Knockdown of frizzled-7 inhibits cell growth and metastasis and promotes chemosensitivity of esophageal squamous cell carcinoma cells by inhibiting Wnt signaling

TAPI-1 Exhibits Anti-tumor Efficacy in Human Esophageal Squamous Cell Carcinoma Cells via Suppression of NF-κB Signaling Pathway

BACKGROUND

TNF-α processing inhibitor-1 (TAPI-1) is a known metalloproteinase inhibitor with potential anti-inflammatory effects. However, its anti-cancer effects on esophageal squamous cell carcinoma (ESCC) have not been uncovered.

AIM

In the present study, the effects of TAPI-1 on ESCC cell viability, migration, invasion, and cisplatin resistance and the underlying molecular mechanisms were investigated in TE-1 and Eca109 cells.

METHODS

To this end, TE-1 and Eca109 cells were exposed to TAPI-1 for indicated time intervals. Cell viability was assessed using cell counting kit-8 assay and apoptosis was evaluated using flow cytometry assay. Migration and invasion were assessed using Transwell assays. Gene expressions were analyzed using quantitative reverse transcription polymerase chain reaction. The activation of NF-κB signaling pathway was elucidated via Western blot and chromatin immunoprecipitation assay.

RESULTS

We observed that higher doses (10, 20 μM) of TAPI-1 inhibited ESCC cell viability, while a lower dose (5 μM) of TAPI-1 inhibited ESCC cell migration and invasion and enhanced the chemosensitivity of ESCC cells to cisplatin. Moreover, TAPI-1 suppressed the activation of NF-κB signaling and the target genes expression in the stage of transcription initiation. Furthermore, blocking NF-κB signaling in advance could abolish all the effects of TAPI-1 on ESCC cells.

CONCLUSION

Overall, these results indicated that TAPI-1 impairs ESCC cell viability, migration, and invasion and facilitates cisplatin-induced apoptosis via suppression of NF-κB signaling pathway. TAPI-1 may serve as a potential adjuvant agent with cisplatin for ESCC therapy.

Wnt Signaling Inhibitors and Their Promising Role in Tumor Treatment

In a continuous search for the improvement of antitumor therapies, the inhibition of the Wnt signaling pathway has been recognized as a promising target. The altered functioning of the Wnt signaling in human tumors points to the strategy of the inhibition of its activity that would impact the clinical outcomes and survival of patients. Because the Wnt pathway is often mutated or epigenetically altered in tumors, which promotes its activation, inhibitors of Wnt signaling are being intensively investigated. It has been shown that knocking down specific components of the Wnt pathway has inhibitory effects on tumor growth in vivo and in vitro. Thus, similar effects are expected from the application of Wnt inhibitors. In the last decades, molecules acting as inhibitors on the pathway’s specific molecular levels have been identified and characterized. This review will discuss the inhibitors of the canonical Wnt pathway, summarize knowledge on their effectiveness as therapeutics, and debate their side effects. The role of the components frequently mutated in various tumors that are principal targets for Wnt inhibitors is also going to be brought to the reader’s attention. Some of the molecules identified as Wnt pathway inhibitors have reached early stages of clinical trials, and some have only just been discovered. All things considered, inhibition of the Wnt signaling pathway shows potential for the development of future therapies.

Signaling pathways and their potential therapeutic utility in esophageal squamous cell carcinoma

Esophageal cancer is a complex gastrointestinal malignancy with an extremely poor outcome. Approximately 80% of cases of this malignancy in Asian countries including India are of squamous cell origin, termed Esophageal Squamous Cell Carcinoma (ESCC).The five-year survival rate in ESCC patients is less than 20%. Neo-adjuvant chemo-radiotherapy (NACRT) followed by surgical resection remains the major therapeutic strategy for patients with operable ESCC. However, resistance to NACRT and local recurrence after initial treatment are the leading cause of dismal outcomes in these patients. Therefore, an alternative strategy to promote response to the therapy and reduce the post-operative disease recurrence is highly needed. At the molecular level, wide variations have been observed in tumor characteristics among different populations, nevertheless, several common molecular features have been identified which orchestrate disease progression and clinical outcome in the malignancy. Therefore, determination of candidate molecular pathways for targeted therapy remains the mainstream idea of focus in ESCC research. In this review, we have discussed the key signaling pathways associated with ESCC, i.e., Notch, Wnt, and Nrf2 pathways, and their crosstalk during disease progression. We further discuss the recent developments of novel agents to target these pathways in the context of targeted cancer therapy. In-depth research of the signaling pathways, gene signatures, and a combinatorial approach may help in discovering targeted therapy for ESCC.

Unlocking the Wnt pathway: Therapeutic potential of selective targeting FZD7 in cancer

The Wnt signaling is of paramount pathophysiological importance. Despite showing promising anticancer activities in pre-clinical studies, current Wnt pathway inhibitors face complications in clinical trials resulting from on-target toxicity. Hence, the targeting of pathway component(s) that are essential for cancer but dispensable for normal physiology is key to the development of a safe Wnt signaling inhibitor. Frizzled₇ (FZD₇) is a Wnt pathway receptor that is redundant in healthy tissues but crucial in various cancers. FZD₇ modulates diverse aspects of carcinogenesis, including cancer growth, metastasis, maintenance of cancer stem cells, and chemoresistance. In this review, we describe state-of-the-art knowledge of the functions of FZD₇ in carcinogenesis and adult tissue homeostasis. Next, we overview the development of small molecules and biomolecules that target FZD₇. Finally, we discuss challenges and possibilities in developing FZD₇-selective antagonists.

Addressing cancer signal transduction pathways with antisense and siRNA oligonucleotides

Signal transduction pathways play key roles in the initiation, progression and dissemination of cancer. Thus, signaling molecules are attractive targets for cancer therapeutics and enormous efforts have gone into the development of small molecule inhibitors of these pathways. However, regrettably, there has been only moderate progress to date, primarily in connection with the RAS signaling pathway. Oligonucleotide-based drugs potentially offer several advantages for addressing signaling pathways, including their exquisite selectivity and their ability to exploit both enzymatic and nonenzymatic targets. Nonetheless, there are problems inherent in the oligonucleotide approach, not the least being the challenge of effectively delivering these complex molecules to intracellular sites within tumors. This survey article will provide a selective review of recent studies where oligonucleotides were used to address cancer signaling and will discuss both positive aspects and limitations of those studies. This will be set in the context of an overview of various cancer signaling pathways and small molecule approaches to regulate those pathways. The survey will also evaluate the challenges and opportunities implicit in the oligonucleotide-based approach to cancer signaling and will point out several possibilities for future research.

Expression of LGR5, FZD7, TROY, and MIST1 in Perioperatively Treated Gastric Carcinomas and Correlation with Therapy Response

The cancer stem cell model is considered as a putative cause of resistance to chemotherapy and disease recurrence in malignant tumors. In this study, we tested the hypothesis that the response to neoadjuvant/perioperative chemotherapy correlates with the expression of four different putative cancer stem cell markers of gastric cancer (GC), i.e., LGR5, FZD7, TROY, and MIST1. The expression of LGR5, FZD7, TROY, and MIST1 was assessed by immunohistochemistry in 119 perioperatively treated GCs including pretherapeutic biopsies, resected primary GCs, and corresponding nodal and distant metastases. All four markers were detected in our cohort with variable prevalence and histoanatomical distributions. Few tumor cells expressed TROY. LGR5, FZD7, and MIST1 were coexpressed in 41.2% and completely absent in 6.2%. The prevalence of LGR5- and FZD7-positive GCs was higher and of TROY-positive GCs lower in perioperatively treated GCs compared with treatment-naïve tumors. LGR5, FZD7, and MIST1 in the primary tumors correlated significantly with their expression in the corresponding lymph node metastasis. An increased expression of LGR5 in primary GC correlated significantly with tumor regression. The expression of MIST1 in lymph node metastases correlated significantly with the number of lymph node metastases as well as overall and tumor-specific survival. FZD7 did not correlate with any clinicopathological patient characteristic. Our study on clinical patient samples shows that GCs may coexpress independently different stem cell markers; that neoadjuvant/perioperative treatment of GC significantly impacts on the expression of stem cell markers, which cannot be predicted by the analysis of pretherapeutic biopsies; and that their expression and tumor biological effect are heterogeneous and have to be viewed as a function of histoanatomical distribution.

Functional roles of circular RNAs during epithelial-to-mesenchymal transition

Cancer has become a major health issue worldwide, contributing to a high mortality rate. Tumor metastasis is attributed to the death of most patients. Epithelial-to-mesenchymal transition (EMT) plays a vital role in inducing metastasis. During EMT, epithelial cells lose their characteristics, such as cell-to-cell adhesion and cell polarity, and cells gain motility, migratory potential, and invasive properties to become mesenchymal stem cells. Circular RNAs (circRNAs) are closely associated with tumor metastasis and patient prognosis, as revealed by increasing lines of evidence. CircRNA is a type of single-stranded RNA that forms a covalently closed continuous loop. CircRNAs are insensitive to ribonucleases and are widespread in body fluids. This work is the first review on EMT-related circRNAs. In this review, we briefly discuss the characteristics and functions of circRNAs. The correlation of circRNAs with EMT has been reported, and we discuss the ways circRNAs can regulate EMT progression through EMT transcription factors, EMT-related signaling pathways, and other mechanisms. This work summarizes current studies on EMT-related circRNAs in various cancers and provides a theoretical basis for the use of EMT-related circRNAs in targeted management and therapy.

MicroRNA-488 inhibits endometrial glandular epithelial cell proliferation, migration, and invasion in endometriosis mice via Wnt by inhibiting FZD7

Endometriosis is a chronic inflammatory syndrome and nearly 6%‐10% of women are affected by it during the reproductive period. Previous studies have proved that microRNAs (miRNAs) are implicated in the pathogenesis of ovarian endometriosis. In this study, we aimed to investigate that restored miR‐488 would effectively inhibit the development of endometriosis. The microarray‐based data analysis was performed to screen endometriosis‐related differentially expressed genes (DEGs). The mouse model in endometriosis syndrome was established by being subcutaneously injected with Estradiol benzoate, and the ectopic endometrial tissues and normal endometrial tissues were collected. Additionally, the endometrial glandular epithelial cells were extracted from the endometrial glandular epithelial tissues from normal and endometriosis mice. In order to examine the role of miR‐488 in mice with endometriosis, we measured miR‐488 expression and expression levels of Frizzled‐7 (FZD7), cyclinD1, β‐catenin, and c‐Myc in vivo and in vitro. Finally, we detected the effect of miR‐488 on cell proliferation, apoptosis, migration and invasion in vitro. FZD7 was upregulated in human endometriosis. The data showed higher expression levels of FZD7, β‐catenin, c‐Myc and cyclinD1, and lower miR‐488 expression in mouse endometrial tissues. FZD7 was the target gene of miR‐488. Furthermore, elevated miR‐488 in isolated mouse endometrial glandular endometrial cells inhibited FZD7, the translocation of β‐catenin to nucleus, the activation of Wnt pathway, and the cell proliferation, migration and invasion. Collectively, these findings indicated that up‐regulated miR‐488 may reduce the proliferation, migration and invasion of endometrial glandular epithelial cells through inhibiting the activation of Wnt pathway by down‐regulating FZD7.

Wnt receptor Frizzled 8 is a target of ERG in prostate cancer

Prostate cancer (PCa) is one of the most frequently diagnosed cancers among men. Many molecular changes have been detailed during PCa progression. The gene encoding the transcription factor ERG shows recurrent rearrangement, resulting in the overexpression of ERG in the majority of prostate cancers. Overexpression of ERG plays a critical role in prostate oncogenesis and development of metastatic disease. Among the downstream effectors of ERG, Frizzled family member FZD4 has been shown to be a target of ERG. Frizzled-8 (FZD8) has been shown to be involved in PCa bone metastasis. In the present study, we show that the expression of FZD8 is directly correlated with ERG expression in PCa. Furthermore, we show that ERG directly targets and activates FZD8 by binding to its promoter. This activation is specific to ETS transcription factor ERG and not ETV1. We propose that ERG overexpression in PCa leads to induction of Frizzled family member FZD8, which is known to activate the Wnt pathway. Taken together, these findings uncover a novel mechanism for PCa metastasis, and indicate that FZD8 may represent a potential therapeutic target for PCa.

MicroRNA-504 functions as a tumor suppressor in hepatocellular carcinoma through inhibiting Frizzled-7-mediated-Wnt/β-catenin signaling

Accumulating evidence suggests that microRNAs (miRNAs) are critical regulators in the development and progression of various malignant tumors, including hepatocellular carcinoma (HCC). Multiple findings have indicated that miRNA-504 (miR-504) is dysregulated in several types of cancers, functioning as an oncogenic miRNA or a tumor suppressive miRNA. However, the role of miR-504 in HCC remains unknown. In this study, we aimed to detect the expression pattern of miR-504 in HCC tissues and cell lines and investigate the precise biological function in HCC cells. Our results showed that miR-504 expression levels were frequently downregulated in both HCC tissues and cell lines. Gain-of-function experiments demonstrated that miR-504 overexpression inhibited the proliferation and invasion in HCC cell lines. By contrast, miR-504 inhibition had the opposite effect. Interestingly, bioinformatics analysis predicted that Frizzled-7 (FZD7) was a potential target gene of miR-504. Dual-luciferase reporter assays confirmed that miR-504 directly targeted the 3'-untranslated region of FZD7 mRNA. In addition, our results showed that miR-504 negatively regulated the mRNA and protein expression of FZD7 in HCC cell lines. Moreover, miR-540 overexpression inhibited the cellular expression of β-catenin and blocked the activation of Wnt signaling in HCC cells. Notably, restoration of FZD7 expression significantly reversed the inhibitory effect of miR-504 on proliferation, invasion, and Wnt/β-catenin signaling in HCC cells. In conclusion, our results demonstrate that miR-504 functions as a tumor suppressive miRNA that inhibits the proliferation and invasion of HCC cells by targeting FZD7 and inhibiting Wnt/β-catenin signaling. Our study provides evidence that miR-504-meidated FZD7/Wnt/β-catenin signaling pathway plays an important role in HCC development and progression and suggests miR-504 as a novel future therapeutic target for treatment of HCC.

hsa_circ_0000177-miR-638-FZD7-Wnt Signaling Cascade Contributes to the Malignant Behaviors in Glioma

As a new member of the noncoding RNA family, circular RNAs (circRNAs) have been demonstrated as critical regulators in various physiological and pathological processes, such as tumorigenesis. However, the role of circRNAs has not been well understood until now. In our study, we found that circRNA hsa_circ_0000177 was upregulated in glioma tissues and cell lines. Also, hsa_circ_0000177 overexpression was associated with poor prognosis in glioma patients. Through functional experiments, we found that hsa_circ_0000177 knockdown dramatically inhibited glioma cell proliferation and invasion in vitro. Consistently, hsa_circ_0000177 knockdown significantly repressed glioma growth in vivo. In terms of mechanism, we used bioinformatics analysis and identified hsa_circ_0000177 as a miR-638 sponge. We showed that miR-638 inhibition could restore the proliferation and invasion of glioma cells transfected with hsa_circ_0000177 small interfering RNA. Furthermore, we demonstrated that frizzled class receptor 7 (FZD7) was targeted by miR-638 and upregulated by hsa_circ_0000177. Through upregulating FZD7 expression, hsa_circ_0000177 activated Wnt signaling and facilitated glioma growth. Taken together, our study revealed a novel signaling pathway involved in glioma progression.

Frizzled Receptors as Potential Therapeutic Targets in Human Cancers

Frizzled receptors (FZDs) are a family of seven-span transmembrane receptors with hallmarks of G protein-coupled receptors (GPCRs) that serve as receptors for secreted Wingless-type (WNT) ligands in the WNT signaling pathway. Functionally, FZDs play crucial roles in regulating cell polarity, embryonic development, cell proliferation, formation of neural synapses, and many other processes in developing and adult organisms. In this review, we will introduce the basic structural features and review the biological function and mechanism of FZDs in the progression of human cancers, followed by an analysis of clinical relevance and therapeutic potential of FZDs. We will focus on the development of antibody-based and small molecule inhibitor-based therapeutic strategies by targeting FZDs for human cancers.

Determination of the relationship between doxorubicin resistance and Wnt signaling pathway in HeLa and K562 cell lines

Activation of the Wnt signaling in some types of cancer and its relation with chemotherapy resistance is a very interesting issue that has been emphasized in recent years. Although, it is known that increase in the activity of β-catenin is important in blast transformation and drug resistance, the underlying mechanisms are still unclear. In this study, changes in the expression levels of 186 genes that are thought to be important in drug resistance and Wnt signaling pathways were determined by using qPCR method in doxorubicin-sensitive and -resistant HeLa and K562 cell lines. It has been observed that the genes involved in the Wnt signaling pathways are involved in more changes in HeLa/Dox cells (36 genes) than in the K562/Dox cells (17 genes). Genes important for the development of cancer resistance have been found to be significantly different in expression levels of 18 genes in HeLa/Dox cells and 20 genes in K562/Dox cells. In both cell lines, the expression of ABCB1 gene was significantly increased to 160 and 103 fold, respectively. However, despite the resistance to same drug in HeLa and K562 cell lines, it appears that the expression levels of different oncogenes and genes involved in Wnt signaling pathways have been altered. It has been found that although resistance develops to the same drug in both cell lines, the expression levels of different genes have changed. If functional analysis of these genes is performed on patient population groups, these molecules may become candidates for novel therapeutic target molecules.

Reversal effect of quercetin on multidrug resistance via FZD7/β-catenin pathway in hepatocellular carcinoma cells

BACKGROUND

Chemotherapy has been widely used to treat cancer, but the appearance of multidrug resistance (MDR) is the biggest obstacle to successful chemotherapy. One of the conventional mechanisms of MDR is overexpression of ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp/ABCB1) and multidrug resistance-associated proteins (MRPs/ABCCs) that limits the prolonged and efficient use of chemotherapeutic drugs. To enhance the chemosensitivity of tumor cells, attentions have been focused on effective MDR modulators.

PURPOSE

This study aimed to investigate the reversal effect of quercetin on MDR, and explored its mechanism of action in vitro.

STUDY DESIGN/METHODS

The effect and mechanism of quercetin on MDR was examined by using MTT assay, flow cytometry, real-time PCR and western blot analysis in human hepatocellular carcinoma cells.

RESULTS

Our data found that the intracellular accumulation of rhodamine-123 (Rh123) and doxorubicin (ADR) were increased, the sensitivity of BEL/5-FU cells to chemotherapeutic drugs were increased, and the expressions of ABCB1, ABCC1 and ABCC2 were all down-regulated, which indicated that the functions and expressions of ABCB1, ABCC1 and ABCC2 efflux pump were inhibited by quercetin treatment. Moreover, the suppression of ABCB1, ABCC1 and ABCC2 by quercetin was dependent on the FZD7 through the Wnt/β-catenin pathway. Further research revealed that reduction of FZD7 by RNA interference (siFZD7) enhanced the sensitivity to chemotherapeutic drugs, increased the cellular accumulation of Rh123 and ADR, and induced inhibitory effects on the expression of FZD7, ABCB1, ABCC1, ABCC2 and β-catenin, similar to quercetin. In the meanwhile, overexpression of FZD7 showed the inversely effect on the expressions. Interesting, it was confirmed that quercetin could inhibit the expression levels of FZD7, ABCB1, ABCC1, ABCC2 and β-catenin in BEL-7402 cells; furthermore, treatment by quercetin combined with siFZD7 in BEL/5-FU cells, the expressions of these genes were effectively decreased in comparison to quercetin combined with siRNA negative control (sncRNA).

CONCLUSION

Overall, these data suggested the effectiveness of using quercetin, at least in part, via inhibiting FZD7 to combat chemoresistance and showed that quercetin could be developed into an efficient natural sensitizer for resistant human hepatocellular carcinoma.

ABC Transporters and Their Role in the Neoadjuvant Treatment of Esophageal Cancer

The prognosis of esophageal cancer (EC) is poor, despite considerable effort of both experimental scientists and clinicians. The tri-modality treatment consisting of neoadjuvant chemoradiation followed by surgery has remained the gold standard over decades, unfortunately, without significant progress in recent years. Suitable prognostic factors indicating which patients will benefit from this tri-modality treatment are missing. Some patients rapidly progress on the neoadjuvant chemoradiotherapy, which is thus useless and sometimes even harmful. At the same time, other patients achieve complete remission on neoadjuvant chemoradiotherapy and subsequent surgery may increase their risk of morbidity and mortality. The prognosis of patients ranges from excellent to extremely poor. Considering these differences, the role of drug metabolizing enzymes and transporters, among other factors, in the EC response to chemotherapy may be more important compared, for example, with pancreatic cancer where all patients progress on chemotherapy regardless of the treatment or disease stage. This review surveys published literature describing the potential role of ATP-binding cassette transporters, the genetic polymorphisms, epigenetic regulations, and phenotypic changes in the prognosis and therapy of EC. The review provides knowledge base for further research of potential predictive biomarkers that will allow the stratification of patients into defined groups for optimal therapeutic outcome.

SOX8 regulates cancer stem-like properties and cisplatin-induced EMT in tongue squamous cell carcinoma by acting on the Wnt/β-catenin pathway

A sub-population of chemoresistant cells exhibits biological properties similar to cancer stem cells (CSCs), and these cells are believed to be a main cause for tumor relapse and metastasis. In our study, we explored the role of SOX8 and its molecular mechanism in the regulation of the stemness properties and the epithelial mesenchymal transition (EMT) of cisplatin-resistant tongue squamous cell carcinoma (TSCC) cells. We found that SOX8 was upregulated in cisplatin-resistant TSCC cells, which displayed CSC-like properties and exhibited EMT. SOX8 was also overexpressed in chemoresistant patients with TSCC and was associated with higher lymph node metastasis, advanced tumor stage and shorter overall survival. Stable knockdown of SOX8 in cisplatin-resistant TSCC cells inhibited chemoresistance, tumorsphere formation, and EMT. The Wnt/β-catenin pathway mediated the cancer stem-like properties in cisplatin-resistant TSCC cells. Further studies showed that the transfection of active β-catenin in SOX8 stable-knockdown cells partly rescued the SOX8 silencing-induced repression of stem-like features and chemoresistance. Through chromatin immunoprecipitation and luciferase assays, we observed that SOX8 bound to the promoter region of Frizzled-7 (FZD7) and induced the FZD7-mediated activation of the Wnt/β-catenin pathway. In summary, SOX8 confers chemoresistance and stemness properties and mediates EMT processes in chemoresistant TSCC via the FZD7-mediated Wnt/β-catenin pathway.