Medical Hypothesis only: Do dogs harbor risk factors for human breast cancer?

1: Med Hypotheses. 2006 Mar 2; [Epub ahead of print] Links

Do dogs harbour risk factors for human breast cancer?

Laumbacher B, Fellerhoff B, Herzberger B, Wank R.

Institute of Immunology, Klinikum Innenstadt, University of Munich, Goethestrasse 31, 80336 Muenchen, Germany.

We ask consulting patients regularly whether they keep pets in order to identify zoonotic factors. It became apparent that patients with breast carcinoma (N=69) owned significantly more often dogs but not cats compared to age matched female controls. We compared the frequencies of dog and pet ownership with data from public available statistics on women (N=1320) of the same age group in Bavaria. The most striking result was that more than twice the number of patients kept dogs permanently in the last 10 years and at the time of interrogation as compared to control individuals at the time of interrogation (p=0.0000003, relative risk 3.5). Further internet search on the morbidity of breast carcinoma showed in dogs a protracted course of disease and metastases into lung, liver and bones, resembling the course of disease in human breast cancer. In contrast with this, breast cancer presented in cats a dramatically short course and the main but unusual location of metastasis presents in the hind legs. A recent publication in Norway reported on a high frequency (53.3%) of breast carcinomas in 14,401 investigated dogs. Which transmissible factor or factors come into question? Variants of the mouse mammary tumor virus (MMTV) can productively replicate in human cells and in different animals, including dogs. Many investigators, but not all, could identify MMTV-like sequences in sporadic human breast cancer. MMTV or MMTV-like sequences have not been investigated in canine breast carcinomas until now. It is also conceivable that other microbes from the dog, for example bacteria, could participate in the first steps of carcinogenesis in human. It was recently shown that bartonella species promote vascularization and prevent apoptosis of infected cells with the same methods as helicobacter pylori. Our considerations require further research. Epidemiologic cohort studies and identification of potential carcinogenic microbial factors will prove or disprove our hypothesis that risk factors from dogs could contribute to the carcinogenesis of human breast cancer.

PMID: 16516398 [PubMed - as supplied by publisher]

[Christine MH-UK]

I have never owned a dog, but found this interesting. Some recent Brazilian research suggests that her2+++ mammary cancer occurs in dogs: A.P. Dutra1, N.V.M. Granja2, F.C. Schmitt3 and G.D. Cassali1 c-erbB-2 expression and nuclear pleomorphism in canine mammary tumors http://www.scielo.br/scielo.php?scri...lng=en&nrm=iso

although one Japanese study (Immunohistochemical analysis of c-yes and c-erbB-2 oncogene products and p53 tumor suppressor protein in canine mammary tumors) found no connection.

A Spanish study found that her2 overexpression, not overamplification occurred in dogs:
http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum
but a Japanese study did not find her2 expression to be common in dog cancer.

The oldest study, based in the U.S. (Expression of the oncogene c-erbB-2 in canine mammary cancers and tumor-derived cell lines), found a very high rate of her2+++ among dogs.

However, viruses like MMTV are known to be more common in some areas than others, so regional variations migh help to explain the wide range of findings.