Dairy cattle serum and milk factors contributing to the risk of colon and breast cancers

Abstract

The analysis of published epidemiological data on colon and breast cancer reveals a remarkable concordance for most regions of the world. A low incidence for both cancers has been recorded in Mongolia and Bolivia. Discrepant data, however, have been reported for India, Japan and Korea. In India, the incidence of breast cancer is significantly higher than for colon cancer, in Japan and Korea colon cancer exceeds by far the rate of breast cancer. Here, studies are summarized pointing to a species-specific risk for colon cancer after consumption of beef originating from dairy cattle. Uptake of dairy products of Bos taurus-derived milk cattle, particularly consumed at early age, is suggested to represent one of the main risk factors for the development of breast cancer. A recent demonstration of reduced breast cancer rates in individuals with lactose intolerance (Ji et al., Br J Cancer 2014; 112:149-52) seems to be in line with this interpretation. Species-specific risk factors for these cancers are compatible with the transmission of different infectious factors transferred via meat or dairy products. Countries with discordant rates of colon and breast cancer reveal a similar discordance between meat and milk product consumption of dairy cattle. The recent isolation of a larger number of novel presumably viral DNAs from serum, meat and dairy products of healthy dairy cows, at least part of them infectious for human cells, deserves further investigation. Systemic infections early in life, resulting in latency and prevention of subsequent infections with the same agent by neutralizing antibodies, would require reconsideration of ongoing prospective studies conducted in the adult population. What's new? While the association between human papilloma virus (HPV) infection and cervical cancer is well established, viral causes for other common cancers remain less clear. Here, Prof. Harald zur Hausen, the former editor-in-chief of IJC, and Prof. Ethel-Michele de Villiers summarize intriguing epidemiological data linking dairy cattle and milk consumption with colon and breast cancer. A possible connection with recently isolated episomally persisting circular single-stranded DNA, presumably of viral origin, is also being discussed. This analysis may increase attention to species-specific infectious factors present in dairy cattle meat, serum or milk that, if confirmed, could contribute to the pathogenesis of common cancers like colon and breast cancer.