Figure 4

Proliferation of the tumor-derived cell lines and their responsiveness to growth factors. (a) The tumor-derived cell lines 78423, 78617, 85815 and 85819 were subjected to SRB assays for measurement of cell growth rate as described in Materials and methods. The means of at least three independent experiments were plotted. SD for each point was less than 10%. (b) The indicated breast cancer cells (5 × 10³) in 0.1 ml culture media were plated onto 96-well plates. After 24 h incubation, cells were grown in either 0.1 ml fresh medium with 0.5% FBS as control, or 0.1 ml same medium containing either 25 ng/ml HRG or 10 ng/ml EGF, and 40 ng/ml IGF-1. Cells were incubated at 37°C with 5% CO₂ for another 72 h, and the percentages of surviving cells from each group relative to controls, defined as 100% survival, were determined by reduction of MTS. Data reflect the means of at least three independent experiments.