Lack of Association Between Epstein-Barr Virus and Mammary Tumours in Dogs

Abstract

Introduction: Epstein-Barr virus (EBV) is a γ-herpesvirus associated with various neoplasms in humans and is a probable aetiological agent in breast cancer; however, a causal relationship has not yet been established. Because of the epidemiological and clinicopathological similarities between breast cancer and canine mammary tumours, dogs have been proposed as a valid model for breast cancer.

Material and methods: A total of 47 canine mammary gland tumour tissues were processed by routine histopathological technique with haematoxylin-eosin staining and classified according to the type of neoplasm. DNA was extracted from paraffin-embedded tissues and the EBNA-1 gene and the BamHI-W region specific for EBV were evaluated by nested PCR.

Results: The histopathological evaluation revealed 2 benign neoplasms, and many carcinomas: 2 in situ, 9 simple, 3 solid, 10 complex, and 21 mixed. One sample was positive for the EBNA-1 gene, while all were negative for the BamHI-W region.

Conclusion: No association was found between EBV and mammary tumours in dogs. However, here we report for the first time the presence of an EBV gene sequence in a canine mammary tumour. It is likely that detection of EBV might be affected by the quality and quantity of DNA extracted from paraffin-embedded tissues. Additional studies are necessary to establish any association of EBV with mammary gland cancer in humans and in dogs, which could eventually lead to better public health prevention and control.

Keywords: Epstein–Barr virus; comparative pathology; dogs; mammary gland cancer.

Fig. 1

Histological features of canine mammary gland tumours. A, B – simple carcinoma, tubulopapillary type, C, D – solid carcinoma, E – simple carcinoma, F – complex carcinoma, G – tubulopapillary carcinoma, H, I – carcinoma, cystic-papillary type, J – complex carcinoma, K – simple adenoma, L – simple carcinoma, tubulopapillary type

Fig. 2

PCR amplification of EBV EBNA-1 gene in canine mammary tumours by nested PCR. M – 100 bp molecular weight marker. Lanes 01– 05 – samples of canine mammary tumours, using first a volume of amplicon of 1.5 μL (to the left), 2 μL (in the middle), and 4 μL (to the right) for the second reaction of PCR. Lanes 06–07 – EBV positive control. N – negative controls. Sample 01 on the right showed a product of the expected size of 209 bp, using a volume of 4 μL of amplicon for the second round of amplification