Mouse sequences detected in human samples are proof of transmission of mouse viruses to human beings

Alexandre FR Stewart a, D William Cameron a, The Lancet Infectious Diseases, Volume 11, Issue 4, Pages 264 - 265, April 2011:

Simard and colleagues1 reported the most current and largest comprehensive assessment of cancer incidence in people with HIV on antiretroviral therapy.

Whereas the incidence of AIDS-defining cancers, Hodgkin's lymphoma, and many other non-AIDS-defining cancers was increased, a striking finding of this report was the nearly 50% reduction in the incidence of breast and prostate cancer.

This paradoxical reduction in breast-cancer risk has been reported in the context of immune suppression.2

Researchers from several laboratories have identified DNA sequences highly homologous to the mouse mammary tumour virus (MMTV; a betaretrovirus of mice) in about 40% of human breast cancer specimens.3—4 Others have identified sequences related to the xenotropic murine leukaemia virus-related virus (XMRV; a gammaretrovirus of mice) in human prostate cancer.5 In both malignancies, a retrovirus from mice has been associated, albeit association itself is not evidence for causality. Furthermore, not all laboratories have replicated these associations, and a retroviral cause in breast and prostate cancer remains controversial. Arguments that mouse sequences detected in human samples are proof of contamination can be equally interpreted as evidence for zoonosis—the transmission of mouse viruses to human beings—as we have suggested.6

Antiretroviral drug treatment (ART) might inhibit retroviruses other than HIV.7

Should ART have an effect on putative oncoviral cancers of long clinical latency or late onset (such as breast and prostate cancer), because HIV is generally acquired during the reproductive years and as the use of ART started in the 1990s, then an effect might be seen only after many years and in later life. A meta-analysis8 published in 2007 noted reduced incidence of prostate cancer, but not breast cancer, in patients with AIDS. Reduced incidence of breast cancer was noted by Simard and colleagues.1

This finding might be related to the long period of HIV immune suppression despite partial immune reconstitution on ART, or it might be due to antiviral activity of ART—if mouse retroviruses contribute to human breast cancer as we have proposed.6

Evidence that ART in patients with HIV is associated with a 50% reduction in the incidence of breast cancer lends further support to the oncoviral hypothesis. Read more>>