Buehring emphasized that this study does not identify how the virus infected the breast tissue samples in their study. So far, they have found that 59 percent of breast cancer cells showed the presence of BLV DNA.
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“We still need to confirm that the infection with the virus happened before, not after, the breast cancer developed, and if so, how”, says the study’s lead author, Professor Gertrude Buehring from the Division of Infectious Diseases and Vaccinology at University of California Berkeley’s School of Public Health.
While the researchers claim that they have not definitely proven a cause-and-effect relationship between the virus and breast cancer, they go on to state that it could possibly be attributed to 37% types of breast cancers out there.
For more than 30 years, BLV, a virus that causes leukemia and lymphoma in cattle, was not believed to infect humans. Meanwhile, a 2007 bulk milk tank survey conducted by the US Department of Agriculture (USDA) showed that large-scale herd operations, or those with no less than 500 cows, contained BLV antibodies.
“The tests we have now are more sensitive, but it was still hard to overturn the established dogma that BLV was not transmissible to humans”. BLV is present in much of marketed beef and dairy products, and breast cancer incidence is greatest in countries with high consumption of bovine foodstuffs. The tissue was donated from the Cooperative Human Tissue Network. Professor Buehring insists that researchers have yet to prove that bovine leukemia causes breast cancer, if that is indeed the case.
Researchers at UC Berkeley analysed samples of breast tissue from 239 women, with and without breast cancer. She mentioned that the discovery does not indicated that BLV causes cancer, but that it is, for the time being, suspected of playing a major part cancer development. Dairy operations with small herds of less than 100 cows tested positive for BLV 83% of the time. The virus may have been delivered through unpasteurized milk, undercooked meat, or via another human.
The findings were published earlier this month, in the journal PLOS ONE.
In the past three decades, there was no evidence that BLV, the leukemia-causing virus found in cattle, could be passed down to humans. According to Buehring, that is the most important question that needs to be answered. It is not known how the subjects in this study became infected with BLV.
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According to Medical News Today, it was only discovered in 2014 that the transmission of BLV to humans is possible. It could shift the emphasis to prevention of breast cancer, rather than trying to cure or control it after it has already occurred, added Buehring.
