MAMMARY-TUMOR VIRUS-DNA AS A MARKER FOR GENOTYPIC VARIANCE WITHIN HORMONE-RESPONSIVE GR MOUSE MAMMARY-TUMORS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (3) , 1154-1158
Abstract
Mammary tumors of GR mice acquire extra mammary tumor virus (MMTV) DNA information within their DNA during tumor growth and development. These extra MMTV genes were used as genotypic markers to investigate the heterogeneity of GR mammary tumors and their loss of hormone dependence during serial transplantation. The various subpopulations of cells within individual GR mammary tumors appear to be characterized by differences in number and location of acquired extra MMT7V DNA fragments. Losses of certain of these extra MMTV DNA fragments occur when mammary tumors become hormone independent, indicating a loss of hormone-dependent cells. The study of MMTV DNA markers also reveals that low levels of autonomous cells are already present in some hormone-dependent mammary tumors at an early stage of their development. The genotypic analysis strongly indicates that mammary tumor progression is not due to phenotypic adaptation but to clonal selection of the more aggressive sublines.