Placenta has the highest expression of epidermal growth factor (EGF) receptor of all tissues, a cell signaling pathway promoting survival and growth. Therefore, EGF receptor inhibition could potentially treat ectopic pregnancy. We undertook preclinical studies to examine whether gefitinib (orally available EGF receptor inhibitor) with or without methotrexate inhibits placental cell growth.
Gefitinib and methotrexate were added to placental cells and their ability inhibit cell growth, block EGF receptor signaling, and induce apoptosis (programmed cell death) was examined. They were also administered to two animal mouse models to examine their effects on placental tissue in vivo.
Epidermal growth factor receptor was highly expressed in placental tissue from ectopic pregnancies. Combining gefitinib with methotrexate potently inhibited growth of placental cells, including placental cell lines (JEG3, BeWo cells) and cells isolated from first-trimester placenta. These drugs were additive in blocking EGF receptor signaling and inducing apoptosis. Gefitinib and methotrexate administered together were more potent in decreasing the volume of human placental cells xenografted subcutaneously onto mice compared with either alone. By day 19 after xenografting, mean (±standard error of the mean), xenograft volumes were: 821 (±68) mm3 after gefitinib treatment, 901 (±204) mm3 after methotrexate treatment, and 345 (±137) mm3 after both drugs were given (P<.01 for both comparisons of single therapy compared with combination therapy). Combining these agents doubled rates of fetal resorption in pregnant mice compared with each drug alone.
Combining gefitinib with methotrexate potently inhibits placental cell growth in vitro and in mouse models. The combination may have potential in treating ectopic pregnancies.