Ubiquitin-specific protease 15 contributes to gastric cancer progression by regulating the Wnt/β-catenin signaling pathway.

Ubiquitin-specific protease 15 (USP15) is an important member of the ubiquitin-specific protease family, the largest deubiquitinase subfamily, whose expression is dysregulated in many types of cancer. However, the biological function and the underlying mechanisms of USP15 in gastric cancer (GC) progression have not been elucidated. To explore the biological role and underlying mechanisms of USP15 in GC progression. Bioinformatics databases and western blot analysis were utilized to determine the expression of USP15 in GC. Immunohistochemistry was performed to evaluate the correlation between USP15 expression and clinicopathological characteristics of patients with GC. A loss- and gain-of-function experiment was used to investigate the biological effects of USP15 on GC carcinogenesis. RNA sequencing, immunofluorescence, and western blotting were performed to explore the potential mechanism by which USP15 exerts its oncogenic functions. USP15 was up-regulated in GC tissue and cell lines. The expression level of USP15 was positively correlated with clinical characteristics (tumor size, depth of invasion, lymph node involvement, tumor-node-metastasis stage, perineural invasion, and vascular invasion), and was related to poor prognosis. USP15 knockdown significantly inhibited cell proliferation, invasion and epithelial-mesenchymal transition (EMT) of GC in vitro, while overexpression of USP15 promoted these processes. Knockdown of USP15 inhibited tumor growth in vivo. Mechanistically, RNA sequencing analysis showed that USP15 regulated the Wnt signaling pathway in GC. Western blotting confirmed that USP15 silencing led to significant down-regulation of β-catenin and Wnt/β-catenin downstream genes (c-myc and cyclin D1), while overexpression of USP15 yielded an opposite result and USP15 mutation had no change. Immunofluorescence indicated that USP15 promoted nuclear translocation of β-catenin, suggesting activation of the Wnt/β-catenin signaling pathway, which may be the critical mechanism promoting GC progression. Finally, rescue experiments showed that the effect of USP15 on gastric cancer progression was dependent on Wnt/β-catenin pathway. USP15 promotes cell proliferation, invasion and EMT progression of GC via regulating the Wnt/β-catenin pathway, which suggests that USP15 is a novel potential therapeutic target for GC.

Zhong M ，Zhou L ，Fang Z ，Yao YY ，Zou JP ，Xiong JP ，Xiang XJ ，Deng J ... -  《-》

Ubiquitin-like modifier activating enzyme 2 promotes cell migration and invasion through Wnt/β-catenin signaling in gastric cancer.

Li J ，Sun X ，He P ，Liu WQ ，Zou YB ，Wang Q ，Meng XW ... -  《-》

MiR-675 is frequently overexpressed in gastric cancer and enhances cell proliferation and invasion via targeting a potent anti-tumor gene PITX1.

Gastric cancer (GC) is a common malignancy around the world. Irregular expression of microRNAs (miRNAs) contributes to the progression of malignancies. Our study illustrated that miR-675 facilitates GC proliferation and invasion via targeting paired-like homeodomain transcription factor 1 (PITX1) and promoting epithelial-mesenchymal transition (EMT) as well as Wnt/β-catenin signaling pathway. We collected the RNA-seq data of GC and normal stomach tissues from TCGA database to analyze the expression of miR-675 and PITX1. Kaplan-Meier plotter on line tool was used to analyze the association between miR-675 or PITX1 expression and the overall survival of GC patients. The biological function of miR-675 in GC cells was evaluated via altering its expression using miR-675 agomiR or antamiR. Dual-luciferase reporter assay was applied for verifying whether miR-675 could direct bind to 3'UTR of PITX1. Rescue assays were applied for characterizing the effects of miR-675/PITX1 axis on GC growth and invasion. Western blot was performed to evaluate the protein expression levels of PITX1, EMT-related and Wnt signaling-related proteins. Our results showed that miR-675 is up-regulated and predictive of worse prognosis in GC patients. Overexpression of miR-675 in AGS cells notably promoted cell proliferation, migration and invasion, whilst down-regulation of miR-675 in SGC-7901 cells gained the opposite results. PITX1 is down-regulated in GC and identified as a direct target of miR-675. Overexpression of PITX1 in AGS cells reverses cell viability and invasion that enhanced by miR-675 up-regulation. Conversely, depletion of PITX1 in SGC-7901 cells rescues cell viability and invasion that inhibited by miR-675 down-regulation. Western bolt results revealed that miR-675 positively regulated EMT and Wnt/β-catenin signaling pathway in GC cells via targeting PITX1. Our study emphasized the functional mechanism of miR-675 in GC and intimated that miR-675/PITX1 axis possibly affects proliferative and invasive properties of GC cells via regulating EMT and Wnt/β-catenin signaling pathway. Furthermore, miR-675 and PITX1 may be served as early diagnostic markers as well as therapeutic targets for GC.

Liu L ，Tian YC ，Mao G ，Zhang YG ，Han L ... -  《-》

KLF3 Transcription Activates WNT1 and Promotes the Growth and Metastasis of Gastric Cancer via Activation of the WNT/β-Catenin Signaling Pathway.

The transcription factor Krüppel-like factor (KLF) 3 is one of the members of the KLF family, which plays an important role in tumor progression. Nevertheless, the role of KLF3 in the growth and metastasis of gastric cancer (GC) still needs to be elucidated. Bioinformatics analysis showed that KLF3 was overexpressed in patients with GC, and the high expression of KLF3 was correlated with poor survival. KLF3 was also overexpressed in GC clinical samples and cell lines. In vitro functional role of KLF3 in GC cells was explored by a gain-of-function and loss-of-function assay. Overexpressed KLF3 promoted the cell proliferation, migration, invasion, and epithelial-mesenchymal transition of GC cells, whereas suppressed KLF3 inhibited these biological behaviors. The clinical samples and bioinformatics analysis showed that WNT1 was also highly expressed in GC tumor tissues and positively correlated with KLF3 expression. The luciferase reporter assay and chromatin immunoprecipitation result confirmed that KLF3 could directly bind to the WNT1 promoter to increase the transcriptional activity of WNT1, thus regulating its expression. Overexpressed KLF3 enhanced the protein expression level of p-GSK3β(Ser9) and β-catenin, the key elements in the WNT/β-catenin signaling pathway. Repression of KLF3 decreased the level of p-GSK3β(Ser9) and β-catenin. Immunofluorescence images showed that KLF3 promoted nuclear β-catenin accumulation. Inhibition of WNT1 attenuated the proliferation, migration, and invasiveness of KLF3-overexpressing GC cells. Moreover, the xenograft mouse model confirmed that KLF3 promotes GC tumor growth and metastasis in vivo. Our results demonstrated that KLF3 activates the WNT/β-catenin signaling pathway via WNT1 to promote GC tumor growth and metastasis, indicating that repression of KLF3 may act as a potential therapeutic target for patients with GC.

Li Y ，Wang Y ，Zou Q ，Li S ，Zhang F ... -  《-》

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

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. 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. 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. 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.

Lu Q ，Ma X ，Li Y ，Song W ，Zhang L ，Shu Y ，Wan B ... -  《-》