Oded Komemi1,4*, Gali Epstein Shochet1,4*, Dana Sadeh2,4, Meir Pomeranz.2,4, Ami Fishman2,4, Liat Drucker1,4, Michael Lishner1,3,4, Shelly Tartakover Matalon1,4
Oncogenetic Laboratory1, Department of Obstetrics & Gynecology2, and internal medicine A3, Meir Medical Center Kfar-Saba and Sackler Faculty of Medicine, Tel-Aviv University4, Israel
Introduction: During implantation cytotrophoblast differentiate to extravillous trophoblast cells (EVT) and invade into the maternal uterine blood vessels. Lately, we demonstrated that HSP27-eIF4E (eukaryotic translation initiation factor-4E) axis regulates cytotrophoblast differentiation to EVT. HSP27 has several important functions including chaperoning and translation regulation. Additional factor, which is suspected to be essential for embryo implantation and decidualisation is STAT3. STAT3 regulates diverse cellular processes such as survival and motility and is required for the maintenance of cancer and embryonic stem cell characteristics. HSP27 interacts closely with STAT3 in cancer cells. We aimed to analyze the effect of HSP27 on placental STAT3 level and activity. Materials & Methods: We evaluated the effect of HSP27 silencing (siRNA) in first trimester human placental explants and in EVT cell line (HTR-8/SVNEO) on total/phospho (Tyr705/Ser727) STAT3 levels (western-blot) and targets (MUC1- invasiveness regulator and stem cell marker), eIF4E (regulator of translation and cytotrophoblast differentiation), IRF1, (regulator of cell death, qPCR).
Results: Silencing HSP27 reduced STAT3 level both in HTR-8/SVNEO cells (72hr; 26%↓ p<0.05) and in placental explants (72hr; 33%↓ p<0.05). Interestingly STAT3 phosphorylation was reduced only in HTR-8/SVNEO cells (72hr; 34%↓ p<0.05), reflecting the effect of factors released from other placental cells on STAT3 phosphorylation. Moreover, silencing of HSP27 in HTR-8/SVNEO cells reduced STAT3 target genes (MUC1, eIF4E and IRF1: 49%↓, 60%↓, 55%↓, respectively, p<0.05).
Conclusions: Our results show that HSP27 regulates STAT3 level and activity in first trimester placenta and suggest the involvement of STAT3 in HSP27/eIF4E axis, which regulates cytotrophoblast differentiation.