The Role Of FSTL1 In Regulation Of Epithelial-Mesenchymal Transition And Cell Stemness In Ovarian Cancer Cells

Ovarian cancer is the most common and most fatal gynecologic tumor.The lack of effective diagnosis and treatment is the main reason leading to the death of women.The current clinical treatment of ovarian cancer is mainly surgical treatment combined with postoperative chemotherapy.Postoperative recurrence and chemotherapy resistance make it difficult to ensure the patients’ quality of life,so it is particularly urgent to seek new treatments for ovarian cancer.Follistatin-like protein 1(FSTL1)is a secreted cysteine-rich acidic protein with a variety of biological functions.In recent years,there have been preliminary studies on FSTL1 in various diseases and tumors,but its mechanism in tumorigenesis and development remains unclear.Therefore,the study of FSTL1 and its mechanism of action may provide new ideas for the treatment of tumors.Our previous studies have shown that Notch3 signaling pathway mediates PTH-mediated epithelial-mesenchymal transition and cell stemness in ovarian cancer cells.Later we found that PTH can promote the expression of FSTL1 in ovarian cancer cells.Based on previous studies,this study aims to explore the effect of FSTL1 on metastasis and recurrence of ovarian cancer,and to reveal the role of FSTL1 in the regulation of epithelial-mesenchymal transition and stem cell stemness in ovarian cancer cells.Firstly,we examined the effect of PTH on FSTL1 expression in ovarian cancer cells at the protein level.By using PTH on ovarian cancer cells,Western blot analysis revealed that PTH can promote the expression of FSTL1 in ovarian cancer cells.Next,we analyzed the function of FSTL1 in tumor progression through Western blot,cell clone formation experiments,cell wound healing experiments,cell invasion experiments,and microsphere formation experiments.We found that:1)Up-regulation of FSTL1 expression and adding recombinant protein rhFSTL1 can significantly promote the EMT process of ovarian cancer cells,while down-regulating FSTL1 results are reversed;2)Up-regulation of FSTL1 can promote cell colony formation rate;3)Up-regulation of FSTL1 can promote the migration and invasion ability of ovarian cancer cells;4)Up-regulation of FSTL1 and adding recombinant protein rhFSTL1 can significantly promote the proliferation of ovarian cancer cells;down-regulation of FSTL1 inhibits the proliferation of ovarian cancer cells;5)Up-regulation of FSTL1 can enhance the cell stemness of ovarian cancer cells.This part of the experimental results shows that FSTL1 is a carcinogenic factor in ovarian cancer cells,and promotes the EMT process and cell stemness of ovarian cancer cells.To further explore the molecular mechanism of FSTL1 function in ovarian cancer cells,we constructed an ovarian cancer cell line with low expression of Notch3.Through Western blot,cell growth experiments,cell clone formation experiments,etc.to explore the regulation mechanism of FSTL1 in Notch3 signaling pathway.We found that: 1)Downregulation of Notch3 protein can inhibit the EMT process and cell stemness of ovarian cancer cells;2)Downregulation of Notch3 protein can inhibit the proliferation and colony formation of ovarian cancer cells.This part of the results shows that FSTL1 can play a role through mediation of Notch3 signaling pathway.In summary,FSTL1 can participate in the occurrence and development of ovarian cancer,stem cell formation and EMT process through Notch3 signal transduction pathway,and regulate cell proliferation,differentiation and apoptosis.Therefore,targeted therapy for FSTL1 may provide a new approach for the clinical treatment of metastasis and recurrence of ovarian cancer.