Evidence of bovine leukemia virus genes detected in Colombian women with and without breast cancer: A zoonotic infection

Bovine leukemia virus (BLV), is an oncogenic virus that infects cattle worldwide and is the causative agent of leukemias, lymphomas and persistent lymphocytosis. BLV has also been found in humans and has recently been proposed as a risk factor for developing breast cancer in the USA and Australia. In Colombia, there is evidence of infection in women but no correlation with breast cancer. This study was aimed at comparing the presence of the virus in breast tissue from different sources: necropsies of women without tumor development (normal breast tissue), and surgeries of benign and malignant tumors, to better understand the role of BLV in Colombia. A cross-sectional study was designed in which 315 participants were included. Paired samples of breast tissue and blood were obtained from surgeries and necropsies in Bogota city. The presence of BLV was determined by nested PCR and in situPCR targeting different viral genes. For the nested PCR, DNA was extracted from fresh tissues and blood samples, and human GAPDH amplification was carried out to assess DNA quality for the PCRs. Afterwards, different BLV genes were detected by nested PCR. In situ PCR was directed to the tax region of the virus and was done to FFPE sections of the same samples. Positive samples were considered when at least one of the techniques was positive for the virus and were confirmed by Sanger sequencing. Correlation with other risk factors related with breast cancer (HER2, PR, ER and KI67) and the presence of the virus were determined. From the overall population, 40% of the samples were positive for BLV. In the breast cancer population, 37% of the samples were infected with the virus; similar distributions were found in the other groups (pre-malignant, 33%; benign tumors, 27%). Interestingly, almost 60% of the samples were infected in the no-tumor group. 22% of the samples were positive for both breast tissue and blood from the same patients. All the positive samples were confirmed to have BLV by Sanger sequencing of different gene regions of the virus. When correlating viral presence with other risk factors of breast cancer, it was found that most of the positive BLV samples were also positive for progesterone (79%) and estrogen (93%) receptors and were negative for the HER2 mutation. It could thus be possible that the hormonal profile could be linked with the presence of the virus. This study shows that irrespective of the breast pathology, BLV can be found in Colombian women both in breast tissue and blood. Sanger sequencing showed that the virus found in humans is similar to previously reported sequences obtained from cattle with high identity percentages. Even when the biology of the virus remains unknown in humans, it is a big concern to find the presence of an oncogenic virus coming from animals. Further studies are needed to understand the viral mechanisms related with cancer in humans. Citation Format: Nury N. Olaya-Galan, Sandra P. Salas-Cardenas, Adriana P. Corredor-Figueroa, Gertrude C. Buehring, HuaMin Shen, Manuel A. Patarroyo, Ma, Fernanda Gutierrez. Evidence of bovine leukemia virus genes detected in Colombian women with and without breast cancer: A zoonotic infection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4220.