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

Bovine leukemia virus (BLV) causes enzootic bovine leukemia, andis 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 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. 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. 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 prognosis 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. The obtained results support the idea that BLV might play a role in malignant tissue transformation.