4 Epidermal growth factor receptor positively regulates sFlt1 secretion

Abstract

Introduction Preeclampsia is associated with elevated placental secretion of the anti-angiogenic factor sFlt1. Surprisingly, little is understood about its regulation, characterizing this may identify therapeutic leads. Placenta has by far the highest Epidermal Growth Factor Receptor (EGFR) expression of non-malignant tissue. It is localized to the placental surface and elevated in preeclamptic placenta. Objectives Our objective was to characterize EGFR pathway expression in preeclamptic placenta and to assess whether EGFR signaling regulates sFlt1 secretion in primary human placenta. Methods RNA and protein were extracted from a cohort of severe early onset preeclamptic ( n =25) placentas as well as gestational matched normotensive controls ( n =25). EGFR mRNA expression was assessed as well as protein levels of phosphorylated EGFR and the key downstream signaling molecules Erk1/2, Akt and STAT3. We next isolated primary trophoblast from normotensive term placenta and (1) inhibited EGFR signaling with gefitinib (orally available EGFR inhibitor), or (2) inhibited the downstream EGFR signaling cascades with seven different small molecule inhibitors. mRNA expression of sFlt1 variants as well as protein secretion was assessed. EGFR expression was also assessed in primary trophoblasts treated with esomeprazole, pravastatin and sulfasalazine. Results mRNA expression of EGFR was significantly upregulated in preeclamptic placentas. Active EGFR, Erk1/2, Akt and STAT3 were all also significantly increased in preeclamptic placenta. Inhibiting EGFR in primary trophoblasts with gefitinib significantly reduced sFlt1-e15a mRNA and protein expression and total sFlt1 secretion by 30–70% from baseline (Fig. 1). Inhibiting the downstream adaptor molecules MEK1/2 (U0126), Erk/12 (PD98059), c-RAF (ZM336372) and JAK2 (AG490) also induced a significant dose dependent reduction in both sFlt1-e15a and total sFlt1 mRNA and protein expression. Additionally, treating primary trophoblasts with esomeprazole, pravastatin and sulfasalazine all significantly down regulated EGFR mRNA and protein expression coincident with significantly reduced sFlt1 secretion. Conclusions We have identified a new level of molecular regulation for sFlt1. EGFR signaling positively regulate sFlt1 secretion. The implications are that identifying drugs that block EGFR signaling may be a novel therapeutic strategy.