Factors secreted by benign mammary epithelial cells inhibit the proliferation of R2-T1AS in suspension. Graph shows proliferation of R2-T1AS cells in suspension cultures in mock-conditioned medium (red line), G2B-10A - conditioned medium (G2B-10A CM, green line), or HuMEC - conditioned medium (HuMEC CM, brown line). To produce conditioned media, G2B-10A cells, HuMEC cells, or no cells (mock) were plated in low-glucose, 5% serum medium, on tissue culture plates. Conditioned media were harvested after a 3-day incubation. For suspension culture, R2-T1AS cells were seeded in conditioned media, in 6-well, low-attachment plates, at a density of 0.3 × 106 cells per well. After 24, 48, and 96 hours media with cells were harvested and cell numbers were determined using an automated cell counter (ViCell), with the use of trypan blue exclusion. Each data point represents a mean of 3 independent experiments (± standard error), with each experiment performed in 3 replicate wells. ** p < 0.001 - for 96 hours time point.