Plakoglobin (c-catenin) is a homolog of b-catenin with similar dual adhesive and signaling functions. The adhesive function of these proteins is mediated by their interactions with cadherins, whereas their signaling activity is regulated by association with various intracellular partners. In this respect, b-catenin has a well-defined oncogenic activity through its role in the Wnt signaling pathway, whereas plakoglobin acts as a tumor/metastasis suppressor through mechanisms that remain unclear. We previously expressed plakoglobin in SCC9 squamous carcinoma cells (SCC9-P) and observed a mesenchymalto-epidermoid transition. Comparison of the protein and RNA profiles of parental SCC9 cells and SCC9-P transfectants identified various differentially expressed proteins and transcripts, including the nonmetastatic protein 23 (Nm23). In this study, we show that Nm23-H1 mRNA and Nm23-H2 protein are increased after plakoglobin expression. Coimmunoprecipitation and confocal microscopy studies using SCC9-P and various epithelial cell lines with endogenous plakoglobin expression revealed that Nm23 interacts with plakoglobin, cadherins and a-catenin. Furthermore, Nm23-H2 is the primary isoform involved in these interactions, which occur prominently in the cytoskeleton-associated pool of cellular proteins. In addition, we show that plakoglobinNm23 interaction requires the N-terminal (a-catenin interacting) domain of plakoglobin. Our data suggest that by increasing the expression and stability of Nm23, plakoglobin has a role in regulating the metastasis suppressor activity of Nm23, which may further provide a potential mechanism for the tumor/metastasis suppressor function of plakoglobin itself.

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Gastric cancer (GC) is one of the most common cancers in the world. The cathepsin F (CTSF) gene has recently been found to participate in the progression of several types of cancer. However, the clinical characteristics and function of CTSF in GC as well as its molecular mechanisms are not clear. Six GC cell lines and 44 paired adjacent noncancerous and GC tissue samples were used to assess CTSF expression by quantitative polymerase chain reaction (qPCR). We used lentivirus-mediated small hairpin RNA (Lenti-shRNA) against CTSF to knock down the expression of CTSF in GC cells. Western blot and qPCR were used to analyze the mRNA and related protein expression. The biological phenotypes of gastric cells were examined by cell proliferation and apoptosis assays. Microarray-based mRNA expression profile screening was also performed to evaluate the potential molecular pathways in which CTSF may be involved. The CTSF mRNA level was associated with tumor differentiation, depth of tumor invasion, and lymph node metastasis. Downregulation of CTSF expression efficiently inhibited apoptosis and promoted the proliferation of GC cells. Moreover, a total of 1,117 upregulated mRNAs and 1,143 downregulated mRNAs were identified as differentially expressed genes (DEGs). Further analysis identified the involvement of these mRNAs in cancer-related pathways and various other biological processes. Nine DEGs in cancer-related pathways and three downstream genes in the apoptosis pathway were validated by Western blot, which was mainly in agreement with the microarray data. To our knowledge, this is the first report investigating the effect of CTSF on the growth and apoptosis in GC cells and its clinical significance. The CTSF gene may function as a tumor suppressor in GC and may be a potential therapeutic target in the treatment of GC.

HtrA serine peptidase 3 (HTRA3) participates in multiple signal pathways and plays an important regulatory role in various malignancies; however, its role on prognosis and immune infiltrates in gastric cancer (GC) remains unclear. The study investigated HTRA3 expression in tumor tissues and its association with immune infiltrates, and determined its prognostic roles in GC patients. Patients with GC were collected from the cancer genome atlas (TCGA). We compared the expression of HTRA3 in GC and normal gastric mucosa tissues with Wilcoxon rank sum test. And logistic regression was used to evaluate the relationship between HTRA3 and clinicopathological characters. Gene ontology (GO) term analysis, Gene set enrichment analysis (GSEA), and single-sample Gene Set Enrichment Analysis (ssGSEA) was conducted to explain the enrichmental pathways and functions and quantify the extent of immune cells infiltration for HTRA3. Kaplan-Meier analysis and Cox regression were performed to evaluate the correlation between HTRA3 and survival rates. A nomogram, based on Cox multivariate analysis, was used to predict the impact of HTRA3 on prognosis. High HTRA3 expression was significantly correlated with tumor histological type, histological grade, clinical stage, T stage, and TP53 status (P < 0.05). HTRA3-high GC patients had a lower 10-year progression-free interval [PFI; hazard ratio (HR): 1.46; 95% confidence interval (CI): 1.02–2.08; P = 0.038], disease-specific survival (DSS; HR: 1.65; CI: 1.08–2.52; P = 0.021) and overall survival (OS; HR: 1.59; CI: 1.14–2.22; P = 0.006). Multivariate survival analysis showed that HTRA3 was an independent prognostic marker for PFI (HR: 1.456; CI: 1.021–2.078; P = 0.038), DSS (HR: 1.650; CI: 1.079–2.522; P = 0.021) and OS [hazard ratio (HR): 1.590; 95% confidence interval (CI):1.140–2.219; P = 0.006]. The C-indexes and calibration plots of the nomogram based on multivariate analysis indicated an effective predictive performance for GC patients. GSEA showed that High HTRA3 expression may activate NF-κB pathway, YAP1/WWTR1/TAZ pathway, and TGFβ pathway. There was a negative correlation between the HTRA3 expression and the abundances of adaptive immunocytes (T helper cell 17 cells) and a positive correlation with abundances of innate immunocytes (natural killer cells, macrophages etc.). HTRA3 plays a vital role in GC progression and prognosis and could be a moderate biomarker for prediction for survival after gastrectomy.

Tumor metastasis remains the main cause of breast cancer-related deaths, especially delayed breast cancer distant metastasis. The current study assessed the frequency of CD44-/CD24- breast cancer cells in 576 tissue specimens for associations with clinicopathological features and metastasis and investigated the underlying molecular mechanisms. The results indicated that higher frequency (≥19.5%) of CD44-/CD24- cells was associated with delayed postoperative breast cancer metastasis. Furthermore, CD44-/CD24- triple negative breast cancer (TNBC) cells spontaneously converted into CD44+/CD24- cancer stem cells (CSCs) with properties similar to CD44+/CD24- CSCs from primary human breast cancer cells and parental TNBC cells in terms of stemness marker expression, self-renewal, differentiation, tumorigenicity and lung metastasis in vitro and in NOD/SCID mice. RNA sequencing identified several differentially expressed genes (DEGs) in newly converted CSCs and RHBDL2, one of the DEGs, expression was up-regulated. More importantly, RHBDL2 silencing inhibited the YAP1/USP31/NF-κB signaling and attenuated spontaneous CD44-/CD24- cell conversion into CSCs and their mammosphere formation. These findings suggest that the frequency of CD44-/CD24- tumor cells and RHBDL2 may be valuable for prognosis of delayed breast cancer metastasis, particularly for TNBC.