Zhang Wh

β-Catenin/TCF pathway upregulates STAT3 expression in human esophageal squamous cell carcinoma

Precise roles of beta-catenin/TCF pathway involved in esophageal tumorigenesis remain elusive. Here we found STAT3 overexpression in esophageal cancer cells and tissues, and its overexpression in esophageal squamous cell carcinoma (ESCC) tissues correlated with beta-catenin cytoplasmic/nuclear accumulation. A functional TCF binding element was detected in STAT3 promoter which specifically bound to TCF4. Transfected beta-catenin induced STAT3 transcriptional activity dose-dependently, and also enhanced STAT3 mRNA and protein levels. These inductions were specifically abolished by dominant-negative TCF4. These results suggest that STAT3 is a target of beta-catenin/TCF pathway and might participate in esophageal tumorigenesis.

TNF-α is a novel target of miR-19a.

Many studies have demonstrated the overexpression and amplification of the miR-17-92 cluster in malignant human cancers, including B-cell lymphomas and lung cancers. The purpose of this study was to investigate for the first time, the expression of the miR-17-92 cluster in esophageal squamous cell carcinoma (ESCC). The miR-17-92 cluster was found to be overexpressed in 21 out of 28 (75%) esophageal cancer samples. It was also found that overexpression of the miR-17-92 cluster could promote cellular growth in vivo and in vitro. Furthermore, inhibition of miR-19a by antisense oligonucleotides (ONs) induced apoptosis, while antisense ONs against miR-17-5p, miR-18a, miR-20a and miR-92-1 did not exhibit such an effect. In addition, it was found that antagomir-19a treatment could impair tumor growth in vivo. Using Human Apoptosis RT2 Profiler PCR Array 384HT, we found that tumor necrosis factor-α (TNF-α) was up-regulated 12-fold in cells transfected with miR-19a antisense ONs compared to the cells treated with the control scramble ONs. MiR-19a was predicted to target the 3 untranslated region of TNF-α mRNA, and this was confirmed by luciferase reporter assay. Taken together, we conclude that the miR-17-92 cluster is overexpressed in ESCC and that TNF-α is a novel target of miR-19a.

miR‐106a is frequently upregulated in gastric cancer and inhibits the extrinsic apoptotic pathway by targeting FAS

Emerging evidence has shown the association of aberrantly expressed miR‐106a with cancer development, however, little is known about its potential role in gastric carcinogenesis. In our present study, obviously overexpressed miR‐106a was found in gastric cancer tissues compared with their nontumor counterparts. Suppression of miR‐106a significantly inhibited gastric cancer cell proliferation and triggered apoptosis. Bioinformatic analysis combining with validation experiments identified FAS as a direct target of miR‐106a. Rescue experiments and examination of caspase‐8, PARP and caspase‐3 further approved that miR‐106a could inhibit gastric cancer cell apoptosis through interfering with FAS‐mediated apoptotic pathway. Moreover, a significant inverse correlation was found between miR‐106a and FAS expression not only in gastric cancer cell lines but also in gastric cancer specimens. Taken together, these findings suggest that ectopicly overexpressed miR‐106a may play an oncogenic role in gastric carcinogenesis and impair extrinsic apoptotic pathway through targeting FAS.

Identification of genes regulated by Wnt/β-catenin pathway and involved in apoptosis via microarray analysis

BackgroundWnt/β-catenin pathway has critical roles in development and oncogenesis. Although significant progress has been made in understanding the downstream signaling cascade of this pathway, little is known regarding Wnt/β-catenin pathway modification of the cellular apoptosis.MethodsTo identify potential genes regulated by Wnt/β-catenin pathway and involved in apoptosis, we used a stably integrated, inducible RNA interference (RNAi) vector to specific inhibit the expression and the transcriptional activity of β-catenin in HeLa cells. Meanwhile, we designed an oligonucleotide microarray covering 1384 apoptosis-related genes. Using oligonucleotide microarrays, a series of differential expression of genes was identified and further confirmed by RT-PCR.ResultsStably integrated inducible RNAi vector could effectively suppress β-catenin expression and the transcriptional activity of β-catenin/TCF. Meanwhile, depletion of β-catenin in this manner made the cells more sensitive to apoptosis. 130 genes involved in some important cell-apoptotic pathways, such as PTEN-PI3K-AKT pathway, NF-κB pathway and p53 pathway, showed significant alteration in their expression level after the knockdown of β-catenin.ConclusionCoupling RNAi knockdown with microarray and RT-PCR analyses proves to be a versatile strategy for identifying genes regulated by Wnt/β-catenin pathway and for a better understanding the role of this pathway in apoptosis. Some of the identified β-catenin/TCF directed or indirected target genes may represent excellent targets to limit tumor growth.

Macrophage inhibitory cytokine 1 (MIC-1/GDF15) as a novel diagnostic serum biomarker in pancreatic ductal adenocarcinoma.

BackgroundMacrophage inhibitory cytokine 1 (MIC-1/GDF15) has been identified as a potential novel biomarker for detection of pancreatic cancer (PCa). However, the diagnostic value of serum MIC-1 for pancreatic ductal adenocarcinoma (PDAC), particularly for those at the early stage, and the value for treatment response monitoring have not yet been investigated.MethodsMIC-1 expression in tumor tissue was analyzed by RT-PCR from 64 patients with PDAC. Serum MIC-1 levels were detected by ELISA in 1472 participants including PDAC, benign pancreas tumor, chronic pancreatitis and normal controls. The diagnostic performance of MIC-1 was assessed and compared with CA19.9, CEA and CA242, and the value of it as a predictive indicator for therapeutic response and tumor recurrence was also evaluated.ResultsMIC-1 levels were significantly elevated in PDAC tissues as well as serum samples. The sensitivity of serum MIC-1 for PDAC diagnosis was much higher than that of CA19.9 (65.8% vs. 53.3%) with similar specificities. Furthermore, serum MIC-1 detected 238 out of 377 (63.1%) CA19.9-negative PDAC. Moreover, receiver operating characteristic (ROC) curve analysis also showed that serum MIC-1 had a better performance compared with CA19.9 in distinguishing early-stage PDAC from normal serum with a higher sensitivity (62.5% vs. 25.0% respectively). Notably, serum MIC-1 level was significantly decreased in patients with PDAC after curative resection and returned to elevated levels when tumor relapse occurred.ConclusionsSerum MIC-1 is significantly elevated in most PDAC, including those with negative CA19.9 and early stage disease, and thus may serve as a novel diagnostic marker in early diagnosis and postoperative monitoring of PDAC.

EB1 acts as an oncogene via activating β-catenin/TCF pathway to promote cellular growth and inhibit apoptosis†

Previously we showed that end‐binding protein 1 (EB1) may promote cellular growth by activating β‐catenin/T‐cell factor (TCF) pathway. To further investigate the role of EB1 in regulating cellular growth, we established an EB1‐inducible expression system in which the protein level of EB1 was significantly upregulated upon doxycycline induction. We found that EB1 promoted cellular growth and resulted in a significant increase in colony formation. In addition, EB1 could induce tumor formation in nude mice, activate β‐catenin‐dependent gene expression and upregulate the transcriptional activity of c‐myc. We also showed that EB1 in this manner inhibited apoptosis of 293‐T‐REx cells upon cisplatin and upregulated expression of Bcl‐2, whereas ΔN TCF4, an inhibitor of β‐catenin/TCF pathway, could completely or partially abolish the effects of EB1 on the promotion of cell growth and the inhibition of apoptosis activity. Moreover, knockdown of c‐myc by RNAi could abrogate upregulation of EB1‐dependent induction of Bcl‐2 expression. Overall, EB1 acts as a potential oncogene via activating β‐catenin/TCF pathway to promote cellular growth and inhibit apoptosis.

Use of an expanded gold standard to estimate the accuracy of colposcopy and visual inspection with acetic acid

We estimate the accuracy of colposcopy and visual inspection with acetic acid (VIA) while minimizing the effects of misclassification bias, and maximizing ascertainment of disease. VIA was performed by experienced physicians on a population‐based sample of women aged 30 to 49 years in rural Shanxi province, China. Each woman received VIA, liquid‐based cytology (LBC) and hybrid capture 2 (hc2, QIAGEN, Gaithersburg, MD; formerly Digene Corporation). Any woman who tested positive on any test had colposcopy, endocervical curettage (ECC) with directed biopsies as necessary and 4‐quadrant random biopsies from normal‐appearing areas of the cervix. A standard diagnosis based on colposcopy and directed biopsy, and an expanded diagnosis including ECC and 4‐quadrant random biopsy were generated for each woman. In 1,839 women, use of the expanded versus the standard diagnostic criteria increased the prevalence of histologically confirmed high‐grade cervical intraepithelial neoplasia and cancer (CIN2+) from 3.2% (59/1,839) to 4.2% (77/1,839) and decreased the sensitivity of VIA for CIN2+ from 69.5% (95% CI: 56.8–79.8) to 58.4% (95% CI: 47.3–68.8%) with little change in specificity of approximately 89%. Compared with the expanded diagnostic criterion, the sensitivity of a visual diagnosis of high‐grade CIN or cancer by a colposcopist was 49.4% (95% CI: 38.2–60.5). The use of an expanded diagnostic criterion in this study yielded more conservative estimates of the sensitivity of VIA and colposcopy.

Inhibition of ErbB2 by Herceptin reduces survivin expression via the ErbB2–β-catenin/TCF4-survivin pathway in ErbB2-overexpressed breast cancer cells

Overexpression of ErbB2 is associated with poor prognosis in breast cancer. Targeting of ErbB2 is a very common therapeutic strategy in ErbB2‐overexpressed breast cancer. Herceptin is the first approved and most widely used agent for ErbB2‐targeting therapy in breast cancer. Even though the clinical application has been performed for more than 10u2003years, the exact mechanism underlying how Herceptin exhibits its effects has not been fully elucidated. In this study, we found that Herceptin could inhibit the expression of survivin in ErbB2‐overexpressed cell lines. Overexpression of survivin could abrogate the inhibition of cell growth induced by Herceptin. Herceptin could reduce survivin expression at the transcriptional level. The β‐catenin/T‐cell factor (TCF) pathway played a very crucial role in this cascade. We found that Herceptin could reduce tyrosine phosphorylation levels of ErbB2 and β‐catenin. Herceptin treatment induced degradation of β‐catenin protein, resulting in reduced binding affinity of β‐catenin/TCF4 to the promoter region of survivin. When we cross‐mutated the TCF4 binding sites in the promoter region of survivin, the reduction of survivin promoter activity almost diminished. Taken together, we showed that Herceptin could inhibit survivin expression through the ErbB2–β‐catenin/TCF4‐survivin pathway in ErbB2‐overexpressed breast cancer cells. This indicates that there may be a new cascade axis from ErbB2 to survivin.

FRAT1 overexpression leads to aberrant activation of β-catenin/TCF pathway in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is an aggressive tumor with a poor prognosis. Although aberrant activation of β‐catenin/T‐cell factor (TCF) pathway has been observed in ESCC, mechanisms underlying this phenomenon remain unknown. Frequently rearranged in advanced T‐cell lymphomas‐1 (FRAT1), overexpressed in some ESCC lines, is a positive regulator of β‐catenin/TCF pathway. However, little is known about the molecular relationship between FRAT1 and β‐catenin/TCF in ESCC. In this study, we analyzed freshly resected ESCC specimens and demonstrated that FRAT1 was overexpressed in approximately 74% of tumor samples compared with matched normal tissue. Overexpression of FRAT1 significantly promoted esophageal cancer cells growth, whereas suppression of FRAT1 level by RNAi markedly inhibited their growth. In addition, FRAT1 overexpression induced the nuclear accumulation of β‐catenin and promoted the transcriptional activity of β‐catenin/TCF. These effects were reversed by coexpression of GSK 3β or ΔN TCF4. Furthermore, accumulation of β‐catenin was correlated with FRAT1 overexpression in ESCC and the basal layer of normal esophageal epithelium. Finally, continued expression of c‐Myc is necessary and sufficient for maintenance of the growth state in cells expressing FRAT1. Taken together, these results support the novel hypothesis that aberrant activation of β‐catenin/TCF pathway in esophageal cancer appears to be due to upstream events such as FRAT1 overexpression, and c‐Myc may be an important element in oncogenesis of human ESCC induced by FRAT1.

Suppression of Aurora-A oncogenic potential by c-Myc downregulation.

The abnormality of serine/threonine kinase Aurora-A is seen in many types of cancers. Although in physiological context it has been shown to play a vital role in cellular mitosis, how this oncogene contributes to tumorigenesis remains unclear. Here we demonstrate that Aurora-A overexpression enhances both the expression level and transcriptional activity of c-Myc. The inhibition of c-Myc expression by RNA interference significantly impaired the oncogenic potential of Aurora-A, resulting in attenuated cellular proliferation and transformation rates as well as fewer centrosomal aberrations. Furthermore, downregulation of c-Myc effectively overcame Aurora-A-induced resistance to cisplatin in esophageal cancer cells. Taken together, our results suggest an important role for c-Myc in mediating the oncogenic activity of Aurora-A, which may in turn allow for future targeting of c-Myc as a potential therapeutic strategy for tumors with Aurora-A overexpression.