Overexpression of FOXS1 in gastric cancer cell lines inhibits proliferation, metastasis, and epithelial-mesenchymal transition of tumor through downregulating wnt/β-catenin pathway

Abstract

Background: Expression of forkhead box (FOX) superfamily members has been shown to be decreased in cancer, which was linked to poor prognosis of patients. The aim of this study was to investigate the expression of a new FOX superfamily member, FOXS1, in gastric cancer, and the influence of FOXS1 overexpression on the tumorigenesis of gastric cancer cells. The underlying molecular mechanism was also investigated.

Materials and methods: FOXS1 expression levels were firstly measured in 15 paired gastric cancer and peritumor tissue using quantitative polymerase chain reaction or immunohistochemistry. Secondly, FOXS1 overexpression models were established in two gastric cancer cell lines (SNU-216 and AGS) and FOXS1 knockdown model was established in SNU-638 gastric cancer cell line. Markers for cell proliferation, metastasis, cell cycle status, and wnt/β-catenin pathway were evaluated. Influence of FOXS1 overexpression on tumorigenesis was further evaluated in xenograft model.

Results: Expression of FOXS1 was significantly decreased in gastric cancer tissue in both messenger RNA and protein levels, compared with peritumor tissue. Our results showed that compared to cell lines transfected with negative control, gastric cancer cell lines with FOXS1 overexpression showed suppressed cell proliferation, metastasis, and increased ratio of G0/G1 phase. Xenograft model also showed suppressed tumor growth in FOXS1 overexpression group. Epithelial-mesenchymal transition was also inhibited when FOXS1 was overexpressed, which was indicated by an increase of E-cadherin expression and decrease in vimentin expression. Further investigation showed that expression of β-catenin was decreased, together with decreased expression in downstream signaling factors, c-Myc and cyclin-D1 in FOXS1 overexpression cell lines. On the other hand, knockdown of FOXS1 showed opposite trends in the changes of those markers for cell proliferation, metastasis, cell cycle status, and wnt/β-catenin pathway, compared with FOXS1 overexpression.

Conclusion: In conclusion, the present study showed that FOXS1 expression is downregulated in most GC cases in our cohort, and this loss of expression may promote cell proliferation and metastasis through upregulation of wnt/β-catenin pathway.

Keywords: FOXS1; forkhead box; gastric cancer; tumorigenesis; wnt/β-catenin pathway.