Transforming Growth Factor-α and Insulin-like Growth Factor-I, but Not Epidermal Growth Factor, Elicit Autocrine Stimulation of Mitogenesis in Endometrial Cancer Cell Lines

Abstract

Objectives.Endometrial carcinoma cell lines were evaluated for epidermal growth factor (EGF), transforming growth factor-α (TGF-α), and insulin-like growth factor I (IGF-1) production and for autocrine stimulation.Methods.Conditioned, serum-free media (CM) from cell lines RL95-2, KLE, HEC, and Ishikawa (ISH) were concentrated radioimmunoassayed (RIA). Samples for the IGF-1 assay were extracted with acid–ethanol to remove IGF-1 binding protein. Polymerase chain reaction (PCR) was used to validate the presence of mRNA for growth factors and receptors. Cells were incubated with Ab528, an antibody blocking EGF receptors, and αIR3, an antibody blocking IGF-1 receptors. Proliferation was quantified using [3H]thymidine incorporation.Results.TGF-α was detected in CM: RL95-2 (0.4 ± 0.001 ng/ml), KLE (0.7 ± 0.003 ng/ml), HEC (0.8 ± 0.01 ng/ml), ISH (1.2 ± 0.05 ng/ml). No EGF was detected in CM. In extracted samples, IGF-1 was detected in CM: RL95-2 (0.8 ± 0.03 ng/ml), KLE (1.25 ± 0.02 ng/ml), HEC (1.6 ± 0.01 ng/ml), ISH (1.6 ± 0.08 ng/ml). Unconditioned media served as the control. EGF, TGF-α, and IGF-1 mRNA was identified in all cell lines, as was the mRNA for EGF and IGF-1 receptors. Incubation with Ab528 or αIR3 resulted in significant inhibition of DNA synthesis in HEC 1A, KLE, and ISH. No inhibition was detected in the RL95-2 cell line. A control antibody did not inhibit the cell lines.Conclusion.Autocrine production and stimulation of endometrial carcinoma cell lines by TGF-α and IGF-1 are demonstrated in three of four endometrial cancer cell lines. No measurable EGF was produced by any of the cell lines.