Tissue culture conditions determine the effects of estrogen and growth factors on the anchorage independent growth of human breast cancer cell lines.

We determined the effects of epidermal growth factor, insulin-like-growth-factor-1 and estradiol on the anchorage independent growth of the estrogen receptor positive human breast cancer cell lines MCF7 and T-47D. In serum free conditions growth factors but not estrogen induced a dose dependent stimulation of growth in both cell lines. The ability of estrogen to induce colony formation of early passage MCF7 cells (less than 100) was strictly correlated to the concentration of sulfatase and charcoal treated calf serum (CCS) with a maximal effect at a concentration of 5% CCS and 10 nM estradiol. CCS alone had no stimulatory effect on the anchorage independent growth of early passage MCF7 cells, but increased colony formation in late passage (greater than 1000) MCF7 and T-47D cells. The growth of late passage MCF7 cells was inhibited by antiestrogen. Thus, the presence of serum components is necessary for the effect of estrogen but not for the effects of growth factors on the anchorage independent growth of estrogen receptor positive human breast cancer cell lines; after a prolonged period of tissue culture serum components switch their function from indirectly modulating estrogen effects to directly stimulating growth in the absence of estrogen.