs. High-grade positivity for HCMV-IE was detected in 77% of infiltrating BCs, 39% of ductal carcinomas in situ, and 7% of tumor-free breast tissue samples. HCMV expression correlated inversely with ER-α (P = .02) and PgR (P = .003) expression. HER2 expression was also reduced in HCMV-positive samples without reaching a level of statistical significance (P = .09).

CONCLUSION

The negative correlation between high-grade expression HCMV-IE and hormone receptor expression suggests a role for HCMV in hormone receptor-negative BC tumors, possibly by forcing BC cells into a more aggressive phenotype.

Cytomegalovirus, Macrophages and Breast Cancer

The human cytomegalovirus (HCMV) is a betaherpesvirus that is highly host specific, infects among others epithelial cells and macrophages, and has been recently mentioned as having oncomodulatory properties. HCMV is detected in the breast tumor tissue where macrophages, especially tumor associated macrophages, are associated with a poor prognosis. In this review, we will discuss the potential implication of HCMV in breast cancer with emphasis on the role played by macrophages.

Humoral Immunity to Cytomegalovirus Glycoprotein B in Patients With Breast Cancer and Matched Controls: Contribution of Immunoglobulin γ, κ, and Fcγ Receptor Genes

Increasing evidence implicates human cytomegalovirus (HCMV) in the etiopathogenesis of breast cancer. Antibodies to this virus in patients with breast cancer have been reported, but no large-scale studies have been conducted to determine whether the antibody levels differ between patients and matched controls. Using specimens from a large (1712 subjects) multiethnic case-control study, we aimed to determine whether the levels of antibodies to the HCMV glycoprotein B (gB) differed between patients and controls and whether they were associated with particular immunoglobulin γ marker (GM), κ marker (KM), and Fcγ receptor (FcγR) genotypes. A combined analysis showed that anti-gB immunoglobulin G antibody levels were higher in healthy controls than in patients (P < .0001). Stratified analyses showed population-specific differences in the magnitude of anti-gB antibody responsiveness and in the contribution of particular GM, KM, and FcγR genotypes to these responses. These findings may have implications for HCMV-based immunotherapy against breast cancer and other HCMV-associated diseases.

Cytomegalovirus and Epstein-Barr virus in breast cancer

Findings of polymerase chain reaction (PCR) studies of cytomegalovirus (CMV) and Epstein-Barr virus (EBV) and breast cancer vary, making it difficult to determine whether either, both, or neither virus is causally associated with breast cancer. We investigated CMV and EBV in paired samples of breast cancer and normal breast tissue from 70 women using quantitative PCR. A serum sample from each woman was tested for CMV and EBV IgG. To place our results in context, we reviewed the existing literature and performed a meta-analysis of our results together with previous PCR studies of EBV, CMV, and breast cancer. Of the serology samples, 67 of 70 (96%) were EBV IgG positive and 49 of 70 (70%) were CMV IgG positive. QPCR detected EBV in 24 (34%) of the tumour and 9 (13%) of the paired normal specimens and CMV in 0 (0%) of the tumour and 2 (3%) of the paired normal specimens. Our findings, together with earlier results summarised in the meta-analysis, suggest several possibilities: variable findings may be due to limitations of molecular analyses; 'hit and run' oncogenesis may lead to inconsistent results; one or both viruses has a role at a later stage in breast cancer development; infection with multiple viruses increases breast cancer risk; or neither virus has a role. Future studies should focus on ways to investigate these possibilities, and should include comparisons of breast cancer tissue samples with appropriate normal tissue samples.

Breast cancer: is there a viral connection?

Viruses are known to be etiologically related to several types of human cancer. In several published studies, viruses such as human mammary tumor virus, human papillomaviruses, Epstein-Barr virus, human cytomegalovirus, herpes simplex virus, and measles virus have been implicated in the pathogenesis of a subset of breast cancers (BC). However, these studies have produced conflicting results, causing considerable controversy. In this context, recent demonstration of elevated levels of mutagenic antiviral enzyme APOBEC3B in a majority of BCs is a highly significant development, as it provides a possible mechanism for development of large numbers of mutations (kataegis) that characterize many of the BCs. It has also provided further impetus for revaluating the role of viruses in the pathogenesis of BC.

The oncogenic potential of human cytomegalovirus and breast cancer

Breast cancer is the leading causes of cancer-related death among women. The vast majority of breast cancers are carcinomas that originate from cells lining the milk-forming ducts of the mammary gland. Numerous articles indicate that breast tumors exhibit diverse phenotypes depending on their distinct physiopathological signatures, clinical courses, and therapeutic possibilities. The human cytomegalovirus (HCMV) is a multifaceted highly host specific betaherpesvirus that is regarded as asymptomatic or mildly pathogenic virus in immunocompetent host. HCMV may cause serious in utero infections as well as acute and chronic complications in immunocompromised individual. The involvement of HCMV in late inflammatory complications underscores its possible role in inflammatory diseases and cancer. HCMV targets a variety of cell types in vivo, including macrophages, epithelial cells, endothelial cells, fibroblasts, stromal cells, neuronal cells, smooth muscle cells, and hepatocytes. HCMV can be detected in the milk after delivery and thereby HCMV could spread to adjacent mammary epithelial cells. HCMV also infects macrophages and induces an atypical M1/M2 phenotype, close to the tumor-associated macrophage phenotype, which is associated with the release of cytokines involved in cancer initiation or promotion and breast cancer of poor prognosis. HCMV antigens and DNA have been detected in tissue biopsies of breast cancers and elevation in serum HCMV IgG antibody levels has been reported to precede the development of breast cancer in some women. In this review, we will discuss the potential role of HCMV in the initiation and progression of breast cancer.

Role of viruses in the development of breast cancer

The most common cancer worldwide among women is breast cancer. The initiation, promotion, and progression of this cancer result from both internal and external factors. The International Agency for Research on Cancer stated that 18-20% of cancers are linked to infection, and the list of definite, probable, and possible carcinogenic agents is growing each year. Among them, biological carcinogens play a significant role. In this review, data covering infection-associated breast and lung cancers are discussed and presented as possible involvements as pathogens in cancer. Because carcinogenesis is a multistep process with several contributing factors, we evaluated to what extent infection is significant, and concluded that members of the herpesvirus, polyomavirus, papillomavirus, and retrovirus families definitely associate with breast cancer. Detailed studies of viral mechanisms support this conclusion, but have presented problems with experimental settings. It is apparent that more effort needs to be devoted to assessing the role of these viruses in carcinogenesis, by characterizing additional confounding and synergistic effects of carcinogenic factors. We propose that preventing and treating infections may possibly stop or even eliminate certain types of cancers.

High prevalence of human cytomegalovirus proteins and nucleic acids in primary breast cancer and metastatic sentinel lymph nodes

Background

Breast cancer is a leading cause of death among women worldwide. Increasing evidence implies that human cytomegalovirus (HCMV) infection is associated with several malignancies. We aimed to examine whether HCMV is present in breast cancer and sentinel lymph node (SLN) metastases.

Materials and Methods

Formalin-fixed paraffin-embedded tissue specimens from breast cancer and paired sentinel lymph node (SLN) samples were obtained from patients with (n = 35) and without SLN metastasis (n = 38). HCMV immediate early (IE) and late (LA) proteins were detected using a sensitive immunohistochemistry (IHC) technique and HCMV DNA by real-time PCR.

Results

HCMV IE and LA proteins were abundantly expressed in 100% of breast cancer specimens. In SLN specimens, 94% of samples with metastases (n = 34) were positive for HCMV IE and LA proteins, mostly confined to neoplastic cells while some inflammatory cells were HCMV positive in 60% of lymph nodes without metastases (n = 35). The presence of HCMV DNA was confirmed in 12/12 (100%) of breast cancer and 10/11 (91%) SLN specimens from the metastatic group, but was not detected in 5/5 HCMV-negative, SLN-negative specimens. There was no statistically significant association between HCMV infection grades and progesterone receptor, estrogen receptor alpha and Elston grade status.

Conclusions

The role of HCMV in the pathogenesis of breast cancer is unclear. As HCMV proteins were mainly confined to neoplastic cells in primary breast cancer and SLN samples, our observations raise the question whether HCMV contributes to the tumorigenesis of breast cancer and its metastases.

An expanded myeloid derived suppressor cell population does not play a role in gammaherpesvirus-exacerbated breast cancer metastases

Background

Mice latently infected with murine gammaherpesvirus 68 (HV-68) and transplanted with 4 T1 breast cancer cells developed exacerbated metastatic lesions when compared to controls. The mechanisms responsible for this viral-exacerbated disease were not clear. The ability of HV-68 infection to induce S100A8 and S100A9 production and to expand a population of CD11b+Gr-1+ cells suggested that increased numbers, or activity, of viral-expanded myeloid derived suppressor cells (MDSCs) might contribute to HV-68-associated metastatic breast cancer in this model. We questioned whether mock or HV-68 infected mice with significant breast cancer might have differences in the number and/or activity of MDSCs.

Methods

Myeloid-derived macrophages and dendritic cells were isolated from normal mice and cultured in vitro with HV-68 to assess S100A8 and S100A9 mRNA and protein expression. In vivo studies were performed using groups of mice that were mock treated or infected with HV-68. After viral latency was established, 4 T1 breast cancer cells were transplanted in mice. When primary breast tumors were present mice were euthanized and cells isolated for phenotyping of myeloid cell populations using FACS, and for ex vivo analysis of suppressor activity. Serum from these animals was also collected to quantify S100A8 and S100A9 levels.

Results

In vitro studies demonstrated that direct exposure of myeloid cells to HV-68 did not induce increased expression of S100A8 or S100A9 mRNAs or secreted protein. HV-68 infected mice with metastatic breast cancer disease had no increases in S100A8/A9 levels and no significant increases in the numbers or activation of CD11b+Gr-1+MDSCs when compared to mock treated mice with breast cancer.

Conclusions

Together these studies are consistent with the notion that expanded myeloid derived suppressor cells do not play a role in gammaherpesvirus-exacerbated breast cancer metastases. The mechanisms responsible for HV-68 induced exacerbation of metastatic breast cancer remain unclear.

Exploring the prevalence of ten polyomaviruses and two herpes viruses in breast cancer

Several different viruses have been proposed to play a role in breast carcinogenesis. The aim of this study was to investigate the prevalence of a subset of viruses in breast cancer tissue. We investigated the prevalence of 12 DNA viruses: EBV and CMV from the Herpesviridae family and SV40, BKV, JCV, MCV, WUV, KIV, LPV, HPyV6, HPyV7, and TSV from the Polyomaviridae family in 54 fresh frozen breast tumour specimens. Relevant clinical data and basic lifestyle data were available for all patients. The tissue samples were DNA extracted and real-time PCR assays were used for viral detection.The highest prevalence, 10% (5/54), was found for EBV. MCV, HPyV6, and HPyV7 were detected in single patient samples (2% each), while WUV, KIV, JCV, BKV, LPV, SV40, TSV and CMV were not detected in the 54 breast cancer specimens analysed here. Further investigations are needed to elucidate the potential role of viruses, and particularly EBV, in breast carcinogenesis.

Genetic markers of immunoglobulin G and susceptibility to breast cancer

Immunoglobulin GM allotypes, antigenic determinants of γ chains, are encoded by three very closely linked codominant genes on chromosome 14q32. Particular GM alleles/haplotypes are associated with antibody responses to certain tumor antigens and contribute to the cytotoxicity of breast cancer cells, but their possible role in susceptibility to this malignancy has not been adequately examined. Using a matched case-control design, we genotyped a large (1710 subjects) study population from Japan and Brazil for several GM alleles to determine whether these determinants are associated with susceptibility to breast cancer. After adjusting for the potential confounders, the GM 3 allele of IgG1 was significantly associated with susceptibility to breast cancer in white subjects from Brazil (OR=2.07, CI 1.16-3.71; p=0.0147). These data show that Caucasians with the GM 3 allele are over twice as likely to develop breast cancer as those who lack this allele. Since this allele modulates an immune evasion strategy of cytomegalovirus, the results also shed light on the possible mechanism underlying the reported involvement of this virus in the etiology of breast cancer.

Exacerbated metastatic disease in a mouse mammary tumor model following latent gammaherpesvirus infection

Background

Controversy exists as to the ability of human gammaherpesviruses to cause or exacerbate breast cancer disease in patients. The difficulty in conducting definitive human studies can be overcome by investigating developing breast cancer in a mouse model. In this study, we utilized mice latently infected with murine gammaherpesvirus 68 (HV-68) to question whether such a viral burden could exacerbate metastatic breast cancer disease using a mouse mammary tumor model.

Results

Mice latently infected with HV-68 had a similar primary tumor burden, but much greater metastatic disease, when compared to mock treated mice given the transplantable tumor, 4 T1. This was true for lung lesions, as well as secondary tumor masses. Increased expression of pan-cytokeratin and VEGF-A in tumors from HV-68 infected mice was consistent with increased metastatic disease in these animals. Surprisingly, no viral particles could be cultured from tumor tissues, and the presence of viral DNA or RNA transcripts could not be detected in primary or secondary tumor tissues.

Conclusions

Latent HV-68 infection had no significant effect on the size of primary 4 T1 mammary tumors, but exacerbated the number of metastatic lung lesions and secondary tumors when compared to mock treated mice. Increased expression of the tumor marker, pan-cytokeratin, and VEGF-A in tumors of mice harboring latent virus was consistent with an exacerbated metastatic disease. Mechanisms responsible for this exacerbation are indirect, since no virus could be detected in cancerous tissues.

Epstein-Barr virus infection and sporadic breast cancer risk: a meta-analysis

Background

A large number of epidemiological studies have evaluated the association between Epstein-Barr virus infection and breast carcinoma risk but results have been inconsistent.

Methodology

Research using the polymerase chain reaction technique for detecting the Epstein-Barr virus was selected; 24 studies and 1535 cases were reviewed. Information on the study populations, sample types, publication calendar period and histological types of breast carcinoma were collected. An unconditional logistic regression model was used to analyze potential parameters related to the Epstein-Barr virus prevalence. A Kappa test was used to evaluate the consistency in detecting different Epstein-Barr virus DNA regions. Nine studies that included control groups and 1045 breast cancer cases were adopted in this meta-analysis.

Conclusions

We found that 29.32% of the patients with breast carcinoma were infected with the Epstein-Barr virus. The prevalence of Epstein-Barr was highest in Asia (35.25%) and lowest in the USA (18.27%). Statistical analysis revealed a trend that showed lobular breast carcinoma might have the strongest association with Epstein-Barr virus infection. This meta-analysis showed a significant increase in breast malignancy risk in patients testing positive for the Epstein-Barr virus (OR = 6.29, 95% CI = 2.13–18.59). This result suggests that an Epstein-Barr virus infection is statistically associated with increased breast carcinoma risk.

No evidence for the involvement of XMRV or MCV in the pathogenesis of breast cancer

Background:

The aetiology of breast cancer remains elusive. A viral aetiology has been proposed, but to date no virus has been conclusively demonstrated to be involved. Recently, two new viruses, namely Merkel cell polyomavirus (MCV) and xenotropic murine leukaemia virus-related virus (XMRV) have been identified and implicated in the pathogenesis of Merkel cell carcinoma (MCC) and familial form of prostate cancer, respectively.

Methods:

We examined 204 samples from 58 different cases of breast cancer for presence of MCV or XMRV by PCR. Samples consisted of both malignant and non-malignant tissues. Additionally, we included 6 cases of MCC and 12 cases of prostate cancer as potential controls for MCV and XMRV, respectively.

Results:

All of the breast cancer samples examined were negative for both MCV and XMRV. However, 4/6 MCC and 2/12 prostate cancer samples were found to be positive for MCV and XMRV, respectively. Sequence analysis of the amplified products confirmed that these sequences belonged to MCV and XMRV.

Conclusion:

We conclude that there is no evidence for the involvement of MCV or XMRV in the pathogenesis of breast cancer. What role these viruses have in the pathogenesis of MCC and prostate carcinomas remains to be demonstrated.

Joint effects of Epstein-Barr virus and polymorphisms in interleukin-10 and interferon-γ on breast cancer risk

BACKGROUND

The relationship between Epstein-Barr virus (EBV) and breast cancer (BC) is controversial. Interleukin-10 (IL-10) and interferon-γ (IFN-γ) are believed to play a critical role in the host's responses to EBV infection, and their genetic variations may modify the association of EBV with BC risk.

METHODS

We examined serum levels of EBV viral capsid antigen (VCA) immunoglobulin A (IgA) and nuclear antigen-1 (EBNA-1) IgA along with the polymorphisms of IL-10 rs1800871 and IFN-γ rs2069705 in 354 incident BC cases and 504 age-matched controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using multivariate logistic regression.

RESULTS

VCA IgA and EBNA-1 IgA levels were positively associated with BC risk. IL-10 rs1800871 (TC/CC) was associated with a reduced BC risk (OR, 0.74 [95% CI, 0.55-1.00]) but had no interaction with EBV infection on BC risk. IFN-γ rs2069705 was not directly associated with BC risk but interacted with EBNA-1 IgA on BC risk. Among women with the CC genotype, EBNA-1 IgA seropositivity significantly increased the risk of BC compared to EBNA-1 IgA seronegativity (OR, 5.14 [95% CI, 1.76-14.98]).

CONCLUSIONS

These results suggest that EBV may contribute to the risk of BC and that this contribution may be modified by genetic variations in IFN-γ.

Epstein-Barr virus and breast cancer: serological study in a high-incidence area of nasopharyngeal carcinoma

We investigated IgA and IgG levels against EBV viral capsid antigen (VCA) and nuclear antigen-1 (EBNA-1) in serum of 223 women with breast cancer (BC) and 309 controls in Guangzhou, China. VCA IgA levels were significantly associated with an elevated risk of BC, with adjusted ORs (95%CIs) of 1.70 (1.05-2.76) (seropositivity) and 2.21 (1.11-4.40) (unit increases in OD value). This association was stronger among young, lean, and HER2+ women. The EBNA-1 IgA levels in OD value, but not seropositivity, were associated with an increased risk of BC among ER+, PR+, and HER2+ patients. None of the IgG variables was related to BC. These results suggest the EBV association with BC in an endemic area of nasopharyngeal carcinoma.

Social support and socioeconomic status interact to predict Epstein-Barr virus latency in women awaiting diagnosis or newly diagnosed with breast cancer

OBJECTIVE

Both higher socioeconomic status (SES) and supportive personal relationships confer health benefits, including better immune function. This study assessed the joint impact of SES and social support on the expression of a latent herpesvirus, Epstein-Barr virus (EBV), in a group of highly stressed women.

METHODS

Two-hundred and twenty four women either awaiting further evaluation following an abnormal mammogram or newly diagnosed with breast cancer completed questionnaires and provided blood samples to assess EBV viral capsid antigen (VCA) IgG antibody titers.

RESULTS

More highly educated women with more support from friends had lower EBV VCA antibody titers, reflecting a stronger cellular immune response to the latent virus; however, among less educated women, friend support was not associated with EBV antibody titers. As revealed in an ancillary analysis, more highly educated women with more friend support had lower systolic blood pressure (SBP); however, friend support was not associated with SBP among less educated women. Neither depression nor perceived stress mediated these associations. Neither cancer status nor cancer stage among those diagnosed with cancer was significantly related to these outcomes.

CONCLUSION

Lower SES women may not reap the same immunological benefits from friend support when experiencing a stressful life event as their higher SES counterparts.

Localization of Epstein-Barr virus to infiltrating lymphocytes in breast carcinomas and not malignant cells

The pathogenesis of breast cancer is unknown. In recent years, a number of studies have implicated a role for Epstein-Barr virus (EBV) in a subset of cases. However, these findings are controversial and others have failed to find any link between the virus and this malignancy. We hypothesized that technical differences and the different type and ethnic origin of the cases may be the cause of the disparities reported. Using a highly sensitive EBER-in situ hybridization and immunohistochemistry, we examined 219 samples (158 malignant and 61 non-malignant) from 61 Emirati breast cancer cases to determine if EBV was etiologically associated with Emirati cases and if there was any correlation with other established prognostic factors such as age, histological type, lymph node metastasis, estrogen, progesterone and HER2 expression. We found 47.5% of the cases to be EBV positive, but the virus was localized to occasional infiltrating lymphocytes and not in the malignant cells. EBV lymphocytes were more commonly observed in lymph nodes than in breast tissues, but there was no correlation with malignancy or hormone status. The mean age of our patients was 48years and hormone receptor staining revealed 20% of the cases to be triple negative (ER-/PR-/HER2-). We conclude that although EBV can be detected in breast cancer cases, it is not directly associated with the disease. Thus, a PCR-based approach cannot be used to link this ubiquitous virus to the pathogenesis of breast cancer. Furthermore, we do not find any correlation between the presence of EBV in infiltrating lymphocytes and ER, PR, HER2 expression. We believe our findings will help explain some of the controversies relating to the role of EBV in the pathogenesis of breast cancer.

Association between Epstein-Barr virus infection and risk for development of pregnancy-associated breast cancer: joint effect with vitamin D?

BACKGROUND

Few studies have evaluated the role of the ubiquitous Epstein-Barr virus (EBV) infection, together with levels of the immunomodulator, vitamin D, in different breast cancer entities. We studied, prospectively, the association of EBV and vitamin D status with the risk of pregnancy-associated breast cancer (PABC), breast cancer diagnosed during pregnancy or 1 year post-partum, using a nested case-control study.

METHODS

Serum vitamin D and antibodies to EBV were measured for 108 PABC cases of the Finnish Maternity Cohort, and 208 controls matched for date of birth, date of sampling and parity. The joint effect of vitamin D and EBV on the risk of PABC was evaluated.

RESULTS

EBV seropositivity was generally not associated with the risk of PABC. Among individuals with sufficient (≥75 nmol/l) levels of vitamin D, we, however, found similar increased risk estimates for PABC associated with serum immunoglobulin G (IgG) antibodies to EBV early antigens [odds ratio (OR)=7.7, 95% (confidence interval) CI 1.4-42.3] and the viral reactivator protein, ZEBRA (OR=7.8, 95% CI 1.1-61.2).

CONCLUSION

Immunological markers of EBV reactivation status among individuals with sufficient vitamin D levels were consistently associated with increased risk of the disease. This suggests that EBV reactivation may be an indicator of the progression of breast cancer occurring soon after pregnancy, while the virus probably is not the aetiological agent.

Epstein-Barr virus as a marker of biological aggressiveness in breast cancer

Purpose:

Although a potential role of the Epstein-Barr virus (EBV) in the pathogenesis of breast cancer (BC) has been underlined, results remain conflicting. Particularly, the impact of EBV infection on biological markers of BC has received little investigation.

Methods:

In this study, we established the frequency of EBV-infected BC using real-time quantitative PCR (RT–PCR) in 196 BC specimens. Biological and pathological characteristics according to EBV status were evaluated.

Results:

EBV DNA was present in 65 of the 196 (33.2%) cases studied. EBV-positive BCs tended to be tumours with a more aggressive phenotype, more frequently oestrogen receptor negative (P=0.05) and with high histological grade (P=0.01). Overexpression of thymidine kinase activity was higher in EBV-infected BC (P=0.007). The presence of EBV was weakly associated with HER2 gene amplification (P=0.08).

Conclusion:

Our study provides evidence for EBV-associated BC undergoing distinct carcinogenic processes, with more aggressive features.