MALIGNANT PROGRESSION OF SV40-IMMORTALIZED HUMAN-MILK EPITHELIAL-CELLS

A human breast epithelial cell line (Hu-MI), established by microinjec ting SV40 DNA into human milk epithelial cells, exhibits the phenotype of luminal epithelial cells and is neither clonogenic nor tumorigenic . From this cell line we have selected two sublines, HuMI-T and HuMI-T Tu1, reflecting different stages of spontaneous transformation. HuMI-T cells grow anchorage-independently, but do not induce tumours in nude mice. HuMI-TTu1 cells are clonogenic as well as tumorigenic. Cells fr om both lines exhibit polymorphic structural and numerical chromosome aberrations. Immortalisation of normal luminal epithelial cells from h uman mammary gland with SV40 DNA alone may thus cause random genetic c hanges eventually resulting in tumorigenic cell lines. Since Hu-MI, Hu MI-T and HuMI-TTu1 represent some of the consecutive stages taking pla ce during cellular transformation, they are particularly suited as a n ovel in vitro model system to study progression of human breast cancer .