Exposure to Bovine Leukemia Virus Is Associated with Breast Cancer: A Case-Control Study.
BACKGROUND
Age, reproductive history, hormones, genetics, and lifestyle are known risk factors for breast cancer, but the agents that initiate cellular changes from normal to malignant are not understood. We previously detected bovine leukemia virus (BLV), a common oncogenic virus of cattle, in the breast epithelium of humans. The objective of this study was to determine whether the presence of BLV DNA in human mammary epithelium is associated with breast cancer.


METHODS
This was a case-control study of archival formalin fixed paraffin embedded breast tissues from 239 donors, received 2002-2008 from the Cooperative Human Tissue Network. Case definition as breast cancer versus normal (women with no history of breast cancer) was established through medical records and examination of tissues by an anatomical pathologist. Breast exposure to BLV was determined by in situ-PCR detection of a biomarker, BLV DNA, localized within mammary epithelium.


RESULTS
The frequency of BLV DNA in mammary epithelium from women with breast cancer (59%) was significantly higher than in normal controls (29%) (multiply- adjusted odds ratio = 3.07, confidence interval = 1.66-5.69, p = .0004, attributable risk = 37%). In women with premalignant breast changes the frequency of BLV DNA was intermediate (38%) between that of women with breast cancer and normal controls (p for trend < .001).


CONCLUSIONS
Among the specimens in this study, the presence of amplified BLV DNA was significantly associated with breast cancer. The odds ratio magnitude was comparable to those of well-established breast cancer risk factors related to reproductive history, hormones, and lifestyle and was exceeded only by risk factors related to genetics (familial breast cancer), high dose ionizing radiation, and age. These findings have the potential for primary and secondary prevention of breast cancer.
Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, California, United States of America.
Gertrude Case
GC
Buehring
Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, California, United States of America.
Hua Min
HM
Shen
Department of Pathology and Laboratory Medicine, University of California, Davis Medical Center, Sacramento, California, United States of America.
Hanne M
HM
Jensen
Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, California, United States of America.
Diana L
DL
Jin
Atkins Center for Weight and Health, University of California, Berkeley, California, United States of America.
Mark
M
Hudes
Division of Community Health and Human Development, School of Public Health, University of California, Berkeley, California, United States of America.
Gladys
G
Block
D000328:Adult; D000368:Aged; D000818:Animals; D015415:Biomarkers; D001943:Breast Neoplasms / Q000473:pathology / Q000821:virology*; D016022:Case-Control Studies; D002417:Cattle; D005260:Female; D006801:Humans; D001909:Leukemia Virus, Bovine / Q000235:genetics / Q000302:isolation & purification*; D042361:Mammary Glands, Human / Q000473:pathology / Q000821:virology*; D008875:Middle Aged
D015415:Biomarkers