[Malignant transformation of mouse embryo cells by estrogenic hormones in vitro]

Mouse embryo cells (MEC) taken from a LACA pregnant female mouse, were cultured in RPMI 1640 medium with 20% horse serum. In the experimental group (10 bottles), the first 3 generations of MEC were treated with estradiol valerate (E) and hydroxyprogesterone caproate (P) at doses of 5.2 micrograms/ml and 261 micrograms/ml medium in the original and the 2nd generations, and at double doses in the 1st generation. In the control group (10 bottles), the MEC were cultured without E and P. The MEC in both groups was subdivided into 3 bottles from 1 every seven days. In the experimental group (44 bottles), the morphological transformation emerged in 2 bottles of MEC (the 5th and 7th generations) after 79 day's treatment by E and P. Meanwhile, the nonmorphological transformed cells (the 3rd, 5th and 7th generations) had the ability to grow in ouabain-contained medium (Anti-Oua+). It implies that the mutation had already occurred before transformation. The transformed cells had the ability to form colonies in soft-agar medium, could be agglutinated by concanavalin A and form fibrosarcoma in the subcutaneous region after inoculation. Basing on the above results, we suggest that E and P directly act as a carcinogen on the MEC and cause the latter to undergo malignant transformation.