Proliferation and apoptosis regulation by G protein‑coupled estrogen receptor in glioblastoma C6 cells

Abstract

Glioblastoma is the most frequent primary tumor in the human brain. Glioblastoma cells express aromatase and the classic estrogen receptors ERα and ERβ and can produce estrogens that promote tumor growth. The membrane G protein-coupled estrogen receptor (GPER) also plays a significant role in numerous types of cancer; its participation in glioblastoma tumor development is not entirely known. The present study investigated the effect of the agonists [17β-estradiol (E2) and G1] and antagonist (G15) of GPER on proliferation and apoptosis of C6 glioblastoma cells. GPER expression was evaluated by immunofluorescence, western blotting and reverse transcription-quantitative PCR. Cell proliferation was determined using Ki67 immunopositivity. Cell viability was examined using the MTT assay and apoptosis using caspase-3 immunostaining and ELISA. C6 cells express GPER, and the immunopositivity increased after exposure to E2, G1, or their combination. GPER protein expression increased after treatment with E2 combined with G1. However, GPER mRNA expression decreased in treated cells compared with control. The percentage of Ki67 immunopositive C6 cells increased under the effect of E2 in combination with G1 or G1 alone. G15 significantly reduced Ki67 immunopositivity. Pearson's correlation analysis revealed a positive relationship between GPER and Ki67 immunopositivity across the study conditions. Additionally, the MTT assay showed a significant reduction in C6 cell viability after G15 treatment, alone or in combination with G1. The exposure to G15 increased the percentage of caspase-3 immunopositivity cells and caspase-3 levels. Pearson's correlation analysis demonstrated a negative correlation between GPER and caspase-3 immunopositivity across the study conditions. Glioblastoma C6 cells express GPER, and this receptor modulates cell proliferation and apoptosis. The GPER agonists E2 and G1 favored cell proliferation; meanwhile, the antagonist G15 reduced cell proliferation, viability and favored apoptosis. Therefore, GPER may be used as a biomarker of glioblastoma and as a target to develop new therapeutic strategies for glioblastoma treatment.

Combinatorial chemotherapy via poloxamer 188 surface-modified PLGA nanoparticles that traverse the blood-brain-barrier in a glioblastoma model

“…To distinguish the best response to the treatment between P-MTX NPs+P-PTX NPs and P-PTX NPs, the expressed Ki-67, VEGF, p53 and MMP-2 was quantified. Ki-67 is a marker to estimate proliferation and metastasis in tumors [98]. VEGF plays a role in angiogenesis [99] using the amount of expression as a factor to estimate the severity of GBM [64].…”

Locomotion Outcome Improvement in Mice with Glioblastoma Multiforme after Treatment with Anastrozole

“…This study found that ERα and GPR30 decreased expression in the GBM anastrozole-treated group. The reduced number of tumor cells could be due to low estrogen alpha and GPER receptor expression and estrogen levels [ 10 , 29 ]. Further experiments are needed to quantify estrogen receptor expression in GBM-treated anastrozole mice.…”

GPER: An Estrogen Receptor Key in Metastasis and Tumoral Microenvironments

“…A higher GPER expression in cancer cells and tissues favors cancer development, and GPER levels serve as indicators for survival prognoses, where elevated levels are related to bad outcomes. Some examples of the above have been observed in lung, prostate, cervical, glioblastoma, and breast cancer models [49][50][51][52][53]. Moreover, GPER expression is related to stemness features in breast cancer stem cells (BCSC) through phosphorylation of BCL2associated agonist of cell death (BAD) promoting cell survival, but the silencing of GPER results in a decrease in BCSC in vivo [54,55].…”