Analysis of specific transcriptional regulators as early predictors of independent prognostic relevance in resected colorectal cancer

SP4 Facilitates Esophageal Squamous Cell Carcinoma Progression by Activating PHF14 Transcription and Wnt/Β-Catenin Signaling

Specificity protein 4 transcription factor (SP4), a member of the Sp/Krüppel-like family (KLF), could bind to GT and GC box promoters, and plays an essential role in transcriptional activating. Despite SP4 having been detected to be highly expressed in a variety of human tumors, its biological effect and underlying molecular mechanism in esophageal squamous cell carcinoma (ESCC) remains unclear. Our research discovered that high SP4 expression is detected in primary ESCC specimens and cell lines and is strongly associated with the ESCC tumor grade and poor prognosis. In vitro, knockdown of SP4 suppressed cell proliferation and cell-cycle progression and promoted apoptosis, whereas overexpression of SP4 did the opposite. In vivo, inhibiting SP4 expression in ESCC cells suppresses tumor growth. Subsequently, we demonstrated that SP4 acts as the transcriptional upstream of PHF14, which binds to PHF14 promoter region, thus promoting PHF14 transcription. PHF14 was also significantly expressed in patient tissues and various ESCC cell lines and its expression promoted cell proliferation and inhibited apoptosis. Moreover, knockdown of SP4 inhibited the Wnt/β-catenin signaling pathway, whereas overexpression of PHF14 eliminated the effects of SP4 knockdown in ESCC cells. These results demonstrate that SP4 activates the Wnt/β-catenin signaling pathway by driving PHF14 transcription, thereby promoting ESCC progression, which indicates that SP4 might act as a prospective prognostic indicator or therapeutic target for patients with ESCC.

IMPLICATIONS

This study identified SP4/PH14 axis as a new mechanism to promote the progression of ESCC, which may serve as a novel therapeutic target for patients with ESCC.

Specificity Proteins (Sp) and Cancer

The specificity protein (Sp) transcription factors (TFs) Sp1, Sp2, Sp3 and Sp4 exhibit structural and functional similarities in cancer cells and extensive studies of Sp1 show that it is a negative prognostic factor for patients with multiple tumor types. In this review, the role of Sp1, Sp3 and Sp4 in the development of cancer and their regulation of pro-oncogenic factors and pathways is reviewed. In addition, interactions with non-coding RNAs and the development of agents that target Sp transcription factors are also discussed. Studies on normal cell transformation into cancer cell lines show that this transformation process is accompanied by increased levels of Sp1 in most cell models, and in the transformation of muscle cells into rhabdomyosarcoma, both Sp1 and Sp3, but not Sp4, are increased. The pro-oncogenic functions of Sp1, Sp3 and Sp4 in cancer cell lines were studied in knockdown studies where silencing of each individual Sp TF decreased cancer growth, invasion and induced apoptosis. Silencing of an individual Sp TF was not compensated for by the other two and it was concluded that Sp1, Sp3 and Sp4 are examples of non-oncogene addicted genes. This conclusion was strengthened by the results of Sp TF interactions with non-coding microRNAs and long non-coding RNAs where Sp1 contributed to pro-oncogenic functions of Sp/non-coding RNAs. There are now many examples of anticancer agents and pharmaceuticals that induce downregulation/degradation of Sp1, Sp3 and Sp4, yet clinical applications of drugs specifically targeting Sp TFs are not being used. The application of agents targeting Sp TFs in combination therapies should be considered for their potential to enhance treatment efficacy and decrease toxic side effects.

Flavonoids kaempferol and quercetin are nuclear receptor 4A1 (NR4A1, Nur77) ligands and inhibit rhabdomyosarcoma cell and tumor growth

BACKGROUND

Flavonoids exhibit both chemopreventive and chemotherapeutic activity for multiple tumor types, however, their mechanisms of action are not well defined. Based on some of their functional and gene modifying activities as anticancer agents, we hypothesized that kaempferol and quercetin were nuclear receptor 4A1 (NR4A1, Nur77) ligands and confirmed that both compounds directly bound NR4A1 with KD values of 3.1 and 0.93 μM, respectively.

METHODS

The activities of kaempferol and quercetin were determined in direct binding to NR4A1 protein and in NR4A1-dependent transactivation assays in Rh30 and Rh41 rhabdomyosarcoma (RMS) cells. Flavonoid-dependent effects as inhibitors of cell growth, survival and invasion were determined in XTT and Boyden chamber assays respectively and changes in protein levels were determined by western blots. Tumor growth inhibition studies were carried out in athymic nude mice bearing Rh30 cells as xenografts.

RESULTS

Kaempferol and quercetin bind NR4A1 protein and inhibit NR4A1-dependent transactivation in RMS cells. NR4A1 also regulates RMS cell growth, survival, mTOR signaling and invasion. The pro-oncogenic PAX3-FOXO1 and G9a genes are also regulated by NR4A1 and, these pathways and genes are all inhibited by kaempferol and quercetin. Moreover, at a dose of 50 mg/kg/d kaempferol and quercetin inhibited tumor growth in an athymic nude mouse xenograft model bearing Rh30 cells.

CONCLUSION

These results demonstrate the clinical potential for repurposing kaempferol and quercetin for clinical applications as precision medicine for treating RMS patients that express NR4A1 in order to increase the efficacy and decrease dosages of currently used cytotoxic drugs.

Transcription factors specificity protein and nuclear receptor 4A1 in pancreatic cancer

Specificity protein (Sp) transcription factors (TFs) Sp1, Sp3 and Sp4, and the orphan nuclear receptor 4A1 (NR4A1) are highly expressed in pancreatic tumors and Sp1 is a negative prognostic factor for pancreatic cancer patient survival. Results of knockdown and overexpression of Sp1, Sp3 and Sp4 in pancreatic and other cancer lines show that these TFs are individually pro-oncogenic factors and loss of one Sp TF is not compensated by other members. NR4A1 is also a pro-oncogenic factor and both NR4A1 and Sp TFs exhibit similar functions in pancreatic cancer cells and regulate cell growth, survival, migration and invasion. There is also evidence that Sp TFs and NR4A1 regulate some of the same genes including survivin, epidermal growth factor receptor, PAX3-FOXO1, α5- and α6-integrins, β1-, β3- and β4-integrins; this is due to NR4A1 acting as a cofactor and mediating NR4A1/Sp1/4-regulated gene expression through GC-rich gene promoter sites. Several studies show that drugs targeting Sp downregulation or NR4A1 antagonists are highly effective inhibitors of Sp/NR4A1-regulated pathways and genes in pancreatic and other cancer cells, and the triterpenoid celastrol is a novel dual-acting agent that targets both Sp TFs and NR4A1.

miR-375-3p suppresses tumorigenesis and partially reverses chemoresistance by targeting YAP1 and SP1 in colorectal cancer cells

Clinically, one of the principal factors in the failure of advanced colorectal cancer (CRC) treatment is chemoresistance to 5-fluorouracil (5FU)-based chemotherapy. Although microRNA-375-3p (miR-375) is considered a tumor suppressor in multiple cancers, the mechanism of miR-375 in the regulation of drug resistance in CRC remains unclear. In this study, we investigated the chemosensitivity of miR-375 to 5FU in CRC from biological and clinical aspects. We found that miR-375 was significantly downregulated in CRC tissues and cell lines, and low miR-375 expression was strongly correlated with poor overall survival in CRC patients. Overexpression of miR-375 sensitized CRC cells to a broad spectrum of chemotherapeutic drugs in vitro and in vivo. Further mechanistic analysis demonstrated that miR-375 enhanced CRC cell sensitivity to 5FU by directly targeting YAP1 and SP1. MiR-375 downregulated YAP1, resulting in reduced expression of the Hippo-YAP1 pathway downstream genes CTGF, cyclin D1 and BIRC5 (also known as survivin). Overall, miR-375 was confirmed as a prospective molecular biomarker in the chemoresistance and prognosis of CRC patients, and the synergy between miR-375 and chemotherapeutic drugs could be a promising therapeutic strategy for CRC patients, especially with chemoresistance.

Role of Sp1 expression in gastric cancer: A meta-analysis and bioinformatics analysis

Sp1 (specificity protein 1) is an important transcription factor that regulates multiple cancer-related genes. A number of published studies have explored the relationship between Sp1 expression and prognosis in gastric cancer. Therefore, a deeper level of understanding is required into the molecular biological mechanism of gastric cancer. Finding new tumor biomarkers for the accurate prediction of occurrence, recurrence and metastasis of gastric cancer are of great significance. The present study uses a systematic meta-analysis and bioinformatics analysis to acquire evidence for a prognosis marker based on Sp1 expression in gastric cancer. A literature search was performed using PubMed and China National Knowledge Infrastructure on 8th June, 2018. A total of 13 studies were included in the meta-analysis. The meta-analysis showed that the expression of Sp1 was significantly higher in gastric cancer tissue, compared with that of normal mucosa [odds ratio (OR), −0.53; 95% CI, −0.62–0.44; P<0.0001] and dysplasia (OR, 0.24; 95% CI, 0.13–0.44; P<0.0001). A positive association was found Sp1 expression and depth of invasion (OR, 0.31; 95% CI, 0.11–0.86), lymph node metastasis (OR, 0.36; 95% CI, 0.22–0.59), TNM staging of gastric cancer (OR, 0.43; 95% CI, 0.24–0.79) and Lauren's classification (OR, 0.83; 95% CI, 0.51–1.36), but not with sex or tumor differentiation (OR, 1.34; 95% CI, 0.95–1.88). According to the Oncomine database, Sp1 mRNA expression is significantly higher in gastric cancer tissues compared with that in normal tissues (P<0.05), including that of intestinal, diffuse and mixed-type gastric carcinomas (P<0.05). Kaplan-Meier plots show that the expression of Sp1 mRNA is negatively associated with overall and progression-free survival rates of patients with gastric cancer, even when stratified according to expression level (P<0.05). The selected prediction parameter is overall survival or progressive-free survival rate. The expression level of Sp1 was divided into high expression group and low expression group according to the best cut off value provided on the Kaplan-Meier plotter. However, Sp1 protein expression is upregulated in gastric cancer tissues compared with normal tissues and is positively associated with depth of invasion and TNM stage of gastric cancer. The high protein expression of Sp1 might make it a good potential marker for the prognosis of patients with gastric cancer.

Reactive Oxygen Species (ROS)-Inducing Triterpenoid Inhibits Rhabdomyosarcoma Cell and Tumor Growth through Targeting Sp Transcription Factors

Methyl 2-trifluoromethyl-3,11-dioxo-18β-olean-1,12-dien-3-oate (CF₃DODA-Me) is derived synthetically from glycyrrhetinic acid, a major component of licorice, and this compound induced reactive oxygen species (ROS) in RD and Rh30 rhabdomyosarcoma (RMS) cells. CF₃DODA-Me also inhibited growth and invasion and induced apoptosis in RMS cells, and these responses were attenuated after cotreatment with the antioxidant glutathione, demonstrating the effective anticancer activity of ROS in RMS. CF₃DODA-Me also downregulated expression of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 and prooncogenic Sp-regulated genes including PAX3-FOXO1 (in Rh30 cells). The mechanism of CF₃DODA-Me-induced Sp-downregulation involved ROS-dependent repression of c-Myc and cMyc-regulated miR-27a and miR-17/20a, and this resulted in induction of the miRNA-regulated Sp repressors ZBTB4, ZBTB10, and ZBTB34. The cell and tumor growth effects of CF₃DODA-Me further emphasize the sensitivity of RMS cells to ROS inducers and their potential clinical applications for treating this deadly disease. IMPLICATIONS: CF₃DODA-Me and HDAC inhibitors that induce ROS-dependent Sp downregulation could be developed for clinical applications in treating rhabdomyosarcoma.

MicroRNA-22 suppresses the growth, migration and invasion of colorectal cancer cells through a Sp1 negative feedback loop

MicroRNAs have recently emerged as regulators of many biological processes including cell proliferation, development and differentiation. This study identified that miR-22 was statistically decreased in colorectal cancer clinical specimens and highly metastatic cell lines. Moreover, low miR-22 expression was associated with tumor metastasis, advanced clinical stage and relapse. Consistent with clinical observations, miR-22 significantly suppressed the ability of colorectal cancer cells to growth and metastasize in vitro and in vivo. Sp1 was validated as a target of miR-22, and ectopic expression of Sp1 compromised the inhibitory effects of miR-22. In addition, Sp1 repressed miR-22 transcription by binding to the miR-22 promoter, hence forming a negative feedback loop. Further study has shown that miR-22 suppresses the activity of PTEN/AKT pathway by Sp1. Our present results implicate the newly indentified miR-22/Sp1/PTEN/AKT axis might represent a potential therapeutic target for colorectal cancer.

Specificity Protein Transcription Factors and Cancer: Opportunities for Drug Development

Specificity protein (Sp) transcription factors (TFs) such as Sp1 are critical for early development but their expression decreases with age and there is evidence that transformation of normal cells to cancer cells is associated with upregulation of Sp1, Sp3, and Sp4, which are highly expressed in cancer cells and tumors. Sp1 is a negative prognostic factor for pancreatic, colon, glioma, gastric, breast, prostate, and lung cancer patients. Functional studies also demonstrate that Sp TFs regulate genes responsible for cancer cell growth, survival, migration/invasion, inflammation and drug resistance, and Sp1, Sp3 and Sp4 are also nononcogene addiction (NOA) genes and important drug targets. The mechanisms of drug-induced downregulation of Sp TFs and pro-oncogenic Sp-regulated genes are complex and include ROS-dependent epigenetic pathways that initially decrease expression of the oncogene cMyc. Many compounds such as curcumin, aspirin, and metformin that are active in cancer prevention also exhibit chemotherapeutic activity and these compounds downregulate Sp TFs in cancer cell lines and tumors. The effects of these compounds on downregulation of Sp TFs in normal cells and the contribution of this response to their chemopreventive activity have not yet been determined. Cancer Prev Res; 11(7); 371-82. ©2018 AACR.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

Specificity protein (Sp) transcription factors and metformin regulate expression of the long non-coding RNA HULC

Specificity protein 1 (Sp1) transcription factor (TF) regulates expression of long non-coding RNAs (lncRNAs) in hepatocellular carcinoma (HCC) cells. RNA interference (RNAi) studies showed that among several lncRNAs expressed in HepG2, SNU-449 and SK-Hep-1 cells, highly upregulated in liver cancer (HULC) was regulated not only by Sp1 but also Sp3 and Sp4 in the three cell lines. Knockdown of Sp transcription factors and HULC by RNAi showed that they play important roles in HCC cell proliferation, survival and migration. The relative contribution of Sp1, Sp3, Sp4 and HULC on these responses in HepG2, SNU-449 and SK-Hep-1 cells were cell context- and response-dependent. In the poorly differentiated SK-Hep-1 cells, knockdown of Sp1 or HULC resulted in genomic and morphological changes, indicating that Sp1 and Sp1-regulated HULC are important for maintaining the mesenchymal phenotype in this cell line. Genomic analysis showed an inverse correlation between expression of genes after knockdown of HULC and expression of those genes in liver tumors from patients. The antidiabetic drug metformin down-regulates Sp proteins in pancreatic cancer, and similar results including decreased HULC expression were observed in HepG2, SNU-449 and SK-Hep-1 cells treated with metformin, indicating that metformin and other antineoplastic agents that target Sp proteins may have clinical applications for HCC chemotherapy.

Specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 are non-oncogene addiction genes in cancer cells

Specificity protein (Sp) transcription factor (TF) Sp1 is overexpressed in multiple tumors and is a negative prognostic factor for patient survival. Sp1 and also Sp3 and Sp4 are highly expressed in cancer cells and in this study, we have used results of RNA interference (RNAi) to show that the three TFs individually play a role in the growth, survival and migration/invasion of breast, kidney, pancreatic, lung and colon cancer cell lines. Moreover, tumor growth in athymic nude mice bearing L3.6pL pancreatic cancer cells as xenografts were significantly decreased in cells depleted for Sp1, Sp3 and Sp4 (combined) or Sp1 alone. Ingenuity Pathway Analysis (IPA) of changes in gene expression in Panc1 pancreatic cancer cells after individual knockdown of Sp1, Sp3 and Sp4 demonstrates that these TFs regulate genes and pathways that correlated with the functional responses observed after knockdown but also some genes and pathways that inversely correlated with the functional responses. However, causal IPA analysis which integrates all pathway-dependent changes in all genes strongly predicted that Sp1-, Sp3- and Sp4-regulated genes were associated with the pro-oncogenic activity. These functional and genomic results coupled with overexpression of Sp transcription factors in tumor vs. non-tumor tissues and decreased Sp1 expression with age indicate that Sp1, Sp3 and Sp4 are non-oncogene addiction (NOA) genes and are attractive drug targets for individual and combined cancer chemotherapies.

Sulindac sulfide inhibits colon cancer cell growth and downregulates specificity protein transcription factors

Background

Specificity protein (Sp) transcription factors play pivotal roles in maintaining the phenotypes of many cancers. We hypothesized that the antineoplastic effects of sulindac and its metabolites were due, in part, to targeting downregulation of Sp transcription factors.

Methods

The functional effects of sulindac, sulindac sulfone and sulindac sulfide on colon cancer cell proliferation were determined by cell counting. Effects of these compounds on expression of Sp1, Sp3, Sp4 and pro-oncogenic Sp-regulated genes were determined by western blot analysis of whole cell lysates and in transient transfection assays using GC-rich constructs.

Results

Sulindac and its metabolites inhibited RKO and SW480 colon cancer cell growth and the order of growth inhibitory potency was sulindac sulfide > > sulindac sulfone > sulindac. Treatment of SW480 and RKO cells with sulindac sulfide downregulated expression of Sp1, Sp3 and Sp4 proteins. Sulindac sulfide also decreased expression of several Sp-regulated genes that are critical for cancer cell survival, proliferation and angiogenesis and these include survivin, bcl-2, epidermal growth factor receptor (EGFR), cyclin D1, p65 subunit of NFκB and vascular endothelial growth factor (VEGF). Sulindac sulfide also induced reactive oxygen species (ROS) and decreased the level of microRNA-27a in colon cancer cells, which resulted in the upregulation of the Sp-repressor ZBTB10 and this resulted in downregulation of Sp proteins.

Conclusions

The results suggest that the cancer chemotherapeutic effects of sulindac in colon cancer cells are due, in part, to its metabolite sulindac sulfide which downregulates Sp transcription factors and Sp-regulated pro-oncogenic gene products.

Transcription factor Sp1, also known as specificity protein 1 as a therapeutic target

INTRODUCTION

Specificity protein (Sp) transcription factors (TFs) are members of the Sp/Kruppel-like factor family, and Sp proteins play an important role in embryonic and early postnatal development. Sp1 has been the most extensively investigated member of this family, and expression of this protein decreases with age, whereas Sp1 and other family members (Sp3 and Sp4) are highly expressed in tumors and cancer cell lines.

AREA COVERED

The prognostic significance of Sp1 in cancer patients and the functional pro-oncogenic activities of Sp1, Sp3 and Sp4 in cancer cell lines are summarized. Several different approaches have been used to target downregulation of Sp TFs and Sp-regulated genes, and this includes identification of different structural classes of antineoplastic agents including NSAIDs, natural products and their synthetic analogs and several well-characterized drugs including arsenic trioxide, aspirin and metformin. The multiple pathways involved in drug-induced Sp downregulation are also discussed.

EXPERT OPINION

The recognition by the scientific and clinical community that experimental and clinically used antineoplastic agents downregulate Sp1, Sp3 and Sp4, and pro-oncogenic Sp-regulated genes will facilitate future clinical applications for individual drug and drug combination therapies that take advantage of their unusual effects.

Increased expression of colonic Wnt9A through Sp1-mediated transcriptional effects involving arylsulfatase B, chondroitin 4-sulfate, and galectin-3

In cultured human colonic epithelial cells and mouse colonic tissue, exposure to the common food additive carrageenan leads to inflammation, activation of Wnt signaling, increased Wnt9A expression, and decline in the activity of the enzyme arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase). In this study, the novel transcriptional mechanism by which carrageenan and decline in ARSB increase Wnt9A expression in NCM460 and HT-29 human colonic epithelial cells and in mouse colon is presented. Increased expression of Wnt9A has been associated with multiple malignancies, including colon carcinoma, and with ectodermal and mesoendodermal morphogenesis. When ARSB activity was reduced by siRNA or by exposure to carrageenan (1 μg/ml for 24 h), degradation of chondroitin 4-sulfate (C4S) was inhibited, leading to accumulation of more highly sulfated C4S, which binds less galectin-3, a β-galactoside-binding protein. Nuclear galectin-3 increased and mediated increased binding of Sp1 to the Sp1 consensus sequence in the Wnt9A promoter, shown by oligonucleotide-binding assay and by chromatin immunoprecipitation assay. When galectin-3 was silenced, the increases in Sp1 binding to the Wnt9A promoter and in Wnt9A expression, which followed carrageenan or ARSB silencing, were inhibited. Mithramycin A, a specific inhibitor of Sp1 oligonucleotide binding, and Sp1 siRNA blocked the carrageenan- and ARSB siRNA-induced increases in Wnt9A expression. These studies reveal how carrageenan exposure can lead to transcriptional events in colonic epithelial cells through decline in arylsulfatase B activity, with subsequent impact on C4S, galectin-3, Sp1, and Wnt9A and can exert significant effects on Wnt-initiated signaling and related vital cell processes.

Src activity is increased in gastrointestinal stromal tumors--analysis of associations with clinical and other molecular tumor characteristics

BACKGROUND

Increased activity of Src has been found in several human cancers, and often is associated with poor clinical outcome. The present study aimed to determine whether Src activity is increased in gastrointestinal stromal tumors (GIST), and whether it correlates with established tumor or patient characteristics and prognosis.

METHODS

Tumor/normal tissues of 29 patients were analyzed for Src activity/protein with kinase assays, and for VEGF/VEGFR with immunohistochemical staining.

RESULTS

Src activity was higher in tumor than in normal tissues (P = 0.093). However, when imatinib responders were excluded from the analyses, it was significantly higher in the tumor tissue (P = 0.017). Additionally, it was higher in primary compared to recurrent tumors or metastasis (P = 0.04). Univariate survival analysis showed a longer overall survival for patients with high Src activity (P = 0.038). In multivariate analysis, the response to imatinib treatment was the only survival-influencing factor (P = 0.072).

CONCLUSIONS

Src activity is increased in GIST. In contrast to most other tumor entities, it does not correlate with poor clinical outcome, but decreases during the progression from primary tumor to recurrence and metastasis, especially under therapy with imatinib. Additionally, our results show that higher Src activity is associated with longer overall survival.

COX-2, TFF1, and Src define better prognosis in young patients with gastric cancer

BACKGROUND AND OBJECTIVES

Despite its dwindling occurrence, gastric cancer remains a leading cause of cancer related mortality worldwide. Molecular determinants of prognosis that impact survival are being sought out as a means to facilitate rational clinical decision-making and enhance patient management. In this study, we evaluated three molecules implicated in gastric carcinogenesis and demonstrated that the differential expression of cyclooxygenase-2 (COX-2) and the viral oncogene homolog Src proteins could explain the differences in survival observed in patients older and younger than 50 years of age.

METHODS

We evaluated 5-year survival in a cohort of 423 gastric cancer patients using chronological age as a variable. Additionally, we assessed the protein expression of three molecules (COX-2, TFF1, Src) implicated in the pathogenesis of gastric cancer using immunohistochemistry.

RESULTS

We found that patients younger than 50 years of age had a better 5-year survival rate in all tumor stages. We found that the expression of COX-2 and Src correlated significantly with survival in this group without any significant impact attributable to TFF1.

CONCLUSIONS

Our study demonstrates that young gastric cancer patients have a better prognostic outlook that could in part be explained by the differential expression of COX-2 and Src.

Role of urokinase receptor in tumor progression and development

Elevated level of urokinase receptor (uPAR) is detected in various aggressive cancer types and is closely associated with poor prognosis of cancers. Binding of uPA to uPAR triggers the conversion of plasminogen to plasmin and the subsequent activation of metalloproteinases. These events confer tumor cells with the capability to degrade the components of the surrounding extracellular matrix, thus contributing to tumor cell invasion and metastasis. uPA-uPAR interaction also elicits signals that stimulate cell proliferation/survival and the expression of tumor-promoting genes, thus assisting tumor development. In addition to its interaction with uPA, uPAR also interacts with vitronectin and this interaction promotes cancer metastasis by activating Rac and stimulating cell migration. Although underlying mechanisms are yet to be fully elucidated, uPAR has been shown to facilitate epithelial-mesenchymal transition (EMT) and induce cancer stem cell-like properties in breast cancer cells. The fact that uPAR lacks intracellular domain suggests that its signaling must be mediated through its co-receptors. Indeed, uPAR interacts with diverse transmembrane proteins including integrins, ENDO180, G protein-coupled receptors and growth factor receptors in cancer cells and these interactions are proven to be critical for the role of uPAR in tumorigenesis. Inhibitory peptide that prevents uPA-uPAR interaction has shown the promise to prolong patients' survival in the early stage of clinical trial. The importance of uPAR's co-receptor in uPAR's tumor-promoting effects implicate that anti-cancer therapeutic agents may also be developed by disrupting the interactions between uPAR and its functional partners.

Brain metastases from colorectal cancer: microenvironment and molecular mechanisms

Colorectal cancer is one of the most common digestive tract malignancies in the world. Owing to the newer and more effective systemic therapies, the life of colorectal cancer patients can be remarkably prolonged, and the incidence of brain metastases is increasing. However, little is known about the underlying mechanisms of brain metastasis from colorectal cancer. Here we review the tumor microenvironment and metastasis associated molecules in brain metastases from colorectal cancer. A further understanding of these mechanisms will help us to propose better strategies for colorectal cancer patients with brain metastasis and improve their life quality.

Stromal cell-derived factor-1/CXC receptor 4 and β1 integrin interaction regulates urokinase-type plasminogen activator expression in human colorectal cancer cells

The stromal cell-derived factor-1 (SDF-1)/CXC receptor 4 (CXCR4) axis has been shown to play a role in colorectal cancer progression. In addition, the protease urokinase-type plasminogen activator (uPA) is an important factor in tumor cell invasion and metastasis. However, the mechanism by which SDF-1 mediates uPA expression in human colorectal cancer cells remains unknown. We investigated the molecular mechanism governing the interaction between SDF-1 stimulation and uPA expression in three human colon cancer cell lines (DLD-1, SW48, and COLO 205). We found that SDF-1 stimulation led to an increase in the expression and secretion of uPA in these cells. Experiments involving specific inhibitors and small interfering RNA demonstrated that the activation of p38 mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt pathways are critical for SDF-1-induced uPA expression. Analysis of transcription factor binding using ELISA and chromatin immunoprecipitation assays revealed that SDF-1 increased Sp1- and AP-1-DNA-binding activities in DLD-1 cells. Inhibition of Sp1 and AP-1 activation blocked the SDF-1-induced expression and activity of the uPA promoter. The effect of SDF-1 on DLD-1 signaling and uPA expression was mediated by the CXCR4/β1 integrin axis. In summary, our findings elucidate the mechanisms of SDF-1/CXCR4 downstream signaling and provide insights into the function of SDF-1 in colon cancer cells.

The effect of focal adhesion kinase gene silencing on 5-fluorouracil chemosensitivity involves an Akt/NF-kappaB signaling pathway in colorectal carcinomas

Multicellular resistance (MCR) is produced because multicellular spheroids (MCSs) are formed with a broad cell-cell connection when cultured in three-dimensions, which limits the clinical treatment efficacy in solid tumors. Focal adhesion kinase (FAK) plays an important role in apoptosis, survival and cell adhesion between cells and their extracellular matrix. In this study, we investigated the expressions of FAK, Akt and NF-kappaB in human colorectal cancer (CRC), and the effects of FAK gene silencing on MCSs formation and 5-fluorouracil (5-FU) chemosensitivity in colon carcinoma MCSs culture cells. In CRC samples, FAK, Akt and NF-kappaB were overexpressed. The positive expression of FAK correlated notably with lymph node metastasis and cellular differentiation. Positive expressions of Akt and NF-kappaB were significantly related to cellular differentiation and lymph node metastasis, respectively. Furthermore, positive expression of FAK correlated with that of Akt and NF-kappaB. The expression of FAK was inhibited significantly by a small hairpin RNA targeting FAK. Knockdown of FAK reversed the formation and aggregation of MCSs, significantly decreased the 50% inhibitory concentration of 5-FU, and markedly increased MCS culture cells apoptosis. These effects were associated with reduced levels of Akt and NF-kappaB. These results indicate that suppressing FAK expression potentiated 5-FU-induced cytotoxicity and contributed to its chemosensitizing effect by suppressing Akt/NF-kappaB signaling in colon carcinoma MCS culture cells. These data also imply that FAK mediates MCR of CRC through the survival signaling pathway FAK/Akt/NF-kappaB.

Translational research on u-PAR

The urokinase receptor (u-PAR) is one of the most critical molecules in migration, invasion, intravasation, and metastasis and is also a key regulator between tumour cell proliferation and dormancy. It is overexpressed in most human solid cancer types, which has led to increasing translational and clinical research on this molecule. The current review discusses in particular the in vivo, translational, and putative clinical relevance of u-PAR in the context of this latest development. It outlines how u-PAR is already being used and might increasingly be applied as a diagnostic tool, for example, in distinguishing benign from malignant neoplasms, as a molecular marker for predicting clinical response to chemotherapy or novel targeted therapy, and finally as a promising tool for the development of novel cancer therapeutics.

Regulation of cell signalling by uPAR

Urokinase-type plasminogen activator receptor (uPAR) expression is elevated during inflammation and tissue remodelling and in many human cancers, in which it frequently indicates poor prognosis. uPAR regulates proteolysis by binding the extracellular protease urokinase-type plasminogen activator (uPA; also known as urokinase) and also activates many intracellular signalling pathways. Coordination of extracellular matrix (ECM) proteolysis and cell signalling by uPAR underlies its important function in cell migration, proliferation and survival and makes it an attractive therapeutic target in cancer and inflammatory diseases. uPAR lacks transmembrane and intracellular domains and so requires transmembrane co-receptors for signalling. Integrins are essential uPAR signalling co-receptors and a second uPAR ligand, the ECM protein vitronectin, is also crucial for this process.

Data recovery and integration from public databases uncovers transformation-specific transcriptional downregulation of cAMP-PKA pathway-encoding genes

BACKGROUND

The integration of data from multiple genome-wide assays is essential for understanding dynamic spatio-temporal interactions within cells. Such integration, which leads to a more complete view of cellular processes, offers the opportunity to rationalize better the high amount of "omics" data freely available in several public databases.In particular, integration of microarray-derived transcriptome data with other high-throughput analyses (genomic and mutational analysis, promoter analysis) may allow us to unravel transcriptional regulatory networks under a variety of physio-pathological situations, such as the alteration in the cross-talk between signal transduction pathways in transformed cells.

RESULTS

Here we sequentially apply web-based and statistical tools to a case study: the role of oncogenic activation of different signal transduction pathways in the transcriptional regulation of genes encoding proteins involved in the cAMP-PKA pathway. To this end, we first re-analyzed available genome-wide expression data for genes encoding proteins of the downstream branch of the PKA pathway in normal tissues and human tumor cell lines. Then, in order to identify mutation-dependent transcriptional signatures, we classified cancer cells as a function of their mutational state. The results of such procedure were used as a starting point to analyze the structure of PKA pathway-encoding genes promoters, leading to identification of specific combinations of transcription factor binding sites, which are neatly consistent with available experimental data and help to clarify the relation between gene expression, transcriptional factors and oncogenes in our case study.

CONCLUSIONS

Genome-wide, large-scale "omics" experimental technologies give different, complementary perspectives on the structure and regulatory properties of complex systems. Even the relatively simple, integrated workflow presented here offers opportunities not only for filtering data noise intrinsic in high throughput data, but also to progressively extract novel information that would have remained hidden otherwise. In fact we have been able to detect a strong transcriptional repression of genes encoding proteins of cAMP/PKA pathway in cancer cells of different genetic origins. The basic workflow presented herein may be easily extended by incorporating other tools and can be applied even by researchers with poor bioinformatics skills.

Urokinase receptor, MMP-1 and MMP-9 are markers to differentiate prognosis, adenoma and carcinoma in thyroid malignancies

The identification of high-risk patients with thyroid cancer and the preoperative differentiation between follicular adenoma and carcinoma remain clinically challenging. Our study was conducted to analyze whether the quantification of matrix metalloproteinases (MMPs) and urokinase-type plasminogen activator receptor (u-PAR) and transcription factor binding to the u-PAR promoter improve prognostic predictability and differential diagnosis of thyroid tumors. Tumor/normal tissue was collected from 69 prospectively followed patients with thyroid carcinomas (papillary, medullary, follicular and anaplastic, PTC, MTC, FTC and ATC) or follicular adenomas. U-PAR, MMP-1, MMP-7 and MMP-9 amounts were determined by ELISA, and transcription factor binding was determined by electrophoretic mobility shift assay. Binding of transcription factors to the u-PAR promoter was observed, but not associated with u-PAR expression. Carcinomas except MTC expressed significantly more u-PAR/MMPs than adenomas/normal tissues, this being associated with advanced pT- or M-stages. MMP-1 and MMP-9 were significantly higher in follicular carcinomas than in adenomas. In carcinomas, high u-PAR-gene expression correlated significantly with high MMP-9, the latter being associated with MMP-7 in normal tissues. Poor survival in differentiated tumors was associated in trend (p = 0.07); poor survival of all patients (p = 0.043) and especially of patients with carcinomas of follicular origin (including ATC), but not medullary carcinomas, were significantly associated with high u-PAR-protein (p = 0.015). Quantification of u-PAR is of prognostic relevance in thyroid carcinomas of non-c-cell origin, and u-PAR in part may be regulated nontranscriptionally in thyroid cancers. This is the first study to suggest MMP-1/-9 as significant differentiation markers between follicular adenoma and follicular carcinoma.

Inhibition of STAT5 induces G1 cell cycle arrest and reduces tumor cell invasion in human colorectal cancer cells

Abnormalities in the signal transducer and activator of transcription (STAT) pathway are involved in the oncogenesis of several cancers. However, the mechanism by which dysregulated STAT5 signaling contributes to the progression of human colorectal cancer (CRC) has not been elucidated. To investigate the role of STAT5 in CRC progression, we depleted STAT5 with a small interfering RNA (siRNA). Our results demonstrate that STAT5 is involved in CRC cell growth, cell cycle progression, invasion and migration through regulation of gene expression, such as Bcl-2, p16(ink4a), p21(waf1/cip1), p27(kip1), E-cadherin, the focal adhesion kinase (FAK), vascular endothelial growth factor (VEGF) and matrix metalloproteinases. In addition, immunohistochemical staining reveals upregulation of STAT5 during CRC tumorigenesis. Moreover, phospho-STAT5 (pSTAT5) is predominantly localized in the cytoplasm of adenomas cells and colon adenocarcinoma cells, but primarily presented in the nucleus of normal colonic epithelium cells. Thus, pSTAT5 protein is shuttled from the nucleus to the cytoplasm in the oncogenesis of CRC, suggesting that activated STAT5 may also have cytoplasmic functions. In support of this hypothesis, we found that STAT5 formed a complex with p44/42 MAPK and SAPK/JNK in CRC cells, suggesting cross talk between STAT5 signaling and the MAPK pathway in the development of human CRC. Our findings illustrate the biological significance of STAT5 signaling in CRC progression, and provide novel evidence that intervention in STAT5 signaling may have potential therapeutic value in the prevention of human colorectal cancer.

Expression of the signal transducer and activator of transcription factor 3 and Janus kinase 3 in colorectal carcinomas, colonic adenomas and ulcerative colitis

BACKGROUND AND STUDY AIMS

Despite the growing understanding of the involvement of protooncogenes and tumour suppressor genes in the oncogenesis of CRC, the exact biological and molecular mechanisms underpinning this process remain poorly understood. The signal transducer and activator of transcription (STAT3) has been implicated in the regulation of growth and malignant transformation. Accumulating evidences have come to indicate that abnormalities in the Janus kinase (JAK)/STAT pathway are involved in oncogenesis of several cancers. The aim of this study was to investigate the expression of JAK3 and STAT3 in both normal and activated forms by immunohistochemistry in adenomas of the colon, ulcerative colitis and CRC compared to normal colonic mucosa.

PATIENTS AND METHODS

Tissues from 30 cases with primary CRC and seven cases with ulcerative colitis (UC), removed by colectomy, were included. In addition, tissues from 10 colonic adenomas, 15 CRC and eight cases with UC, obtained by endoscopic biopsies, were examined histopathologically. Immunohistochemical evaluation of STAT3, p-STAT3, JAK3 and p-JAK3 expression in tissue sections was completed. Statistical analysis and correlation of data were then performed.

RESULTS

Normal colonic mucosa showed expression of STAT3 only. Immunoreactivity of p-JAK3 increased significantly (p<0.05) and correlated with the degree of dysplasia in colonic adenomas. Immunoreactivity of p-STAT3 increased significantly (p<0.05) and correlated with the degree of dysplasia in cases with UC. In CRC a significant positive correlation was found between p-STAT3 expression and grading, STAT3, JAK3 and p-JAK3 and TNM or Dukes' staging, and p-STAT3 and nodal status excluding distant metastasis (p<0.05).

CONCLUSION

JAK3 and STAT3, and particularly their activated forms, were found to correlate significantly with the degree of dysplasia in adenomas and UC, indicating their potential role in colorectal carcinogenesis. They also correlate with anaplasia and invasion, suggesting a definitive role in progression of CRC.

Dual role of Sp3 transcription factor as an inducer of apoptosis and a marker of tumour aggressiveness

BACKGROUND

The ambiguous role of transcription factor Sp3 for tumour progression is still debated since it was described as a transcriptional repressor or activator. Here we tried to decipher the molecular mechanisms implicated in Sp3 accumulation observed in aggressive tumours.

METHODOLOGY

We generated normal and tumour cell lines conditionally expressing Sp3. Cell growth was analyzed in vitro and after inoculation in nude mice. Apoptosis was assessed by pan- caspase activity assays, by counting fragmented nuclei and by determination of caspase 9 cleavage. Gene expression was determined by quantitative PCR. Cleavage by different caspases was performed after in vitro translation of the Sp3 cDNA in the presence of [S(35)] labelled methionine. Different tumour cell lines and head and neck tumour samples were tested for the presence of Sp3 by western blots. Correlation between Sp3 expression and overall survival has been statistically determined.

PRINCIPAL FINDINGS

Conditional over-expression of Sp3 induces apoptosis and modifies expression of genes implicated in the regulation of cell cycle and pro and anti apoptotic genes. Sp3 over-expression strongly reduces the development of tumours in nude mice confirming its pro-apoptotic potential in vivo. However, cells can survive to apoptosis through selective Sp3 cleavage by caspase. Sp3 induction in established tumours resulted in transient regression then progression. Progression coincides with re-accumulation of the full length form of Sp3. Sp3 is over-expressed in tumour cell lines of different origins. The presence of high levels of the full-length form of Sp3 indicates a poor prognosis for overall survival of patients with head and neck tumours.

CONCLUSIONS

Full length Sp3 accumulation highlights bypass of tumour cell apoptotic capacities and is indicative of head and neck tumours aggressiveness.

Inhibition of JAK1, 2/STAT3 signaling induces apoptosis, cell cycle arrest, and reduces tumor cell invasion in colorectal cancer cells

Abnormalities in the STAT3 pathway are involved in the oncogenesis of several cancers. However, the mechanism by which dysregulated STAT3 signaling contributes to the progression of human colorectal cancer (CRC) has not been elucidated, nor has the role of JAK, the physiological activator of STAT3, been evaluated. To investigate the role of both JAK and STAT3 in CRC progression, we inhibited JAK with AG490 and depleted STAT3 with a SiRNA. Our results demonstrate that STAT3 and both JAK1 and 2 are involved in CRC cell growth, survival, invasion, and migration through regulation of gene expression, such as Bcl-2, p1(6ink4a), p21(waf1/cip1), p27(kip1), E-cadherin, VEGF, and MMPs. Importantly, the FAK is not required for STAT3-mediated regulation, but does function downstream of JAK. In addition, our data show that proteasome-mediated proteolysis promotes dephosphorylation of the JAK2, and consequently, negatively regulates STAT3 signaling in CRC. Moreover, immunohistochemical staining reveals that nuclear staining of phospho-STAT3 mostly presents in adenomas and adenocarcinomas, and a positive correlation is found between phospho-JAK2 immunoreactivity and the differentiation of colorectal adenocarcinomas. Therefore, our findings illustrate the biologic significance of JAK1, 2/STAT3 signaling in CRC progression and provide novel evidence that the JAK/STAT3 pathway may be a new potential target for therapy of CRC.

Src continues aging: current and future clinical directions

Aberrant activation of members of the Src family of nonreceptor protein tyrosine kinases is common in solid tumor malignancies and may contribute to the development and/or progression of these tumors. As a result, four Src inhibitors are now in more than 50 clinical trials for at least 14 different types of solid tumors. In this review, we briefly discuss the preclinical rationale for Src inhibitors, the development strategies most likely to be successful in the clinic, and the rationale for Src inhibitors in combination with other agents as part of a more comprehensive therapeutic strategy. As the use of Src family inhibitors in clinical trials on solid tumors is in its infancy, further studies on the roles of Src family kinases in tumor progression, chemoresistance, epidermal-to-mesenchymal transition, and other properties of tumor progression will be important in designing the most effective clinical trials using these inhibitors.

Regulation of angiogenesis and vascular permeability by Src family kinases: opportunities for therapeutic treatment of solid tumors

Aberrant expression or activation of protein tyrosine kinases, including Src and related Src family kinases, is a common occurrence in many human cancers, resulting in deregulation of expression of numerous mediators of cellular functions, including pro-angiogenic molecules. In addition, Src activation regulates vascular permeability of endothelial cells. How these processes contribute to tumor progression and metastasis are the subjects of this review. As Src-selective inhibitors have entered clinical trials for a number of solid tumors, further understanding of the roles of Src kinases in mediating tumor angiogenesis as well as modulating tumor/microenvironment interactions will provide insights into the best use of these inhibitors in treating patients afflicted with tumors in which Src is activated.

Synergistic effects of a combination of dietary factors sulforaphane and (-) epigallocatechin-3-gallate in HT-29 AP-1 human colon carcinoma cells

PURPOSE

The objective of this study was to investigate combinations of two chemopreventive dietary factors: EGCG 20 microM (or 100 microM) and SFN (25 microM) in HT-29 AP-1 human colon carcinoma cells.

METHODS

After exposure of HT-29 AP-1 cells to SFN and EGCG, individually or in combination, we performed AP-1 luciferase reporter assays, cell viability assays, isobologram analyses, senescence staining, quantitative real-time PCR (qRT-PCR) assays, Western blotting, and assays for HDAC activity and hydrogen peroxide. In some experiments, we exposed cells to superoxide dismutase (SOD) or Trichostatin A (TSA) in addition to the treatment with dietary factors.

RESULTS

The combinations of SFN and EGCG dramatically enhanced transcriptional activation of AP-1 reporter in HT-29 cells (46-fold with 25 microM SFN and 20 microM EGCG; and 175-fold with 25 microM SFN and 100 microM EGCG). Isobologram analysis showed synergistic activation for the combinations with combination index, CI < 1. Interestingly, co-treatment with 20units/ml of SOD, a free radical scavenger, attenuated the synergism elicited by the combinations (2-fold with 25 muM SFN and 20 muM EGCG; and 15-fold with 25 microM SFN and 100 microM EGCG). Cell viability assays showed that the low-dose combination decreased cell viability to 70% whereas the high-dose combination decreased cell viability to 40% at 48 h, with no significant change in cell viability at 24 h as compared to control cells. In addition, 20 microM and 100 microM EGCG, but not 25 microM SFN, showed induction of senescence in the HT-29 AP-1 cells subjected to senescence staining. However, both low- and high-dose combinations of SFN and EGCG attenuated the cellular senescence induced by EGCG alone. There was no significant change in the protein levels of phosphorylated forms of ERK, JNK, p38, and Akt-Ser473 or Akt-Thr308. Besides, qRT-PCR assays corroborated the induction of the luciferase gene seen with the combinations in the reporter assay. Relative expression levels of transcripts of many other genes known to be either under the control of the AP-1 promoter or involved in cell cycle regulation or cellular influx-efflux such as cyclin D1, cMyc, ATF-2, Elk-1, SRF, CREB5, SLCO1B3, MRP1, MRP2 and MRP3 were also quantified by qRT-PCR in the presence and absence of SOD at both 6 and 10 h. In addition, pre-treatment with 100 ng/ml TSA, a potent HDAC inhibitor, potentiated (88-fold) the synergism seen with the low-dose combination on the AP-1 reporter transcriptional activation. Cytoplasmic and nuclear fractions of treated cells were tested for HDAC activity at 2 and 12 h both in the presence and absence of TSA, however, there was no significant change in their HDAC activity. In addition, the H2O2 produced in the cell system was about 2 microM for the low-dose combination which was scavenged to about 1 microM in the presence of SOD.

CONCLUSION

Taken together, the synergistic activation of AP-1 by the combination of SFN and EGCG that was potentiated by HDAC inhibitor TSA and attenuated by free radical scavenger SOD point to a possible multifactorial control of colon carcinoma that may involve a role for HDACs, inhibition of cellular senescence, and SOD signaling.

Src InducesUrokinase ReceptorGene Expression and Invasion/Intravasation via Activator Protein-1/p-c-Jun in Colorectal Cancer

The urokinase receptor [urokinase plasminogen activator receptor (u-PAR)] promotes invasion and metastasis and is associated with poor patient survival. Recently, it was shown that Src induces u-PAR gene expression via Sp1 bound to the u-PAR promoter region -152/-135. However, u-PAR is regulated by diverse promoter motifs, among them being an essential activator protein-1 (AP-1) motif at -190/-171. Moreover, an in vivo relevance of Src-induced transcriptional regulators of u-PAR-mediated invasion, in particular intravasation, and a relevance in resected patient tumors have not sufficiently been shown. The present study was conducted (a) to investigate if, in particular, AP-1-related transcriptional mediators are required for Src-induced u-PAR-gene expression, (b) to show in vivo relevance of AP-1-mediated Src-induced u-PAR gene expression for invasion/intravasation and for resected tissues from colorectal cancer patients. Src stimulation of the u-PAR promoter deleted for AP-1 region -190/-171 was reduced as compared with the wild-type promoter in cultured colon cancer cells. In gelshifts/chromatin immunoprecipitation, Src-transfected SW480 cells showed an increase of phospho-c-Jun, in addition to JunD and Fra-1, bound to region -190/-171. Src-transfected cells showed a significant increase in c-Jun phosphorylated at Ser(73) and also Ser(63), which was paralleled by increased phospho-c-jun-NH(2)-kinase. Significant decreases of invasion/in vivo intravasation (chorionallantoic membrane model) were observed in Src-overexpressing cells treated with Src inhibitors, u-PAR-small interfering RNA, and dominant negative c-Jun (TAM67). In resected tissues of 20 colorectal cancer patients, a significant correlation between Src activity, AP-1 complexes bound to u-PAR region -190/-171, and advanced pN stage were observed. These data suggest that Src-induced u-PAR gene expression and invasion/intravasation in vivo is also mediated via AP-1 region -190/-171, especially bound with c-Jun phosphorylated at Ser(73/63), and that this pathway is biologically relevant for colorectal cancer patients, suggesting therapeutic potential.