Ying-Chao Wang

Roles of STAT3 and ZEB1 Proteins in E-cadherin Down-regulation and Human Colorectal Cancer Epithelial-Mesenchymal Transition

Background: Colorectal cancer (CRC) to metastatic disease may involve the epithelial-mesenchymal transition (EMT). Results: STAT3 may regulate N-cadherin, vimentin, and ZEB1 expressions. STAT3-induced cell invasion and down-regulation of E-cadherin may depend on ZEB1. Conclusion: STAT3 may mediate CRC EMT progression and ZEB1 expression. Activation of STAT3 and ZEB1 proteins may contribute to worse prognosis in CRC patients. Significance: Our data may provide potential targets to prevent and/or treat CRC invasion. The progression of colorectal carcinoma (CRC) to invasive and metastatic disease may involve localized occurrences of epithelial-mesenchymal transition (EMT). However, mechanisms of the EMT process in CRC progression are not fully understood. We previously showed that knockdown of signal transducer and activator of transcription 3 (STAT3) up-regulated E-cadherin (a key component in EMT progression) in CRC. In this study, we examined the roles of STAT3 in CRC EMT and ZEB1, an EMT inducer, in STAT3-induced down-regulation of E-cadherin. Knockdown of STAT3 significantly increased E-cadherin and decreased N-cadherin and vimentin expressions in highly invasive LoVo CRC cells. Meanwhile, overexpression of STAT3 significantly reduced E-cadherin and enhanced N-cadherin and vimentin expressions in weakly invasive SW1116 CRC cells. Activation of STAT3 significantly increased CRC cell invasiveness and resistance to apoptosis. Knockdown of STAT3 dramatically enhanced chemosensitivity of CRC cells to fluorouracil. STAT3 regulated ZEB1 expression in CRC cells, and the STAT3-induced decrease in E-cadherin and cell invasion depended on activation of ZEB1 in CRC cells. Additionally, pSTAT3Tyr-705 and ZEB1 expressions were significantly correlated with TNM (tumor, lymph node, and metastasis stages) (p < 0.01). In conclusion, STAT3 may directly mediate EMT progression and regulate ZEB1 expression in CRC. ZEB1 may participate in STAT3-induced cell invasion and E-cadherin down-regulation in CRC cells. The expressions of pSTAT3Tyr-705 and ZEB1 may be positively associated with CRC metastasis. Our data may provide potential targets to prevent and/or treat CRC invasion and metastasis.

Long Noncoding RNA GAPLINC Regulates CD44-Dependent Cell Invasiveness and Associates with Poor Prognosis of Gastric Cancer

It is increasingly evident that long noncoding RNAs (lncRNA) have causative roles in carcinogenesis. In this study, we report findings implicating a novel lncRNA in gastric cancer, termed GAPLINC (gastric adenocarcinoma predictive long intergenic noncoding RNA), based on the use of global microarray and in situ hybridization (ISH) analyses to identify aberrantly expressed lncRNA in human gastric cancer specimens. GAPLINC is a 924-bp-long lncRNA that is highly expressed in gastric cancer tissues. GAPLINC suppression and with gene expression profiling in gastric cancer cells revealed alterations in cell migration pathways, with CD44 expression the most highly correlated. Manipulating GAPLINC expression altered CD44 mRNA abundance and the effects of GAPLINC on cell migration and proliferation were neutralized by suppressing CD44 expression. Mechanistic investigations revealed that GAPLINC regulates CD44 as a molecular decoy for miR211-3p, a microRNA that targets both CD44 and GAPLINC. Tissue ISH analysis suggested that GAPLINC overexpression defines a subgroup of patients with gastric cancer with very poor survival. Taken together, our results identify a noncoding regulatory pathway for the CD44 oncogene, shedding new light on the basis for gastric cancer cell invasiveness.

MiR-29a Inhibits Cell Proliferation and Induces Cell Cycle Arrest through the Downregulation of p42.3 in Human Gastric Cancer

As a newly identified and characterized gene, p42.3 is associated with cell proliferation and tumorigenicity. The expression of p42.3 is upregulated in human gastric cancer (GC), but its underlying mechanisms of action are not well understood. MicroRNAs (miRNAs) are known to play vital regulatory roles in many cellular processes. Here we utilized bioinformatics and experimental approaches to investigate the regulatory relationship between miRNAs and the p42.3 gene. We showed that miR-29a could repress p42.3 expression at both the mRNA and protein levels via directly binding to its 3’UTR. Furthermore, an inverse relationship was observed between miR-29a and p42.3 expression in gastric cancer cell lines and GC tissue samples, especially in cases where p42.3 was downregulated. Taken together, we have elucidated previously unrecognized roles of miR-29a and indicated that miR-29a may function, at least partially, by targeting the p42.3 gene in human GC.

A Meta-Analysis of Interleukin-10 -592 Promoter Polymorphism Associated with Gastric Cancer Risk

We aimed to explore the role of IL-10 -592 A/C SNP in the susceptibility to gastric cancer through a systematic review and meta-analysis. Each initially included article was scored for quality appraisal. 17 studies were eligible for the meta-analysis. We adopted the most probably appropriate genetic model (recessive model). Potential sources of heterogeneity were sought out via subgroup and sensitivity analyses, and publication biases were estimated. IL-10-592 AA genotype is associated with the reduced risk of developing gastric cancer among Asians and even apparently observed among Asians high quality subgroup, suggesting IL-10-592 AA genotype may seem to be more protective from overall gastric cancer in Asian populations. IL-10-592 AA genotype is also associated with the overall reduced gastric cancer susceptibility in persons with H. pylori infection compared with controls without H. pylori infection, suggesting IL-10-592 AA genotype may seem to be more protective from overall gastric cancer susceptibility in persons infected with H. pylori. IL-10-592 AA genotype is not associated with either pathologic subtypes (intestinal or diffuse) or anatomic subtypes (non-cardia or cardia) of gastric cancer susceptibility. Genotyping methods like direct sequencing should be highly advocated to be conducted in future well-designed high quality studies among different ethnicities or populations.

Trichostatin A, a histone deacetylase inhibitor, suppresses JAK2/STAT3 signaling via inducing the promoter-associated histone acetylation of SOCS1 and SOCS3 in human colorectal cancer cells

Aberrant janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling is involved in the oncogenesis of several cancers. Suppressors of cytokine signaling (SOCS) genes and SH2‐containing protein tyrosine phosphatase 1 (SHP1) proteins, which are negative regulators of JAK/STAT signaling, have been reported to have tumor suppressor functions. However, in colorectal cancer (CRC) cells, the mechanisms that regulate SOCS and SHP1 genes, and the cause of abnormalities in the JAK/STAT signaling pathway, remain largely unknown. The present study shows that trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, leads to the hyperacetylation of histones associated with the SOCS1 and SOCS3 promoters, but not the SHP1 promoter in CRC cells. This indicates that histone modifications are involved in the regulation of SOCS1 and SOCS3. Moreover, upregulation of SOCS1 and SOCS3 expression was achieved using TSA, which also significantly downregulated JAK2/STAT3 signaling in CRC cells. We also demonstrate that TSA suppresses the growth of CRC cells, and induces G1 cell cycle arrest and apoptosis through the regulation of downstream targets of JAK2/STAT3 signaling, including Bcl‐2, survivin and p16ink4a. Therefore, our data demonstrate that TSA may induce SOCS1 and SOCS3 expression by inducing histone modifications and consequently inhibits JAK2/STAT3 signaling in CRC cells. These results also establish a mechanistic link between the inhibition of JAK2/STAT3 signaling and the anticancer action of TSA in CRC cells. Mol. Carcinog.

Constitutive activation of STAT3 is predictive of poor prognosis in human gastric cancer.

Abnormalities in signal transducer and activator of transcription (STAT) signaling, especially STAT3 and STAT5, are involved in the oncogenesis of several human cancers, including gastric cancer (GC). However, the downstream targets of STAT3 and STAT5 are not fully identified, and the precise roles and the prognostic value of STAT3 and STAT5 in GC have not been fully characterized. In this study, we used ChIP-on-chip to identify STAT3 and STAT5 target genes on a whole genome scale in AGS cells, a human GC cell line. A total of 2,514 and 1,314 genes were identified as STAT3 and STAT5 target genes, which were mainly related to cell growth, metabolism, differentiation, adhesion, immune response, and stress response. Furthermore, we depleted STAT3 and STAT5 with a small interfering RNA, respectively. Our results demonstrate that STAT3, but not STAT5, is involved in GC cell growth and cell cycle progression through regulation of gene expression, such as Bcl-2, p16ink4a and p21waf1/cip1. Moreover, expression of pSTAT3Tyr705 correlates with TNM stage, differentiation and survival, and is a significant prognostic factor in GC. Therefore, our findings provide novel evidence that STAT3 may be a potential therapeutic target for GC treatment and pSTAT3Tyr705 expression can predict prognosis in GC.

Knockdown of ZFX inhibits gastric cancer cell growth in vitro and in vivo via downregulating the ERK-MAPK pathway.

Zinc finger protein X-linked (ZFX) is a zinc finger transcription factor encoded on the X chromosome. Here, we found that ZFX expression was significantly upregulated in gastric cancer (GC) cell lines and tissues. Knockdown of ZFX induced significant apoptosis and cell cycle arrest in SGC7901 and MGC803 cells. Moreover, we demonstrated for the first time that knockdown of ZFX inhibited gastric cancer cell growth in vitro and in vivo via downregulating the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK-MAPK) pathway. Therefore, ZFX play a prominent role in GC tumorigenicity and may have potential applications in the diagnosis or treatment of GC.

Bidirectional regulation between WDR83 and its natural antisense transcript DHPS in gastric cancer

Natural antisense transcripts (NATs) exist ubiquitously in mammalian genomes and play roles in the regulation of gene expression. However, both the existence of bidirectional antisense RNA regulation and the possibility of protein-coding genes that function as antisense RNAs remain speculative. Here, we found that the protein-coding gene, deoxyhypusine synthase (DHPS), as the NAT of WDR83, concordantly regulated the expression of WDR83 mRNA and protein. Conversely, WDR83 also regulated DHPS by antisense pairing in a concordant manner. WDR83 and DHPS were capable of forming an RNA duplex at overlapping 3′ untranslated regions and this duplex increased their mutual stability, which was required for the bidirectional regulation. As a pair of protein-coding cis-sense/antisense transcripts, WDR83 and DHPS were upregulated simultaneously and correlated positively in gastric cancer (GC), driving GC pathophysiology by promoting cell proliferation. Furthermore, the positive relationship between WDR83 and DHPS was also observed in other cancers. The bidirectional regulatory relationship between WDR83 and DHPS not only enriches our understanding of antisense regulation, but also provides a more complete understanding of their functions in tumor development.

Folic Acid Prevents the Initial Occurrence of Sporadic Colorectal Adenoma in Chinese Older than 50 Years of Age: A Randomized Clinical Trial

Colorectal adenoma (CRA) is the precursor lesion of colorectal cancer (CRC). Several agents have been shown to be effective in the chemoprevention of CRA recurrence, but there has been little research on its primary prevention. Participants older than 50 years with no adenomas were recruited for our study and randomized to receive either 1 mg/day folic acid supplement or treatment without folic acid. After 3 years of follow-up, plasma folate and colonoscopy were evaluated. Seven hundred ninety-one participants (91.98%) completed the study. CRA occurred in 64 (14.88%) participants in the folic acid group and 132 (30.70%) in the control group [unadjusted risk ratio (RR), 0.49; 95% confidence interval (CI), 0.37–0.63; P < 0.01]; left-sided adenoma (unadjusted RR, 0.54; 95% CI, 0.38–0.76; P = 0.001) and advanced CRA (unadjusted RR, 0.36; 95% CI, 0.16–0.81; P = 0.01) were most common. There was no significance difference in the occurrence of three or more adenomas (unadjusted RR, 0.70; 95% CI, 0.36–1.77; P = 0.38) or right-sided adenoma (unadjusted RR, 0.55; 95% CI, 0.30–1.00; P = 0.07) between the two groups. Participants with low plasma folate may have a high risk of CRA. In conclusion, primary prevention with 1 mg/day folic acid supplementation could reduce the incidence of CRA, especially left-sided and advanced disease in those with no previous adenomas. People with differing baseline plasma folate levels should be given individualized treatment. Those with low plasma folate should be encouraged to take adequate supplements; plasma folate should be elevated to an effective therapeutic level, which may reduce the incidence of CRA. Cancer Prev Res; 6(7); 744–52. ©2013 AACR.

STAT5 isoforms regulate colorectal cancer cell apoptosis via reduction of mitochondrial membrane potential and generation of reactive oxygen species

Although the two isoforms of signal transducer and activator of transcription 5 (STAT5) protein, STAT5a and STAT5b, have 94% sequence identity, they are encoded by different genes. Previous studies have been unable to define clearly the roles of the STAT5 genes in colorectal cancer (CRC). To investigate the role of STAT5 isoforms in CRC oncogenesis, immunohistochemical staining was performed. Colorectal adenocarcinomas showed higher expression of STAT5a/5b than normal colonic mucosa (P < 0.05), and STAT5b expression was significantly higher than that of STAT5a in colorectal adenocarcinoma tissue (P < 0.05). Furthermore, STAT5b expression was significantly associated with TNM stage. To delineate the roles of STAT5a/5b in CRC carcinogenesis, we studied CRC cells depleted of each isoform by treating the cells with small interfering RNA. Both STAT5a and STAT5b were found to be involved in cell growth, cell cycle progression, and apoptosis of CRC cells, and exerted their effects via the regulation of downstream targets of the STAT genes. However, STAT5b influenced CRC cell apoptosis more than STAT5a (P < 0.05), reducing mitochondrial membrane potential and generating reactive oxygen species. In conclusion, both isoforms of STAT5 are involved in the growth and cell cycle progression of CRC cells, STAT5b could play a more important role than STAT5a in the clinicopathological characteristics of CRC and CRC cell apoptosis. J. Cell. Physiol. 227: 2421–2429, 2012.