Revisiting a role for a mammary tumor retrovirus in human breast cancer

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.

Decoding the mystery of MMTV-like virus and its relationship with breast cancer metastasis

BACKGROUND

MMTV causes mammary tumors in mice, and it is associated with invasive and aggressive forms of breast cancer in humans. However, the underlying mechanisms are yet unknown. We aimed to determine the MMTV-like virus (MMTV-LV) association with histological types of breast cancer, nodal involvement, and metastasis.

METHODS

First, 105 breast cancer biopsies and 15 disease-free biopsies were collected. Details of clinicopathological characteristics were retrieved from patients' records. The status of MMTV-LV was already known for these biopsy samples. Associations of MMTV-LV prevalence with LNM status and metastatic history were determined. Next, quantitative PCR (qPCR) was used to quantify env gene mRNA in biopsies positive for MMTV-LV. Expression of the env gene was compared against different histopathological types of mammary tumor, LNM status, and metastasis by performing Ordinary One Way ANOVA followed by Tukey's multiple comparisons test.

RESULTS

MMTV-LV prevalence was found to have no significant association with LNM or metastatic history. As compared to normal control, expression of the env gene was significantly higher (>2.8 folds) in invasive samples (P-value: < 0.01). Expression was also higher (3.28 and 2.89 folds) in patient samples with LNM (P-value: 0.0006) or metastatic history (P-value: < 0.0001), respectively.

CONCLUSION

We conclude that MMTV-LV prevalence is not associated with LNM status or breast cancer metastasis; samples with invasive phenotypes, nodal involvement, and metastasis exhibit significantly higher expression of the MMTV-like env gene.

The Role of a Betaretrovirus in Human Breast Cancer: Enveloping a Conundrum

Most of the evidence that a human betaretrovirus (HBRV/HMTV) highly related to mouse mammary tumour virus (MMTV) has an etiological role in breast cancer has been summarized in a recent comprehensive Special Issue of "Viruses" entitled "Human Betaretrovirus (HBRV) and Related Diseases". Shortly after publication of this special issue, a detailed analysis of aligned env sequences was published and concluded that (i) MMTV and HBRV/HMTV cannot be distinguished on the basis of aligned env sequences and (ii) more sequence data covering the full-length env or HBRV/HMTV genomes from multiple isolates is needed. Although productive infection of human cells by MMTV (and presumably HBRV/HMTV) has been shown, it is imperative that the receptor(s) enabling HBRV/HMTV to infect human cells are defined. Moreover, there is currently no compelling data for common integration sites, in contrast to MMTV induced mammary tumorigenesis in mice, suggesting that other mechanisms of tumorigenesis are associated with HBRV/HMTV infection. These issues need to be resolved before a clear link between MMTV/HBRV/HMTV and human breast cancer can be concluded.

The Viral Origin of Human Breast Cancer: From the Mouse Mammary Tumor Virus (MMTV) to the Human Betaretrovirus (HBRV)

A Human Betaretrovirus (HBRV) has been identified in humans, dating as far back as about 4500 years ago, with a high probability of it being acquired by our species around 10,000 years ago, following a species jump from mice to humans. HBRV is the human homolog of the MMTV (mouse mammary tumor virus), which is the etiological agent of murine mammary tumors. The hypothesis of a HMTV (human mammary tumor virus) was proposed about 50 years ago, and has acquired a solid scientific basis during the last 30 years, with the demonstration of a robust link with breast cancer and with PBC, primary biliary cholangitis. This article summarizes most of what is known about MMTV/HMTV/HBRV since the discovery of MMTV at the beginning of last century, to make evident both the quantity and the quality of the research supporting the existence of HBRV and its pathogenic role. Here, it is sufficient to mention that scientific evidence includes that viral sequences have been identified in breast-cancer samples in a worldwide distribution, that the complete proviral genome has been cloned from breast cancer and patients with PBC, and that saliva contains HBRV, as a possible route of inter-human infection. Controversies that have arisen concerning results obtained from human tissues, many of them outdated by new scientific evidence, are critically discussed and confuted.

Mouse Mammary Tumor Virus (MMTV) and MMTV-like Viruses: An In-depth Look at a Controversial Issue

Since its discovery as a milk factor, mouse mammary tumor virus (MMTV) has been shown to cause mammary carcinoma and lymphoma in mice. MMTV infection depends upon a viral superantigen (sag)-induced immune response and exploits the immune system to establish infection in mammary epithelial cells when they actively divide. Simultaneously, it avoids immune responses, causing tumors through insertional mutagenesis and clonal expansion. Early studies identified antigens and sequences belonging to a virus homologous to MMTV in human samples. Several pieces of evidence fulfill a criterion for a possible causal role for the MMTV-like virus in human breast cancer (BC), though the controversy about whether this virus was linked to BC has raged for over 40 years in the literature. In this review, the most important issues related to MMTV, from its discovery to the present days, are retraced to fully explore such a controversial issue. Furthermore, the hypothesis of an MMTV-like virus raised the question of a potential zoonotic mouse–man transmission. Several studies investigate the role of an MMTV-like virus in companion animals, suggesting their possible role as mediators. Finally, the possibility of an MMTV-like virus as a cause of human BC opens a new era for prevention and therapy.

Pathological Features and Molecular Phenotype of MMTV Like-Positive Feline Mammary Carcinomas

Simple Summary

Mouse mammary tumour virus-like (MMTV-like) is suspected to be involved in human breast cancer and feline mammary carcinomas (FMCs). We previously reported the identification of MMTV-like sequences and viral protein in six of 78 FMCs collected in Tuscany, Italy. To corroborate this finding, FMCs samples collected from a different geographic area were investigated. MMTV-like sequences and p14 protein were identified in three of 24 FMCs collected at the University of Bologna, one tubular carcinoma, one tubulopapillary carcinoma and one ductal carcinoma. All the examined FMCs from Pisa and Bologna were submitted to immunohistochemistry for molecular phenotype characterization. Of the nine positive FMCs, six were basal-like and three luminal-like. This study highlights the presence of MMTV-like sequences and protein in FMCs of different geographic areas. The characterization of molecular phenotype could contribute to understand the possible role of MMTV-like virus in FMC biological behaviour.

Abstract

In the last few years MMTV-like nucleotide sequences were detected in some feline and canine mammary tumours. Due to the confirmed role of cats in the epidemiology of the MMTV-like virus, the aim of this study was to investigate the main pathological features of positive feline mammary carcinomas (FMCs). Twenty-four FMCs were collected at the University of Bologna, submitted to laser microdissection and analysed by nested fluorescence-PCR using primer sets specific for MMTV env sequence. For immunohistochemistry, an antibody against MMTV protein 14 (p14) was used. MMTV-like sequences were detected in three out of 24 FMCs (12.5%), one tubular carcinoma, one tubulopapillary carcinoma and one ductal carcinoma. All PCR-positive tumours were also positive for p14. Multiple nucleotide alignment has shown similarity to MMTV ranging from 98% to 100%. All the 102 examined FMCs were submitted to immunohistochemistry for molecular phenotyping. Of the nine MMTV-like positive FMCs, six were basal-like and three luminal-like. Our results demonstrate MMTV-like sequences and protein in FMCs of different geographic areas. Molecular phenotyping could contribute to understand the possible role of MMTV-like virus in FMC tumor biology.

Evaluating the expression level of HERV-K env, np9, rec and gag in breast tissue

OBJECTIVE

Breast cancer is one of the most common health problems. It has been suggested that several risk factors, either considered as external or internal, play a critical role in the pathogenesis of breast cancer, which among them, HERV-k, has the most fundamental role. In the present study, we aimed to evaluate the role of HERV-k env, gag, rec, np9 expressions in breast cancer progression.

MATERIALS AND METHODS

We collected 40 breast cancer tissues and their normal adjacent ones. After extracting the RNA of breast samples, we evaluated the expression of HERV-k env, gag, rec, np9 by using Quantitative real-time PCR (qRT-PCR).

RESULTS

The resulting data revealed that while there was a meaningful increase in the expression level of HERV-k env, gag and np9 in breast cancer tissues (P ≤ 0.01, 0.05, 0.05, respectively), we failed to find any significant elevation in the expression level of rec mRNA level.

CONCLUSION

The results of our study suggested that there is a plausible correlation between the mRNA expression level of HERV-K env, gag and np9 and the progression of breast cancer, proposing these markers as promising biomarkers to diagnose breast cancer.

Mouse mammary tumor virus (MMTV) - like exogenous sequences are associated with sporadic but not hereditary human breast carcinoma

The inheritance of mutated suppressor genes, such as BRCA1 and BRCA2, is acknowledged as an etiological factor in hereditary breast carcinoma (HBC). Two different molecular mechanisms are possible; the Knudson's "two hits" or the gene haploinsufficiency. Etiology of sporadic breast carcinoma (SBC) is not known, although data support the possible role of the betaretrovirus Mouse Mammary Tumor Virus (MMTV). This study analyzes the presence of MMTV exogenous sequences in two representative groups of HBC and SBC, excluding any contamination by murine and retroviral material and endogenous betaretroviruses. The 30.3% of 56 SBC contained MMTV sequences, against the 4.2% of 47 HBC (p < 0.001). Cases positive for viral sequences showed the presence of p14, signal peptide of the MMTV envelope precursor. This result was expected based on the fact that HBCs, having a specific genetic etiology, do not need the action of a carcinogenetic viral agent. Moreover, the striking results obtained by comparing two groups of vastly different tumors represent an additional element of quality control: the distinction between HBC and SBC is so well-defined that results cannot be ascribed to mere coincidence. This paper strengthens the hypothesis for a viral etiology for human sporadic breast carcinoma.

Bovine leukemia virus DNA associated with breast cancer in women from South Brazil

Breast cancer is a neoplastic condition with a high morbidity and mortality amongst women worldwide. Recent data linking bovine leukemia virus (BLV) with breast cancer has been contested already. Our study investigated the presence of BLV genome in healthy (n = 72) and cancerous (n = 72) paraffin-embedded samples of breast tissues from women in south Brazil. BLV DNA was found most frequently (30.5%) in breast cancer tissue than in healthy breast (13.9%) (Odds ratio = 2.73; confidence interval = 1.18-6.29; p = 0.027). In contrast, antibodies to BLV were found in a very small percentage of healthy blood donors. There was no association between BLV DNA and other tumor prognostic biological markers such as hormonal receptors, HER2 oncoprotein, proliferation index, metastasis in sentinels lymph nodes, and tumor grade and size. Our findings suggest that BLV should be considered a potential predisposing factor to breast cancer in women.

Tumour virology in the era of high-throughput genomics

With the advent of massively parallel sequencing, oncogenic viruses in tumours can now be detected in an unbiased and comprehensive manner. Additionally, new viruses or strains can be discovered based on sequence similarity with known viruses. Using this approach, the causative agent for Merkel cell carcinoma was identified. Subsequent studies using data from large collections of tumours have confirmed models built during decades of hypothesis-driven and low-throughput research, and a more detailed and comprehensive description of virus-tumour associations have emerged. Notably, large cohorts and high sequencing depth, in combination with newly developed bioinformatical techniques, have made it possible to rule out several suggested virus-tumour associations with a high degree of confidence. In this review we discuss possibilities, limitations and insights gained from using massively parallel sequencing to characterize tumours with viral content, with emphasis on detection of viral sequences and genomic integration events.This article is part of the themed issue 'Human oncogenic viruses'.

A new immunization and treatment strategy for mouse mammary tumor virus (MMTV) associated cancers

Mouse Mammary Tumor Virus (MMTV) causes mammary carcinoma or lymphoma in mice. An increasing body of evidence in recent years supports its involvement also in human sporadic breast cancer. It is thus of importance to develop new strategies to impair the development, growth and metastasis of MMTV-associated cancers. The signal peptide of the envelope precursor protein of this virus: MMTV-p14 (p14) is an excellent target for such strategies, due to unique characteristics distinct from its regular endoplasmic reticulum targeting function. These include cell surface expression in: murine cancer cells that harbor the virus, human breast cancer (MCF-7) cells that ectopically express p14, as well as cultured human cells derived from an invasive ductal breast carcinoma positive for MMTV sequences. These findings support its use in signal peptide-based immune targeting. Indeed, priming and boosting mice with p14 elicits a specific anti-signal peptide immune response sufficient for protective vaccination against MMTV-associated tumors. Furthermore, passive immunization using a combination of anti-p14 monoclonal antibodies or the transfer of T-cells from immunized mice (Adoptive Cell Transfer) is also therapeutically effective. With reports demonstrating involvement of MMTV in human breast cancer, we propose the immune-mediated targeting of p14 as a strategy for prevention, treatment and diagnosis of MMTV-associated cancers.

Comparative aspects of canine and human inflammatory breast cancer

Inflammatory breast cancer (IBC) in humans is the most aggressive form of mammary gland cancer and shares clinical, pathologic, and molecular patterns of disease with canine inflammatory mammary carcinoma (CIMC). Despite the use of multimodal therapeutic approaches, including targeted therapies, the prognosis for IBC/CIMC remains poor. The aim of this review is to critically analyze IBC and CIMC in terms of biology and clinical features. While rodent cancer models have formed the basis of our understanding of cancer biology, the translation of this knowledge into improved outcomes has been limited. However, it is possible that a comparative "one health" approach to research, using a natural canine model of the disease, may help advance our knowledge on the biology of the disease. This will translate into better clinical outcomes for both species. We propose that CIMC has the potential to be a useful model for developing and testing novel therapies for IBC. Further, this strategy could significantly improve and accelerate the design and establishment of new clinical trials to identify novel and improved therapies for this devastating disease in a more predictable way.

Bovine leukemia virus linked to breast cancer but not coinfection with human papillomavirus: Case-control study of women in Texas

BACKGROUND

Bovine leukemia virus (BLV) and human papillomavirus (HPV) were previously identified in human breast tissue and have been associated with breast cancer in independent studies. The objective of the current study was to test for the presence of BLV and HPV in the same breast tissue specimens to determine whether the viruses were associated with breast cancer either singly or together.

METHODS

Archival formalin-fixed paraffin-embedded breast tissue sections from 216 women were received from The University of Texas MD Anderson Cancer Center along with patient diagnosis. In situ polymerase chain reaction and/or DNA hybridization methods were used to detect targeted DNA segments of BLV and HPV. Standard statistical methods were used to calculate age-adjusted odds ratios, attributable risk, and P values for the trend related to the association between presence of a virus and a diagnosis of breast disease.

RESULTS

Women diagnosed with breast cancer were significantly more likely to have BLV DNA in their breast tissue compared with women with benign diagnoses and no history of breast cancer. Women with breast pathology classified as premalignant and no history of breast cancer also were found to have an elevated risk of harboring BLV DNA in their breast tissue. HPV status was not associated with malignancy, premalignant breast disease, or the presence of BLV in the breast tissues.

CONCLUSIONS

The data from the current study supported previous findings of a significant association between BLV DNA in breast tissue and a diagnosis of breast cancer, but did not demonstrate oncogenic strains of HPV associated with breast cancer or the presence of BLV DNA in breast tissue. The authors believe the findings of the current study contribute to overall knowledge regarding a possible causal role for viruses in human breast cancer. Cancer 2018;124:1342-9. © 2017 American Cancer Society.

Detection of oncogenic viruses in water environments by a Luminex-based multiplex platform for high throughput screening of infectious agents

Recent studies documented the detection of viruses strongly associated with human cancer in urban sewages and other water environments worldwide. The aim of this study was to estimate the occurrence of human oncogenic viruses in environmental samples (sewage, river, marine, and pool/spa water) using highly sensitive and specific multiplex bead-based assays (Luminex technology). A total of 33 samples were analysed for 140 oncogenic viral agents, including mucosal and cutaneous human papillomaviruses (HPVs), human polyomaviruses (HPyV), human herpesviruses (HHV) and mouse mammary tumour virus (MMTV). Eighty-eight percent of the samples tested positive for at least one viral pathogen and the simultaneous presence of more than one virus was frequent (mean number of positivities/sample = 3.03). A total of 30 different Alpha, Beta and Gamma HPVs were detected, including mucosal and cutaneous types. The high-risk type HPV16 was the most frequently detected virus, identified in 73% of the samples. Of the 12 HPyVs tested, only two (BKPyV and MCPyV) were detected. At least one of these two was present in 48% of the samples. MMTV was detected in 21% of the samples, while herpesviruses - HHV-6 and HHV-1 - were detected in two samples (6%). The present study is the first to provide a comprehensive picture of the occurrence of oncogenic viruses belonging to different families and species in diverse water environments, and the first to successfully use, in environmental samples, a Luminex-based multiplex platform for high throughput screening of infectious agents. Our findings, showing that oncogenic viruses are ubiquitous in water environments, pave the way for future studies on the fate of these pathogens in water environments as well as on their potential for transmission via the waterborne route.

Is MMTV associated with human breast cancer? Maybe, but probably not

BACKGROUND

Conflicting results regarding the association of MMTV with human breast cancer have been reported. Published sequence data have indicated unique MMTV strains in some human samples. However, concerns regarding contamination as a cause of false positive results have persisted.

METHODS

We performed PCR assays for MMTV on human breast cancer cell lines and fresh frozen and formalin fixed normal and malignant human breast epithelial samples. Assays were also performed on peripheral blood mononuclear cells from volunteer blood donors and subjects at risk for human retroviral infections. In addition, assays were performed on DNA samples from wild and laboratory mice. Sequencing of MMTV positive samples from both humans and mice were performed and phylogenetically compared.

RESULTS

Using PCR under rigorous conditions to prevent and detect "carryover" contamination, we did detect MMTV DNA in human samples, including breast cancer. However, the results were not consistent and seemed to be an artifact. Further, experiments indicated that the probable source of false positives was murine DNA, containing endogenous MMTV, present in our building. However, comparison of published and, herein, newly described MMTV sequences with published data, indicates that there are some very unique human MMTV sequences in the literature.

CONCLUSION

While we could not confirm the true presence of MMTV in our human breast cancer subjects, the data indicate that further, perhaps more traditional, retroviral studies are warranted to ascertain whether MMTV might rarely be the cause of human breast cancer.

Breast Cancer and HIV in Sub-Saharan Africa: A Complex Relationship

Introduction

The number and lifespan of individuals living with HIV have increased significantly with the scale-up of antiretroviral therapy. Furthermore, the incidence of breast cancer in women with HIV is growing, especially in sub-Saharan Africa (SSA). However, the association between HIV infection and breast cancer is not well understood.

Methods

A literature search was performed to identify articles published in journals pertaining to breast cancer and HIV, with an emphasis on SSA. Selected US-based studies were also identified for comparison.

Results

Among the 56 studies reviewed, the largest study examined 314 patients with breast cancer and HIV in the United States. There is no consensus on whether HIV infection acts as a pro-oncogenic or antioncogenic factor in breast cancer, and it may have no relation to breast cancer. A higher incidence of breast cancer is reported in high-income countries than in SSA, although breast cancer in SSA presents at a younger age and at a more advanced stage. Some studies show that patients with breast cancer and HIV experience worse chemotherapy toxicity than do patients without HIV. Data on treatment outcomes are limited. The largest study showed worse treatment outcomes in patients with HIV, compared with their counterparts without HIV.

Conclusion

HIV infection has not been associated with different clinical presentation of breast cancer. However, some evidence suggests that concurrent diagnosis of HIV with breast cancer is associated with increased therapy-related toxicity and worse outcomes. Systematic prospective studies are needed to establish whether there is a specific association between breast cancer and HIV.

Polypyrimidine tract-binding protein binds to the 5' untranslated region of the mouse mammary tumor virus mRNA and stimulates cap-independent translation initiation

The 5' untranslated region (UTR) of the full-length mRNA of the mouse mammary tumor virus (MMTV) harbors an internal ribosomal entry site (IRES). In this study, we show that the polypyrimidine tract-binding protein (PTB), an RNA-binding protein with four RNA recognition motifs (RRMs), binds to the MMTV 5' UTR stimulating its IRES activity. There are three isoforms of PTB: PTB1, PTB2, and PTB4. Results show that PTB1 and PTB4, but not PTB2, stimulate MMTV-IRES activity. PTB1 promotes MMTV-IRES-mediated initiation more strongly than PTB4. When expressed in combination, PTB1 further enhanced PTB4 stimulation of the MMTV-IRES, while PTB2 fully abrogates PTB4-induced stimulation. PTB1-induced stimulation of MMTV-IRES was not altered in the presence of PTB4 or PTB2. Mutational analysis reveals that stimulation of MMTV-IRES activity is abrogated when PTB1 is mutated either in RRM1/RRM2 or RRM3/RRM4. In contrast, a PTB4 RRM1/RRM2 mutant has reduced effect over MMTV-IRES activity, while stimulation of the MMTV-IRES activity is still observed when the PTB4 RRM3/RMM4 mutant is used. Therefore, PTB1 and PTB4 differentially stimulate the IRES activity. In contrast, PTB2 acts as a negative modulator of PTB4-induced stimulation of MMTV-IRES. We conclude that PTB1 and PTB4 act as IRES trans-acting factors of the MMTV-IRES.

Exposure to Bovine Leukemia Virus Is Associated with Breast Cancer: A Case-Control Study

BACKGROUND

Age, reproductive history, hormones, genetics, and lifestyle are known risk factors for breast cancer, but the agents that initiate cellular changes from normal to malignant are not understood. We previously detected bovine leukemia virus (BLV), a common oncogenic virus of cattle, in the breast epithelium of humans. The objective of this study was to determine whether the presence of BLV DNA in human mammary epithelium is associated with breast cancer.

METHODS

This was a case-control study of archival formalin fixed paraffin embedded breast tissues from 239 donors, received 2002-2008 from the Cooperative Human Tissue Network. Case definition as breast cancer versus normal (women with no history of breast cancer) was established through medical records and examination of tissues by an anatomical pathologist. Breast exposure to BLV was determined by in situ-PCR detection of a biomarker, BLV DNA, localized within mammary epithelium.

RESULTS

The frequency of BLV DNA in mammary epithelium from women with breast cancer (59%) was significantly higher than in normal controls (29%) (multiply- adjusted odds ratio = 3.07, confidence interval = 1.66-5.69, p = .0004, attributable risk = 37%). In women with premalignant breast changes the frequency of BLV DNA was intermediate (38%) between that of women with breast cancer and normal controls (p for trend < .001).

CONCLUSIONS

Among the specimens in this study, the presence of amplified BLV DNA was significantly associated with breast cancer. The odds ratio magnitude was comparable to those of well-established breast cancer risk factors related to reproductive history, hormones, and lifestyle and was exceeded only by risk factors related to genetics (familial breast cancer), high dose ionizing radiation, and age. These findings have the potential for primary and secondary prevention of breast cancer.

No significant viral transcription detected in whole breast cancer transcriptomes

Background

Studies evaluating the presence of viral sequences in breast cancer (BC), including various strains of human papillomavirus and human herpes virus, have yielded conflicting results. Most were based on RT-PCR and in situ hybridization.

Methods

In this report we searched for expressed viral sequences in 58 BC transcriptomes using five distinct in silico methods. In addition, we complemented our RNA sequencing results with exome sequencing, PCR and immunohistochemistry (IHC) analyses. A control sample was used to test our in silico methods.

Results

All of the computational methods correctly detected viral sequences in the control sample. We identified a small number of viral sequences belonging to human herpesvirus 4 and 6 and Merkel cell polyomavirus. The extremely low expression levels—two orders of magnitude lower than in a typical hepatitis B virus infection in hepatocellular carcinoma—did not suggest active infections. The presence of viral elements was confirmed in sample-matched exome sequences, but could not be confirmed by PCR or IHC.

Conclusions

Our results show that no viral sequences are expressed in significant amounts in the BC investigated. The presence of non-transcribed viral DNA cannot be excluded.

Detection of MMTV-Like sequences in Moroccan breast cancer cases

Introduction

The mouse mammary tumor virus (MMTV) like sequences have been reported to be present in some human breast cancers, but their association with breast cancer development is still controversial.

Methods

In this retrospective study, we investigated the status of MMTV-like in 42 tumor biopsies and 18 paired normal tissues from Moroccan patients with breast cancer. MMTV-like env sequences were identified by PCR and confirmed by direct DNA sequencing.

Results

Specific MMTV-like env sequences were found in 24 (57.14%) cases of breast carcinomas, and 6 (33.3%) cases of matched normal breast tissues. Comparison to sociologic and clinicopathological parameters showed no significant association between the presence of MMTV-like sequences and age, menopausal status, histological subtype, histological grade, tumor size and the expression of hormone receptors (estrogen ER and/or progesterone PgR) and Her 2. However, a significant correlation was found between MMTV-like presence and parity (p = 0.024).

Conclusions

This present study confirms the presence of MMTV-like env sequences in breast cancer in Moroccan women, prompting further evaluation, on large sampling, to elucidate the probable causal roles of MMTV-like in breast cancer development.

Synchronous ipsilateral carcinoma of the accessory mammary gland and primary lymphoma of the breast with subsequent rectal carcinoma: report of a case

A case of synchronous carcinoma of the accessory mammary gland and primary breast lymphoma with subsequent rectal carcinoma has not been reported previously. We present a very rare case of primary non-Hodgkin lymphoma of the left breast diagnosed simultaneously with invasive lobular carcinoma of the left axillary accessory mammary gland and rectal adenocarcinoma. An 82-year-old Japanese woman presented with two palpable masses on the left chest wall. She was given a diagnosis of suspected breast malignant tumor and axillary accessory mammary gland. She underwent excision of the axillary accessory mammary gland and left mastectomy with axillary lymph node dissection. Histopathological examination revealed diffuse large B-cell lymphoma of the breast and invasive lobular carcinoma of the axillary accessory mammary gland with lymph nodes metastasis. Three months after the surgery, primary rectal adenocarcinoma was also detected by F-18 fluorodeoxyglucose positron emission tomography. Hartmann’s operation was performed, since which time the patient has been doing well.

Recent developments linking retroviruses to human breast cancer: infectious agent, enemy within or both?

Evidence is accumulating that one or more beta-retrovirus is associated with human breast cancer. Retroviruses can exist as an infectious (exogenous) virus or as a part of the genetic information of cells due to germline integration (endogenous). An exogenous virus with a genome that is highly homologous to mouse mammary tumour virus is gaining acceptance as possibly being associated with human breast cancer, and recently furnished evidence is discussed in this article, as is the evidence for involvement of an endogenous human beta-retrovirus, HERV-K. Modes of interaction are also reviewed and linkages to the APOBEC3 family are suggested.

Joint infectious causation of human cancers

Joint infectious causation of cancer has been accepted in a few well-studied instances, including Burkitt's lymphoma and liver cancer. In general, evidence for the involvement of parasitic agents in oncogenesis has expanded, and recent advances in the application of molecular techniques have revealed specific mechanisms by which host cells are transformed. Many parasites evolve to circumvent immune-mediated detection and destruction and to control critical aspects of host cell reproduction and survival: cell proliferation, apoptosis, adhesion, and immortalization. The host has evolved tight regulation of these cellular processes-the control of each represents a barrier to cancer. These barriers need to be compromised for oncogenesis to occur. The abrogation of a barrier is therefore referred to as an essential cause of cancer. Alternatively, some aspects of cellular regulation restrain but do not block oncogenesis. Relaxation of a restraint is therefore referred to as an exacerbating cause of cancer. In this chapter, we explore past and current evidence for joint infectious causation of cancer in the context of essential and exacerbating causes. We stress that discovery of joint infectious causation may provide great improvements in controlling cancer, particularly through the identification of many additional nonhuman targets for synergistic interventions for prevention and treatment.