Decreased TOB1 expression and increased phosphorylation of nuclear TOB1 promotes gastric cancer

Methylation Mediated Downregulation of TOB1-AS1 and TOB1 Correlates with Malignant Progression and Poor Prognosis of Esophageal Squamous Cell Carcinoma

BACKGROUND

TOB1, a member of the transducer of erbB-2 /B-cell translocation gene family, was detected to be down-regulated in ESCC by RNA sequencing. TOB1-AS1, a head-to-head antisense lncRNA with TOB1, was down-regulated in several cancers. However, the roles of them in esophageal squamous cell carcinoma (ESCC) remained unclarified.

AIMS

To investigate the roles and functions of TOB1-AS1 and TOB1 in ESCC tumorigenesis.

MATERIALS AND METHODS

The expression levels, methylation status, biological function and mechanisms of TOB1-AS1 and TOB1 in ESCC were, respectively, detected.

RESULTS

Frequent down-regulation of TOB1-AS1 and TOB1 was verified in esophageal cancer cells and ESCC tissues, and there was a positive correlation between them in ESCC tissues. The CpG sites hypermethylation within proximal promoter of TOB1-AS1 and TOB1 could lead to transcriptional inhibition of both genes. Furthermore, expression and proximal promoter methylation status of TOB1-AS1 or TOB1 may be associated with ESCC patients' prognosis. TOB1-AS1 and TOB1 may function as tumor suppressors by inhibiting growth, migration, and invasion of esophageal cancer cells. Up-regulation of TOB1-AS1 increased expression level of TOB1, and TOB1-AS1 could work as a ceRNA to modulate ATF3 expression via competitively binding with miR-103a-2-5p. Meanwhile, ATF3, as a transcription factor, could regulate transcription of TOB1; down-regulation of TOB1-AS1 in ESCC led to decreased expression of ATF3 through ceRNA mechanism, and further influenced the transcription of TOB1.

CONCLUSION

TOB1-AS1 and TOB1 may act as tumor suppressors and may serve as potential targets for antitumor therapy in ESCC.

The Overexpression of TOB1 Induces Autophagy in Gastric Cancer Cells by Secreting Exosomes

We previously confirmed that transducer of ERBB2, 1 (TOB1) gene, can induce autophagy in gastric cancer cells. Studies have shown the biogenesis of exosomes overlaps with different autophagy processes, which helps to maintain the self-renewal and homeostasis of body cells. This study is aimed at verifying whether overexpressing TOB1 induces autophagy by secreting exosomes in gastric cancer cells and its underlying mechanisms. Differential ultracentrifugation was used to extracted the exosomes from the culture medium of gastric cancer cell line AGS-TOB1 ectopically overexpressing TOB1 (exo-AGS-TOB1, experimental group) and AGS-empty-vector cell line with low expression of endogenous TOB1 (exo-AGS-Vector, control group). Exosomal markers CD9 and TSG101 were determined in both the cell supernatants of exo-AGS-TOB1 and exo-AGS-Vector by Western blot. Under the transmission electron microscope (TEM), the exosomes were round and saucer-like vesicles with double-layer membrane structure, and the vesicles showed different translucency due to different contents. The peak size of exosomes detected by nanoparticle tracking analysis (NTA) was about 100 nm. When the exosomes of exo-AGS-TOB1 and exo-AGS-Vector were cocultured with TOB1 knockdown gastric cancer cell line HGC-27-TOB1-6E12 for 48 hours, the conversion of autophagy-related protein LC3-I to LC3-II in HGC-27-TOB1-6E12 gastric cancer cells cocultured with exo-AGS-TOB1 was significantly higher than that in the control group, and the ratio of LC3-II/LC3-I was statistically different (P < 0.05). More autophagosomes in HGC-27-TOB1-6E12 cells cocultured with exo-AGS-TOB1 for 48 hours were observed under TEM, while fewer autophagosomes were found in the control group. Lastly, miRNAs were differentially expressed by cell supernatant-exosomal whole transcriptome sequencing. Thus, our results provide new insights into TOB1-induced autophagy in gastric cancer.

Involvement of TOB1 on autophagy in gastric cancer AGS cells via decreasing the activation of AKT/mTOR signaling pathway

BACKGROUND

We previously identified the tumor suppressor gene TOB1 as related to gastric cancer. The purpose of this study was to explore whether TOB1 induces autophagy through the AKT/mTOR signaling pathway in gastric cancer.

METHODS

Western blotting was used to detect the protein levels of TOB1, LC3, AKT, mTOR, phosphorylated (p) AKT, and p-mTOR. A double fluorescent GFP-RFP-LC3 fusion protein was used to trace autophagy by laser confocal microscopy. Autophagosomes were observed by transmission electron microscopy.

RESULTS

The conversion of LC3-I to LC3-II and the LC3-II/LC3-I ratio were significantly increased in AGS cells overexpressing TOB1 compared with control cells. Fluorescence imaging showed LC3 puncta at 48 h, and these puncta increased significantly at 72 h after TOB1 transfection compared with control tumor cells. The presence of autophagosomes in AGS cells was observed at 72 h after TOB1 transfection by transmission electron microscopy, and no autophagosomes were found in the control cells. Moreover, the levels of p-AKT and p -mTOR were lower in AGS cells than in control cancer cells.

CONCLUSION

Our results provide novel insight that TOB1 might suppress gastric cancer by inducing autophagy, possibly through decreasing phosphorylation and the subsequent activation of the AKT/mTOR signaling pathway.

Key Regulatory Differentially Expressed Genes in the Blood of Atrial Septal Defect Children Treated With Occlusion Devices

Atrial septal defects (ASDs) are the most common types of cardiac septal defects in congenital heart defects. In addition to traditional therapy, interventional closure has become the main treatment method. However, the molecular events and mechanisms underlying the repair progress by occlusion device remain unknown. In this study, we aimed to characterize differentially expressed genes (DEGs) in the blood of patients treated with occlusion devices (metal or poly-L-lactic acid devices) using RNA-sequencing, and further validated them by qRT-PCR analysis to finally determine the expression of key mediating genes after closure of ASD treatment. The result showed that total 1,045 genes and 1,523 genes were expressed differently with significance in metal and poly-L-lactic acid devices treatment, respectively. The 115 overlap genes from the different sub-analyses are illustrated. The similarities and differences in gene expression reflect that the body response process involved after interventional therapy for ASDs has both different parts that do not overlap and the same part that crosses. The same portion of body response regulatory genes are key regulatory genes expressed in the blood of patients with ASDs treated with closure devices. The gene ontology enrichment analysis showed that biological processes affected in metal device therapy are immune response with CXCR4 genes and poly-L-lactic acid device treatment, and the key pathways are nuclear-transcribed mRNA catabolic process and proteins targeting endoplasmic reticulum process with ribosomal proteins (such as RPS26). We confirmed that CXCR4, TOB1, and DDIT4 gene expression are significantly downregulated toward the pre-therapy level after the post-treatment in both therapy groups by qRT-PCR. Our study suggests that the potential role of CXCR4, DDIT4, and TOB1 may be key regulatory genes in the process of endothelialization in the repair progress of ASDs, providing molecular insights into this progress for future studies.

Bioinformatic identification of differentially expressed genes associated with prognosis of locally advanced lymph node-positive prostate cancer

Prostate cancer (PCa) is one of the primary causes of cancer-related mortality in men worldwide. Patients with locally advanced PCa with metastases in regional lymph nodes are usually marked as a high-risk group. One of the chief concerns for this group is to make an informed decision about the necessity of conducting adjuvant androgen deprivation therapy after radical surgical treatment. During the oncogenic transformation and progression of the disease, the expression of many genes is altered. Some of these genes can serve as markers for diagnosis, predicting the prognosis or effectiveness of drug therapy, as well as possible therapeutic targets. We undertook bioinformatic analysis of the RNA-seq data deposited in The Cancer Genome Atlas consortium database to identify possible prognostic markers. We compared the groups with favorable and unfavorable prognosis for the cohort of patients with PCa showing lymph node metastasis (pT2N1M0, pT3N1M0, and pT4N1M0) and for the most common molecular type carrying the fusion transcript TMPRSS2-ERG. For the entire cohort, we revealed at least six potential markers (IDO1, UGT2B15, IFNG, MUC6, CXCL11, and GBP1). Most of these genes are involved in the positive regulation of immune response. For the TMPRSS2-ERG subtype, we also identified six genes, the expression of which may be associated with prognosis: TOB1, GALNT7, INAFM1, APELA, RAC3, and NNMT. The identified genes, after additional studies and validation in the extended cohort, could serve as a prognostic marker of locally advanced lymph node-positive PCa.

TOB1 suppresses proliferation in K-Ras wild-type pancreatic cancer

TOB1 participates in various kinds of cancers. However, its role in pancreatic cancer has rarely been reported. In this study, we explored the expression and mechanisms of TOB1 in regulating the malignant phenotype of pancreatic cancer cells. TOB1 expression was determined by data mining and immunohistochemistry (IHC), and its localization was observed by immunofluorescence. CCK‐8 cell proliferation, colony formation, flow cytometric, transwell migration, and Western blot (WB) assays were used to examine how it impacts the malignant phenotype of pancreatic cancer. Furthermore, Foxa2 binding to TOB1 was tested by dual‐luciferase reporter assays, and RNA‐Seq was performed to identify signaling pathways. We found TOB1 was downregulated in pancreatic cancer tissues and was mainly located in the cytoplasm. TOB1 overexpression reduced the proliferation of K‐Ras wild‐type pancreatic cancer cells but made no difference to cell migration and invasion. Foxa2 overexpression significantly enhanced TOB1 promoter activity. Moreover, overexpressing TOB1 substantially enriched the calcium pathway in K‐Ras wild‐type pancreatic cancer cells. In conclusion, TOB1 may suppress the proliferation of K‐Ras wild‐type pancreatic cancer cells by regulating calcium pathway genes.

Phosphorylation of TOB1 at T172 and S320 is critical for gastric cancer proliferation and progression

We previously revealed that increased phosphorylation of TOB1, a tumor suppressor protein, may promote the progression of gastric cancer. However, the phosphorylated sites on TOB1 and their functional implication in gastric cancer remain to be clarified. Here, we addressed these questions using the gastric mucosal epithelial cell line GES-1 and three gastric cancer cell lines (HGC-27, AGS, and MKN-1). Compared with the control GES-1 cells, the gastric cancer cells showed decreased levels of TOB1 protein and increased levels of phosphorylated TOB1 (p-TOB1) by Western blotting. Then, TOB1 protein was enriched and purified by immunoprecipitation. Two novel phosphorylation sites at threonine 172 (T172) and serine 320 (S320) in TOB1 were identified in gastric cancer MKN-1 cells using LC-MS/MS. Furthermore, treatment with the serine/threonine kinase inhibitor staurosporine (STS; 2 nmol/L, 8 h) significantly decreased the levels of p-TOB1. As a result, the proliferation, migration, and invasion of gastric cancer cells were diminished, accompanied by an increased proportion of cells in G1 phase and a decreased proportion of cells in G2 phase. Taken together, these findings indicate for the first time that TOB1 is phosphorylated at T172 and S320 in gastric cancer cells, which are sensitive to STS. Downregulation of p-TOB1 levels by STS treatment can weaken the malignant phenotype of gastric cancer cells and block their progression through the cell cycle. Moreover, STS may exert its antiproliferative activity in gastric cancers by restoring TOB1 protein activity.

Decreased expression levels of DAL-1 and TOB1 are associated with clinicopathological features and poor prognosis in gastric cancer

PURPOSE

We previously demonstrated that the functional inactivation of DAL-1 and TOB1 promotes an aggressive phenotype in gastric cancer cells, but the links between both genes and the survival of patients with gastric cancer are unknown. Here, we investigated the correlations of the expression levels of DAL-1 and TOB1 with the progression of gastric cancer.

METHODS

A total of 270 patients who underwent resectable gastrectomy were included. The expression of DAL-1 and TOB1 was detected by immunohistochemistry.

RESULTS

Low expression of DAL-1 in cancer tissue was significantly associated with tumor site (p < 0.05), histological grade (p < 0.01), depth of invasion (p < 0.05), lymph node metastasis status (p < 0.05), Lauren classification (p < 0.001), and clinical stage (p < 0.01). A lower level of TOB1 was observed in gastric cancer patients with diffuse type disease compared to patients with either intestinal or mixed type disease (p < 0.001). Additionally, Spearman's correlation analysis revealed that decreased expression of DAL-1 was positively correlated with low TOB1 expression (r=0.304, p < 0.001). The survival analysis showed that low levels of DAL-1 and TOB1 were significantly associated with poor survival of gastric cancer patients (p <0.001 and p < 0.05, respectively).

CONCLUSION

The downregulation of DAL-1 and TOB1 expression is associated with shorter survival of gastric cancer patients. Hence, DAL-1 and TOB1 may be considered potential novel markers for predicting the outcomes of patients with gastric cancer.

Nuclear ERK: Mechanism of Translocation, Substrates, and Role in Cancer

The extracellular signal-regulated kinases 1/2 (ERK) are central signaling components that regulate stimulated cellular processes such as proliferation and differentiation. When dysregulated, these kinases participate in the induction and maintenance of various pathologies, primarily cancer. While ERK is localized in the cytoplasm of resting cells, many of its substrates are nuclear, and indeed, extracellular stimulation induces a rapid and robust nuclear translocation of ERK. Similarly to other signaling components that shuttle to the nucleus upon stimulation, ERK does not use the canonical importinα/β mechanism of nuclear translocation. Rather, it has its own unique nuclear translocation signal (NTS) that interacts with importin7 to allow stimulated shuttling via the nuclear pores. Prevention of the nuclear translocation inhibits proliferation of B-Raf- and N/K-Ras-transformed cancers. This effect is distinct from the one achieved by catalytic Raf and MEK inhibitors used clinically, as cells treated with the translocation inhibitors develop resistance much more slowly. In this review, we describe the mechanism of ERK translocation, present all its nuclear substrates, discuss its role in cancer and compare its translocation to the translocation of other signaling components. We also present proof of principle data for the use of nuclear ERK translocation as an anti-cancer target. It is likely that the prevention of nuclear ERK translocation will eventually serve as a way to combat Ras and Raf transformed cancers with less side-effects than the currently used drugs.

Association between the SNPs of the TOB1 gene and gastric cancer risk in the Chinese Han population of northeast China

The TOB1 (ErbB-2,1) gene is an anti-proliferative factor that has the potential to regulate cell growth and encodes a member of the transducer of erbB-2/B-cell translocation gene protein. The association between the polymorphisms of the TOB1 gene and gastric cancer (GC) risk is still unclear. In this study, 506 GC cases and 548 healthy controls (HCs) were collected to evaluate the association between the eleven SNPs (rs35220381, rs12950561, rs7221352, rs61482741, rs9303568, rs34700818, rs12949115, rs9903822, rs12601477, rs11656976 and rs4626) of the TOB1 gene and GC risk in the population of northeast China. The results showed that there were significant associations of haplotype GCCTTGC, haplotype ATCTTGG, and haplotype GCCACGC with GC risk (P < 0.05, P < 0.001, and P <0.001, respectively). The association between rs12601477 GA+AA genotypes and GC risk was significant among individuals older than 58 (adjusted OR=1.53, 95% CI=1.05-2.22, P< 0.05). The association between rs4626 AG+GG genotypes and GC risk was significant among individuals older than 58 (adjusted OR=1.54, 95% CI = 1.03-2.28, P<0.05). The rs34700818 CT+TT genotypes were associated with a significantly increased risk of T3-T4 (CT+TT vs CC, adjusted OR=1.71, 95% CI= 1.01-2.88, P<0.05) and TNM stage II (CT+TT vs CC, adjusted OR=2.40, 95% CI =1.27-4.52, P<0.01). The rs61482741 CG+GG genotypes were also associated with a significantly increased risk of T3-T4 (CG+GG vs CC, adjusted OR=1.71, 95% CI = 1.01-2.88, P<0.05) and TNM stage II (CG+GG vs CC, adjusted OR=2.40, 95% CI=1.27-4.52, P<0.01). The results suggest that four SNPs (rs12601477, rs4626, rs34700818 and rs61482741) of the TOB1 gene play an important role in the occurrence and development of GC in the Chinese Han population of northeast China.