Abstract
BackgroundFocal adhesion kinase (FAK) is a cytoplasmatic protein tyrosine kinase that associates with both integrins and growth factor receptors toward the adhesion, migration and invasion of cancer cells. The G-protein coupled estrogen receptor (GPER) has been involved in the stimulatory action of estrogens in breast tumor. In this study, we have investigated the engagement of FAK by GPER signaling in triple negative breast cancer (TNBC) cells.MethodsPublicly available large-scale database and patient data sets derived from “The Cancer Genome Atlas” (TCGA; www.cbioportal.org) were used to assess FAK expression in TNBC, non-TNBC tumors and normal breast tissues. MDA-MB 231 and SUM159 TNBC cells were used as model system. The levels of phosphorylated FAK, other transduction mediators and target genes were detected by western blotting analysis. Focal adhesion assay was carried out in order to determine the focal adhesion points and the formation of focal adhesions (FAs). Luciferase assays were performed to evaluate the promoters activity of c-FOS, EGR1 and CTGF upon GPER activation. The mRNA expression of the aforementioned genes was measured by real time-PCR. Boyden chamber and wound healing assays were used in order to evaluate cell migration. The statistical analysis was performed by ANOVA.ResultsWe first determined by bioinformatic analysis that the mRNA expression levels of the gene encoding FAK, namely PTK2, is higher in TNBC respect to non-TNBC and normal breast tissues. Next, we found that estrogenic GPER signaling triggers Y397 FAK phosphorylation as well as the increase of focal adhesion points (FAs) in TNBC cells. Besides, we ascertained that GPER and FAK activation are involved in the STAT3 nuclear accumulation and gene expression changes. As biological counterpart, we show that FAK inhibition prevents the migration of TNBC cells upon GPER activation.ConclusionsThe present data provide novel insights regarding the action of FAK in TNBC. Moreover, on the basis of our findings estrogenic GPER signaling may be considered among the transduction mechanisms engaging FAK toward breast cancer progression.
Highlights
Focal adhesion kinase (FAK) is a cytoplasmatic protein tyrosine kinase that associates with both integrins and growth factor receptors toward the adhesion, migration and invasion of cancer cells
In the framework of the aforementioned findings, in the current study we have focused on the role of G-protein coupled estrogen receptor (GPER) in the regulation of FAK signaling by estrogens using the invasive and metastatic triple negative breast cancer (TNBC) MDA-MB 231 and SUM159 cells as experimental model
The analysis of the RNA sequencing data derived from Invasive Breast Cancer Cohort of TCGA project (The Cancer Genome Atlas: https://cancergenome.nih.gov/), revealed that the PTK2 mRNA expression levels are significantly higher in TNBC compared with normal breast tissues in two independent cohort datasets (Fig. 1a-b)
Summary
Focal adhesion kinase (FAK) is a cytoplasmatic protein tyrosine kinase that associates with both integrins and growth factor receptors toward the adhesion, migration and invasion of cancer cells. FAK action has been associated to aggressive cancer features as the cell adhesion and spreading [20,21,22], the enhancement of cell proliferation and survival [23, 24] and the facilitation of invasive cell phenotypes [25,26,27]. In this context, it is worth mentioning that FAK was shown to be over-expressed in a wide variety of human malignancies, including invasive and metastatic breast tumors [28,29,30]. Neverthless, a better understanding on the molecular mechanisms through which FAK activation may contribute to breast cancer progression is still needed
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