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Purpose: Follistatin-related gene 3 (FSTL3), an established oncogene, can modulate target gene expression via members of the transforming growth factor β (TGF-β) superfamily. The present study was conducted to evaluate the expression of FSTL3 in gastric cancer (GC) and to determine its prognostic significance. We also evaluated the possible mechanisms involved in the oncogenic role of FSTL3 in gastric carcinogenesis and development. Methods: We obtained data from the Human Protein Atlas, MethSurv, cBioPortal, UALCAN, TIMER, GEPIA, STRING, GeneMANIA, ONCOMINE, and MEXPRESS databases and examined it using R software. RNAi was used to establish stable FSTL3-knockdown (shFSTL3) and overexpression (OE) cell strains. Western blot; enzyme-linked immunosorbent (ELISA); and immunohistochemical (ICH), immunofluorescence, and phalloidin staining were used for examining protein expression. Cell invasion and migration were determined using transwell and scratch-wound assays. After tumor-associated macrophage (TAM) generation, co-culturing of cancer cells with TAMs was performed to confirm the relationship between FSTL3 and TAMs. Results: In GC patients, FSTL3 mRNA and protein levels were upregulated. FSTL3 expression was significantly linked to cancer stage as well as to pathological tumor grade in GC. Moreover, a high expression of FSTL3 was associated with a dismal survival duration in patients with GC. Furthermore, functional enrichment analysis demonstrated that FSTL3 overexpression could activate epithelial–mesenchymal transition (EMT) by promoting F-actin expression and BMP/SMAD signaling. Finally, immunofluorescence staining confirmed that the overexpression of FSTL3 promoted the proliferation of M2 TAMs. Conclusion: Taken together, our findings suggest that FSTL3 may be involved in GC progression via the promotion of BMP/SMAD signaling-mediated EMT and M2 macrophage activation. [ABSTRACT FROM AUTHOR]

Purpose: Emerging evidence has shown that long noncoding RNAs (lncRNAs) participate in oncogenesis and tumor progression. We previously found a novel lncRNA p4516 which was closely associated with prognosis by preliminary study of lncRNA expression profile from paired tumors and nontumor tissues in 198 gastric cancer (GC) patients. However, the exact biological functions and the underlying molecular mechanisms of p4516 in gastric tumorigenesis still remain unclear. Materials and methods: The RNA fluorescence in situ hybridization (RNA-FISH) analysis, cytoplasmic and nuclear RNA isolation and qRT-PCR were applied to determine the subcellular localization of p4516. Expression levels of p4516 were assessed using qRT-PCR in both GC cell lines and in 142 primary GC tissues. Correlations between p4516 expression and GC patients' clinicopathological parameters were analyzed. Gain- and loss-of-function experiments were employed to investigate the role of p4516 in proliferation, migration and invasion both in vitro and in vivo. In addition, Western blotting and immunohistochemical staining were used to examine the protein expression levels. Results: LncRNA p4516 was mainly localized in the nucleus of GC cells and p4516 tended to have higher expression levels in GC cells compared to the normal gastric mucosa-derived cells GES-1. Furthermore, higher expression levels of p4516 correlated with worse clinical outcomes in GC patients and acted as an independent prognostic biomarker. Functional analysis revealed that p4516 participated in the regulation of GC cell proliferation, invasion and migration both in vivo and in vitro. Moreover, p4516 was involved in epithelial–mesenchymal transition (EMT) in GC cells. Conclusion: Our study demonstrated the oncogenic role of novel lncRNA p4516 in the gastric carcinogenesis for the first time. High expression of p4516 may act as prognostic marker in patient with gastric cancer. [ABSTRACT FROM AUTHOR]