PYK2 promotes cell proliferation and epithelial-mesenchymal transition in endometriosis by phosphorylating Snail1

Endometriosis can lead to decreased endometrial receptivity, reduced rates of implantation, and diminished ovarian reserve. Currently, more than 50% of infertile women are found to suffer from endometriosis. However the etiology and pathogenesis of endometriosis are still poorly understood. Epithelial-mesenchymal transition (EMT) has been confirmed to be involved in endometriosis. PYK2 is a non-receptor tyrosine kinase that affects cell proliferation, survival, and migration by regulating intracellular signaling pathways. PYK2 plays a regulatory role in the EMT process by affecting the expression of genes associated with EMT through the influence of transcription factors. Snail1 (Snail1) plays a key role in the EMT process and is highly expressed in endometriosis tissues. On the other hand, Snail1 affects the invasive and metastatic ability of endometriosis cells mainly by regulating the EMT process. However, the upstream mechanisms that regulate the process of Snail1 protein stability in endometriosis are not clear.

We identified a non-receptor tyrosine kinase, proline-rich tyrosine kinase 2 (PYK2 or PTK2B), and examined the expression of PYK2 in endometriosis. The relevant plasmids were constructed. This study enrolled 20 patients with laparoscopically confirmed endometriosis meeting ASRM diagnostic criteria, collecting ectopic lesions (14 ovarian endometriotic cysts and 6 deep infiltrating nodules) along with matched eutopic endometrial tissues (15 proliferative phase, 5 secretory phase) as controls. All tissue specimens underwent immunohistochemical analysis. Human endometrial stromal cells (HESC) were isolated from normal endometrium of 3 control patients for in vitro meconium induction. Ectopic endometrial stromal cells (EESC) were obtained from 5 ectopic lesions. Protein extracts from both ectopic tissues and cells were subjected to Western blot and co-immunoprecipitation (Co-IP) interaction validation. Functional assays (proliferation/migration/invasion) were performed using EESC and 11Z cell lines with triplicate biological replicates. Co-IP experiments were performed to verify the interaction between PYK2 and Snail1, as well as to determine the specific location of this interaction. Additionally, we examined the effect of PYK2 on endometriosis cells in vitro and whether VS-6063 inhibits the biological functions of endometriosis cells. Endometriosis models were established in 20 five-week-old female C57BL/6 mice, randomly allocated into experimental (n = 10) and control (n = 10) groups. Statistical analyses were conducted using GraphPad Prism 7.0, employing parametric tests for normally distributed data and non-parametric methods otherwise, with Benjamini-Hochberg correction for multiple comparisons.

PYK2 is highly expressed in endometriosis tissues. It acts as a new binding partner of Snail1 and enhances EMT in endometriosis by increasing the phosphorylation of Snail1. Additionally, PYK2 promotes the proliferation, migration, and invasion of endometriosis cells while inhibiting decidualization. We demonstrated that VS-6063 inhibited the proliferation, migration, and invasion of endometriosis cells in vitro, as well as the growth of endometriotic lesions in vivo.

PYK2 is a novel binding partner of Snail1. PYK2 promotes the occurrence and development of endometriosis by up-regulating Snail1, which could be a promising therapeutic target for endometriosis.