Morphologic alterations in human breast cancer MCF7 cells triggered by co-culture with Spalax fibroblasts. MCF7 cells were co-cultured with skin fibroblasts of Spalax or mouse in the ratio of 1:15 (5 × 104 fibroblasts and 2.5 × 103 cancer cells in six-well plates) in DMEM/DMEM-F12 media (1:1) containing 5% FBS. Representative phase contrast images after 10 days of co-culture are presented (×200). Note rounding and detachment of MCF7 cells co-cultured with Spalax fibroblasts. Black arrows point to rounding cells. White arrows show shrunken “floating” cells.