Detection of bovine leukemia virus, Epstein-Barr virus and human papillomavirus in breast cancer tissues of Egyptian patients

Abstract

Background: Breast cancer (BC) remains one of the most common malignancies worldwide. Many viruses have been linked to BC; namely, Human papillomavirus (HPV), Epstein-Barr virus (EBV) and Bovine leukemia virus (BLV). However, a causal role is yet to be established.

Objectives: To detect the prevalence of BLV, EBV and HPV sequences in BC tissue compared to BC-free tissue and correlate their presence with different pathological features of BC.

Subjects and methods: A retrospective case-control study was conducted on 75 FFPE (formalin fixed paraffin embedded) blocks of BC tissues and 25 of BC-free tissues obtained from Alexandria Main University Hospital pathology department archive. Demographic, medical, pathological data were retrieved from patients' archival records. Hormonal receptor status, Real-time PCR for viral detection and HPV genotyping were done. Statistical analysis was done using SPSS software. The Chi-square test, Fisher's Exact correction and Monte Carlo simulation were used for quantitative variables.

Results: Invasive ductal carcinoma was the most predominant histologic type (85.3%). BLV, EBV and HPV were detected in (22.7% vs. 16%, 14.7% vs. 8%, 6.7% vs. 0%) BC vs. non-BC tissues respectively with HR HPV 16 detection. Lymphovascular invasion (LVI) and stage III were more commonly seen among tissues with positive viral detection vs. those which were negative (64.3% vs. 53% and 39% vs. 17% respectively). However, no single viral detection was found to be statistically significant in relation to clinicopathological parameters. Multiple viral co-existence was found in 18% of PCR positive cases which was significantly associated with younger age (P = 0.026).

Conclusion: Low rate of viral presence was found in BC tissues. Nevertheless, LVI and stage III were more commonly seen in tissues with positive viral detection. Moreover, a synergetic relation between multiple viral existence and BC development in young age could be possible yet to be verified.

Keywords: Bovine leukemia virus (BLV); Breast cancer (BC); Epstein-Barr virus (EBV); HPV genotyping; Human papillomaviruses (HPVs).

Fig. 1

A case of invasive ductal carcinoma of no special type NST, G2 showing A: positive nuclear staining for ER antibody, B: positive nuclear staining for PR antibody, C: negative membranous staining (score 0) for Her2-neu antibody (Immunoperoxidase A: x100, B: x200, C: x200)

Fig. 2

A case of Invasive ductal carcinoma of no special type (NST), G3, showing A: negative nuclear staining for ER antibody, B: negative nuclear staining for PR antibody, C: positive membranous staining (score 3+) for Her2-neu antibody (Immunoperoxidase x100)

Fig. 3

A: Invasive ductal carcinoma of No Special Type (NST), G2 (H&E x100), B: Invasive ductal carcinoma of No Special Type (NST), G3 (H&Ex100), C: Invasive lobular carcinoma (H&Ex100), D: Lymph node invasion. Note the microacinar pattern (arrows) (H&Ex200)

Fig. 4

A: Positive and negative samples for BLV TAX gene by real-time PCR (Tm 88 ± 0.5 °C), B: positive samples for BLV TAX gene (114-bp PCR product) on 2% agarose gel. (L: 50 bp gel ladder. 1–6: positive samples.) C: Positive and negative samples for EBV EBNA gene by real-time PCR (Tm 86 ± 0.5 °C), D: Positive samples for EBV EBNA gene (310-bp PCR product) on 2% agarose gel. (L: 50-bp DNA ladder, C+: positive control, 2, 5–8: positive samples, 1, 3–4: Negative samples). E: Positive and negative samples for HPV L1 gene by real-time PCR (Tm 79 ± 0.5 °C), F: Positive samples for HPV L1 gene (150-bp PCR product) on 2% agarose gel. (L: 50-bp DNA ladder, C+: positive control, 1–4: positive samples, 5: Negative sample)

Fig. 5

HPV 16 positive sample by genotyping. (16: Positive sample for genotype HPV 16, IC: Internal Control)