Efficacy of Wnt-1 monoclonal antibody in sarcoma cells

Drug discovery efforts toward inhibitors of canonical Wnt/β-catenin signaling pathway in the treatment of cancer: A composition-of-matter review (2010-2020)

The Wnt/β-catenin pathway has a crucial role in the proliferation and differentiation of normal cells as well as the self-renewal and pluripotency of stem cells, including cancer stem cells (CSCs). Targeting this pathway with small-molecule chemotherapeutics, discovered via conventional efforts, has proved difficult. Recently, computer-aided drug discovery efforts have produced promising chemotherapeutics. A concerted effort to develop inhibitors of this pathway through more efficient and cost-effective drug discovery methods could lead to a significant increase in clinically relevant therapeutics. Herein, patents from 2010 to 2020 are reviewed to identify those that have disclosed composition of matter for small-molecule inhibitors of the Wnt/ β-catenin pathway for cancer. We believe that such efforts will provide insights for future therapeutic candidate discovery and development in this field.

WNT/β-Catenin Pathway in Soft Tissue Sarcomas: New Therapeutic Opportunities?

Simple Summary

The WNT/β-catenin signaling pathway is involved in fundamental processes for the proliferation and differentiation of mesenchymal stem cells. However, little is known about its relevance for mesenchymal neoplasms, such us soft tissue sarcomas (STS). Chemotherapy based on doxorubicin (DXR) still remains the standard first-line treatment for locally advanced unresectable or metastatic STS, although overall survival could not be improved by combination with other chemotherapeutics. In this sense, the development of new therapeutic approaches continues to be an unmatched goal. This review covers the most important molecular alterations of the WNT signaling pathway in STS, broadening the current knowledge about STS as well as identifying novel drug targets. Furthermore, the current therapeutic options and drug candidates to modulate WNT signaling, which are usually classified by their interaction site upstream or downstream of β-catenin, and their presumable clinical impact on STS are discussed.

Abstract

Soft tissue sarcomas (STS) are a very heterogeneous group of rare tumors, comprising more than 50 different histological subtypes that originate from mesenchymal tissue. Despite their heterogeneity, chemotherapy based on doxorubicin (DXR) has been in use for forty years now and remains the standard first-line treatment for locally advanced unresectable or metastatic STS, although overall survival could not be improved by combination with other chemotherapeutics. In this sense, the development of new therapeutic approaches continues to be a largely unmatched goal. The WNT/β-catenin signaling pathway is involved in various fundamental processes for embryogenic development, including the proliferation and differentiation of mesenchymal stem cells. Although the role of this pathway has been widely researched in neoplasms of epithelial origin, little is known about its relevance for mesenchymal neoplasms. This review covers the most important molecular alterations of the WNT signaling pathway in STS. The detection of these alterations and the understanding of their functional consequences for those pathways controlling sarcomagenesis development and progression are crucial to broaden the current knowledge about STS as well as to identify novel drug targets. In this regard, the current therapeutic options and drug candidates to modulate WNT signaling, which are usually classified by their interaction site upstream or downstream of β-catenin, and their presumable clinical impact on STS are also discussed.

The Small Molecule BC-2059 Inhibits Wingless/Integrated (Wnt)-Dependent Gene Transcription in Cancer through Disruption of the Transducin β-Like 1-β-Catenin Protein Complex

The central role of β-catenin in the Wnt pathway makes it an attractive therapeutic target for cancers driven by aberrant Wnt signaling. We recently developed a small-molecule inhibitor, BC-2059, that promotes apoptosis by disrupting the β-catenin/transducin β-like 1 (TBL1) complex through an unknown mechanism of action. In this study, we show that BC-2059 directly interacts with high affinity for TBL1 when in complex with β-catenin. We identified two amino acids in a hydrophobic pocket of TBL1 that are required for binding with β-catenin, and computational modeling predicted that BC-2059 interacts at the same hydrophobic pocket. Although this pocket in TBL1 is involved in binding with NCoR/SMRT complex members G Protein Pathway Suppressor 2 (GSP2) and SMRT and p65 NFκB subunit, BC-2059 failed to disrupt the interaction of TBL1 with either NCoR/SMRT or NFκB. Together, our results show that BC-2059 selectively targets TBL1/β-catenin protein complex, suggesting BC-2059 as a therapeutic for tumors with deregulated Wnt signaling pathway. SIGNIFICANCE STATEMENT: This study reports the mechanism of action of a novel Wnt pathway inhibitor, characterizing the selective disruption of the transducin β-like 1/β-catenin protein complex. As Wnt signaling is dysregulated across cancer types, this study suggests BC-2059 has the potential to benefit patients with tumors reliant on this pathway.

Targeting the crosstalk between canonical Wnt/β-catenin and inflammatory signaling cascades: A novel strategy for cancer prevention and therapy

Emerging scientific evidence indicates that inflammation is a critical component of tumor promotion and progression. Most cancers originate from sites of chronic irritation, infections and inflammation, underscoring that the tumor microenvironment is largely orchestrated by inflammatory cells and pro-inflammatory molecules. These inflammatory components are intimately involved in neoplastic processes which foster proliferation, survival, invasion, and migration, making inflammation the primary target for cancer prevention and treatment. The influence of inflammation and the immune system on the progression and development of cancer has recently gained immense interest. The Wnt/β-catenin signaling pathway, an evolutionarily conserved signaling strategy, has a critical role in regulating tissue development. It has been implicated as a major player in cancer development and progression with its regulatory role on inflammatory cascades. Many naturally-occurring and small synthetic molecules endowed with inherent anti-inflammatory properties inhibit this aberrant signaling pathway, making them a promising class of compounds in the fight against inflammatory cancers. This article analyzes available scientific evidence and suggests a crosslink between Wnt/β-catenin signaling and inflammatory pathways in inflammatory cancers, especially breast, gastrointestinal, endometrial, and ovarian cancer. We also highlight emerging experimental findings that numerous anti-inflammatory synthetic and natural compounds target the crosslink between Wnt/β-catenin pathway and inflammatory cascades to achieve cancer prevention and intervention. Current challenges, limitations, and future directions of research are also discussed.

Activation of WNT7b autocrine eases metastasis of colorectal cancer via epithelial to mesenchymal transition and predicts poor prognosis

BACKGROUND

Aberrant activation of the Wnt/β-catenin signaling pathway is one of the most frequent abnormalities in human cancer, including colorectal cancer (CRC). Previous studies revealed pivotal functions of WNT family members in colorectal cancer, as well as their prognostic values. Nevertheless, the prognostic role and mechanisms underlying WNT7b in colorectal cancer development remains unclear.

METHODS

In this study, WNT7b expression was measured by immunohistochemical staining of 100 cases of surgically resected human colorectal cancerous tissues as well as matched adjacent normal tissues constructed as tissue microarrays. In vitro studies, we attempted to substantiate the WNT7b expressional pattern previously found in immunohistochemistry staining. We used the colorectal cancer cell-line HCT116 and normal colorectal cell-line FHC for immunofluorescence staining and nuclear/cytoplasmic separated western blotting. We measured epithelial-mesenchymal transition (EMT) markers and migration capacity of HCT116 in the context of WNT7b knocked-down using short interfering RNA. Finally, clinical and prognostic values of WNT7b activation levels were examined.

RESULTS

WNT7b was expressed in the nucleus in adjacent normal tissues. In CRC tissues, nuclear expression of WNT7b was similar; however, membrane and cytoplasmic expression was strikingly enhanced. Consistently, in vitro analysis confirmed the same expression pattern of WNT7b. Compared with FHC cells, HCT116 cells displayed higher levels of WNT7b membrane and cytoplasmic enrichment, as well as higher migration capacity with a sensitized EMT process. Either partial knockdown of WNT7b or blockade of the Wnt/β-catenin signaling pathway reversed EMT process and inhibited the migration of HCT116 cells. Finally, elevated secretion levels of WNT7b were significantly associated with lymphatic and remote metastasis and predicted worse prognosis in the CRC cohort.

CONCLUSION

In summary, we demonstrated that the activation of WNT7b autocrine probably contributes to CRC metastasis by triggering EMT process through the Wnt/β-catenin signaling pathway. High levels of WNT7b autocrine secretion predicts poor outcome in patients with CRC. This molecule is a promising candidate for clinical CRC treatments.

Wnt Pathway: An Integral Hub for Developmental and Oncogenic Signaling Networks

The Wnt pathway is an integral cell-to-cell signaling hub which regulates crucial development processes and maintenance of tissue homeostasis by coordinating cell proliferation, differentiation, cell polarity, cell movement, and stem cell renewal. When dysregulated, it is associated with various developmental diseases, fibrosis, and tumorigenesis. We now better appreciate the complexity and crosstalk of the Wnt pathway with other signaling cascades. Emerging roles of the Wnt signaling in the cancer stem cell niche and drug resistance have led to development of therapeutics specifically targeting various Wnt components, with some agents currently in clinical trials. This review highlights historical and recent findings on key mediators of Wnt signaling and how they impact antitumor immunity and maintenance of cancer stem cells. This review also examines current therapeutics being developed that modulate Wnt signaling in cancer and discusses potential shortcomings associated with available therapeutics.

Wnt/β-Catenin Signaling in Liver Cancers

Liver cancer is among the leading global healthcare issues associated with high morbidity and mortality. Liver cancer consists of hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), hepatoblastoma (HB), and several other rare tumors. Progression has been witnessed in understanding the interactions between etiological as well as environmental factors and the host in the development of liver cancers. However, the pathogenesis remains poorly understood, hampering the design of rational strategies aiding in preventing liver cancers. Accumulating evidence demonstrates that aberrant activation of the Wnt/β-catenin signaling pathway plays an important role in the initiation and progression of HCC, CCA, and HB. Targeting Wnt/β-catenin signaling potentiates a novel avenue for liver cancer treatment, which may benefit from the development of numerous small-molecule inhibitors and biologic agents in this field. In this review, we discuss the interaction between various etiological factors and components of Wnt/β-catenin signaling early in the precancerous lesion and the acquired mechanisms to further enhance Wnt/β-catenin signaling to promote robust cancer formation at later stages. Additionally, we shed light on current relevant inhibitors tested in liver cancers and provide future perspectives for preclinical and clinical liver cancer studies.

Targeting the Wnt/beta-catenin pathway in cancer: Update on effectors and inhibitors

The Wnt/beta-catenin pathway is a family of proteins that is implicated in many vital cellular functions such as stem cell regeneration and organogenesis. Several intra-cellular signal transduction pathways are induced by Wnt, notably the Wnt/beta-catenin dependent pathway or canonical pathway and the non-canonical or beta-catenin-independent pathway; the latter includes the Wnt/Ca2+ and Planar Cell Polarity pathway (PCP). Wnt activation occurs at the intestinal crypt floor, and is critical to optimal maintenance of stem cells. Colorectal cancers show evidence of Wnt signaling pathway activation and this is associated with loss of function of the tumor regulator APC. Wnt activation has been observed in breast, lung, and hematopoietic malignancies and contributes to tumor recurrence. The Wnt pathway cross talks with the Notch and Sonic Hedgehog pathways, which has implications for therapeutic interventions in cancers. There are significant challenges in targeting the Wnt pathway, including finding agents that are efficacious without damaging the system of normal somatic stem cell function in cellular repair and tissue homeostasis. Here, we comprehensively review the Wnt pathway and its interactions with the Notch and Sonic Hedgehog pathways. We present the state of the field in effectors and inhibitors of Wnt signaling, including updates on clinical trials in various cancers with inhibitors of Wnt, Notch, and Sonic Hedgehog.

Lung cells support osteosarcoma cell migration and survival

Background

Osteosarcoma (OS) is the most common primary bone tumor, with a propensity to metastasize to the lungs. Five-year survival for metastatic OS is below 30%, and has not improved for several decades despite the introduction of multi-agent chemotherapy. Understanding OS cell migration to the lungs requires an evaluation of the lung microenvironment. Here we utilized an in vitro lung cell and OS cell co-culture model to explore the interactions between OS and lung cells, hypothesizing that lung cells would promote OS cell migration and survival. The impact of a novel anti-OS chemotherapy on OS migration and survival in the lung microenvironment was also examined.

Methods

Three human OS cell lines (SJSA-1, Saos-2, U-2) and two human lung cell lines (HULEC-5a, MRC-5) were cultured according to American Type Culture Collection recommendations. Human lung cell lines were cultured in growth medium for 72 h to create conditioned media. OS proliferation was evaluated in lung co-culture and conditioned media microenvironment, with a murine fibroblast cell line (NIH-3 T3) in fresh growth medium as controls. Migration and invasion were measured using a real-time cell analysis system. Real-time PCR was utilized to probe for Aldehyde Dehydrogenase (ALDH1) expression. Osteosarcoma cells were also transduced with a lentivirus encoding for GFP to permit morphologic analysis with fluorescence microscopy. The anti-OS efficacy of Disulfiram, an ALDH-inhibitor previously shown to inhibit OS cell proliferation and metastasis in vitro, was evaluated in each microenvironment.

Results

Lung-cell conditioned medium promoted osteosarcoma cell migration, with a significantly higher attractive effect on all three osteosarcoma cell lines compared to basic growth medium, 10% serum containing medium, and NIH-3 T3 conditioned medium (p <0.05). Lung cell conditioned medium induced cell morphologic changes, as demonstrated with GFP-labeled cells. OS cells cultured in lung cell conditioned medium had increased alkaline phosphatase staining.

Conclusions

Lung endothelial HULEC-5a cells are attractants for OS cell migration, proliferation, and survival. The SJSA-1 osteosarcoma cell line demonstrated greater metastatic potential than Saos-2 and U-2 cells. ALDH appears to be involved in the interaction between lung and OS cells, and ALP may be a valuable biomarker for monitoring functional OS changes during metastasis.

Clinical Observations and Molecular Variables of Primary Vascular Leiomyosarcoma

IMPORTANCE

Vascular leiomyosarcomas are a rare subtype of leiomyosarcomas that most commonly affect the inferior vena cava and account for 5% of all leiomyosarcomas. These tumors are aggressive malignant tumors for which adjuvant modalities have not shown increased efficacy compared with surgery.

OBJECTIVES

To evaluate the outcomes of patients with vascular leiomyosarcoma and the association between vascular leiomyosarcomas and immunohistochemical molecular markers, to determine their potential prognostic and therapeutic utility.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective medical record review of a cohort of 77 patients who presented to the University of Texas MD Anderson Cancer Center in Houston during the period from January 1993 to April 2012. Data were analyzed during the period from November 2012 to May 2015. All of the patients received a confirmed diagnosis of vascular leiomyosarcoma. Immunohistochemical studies for biomarkers were performed on a tissue microarray that included 26 primary specimens of vascular leiomyosarcoma.

MAIN OUTCOMES AND MEASURES

Demographic and clinical factors were evaluated to assess clinical course, patterns of recurrence, and survival outcomes for patients with primary vascular leiomyosarcoma. A univariate Cox proportional hazards model was used to correlate disease-specific survival and time to recurrence with potential prognostic indicators.

RESULTS

Sixty-three patients with localized disease who underwent surgical resection formed the study population, and their data were used for subsequent outcomes analysis. The median age at diagnosis was 58 years (range, 22-78 years). The majority of patients were female (41 patients [65%]) and white (51 patients [81%]). The 5-year disease-specific survival rate after tumor resection was 65%. The median time to local recurrence was 43 months, the median time to distant recurrence was 25 months, and the median time to concurrent local and distant recurrences was 15 months (P = .04). Strong expressions of cytoplasmic β-catenin (hazard ratio, 5.33 [95% CI, 0.97-29.30]; P = .06) and insulinlike growth factor 1 receptor (hazard ratio, 2.74 [95% CI, 1.14-6.56]; P = .02) were associated with inferior disease-specific survival.

CONCLUSIONS AND RELEVANCE

Vascular leiomyosarcomas are aggressive malignant tumors, with high recurrence rates. Expressions of β-catenin and insulinlike growth factor 1 receptor were associated with poor disease-specific survival. Prospective studies should evaluate the clinical and therapeutic utility of these molecular markers.

The evolving roles of canonical WNT signaling in stem cells and tumorigenesis: implications in targeted cancer therapies

The canonical WNT/β-catenin signaling pathway governs a myriad of biological processes underlying the development and maintenance of adult tissue homeostasis, including regulation of stem cell self-renewal, cell proliferation, differentiation, and apoptosis. WNTs are secreted lipid-modified glycoproteins that act as short-range ligands to activate receptor-mediated signaling pathways. The hallmark of the canonical pathway is the activation of β-catenin-mediated transcriptional activity. Canonical WNTs control the β-catenin dynamics as the cytoplasmic level of β-catenin is tightly regulated via phosphorylation by the 'destruction complex', consisting of glycogen synthase kinase 3β (GSK3β), casein kinase 1α (CK1α), the scaffold protein AXIN, and the tumor suppressor adenomatous polyposis coli (APC). Aberrant regulation of this signaling cascade is associated with varieties of human diseases, especially cancers. Over the past decade, significant progress has been made in understanding the mechanisms of canonical WNT signaling. In this review, we focus on the current understanding of WNT signaling at the extracellular, cytoplasmic membrane, and intracellular/nuclear levels, including the emerging knowledge of cross-talk with other pathways. Recent progresses in developing novel WNT pathway-targeted therapies will also be reviewed. Thus, this review is intended to serve as a refresher of the current understanding about the physiologic and pathogenic roles of WNT/β-catenin signaling pathway, and to outline potential therapeutic opportunities by targeting the canonical WNT pathway.

Wnt/β-catenin signaling in bone marrow niche

The bone marrow (BM) niche is a specific physiological environment for hematopoietic and non-hematopoietic stem cells (HSCs). Several signaling pathways (including Wnt/β-catenin) regulate various aspects of stem cell growth, function and death in the BM niche. In addition, the canonical Wnt pathway is crucial for directing self-renewal and differentiation as important mechanisms in many types of stem cells. We review the role of the Wnt/β-catenin pathway in the BM niche and its importance in stem cells. Relevant literature was identified by a PubMed search (1997-2014) of English-language literature by using the following keywords: BM niche, Wnt/β-catenin signaling, osteoblast, osteoclast and bone disease. The Wnt/β-catenin pathway regulates the stability of the β-catenin proto-oncogene. The stabilized β-catenin then translocates to the nucleus, forming a β-catenin-TCF/LEF complex regulating the transcription of specific target genes. Stem cells require β-catenin to mediate their response to Wnt signaling for maintenance and transition from the pluripotent state during embryogenesis. In adult stem cells, Wnt signaling functions at various hierarchical levels to contribute to the specification of the diverse tissues. Aberrant Wnt/β-catenin signaling and its downstream transcriptional regulators are observed in several malignant stem cells and human cancers. Because Wnt signaling can maintain stem cells and cancer cells, the ability to modulate the Wnt pathway either positively or negatively may be of therapeutic relevance. The controlled activation of Wnt signaling might allow us to enhance stem and progenitor cell activity when regeneration is needed.

Targeting Wnt signaling in colorectal cancer. A Review in the Theme: Cell Signaling: Proteins, Pathways and Mechanisms

The evolutionarily conserved Wnt signaling pathway plays essential roles during embryonic development and tissue homeostasis. Notably, comprehensive genetic studies in Drosophila and mice in the past decades have demonstrated the crucial role of Wnt signaling in intestinal stem cell maintenance by regulating proliferation, differentiation, and cell-fate decisions. Wnt signaling has also been implicated in a variety of cancers and other diseases. Loss of the Wnt pathway negative regulator adenomatous polyposis coli (APC) is the hallmark of human colorectal cancers (CRC). Recent advances in high-throughput sequencing further reveal many novel recurrent Wnt pathway mutations in addition to the well-characterized APC and β-catenin mutations in CRC. Despite attractive strategies to develop drugs for Wnt signaling, major hurdles in therapeutic intervention of the pathway persist. Here we discuss the Wnt-activating mechanisms in CRC and review the current advances and challenges in drug discovery.

Genomic instability of osteosarcoma cell lines in culture: impact on the prediction of metastasis relevant genes

Background

Osteosarcoma is a rare but highly malignant cancer of the bone. As a consequence, the number of established cell lines used for experimental in vitro and in vivo osteosarcoma research is limited and the value of these cell lines relies on their stability during culture. Here we investigated the stability in gene expression by microarray analysis and array genomic hybridization of three low metastatic cell lines and derivatives thereof with increased metastatic potential using cells of different passages.

Principal Findings

The osteosarcoma cell lines showed altered gene expression during in vitro culture, and it was more pronounced in two metastatic cell lines compared to the respective parental cells. Chromosomal instability contributed in part to the altered gene expression in SAOS and LM5 cells with low and high metastatic potential. To identify metastasis-relevant genes in a background of passage-dependent altered gene expression, genes involved in "Pathways in cancer" that were consistently regulated under all passage comparisons were evaluated. Genes belonging to "Hedgehog signaling pathway" and "Wnt signaling pathway" were significantly up-regulated, and IHH, WNT10B and TCF7 were found up-regulated in all three metastatic compared to the parental cell lines.

Conclusions

Considerable instability during culture in terms of gene expression and chromosomal aberrations was observed in osteosarcoma cell lines. The use of cells from different passages and a search for genes consistently regulated in early and late passages allows the analysis of metastasis-relevant genes despite the observed instability in gene expression in osteosarcoma cell lines during culture.

Suppression of wingless-type MMTV integration site family, member 1 expression by small interfering RNA inhibits U251 glioma cell growth in vitro

A Wingless-type MMTV integration site family, member 1 (Wnt-1) RNA interference expression vector was constructed during the present study, which was used to transfect the glioma U251 cell line and investigate its effect on glioma. Two 21-base oligonucleotides complementary to the coding sequence that was flanking the loop sequence were designed to form a DNA hairpin template for the target small interfering RNA (siRNA). The siRNA templates were cloned into the siRNA expression vector, pGPU6/green fluorescent protein (GFP)/Neo and the sequence was confirmed by DNA sequencing. The pGPU6/GFP/Neo-short hairpin RNA (shRNA)-Wnt-1 vector was subsequently transfected into U251 cells, and reverse transcription polymerase chain reaction and western blot analysis were used to evaluate the Wnt-1 gene silencing effect on U251 cell growth by MTT assay and flow cytometry. The Wnt-1 protein expression was significantly reduced following transfection with the recombinant plasmid, as determined by western blot analysis of the transfected U251 cells. This transfection exhibited a significantly higher death rate, as shown by MTT. Thus, the present study demonstrated that the pGPU6/GFP/Neo-shRNA-Wnt-1 vector inhibited Wnt-1 protein expression. However, further investigations regarding the Wnt signaling pathway in glioma pathogenesis are required.

Wnt pathway in osteosarcoma, from oncogenic to therapeutic

Osteosarcoma is the most common malignant bone tumor in children and adolescents. Although pathologic characteristics of this disease are clear and well established, much remains to be understood about this tumor, particularly at the molecular signaling level. Secreted signaling molecules of the Wnt family have been widely investigated and found to play a central role in controlling embryonic bone development, bone mass, and postnatal bone regeneration. A variety of studies also suggest that Wnt signaling pathway is closely associated with bone malignancies, including breast or prostate cancer induced bone metastasis, multiple myeloma, as well as osteosarcoma. Here, we provide an overview of the role of Wnt signaling pathway in osteosarcoma development and progression, highlighting the aberrant activation of Wnt pathway in this bone malignancy. We also discuss the potential therapeutic applications for the treatment of osteosarcoma targeting Wnt pathway.

Targeting the Wnt pathway in human cancers: therapeutic targeting with a focus on OMP-54F28

The Wnt signaling pathways are a group of signal transduction pathways that play an important role in cell fate specification, cell proliferation and cell migration. Aberrant signaling in these pathways has been implicated in the development and progression of multiple cancers by allowing increased proliferation, angiogenesis, survival and metastasis. Activation of the Wnt pathway also contributes to the tumorigenicity of cancer stem cells (CSCs). Therefore, inhibiting this pathway has been a recent focus of cancer research with multiple targetable candidates in development. OMP-54F28 is a fusion protein that combines the cysteine-rich domain of frizzled family receptor 8 (Fzd8) with the immunoglobulin Fc domain that competes with the native Fzd8 receptor for its ligands and antagonizes Wnt signaling. Preclinical models with OMP-54F28 have shown reduced tumor growth and decreased CSC frequency as a single agent and in combination with other chemotherapeutic agents. Due to these findings, a phase 1a study is nearing completion with OMP-54F28 in advanced solid tumors and 3 phase 1b studies have been opened with OMP-54F28 in combination with standard-of-care chemotherapy backbones in ovarian, pancreatic and hepatocellular cancers. This article will review the Wnt signaling pathway, preclinical data on OMP-54F28 and other Wnt pathway inhibitors and ongoing clinical trials.

Wnt signaling and hepatocarcinogenesis: molecular targets for the development of innovative anticancer drugs

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer death worldwide. HCC can be cured by radical therapies if early diagnosis is done while the tumor has remained of small size. Unfortunately, diagnosis is commonly late when the tumor has grown and spread. Thus, palliative approaches are usually applied such as transarterial intrahepatic chemoembolization and sorafenib, an anti-angiogenic agent and MAP kinase inhibitor. This latter is the only targeted therapy that has shown significant, although moderate, efficiency in some individuals with advanced HCC. This highlights the need to develop other targeted therapies, and to this goal, to identify more and more pathways as potential targets. The Wnt pathway is a key component of a physiological process involved in embryonic development and tissue homeostasis. Activation of this pathway occurs when a Wnt ligand binds to a Frizzled (FZD) receptor at the cell membrane. Two different Wnt signaling cascades have been identified, called non-canonical and canonical pathways, the latter involving the β-catenin protein. Deregulation of the Wnt pathway is an early event in hepatocarcinogenesis and has been associated with an aggressive HCC phenotype, since it is implicated both in cell survival, proliferation, migration and invasion. Thus, component proteins identified in this pathway are potential candidates of pharmacological intervention. This review focuses on the characteristics and functions of the molecular targets of the Wnt signaling cascade and how they may be manipulated to achieve anti-tumor effects.

Genetic methylation and lymphoid malignancies: biomarkers of tumor progression and targeted therapy

Lymphoid malignancies, mainly including lymphocytic leukemia and lymphoma, are a group of heterogeneous diseases. Although the clinical outcome of patients has been significantly improved with current immuno-chemotherapy, definitive biomarkers remain to be investigated, particularly those reflecting the malignant behavior of tumor cells and those helpful for developing optimal targeted therapy. Recently, genome-wide analysis reveals that altered genetic methylations play an important role in tumor progression through regulation of multiple cellular transduction pathways. This review describes the pathogenetic effect of the aberrant genetic methylation in lymphoid malignancies, with special emphasis on potential therapeutic strategies targeting key signaling networks.

Novel drug discovery opportunities for colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) is a leading cause of cancer mortality worldwide, with > 1.2 million new cases and > 600,000 deaths per year. This complex disease is driven by multiple genetic lesions, commonly dysregulated signaling pathways, and aberrant activity of developmental programs such as Notch and Wnt. While emerging therapies such as EGFR inhibitors are improving treatment regimens, recent findings elucidating the role of cancer stem cells provide insights into opportunities for novel therapeutic intervention.

AREAS COVERED

This review provides a background on CRC statistics, colon anatomy and CRC pathobiology, CRC genetics and current and emerging therapies. Furthermore, the article discusses the role of developmental signaling pathways governing self-renewal biology as potential points for therapeutic intervention.

EXPERT OPINION

Despite recent advances including the introduction of targeted therapeutics, prognosis for advanced CRC patients remains bleak, reinforcing the need for novel therapeutic intervention. Developmental pathways such as Notch and Wnt provide opportunities to address this urgent need, and preclinical evidence supports targeting these pathways in CRC. Progress has been made toward this end, and while challenges persist, an increasing number of preclinical findings show promise.

WNT signalling pathways as therapeutic targets in cancer

Since the initial discovery of the oncogenic activity of WNT1 in mouse mammary glands, our appreciation for the complex roles for WNT signalling pathways in cancer has increased dramatically. WNTs and their downstream effectors regulate various processes that are important for cancer progression, including tumour initiation, tumour growth, cell senescence, cell death, differentiation and metastasis. Although WNT signalling pathways have been difficult to target, improved drug-discovery platforms and new technologies have facilitated the discovery of agents that can alter WNT signalling in preclinical models, thus setting the stage for clinical trials in humans.

Targeting Wnt pathways in disease

Wnt-mediated signal transduction pathways have long been recognized for their roles in regulating embryonic development, and have more recently been linked to cancer, neurologic diseases, inflammatory diseases, and disorders of endocrine function and bone metabolism in adults. Although therapies targeting Wnt signaling are attractive in theory, in practice it has been difficult to obtain specific therapeutics because many components of Wnt signaling pathways are also involved in other cellular processes, thereby reducing the specificity of candidate therapeutics. New technologies, and advances in understanding the mechanisms of Wnt signaling, have improved our understanding of the nuances of Wnt signaling and are leading to promising new strategies to target Wnt signaling pathways.

Targeting the Wnt/β-catenin signaling pathway in human cancers

INTRODUCTION

The Wnt/β-catenin signaling pathway plays a pivotal role in the regulation of cell growth, cell development and the differentiation of normal stem cells. Constitutive activation of the Wnt/β-catenin signaling pathway is found in many human cancers, and is thus an attractive target for anti-cancer therapy. Specific inhibitors of this pathway have been keenly researched and developed.

AREAS COVERED

This review discusses the potential of inhibiting the Wnt/β-catenin signaling pathway, as a therapeutic approach for cancer, along with an overview of the development of specific inhibitors.

EXPERT OPINION

Cancer stem cells (CSCs) play a significant role in the development and recurrence of several cancers, and Wnt/β-catenin signaling is important for the proliferation of CSCs. Inhibition of Wnt/β-catenin signaling is therefore a promising treatment approach. Progress has been made in the development of screening methods to identify Wnt/β-catenin signaling inhibitors. Biomarker-based screening is an effective and promising method for the identification of compounds of interest.

Drug discovery approaches to target Wnt signaling in cancer stem cells

Cancer stem cells (CSCs) represent a unique subset of cells within a tumor that possess self-renewal capacity and pluripotency, and can drive tumor initiation and maintenance. First identified in hematological malignancies, CSCs are now thought to play an important role in a wide variety of solid tumors such as NSCLC, breast and colorectal cancer. The role of CSCs in driving tumor formation illustrates the dysregulation of differentiation in tumorigenesis. The Wnt, Notch and Hedgehog (HH) pathways are developmental pathways that are commonly activated in many types of cancer. While substantial progress has been made in developing therapeutics targeting Notch and HH, the Wnt pathway has remained an elusive therapeutic target. This review will focus on the clinical relevance of the Wnt pathway in CSCs and tumor cell biology, as well as points of therapeutic intervention and recent advances in targeting Wnt/β-catenin signaling.

Striking the target in Wnt-y conditions: intervening in Wnt signaling during cancer progression

Wnt signaling can be divided into three pathways, namely the canonical Wnt/beta-catenin pathway, and the non-canonical (or heretical) Wnt/Ca(2+) and planar cell polarity (PCP) pathways. Although the canonical Wnt/beta-catenin pathway is the best described in cancer, increasing data points to the importance of the heretical Wnt pathways in several aspects of tumor progression. The recent advances in understanding the players and mechanisms by which these Wnt pathways contribute to cancer progression have led to the identification of numerous molecules that are already, or could be considered, targets for cancer therapy.

Sulf-2, a heparan sulfate endosulfatase, promotes human lung carcinogenesis

Heparan sulfate (HS) proteoglycans (HSPGs) bind to multiple growth factors/morphogens and regulate their signaling. 6-O-sulfation (6S) of glucosamine within HS chains is critical for many of these ligand interactions. Sulf-1 and Sulf-2, which are extracellular neutral-pH sulfatases, provide a novel post-synthetic mechanism for regulation of HSPG function by removing 6S from intact HS chains. The Sulfs can thereby modulate several signaling pathways, including the promotion of Wnt signaling. We found induction of SULF2 transcripts and Sulf-2 protein in human lung adenocarcinoma and squamous cell carcinoma, the two major classes of non-small-cell lung carcinomas (NSCLCs). We confirmed widespread Sulf-2 protein expression in tumor cells of 10/10 surgical specimens of human lung squamous carcinomas. We studied five Sulf-2(+) NSCLC cell lines, including two, which were derived by cigarette-smoke transformation of bronchial epithelial cells. shRNA-mediated Sulf-2 knockdown in these lines caused an increase in 6S on their cell surface and in parallel reversed their transformed phenotype in vitro, eliminated autocrine Wnt signaling and strongly blunted xenograft tumor formation in nude mice. Conversely, forced Sulf-2 expression in non-malignant bronchial epithelial cells produced a partially transformed phenotype. Our findings support an essential role for Sulf-2 in lung cancer, the leading cancer killer.

Exploring the pathogenesis of renal cell carcinoma: pathway and bioinformatics analysis of dysregulated genes and proteins

We recently identified a group of proteins which are dysregulated in renal cell carcinoma (RCC). In this study, we performed bioinformatics and pathway analysis of these proteins. Proteins were mapped to gene ontology biological processes. The upregulated proteins tend to cluster in processes, such as cancer initiation and progression. In addition, we identified a number of pathways that are significantly enriched in RCC. Some of these are 'common' pathways which are dysregulated in many cancers, but we also identified a number of pathways which were not previously linked to RCC. In addition to their potential prognostic values, many of these pathways have a potential as therapeutic targets for RCC. To verify our findings, we compared our proteins to a pool of datasets from published reports. Although there were only a minimal number of common proteins, there was a significant overlap between the identified pathways in the two groups. Moreover, out of 16 individually discovered genes identified by a literature search, 10 were found to be related to our dysregulated pathways. We also verified the upregulation of the mammalian target of rapamycin signaling pathway in RCC by immunohistochemistry. Finally, we highlight the potential clinical applications of pathway analysis in kidney cancer.

Frzb, a secreted Wnt antagonist, decreases growth and invasiveness of fibrosarcoma cells associated with inhibition of Met signaling

Soft tissue sarcomas (STS) have a strong propensity for aggressive growth and metastasis. We showed that the secreted Wnt antagonist Frzb exhibited potent antitumor activity against prostate cancer, an epithelial type of malignancy. In this study, we further showed the antitumor efficacy of Frzb in STS, a mesenchymal group of cancer. Frzb transfection of HT1080 (fibrosarcoma) and SW872 (liposarcoma) cell lines and their conditioned media resulted in a significant reduction in cellular invasion, motility, and colony formation in soft agar compared with vector control-transfected cells. In a xenograft mouse model, Frzb dramatically suppressed tumor growth of HT1080 cells in nude mice. In a tail-vein injection metastatic model, Frzb-transfected HT1080 cells formed fewer and smaller lung nodules than vector control cells. In addition, we identified new mechanisms for Frzb antitumor activities. Frzb reduced c-Met expression and inhibited Met-mediated signaling, associated with up-regulation of epithelial markers (i.e., keratins 8 and 18) and down-regulation of mesenchymal markers (i.e., vimentin, N-cadherin, fibronectin, Slug, and Twist). Similar to Frzb, silencing of c-Met by short hairpin RNA or using a dominant-negative LRP5 receptor also suppressed Met signaling, leading to reduced cellular motility, invasion, and in vivo tumor growth. Given recent studies indicating an important role of c-Met in sarcoma development and progression, our data showed that Frzb expression was significantly inversely correlated with Met expression in both STS cell lines and tissues. These results suggested the usefulness of Frzb in modulating Met signaling as a new treatment strategy for STS.

Autocrine WNT signaling contributes to breast cancer cell proliferation via the canonical WNT pathway and EGFR transactivation

Background

De-regulation of the wingless and integration site growth factor (WNT) signaling pathway via mutations in APC and Axin, proteins that target β-catenin for destruction, have been linked to various types of human cancer. These genetic alterations rarely, if ever, are observed in breast tumors. However, various lines of evidence suggest that WNT signaling may also be de-regulated in breast cancer. Most breast tumors show hypermethylation of the promoter region of secreted Frizzled-related protein 1 (sFRP1), a negative WNT pathway regulator, leading to downregulation of its expression. As a consequence, WNT signaling is enhanced and may contribute to proliferation of human breast tumor cells. We previously demonstrated that, in addition to the canonical WNT/β-catenin pathway, WNT signaling activates the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway in mouse mammary epithelial cells via epidermal growth factor receptor (EGFR) transactivation.

Methods

Using the WNT modulator sFRP1 and short interfering RNA-mediated Dishevelled (DVL) knockdown, we interfered with autocrine WNT signaling at the ligand-receptor level. The impact on proliferation was measured by cell counting, YOPRO, and the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay; β-catenin, EGFR, ERK1/2 activation, and PARP (poly [ADP-ribose]polymerase) cleavages were assessed by Western blotting after treatment of human breast cancer cell lines with conditioned media, purified proteins, small-molecule inhibitors, or blocking antibodies.

Results

Phospho-DVL and stabilized β-catenin are present in many breast tumor cell lines, indicating autocrine WNT signaling activity. Interfering with this loop decreases active β-catenin levels, lowers ERK1/2 activity, blocks proliferation, and induces apoptosis in MDA-MB-231, BT474, SkBr3, JIMT-1, and MCF-7 cells. The effects of WNT signaling are mediated partly by EGFR transactivation in human breast cancer cells in a metalloprotease- and Src-dependent manner. Furthermore, Wnt1 rescues estrogen receptor-positive (ER⁺) breast cancer cells from the anti-proliferative effects of 4-hydroxytamoxifen (4-HT) and this activity can be blocked by an EGFR tyrosine kinase inhibitor.

Conclusion

Our data show that interference with autocrine WNT signaling in human breast cancer reduces proliferation and survival of human breast cancer cells and rescues ER⁺ tumor cells from 4-HT by activation of the canonical WNT pathway and EGFR transactivation. These findings suggest that interference with WNT signaling at the ligand-receptor level in combination with other targeted therapies may improve the efficiency of breast cancer treatments.

Suppression of PPN/MG61 attenuates Wnt/beta-catenin signaling pathway and induces apoptosis in human lung cancer

Wingless and int homologue (Wnt) family proteins have been shown to have important roles in the decision of cell fate and behavior at multiple stages during the development and tumorigenesis. One of the Drosophila segment polarity genes, porcupine (porc) gene, encodes an evolutionarily conserved endoplasmic reticulum membrane protein involving in the post-translational processing of the Wnt family proteins. Here, we report that human homologue of Drosophila porc gene, PPN/MG61, was abundantly expressed in human cancer cell lines, but not in normal cells. We also found that PPN/MG61 was overexpressed in primary lung cancer tissue samples, compared to their matched normal tissue samples. Furthermore, when we used small interfering RNA to knock down PPN/MG61 mRNA in lung cancer cells expressing the gene, we observed apoptosis induction, along with decreased activity of Wnt pathway in those lung cancer cells. These data suggest that PPN/MG61 may be a novel marker for human lung cancer and that post-translational modification of the Wnt signal molecules by PPN/MG61 may be important for the function of Wnt pathway in lung cancer.

siRNA-mediated beta-catenin knockdown in human hepatoma cells results in decreased growth and survival

beta-Catenin, the chief oncogenic component of the canonical Wnt pathway, is known to be involved in a variety of cancers, including hepatocellular carcinoma (HCC). Although the mechanism of beta-catenin activation in HCC is multifactorial, it is indisputably implicated at various stages of hepatocarcinogenesis, making it an attractive therapeutic target. Here we investigate the effect of small interfering RNA-mediated beta-catenin knockdown on the growth and survival of human hepatoma cell lines with (HepG2) and without (Hep3B) beta-catenin mutations. Transfection of HepG2 and Hep3B cells with human beta-catenin (CTNNB1) small interfering RNA resulted in a significant beta-catenin decrease, as confirmed by Western blot analyses and immunofluorescence, also leading to decreased expression of known target genes such as cyclin D1 and glutamine synthetase. The decrease in beta-catenin activity was confirmed by TOPflash reporter luciferase assay. The functional impact of diminished beta-catenin was exhibited as temporal decrease in tumor cell viability by the MTT assay. A concomitant decrease in tumor cell proliferation was also evident with [(3)H]thymidine incorporation and verified with soft agar assays. Thus, beta-catenin is essential for the survival and growth of hepatoma cells independent of mutations in the beta-catenin gene and provide a proof of principle for the significance of the therapeutic inhibition of beta-catenin in HCC.

The hepatitis B x antigen effector, URG7, blocks tumour necrosis factor α-mediated apoptosis by activation of phosphoinositol 3-kinase and β-catenin

Hepatitis B x antigen (HBxAg) contributes significantly to the pathogenesis of chronic infection and development of hepatocellular carcinoma. To discern some of its operative pathways, HepG2 cells were stably transduced with HBx or the bacterial chloramphenicol acetyltransferase (CAT) gene. Differential gene expression has previously revealed an upregulated gene, clone 7 (URG7), that conferred resistance to anti-Fas killing on HepG2X cells. Given that tumour necrosis factor alpha (TNFα) is also an important mediator of chronic hepatitis, and partially shares signalling with Fas, experiments were designed to test whether URG7 blocks TNFα killing of HepG2X cells. HepG2X cells expressing URG7 and HepG2 cells overexpressing URG7 in the absence of HBxAg were resistant to TNFα killing compared with HepG2CAT cells. URG7 small interfering RNA restored the sensitivity of HepG2X cells to TNFα killing. Killing was associated with the activation of caspases 3 and 8, suggesting that URG7 blocked these caspases. This resistance was also associated with activation of phosphoinositol 3-kinase/Akt. Given that Akt and HBxAg also activate β-catenin, experiments were designed to determine whether URG7 blocked apoptosis via activation of β-catenin. Both HBxAg and URG7 activated fragments of the β-catenin promoter, and also promoted expression of β-catenin target genes. Hence, URG7 inhibits TNFα-mediated killing by blocking one or more caspases in the apoptotic pathway and by activating phosphoinositol 3-kinase and β-catenin, thereby overriding the apoptotic signalling of TNFα. This suggests that URG7 helps to protect virus-infected hepatocytes during chronic hepatitis B virus infection.

Syndecan-1 and Wingless-type protein-1 in human ameloblastomas

BACKGROUND

Aberrant Wingless type 1 glycoprotein (Wnt) pathway in ameloblastomas and a role of syndecan-1 (SDC1) in activating Wnt signalling were perspected. SDC1 shifting from epithelium to stroma was reported in invasive non-odontogenic neoplasms. The aim of this study was to reveal the role of SDC1 and Wnt1 in intraosseous ameloblastomas (IA(s)).

METHODS

SDC1 and Wnt1 expressions were investigated in 29 ameloblastoma subtypes and seven tooth buds.

RESULTS

SDC1 immunostaining strongly depicted stromal cells, extracellular matrix (ECM) and basement membranes of ameloblastomas. It also showed epithelial tumour cells in the acanthomatous and plexiform subtypes, and it often occurred in stellate reticulum cells and basal ameloblasts of tooth buds. Parallel Wnt1 expression occurred in ameloblastomatous epithelial cells, but it was common in basal cells of tooth buds too. Statistically, a significant correlation was found between the percentage of IA(s)-bearing SDC1-positive stromal cells and ECM and the percentage of IA(s)-bearing Wnt1-positive epithelial cells.

CONCLUSIONS

A role of SDC1 in stromal cells and ECM can be hypothesized as a critical factor for carcinogenesis and local invasiveness of IA(s).

Adult human sarcomas. II. Medical oncology

Human sarcoma cells can be killed by radio- and chemotherapy, but tumor cells acquiring resistance frequently kill the patient. A keen understanding of the intracellular course of oncogenic cascades leads to the discovery of small molecular inhibitors of the involved phosphorylated kinases. Targeted therapy complements chemotherapy. Oncogene silencing is feasible by small interfering RNA. The restoration of some of the mutated or deleted tumor-suppressor genes (p53, Rb, PTEN, hSNF, INK/ARF and WT) by demethylation or reacetylation of their histones has been accomplished. Genetically engineered or naturally oncolytic viruses selectively lyse tumors and leave healthy tissues intact. Adeno- or retroviral vectors deliver genes of immunological costimulators, tumor antigens, chemo- or cytokines and/or tumor-suppressor proteins into tumor (sarcoma) cells. Suicide gene delivery results in apoptosis induction. Genes of enzymes that target prodrugs as their substrates render tumor cells highly susceptible to chemotherapy, with the prodrug to be targeted intracellularly. It will be combinations of sophisticated surgical removal of the nonencapsulated and locally invasive primary sarcomas, advanced forms of radiotherapy to the involved sites and immunotherapy with sarcoma vaccines that will cure primary sarcomas. Adoptive immunotherapy with immune lymphocytes will be operational in metastatic disease only when populations of regulatory T cells are controlled. Targeted therapy with small molecular inhibitors of oncogene cascades, the driving forces of sarcoma cells, alteration of the tumor stroma from a supportive to a tumor-hostile environment, reactivation or replacement of wild-type tumor-suppressor genes, and radio-chemotherapy (with much reduced toxicity) will eventually accomplish the cure of metastatic sarcomas.

Targeting the Wnt signaling pathway to treat Barrett’s esophagus

Barrett's esophagus (BE) is an acquired condition in which the normal squamous epithelium in the distal esophagus is replaced by a metaplastic columnar epithelium, as a complication of chronic gastroesophageal reflux. The clinical significance of this disease is its associated predisposition to esophageal adenocarcinoma (EAC). Recently, and similarly to other human malignancies, the Wnt signaling pathway and its key component beta-catenin have been implicated in the carcinogenesis of BE. Although mutations in adenomatous polyposis coli (APC) or beta-catenin are rare in EAC, alterations of upstream components, such as overexpression of Wnt2 ligand or downregulation of Wnt antagonists may play dominant roles in the activation of the Wnt pathway. Increasing evidence suggests that inhibiting the Wnt pathway may be a new targeted therapy for the treatment of cancers and could, therefore, be promising for the cure of EAC, which remains a highly lethal disease.

WNTS and WNT receptors as therapeutic tools and targets in human disease processes

The body of scientific literature linking Wnts and Wnt-associated proteins to human disease processes continues to grow in parallel with new discoveries from basic science laboratories that further characterize the elaborate cellular events following the binding of Wnts to their receptors. While Wnt-mediated signaling has long been known to play a major role in human carcinogenesis, accumulating evidence indicates that Wnts are also important mediators of inflammation and recovery from injury. The binding of secreted Wnt ligands to their receptors offers an attractive and accessible target for therapeutic regulation of these signaling pathways. Several promising preliminary studies have already addressed potential avenues for the manipulation of Wnt signaling in disease processes. This review will focus on disease processes involving the regulation of Wnt signaling at the level of Wnt binding to its target receptors. Wnt proteins, Wnt receptors, and secreted Wnt inhibitors are attractive as potential therapeutic agents and targets due to their extracellular location. In addition, since Wnt signaling results in a diverse array of downstream intracellular events, many of which are not fully understood, the targeting of this pathway at the most upstream site of pathway activation also provides a strategic advantage for therapy. As the list of Wnt-related diseases continues to grow, advances in our understanding of the biochemical and molecular mechanisms underlying Wnt signaling may ultimately translate into innovative ways to treat Wnt-related disease processes in patients.

Wnt signaling in stem cells and lung cancer

The Wnt signal transduction pathway plays important roles during embryo development, regulating cell proliferation and survival of immature cells. However, its improper function can lead to harmful consequences for humans, such as aberrant cell proliferation and, therefore, cancer. Increasing evidence suggests that stem cells may be the source of mutant cells that cause cancers to develop and proliferate. Wnt signaling has been shown to promote self-renewal in both gut epithelial and hematopoietic stem cells (HSCs) and to trigger critical pathways in carcinogenesis. Although the function of stem cells in solid tumor development is unclear, the Wnt pathway's role in determining the fate and self-renewal potential of cancer stem cells suggests a critical role in carcinogenesis. The development of new inhibitors, such as antibodies or small molecules, to inhibit this pathway may be of great therapeutic utility against cancer.

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

BACKGROUND

Wnt/beta-catenin pathway has critical roles in development and oncogenesis. Although significant progress has been made in understanding the downstream signaling cascade of this pathway, little is known regarding Wnt/beta-catenin pathway modification of the cellular apoptosis.

METHODS

To identify potential genes regulated by Wnt/beta-catenin pathway and involved in apoptosis, we used a stably integrated, inducible RNA interference (RNAi) vector to specific inhibit the expression and the transcriptional activity of beta-catenin in HeLa cells. Meanwhile, we designed an oligonucleotide microarray covering 1384 apoptosis-related genes. Using oligonucleotide microarrays, a series of differential expression of genes was identified and further confirmed by RT-PCR.

RESULTS

Stably integrated inducible RNAi vector could effectively suppress beta-catenin expression and the transcriptional activity of beta-catenin/TCF. Meanwhile, depletion of beta-catenin in this manner made the cells more sensitive to apoptosis. 130 genes involved in some important cell-apoptotic pathways, such as PTEN-PI3K-AKT pathway, NF-kappaB pathway and p53 pathway, showed significant alteration in their expression level after the knockdown of beta-catenin.

CONCLUSION

Coupling RNAi knockdown with microarray and RT-PCR analyses proves to be a versatile strategy for identifying genes regulated by Wnt/beta-catenin pathway and for a better understanding the role of this pathway in apoptosis. Some of the identified beta-catenin/TCF directed or indirected target genes may represent excellent targets to limit tumor growth.

Dysregulation of growth factor signaling in human hepatocellular carcinoma

Dysregulation of pleiotropic growth factors, receptors and their downstream signaling pathway components represent a central protumorigenic principle in human hepatocarcinogenesis. Especially the Insulin-like Growth Factor/IGF-1 receptor (IGF/IGF-1R), Hepatocyte Growth Factor (HGF/MET), Wingless (Wnt/beta-catenin/FZD), Transforming Growth Factor alpha/Epidermal Growth Factor receptor (TGFalpha/EGFR) and Transforming Growth Factor beta (TGFbeta/TbetaR) pathways contribute to proliferation, antiapoptosis and invasive behavior of tumor cells. This review focuses on the relevant alterations in these pathways identified in human human hepatocellular carcinomas (HCCs). Resultant functional effects are modulated by multiple cross-talks between the different signaling pathways and additional tumor-relevant factors, such as cyclooxygenase-2 and p53. Several specific strategies are currently under development such as receptor kinase inhibitors, neutralizing antibodies and antagonistic proteins, which may improve the systemic treatment of human HCCs.

Wnt signaling activation and WIF-1 silencing in nasopharyngeal cancer cell lines

Aberrant activation of Wingless-type (Wnt) signaling pathway plays a critical role in oncogenesis of various human cancers. Wnt inhibitory factor-1 (WIF-1) is a secreted antagonist of Wnt signaling and acts through direct binding to Wnt in the extracellular space. Recently, we reported Wnt signaling in various human malignancies. In addition, we identified in lung cancer that WIF-1 is silenced due to promoter hypermethylation. In this study, we found constitutive activation of Wnt signaling and WIF-1 silencing in nasopharyngeal carcinoma (NPC) cell lines. Furthermore, by utilizing methylation-specific PCR and sequence analysis, we demonstrated that frequent hypermethylation of the WIF-1 promoter correlates with WIF-1 silencing in NPC cell lines. Our results indicate that aberrant Wnt signaling is a common event in NPC carcinogenesis linked with WIF-1 silencing in at least cell lines. Strategies targeting these molecules should be potentially promising in treating NPC.