Epstein-Barr Virus (EBV) Genome and Expression in Breast Cancer Tissue: Effect of EBV Infection of Breast Cancer Cells on Resistance to Paclitaxel (Taxol)

Abstract

The Epstein-Barr virus (EBV) has been detected in subsets of breast cancers. In order to elaborate on these observations, we quantified by real-time PCR (Q-PCR) the EBV genome in biopsy specimens of breast cancer tissue as well as in tumor cells isolated by microdissection. Our findings show that EBV genomes can be detected by Q-PCR in about half of tumor specimens, usually in low copy numbers. However, we also found that the viral load is highly variable from tumor to tumor. Moreover, EBV genomes are heterogeneously distributed in morphologically identical tumor cells, with some clusters of isolated tumor cells containing relatively high genome numbers while other tumor cells isolated from the same specimen may be negative for EBV DNA. Using reverse transcription-PCR, we detected EBV gene transcripts: EBNA-1 in almost all of the EBV-positive tumors and RNA of the EBV oncoprotein LMP-1 in a smaller subset of the tissues analyzed. Moreover, BARF-1 RNA was detected in half of the cases studied. Furthermore, we observed that in vitro EBV infection of breast carcinoma cells confers resistance to paclitaxel (taxol) and provokes overexpression of a multidrug resistance gene (MDR1). Consequently, even if a small number of breast cancer cells are EBV infected, the impact of EBV infection on the efficiency of anticancer treatment might be of importance.The Epstein-Barr virus (EBV), a ubiquitous human herpesvirus, is associated with the development of different epithelial malignancies (28), including nasopharyngeal carcinoma (NPC). It has also been linked with subsets of other types of carcinomas, including gastric carcinoma and lymphoepithelioma-like carcinoma in salivary glands and thymus (32,44). Several laboratories have reported detection of EBV in a subset of breast tumors (3,10,19,23). However, negative results have also been reported (6,9,14,27). Nevertheless, in most of the studies, a low viral load was detected in breast cancer biopsy specimens but the infected cells were not clearly identified. In the study presented here, we used real-time PCR (Q-PCR) to quantify the copy numbers of the EBV genome in biopsy specimens as well as in microdissected tumor cells. The results show that breast cancer cells harbor the viral genome. However, through microdissection and isolation of pure tumor cells, we now find that even in EBV-positive tumor samples, many tumor cells do not contain EBV genomes and that the breast carcinomas are highly heterogeneous in terms of genome content and distribution. Moreover, using reverse transcription-PCR (RT-PCR), we detected EBNA-1 and BARF-1 transcripts in almost all of the EBV-positive tumors and LMP-1 RNA in 3 of the 15 cases studied. The findings raise the possibility that although EBV is unlikely to have an etiologic role in the genesis of breast cancer, the virus might contribute to tumor progression. Finally, the potential impact of EBV in breast cancer progression was evaluated by estimation of resistance to chemotherapeutic agents on in vitro-infected MDA-MB-231 cells. The resul...

EBV Latent Membrane Protein 1 Up-regulates Hypoxia-Inducible Factor 1α through Siah1-Mediated Down-regulation of Prolyl Hydroxylases 1 and 3 in Nasopharyngeal Epithelial Cells

“…MDA-MB-231 is an EBV-negative breast cancer cell line, and C4A3, C1D12, C2G6, and C3B4 are EBVinfected clones derived from it (31). As shown in Fig.…”

Twist and Epithelial-Mesenchymal Transition Are Induced by the EBV Oncoprotein Latent Membrane Protein 1 and Are Associated with Metastatic Nasopharyngeal Carcinoma

“…Finally, expression of Twist correlates with LMP1 protein expression in human NPC tissues as well as with metastasis. and EBV-infected MDA-MB-231 clones (C4A3, C1D12, C2G6, and C3B4) were described previously (41). The parental MDA-MB-231 cells and C4A3 clone are LMP1 negative.…”

Presencia del virus del papiloma humano y del virus de Epstein-Barr en biopsias de cáncer de mama como posibles factores de riesgo

“…La evidencia más específica de la asociación del VEB con el cáncer de mama ha sido la identificación de secuencias génicas del virus dentro de tumores mamarios 20,21 . Por otra parte, también se ha evaluado la expresión de proteínas latentes del VEB en líneas celulares de cáncer de mama in vitro e in vivo 22 , así como también la capacidad oncogénica de sus proteínas virales 6 . Sin embargo, algunos estudios no han encontrado ninguna relación entre el VEB y el cáncer de mama [23][24][25] .…”