Abstract
The human breast cancer cell line MCF-7 requires oestrogen to produce and promote growth of tumours in athymic mice. In vitro, however, MCF-7 cells proliferate rapidly without supply of oestrogen (Briand & Lykkesfeldt, 1984). Oestrogen stimulation of proliferation of MCF-7 cells can be achieved when the cells are grown at high concentration of newborn calf serum (NCS, 10%) or oestrogen deprived foetal calf serum (10%). The stimulation involves an abolishment of inhibitory activity present in the serum. The oestradiol stimulated cultures grow rapidly for a much longer time period and attain a much higher cell density than the unstimulated cultures. Oestrogen is specific for the promotion of cell proliferation and only oestrogen receptor positive cell lines with a functional oestrogen receptor mechanism can be stimulated. We assume that oestradiol acts directly on the cells and via the oestrogen receptor mechanism induces the synthesis of a substance which abolishes the inhibitory activity in serum. We call this mechanism of action an indirect stimulation of cell proliferation. A similar mechanism may exist in vivo since we find that serum from athymic mice contains a growth inhibitory activity towards MCF-7 cells and the inhibitory effect can be abolished by oestradiol.
Highlights
Since oestrogen supplement is required for the formation of tumours of MCF-7 cells in athymic mice, we have investigated whether MCF-7 cells grown in vitro can be stimulated by oestradiol when grown in the presence of athymic mouse serum
The human breast cancer cell line MCF-7 is routinely propagated in medium supplemented with 0.5% foetal calf serum (FCS)
If the cells are grown in the presence of 10% newborn calf serum (NCS), addition of oestradiol (10-8 M) results in a significant increase in the number of cells per culture flask (Figure 1)
Summary
The human breast cancer cell lines MCF-7, T47D, ZR-75-1 and BT-20 were kindly supplied from the Human Cell Culture Bank, Mason Research Institute (Rockville, MD, USA). A T-75 flask seeded with 3.75 x 105 cells was shifted to medium with 1O-6M tamoxifen after one day in growth medium. The cells were allowed to grow for another 22 days in medium without tamoxifen and after this period of time 8 colonies appeared in the culture flask. After the first sub.cultivation of the isolated colonies (sublines) the cells were maintained in medium with 10-6M tamoxifen with a parallel culture without tamoxifen. One of the sublines maintained in control medium was transferred to tamoxifen medium after 19 passages (subline AL-El, first passage) and have continued growth in 10-6M tamoxifen for 29 passages with a split ratio of 1:15 every week. The other cell lines were propagated according to the recommendations from the Cell Culture Bank, except that the HBL100 cell line was adapted to growth with 0.5% FCS
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