High positivity values for bovine leukemia virus in human breast cancer cases from Minas Gerais, Brazil

Abstract

Bovine leukemia virus (BLV) is a retrovirus that causes lymphoma in cattle worldwide and has also been associated with breast cancer in humans. The mechanism of BLV infection in humans and its implication as a primary cause of cancer in women are not known yet. BLV infection in humans may be caused by the consumption of milk and milk-products or meat from infected animals. Breast cancer incidence rates in Brazil are high, corresponding to 29.5% a year of cancer cases among women. In 2020, an estimated 66,280 new cases of breast cancer are expected, whereas in 2018 breast cancer has led to 17,572 deaths, the highest incidence and lethality among cancers in women in this country that year. BLV infection occurrence ranges from 60 to 95% in dairy herds. In addition, there are some regions, such as the Minas Gerais State, southeastern Brazil, where the population traditionally consume unpasteurized dairy products. Taken together, this study aimed to verify if there is a higher association between breast cancer and the presence of BLV genome in breast tissue samples within this population that consumes raw milk from animals with high rates of BLV infection. A molecular study of two BLV genes was carried out in 88 breast parenchyma samples, between tumors and controls. The amplified fragment was subjected to BLV proviral sequencing and its identity was confirmed using GenBank. BLV proviral genes were amplified from tumor breast parenchyma samples and healthy tissue control samples from women, revealing a 95.9% (47/49) and 59% (23/39) positivity, respectively. Our results show the highest correlation of BLV and human breast cancer found in the world to date within the population of Minas Gerais, Brazil.

Catching viral breast cancer

“…The prevalence of BLV in the dairy cattle present in more than 90% of the animals. BLV was identified in 96% of human breast cancers as compared to 59% of normal breast controls [ 12 ].…”

“…There is new evidence that Epstein Barr viruses enhance the role of HPVs in breast cancer including the invasive capacity of breast cancer cells [7][8][9]. New case control studies have confirmed the probable role of bovine leukemia virus (BLV) in human breast cancer [10][11][12]. BLV has been identified in human blood which suggests a means of internal transmission of this virus to breasts [13].…”

Co-Circulation of Bovine Leukemia Virus Haplotypes among Humans, Animals, and Food Products: New Insights of Its Zoonotic Potential

“…In addition, evidence of BLV in human beings has been reported by different researchers via the presence of its gene segments, proteins and antibodies against the virus in different parts of the world [ 23 , 24 , 25 , 26 , 27 , 28 ]. Epidemiological studies have identified a significant association between the presence of the virus and breast cancer development, proposing BLV as an intermediate risk factor for cancer outcome [ 29 , 30 ].…”

Molecular investigation of possible relationships concerning bovine leukemia virus and breast cancer

“…The relationship between breast cancer and BLV has inadequate evidence. However, recent findings from different countries showed varying percentages of BLV prevalence in breast cancer, i.e., 74% in Berkeley California 9 , 40.5%in Colombia 6 , 44% in Birmingham, Alabama, Pennsylvania, Ohio, Oakland, California 11 , 59% in California 10 , 80% in Australian women 45 , 34% in women in Texas 46 , 38% in California 4 , and 30.5% in South Brazil 47 , and the highest percentage of BLV prevalence was found at 95.9% in Minas Gerais, Brazil 48 . The association of BLV with breast cancer is still controversial, but the recent studies discussed above strongly suggest the significance of the relationship between breast cancer and BLV.…”