A cellular and biochemical investigation of the effects of epidermal growth factor (EGF) on the growth morphology and invasive potential of a human endometrial carcinoma cell line (RL95-2).

Abstract

A role for EGF in normal and malignant uterine growth is suggested by the presence of epidermal growth factor (EGF) receptors. The effects of EGF on two in vitro passages of a human endometrial carcinoma cell line (RL95-2), designated early (<30, estrogen receptor positive) and late (>250, estrogen receptor negative), were studied with respect to their growth, morphology and invasive properties. The early passage was heterogeneous in population, while the late passage was more homogeneous and exhibited several transformed characteristics. EGF had differential effects depending on the seeding density. At high seeding density, EGF stimulated growth of early passage cells at all concentrations used; EGF stimulated growth of late passage cells at 16.6 pM concentration while it inhibited their growth at 4.98 nM and 20 nM concentrations. At low seeding density, only 20 nM EGF significantly inhibited growth of early passage cells, while the effects of EGF significantly inhibited growth of early passage cells, while the effects of EGF on late passage cells were similar to those at high seeding density. Marked morphological alterations occurred upon addition of 20 nM EGF to RL95-2 cells at low seeding densities. Further, EGF (20 nM) increased the invasive potential of cells of both passages at high seeding density, while it decreased the invasive potential at low seeding density. The decrease in invasive potential correlated with extension of elongated processes by the cells, which could hinder their motility. The increase in invasive potential at high seeding density correlated with an increase in enzymic activity of cell-associated plasminogen activator, which could facilitate degradation of the reconstituted basement membrane matrix in vitro, and with an alteration in morphology and F-actin distribution, which could render the cells more motile. Further studies exploring a possible mechanism for the differential growth response of RL95-2 to EGF at high seeding density indicated that early and late passage cells differed in the number and affinity of EGF receptors. The late passage cells exhibited a 5-fold increase in receptor number over early passage cells and had both high (K(d) of 4.47 x 10⁻¹¹ M) and low affinity receptors (K(d) of 9.37 x 10⁻⁹ M), while the early passage cells had only a single class of high affinity receptors (K(d) of 5.67 x 10⁻¹⁰ M). Thus growth inhibition in the late passage RL95-2 cells correlated with an increase in number of EGF receptors.