Abstract
Cancer results from the accumulation of somatic mutations of proto-oncogenes and/or tumor suppressor genes during carcinogenesis. An important source of somatic mutations in some animal cancer models is provirus insertion mutation. Such mutations can arise from either retrovirus infection or retrotransposition of active proviral elements present in the germline, and result in the disruption and/or dysregulation of genes at or near sites of new provirus integration. This phenomenon serves as the basis for an experimental strategy for identifying cancer genes, called provirus tagging, in which proviruses act as both mutagens and tags for the subsequent identification of mutated genes that participate in carcinogenesis. In the mouse, two retroviruses cause cancer by this mechanism; mouse mammary tumor virus and murine leukemia virus. The development of PCR-based methods for efficiently recovering host/virus junction fragments from new proviral integrants, as well as the availability of the mouse genome sequence and new bioinformatics tools, has recently led to a dramatic advance in the power of this experimental strategy. As a consequence, large-scale provirus insertion mutation screens are now ongoing in at least three biotechnology companies and two public research centers. These screens demonstrate that mouse provirus insertion mutation models are able to efficiently identify genes involved in human cancer. Moreover, they suggest that an unexpectedly large fraction of the genes in the mammalian genome can contribute to the process of carcinogenesis. Because provirus tagging allows the precise molecular discrimination between cause and consequence, provirus insertion mutation models provide a useful new filter for cancer drug target selection.
Highlights
The remarkable generation of scores of increasingly sophisticated mouse models of mammary cancer over the past two decades has provided tremendous insights into molecular derangements that can lead to cancer
We report that somatic mutations of p53 in mouse mammary epithelial cells lead to ERα-positive and ERαnegative tumors. p53 inactivation in pre-pubertal/pubertal mice, but not in adult mice, leads to the development of ERα-positive tumors, suggesting that developmental stages influence the availability of ERα-positive tumor origin cells
Genetic alterations commonly observed in human breast cancer including c-myc amplification and Her2/Neu/erbB2 activation were seen in these mouse tumors
Summary
Transgenic Oncogenesis Group, Laboratory of Cell Regulation and Carcinogenesis, National Cancer Institute, Bethesda, Maryland, USA. The remarkable generation of scores of increasingly sophisticated mouse models of mammary cancer over the past two decades has provided tremendous insights into molecular derangements that can lead to cancer. The relationships of these models to human breast cancer, remain problematic. P53 inactivation in pre-pubertal/pubertal mice, but not in adult mice, leads to the development of ERα-positive tumors, suggesting that developmental stages influence the availability of ERα-positive tumor origin cells. These tumors have a high rate of metastasis that is independent of tumor latency. Since it is feasible to isolate ERα-positive epithelial cells from normal mammary glands and tumors, molecular mechanisms underlying ERα-positive and ERα-negative mammary carcinogenesis can be systematically addressed using this model
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have