The growth of malignant and nonmalignant human cells is modulated by a human placental extract

Background: In the present paper; malignant and nonmalignant human cells we re compared in their response to a fraction (fraction D, FD) of a human pla cental extract. Materials and Methods: The activity of FD was tested on cel l proliferation both in the absence and in the presence of 5% 10% and 15% f etal bovine serum (FBS). For cells growing in monolayers, the medium was re newed with fresh medium containing FD 24 hours after plating and 3 days aft er the first exposure. In breast cancer cells only, it was also changed aft er 6 days. For leukemic cells, which grow in suspension, FD was added direc tly to the medium the day of the seeding and then after 3 and 6 days. Resul ts: In normal fibroblasts, when plated at a low density, a strong inhibitor y effect on cell growth was seen with the highest FD dose. This effect was observed in the presence of 5% and 10% FBS, while it disappeared with 15% F BS. In endothelial cells, FD, in the presence of 5% or 10% FBS, produced a modest bur constant inhibition of cell proliferation, which was evident aft er a short treatment and with almost every dose of FD. Breast cancel and le ukemic cell lines, plated at a standard density, were markedly inhibited by FD, but this effect was reversed in serum-free conditions, at least in mam mary cells. In leukemic cells, after an initial stimulatory effect, FD was not able to counterbalance the absence of serum. Conclusions: Our data seem to suggest that in FD both stimulating and inhibitory growth-factors coexi st, the activity of which are greatly influenced by the culture conditions used.