Bovine Leukemia Virus Presence in Breast Tissue of Argentinian Females and Its Association With Cell Proliferation and Prognosis Markers

Introduction: Bovine leukemia virus (BLV) causes enzootic bovine leukemia, and is closely related to human T-lymphotropic virus type 1. It expresses microRNAs of unknown function and codes Tax, the protein that mediates malignant transformation. BLV is capable of infecting B- and T-lymphocytes, endothelial cells, and mammary epithelial cells of cattle. Several studies demonstrated the presence of BLV DNA in human tissue, and it is significantly associated with breast cancer in case-control studies using in situ Polymerase Chain Reaction (PCR), a highly sensitive and specific technique. The current study was the first report of BLV DNA detection by in situ PCR in tissue from Argentinian females with a diagnosis of breast cancer. Methods: In situ PCR was done to detect BLV DNA in 85 human FFPE breast cancer tissue samples. The association of BLV DNA and expression of Ki67 and Her-2 was assessed. Results: BLV DNA presence could be determined in 22.6% of the analyzed samples, and its presence was associated with an increase of the expression and prognostic markers Ki67 (P=0.009) and HER-2 (P=0.044) determined by conventional immunohistochemistry. No statistical significance was observed between the presence or absence of hormonal receptors and the presence of BLV DNA. Conclusions: The obtained results support the idea that BLV might play a role in malignant tissue transformation.