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LOW INCIDENCE OF MAMMARY CANCERS IN UNGULATES
A meta-analysis and causal review
Researcher
SARAH BILLINGS
Hello! My name is Sarah Billings and I am a senior at Smith College. I am a biochemistry and Spanish double major.
ABSTRACT
Mammary cancer is common in most mammals, but extremely rare in ungulates, which are mammals with hooves. Here we present a meta-data analysis and the first tabulation of available case studies of the disease in ungulates in order to examine three current theories regarding the observed low incidence of mammary cancer in these species. The hypotheses include: 1) hormone levels from frequent pregnancies prevent mammary cancer in ungulates; 2) the ungulate herbivorous diet and microbial digestion offer protection; or 3) a genetic factor shields ungulates from mammary cancer. Our analysis suggests that genetic factors are the most plausible cause of the low rates of mammary cancer in ungulates and does not support the hormone hypothesis. Direct or indirect effects of the intestinal microbiome cannot be excluded and require further research. Finally, we tabulate all of the well documented primary and secondary case studies of ungulates with malignant mammary neoplasia in order to serve as a jumping-off point for future research. This comparative oncology analysis, illuminating factors that may lower the frequency of mammary cancer in ungulates, could lead to a more comprehensive understanding of the disease in other mammals and might uncover novel therapeutic approaches.
DOWNLOADABLE MATERIALS
Our lack of understanding here highlights a field lacking biochemical study. In fact, one of my main goals with this paper is to stimulate research in this area. To this end, I have linked my bibliography and table of all documented cases of ungulate mammary cancer in the downloads section. Most studies of breast cancer have been conducted in human models. Perhaps, looking at other mammals would be beneficial. Studying breast cancer through the lens of comparative oncology could lead to possible therapeutics and a better understanding of cancer dynamics.
