Knockdown of G Protein-coupled Estrogen Receptor 1 (GPER1) Enhances Tumor-supportive Properties in Cervical Carcinoma Cells

A wide variety of answers can be found regarding the question of whether G-protein-coupled estrogen receptor 1 (GPER1) is tumor supportive or tumor suppressive. In cervical carcinoma (CC), the function of GPER1 is poorly understood. In this work, we aimed to clarify what role GPER1 plays in CC, tumor promoting of tumor suppressive. Transient GPER1 silencing was conducted using RNAi and approved by RT-qPCR. Clonogenic potential was tested by colony and sphere formation. Expression of SERPINE1/PAI-1 was quantified by RT-qPCR and Western blot. Morphological changes were analyzed using Phalloidin staining. Localization of GPER1 in tumor spheres was examined by immunofluorescence. After GPER1 knockdown, more colonies formed in HeLa and SiHa, and larger colonies formed in C33-A and SiHa CC cells. Size of HeLa and SiHa tumor spheres was also increased. In addition, number of HeLa tumor spheres was elevated, and larger secondary colonies were present. C33-A only formed tumor sphere-like clusters showing no differences in number and size. Phalloidin staining revealed greater cellular length-to-width ratio and increased average filopodia length. Expression of SERPINE1/PAI-1 was increased in HeLa and decreased in C33-A. In SiHa cells, SERPINE1 was slightly decreased, whereas the protein PAI-1 was increased. Strong expression of GPER1 was detectable in peripheral areas and in sprouts of tumor spheres. GPER1 appears to be tumor suppressive in CC, as GPER1 knockdown provoked increased stem cell properties and increased migration/invasion. EMT also appears to be enhanced. Of interest is the increase in SERPINE1/PAI-1 expression after GPER1 knockdown.