Frequent mutations in breast cancer

The Viral Origin of Human Breast Cancer: From the Mouse Mammary Tumor Virus (MMTV) to the Human Betaretrovirus (HBRV)

A Human Betaretrovirus (HBRV) has been identified in humans, dating as far back as about 4500 years ago, with a high probability of it being acquired by our species around 10,000 years ago, following a species jump from mice to humans. HBRV is the human homolog of the MMTV (mouse mammary tumor virus), which is the etiological agent of murine mammary tumors. The hypothesis of a HMTV (human mammary tumor virus) was proposed about 50 years ago, and has acquired a solid scientific basis during the last 30 years, with the demonstration of a robust link with breast cancer and with PBC, primary biliary cholangitis. This article summarizes most of what is known about MMTV/HMTV/HBRV since the discovery of MMTV at the beginning of last century, to make evident both the quantity and the quality of the research supporting the existence of HBRV and its pathogenic role. Here, it is sufficient to mention that scientific evidence includes that viral sequences have been identified in breast-cancer samples in a worldwide distribution, that the complete proviral genome has been cloned from breast cancer and patients with PBC, and that saliva contains HBRV, as a possible route of inter-human infection. Controversies that have arisen concerning results obtained from human tissues, many of them outdated by new scientific evidence, are critically discussed and confuted.

Chronic Inflammation and Breast Pathology: A Theoretical Model

Breast cell pathology results from biochemical and molecular changes that culminate in the cell’s loss of functional responsiveness. The epithelial cell compartment in the breast ductal system is the site of approximately 98% of malignant proliferations, and it is from within these cells that the first biochemical signal of change may be expressed as an inflammatory response. Inflammation may be represented by biomarkers of early pathologic changes in breast cells and be associated with risk for the development of breast cancer. A theoretical model of the inflammatory process is proposed showing predictive linkages among stimuli in the breast microenvironment and the development of breast pathology, in particular, breast cancer. This model fuels intervention concepts that may prevent malignant breast health outcomes.

Mouse mammary tumor virus and mammary tumorigenesis in wild mice

The current knowledge of the distribution of the mouse mammary tumor virus (MMTV) proviral genomes and the mechanism of mammary tumorigenesis by MMTV in mice, with the main emphasis on Asian feral mice, is reviewed. The relevant earlier discoveries on the mode of MMTV transmission are summarized to provide an outline of the biology of MMTV. Finally, the viral etiology of human breast cancer will be discussed.

Mutations in breast cancer

The genetics of spontaneous breast cancer is reviewed. We have identified three regions of amplification and nine chromosomal arms with deletions in the genome. The significance and interrelations of these mutations is discussed with respect to the complex genetics of breast carcinoma. Recent work identifying a commonly deleted region between D17S846 and D17S746 is presented, which is approximately 0.5-1.0 Mb centromeric to the newly described BRCA1 gene candidate. Possible explanations for the different locations of our deleted region and the BRCA1 gene are presented.