Smad4-dependent TGF-beta signaling suppresses RON receptor tyrosine kinase-dependent motility and invasion of pancreatic cancer cells

Small-molecule agents for cancer immunotherapy

Cancer immunotherapy, exemplified by the remarkable clinical benefits of the immune checkpoint blockade and chimeric antigen receptor T-cell therapy, is revolutionizing cancer therapy. They induce long-term tumor regression and overall survival benefit in many types of cancer. With the advances in our knowledge about the tumor immune microenvironment, remarkable progress has been made in the development of small-molecule drugs for immunotherapy. Small molecules targeting PRR-associated pathways, immune checkpoints, oncogenic signaling, metabolic pathways, cytokine/chemokine signaling, and immune-related kinases have been extensively investigated. Monotherapy of small-molecule immunotherapeutic drugs and their combinations with other antitumor modalities are under active clinical investigations to overcome immune tolerance and circumvent immune checkpoint inhibitor resistance. Here, we review the latest development of small-molecule agents for cancer immunotherapy by targeting defined pathways and highlighting their progress in recent clinical investigations.

Molecular mechanism(s) of regulation(s) of c-MET/HGF signaling in head and neck cancer

Head and neck cancer is the sixth most common cancer across the globe. This is generally associated with tobacco and alcohol consumption. Cancer in the pharynx majorly arises through human papillomavirus (HPV) infection, thus classifying head and neck squamous cell carcinoma (HNSCC) into HPV-positive and HPV-negative HNSCCs. Aberrant, mesenchymal-epithelial transition factor (c-MET) signal transduction favors HNSCC progression by stimulating proliferation, motility, invasiveness, morphogenesis, and angiogenesis. c-MET upregulation can be found in the majority of head and neck squamous cell carcinomas. c-MET pathway acts on several downstream effectors including phospholipase C gamma (PLCγ), cellular Src kinase (c-Src), phosphotidylinsitol-3-OH kinase (PI3K), alpha serine/threonine-protein kinase (Akt), mitogen-activated protein kinase (MAPK), and wingless-related integration site (Wnt) pathways. c-MET also establishes a crosstalk pathway with epidermal growth factor receptor (EGFR) and contributes towards chemoresistance in HNSCC. In recent years, the signaling communications of c-MET/HGF in metabolic dysregulation, tumor-microenvironment and immune modulation in HNSCC have emerged. Several clinical trials have been established against c-MET/ hepatocyte growth factor (HGF) signaling network to bring up targeted and effective therapeutic strategies against HNSCC. In this review, we discuss the molecular mechanism(s) and current understanding of c-MET/HGF signaling and its effect on HNSCC.

Graphical abstract

RON Mediates Tumor-Promoting Effects in Endometrial Adenocarcinoma

Endometrial adenocarcinoma is one of the most prevalent female reproductive tract cancers in the world, and the development of effective treatment is still the main goal of its current research. Epithelial-mesenchymal transition (EMT) plays a significant part in the occurrence and development of epithelial carcinoma, including endometrial adenocarcinoma. Recepteur d'origine nantais (RON) induces EMT and promotes proliferation, migration, and invasion in various epithelial-derived cancers, but its role in endometrial adenocarcinoma is still poorly studied. The purpose of this study is to verify the overexpression of RON in endometrial adenocarcinoma and to explore its specific roles. RON expression in tumor lesions was verified by immunohistochemical staining, HEC-1B cells were used to construct stable cell lines with RON overexpression or knockdown to investigate the effects of RON on the function of endometrial adenocarcinoma cells, and xenotransplantation experiment was carried out in nude mice to explore the effect of RON on the growth of endometrial adenocarcinoma in vivo. This study revealed that RON could promote the proliferation, migration, and invasion of HEC-1B cells and induce EMT, and these effects were regulated through the Smad pathway. RON overexpression could promote growth of endometrial adenocarcinoma cells in nude mice, while its inhibitor BMS777607 could restrict this role. RON played an important role in endometrial adenocarcinoma and had a potential to become a new therapeutic target for endometrial adenocarcinoma.

Antibody drug conjugates in gastrointestinal cancer: From lab to clinical development

The antibody-drug conjugates (ADCs) are one the fastest growing biotherapeutics in oncology and are still in their infancy in gastrointestinal (GI) cancer for clinical applications to improve patient survival. The ADC based approach is developed with tumor specific antigen, antibody carrying cytotoxic agents to precisely target and deliver chemotherapeutics at the tumor site. To date, 11 ADCs have been approved by US-FDA, and more than 80 are in the clinical development phase for different oncological indications. However, The ADCs based therapies in GI cancers are still far from having high-efficient clinical outcomes. The limited success of these ADCs and lessons learned from the past are now being used to develop a newer generation of ADC against GI cancers. In this review, we did a comprehensive assessment of the key components of ADCs, including tumor marker, antibody, cytotoxic payload, and linkage strategy, with a focus on technical improvement and some future trends in the pipeline for clinical translation. The various preclinical and clinical ADCs used in gastrointestinal malignancies, their target, composition and bioconjugation, along with preclinical and clinical outcomes, are discussed. The emphasis is also given to new generation ADCs employing novel mAb, payload, linker, and bioconjugation methods are also included.

The MSP-RON pathway regulates liver fibrosis through transforming growth factor beta-dependent epithelial-mesenchymal transition

BACKGROUND

Liver fibrosis is pathologically important in the liver cirrhosis progression. The epithelial-mesenchymal transition (EMT) is crucial for organ fibrosis. Macrophage-stimulating protein (MSP) and its receptor tyrosine kinase, RON, promote cellular EMT. However, their role in liver fibrosis is unclear. Here, we clarify the biological profile, potential mechanisms and therapeutic targets of the MSP-RON pathway in liver fibrosis.

MATERIALS AND METHODS

Macrophage-stimulating protein expression and its correlation with clinicopathological characteristics of cirrhosis were evaluated in 57 clinical cases and a control group. The effect of MSP-RON pathway in liver fibrosis was determined in vitro and in vivo. The therapeutic effects of MSP or RON inhibition on liver fibrosis were evaluated in a mouse liver fibrosis model.

RESULTS

Macrophage-stimulating protein is upregulated in liver cirrhosis, which was associated with poor patient prognosis. The MSP-RON pathway promoted hepatocytes EMT. MSP-RON-induced EMT depends on the transforming growth factor beta (TGF-β) pathway and is regulated by TGF-β inhibitors. In animal models, an MSP blocking antibody and a small molecule inhibitor of RON, BMS-777607, both inhibited liver fibrosis progression.

CONCLUSION

Our study revealed that MSP is an important biomarker in liver cirrhosis progression and can be used to prognose patients. The MSP-RON pathway promotes the EMT of hepatocytes and the progress of fibrosis via a TGF-β related pathway. Consequently, we identified a new treatment strategy for liver cirrhosis through targeted inhibition of MSP/RON. This research increases the understanding of EMT-modulated liver fibrosis and provides new insights into biomarkers and therapeutic targets of liver fibrosis.

CMTM8 as an LPA1-associated partner mediates lysophosphatidic acid-induced pancreatic cancer metastasis

Background

Lysophosphatidic acid (LPA) is known to promote cancer cell invasiveness through LPA1, but the downstream signaling cascades are still not fully clarified. The CKLF-like MARVEL transmembrane domain-containing (CMTM) family regulates aggressive phenotype in many cancers.

Methods

We performed LPA1 co-immunoprecipitation combined with mass spectrometry to search for LPA1-associated proteins. The role of CMTM8 in mediating the pro-invasive activity of LPA was investigated in pancreatic cancer.

Results

We identified CMTM8 as an LPA1-interacting protein. LPA1 and CMTM8 were co-localized in pancreatic cancer cells. LPA treatment led to stabilization of CMTM8 protein, which was impaired by knockdown of LPA1. Depletion of CMTM8 significantly suppressed the migration and invasion of pancreatic cancer cells. Conversely, ectopic expression of CMTM8 enhanced the migratory and invasive capacity of pancreatic cancer cells. CMTM8 depletion blocked the formation of metastatic lesions in the lung. Knockdown of CMTM8 attenuated LPA-induced migration and invasion in pancreatic cancer cells. CMTM8 overexpression stimulated β-catenin activation through reduction of GSK3β. In addition, knockdown of β-catenin dramatically antagonized CMTM8-mediated migration and invasion in pancreatic cancer cells.

Conclusions

CMTM8 serves as a key mediator of LPA-induced invasiveness in pancreatic cancer. The interaction between CMTM8 and LPA1 leads to activation of oncogenic β-catenin signaling. CMTM8 represents a potential therapeutic target for pancreatic cancer.

RON receptor tyrosine kinase in pancreatic ductal adenocarcinoma: Pathogenic mechanism in malignancy and pharmaceutical target for therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers with poor prognosis and high mortality. Molecular aberrations associated with PDAC pathogenesis and progression have been extensively investigated. Nevertheless, these findings have not been translated into clinical practice. Lack of therapeutics for PDAC treatment is another challenge. Recent application of molecularly targeted and immunoregulatory therapies appears to be disappointing. Thus, discovery of new targets and therapeutics is urgently needed to combat this malignant disease. The RON receptor tyrosine kinase is a tumorigenic determinant in PDAC malignancy, which provides the rationale to target RON for PDAC treatment. In this review, we summarize the latest evidence of RON in PDAC pathogenesis and the development of anti-RON antibody-drug conjugates for potential PDAC therapy. The finding that anti-RON antibody-drug conjugates show efficacy in preclinical animal models highlights the potential of this novel class of anti-cancer biotherapeutics in future clinical trials.

Aberrant RON and MET Co-overexpression as Novel Prognostic Biomarkers of Shortened Patient Survival and Therapeutic Targets of Tyrosine Kinase Inhibitors in Pancreatic Cancer

RON (recepteur d'origine nantais) and MET (hepatocyte growth factor receptor) are tyrosine kinase receptors. Various cancers have aberrant RON and MET expression and activation, which contribute to cancer cell proliferation, invasiveness, and metastasis. Here, we explored RON and MET expression in pancreatic cancer and their relationship with overall survival (OS) time, and evaluated their significance as therapeutic targets of tyrosine kinase inhibitors in pancreatic cancer. We enrolled 227 patients with pancreatic cancer in the study. RON and MET expression was analyzed by immunohistochemical staining. Four human pancreatic cancer cell lines expressing variable levels of RON or MET and four MET superfamily inhibitors (BMS777607, PHA665752, INCB28060, Tivantinib) were used. The effect of the four tyrosine kinase inhibitors on cell viability, migration, and apoptosis were determined using cell viability, scratch wound healing, and Caspase-Glo 3/7 assays. Cellular signaling was analyzed by immunoprecipitation and western blotting. The therapeutic efficacy of the tyrosine kinase inhibitors was determined with mouse xenograft pancreatic cancer models in vivo. There was wide aberrant RON and MET expression in the cancer tissues. In 227 pancreatic cancer samples, 33% had RON overexpression, 41% had MET overexpression, and 15.4% had RON and MET co-overexpression. RON and MET expression were highly correlated. RON and MET expression levels were significantly related to OS. Patients with RON and MET co-overexpression had poorer OS. BMS777607 and PHA665752 inhibited pancreatic cancer cell viability and migration, and promoted apoptosis by inhibiting RON and MET phosphorylation and further inhibiting the downstream signaling pathways in vitro. They also inhibited tumor growth and further inhibited phosphorylated (phosphor)-RON and phospho-MET expression in the mouse xenograft models in vivo effectively. INCB28060, which inhibits the MET signaling pathway alone, was not effective. RON and MET can be important indicators of prognosis in pancreatic cancer. Tyrosine kinase inhibitors targeting RON and MET in pancreatic cancer are a novel and potential approach for pancreatic cancer therapy.

Therapeutic efficacy of a novel humanized antibody-drug conjugate recognizing plexin-semaphorin-integrin domain in the RON receptor for targeted cancer therapy

Background

Antibody-drug conjugates (ADCs) targeting the RON receptor, a tumorigenic factor contributing to cancer malignancy, has been considered as a novel strategy for cancer therapy. Here we describe a humanized antibody recognizing the RON plexin-semaphorin-integrin (PSI) domain with increased drug delivery capability for potential clinical application.

Method

Monoclonal antibody PCM5B14 specific to the human and monkey RON PSI domain was generated and characterized by various immunological methods. Humanized antibody H5B14 was created by grafting PCM5B14 complementarity-determining regions into human IgG1/κ acceptor frameworks and conjugated with monomethyl auristatin E and duocarmycin to form two H5B14-based ADCs. Stability of H5B14-based ADCs in human plasma was measured using hydrophobic interaction chromatography. Various biochemical and biological assays were used to determine ADC- regulated RON internalization, cell viability, spheroid formation, and death of cancer stem-like cells. Efficacies of H5B14-based ADCs in vivo were validated using tumor xenograft models. Maximal tolerated doses of H5B14-based ADCs were established in mice.

Results

H5B14 was highly specific to the human RON PSI domain and superior over other anti-RON ADCs in induction of RON internalization in various cancer cell lines tested. H5B14-based ADCS had a drug to antibody ratio of ~ 3.70:1 and were stable in human plasma with a minimal dissociation within a 10-day period. Functionally, H5B14-mediated drug delivery decreased cell viability at early stages with an average IC₅₀ at ~ 20 nM in multiple cancer cell lines examined. H5B14-based ADCs also inhibited spheroid formation and caused death of cancer stem-like cells with RON⁺/CD44⁺/ESA⁺ phenotypes. In vivo, H5B14-based ADCs in a single injection inhibited tumor xenograft growth mediated by multiple cancer cell lines. Tumoristatic concentrations calculated from xenograft tumor models were in the range of 0.63 to 2.0 mg/kg bodyweight. Significantly, H5B14-based ADCs were capable of eradicating tumors at variable levels across multiple xenograft models regardless their malignant statuses. Toxicologically, H5B14-based ADCs were well tolerated in mice up to 60 mg/kg.

Conclusion

H5B14-based ADCs targeting the RON PSI domain are superior in inducing RON internalization, leading to robust drug delivery and overall inhibition and eradication of tumors in multiple xenograft models. These findings warrant H5B14-based ADCs for clinical trials in the future.

Therapeutic efficacy, pharmacokinetic profiles, and toxicological activities of humanized antibody-drug conjugate Zt/g4-MMAE targeting RON receptor tyrosine kinase for cancer therapy

BACKGROUND

Aberrant expression of the RON receptor tyrosine kinase is a pathogenic feature and a validated drug target in various types of cancers. Currently, therapeutic antibodies targeting RON for cancer therapy are under intensive evaluation. Here we report the development and validation of a novel humanized anti-RON antibody-drug conjugate for cancer therapy.

METHODS

Antibody humanization was achieved by grafting sequences of complementarity-determining regions from mouse monoclonal antibody Zt/g4 into human IgG1/κ acceptor frameworks. The selected humanized Zt/g4 subclone H1L3 was conjugated with monomethyl auristatin E using a dipeptide linker to form H-Zt/g4-MMAE. Pharmacokinetic analysis of H-Zt/g4-MMAE was determined using hydrophobic interaction chromatography and a MMAE ADC ELISA kit. Biochemical and biological assays were used for measuring RON expression, internalization, cell viability and death. Therapeutic efficacies of H-Zt/g4-MMAE were validated in vivo using three pancreatic cancer xenograft models. Toxicological activities of H-Zt/g4-MMAE were determined in mouse and cynomolgus monkey.

RESULTS

H-Zt/g4-MMAE had a drug to antibody ratio of 3.77:1 and was highly stable in human plasma with a dissociation rate less than 5% within a 20 day period. H-Zt/g4-MMAE displayed a favorable pharmacokinetic profile in both mouse and cynomolgus monkey. In vitro, H-Zt/g4-MMAE induced RON internalization, which results in killing of pancreatic cancer cells with IC₅₀ values at 10-20 nM. In vivo, H-Zt/g4-MMAE inhibited pancreatic cancer xenograft growth with tumoristatic concentrations at 1~3 mg/kg bodyweight. Significantly, H-Zt/g4-MMAE eradicated tumors across multiple xenograft models regardless their chemoresistant and metastatic statuses. Moreover, H-Zt/g4-MMAE inhibited and eradicated xenografts mediated by pancreatic cancer stem-like cells and by primary cells from patient-derived tumors. Toxicologically, H-Zt/g4-MMAE is well tolerated in mice up to 60 mg/kg. In cynomolgus monkey, H-Zt/g4-MMAE up to 30 mg/kg had a manageable and reversible toxicity profile.

CONCLUSIONS

H-Zt/g4-MMAE is superior in eradication of pancreatic cancer xenografts with favorable pharmacokinetic profiles and manageable toxicological activities. These findings warrant the transition of H-Zt/g4-MMAE into clinical trials in the future.

Therapeutic Considerations for Ron Receptor Expression in Prostate Cancer

INTRODUCTION

The Ron receptor tyrosine kinase was initially discovered as a protein which played a critical role in regulating inflammatory responses. This effect was primarily determined through studies in various macrophage populations. Since its initial discovery, a role has emerged for Ron as a driver of cancer within epithelial cells. After numerous publications have detailed a role for Ron in promoting tumor initiation, growth, and metastasis, Ron has been designated as an emerging therapeutic option in a variety of cancers.

AREAS COVERED

This review discusses the current literature regarding the role of Ron in prostate cancer and places special emphasis on the role of Ron in both epithelial cells and macrophages. Whole body loss of Ron signaling initially exposed a variety of prostate cancer growth mechanisms regulated by Ron. With the knowledge that Ron plays an integral part in regulating the function of epithelial cells and macrophages, studies commenced to discern the cell type specific functions for Ron in prostate cancer. A novel role for Ron in promoting Castration Resistant Prostate Cancer has recently been uncovered, and the results of these studies are summarized herein. Furthermore, this review gives a summary of several currently available compounds which show promise at targeting Ron in both epithelial and macrophage populations.

OUTLOOK

Sufficient evidence has been provided for the initiation of clinical trials focused on targeting Ron in both macrophage and epithelial compartments for the treatment of prostate cancer. A number of therapeutic avenues for targeting Ron in prostate cancer are currently available; however, special consideration will need to take place knowing that Ron signaling impacts multiple cell types. Further understanding of the cell type specific functions of Ron in prostate cancer will help inform and shape future clinical research and therapeutic strategies.

Automatic cell fusion via optically-induced dielectrophoresis and optically-induced locally-enhanced electric field on a microfluidic chip

Cell fusion technology has been exploited in a wide variety of biomedical applications, and physical, chemical, and biological approaches can all be used to fuse two different types of cells; however, no current technique is adept at inducing both cell pairing and fusion at high efficiencies and yields. Hence, we developed a new method featuring the use of optically induced dielectrophoresis (ODEP) in conjunction with an optically induced, locally enhanced electric field for accurate and automatic cell pairing and fusion on a microfluidic device. After pairing cells via ODEP, a locally enhanced electric field generated by "virtual electrodes" by projecting light patterns was enacted to induce a proper transmembrane potential at the cell contact area such that cell fusion could be triggered by white light exposure. As a fusion yield of 9.67% was achieved between Pan1 and A549 cells, we believe that this may be a promising technique for automatically fusing different cell types.

Function of the c-Met receptor tyrosine kinase in carcinogenesis and associated therapeutic opportunities

c-Met is a receptor tyrosine kinase belonging to the MET (MNNG HOS transforming gene) family, and is expressed on the surfaces of various cells. Hepatocyte growth factor (HGF) is the ligand for this receptor. The binding of HGF to c-Met initiates a series of intracellular signals that mediate embryogenesis and wound healing in normal cells. However, in cancer cells, aberrant HGF/c-Met axis activation, which is closely related to c-Met gene mutations, overexpression, and amplification, promotes tumor development and progression by stimulating the PI3K/AKT, Ras/MAPK, JAK/STAT, SRC, Wnt/β-catenin, and other signaling pathways. Thus, c-Met and its associated signaling pathways are clinically important therapeutic targets. In this review, we elaborate on the molecular structure of c-Met and HGF and the mechanism through which their interaction activates the PI3K/AKT, Ras/MAPK, and Wnt signaling pathways. We also summarize the connection between c-Met and RON and EGFR, which are also receptor tyrosine kinases. Finally, we introduce the current therapeutic drugs that target c-Met in primary tumors, and their use in clinical research.

Crosstalk between RON and androgen receptor signaling in the development of castration resistant prostate cancer

Castrate-resistant prostate cancer (CRPC) is the fatal form of prostate cancer. Although reactivation of androgen receptor (AR) occurs following androgen deprivation, the precise mechanism involved is unclear. Here we show that the receptor tyrosine kinase, RON alters mechanical properties of cells to influence epithelial to mesenchymal transition and functions as a transcription factor to differentially regulate AR signaling. RON inhibits AR activation and subset of AR-regulated transcripts in androgen responsive LNCaP cells. However in C4-2B, a castrate-resistant sub-line of LNCaP and AR-negative androgen independent DU145 cells, RON activates subset of AR-regulated transcripts. Expression of AR in PC-3 cells leads to activation of RON under androgen deprivation but not under androgen proficient conditions implicating a role for RON in androgen independence. Consistently, RON expression is significantly elevated in castrate resistant prostate tumors. Taken together our results suggest that RON activation could aid in promoting androgen independence and that inhibition of RON in combination with AR antagonist(s) merits serious consideration as a therapeutic option during hormone deprivation therapy.

The Role of Platelet-Derived ADP and ATP in Promoting Pancreatic Cancer Cell Survival and Gemcitabine Resistance

Platelets have been demonstrated to be vital in cancer epithelial-mesenchymal transition (EMT), an important step in metastasis. Markers of EMT are associated with chemotherapy resistance. However, the association between the development of chemoresistance, EMT, and the contribution of platelets to the process, is still unclear. Here we report that platelets regulate the expression of (1) human equilibrative nucleoside transporter 1 (hENT1) and (2) cytidine deaminase (CDD), markers of gemcitabine resistance in pancreatic cancer. Human ENT1 (hENT1) is known to enable cellular uptake of gemcitabine while CDD deactivates gemcitabine. Knockdown experiments demonstrate that Slug, a mesenchymal transcriptional factor known to be upregulated during EMT, regulates the expression of hENT1 and CDD. Furthermore, we demonstrate that platelet-derived ADP and ATP regulate Slug and CDD expression in pancreatic cancer cells. Finally, we demonstrate that pancreatic cancer cells express the purinergic receptor P2Y₁₂, an ADP receptor found mainly on platelets. Thus ticagrelor, a P2Y₁₂ inhibitor, was used to examine the potential therapeutic effect of an ADP receptor antagonist on cancer cells. Our data indicate that ticagrelor negated the survival signals initiated in cancer cells by platelet-derived ADP and ATP. In conclusion, our results demonstrate a novel role of platelets in modulating chemoresistance in pancreatic cancer. Moreover, we propose ADP/ATP receptors as additional potential drug targets for treatment of pancreatic cancer.

Prognostic value of loss of heterozygosity and sub-cellular localization of SMAD4 varies with tumor stage in colorectal cancer

Background

Although loss of heterozygosity (LOH) at chromosome location 18q21 and decreased expression of SMAD4 in invasive colorectal cancers (CRCs) correlate with poor patient survival, the prognostic value of LOH at 18q21 and sub-cellular localization of SMAD4 have not been evaluated in relation to tumor stage.

Methods

Genomic DNA samples from 209 formalin-fixed, paraffin-embedded sporadic CRC tissues and their matching controls were analyzed for 18q21 LOH, and corresponding tissue sections were evaluated by immunohistochemistry for expression of SMAD4 and assessed for its sub-cellular localization (nuclear vs. cytoplasmic). In addition, 53 frozen CRCs and their matching control tissues were analyzed for their mutational status and mRNA expression of SMAD4. The phenotypic expression pattern and LOH status were evaluated for correlation with patient survival by the use of Kaplan-Meier and Cox regression models.

Results

LOH of 18q21 was detected in 61% of the informative cases. In 8% of the cases, missense point mutations were detected in Smad4. In CRCs, relative to controls, there was increased SMAD4 staining in the cytoplasm (74%) and decreased staining in the nuclei (37%). LOH of 18q21 and high cytoplasmic localization of SMAD4 were associated with shortened overall survival of Stage II patients, whereas low nuclear expression of SMAD4 was associated with worse survival, but only for patients with Stage III CRCs.

Conclusions

LOH of 18q21 and high cytoplasmic localization of SMAD4 in Stage II CRCs and low nuclear SMAD4 in Stage III CRCs are predictors of shortened patient survival.

miR‑196a‑5p modulates gastric cancer stem cell characteristics by targeting Smad4

Cancer stem cells (CSCs) are undifferentiated cancer cells with a high tumorigenic activity, the ability to undergo self-renewal, and a multilineage differentiation potential. Clinical evidence suggests that CSCs in a tumor mass are the cellular determinants to promote cancer invasion and metastasis. MicroRNAs (miRNAs) have emerged as important modulators of cancer stem cell characteristics. Unveiling the candidate miRNAs that regulate CSCs may provide novel therapeutic targets against cancer. We analyzed the miRNA expression profiles regulating the cancer stem-like cell characteristics in gastric cancer. Gastric cancer stem cells (GCSCs) were sorted using the stem cell marker CD44 by fluorescence-activated cell sorting. Functional studies revealed that CD44(+) cells formed more sphere colonies and showed higher invasiveness than CD44(−) cells. miRNA microarray analysis revealed that miR-196a-5p was significantly upregulated in CD44(+) cells than CD44(−) cells. Suppression of miR-196a-5p led to decreased colony formation and invasion of GCSCs. miR-196a-5p decreased the expression of Smad4 by targeting 3′-UTR of the mRNA. The expression of Smad4 in gastric cancer tissues was correlated with differentiation state of tumors, TNM stage and depth of invasion. The stimulation of epithelial-mesenchymal transition (EMT) by miR-196a-5p in cancer stem-like cells was abolished by overexpression of Smad4. Collectively, these data demonstrate that miR-196a-5p has a key role in EMT and invasion by targeting Smad4 in GCSCs. miR-196a-5p may serve as a potential target for gastric cancer therapy.

Effects of PTCs on nonsense-mediated mRNA decay are dependent on PTC location

The récepteur d'origine nantais (RON) gene is a proto-oncogene that is responsible for encoding the human macrophage-stimulating protein (MSP) 1 receptor. MSP activation induces RON-mediated cell dissociation, migration and matrix invasion. Isoforms of RON that exclude exons 5 and 6 encode the RONΔ160 protein, which promotes cell transformation in vitro and tumor metastasis in vivo. Premature termination codons (PTCs) in exons activate the nonsense-mediated mRNA decay (NMD) signaling pathway. The present study demonstrated that PTCs at various locations in the alternative exons 5 and 6 could induce NMD of the majority of the spliced, or partially spliced, isoforms. However, the isoforms that excluded exon 6 or exons 5 and 6 were markedly increased when produced from mutated minigenes with inserted PTCs. Furthermore, the unspliced isoform of intron 5 was not observed to be decreased by the presence of PTCs. Notably, these effects may be dependent on the location of the PTCs. The current study demonstrated a novel mechanism underlying the regulation of NMD in alternative splicing.

Cadherin-11 Is a Cell Surface Marker Up-Regulated in Activated Pancreatic Stellate Cells and Is Involved in Pancreatic Cancer Cell Migration

Chronic pancreatitis is a prominent risk factor for the development of pancreatic ductal adenocarcinoma. In both conditions, the activation of myofibroblast-like pancreatic stellate cells (PSCs) plays a predominant role in the formation of desmoplastic reaction through the synthesis of connective tissue and extracellular matrix, inducing local pancreatic fibrosis and an inflammatory response. Yet the signaling events involved in chronic pancreatitis and pancreatic cancer progression and metastasis remain poorly defined. Cadherin-11 (Cad-11, also known as OB cadherin or CDH11) is a cell-to-cell adhesion molecule implicated in many biological functions, including tissue morphogenesis and architecture, extracellular matrix-mediated tissue remodeling, cytoskeletal organization, epithelial-to-mesenchymal transition, and cellular migration. In this study, we show that, in human chronic pancreatitis and pancreatic cancer tissues, Cad-11 expression was significantly increased in PSCs and pancreatic cancer cells. In particular, an increased expression of Cad-11 can be detected on the plasma membrane of activated PSCs isolated from chronic pancreatitis tissues and in pancreatic cancer cells metastasized to the liver. Moreover, knockdown of Cad-11 in cancer cells reduced pancreatic cancer cell migration. Taken together, our data underline the potential role of Cad-11 in PSC activation and pancreatic cancer metastasis.

Roles of c-Met and RON kinases in tumor progression and their potential as therapeutic targets

c-Met and receptor originated from nantes (RON) are structurally related transmembrane phosphotyrosine kinase receptors. c-Met and RON show increased expression or activity in a variety of tumors leading to tumor progression and may play a role in acquired resistance to therapy. Although often co-expressed, the distinct functional roles of c-Met and RON are not fully understood. c-Met and RON form both activated homodimers and heterodimers with themselves and other families of phosphotyrosine kinase receptors. Inhibitors for c-Met and RON including small molecular weigh kinase inhibitors and neutralizing antibodies are in pre-clinical investigation and clinical trials. Several of the tyrosine kinase inhibitors have activity against both c-Met and RON kinases whereas the antibodies generally are target specific. As with many targeted agents used to treat solid tumors, it is likely that c-Met/RON inhibitors will have greater benefit when used in combination with chemotherapy or other targeted agents. A careful analysis of c-Met/RON expression or activity and a better elucidation of how they influence cell signaling will be useful in predicting which tumors respond best to these inhibitors as well as determining which agents can be used with these inhibitors for combined therapy.

Insights Into SMAD4 Loss in Pancreatic Cancer From Inducible Restoration of TGF-β Signaling

Pancreatic ductal adenocarcinoma (PDAC) is the fourth-leading cause of cancer death in the United States. The TGF-β signaling protein SMAD family member 4 is lost in 60% of PDAC, and this has been associated with poorer prognosis. However, the mechanisms by which SMAD4 loss promotes PDAC development are not fully understood. We expressed SMAD4 in human PDAC cell lines BxPC3 and CFPAC1 by selection of stable clones containing an inducible SMAD4 tetracycline inducible expression system construct. After 24 hours of SMAD4 expression, TGF-β signaling-dependent G1 arrest was observed in BxPC3 cells with an increase in the G1 phase fraction from 48.9% to 71.5%. Inhibition of cyclin-dependent kinase inhibitor 1A by small interfering RNA eliminated the antiproliferative effect, indicating that up-regulation of cyclin-dependent kinase inhibitor 1A/p21 by TGF-β signaling is necessary for the phenotype. SMAD4 expression had no impact on invasion in BxPC3 cells, but reduced migration. Microarray analysis of gene expression at 8, 24, and 48 hours after SMAD4 expression characterized the regulatory impact of SMAD4 expression in a SMAD4-null PDAC cell line and identified novel targets of TGF-β signaling. Among the novel TGF-β targets identified are anthrax toxin receptor 2 (3.58× at 8 h), tubulin, β-3 class III (7.35× at 8 h), cell migration inducing protein, hyaluronan binding (8.07× at 8 h), IL-1 receptor-like 1 (0.403× at 8 h), regulator of G protein signaling 4 (0.293× at 8 h), and THAP domain containing 11 (0.262× at 8 h). The gene expression changes we observed upon restoration of TGF-β signaling provide numerous new targets for future investigations into PDAC biology and progression.

The involvement of insulin-like growth factor 2 binding protein 3 (IMP3) in pancreatic cancer cell migration, invasion, and adhesion

Background

Over-expression of insulin-like growth factor 2 mRNA binding protein 3 (IMP3) is correlated with poor prognosis in pancreatic ductal adenocarcinoma (PDAC). Previous studies examining other cancer types have implicated IMP3 in the regulation of several cellular functions that are characteristic of tumour cells. However, the role of this oncofetal protein in PDAC progression remained unclear.

Methods

Using siRNA, we examined the effect of IMP3 inhibition on the motility, invasive ability, and matrix adhesion of PDAC cells. In addition, we also evaluated the expression of cytoskeleton-associated genes following IMP depletion.

Results

Knockdown of IMP3 significantly decreased the motility, invasion, and extracellular matrix adhesion of select PDAC cells in vitro. In addition, IMP3-depleted cells exhibited lower levels of CD44 protein and KIF11 mRNA. Moreover, we also observed a reduction in downstream RhoA signaling following IMP3 knockdown, indicating that IMP3 modulates the levels of proteins involved in cytoskeletal organization.

Conclusions

These results suggest that IMP3 facilitates PDAC progression by enhancing the pro-metastatic behaviour of tumour cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1251-8) contains supplementary material, which is available to authorized users.

SMAD4 and its role in pancreatic cancer

Transforming growth factor-β (TGF-β) regulates cell functions and has key roles in pancreatic cancer development. SMAD4, as one of the Smads family of signal transducer from TGF-β, mediates pancreatic cell proliferation and apoptosis and is specifically inactivated in half of advanced pancreatic cancers. In recent years, many advances concerning SMAD4 had tried to unravel the complex signaling mechanisms of TGF-β and its dual role of tumor-suppressive and tumor-promoting efforts in pancreatic cancer initiation and progression through SMAD4-dependent TGF-β signaling and SMAD4-independent TGF-β signaling pathways. Meanwhile, its potential prognostic value based on immunohistochemical expression in surgical sample was variably reported by several studies and short of a systematic analysis. This review aimed to discuss the structure, functions, and regulation of this principal protein and its effects in determining the progression and prognosis of pancreatic cancer.

A miRNA signature of chemoresistant mesenchymal phenotype identifies novel molecular targets associated with advanced pancreatic cancer

In this study a microRNA (miRNA) signature was identified in a gemcitabine resistant pancreatic ductal adenocarcinoma (PDAC) cell line model (BxPC3-GZR) and this signature was further examined in advanced PDAC tumor specimens from The Cancer Genome Atlas (TCGA) database. BxPC3-GZR showed a mesenchymal phenotype, expressed high levels of CD44 and showed a highly significant deregulation of 17 miRNAs. Based on relevance to cancer, a seven-miRNA signature (miR-100, miR-125b, miR-155, miR-21, miR-205, miR-27b and miR-455-3p) was selected for further studies. A strong correlation was observed for six of the seven miRNAs in 43 advanced tumor specimens compared to normal pancreas tissue. To assess the functional relevance we initially focused on miRNA-125b, which is over-expressed in both the BxPC3-GZR model and advanced PDAC tumor specimens. Knockdown of miRNA-125b in BxPC3-GZR and Panc-1 cells caused a partial reversal of the mesenchymal phenotype and enhanced response to gemcitabine. Moreover, RNA-seq data from each of 40 advanced PDAC tumor specimens from the TCGA data base indicate a negative correlation between expression of miRNA-125b and five of six potential target genes (BAP1, BBC3, NEU1, BCL2, STARD13). Thus far, two of these target genes, BBC3 and NEU1, that are tumor suppressor genes but not yet studied in PDAC, appear to be functional targets of miR-125b since knockdown of miR125b caused their up regulation. These miRNAs and their molecular targets may serve as targets to enhance sensitivity to chemotherapy and reduce metastatic spread.

Synergistic activities of MET/RON inhibitor BMS-777607 and mTOR inhibitor AZD8055 to polyploid cells derived from pancreatic cancer and cancer stem cells

Tyrosine kinase inhibitor BMS-777067 is an inhibitor of RON/MET receptor tyrosine kinases currently under clinical trials. Here, we report the synergistic activity of BMS-777607 in combination with mTOR inhibitor AZD8055 in killing chemoresistant pancreatic cancer and cancer stem cells. Treatment of pancreatic cancer L3.6pl cells with BMS-777607 alone inhibited clonogenic growth and moderately induced apoptotic death. However, BMS-777607 caused extensive polyploidy in L3.6pl cells through inhibition of aurora kinase B activity, independent of RON expression. In contrast, L3.6pl-derived cancer stem cells were highly resistant to BMS-777607-induced growth inhibition and apoptosis. The effect of BMS-777607 on induction of cancer stem cell polyploidy was also weak. BMS-777607-induced polyploidy features a predominant cell population with 8N chromosome content in both L3.6pl and cancer stem cells. These cells also showed decreased sensitivity toward chemotherapeutics by increased survival of IC(50) values in response to doxorubicin, cisplatin, methotrexate, 5-fluorouracial, and gemcitabine. Among a panel of chemical inhibitors that target different signaling proteins, we found that BMS-777607 in combination with mTOR inhibitor AZD8055 exerted synergistic effects on L3.6pl and cancer stem cells. More than 70% of L3.6pl and cancer stem cells lost their viability when both inhibitors were used. Specifically, BMS-777607 in combination with inhibition of mTORC2, but not mTORC1, was responsible for the observed synergism. Our findings demonstrate that BMS-777607 at therapeutic doses exerts inhibitory activities on pancreatic cancer cells but also induces polyploidy insensitive to chemotherapeutics. Combination of BMS-777607 with AZD8055 achieves the maximal cytotoxic effect on pancreatic cancer and cancer stem cells.

Loss of canonical Smad4 signaling promotes KRAS driven malignant transformation of human pancreatic duct epithelial cells and metastasis

Pancreatic ductal adenocarcinoma (PDAC) is the fourth most common cause of cancer death in North America. Activating KRAS mutations and Smad4 loss occur in approximately 90% and 55% of PDAC, respectively. While their roles in the early stages of PDAC development have been confirmed in genetically modified mouse models, their roles in the multistep malignant transformation of human pancreatic duct cells have not been directly demonstrated. Here, we report that Smad4 represents a barrier in KRAS-mediated malignant transformation of the near normal immortalized human pancreatic duct epithelial (HPDE) cell line model. Marked Smad4 downregulation by shRNA in KRAS^G12V expressing HPDE cells failed to cause tumorigenic transformation. However, KRAS-mediated malignant transformation occurred in a new HPDE-TGF-β resistant (TβR) cell line that completely lacks Smad4 protein expression and is resistant to the mito-inhibitory activity of TGF-β. This transformation resulted in tumor formation and development of metastatic phenotype when the cells were implanted orthotopically into the mouse pancreas. Smad4 restoration re-established TGF-β sensitivity, markedly increased tumor latency by promoting apoptosis, and decreased metastatic potential. These results directly establish the critical combination of the KRAS oncogene and complete Smad4 inactivation in the multi-stage malignant transformation and metastatic progression of normal human HPDE cells.

Oncogenic K-Ras and loss of Smad4 mediate invasion by activating an EGFR/NF-κB Axis that induces expression of MMP9 and uPA in human pancreas progenitor cells

Activating K-Ras mutations and inactivating mutations of Smad4 are two common genetic alterations that occur in the development and progression of pancreatic ductal adenocarcinomas (PDAC). To further study the individual and combinatorial roles of these two mutations in the pathogenesis of PDAC, immortalized human pancreas nestin postive cells (HPNE) were genetically modified by either expressing oncogenic K-Ras (HPNE/K-Ras), by shRNA knock down of Smad4 (HPNE/ShSmad4) or by creating both alterations in the same cell line (HPNE/K-Ras/ShSmad4). We previously found that expression of oncogenic K-Ras caused an increase in expression of EGFR and loss of Smad4 further enhanced the up regulation in expression of EGFR and that this increase in EGFR was sufficient to induce invasion. Here we further investigated the mechanism that links mutational alterations and EGFR expression with invasion. The increase in EGFR signaling was associated with up regulation of MMP9 and uPA protein and activity. Moreover, the increase in EGFR signaling promoted a nuclear translocation and binding of RelA (p65), a subunit of NF-κB, to the promoters of both MMP-9 and uPA. Treatment of HPNE/K-Ras/ShSmad4 cells with an inhibitor of EGFR reduced EGF-mediated NF-κB nuclear translocation and inhibitors of either EGFR or NF-κB reduced the increase in MMP-9 or uPA expression. In conclusion, this study provides the mechanism of how a combination of oncogenic K-Ras and loss of Smad4 causes invasion and provides the basis for new strategies to inhibit metastases.

Knockdown of RON receptor kinase delays but does not prevent tumor progression while enhancing HGF/MET signaling in pancreatic cancer cell lines

In this study, the role of RON (receptor originated from nantes) in tumor progression was further investigated in context with MET expression and activity. RON and MET expressions were not detected in an immortalized normal human pancreas cell line (HPNE), but were co-expressed in five of seven pancreatic ductal adenocarcinoma (PDAC) cell lines (PANC-1, BxPC-3, Capan-2, CFPAC-1 and AsPC-1). RON expression was knocked down by an shRNA approach in two PDAC cell lines (BxPC-3 and CFPAC-1) that co-express MET. Knockdown of RON significantly inhibited cell growth, clonogenicity and macrophage stimulating protein (MSP), RON ligand induced invasion by in vitro assays and significantly inhibited tumor growth (P<0.001) and metastasis (P<0.009) in an orthotopic pancreatic cancer mouse model at week 7. However, by week 9, the mice implanted with RON knockdown cells had developed similar size primary tumors and metastases compared with that seen in the control group at week 7. Western blotting and immunohistochemistry analyses showed that MET remains highly expressed in cells and tumor tissues where RON was knocked down. Moreover, knockdown of RON did not prevent hepatocyte growth factor (HGF) stimulated invasion in in vitro Matrigel assays. Treating cells with MSP induced the transphosphorylation of MET, suggesting that signaling may be modulated by relative levels of RON and MET receptors and their corresponding ligands. To this point, HGF treatment of RON knockdown cells caused an increase in intensity and duration of MET signaling, suggesting that MET signaling may compensate for loss of RON signaling. Treatment of cells with an MET inhibitor, PHA-665752, had minimal effects on inhibiting cell growth but significantly inhibited cell invasion induce by ligands for either MET or RON. These results suggest that HGF/MET signaling may have a more important role in tumor cell invasion and metastasis rather than in tumor cell proliferation. This study indicates that specific inhibition of RON delays but does not prevent progression of PDAC. Moreover, specific signaling may be modulated by the interaction of RON and MET receptors. This dynamic interaction of RON and MET in pancreatic cancer cells suggests that dual targeting of both RON and MET will be preferable to inhibition of either target alone.

Ron knockdown and Ron monoclonal antibody IMC-RON8 sensitize pancreatic cancer to histone deacetylase inhibitors (HDACi)

Recepteur d'origine nantais (Ron) is overexpressed in a panel of pancreatic cancer cells and tissue samples from pancreatic cancer patients. Ron can be activated by its ligand macrophage stimulating protein (MSP), thereby activating oncogenic signaling pathways. Crosstalk between Ron and EGFR, c-Met, or IGF-1R may provide a mechanism underlying drug resistance. Thus, targeting Ron may represent a novel therapeutic strategy. IMC-RON8 is the first Ron monoclonal antibody (mAb) entering clinical trial for targeting Ron overexpression. Our studies show IMC-RON8 downmodulated Ron expression in pancreatic cancer cells and significantly blocked MSP-stimulated Ron activation, downstream Akt and ERK phosphorylation, and survivin mRNA expression. IMC-RON8 hindered MSP-induced cell migration and reduced cell transformation. Histone deacetylase inhibitors (HDACi) are reported to target expression of various genes through modification of nucleosome histones and non-histone proteins. Our work shows HDACi TSA and Panobinostat (PS) decreased Ron mRNA and protein expression in pancreatic cancer cells. PS also reduced downstream signaling of pAkt, survivin, and XIAP, as well as enhanced cell apoptosis. Interestingly, PS reduced colony formation in Ron knockdown cells to a greater extent than Ron scramble control cells in colony formation and soft agarose assays. IMC-RON8 could also sensitize pancreatic cancer cells to PS, as reflected by reduced colony numbers and size in combination treatment with IMC-RON8 and PS compared to single treatment alone. The co-treatment further reduced Ron expression and pAkt, and increased PARP cleavage compared to either treatment alone. This study suggests the potential for a novel combination approach which may ultimately be of value in treatment of pancreatic cancer.

MSP-RON signalling in cancer: pathogenesis and therapeutic potential

Since the discovery of MSP (macrophage-stimulating protein; also known as MST1 and hepatocyte growth factor-like (HGFL)) as the ligand for the receptor tyrosine kinase RON (also known as MST1R) in the early 1990s, the roles of this signalling axis in cancer pathogenesis has been extensively studied in various model systems. Both in vitro and in vivo evidence has revealed that MSP-RON signalling is important for the invasive growth of different types of cancers. Currently, small-molecule inhibitors and antibodies blocking RON signalling are under investigation. Substantial responses have been achieved in human tumour xenograft models, laying the foundation for clinical validation. In this Review, we discuss recent advances that demonstrate the importance of MSP-RON signalling in cancer and its potential as a therapeutic target.

Ron tyrosine kinase receptor synergises with EGFR to confer adverse features in head and neck squamous cell carcinoma

Background:

Although EGFR inhibitors have shown some success in the treatment of head and neck squamous cell carcinomas (HNSCCs), the results are not dramatic. Additional molecular targets are urgently needed. We previously showed that the loss of Ron receptor activity significantly slowed squamous tumour growth and progression in a murine model. Based on these data, we hypothesised that Ron expression confers an aggressive phenotype in HNSCCs.

Methods:

We prospectively collected and evaluated 154 snap-frozen, primary HNSCCs for Ron and EGFR expression/phosphorylation. Biomarker correlation with clinical, pathological and outcome data was performed. The biological responses of HNSCC cell lines to Ron knockdown, its activation and the biochemical interaction between Ron and EGFR were examined.

Results:

We discovered that 64.3% (99 out of 154) HNSCCs expressed Ron. The carcinomas expressed exclusively mature functional Ron, whereas the adjacent nonmalignant epithelium expressed predominantly nonfunctional Ron precursor. There was no significant association between Ron and sex, tumour differentiation, perineural/vascular invasion or staging. However, patients with Ron+HNSCC were significantly older and more likely to have oropharyngeal tumours. Ron+HNSCC also had significantly higher EGFR expression and correlated strongly with phosphorylated EGFR (pEGFR). Newly diagnosed HNSCC with either Ron/pEGFR or both had lower disease-free survival than those without Ron and pEGFR. Knocking down Ron in SCC9 cells significantly blunted their migratory response to not only the Ron ligand, MSP, but also EGF. Stimulation of Ron in SCC9 cells significantly augmented the growth effect of EGF; the synergistic effect of both growth factors in SCC9 cells was dependent on Ron expression. Activated Ron also interacted with and transactivated EGFR.

Conclusion:

Ron synergises with EGFR to confer certain adverse features in HNSCCs.

TGF-β1, Smad-2/-3, Smad-1/-5/-8, and Smad-4 signaling factors are expressed in ameloblastomas, adenomatoid odontogenic tumors, and calcifying cystic odontogenic tumors: an immunohistochemical study

OBJECTIVES

The TGF-β/Smad signaling pathway regulates diverse cellular functions, including tooth development, and is involved in numerous pathological processes such as tumorigenesis. The aim of this study was to investigate the immunoexpression of the TGF-β/Smad signaling pathway members in ameloblastoma (AM), calcifying cystic odontogenic tumor (CCOT), and adenomatoid odontogenic tumor (AOT).

MATERIALS AND METHODS

This retrospective cross-sectional study included 65 tissue specimens: 34 AMs, 13 CCOTs, and 18 AOTs. Serial sections were immunohistochemically stained with TGF-β1, Smad-4, Smad-1/-5/-8, and Smad-2/-3 antibodies, and a semiquantitative measurement of the positive cells was carried out by two oral pathologists using a 0-3 scale (0: no immunoreactivity, 1: <20% positive cells, 2: 20-50% positive cells, 3: >50% positive cells).

RESULTS

All biomarkers studied were found significantly decreased in AM compared to CCOT and AOT. AOT and CCOT expressed Smad-1/-5/-8 more strongly compared to AM (OR = 11.66, P < 0.001 and OR = 5.34, P = 0.013, respectively), and Smad-2/-3 immunostaining was found significantly increased in CCOT (OR = 10.42, P = 0.001) and AOT (OR = 5.16, P < 0.004) compared to AM. Similarly, Smad-4 was expressed more strongly in AOT and CCOT compared to AM (P = 0.001), while AOT demonstrated a fivefold higher chance to express TGF-β1 compared to AM (P = 0.011).

CONCLUSION

TGF-β/Smad signaling pathway is activated in AM, AOT, and CCOT. The statistically significant reduced TGF-β1/Smad immunoexpression in AM compared to AOT/CCOT could be associated with the more aggressive biological behavior of AM including increased cell proliferation and reduced apoptosis and differentiation. Thus, the biomarkers TGF-β, Smad-4, Smad-1/-5/-8, and Smad-2/-3 could serve as supplementary diagnostic indices between odontogenic tumors of high and low neoplastic dynamics.

Transforming growth factor-β/SMAD Target gene SKIL is negatively regulated by the transcriptional cofactor complex SNON-SMAD4

The human SKI-like (SKIL) gene encodes the SMAD transcriptional corepressor SNON that antagonizes TGF-β signaling. SNON protein levels are tightly regulated by the TGF-β pathway: whereas a short stimulation with TGF-β decreases SNON levels by its degradation via the proteasome, longer TGF-β treatment increases SNON levels by inducing SKIL gene expression. Here, we investigated the molecular mechanisms involved in the self-regulation of SKIL gene expression by SNON. Bioinformatics analysis showed that the human SKIL gene proximal promoter contains a TGF-β response element (TRE) bearing four groups of SMAD-binding elements that are also conserved in mouse. Two regions of 408 and 648 bp of the human SKIL gene (∼2.4 kb upstream of the ATG initiation codon) containing the core promoter, transcription start site, and the TRE were cloned for functional analysis. Binding of SMAD and SNON proteins to the TRE region of the SKIL gene promoter after TGF-β treatment was demonstrated by ChIP and sequential ChIP assays. Interestingly, the SNON-SMAD4 complex negatively regulated basal SKIL gene expression through binding the promoter and recruiting histone deacetylases. In response to TGF-β signal, SNON is removed from the SKIL gene promoter, and then the activated SMAD complexes bind the promoter to induce SKIL gene expression. Subsequently, the up-regulated SNON protein in complex with SMAD4 represses its own expression as part of the negative feedback loop regulating the TGF-β pathway. Accordingly, when the SNON-SMAD4 complex is absent as in some cancer cells lacking SMAD4 the regulation of some TGF-β target genes is modified.

RhoT1 and Smad4 are correlated with lymph node metastasis and overall survival in pancreatic cancer

Cancer cell invasion and metastasis are the most important adverse prognostic factors for pancreatic cancer. Identification of biomarkers associated with outcome of pancreatic cancer may provide new approaches and targets for anticancer therapy. The aim of this study is to examine the relationship between the expression of RhoT1, Smad4 and p16 and metastasis and survival in patients with pancreatic cancer. The analysis showed that the high cytoplasmic expression levels of RhoT1, Smad4 and p16 in pancreatic cancer tissues had significantly negative correlation with lymph node metastasis (LNM) (P = 0.017, P = 0.032, P = 0.042, respectively). However, no significant association was observed between perineural invasion (PNI) and the expression of above three proteins (all P>0.05). Additionally, the survival analysis showed that the low expression levels of RhoT1 and Smad4 were significantly associated with worse survival (P = 0.034, P = 0.047, respectively). In conclusion, these results indicated that the low-expression levels of RhoT1 and Smad4 were significantly associated with LNM and shorter survival. RhoT1 may be considered as a potential novel marker for predicting the outcome in patients with pancreatic cancer.

Immunoassay-based proteome profiling of 24 pancreatic cancer cell lines

Pancreatic ductal adenocarcinoma is one of the most deadly forms of cancers, with a mortality that is almost identical to incidence. The inability to predict, detect or diagnose the disease early and its resistance to all current treatment modalities but surgery are the prime challenges to changing the devastating prognosis. Also, relatively little is known about pancreatic carcinogenesis. In order to better understand relevant aspects of pathophysiology, differentiation, and transformation, we analysed the cellular proteomes of 24 pancreatic cancer cell lines and two controls using an antibody microarray that targets 741 cancer-related proteins. In this analysis, 72 distinct disease marker proteins were identified that had not been described before. Additionally, categorizing cancer cells in accordance to their original location (primary tumour, liver metastases, or ascites) was made possible. A comparison of the cells' degree of differentiation (well, moderately, or poorly differentiated) resulted in unique marker sets of high relevance. Last, 187 proteins were differentially expressed in primary versus metastatic cancer cells, of which the majority is functionally related to cellular movement.

Sustained expression of the RON receptor tyrosine kinase by pancreatic cancer stem cells as a potential targeting moiety for antibody-directed chemotherapeutics

Cancer stem cells (CSCs) contribute to pancreatic cancer tumorigenesis through tumor initiation, drug resistance, and metastasis. Currently, therapeutics targeting pancreatic CSCs are under intensive investigation. This study tested a novel strategy that utilizes the RON receptor as a drug delivery moiety for increased therapeutic activity against pancreatic CSCs. CD24(+)CD44(+)ESA(+) triple-positive pancreatic CSCs (CSCs(+24/44/ESA)) were obtained from spheroids of pancreatic L3.6pl cancer cells by sequential magnetic cell sorting methods. These cells displayed a spherical growth pattern, expressed the unique self-renewal marker Bmi-1, redifferentiated into an epithelial phenotype, acquired an epithelial to mesenchymal phenotype, and caused tumor formation in animal models. Among several receptor tyrosine kinases examined, RON was highly expressed and sustained by CSCs(+24/44/ESA). This feature provided the cellular basis for validating the therapeutic effectiveness of anti-RON antibody Zt/c9-directing doxorubicin-immunoliposomes (Zt/c9-Dox-IL). Zt/c9-Dox-IL specifically interacted with CSCs(+24/44/ESA) and rapidly caused RON internalization, which led to the uptake of liposome-coated Dox. Moreover, Zt/c9-Dox-IL was effective in reducing viability of L3.6pl cells and CSCs(+24/44/ESA). The IC(50) values between free Dox (62.0 ± 3.1 μM) and Zt/c9-Dox-IL (95.0 ± 6.1 μM) treated CSCs(+24/44/ESA) were at relatively comparable levels. In addition, Zt/c9-Dox-IL in combination with small molecule inhibitors lapatinib, sunitinib, or dasatinib further reduced the viability of CSCs(+24/44/ESA). In conclusion, RON expression by CSCs(+24/44/ESA) is a suitable molecule for the targeted delivery of chemoagents. The anti-RON antibody-directed delivery of chemotherapeutics is effective in reducing viability of pancreatic CSCs.

Molecular biology of pancreatic ductal adenocarcinoma progression: aberrant activation of developmental pathways

Embryonic development marks a period of peak tissue growth and morphogenesis in the mammalian lifecycle. Many of the pathways that underlie cell proliferation and movement are relatively quiescent in adult animals but become reactivated during carcinogenesis. This phenomenon has been particularly well documented in pancreatic cancer, where detailed genetic studies and a robust mouse model have permitted investigators to test the role of various developmental signals in cancer progression. In this chapter, we review current knowledge regarding the signaling pathways that act during pancreatic development and the evidence that the reactivation of developmentally important signals is critical for the pathogenesis of this treatment-refractory malignancy.

RON (MST1R) is a novel prognostic marker and therapeutic target for gastroesophageal adenocarcinoma

RON (MST1R) is one of two members of the MET receptor tyrosine kinase family, along with parent receptor MET. RON has a putative role in several cancers, but its expression and function is poorly characterized in gastroesophageal adenocarcinoma. A recognized functional role of MET tyrosine kinase in gastroesophageal cancer has led to early phase clinical trials using MET inhibitors, with unimpressive results. Therefore, the role of RON in gastroesophageal cancer, as well as its role in cooperative signaling with MET and as a mechanism of resistance to MET inhibition, was studied in gastroesophageal tissues and cell lines. By IHC, RON was highly over-expressed in 74% of gastroesophageal samples (n=94), and over-expression was prognostic of poor survival (p=0.008); RON and MET co-expression occurred in 43% of samples and was prognostic of worst survival (p=0.03). High MST1R gene copy number by quantitative polymerase chain reaction, and confirmed by fluorescence in situ hybridization and/or array comparative genomic hybridization, was seen in 35.5% (16/45) of cases. High MST1R gene copy number correlated with poor survival (p=0.01), and was associated with high MET and ERBB2 gene copy number. A novel somatic MST1R juxtamembrane mutation R1018G was found in 11% of samples. RON signaling was functional in cell lines, activating downstream effector STAT3, and resulted in increased viability over controls. RON and MET co-stimulation assays led to enhanced malignant phenotypes over stimulation of either receptor alone. Growth inhibition as evidenced by viability and apoptosis assays was optimal using novel blocking monoclonal antibodies to both RON and MET, versus either alone. SU11274, a classic MET small molecule tyrosine kinase inhibitor, blocked signaling of both receptors, and proved synergistic when combined with STAT3 inhibition (combination index < 1). These preclinical studies define RON as an important novel prognostic marker and therapeutic target for gastroesophageal cancer warranting further investigation.

Deploying mouse models of pancreatic cancer for chemoprevention studies

With the advent of mouse models that recapitulate the cellular and molecular pathology of pancreatic neoplasia and cancer, it is now feasible to recruit and deploy these models for the evaluation of various chemopreventive and/or anticancer regimens. The highly lethal nature of pancreatic ductal adenocarcinoma (PDAC) makes multiple areas of research a priority, including assessment of compounds that prevent or suppress the development of early lesions that can transform into PDAC. Currently, there are over a dozen models available, which range from homogeneous preneoplastic lesions with remarkable similarity to human pancreatic intraepithelial neoplasms to models with a more heterogeneous population of lesions including cystic papillary and mucinous lesions. The molecular features of these models may also vary in a manner comparable with the differences observed in lesion morphology, and so, navigating the route of model selection is not trivial. Yet, arming the community of cancer investigators with a repertoire of models and the guidance to select relevant models that fit their research themes promises to produce findings that will have clinical relevance.

Expression of oncogenic K-ras and loss of Smad4 cooperate to induce the expression of EGFR and to promote invasion of immortalized human pancreas ductal cells

Activating mutation of K-ras and inactivation of DPC4 are two common genetic alterations that occur in the development and progression of pancreatic ductal adenocarcinomas (PDAC). A separate common event in PDAC progression is increased expression of phosphotyrosine kinase receptors (PTKRs). In our study, we examined whether activating mutations of K-ras and loss of Smad4 play a role in causing the aberrant expression of PTKRs. Immortalized human pancreas ductal cells (HPNE) were genetically modified by expressing oncogenic K-ras and/or by shRNA knockdown of Smad4. EGFR and erbB2 protein levels but not Ron or IGF-1R were substantially upregulated in HPNE cells that express K-ras((GD12)). The increased expression of EGFR in HPNE cells that expressed K-ras((GD12)) was mediated by both stabilizing EGFR protein and by increasing EGFR transcription. TGF-beta signaling partially suppressed K-ras((GD12)) induced EGFR transcription in Smad4 intact HPNE cells; whereas knockdown of Smad4 in cells expressing K-ras((GD12)) further enhanced expression of EGFR and erbB2. The upregulation of EGFR and erbB2 was associated with an increase of invasion, which was blocked by a kinase inhibitor of EGFR. Our study indicates for the first time, that oncogenic ras and loss of Smad signaling cooperate to upregulate EGFR and erbB2, which plays a role in promoting invasion.

Inhibition of STAT3 Tyr705 phosphorylation by Smad4 suppresses transforming growth factor beta-mediated invasion and metastasis in pancreatic cancer cells

The role of Smad4 in transforming growth factor beta (TGFbeta)-mediated epithelial-mesenchymal transition (EMT), invasion, and metastasis was investigated using isogenically matched pancreatic cancer cell lines that differed only in expression of Smad4. Cells expressing Smad4 showed an enhanced TGFbeta-mediated EMT as determined by increased expression of vimentin and decreased expression of beta-catenin and E-cadherin. TGFbeta-mediated invasion was suppressed in Smad4-intact cells as determined by in vitro assays, and these cells showed a reduced metastasis in an orthotopic model of pancreatic cancer. Interestingly, TGFbeta inhibited STAT3(Tyr705) phosphorylation in Smad4-intact cells. The decrease in STAT3(Tyr705) phosphorylation was linked to a TGFbeta/Smad4-dependent and enhanced activation of extracellular signal-regulated kinases, which caused an increase in serine phosphorylation of STAT3(Ser727). Down-regulating signal transducer and activator of transcription 3 (STAT3) expression by short hairpin RNA in Smad4-deficient cells prevented TGFbeta-induced invasion. Conversely, expressing a constitutively activated form of STAT3 (STAT3-C) in Smad4-intact cells enhanced invasion. This study indicates the requirement of STAT3 activity for TGFbeta-induced invasion in pancreatic cancer cells and implicates Smad4-dependent signaling in regulating STAT3 activity. These findings further suggest that loss of Smad4, leading to aberrant activation of STAT3, contributes to the switch of TGFbeta from a tumor-suppressive to a tumor-promoting pathway in pancreatic cancer.