Regulation of PTEN expression by the SWI/SNF chromatin-remodelling protein BRG1 in human colorectal carcinoma cells

Background:

Aberrant expression of Brahma-related gene-1 (BRG1), a core component of the SWI/SNF chromatin-remodelling complex, has been implicated in cancer development; however, the biological significance of BRG1 in colorectal carcinoma (CRC) remains unknown.

Methods:

In CRC tissues, expression of BRG1 and Brahma (BRM) was investigated immunohistochemically. Colorectal carcinoma-derived DLD-1 cells were used for knockdown of BRG1 and PTEN with small interfering RNA (siRNA) and transduction of Akt. Complementary DNA (cDNA) microarray analysis was performed to explore the genes affected by BRG1.

Results:

Expression of BRG1, but not BRM, was frequently elevated in CRC specimens, and knockdown of BRG1 suppressed cell proliferation of DLD-1 cells. By cDNA microarray, we determined that PTEN expression was negatively regulated by BRG1 in DLD-1 cells, which subsequently influenced the cyclin D1 levels via the phosphoinositide 3-OH kinase (PI3K)–Akt signalling pathway. The interplay of BRG1 on cyclin D1 expression was confirmed by the introduction of Akt and knockdown of PTEN in the BRG1 siRNA-transduced DLD-1 cells. Interestingly, this positive correlation between BRG1 and cyclin D1 expression was also observed in CRC specimens.

Conclusion:

Brahma-related gene-1 has an important role in the process of CRC development by activating the PI3K–Akt signalling pathway and resultant upregulation of cyclin D1 levels.     

EBV-associated gastric carcinoma in high- and low-incidence areas for nasopharyngeal carcinoma

Background:

Approximately 10% of gastric carcinomas are associated with Epstein–Barr virus (EBV). The Inuit in Greenland have a high incidence of EBV-associated nasopharyngeal carcinoma.

Methods:

We conducted a population-based case–control study comparing gastric carcinomas in Greenland and in Denmark.

Results:

The prevalence rate of EBV-associated gastric carcinomas was 8.5% in both populations.

Conclusion:

The findings of this study argue against a general susceptibility to EBV-associated carcinomas among the Inuit.     

Altered TUBB3 expression contributes to the epothilone response of mitotic cells

Background:

Epothilones are a novel group of microtubule (mt) targeting cancer drugs that bind to the β-subunit of the αβ-tubulin dimer. Epothilones inhibit cell proliferation and induce cell death by interfering with the normal mt function. In this study, we examined the consequences of altered expression of human β-tubulin isotypes in terms of the epothilone drug response in human lung and breast cancer cell lines.

Methods:

The β-tubulin isotypes TUBB2A–C, TUBB3 and TUBB were silenced or overexpressed in A549, A549EpoB40 and MCF7 cell lines in the presence or absence of epothilones. The drug effects on cell proliferation, mitosis and mt dynamics were determined using live cell microscopy and immunofluorescence assays.

Results:

Loss of TUBB3 enhanced the action of epothilones. TUBB3 knockdown increased the severity of drug-induced mitotic defects and resulted in stabilisation of the mt dynamics in cells. Moreover, exogenous expression of TUBB3 in the epothilone resistant cell line conferred the response to drug treatments. In contrast, reduced levels of TUBB2A–C or TUBB had not apparent effect on the cells'' response to epothilones.

Conclusion:

Our results show that the expression of TUBB3 contributes to the cellular response to epothilones, putatively by having an impact on the mt dynamics.     

Inactivation of the WASF3 gene in prostate cancer cells leads to suppression of tumorigenicity and metastases

Background:

The WASF3 protein is involved in cell movement and invasion, and to investigate its role in prostate cancer progression we studied the phenotypic effects of knockdown in primary tumors and cell lines.

Methods:

ShRNA was used to knockdown WASF3 function in prostate cell lines. Cell motility (scratch wound assay), anchorage independent growth and in vivo tumorigenicity and metastasis were then compared between knockdown and wild-type cells.

Results:

Increased levels of expression were seen in high-grade human prostate cancer and in the PC3 and DU145 cell lines. Inactivation of WASF3 using shRNAs reduced cell motility and invasion in these cells and reduced anchorage independent growth in vitro. The loss of motility was accompanied by an associated increase in stress fiber formation and focal adhesions. When injected subcutaneously into severe combined immunodeficiency (SCID) mice, tumor formation was significantly reduced for PC3 and DU145 cells with WASF3 knockdown and in vivo metastasis assays using tail vain injection showed a significant reduction for PC3 and DU145 cells. The loss of the invasion phenotype was accompanied by down-regulation of matrix metalloproteinase 9.

Conclusions:

Overall, these observations demonstrate a critical role for WASF3 in the progression of prostate cancer and identify a potential target to control tumorigenicity and metastasis.     

MicroRNA-15b is induced with E2F-controlled genes in HPV-related cancer

Background:

MicroRNAs (miRNAs) are important regulators of cellular processes and are found to be deregulated in many cancers. We here analysed the miRNA expression in anal carcinomas. In a previous study, we found that our anal carcinoma tumours were divided into two groups based on the expression of E2F-regulated genes. Therefore, we searched for miRNAs that could reproduce this grouping.

Methods:

A global screen of the miRNA population was performed using real-time quantitative PCR (RT–qPCR) array methods and differentially expressed miRNAs were identified. Real-time–qPCR was used to verify the expression levels of selected miRNAs and genes in a larger collection of biopsies. A siRNA-mediated knockdown of human papilloma virus (HPV)16 E7 in a cervical cell line was performed to assess the effect of E7 on miR-15b.

Results:

The grouping of tumours into two groups based on the expression of E2F-controlled genes was confirmed in a larger collection of anal carcinoma tumours. The expression of miR-15b was shown to be highly correlated with that of five selected E2F-induced genes (CCNA2, CCNB1, CCNB2, MSH6 and MCM7). A knockdown of HPV16 E7 resulted in decreased levels of miR-15b in Ca Ski cells.

Conclusion:

MiR-15b expression correlates with E2F-regulated genes in anal carcinoma and appears to be part of the E2F-regulatory network.     

High expression of N-acetylglucosaminyltransferase IVa promotes invasion of choriocarcinoma

Background:

Gestational trophoblastic diseases (GTDs) are related to trophoblasts, and human chorionic gonadotropin (hCG) is secreted by GTDs as well as normal placentas. However, the asparagine-linked sugar chains on hCG contain abnormal biantennary structures in invasive mole and choriocarcinoma, but not normal pregnancy or hydatidiform mole. N-acetylglucosaminyltransferase-IV (GnT-IV) catalyses β1,4-N-acetylglucosamine branching on asparagine-linked oligosaccharides, which are consistent with the abnormal sugar chain structures on hCG.

Methods:

We investigated GnT-IVa expression in GTDs and placentas by immunohistochemistry, western blot, and RT–PCR. We assessed the effects of GnT-IVa knockdown in choriocarcinoma cells in vitro and in vivo.

Results:

The GnT-IVa was highly expressed in trophoblasts of invasive mole and choriocarcinoma, and moderately in extravillous trophoblasts during the first trimester, but not in hydatidiform mole or other normal trophoblasts. The GnT-IVa knockdown in choriocarcinoma cells significantly reduced migration and invasive capacities, and suppressed cellular adhesion to extracellular matrix proteins. The extent of β1,4-N-acetylglucosamine branching on β1 integrin was greatly reduced by GnT-IVa knockdown, although the expression of β1 integrin was not changed. In vivo studies further demonstrated that GnT-IVa knockdown suppressed tumour engraftment and growth.

Conclusion:

These findings suggest that GnT-IVa is involved in regulating invasion of choriocarcinoma through modifications of the oligosaccharide chains of β1 integrin.     

Breast cancer and ductal carcinoma in situ among women with prior squamous or glandular precancer in the cervix: a register-based study

Background:

Human papillomavirus and hormonal contraceptives may be risk factors for cervical precancer and malignant breast tumours.

Methods:

Standardised incidence ratios (SIRs) of malignant breast tumours during 1970–2008 were estimated separately for women with prior squamous and glandular cervical precancer.

Results:

Women with squamous precancer and women with glandular precancer in the cervix had a significantly higher risk of malignant breast tumours than the general female population (SIR, 95% confidence interval: 1.10, 1.05–1.14 and 1.52, 1.11–2.08, respectively).

Interpretation:

Shared risk factors or screening attendance may explain the excess risk of malignant breast tumours among women with a history of cervical precancer.     

Stage-dependent alterations of the serum cytokine pattern in colorectal carcinoma

Background:

Inflammation contributes to the pathogenesis of colorectal cancer (CRC), and cytokine levels are altered during colorectal carcinogenesis.

Methods:

The serum levels of 13 cytokines and their relation to clinical and pathological parameters, and systemic inflammatory response (mGPS, CRP and neutrophil–lymphocyte ratio), were analysed from a prospective series of 148 CRC patients and 86 healthy age- and sex-matched controls.

Results:

CRC patients had higher serum platelet-derived growth factor, interleukin (IL)-6, IL-7, and IL-8 levels and lower monocyte chemotactic protein-1 (MCP-1) levels than the controls. A logistic regression model for discriminating the patients from the controls – including the five most predictive cytokines (high IL-8, high IL-6, low MCP-1, low IL-1ra, and low IP-10) – yielded an area under curve value of 0.890 in receiver operating characteristics analysis. Serum cytokines showed distinct correlation with other markers of systemic inflammatory response, and advanced CRCs were associated with higher levels of IL-8, IL-1ra, and IL-6. A metastasised disease was accompanied by an orientation towards Th2 cytokine milieu.

Conclusion:

CRC is associated with extensive alterations in serum cytokine environment, highlighting the importance of studying relative cytokine level alterations. Serum cytokine profile shows promise in separating CRC patients from healthy controls but its clinical value is yet to be confirmed.     

Basic fibroblast growth factor in the bone microenvironment enhances cell motility and invasion of Ewing's sarcoma family of tumours by activating the FGFR1�CPI3K�CRac1 pathway

Background:

Ewing''s sarcoma family of tumours (ESFT) is a malignant small round-cell tumour of the bone and soft tissues. It is characterised by a strong tendency to invade and form metastases. The microenvironment of the bone marrow is a large repository for many growth factors, including the basic fibroblast growth factor (bFGF). However, the role of bFGF in the invasive and metastatic phenotype of ESFT has not been investigated.

Methods:

The motility and invasion of ESFT cells were assessed by a wound-healing assay, chemotaxis assay, and invasion assay. The expression and activation of FGF receptors (FGFRs) in ESFT cell lines and clinical samples were detected by RT–PCR, western blotting, and immunohistochemistry. The morphology of ESFT cells was investigated by phase-contrast microscopy and fluorescence staining for actin. Activation of Rac1 was analysed by a pull-down assay.

Results:

bFGF strongly induced the motility and invasion of ESFT cells. Furthermore, FGFR1 was found to be expressed and activated in clinical samples of ESFT. Basic FGF-induced cell motility was mediated through the FGFR1–phosphatidylinositol 3-kinase (PI3K)–Rac1 pathway. Conditioned medium from bone marrow stromal cells induced the motility of ESFT cells by activating bFGF/FGFR1 signalling.

Conclusion:

The bFGF–FGFR1–PI3K–Rac1 pathway in the bone microenvironment may have a significant role in the invasion and metastasis of ESFT.     

Endoplasmic reticulum ribosome-binding protein 1, RRBP1, promotes progression of colorectal cancer and predicts an unfavourable prognosis

Background:

Ribosome-binding protein 1 (RRBP1) has been implicated in the regulation of unfolded protein response, which is involved in almost every aspect of cancer development. We aimed to explore the significance of RRBP1 in the progression and prognosis of colorectal cancer (CRC).

Methods:

The study population consisted of 856 patients with stage I–III CRC from two hospitals. RRBP1 expression was examined by immunohistochemisty (IHC) in colorectal tissues. The correlation of RRBP1 expression and CRC occurrence was assessed in paired cancer-adjacent tissues. Factors contributing to prognosis were evaluated in a training-validation design with univariate and multivariate Cox analysis. Colorectal cancer aggressiveness caused by RRBP1 knockdown or overexpression was evaluated in CRC cells.

Results:

RRBP1 was aberrantly overexpressed in CRC. Compared with low-RRBP1 patients, high-RRBP1 patients had shorter disease-specific survival in the training (hazard ratio (HR), 2.423; 95% confidence interval (CI), 1.531–3.835) and validation cohorts (HR, 3.749; 95% CI, 2.166–6.448) in multivariate Cox analysis. High-RRBP1 independently predicted a shorter disease-free survival (HR, 4.821; 95% CI, 3.220–7.218) in the validation cohort. RRBP1 knockdown reduced the aggressiveness of CRC cells in vitro and inhibited the growth of CRC xenografts in vivo.

Conclusions:

High RRBP1 expression facilitates CRC progression and predicts an unfavourable post-operative prognosis.     

Targeting SRPK1 to control VEGF-mediated tumour angiogenesis in metastatic melanoma

Background:

Current therapies for metastatic melanoma are targeted either at cancer mutations driving growth (e.g., vemurafenib) or immune-based therapies (e.g., ipilimumab). Tumour progression also requires angiogenesis, which is regulated by VEGF-A, itself alternatively spliced to form two families of isoforms, pro- and anti-angiogenic. Metastatic melanoma is associated with a splicing switch to pro-angiogenic VEGF-A, previously shown to be regulated by SRSF1 phosphorylation by SRPK1. Here, we show a novel approach to preventing angiogenesis—targeting splicing factor kinases that are highly expressed in melanomas.

Methods:

We used RT–PCR, western blotting and immunohistochemistry to investigate SRPK1, SRSF1 and VEGF expression in tumour cells, and in vivo xenograft assays to investigate SRPK1 knockdown and inhibition in vivo.

Results:

In both uveal and cutaneous melanoma cell lines, SRPK1 was highly expressed, and inhibition of SRPK1 by knockdown or with pharmacological inhibitors reduced pro-angiogenic VEGF expression maintaining the production of anti-angiogenic VEGF isoforms. Both pharmacological SRPK1 inhibitors and SRPK1 knockdown reduced growth of human melanomas in vivo, but neither affected cell proliferation in vitro.

Conclusions:

These results suggest that selective blocking of pro-angiogenic isoforms by inhibiting splice-site selection with SRPK1 inhibitors reduces melanoma growth. SRPK1 inhibitors may be used as therapeutic agents.     

Abnormal expression of TRIB3 in colorectal cancer: a novel marker for prognosis

Background:

TRIB3 is a human homologue of Drosophila tribbles. Previous studies have shown that TRIB3 controls the cell growth through ubiquitination-dependent degradation of other proteins, whereas its significance in the prognosis of colorectal cancer (CRC) is not yet fully understood.

Materials:

This study comprised 202 patients who underwent surgery for CRC, as well as 22 cell lines derived from human gastrointestinal cancer. The correlation of gene expression with clinical parameters in patients was assessed. The biological significance was evaluated by knockdown experiments in seven colorectal cancer cell lines.

Results:

A total of 20 cancer cell lines (90.9%) expressed the TRIB3 gene. The assessment in surgical specimens indicated that the gene expression was significantly higher in the cancerous region than in the marginal non-cancerous region. Patients with high TRIB3 expression were statistically susceptible to a recurrence of the disease, and showed poorer overall survival than those with low expression. The assessment of TRIB3 knockdown in five cell lines showed that small interfering RNA (siRNA) inhibition resulted in a statistically significant reduction in cell growth.

Conclusion:

These data strongly suggest the usefulness of TRIB3 as a marker for predicting the prognosis of CRC patients, showing a basis for the development of effective treatments for CRC.     

MicroRNA-126 and epidermal growth factor-like domain 7–an angiogenic couple of importance in metastatic colorectal cancer. Results from the Nordic ACT trial

Background:

This study investigated the clinical importance of linked angiogenetic biomarkers to chemotherapy, combined with the anti-vascular endothelial growth factor A (anti-VEGF-A), as a first-line treatment in patients with metastatic colorectal cancer (mCRC).

Methods:

A total of 230 patients from a randomised phase III study were included. The primary microRNA-126 (pri-miRNA-126) A24G single-nucleotide polymorphism and the mature miRNA-126 were analysed by PCR using genomic DNA (full blood) and formalin-fixed paraffin-embedded tissue sections, respectively. The epidermal growth factor-like domain 7 (EGFL7) protein was visualised and quantified using immunohistochemistry.

Results:

High tumour expression of miRNA-126 was significantly related to a longer progression-free survival. The independent prognostic value of miRNA-126 was confirmed using a Cox regression analysis (hazard ratio=0.49, 95% confidence interval=0.29–0.84, P=0.009). Although not significant, a relationship between EGFL7 expression and response rates is suggested, with EGFL7 expression at the invasive front being lower in responding patients than in the non-responders (P=0.063).

Conclusion:

The results validate the previous findings on the prognostic value of miRNA-126 in mCRC and may suggest a relationship between treatment efficacy and EGFL7 expression. As miRNA-126 may target VEGF-A as well as EGFL7, the results may provide predictive information in relation to next-generation anti-angiogenetics.     

Epstein-Barr virus microRNAs and lung cancer

Background:

We conducted the first analysis of viral microRNAs (miRNAs) in lung cancer, with a focus on Epstein–Barr virus (EBV).

Methods:

We evaluated viral miRs with a two-channel oligo-array targeting mature, anti-sense miRNAs in 290 cases. In 48 cases, we compared microarray and real-time quantitative PCR (qPCR) expression for three EBV miRNAs. We tested for EBV DNA, RNA, and protein in tumour tissue from six cases with and six cases without strong qPCR-based evidence of EBV miRNAs.

Results:

The EBV miRNAs strongly differentiated between adenocarcinoma and squamous cell carcinoma using the microarray (P<0.01 for 9 out of 16 EBV miRNAs). However, microarray and qPCR measurements of BART1, BART2, and BHRF1–3 expression were not significantly correlated (P=0.53, 0.94, and 0.47, respectively). Although qPCR provided substantial evidence of EBV miRNAs in 7 out of 48 cases, only 1 of these 7 cases had detectable EBV DNA in tumour tissue. None had detectable EBV RNA or protein by histochemical stains.

Conclusion:

In a comprehensive evaluation of EBV miRNA, DNA, RNA, and protein in lung cancer, we found little evidence of EBV in lung tumour tissue. Discrepancies between microarray- and qPCR-based strategies highlight the difficulty of validating molecular markers of disease. Our results do not support a role of EBV in lung cancer.     

An antitumorigenic role for the IL-33 receptor,ST2L,in colon cancer

Background:

Despite the importance of inflammation in cancer, the role of the cytokine IL-33, and its receptor ST2, in colon cancer is unclear. The aim of this study was to investigate the role of IL-33, and its receptor isoforms (ST2 and ST2L), in colon cancer.

Methods:

Serum levels of IL-33 and sST2 were determined with ELISA. ST2 and IL-33 expression was detected with quantitative real-time PCR (qRT–PCR), western blotting and immunohistochemistry. ST2 expression in CT26 cells was stably suppressed using ST2-specific shRNA. Cytokine and chemokine gene expression was detected with qRT–PCR.

Results:

Human colon tumours showed lower expression of ST2L as compared with adjacent non-tumour tissue (P<0.01). Moreover, the higher the tumour grade, the lower the expression of ST2L (P=0.026). Colon cancer cells expressed ST2 and IL-33 in vitro. Functional analyses showed that stimulation of tumour cells with IL-33 induced the expression of chemokine (C–C motif) ligand 2 (CCL2). Knockdown of ST2 in murine colon cancer cells resulted in enhanced tumour growth (P<0.05) in BALB/c mice in vivo. This was associated with a decrease in macrophage infiltration, with IL-33-induced macrophage recruitment reduced by antagonising CCL2 in vitro.

Conclusion:

The IL-33/ST2 signalling axis may have a protective role in colon carcinogenesis.     

In situ quantification of HER2–protein tyrosine kinase 6 (PTK6) protein–protein complexes in paraffin sections from breast cancer tissues

Background:

Protein tyrosine kinase 6 (PTK6; breast tumour kinase) is overexpressed in up to 86% of the invasive breast cancers, and its association with the oncoprotein human epidermal growth factor receptor 2 (HER2) was shown in vitro by co-precipitation. Furthermore, expression of PTK6 in tumours is linked with the expression of HER2.

Method and results:

In this study, we used the proximity ligation assay (PLA) technique on formalin-fixed paraffin sections from eighty invasive breast carcinoma tissue specimens to locate PTK6–HER2 protein–protein complexes. Proximity ligation assay signals from protein complexes were assessed quantitatively, and expression levels showed a statistically significant association with tumour size (P=0.015) and course of the cancer disease (P=0.012).

Conclusion:

Protein tyrosine kinase 6 forms protein complexes with HER2 in primary breast cancer tissues, which can be visualised by use of the PLA technique. Human epidermal growth factor receptor 2–PTK6 complexes are of prognostic relevance.     

CD44s signals the acquisition of the mesenchymal phenotype required for anchorage-independent cell survival in hepatocellular carcinoma

Background:

Circulating tumour cells (CTCs) have an important role in metastatic processes, but details of their basic characteristics remain elusive. We hypothesised that CD44-expressing CTCs show a mesenchymal phenotype and high potential for survival in hepatocellular carcinoma (HCC).

Methods:

Circulating CD44⁺CD90⁺ cells, previously shown to be tumour-initiating cells, were sorted from human blood and their genetic characteristics were compared with those of tumour cells from primary tissues. The mechanism underlying the high survival potential of CD44-expressing cells in the circulatory system was investigated in vitro.

Results:

CD44⁺CD90⁺ cells in the blood acquired epithelial–mesenchymal transition, and CD44 expression remarkably increased from the tissue to the blood. In Li7 and HLE cells, the CD44^high population showed higher anoikis resistance and sphere-forming ability than did the CD44^low population. This difference was found to be attributed to the upregulation of Twist1 and Akt signal in the CD44^high population. Twist1 knockdown showed remarkable reduction in anoikis resistance, sphere formation, and Akt signal in HLE cells. In addition, mesenchymal markers and CD44s expression were downregulated in the Twist1 knockdown.

Conclusions:

CD44s symbolises the acquisition of a mesenchymal phenotype regulating anchorage-independent capacity. CD44s-expressing tumour cells in peripheral blood are clinically important therapeutic targets in HCC.     

Downregulation of cell surface CA125/MUC16 induces epithelial-to-mesenchymal transition and restores EGFR signalling in NIH:OVCAR3 ovarian carcinoma cells

Background:

Epithelial ovarian cancer (EOC) cells are prone to metastasise throughout the peritoneal cavity. The epithelial-to-mesenchymal transition (EMT) is a necessary step towards metastatic tumour progression. CA125/MUC16 mucin is a high-molecular-weight glycoprotein overexpressed in the majority of serous carcinomas, suggesting a possible role in the pathogenesis of these cancers.

Methods:

The role of CA125/MUC16 in EMT was investigated using single-chain antibody-mediated knockdown of cell surface CA125/MUC16 in overexpressing EOC NIH:OVCAR3 cells.

Results:

CA125/MUC16 knockdown was associated with morphological alterations along with decreased surface expression of epithelial markers (E-cadherin, cytokeratin-18) and increased expression of mesenchymal markers (N-cadherin, vimentin). Co-immunoprecipitation experiments revealed that CA125/MUC16 binds to E-cadherin and β-catenin complexes. The in vitro studies showed disruption of cell–cell junctions, enhanced motility, migration and invasiveness in CA125/MUC16 knockdown cells. Enhanced epidermal growth factor receptor (EGFR) activation was observed in CA125/MUC16 knockdown cells along with increased Akt and ERK1/2 phosphorylation, which are downstream effectors of EGFR, and increased MMP-2 and MMP-9 expression and activities. Epidermal growth factor receptor inhibition strongly inhibited the motility of CA125/MUC16 knockdown cells.

Conclusions:

Our findings suggest that CA125/MUC16 plays a role in EMT, presumably through its interaction with E-cadherin and β-catenin complexes and by modulating EGFR and its downstream signalling pathway in NIH:OVCAR3 cells.