c-Met is a marker of pancreatic cancer stem cells and therapeutic target

Roles of MET in human cancer

The MET proto-oncogene was first identified in osteosarcoma cells exposed to carcinogens. Although expressed in many normal cells, MET is overexpressed in many human cancers. MET is involved in the initiation and development of various human cancers and mediates proliferation, migration and invasion. Accordingly, MET has been successfully used as a biomarker for diagnosis and prognosis, survival, post-operative recurrence, risk assessment and pathologic grading, as well as a therapeutic target. In addition, recent work indicates that inhibition of MET expression and function has potential clinical benefit. This review summarizes the role, mechanism, and clinical significance of MET in the formation and development of human cancer.

Does GD2 synthase (GD2S) detect cancer stem cells in blood samples of breast carcinomas?

INTRODUCTION

Cancer stem cells (CSCs) are a theorized subset of cells within the tumor that is thought to drive disease recurrence and metastatic spread. The aim of this study is to investigate mRNA and protein levels of ganglioside GD2 synthase (GD2S), in breast cancer (BC) patients.

METHODS

65 PBMCs of preoperative BC patients without chemotherapy were compared to PBMCs after chemotherapy and controls.

RESULTS

GD2S were significantly higher in BC patients after chemotherapy compared to pre-chemotherapy at both mRNA and protein. GD2S was higher in pre-chemotherapy blood samples compared to control samples.

CONCLUSIONS

Higher expression of GD2S in BC samples compared to healthy control indicates the potential utility of GD2S as a marker of malignancy.

GLRX3, a novel cancer stem cell-related secretory biomarker of pancreatic ductal adenocarcinoma

Background

Cancer stem cells (CSCs) are implicated in carcinogenesis, cancer progression, and recurrence. Several biomarkers have been described for pancreatic ductal adenocarcinoma (PDAC) CSCs; however, their function and mechanism remain unclear.

Method

In this study, secretome analysis was performed in pancreatic CSC-enriched spheres and control adherent cells for biomarker discovery. Glutaredoxin3 (GLRX3), a novel candidate upregulated in spheres, was evaluated for its function and clinical implication.

Results

PDAC CSC populations, cell lines, patient tissues, and blood samples demonstrated GLRX3 overexpression. In contrast, GLRX3 silencing decreased the in vitro proliferation, migration, clonogenicity, and sphere formation of cells. GLRX3 knockdown also reduced tumor formation and growth in vivo. GLRX3 was found to regulate Met/PI3K/AKT signaling and stemness-related molecules. ELISA results indicated GLRX3 overexpression in the serum of patients with PDAC compared to that in healthy controls. The sensitivity and specificity of GLRX3 for PDAC diagnosis were 80.0 and 100%, respectively. When GLRX3 and CA19–9 were combined, sensitivity was significantly increased to 98.3% compared to that with GLRX3 or CA19–9 alone. High GLRX3 expression was also associated with poor disease-free survival in patients receiving curative surgery.

Conclusion

Overall, these results indicate GLRX3 as a novel diagnostic marker and therapeutic target for PDAC targeting CSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08898-y.

Dependence receptors: new targets for cancer therapy

Dependence receptors are known to promote survival and positive signaling such as proliferation, migration, and differentiation when activated, but to actively trigger apoptosis when unbound to their ligand. Their abnormal regulation was shown to be an important feature of tumorigenesis, allowing cancer cells to escape apoptosis triggered by these receptors while promoting in parallel major aspects of tumorigenesis such as proliferation, angiogenesis, invasiveness, and chemoresistance. This involvement in multiple cancer hallmarks has raised interest in dependence receptors as targets for cancer therapy. Although additional studies remain necessary to fully understand the complexity of signaling pathways activated by these receptors and to target them efficiently, it is now clear that dependence receptors represent very exciting targets for future cancer treatment. This manuscript reviews current knowledge on the contribution of dependence receptors to cancer and highlights the potential for therapies that activate pro-apoptotic functions of these proteins.

Epithelial to Mesenchymal Transition: Key Regulator of Pancreatic Ductal Adenocarcinoma Progression and Chemoresistance

Simple Summary

Pancreatic ductal adenocarcinoma’s (PDAC) dismal prognosis is associated with its aggressive biological behavior and resistance to chemotherapy. Epithelial to mesenchymal transition (EMT) has been recognized as a key driver of PDAC progression and development of drug resistance. EMT is a transient and reversible process leading to transdifferentiation of epithelial cells into a more mesenchymal phenotype. It is regulated by multiple signaling pathways that control the activity of a transcription factors network. Activation of EMT in pre-invasive stages of PDAC has been accused for early dissemination. Furthermore, it contributes to the development of intratumoral heterogeneity and drug resistance. This review summarizes the available data regarding signaling networks regulating EMT and describes the integral role of EMT in different aspects of PDAC pathogenesis.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies, characterized by aggressive biological behavior and a lack of response to currently available chemotherapy. Emerging evidence has identified epithelial to mesenchymal transition (EMT) as a key driver of PDAC progression and a central regulator in the development of drug resistance. EMT is a reversible transdifferentiation process controlled by complex interactions between multiple signaling pathways such as TGFb, Wnt, and Notch, which converge to a network of specific transcription factors. Activation of EMT transcriptional reprogramming converts cancer cells of epithelial differentiation into a more mesenchymal phenotypic state. EMT occurrence in pre-invasive pancreatic lesions has been implicated in early PDAC dissemination. Moreover, cancer cell phenotypic plasticity driven by EMT contributes to intratumoral heterogeneity and drug tolerance and is mechanistically associated with the emergence of cells exhibiting cancer stem cells (CSCs) phenotype. In this review we summarize the available data on the signaling cascades regulating EMT and the molecular isnteractions between pancreatic cancer and stromal cells that activate them. In addition, we provide a link between EMT, tumor progression, and chemoresistance in PDAC.

Marker-free lineage tracing reveals an environment-instructed clonogenic hierarchy in pancreatic cancer

Effective treatments for pancreatic ductal adenocarcinoma (PDAC) are lacking, and targeted agents have demonstrated limited efficacy. It has been speculated that a rare population of cancer stem cells (CSCs) drives growth, therapy resistance, and rapid metastatic progression in PDAC. These CSCs demonstrate high clonogenicity in vitro and tumorigenic potential in vivo. However, their relevance in established PDAC tissue has not been determined. Here, we use marker-independent stochastic clonal labeling, combined with quantitative modeling of tumor expansion, to uncover PDAC tissue growth dynamics. We find that in contrast to the CSC model, all PDAC cells display clonogenic potential in situ. Furthermore, the proximity to activated cancer-associated fibroblasts determines tumor cell clonogenicity. This means that the microenvironment is dominant in defining the clonogenic activity of PDAC cells. Indeed, manipulating the stroma by Hedgehog pathway inhibition alters the tumor growth mode, revealing that tumor-stroma crosstalk shapes tumor growth dynamics and clonal architecture.

Single-cell RNA-seq reveals invasive trajectory and determines cancer stem cell-related prognostic genes in pancreatic cancer

Pancreatic duct adenocarcinoma (PDAC) is an aggressive and lethal malignancy. Pancreatic cancer stem cells (PCSCs) are assumed to contribute to the initiation and invasion of PDAC. In this study, we performed single-cell RNA sequencing (scRNA-seq) analysis of PDAC tumor samples from patients and control pancreas tissues to reveal the transformation process of cancer stem cell (CSC)-like ductal cells into ductal cells with invasive potential and we screened out CSC-related genes (CRGs). Subsequently, we applied LASSO and Cox regression models to identify five CRGs with potential prognostic values and constructed a risk prognostic model using the Cancer Genome Atlas datasets. The risk models were verified using Gene Expression Omnibus datasets. Patients in the high-risk group had a significantly poor overall survival (Pvalue<0.0001), as illustrated by the Kaplan-Meier survival curve, and the area under the curve confirmed the accuracy of predictions by our risk model. Tumor mutation burden variations were used to further explore the differences between the two risk cohorts. In addition, the Human Protein Atlas was used to investigate the protein expression of five hub CRGs. In brief, we utilized scRNA-seq to reveal the invasive trajectory of ductal cells and identified crucial CRGs in PDAC, which may help predict patient survival and provide potential clinical therapeutic targets against CSCs.

The plasticity of pancreatic cancer stem cells: implications in therapeutic resistance

The ever-growing perception of cancer stem cells (CSCs) as a plastic state rather than a hardwired defined entity has evolved our understanding of the functional and biological plasticity of these elusive components in malignancies. Pancreatic cancer (PC), based on its biological features and clinical evolution, is a prototypical example of a CSC-driven disease. Since the discovery of pancreatic CSCs (PCSCs) in 2007, evidence has unraveled their control over many facets of the natural history of PC, including primary tumor growth, metastatic progression, disease recurrence, and acquired drug resistance. Consequently, the current near-ubiquitous treatment regimens for PC using aggressive cytotoxic agents, aimed at ‘‘tumor debulking’’ rather than eradication of CSCs, have proven ineffective in providing clinically convincing improvements in patients with this dreadful disease. Herein, we review the key hallmarks as well as the intrinsic and extrinsic resistance mechanisms of CSCs that mediate treatment failure in PC and enlist the potential CSC-targeting ‘natural agents’ that are gaining popularity in recent years. A better understanding of the molecular and functional landscape of PCSC-intrinsic evasion of chemotherapeutic drugs offers a facile opportunity for treating PC, an intractable cancer with a grim prognosis and in dire need of effective therapeutic advances.

Inhibition of c-MET reverses radiation-induced malignant potential in pancreatic cancer

As a treatment option for PDAC, radiation therapy induces good local control. However, radiation also reportedly enhances the malignant potential (e.g., invasion and migration ability) in various cancers, thus increasing the risk of distant metastasis. It remains unclear how radiation induces malignant potential, and how such enhanced malignant potential can be suppressed. In the current study, we evaluated the sequential change of c-Met expression in pancreatic cancer cells following irradiation. We found that irradiation transiently induced c-Met expression in vitro. In an in vivo subcutaneous tumor mouse model, irradiation also enhanced downstream phosphorylated Met (p-Met). Furthermore, this enhancement of p-Met protein expression was suppressed by oral administration of the c-Met inhibitor INC280. Irradiated pancreatic cancer cells with enhanced c-Met expression exhibited higher malignant potential, including invasion and migration ability, compared with cells showing low c-Met expression. Pancreatic cancer cells that overexpressed c-met also showed enhanced malignant potential, which was reversed by c-Met inhibition. Additionally, c-Met inhibitor suppressed the metastatic potential in a liver metastasis mouse model using c-met-overexpressing cells. Overall, our present results revealed that irradiation could induce c-met expression in pancreatic cancer cells, leading to enhanced malignant potential (e.g., invasion and migration ability) and thus promoting distant metastasis. Moreover, a c-Met inhibitor could reverse this enhanced malignant potential.

Fraction B From Catfish Epidermal Secretions Kills Pancreatic Cancer Cells, Inhibits CD44 Expression and Stemness, and Alters Cancer Cell Metabolism

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer related death in western countries. The successful treatment of PDAC remains limited. We investigated the effect of Fraction B, which is a fraction purified from catfish (Arius bilineatus, Val.) skin secretions containing proteins and lipids, on PDAC biology both in-vivo and in-vitro. We report here that Fraction B potently suppressed the proliferation of both human and mouse pancreatic cancer cells in vitro and significantly reduced the growth of their relevant xenograft (Panc02) and orthotopic tumors (human Panc-1 cells) (p < 0.05). The Reverse Phase Protein Array (RPPA) data obtained from the tumor tissues derived from orthotopic tumor bearing mice treated with Fraction B showed that Fraction B altered the cancer stem cells related pathways and regulated glucose and glutamine metabolism. The down-regulation of the cancer stem cell marker CD44 expression was further confirmed in Panc-1 cells. CBC and blood chemistry analyses showed no systemic toxicity in Fraction B treated Panc-1 tumor bearing mice compared to that of control group. Our data support that Fraction B is a potential candidate for PDAC treatment.

Cancer stem cell-targeted chimeric antigen receptor (CAR)-T cell therapy: Challenges and prospects

Cancer stem cells (CSCs) with their self-renewal ability are accepted as cells which initiate tumors. CSCs are regarded as interesting targets for novel anticancer therapeutic agents because of their association with tumor recurrence and resistance to conventional therapies, including radiotherapy and chemotherapy. Chimeric antigen receptor (CAR)-T cells are engineered T cells which express an artificial receptor specific for tumor associated antigens (TAAs) by which they accurately target and kill cancer cells. In recent years, CAR-T cell therapy has shown more efficiency in cancer treatment, particularly regarding blood cancers. The expression of specific markers such as TAAs on CSCs in varied cancer types makes them as potent tools for CAR-T cell therapy. Here we review the CSC markers that have been previously targeted with CAR-T cells, as well as the CSC markers that may be used as possible targets for CAR-T cell therapy in the future. Furthermore, we will detail the most important obstacles against CAR-T cell therapy and suggest solutions.

Stem Cells in the Exocrine Pancreas during Homeostasis, Injury, and Cancer

Simple Summary

Pancreatic cancer is one of the most lethal malignancies. Hence, improved therapies are urgently needed. Recent research indicates that pancreatic cancers depend on cancer stem cells (CSCs) for tumor expansion, metastasis, and therapy resistance. However, the exact functionality of pancreatic CSCs is still unclear. CSCs have much in common with normal pancreatic stem cells that have been better, albeit still incompletely, characterized. In this literature review, we address how pancreatic stem cells influence growth, homeostasis, regeneration, and cancer. Furthermore, we outline which intrinsic and extrinsic factors regulate stem cell functionality during these different processes to explore potential novel targets for treating pancreatic cancer.

Abstract

Cell generation and renewal are essential processes to develop, maintain, and regenerate tissues. New cells can be generated from immature cell types, such as stem-like cells, or originate from more differentiated pre-existing cells that self-renew or transdifferentiate. The adult pancreas is a dormant organ with limited regeneration capacity, which complicates studying these processes. As a result, there is still discussion about the existence of stem cells in the adult pancreas. Interestingly, in contrast to the classical stem cell concept, stem cell properties seem to be plastic, and, in circumstances of injury, differentiated cells can revert back to a more immature cellular state. Importantly, deregulation of the balance between cellular proliferation and differentiation can lead to disease initiation, in particular to cancer formation. Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with a 5-year survival rate of only ~9%. Unfortunately, metastasis formation often occurs prior to diagnosis, and most tumors are resistant to current treatment strategies. It has been proposed that a specific subpopulation of cells, i.e., cancer stem cells (CSCs), are responsible for tumor expansion, metastasis formation, and therapy resistance. Understanding the underlying mechanisms of pancreatic stem cells during homeostasis and injury might lead to new insights to understand the role of CSCs in PDAC. Therefore, in this review, we present an overview of the current literature regarding the stem cell dynamics in the pancreas during health and disease. Furthermore, we highlight the influence of the tumor microenvironment on the growth behavior of PDAC.

Integrated Analysis of Microarray and RNA-Seq Data for the Identification of Hub Genes and Networks Involved in the Pancreatic Cancer

Pancreatic cancer (PaCa) is the seventh most fatal malignancy, with more than 90% mortality rate within the first year of diagnosis. Its treatment can be improved the identification of specific therapeutic targets and their relevant pathways. Therefore, the objective of this study is to identify cancer specific biomarkers, therapeutic targets, and their associated pathways involved in the PaCa progression. RNA-seq and microarray datasets were obtained from public repositories such as the European Bioinformatics Institute (EBI) and Gene Expression Omnibus (GEO) databases. Differential gene expression (DE) analysis of data was performed to identify significant differentially expressed genes (DEGs) in PaCa cells in comparison to the normal cells. Gene co-expression network analysis was performed to identify the modules co-expressed genes, which are strongly associated with PaCa and as well as the identification of hub genes in the modules. The key underlaying pathways were obtained from the enrichment analysis of hub genes and studied in the context of PaCa progression. The significant pathways, hub genes, and their expression profile were validated against The Cancer Genome Atlas (TCGA) data, and key biomarkers and therapeutic targets with hub genes were determined. Important hub genes identified included ITGA1, ITGA2, ITGB1, ITGB3, MET, LAMB1, VEGFA, PTK2, and TGFβ1. Enrichment analysis characterizes the involvement of hub genes in multiple pathways. Important ones that are determined are ECM–receptor interaction and focal adhesion pathways. The interaction of overexpressed surface proteins of these pathways with extracellular molecules initiates multiple signaling cascades including stress fiber and lamellipodia formation, PI3K-Akt, MAPK, JAK/STAT, and Wnt signaling pathways. Identified biomarkers may have a strong influence on the PaCa early stage development and progression. Further, analysis of these pathways and hub genes can help in the identification of putative therapeutic targets and development of effective therapies for PaCa.

The Role of lncRNAs in the Stem Phenotype of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma is one of the deadliest tumors. This neoplasia is characterized by an important cellular and phenotypic heterogeneity. In particular, it has been shown that at least two subtypes can be found: basal-like, which presents stem-like properties, and classical. Cancer stem cells have been isolated and characterized from these tumors, showing their dependance on general and tissue-specific stem transcription factors and signaling pathways. Nevertheless, little is known about their tissue microenvironment and cell non-autonomous regulators, such as long-non-coding RNAs. (lncRNAs). In this review, we summarize the current knowledge about the positive and negative effects of lncRNAs in the stemness phenotype of pancreatic ductal adenocarcinoma cancer (PDAC).

Overcoming the Tumor Microenvironmental Barriers of Pancreatic Ductal Adenocarcinomas for Achieving Better Treatment Outcomes

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with the lowest survival rate among all solid tumors. The lethality of PDAC arises from late detection and propensity of the tumor to metastasize and develop resistance against chemo and radiation therapy. A highly complex tumor microenvironment composed of dense stroma, immune cells, fibroblast, and disorganized blood vessels, is the main obstacle to current PDAC therapy. Despite the tremendous success of immune checkpoint inhibitors (ICIs) in cancers, PDAC remains one of the poorest responders of ICIs therapy. The immunologically "cold" phenotype of PDAC is attributed to the low mutational burden, high infiltration of myeloid-derived suppressor cells and T-regs, contributing to a significant immunotherapy resistance mechanism. Thus, the development of innovative strategies for turning immunologically "cold" tumor into "hot" ones is an unmet need to improve the outcome of PDAC ICIs therapies. Other smart strategies, such as nanomedicines, sonic Hedgehog inhibitor, or smoothened inhibitor, are discussed to enhance chemotherapeutic agents' efficiency by disrupting the PDAC stroma. This review highlights the current challenges and various preclinical and clinical strategies to overcome current PDAC therapy difficulties, thus significantly advancing PDAC research knowledge.

Pancreatic Cancer and Therapy: Role and Regulation of Cancer Stem Cells

Despite significant improvements in clinical management, pancreatic cancer (PC) remains one of the deadliest cancer types, as it is prone to late detection with extreme metastatic properties. The recent findings that pancreatic cancer stem cells (PaCSCs) contribute to the tumorigenesis, progression, and chemoresistance have offered significant insight into the cancer malignancy and development of precise therapies. However, the heterogeneity of cancer and signaling pathways that regulate PC have posed limitations in the effective targeting of the PaCSCs. In this regard, the role for K-RAS, TP53, Transforming Growth Factor-β, hedgehog, Wnt and Notch and other signaling pathways in PC progression is well documented. In this review, we discuss the role of PaCSCs, the underlying molecular and signaling pathways that help promote pancreatic cancer development and metastasis with a specific focus on the regulation of PaCSCs. We also discuss the therapeutic approaches that target different PaCSCs, intricate mechanisms, and therapeutic opportunities to eliminate heterogeneous PaCSCs populations in pancreatic cancer.

Co-dependency for MET and FGFR1 in basal triple-negative breast cancers

Triple-negative breast cancer (TNBC) is a heterogeneous disease that lacks both effective patient stratification strategies and therapeutic targets. Whilst elevated levels of the MET receptor tyrosine kinase are associated with TNBCs and predict poor clinical outcome, the functional role of MET in TNBC is still poorly understood. In this study, we utilise an established Met-dependent transgenic mouse model of TNBC, human cell lines and patient-derived xenografts to investigate the role of MET in TNBC tumorigenesis. We find that in TNBCs with mesenchymal signatures, MET participates in a compensatory interplay with FGFR1 to regulate tumour-initiating cells (TICs). We demonstrate a requirement for the scaffold protein FRS2 downstream from both Met and FGFR1 and find that dual inhibition of MET and FGFR1 signalling results in TIC depletion, hindering tumour progression. Importantly, basal breast cancers that display elevated MET and FGFR1 signatures are associated with poor relapse-free survival. Our results support a role for MET and FGFR1 as potential co-targets for anti-TIC therapies in TNBC.

NOGEA: A Network-oriented Gene Entropy Approach for Dissecting Disease Comorbidity and Drug Repositioning

Rapid development of high-throughput technologies has permitted the identification of an increasing number of disease-associated genes (DAGs), which are important for understanding disease initiation and developing precision therapeutics. However, DAGs often contain large amounts of redundant or false positive information, leading to difficulties in quantifying and prioritizing potential relationships between these DAGs and human diseases. In this study, a network-oriented gene entropy approach (NOGEA) is proposed for accurately inferring master genes that contribute to specific diseases by quantitatively calculating their perturbation abilities on directed disease-specific gene networks. In addition, we confirmed that the master genes identified by NOGEA have a high reliability for predicting disease-specific initiation events and progression risk. Master genes may also be used to extract the underlying information of different diseases, thus revealing mechanisms of disease comorbidity. More importantly, approved therapeutic targets are topologically localized in a small neighborhood of master genes on the interactome network, which provides a new way for predicting drug-disease associations. Through this method, 11 old drugs were newly identified and predicted to be effective for treating pancreatic cancer and then validated by in vitro experiments. Collectively, the NOGEA was useful for identifying master genes that control disease initiation and co-occurrence, thus providing a valuable strategy for drug efficacy screening and repositioning. NOGEA codes are publicly available at https://github.com/guozihuaa/NOGEA.

TGFB1/INHBA Homodimer/Nodal-SMAD2/3 Signaling Network: A Pivotal Molecular Target in PDAC Treatment

Pancreatic cancer remains a grueling disease that is projected to become the second-deadliest cancer in the next decade. Standard treatment of pancreatic cancer is chemotherapy, which mainly targets the differentiated population of tumor cells; however, it paradoxically sets the roots of tumor relapse by the selective enrichment of intrinsically chemoresistant pancreatic cancer stem cells that are equipped with an indefinite capacity for self-renewal and differentiation, resulting in tumor regeneration and an overall anemic response to chemotherapy. Crosstalk between pancreatic tumor cells and the surrounding stromal microenvironment is also involved in the development of chemoresistance by creating a supportive niche, which enhances the stemness features and tumorigenicity of pancreatic cancer cells. In addition, the desmoplastic nature of the tumor-associated stroma acts as a physical barrier, which limits the intratumoral delivery of chemotherapeutics. In this review, we mainly focus on the transforming growth factor beta 1 (TGFB1)/inhibin subunit beta A (INHBA) homodimer/Nodal-SMAD2/3 signaling network in pancreatic cancer as a pivotal central node that regulates multiple key mechanisms involved in the development of chemoresistance, including enhancement of the stem cell-like properties and tumorigenicity of pancreatic cancer cells, mediating cooperative interactions between pancreatic cancer cells and the surrounding stroma, as well as regulating the deposition of extracellular matrix proteins within the tumor microenvironment.

Targeting cancer stem cells for reversing therapy resistance: mechanism, signaling, and prospective agents

Cancer stem cells (CSCs) show a self-renewal capacity and differentiation potential that contribute to tumor progression and therapy resistance. However, the underlying processes are still unclear. Elucidation of the key hallmarks and resistance mechanisms of CSCs may help improve patient outcomes and reduce relapse by altering therapeutic regimens. Here, we reviewed the identification of CSCs, the intrinsic and extrinsic mechanisms of therapy resistance in CSCs, the signaling pathways of CSCs that mediate treatment failure, and potential CSC-targeting agents in various tumors from the clinical perspective. Targeting the mechanisms and pathways described here might contribute to further drug discovery and therapy.

Roles of microRNAs in Gastrointestinal Cancer Stem Cell Resistance and Therapeutic Development

Resistance to cancer treatment is one of the major challenges currently faced when treating gastrointestinal (GI) cancers. A major contributing factor to this resistance is the presence of cancer stem cells (CSCs) in GI cancers (e.g., colorectal, pancreatic, gastric, liver cancer). Non-coding RNAs, such as microRNAs (miRNAs), have been found to regulate several key targets that are responsible for cancer stemness, and function as oncogenic miRNAs (oncomiRs) or tumor suppressor miRNAs. As a result, several miRNAs have been found to alter, or be altered by, the expression of CSC-defining markers and their related pathways. These miRNAs can be utilized to affect stemness in multiple ways, including directly targeting CSCs and enhancing the efficacy of cancer therapeutics. This review highlights current studies regarding the roles of miRNAs in GI CSCs, and efforts towards the development of cancer therapeutics.

Dysregulation of mitophagy and mitochondrial homeostasis in cancer stem cells: Novel mechanism for anti-cancer stem cell-targeted cancer therapy

Despite the potential of cancer medicine, cancer stem cells (CSCs) associated with chemoresistance and disease recurrence are the significant challenges currently opposing the efficacy of available cancer treatment options. Mitochondrial dynamics involving the fission-fusion cycle and mitophagy are the major contributing factors to better adaptation, enabling CSCs to survive and grow better under tumour micro-environment-associated stress. Moreover, mitophagy is balanced with mitochondrial biogenesis to maintain mitochondrial homeostasis in CSCs, which are necessary for the growth and maintenance of CSCs and regulate metabolic switching from glycolysis to oxidative phosphorylation. In this review, we discuss different aspects of mitochondrial dynamics, mitophagy, and mitochondrial homeostasis and their effects on modulating CSCs behaviour during cancer development. Moreover, the efficacy of pharmacological targeting of these cellular processes using anti-CSC drugs in combination with currently available chemotherapeutic drugs improves the patient's survival of aggressive cancer types.

Exploring the significance of novel immune-related gene signatures in the prognosis and immune features of pancreatic adenocarcinoma

BACKGROUND

Immune-related genes (IRGs) are associated with the prognosis of different cancers and are helpful for the diagnosis and management of systematic treatment for cancer patients. However, there have been a few corresponding studies in pancreatic adenocarcinoma (PAAD).

METHODS

The data of PAAD patients were obtained from the TCGA, GEO, and ICGC databases. Additionally, the expression profiles of the normal pancreas from the GTEx database were used to screen differentially expressed immune-related genes (DEIRGs). Cox regression analyses were used to explore overall survival (OS)- and progression-free survival (PFS)-related DEIRGs and to establish two nomograms for PAAD prognosis. Finally, transcription factor (TF), immune infiltration, and unsupervised consensus analyses were performed to understand the potential mechanisms.

RESULTS

An OS-prognostic signature based on seven DEIRGs and a PFS-prognostic signature based on seven DEIRGs were generated, and their robust prognostic ability was confirmed by ROC curves (OS: 0.736 ~ 0.774, PFS: 0.732 ~ 0.840). According to the risk score, the OS and PFS of the high-risk group were poorer than those of the low-risk group in the training set and four external validation sets. In addition, two nomograms based on the signatures and clinical variables also showed excellent discrimination. And two hub regulatory pathways were successfully validated in several independent datasets. Discernable patterns of DEIRGs in unsupervised consensus analysis showed that patients with low expression of immune checkpoints had a favorable prognosis.

CONCLUSION

Two DEIRG-based signatures can be used as independent tools for the prognostic prediction of PAAD and to provide potential novel immunotherapy targets.

Targeting hypoxic tumor microenvironment in pancreatic cancer

Attributable to its late diagnosis, early metastasis, and poor prognosis, pancreatic cancer remains one of the most lethal diseases worldwide. Unlike other solid tumors, pancreatic cancer harbors ample stromal cells and abundant extracellular matrix but lacks vascularization, resulting in persistent and severe hypoxia within the tumor. Hypoxic microenvironment has extensive effects on biological behaviors or malignant phenotypes of pancreatic cancer, including metabolic reprogramming, cancer stemness, invasion and metastasis, and pathological angiogenesis, which synergistically contribute to development and therapeutic resistance of pancreatic cancer. Through various mechanisms including but not confined to maintenance of redox homeostasis, activation of autophagy, epigenetic regulation, and those induced by hypoxia-inducible factors, intratumoral hypoxia drives the above biological processes in pancreatic cancer. Recognizing the pivotal roles of hypoxia in pancreatic cancer progression and therapies, hypoxia-based antitumoral strategies have been continuously developed over the recent years, some of which have been applied in clinical trials to evaluate their efficacy and safety in combinatory therapies for patients with pancreatic cancer. In this review, we discuss the molecular mechanisms underlying hypoxia-induced aggressive and therapeutically resistant phenotypes in both pancreatic cancerous and stromal cells. Additionally, we focus more on innovative therapies targeting the tumor hypoxic microenvironment itself, which hold great potential to overcome the resistance to chemotherapy and radiotherapy and to enhance antitumor efficacy and reduce toxicity to normal tissues.

The role of MET in chemotherapy resistance

Chemotherapy remains the mainstay of treatment in the majority of solid and haematological malignancies. Resistance to cytotoxic chemotherapy is a major clinical problem and substantial research is ongoing into potential methods of overcoming this resistance. One major target, the receptor tyrosine kinase MET, has generated increasing interest with multiple clinical trials in progress. Overexpression of MET is frequently observed in a range of different cancers and is associated with poor prognosis. Studies have shown that MET promotes resistance to targeted therapies, including those targeting EGFR, BRAF and MEK. More recently, several reports suggest that MET also contributes to cytotoxic chemotherapy resistance. Here we review the preclinical evidence of MET's role in chemotherapy resistance, the mechanisms by which this resistance is mediated and the translational relevance of MET inhibitor therapy for patients with chemotherapy resistant disease.

Cancer Stem Cell Microenvironment Models with Biomaterial Scaffolds In Vitro

Defined by its potential for self-renewal, differentiation and tumorigenicity, cancer stem cells (CSCs) are considered responsible for drug resistance and relapse. To understand the behavior of CSC, the effects of the microenvironment in each tissue are a matter of great concerns for scientists in cancer biology. However, there are many complicated obstacles in the mimicking the microenvironment of CSCs even with current advanced technology. In this context, novel biomaterials have widely been assessed as in vitro platforms for their ability to mimic cancer microenvironment. These efforts should be successful to identify and characterize various CSCs specific in each type of cancer. Therefore, extracellular matrix scaffolds made of biomaterial will modulate the interactions and facilitate the investigation of CSC associated with biological phenomena simplifying the complexity of the microenvironment. In this review, we summarize latest advances in biomaterial scaffolds, which are exploited to mimic CSC microenvironment, and their chemical and biological requirements with discussion. The discussion includes the possible effects on both cells in tumors and microenvironment to propose what the critical factors are in controlling the CSC microenvironment focusing the future investigation. Our insights on their availability in drug screening will also follow the discussion.

Targeting HGF/c-MET Axis in Pancreatic Cancer

Pancreatic cancer (pancreatic ductal adenocarcinoma (PDAC/PC)) has been an aggressive disease that is associated with early metastases. It is characterized by dense and collagenous desmoplasia/stroma, predominantly produced by pancreatic stellate cells (PSCs). PSCs interact with cancer cells as well as other stromal cells, facilitating disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells and endothelial cells. The current review discusses the role of the MET/HGF axis in tumour progression and dissemination of pancreatic cancer. Therapeutic approaches that were developed targeting either the ligand (HGF) or the receptor (c-MET) have not been shown to translate well into clinical settings. We discuss a two-pronged approach of targeting both the components of this pathway to interrupt the stromal-tumour interactions, which may represent a potential therapeutic strategy to improve outcomes in PC.

Cancer Stem Cell Niche in Colorectal Cancer and Targeted Therapies

Cancer stem cells (CSCs), also known as tumor-initiating cells, are a sub-population of tumor cells found in many human cancers that are endowed with self-renewal and pluripotency. CSCs may be more resistant to conventional anticancer therapies than average cancer cells, as they can easily escape the cytotoxic effects of standard chemotherapy, thereby resulting in tumor relapse. Despite significant progress in related research, effective elimination of CSCs remains an unmet clinical need. CSCs are localized in a specialized microenvironment termed the niche, which plays a pivotal role in cancer multidrug resistance. The niche components of CSCs, such as the extracellular matrix, also physically shelter CSCs from therapeutic agents. Colorectal cancer is the most common malignancy worldwide and presents a relatively transparent process of cancer initiation and development, making it an ideal model for CSC niche research. Here, we review recent advances in the field of CSCs using colorectal cancer as an example to illustrate the potential therapeutic value of targeting the CSC niche. These findings not only provide a novel theoretical basis for in-depth discussions on tumor occurrence, development, and prognosis evaluation, but also offer new strategies for the targeted treatment of cancer.

Cathepsin B is highly expressed in pancreatic cancer stem-like cells and is associated with patients' surgical outcomes

Cancer stem-like cells (CSLCs) in solid tumors are resistant to conventional chemotherapy and molecularly targeted therapy, which is thought to contribute to cancer recurrence and metastasis. The present study aimed to identify biomarkers for pancreatic CSLCs (P-CSLCs). Using our previously reported methods, P-CSLC-enriched populations were generated from pancreatic cancer cell lines. The protein expression profiles of these populations were compared with those of parental cells using two-dimensional electrophoresis, tandem mass spectrometry, flow cytometry and immunohistochemistry. Protein expression in surgical specimens was also evaluated for relationships with clinical outcomes. A lysosomal cysteine protease, cathepsin B (CTSB), was significantly upregulated in P-CSLCs compared with that in the parental cells, as shown using western blotting. Flow cytometry analysis also confirmed that CTSB was more highly expressed on the surface of P-CSLCs compared with that on parental cells. Moreover, PCLCs had elevated cellular secretions of CTSB compared with the parental cells. Finally, CTSB expression was evaluated in 69 resected tumor specimens, and high expression was associated with the patients' clinicopathological features and surgical outcomes. The present results suggested that CTSB is a biomarker for poor survival in patients with pancreatic cancer, which is possibly associated with P-CSLCs. This novel biomarker may also have potential as a therapeutic target.

In silico identification of therapeutic compounds against microRNA targets in drug-resistant pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a major health issue that has been eluding efforts to identify viable therapeutic treatment options. Besides having the lowest survival rate among all types of cancer, almost all conventional methods of treatment are futile against this condition, leaving patients to succumb to this ailment faster than ever. As it is increasingly becoming difficult to come up with new compounds for the treatment of various diseases, alternative solutions are required for tackling these problems. In this study, publically available miRNA and gene expression data were used to identify common elements that were present in gemcitabine-resistant PDAC cell lines. By selecting overexpressed genes involved in pancreatic cancer and cancer pathways in general, potential drug candidates for the treatment of PDAC were identified. In this study, 21 differentially expressed miRNAs were identified from PANC-1 cell line treated with gemcitabine. Pathway analysis revealed that MET and PPARG were overexpressed in cancer-related pathways, including pancreatic cancer, and could be targeted for PDAC treatment. Using CMap, fisetin was identified a likely candidate drug for the treatment of PDAC. Docking studies indicated that fisetin was bound to c-Met and PPARG with an XP G score of -12.819 and -7.021 kcal/mol, respectively. As miRNAs have increasingly been shown to part take in important cancer-related processes and pathways, researching drug development methods based on miRNA targets could be beneficial for pharmaceutical industries. Communicated by Ramaswamy H. Sarma.

HGF/c-Met Promote Renal Carcinoma Cancer Stem Cells Enrichment Through Upregulation of Cir-CCDC66

Increasing studies have suggested that circular RNAs play an important function in the process of numerous cancers. We aimed to investigate the possible role of cir-CCDC66 in renal carcinoma cancer. As cancer stem cells are responsible for the renal carcinoma cancer tumor growth and resistance to conventional therapy, we focus on the cir-CCDC66 influence on renal carcinoma cancer stem cells. In this study, we performed experiments in human renal tubular epithelial cell HK2 cells and several renal carcinoma cancer cancer cell lines. The results showed that cir-CCDC66 was upregulated not only in renal carcinoma cancer cancer cell lines but also in cancer stem cell spheres. What's more, the results showed that cir-CCDC66 enhanced the cancer stem cell enrichment. Further mechanistic studies showed that hepatocyte growth factor/c-Met pathway was activated in cancer stem cell enrichment and responsible for the cir-CCDC66 upregulation. Inhibition of hepatocyte growth factor/c-Met could block cir-CCDC66-induced cancer stem cell enrichment. In conclusion, our research revealed a novel mechanism between hepatocyte growth factor/c-Met/cir-CCDC66 and cancer stem cell enrichment. We verified that cir-CCDC66 could be a promising biomarker and therapy target for renal carcinoma cancer treatment.

Proteins and Molecular Pathways Relevant for the Malignant Properties of Tumor-Initiating Pancreatic Cancer Cells

Cancer stem cells (CSCs), a small subset of the tumor bulk with highly malignant properties, are deemed responsible for tumor initiation, growth, metastasis, and relapse. In order to reveal molecular markers and determinants of their tumor-initiating properties, we enriched rare stem-like pancreatic tumor-initiating cells (TICs) by harnessing their clonogenic growth capacity in three-dimensional multicellular spheroid cultures. We compared pancreatic TICs isolated from three-dimensional tumor spheroid cultures with nontumor-initiating cells (non-TICs) enriched in planar cultures. Employing differential proteomics (PTX), we identified more than 400 proteins with significantly different expression in pancreatic TICs and the non-TIC population. By combining the unbiased PTX with mRNA expression analysis and literature-based predictions of pro-malignant functions, we nominated the two calcium-binding proteins S100A8 (MRP8) and S100A9 (MRP14) as well as galactin-3-binding protein LGALS3BP (MAC-2-BP) as putative determinants of pancreatic TICs. In silico pathway analysis followed by candidate-based RNA interference mediated loss-of-function analysis revealed a critical role of S100A8, S100A9, and LGALS3BP as molecular determinants of TIC proliferation, migration, and in vivo tumor growth. Our study highlights the power of combining unbiased proteomics with focused gene expression and functional analyses for the identification of novel key regulators of TICs, an approach that warrants further application to identify proteins and pathways amenable to drug targeting.

Cabozantinib Inhibits Photodynamic Therapy-Induced Auto- and Paracrine MET Signaling in Heterotypic Pancreatic Microtumors

Extensive desmoplasia is a hallmark of pancreatic ductal adenocarcinoma (PDAC), which frequently associates with treatment resistance. Recent findings indicate that a combination of photodynamic therapy and the multi-kinase inhibitor cabozantinib achieved local tumor control and a significant decrease in tumor metastases in preclinical PDAC models, but the underlying therapeutic mechanisms remain unclear. This study elucidates the molecular basis of this multi-agent regimen, focusing on the role of MET signaling. Since MET activation stems from its interaction with hepatocyte growth factor (HGF), which is typically secreted by fibroblasts, we developed heterotypic PDAC microtumor models that recapitulate these interactions. In these models, MET signaling can be constitutively activated through paracrine and autocrine mechanisms. Photodynamic therapy caused significant elevations in HGF secretion by fibroblasts, suggesting it plays a complex role in the modulation of the paracrine HGF–MET signaling cascade in desmoplastic tumors. Blocking MET phosphorylation with adjuvant cabozantinib caused a significant improvement in photodynamic therapy efficacy, most notably by elevating spheroid necrosis at low radiant exposures. These findings highlight that adjuvant photodynamic therapy can augment chemotherapy efficacies, and potentially achieve improved management of desmoplastic PDAC in a more tolerable manner.

Targeted Dual Intervention-Oriented Drug-Encapsulated (DIODE) Nanoformulations for Improved Treatment of Pancreatic Cancer

Despite recent advancements, effective treatment for pancreatic ductal adenocarcinoma (PDAC) has remained elusive. The overall survival rate in PDAC patients has been dismally low due to resistance to standard therapies. In fact, the failure of monotherapies to provide long-term survival benefits in patients led to ascension of several combination therapies for PDAC treatment. However, these combination therapies provided modest survival improvements while increasing treatment-related adverse side effects. Hence, recent developments in drug delivery methods hold the potential for enhancing therapeutic benefits by offering cocktail drug loading and minimizing chemotherapy-associated side effects. Nanoformulations-aided deliveries of anticancer agents have been a success in recent years. Yet, improving the tumor-targeted delivery of drugs to PDAC remains a major hurdle. In the present paper, we developed several new tumor-targeted dual intervention-oriented drug-encapsulated (DIODE) liposomes. We successfully formulated liposomes loaded with gemcitabine (G), paclitaxel (P), erlotinib (E), XL-184 (c-Met inhibitor, X), and their combinations (GP, GE, and GX) and evaluated their in vitro and in vivo efficacies. Our novel DIODE liposomal formulations improved median survival in comparison with gemcitabine-loaded liposomes or vehicle. Our findings are suggestive of the importance of the targeted delivery for combination therapies in improving pancreatic cancer treatment.

Significance of Expression of Cancer Stem Cell Markers CD133 and Nestin in Pancreatic Intraepithelial Carcinoma-invasive Adenocarcinoma Sequence

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies and one of the most leading causes of cancer related deaths. It has a very poor prognosis with high recurrence rate. We investigated the expression of CSC markers (CD133 and nestin) in 100 patients [30 pancreatic intraepithelial tumor cases (PanIN) and 70 PDAC cases] and correlate the expression levels of these markers with clinicopathological data with the aid of Ki67 expression. Our findings showed that both cancer stem markers are related to the grade, stage, metastasis of PDAC and to the grade of PanIN cases and revealed that both markers are associated with PanIN-PDAC sequence with inverse relation between them. Both markers may contribute to proliferation, differentiation, invasiveness, and histologic types of PDAC. Sothey may also be useful for developing new therapeutic modalities for PDAC.

SOX13 promotes colorectal cancer metastasis by transactivating SNAI2 and c-MET

Metastasis is a major cause of high recurrence and poor survival of patients with colorectal cancer (CRC), although the mechanisms associated with this process remain poorly understood. In this study, we report a novel mechanism by which SOX13 promotes CRC metastasis by transactivating SNAI2 and c-MET. SOX13 overexpression was significantly correlated with more aggressive clinicopathological features of CRC and indicated poor prognosis in two independent cohorts of CRC patients (cohort I, n = 363; cohort II, n = 390). Overexpression of SOX13-promoted CRC migration, invasion, and metastasis, whereas SOX13 downregulation caused the opposite effects. Further mechanistic investigation identified SNAI2 and MET as important target genes of SOX13 using serial deletion and site-directed mutagenesis luciferase reporter and chromatin immunoprecipitation (ChIP) assays, as well as functional complementation analyses. In addition, SOX13 was shown to be a direct target of HGF/STAT3 signaling, and the c-MET inhibitor crizotinib blocked the HGF/STAT3/SOX13/c-MET axis, significantly inhibiting SOX13-mediated CRC migration, invasion and metastasis. Moreover, in clinical CRC tissues, SOX13 expression was positively correlated with the expression of SNAI2, c-MET, and HGF. CRC patients with positive coexpression of SOX13/SNAI2, SOX13/c-MET, or HGF/SOX13 exhibited a worse prognosis. In summary, SOX13 is a promising prognostic biomarker in patients with CRC, and blocking the HGF/STAT3/SOX13/c-MET axis with crizotinib could be a new therapeutic strategy to prevent SOX13-mediated CRC metastasis.

Large-Scale Virtual Screening Against the MET Kinase Domain Identifies a New Putative Inhibitor Type

By using an ensemble-docking strategy, we undertook a large-scale virtual screening campaign in order to identify new putative hits against the MET kinase target. Following a large molecular dynamics sampling of its conformational space, a set of 45 conformers of the kinase was retained as docking targets to take into account the flexibility of the binding site moieties. Our screening funnel started from about 80,000 chemical compounds to be tested in silico for their potential affinities towards the kinase binding site. The top 100 molecules selected—thanks to the molecular docking results—were further analyzed for their interactions, and 25 of the most promising ligands were tested for their ability to inhibit MET activity in cells. F0514-4011 compound was the most efficient and impaired this scattering response to HGF (Hepatocyte Growth Factor) with an IC50 of 7.2 μM. Interestingly, careful docking analysis of this molecule with MET suggests a possible conformation halfway between classical type-I and type-II MET inhibitors, with an additional region of interaction. This compound could therefore be an innovative seed to be repositioned from its initial antiviral purpose towards the field of MET inhibitors. Altogether, these results validate our ensemble docking strategy as a cost-effective functional method for drug development.

Differential Dependency of Human Pancreatic Cancer Cells on Targeting PTEN via PLK 1 Expression

Even though the tumour suppressive role of PTEN is well-known, its prognostic implications are ambiguous. The objective of this study was to further explore the function of PTEN expression in human pancreatic cancer. The expression of PTEN has been dominant in various human cancers including pancreatic cancer when compared with their matched normal tissues. The pancreatic cancer cells have been divided into PTEN blockade-susceptible and PTEN blockade-impassible groups dependent on targeting PTEN by altering intracellular signaling. The expression of PTEN has led to varying clinical outcomes of pancreatic cancer based on GEO Series (GSE) data analysis and Liptak’s z analysis. Differential dependency to PTEN blockade has been ascertained based on the expression of polo-like kinase1 PLK1 in pancreatic cancer cells. The prognostic value of PTEN also depends on PLK1 expression in pancreatic cancer. Collectively, the present study provides a rationale for targeting PTEN as a promising therapeutic strategy dependent on PLK1 expressions using a companion biomarker discovery platform.

Discovery of [1,2,4]triazolo[4,3-a]pyrazine derivatives bearing a 4-oxo-pyridazinone moiety as potential c-Met kinase inhibitors

We disclosed the preparation and biological evaluation of a series of [1,2,4]triazolo[4,3-a]pyrazine derivatives bearing 4-oxo-pyridazinone moieties, which demonstrated potent inhibition of c-Met kinase, culminating in the discovery of 22i.

CD9 identifies pancreatic cancer stem cells and modulates glutamine metabolism to fuel tumour growth

Pancreatic ductal adenocarcinoma (PDAC) shows great cellular heterogeneity, with pronounced epithelial and mesenchymal cancer cell populations. However, the cellular hierarchy underlying PDAC cell diversity is unknown. Here we identify the tetraspanin CD9 as a marker of PDAC tumour-initiating cells. CD9^high cells had increased organoid formation capability, and generated tumour grafts in vivo at limiting dilutions. Tumours initiated from CD9^high cells recapitulated the cellular heterogeneity of primary PDAC, whereas CD9^low cells only produced duct-like epithelial progeny. CD9 knockdown decreased the growth of PDAC organoids, and heterozygous CD9 deletion in Pdx1-Cre; LSL-KRas^G12D; p53^F/F mice prolonged overall survival. Mechanistically, CD9 promoted the plasma membrane localisation of the glutamine transporter ASCT2, enhancing glutamine uptake in PDAC cells. Thus, our study identifies a PDAC subpopulation capable of initiating PDAC and giving rise to PDAC heterogeneity, suggesting that the cellular diversity of PDAC is generated by PDAC stem cell differentiation.

Comparative characterization of the HGF/Met and MSP/Ron systems in primary pancreatic adenocarcinoma

Pancreatic cancer is an aggressive disease with a poor prognosis for which current standard chemotherapeutic treatments offer little survival benefit. Receptor tyrosine kinases (RTK)s have garnered interest as therapeutic targets to augment or replace standard chemotherapeutic treatments because of their ability to promote cell growth, migration, and survival in various cancers. Met and Ron, which are homologous RTKs activated by the ligands hepatocyte growth factor (HGF) and macrophage stimulating protein (MSP), respectively, are over-activated and display synergistic malignant effects in several cancers. Despite the homology between Met and Ron, studies that have directly compared the functional outcomes of these systems in any context are limited. To address this, we sought to determine if the HGF/Met and MSP/Ron systems produce overlapping or divergent contributions towards a malignant phenotype by performing a characterization of MSP and HGF driven signaling, behavioral, and transcriptomic responses in a primary pancreatic adenocarcinoma (PAAD) cell line in vitro. The impact of dual Met and Ron expression signatures on the overall survival of PAAD patients was also assessed. We found HGF and MSP both encouraged PAAD cell migration, but only HGF increased proliferation. RNA sequencing revealed that the transcriptomic effects of MSP mimicked a narrow subset of the responses induced by HGF. Analysis of clinical data indicated that the strong prognostic value of Met expression in primary PAAD does not appear to be modulated by Ron expression. The relatively reduced magnitude of MSP-dependent effects on primary PAAD cells are consistent with the limited prognostic value of Ron expression in this cancer when compared to Met. Although HGF and MSP produced a differing breadth of responses in vitro, overlapping pro-cancer signaling, behavioral, and transcriptional effects still point to a potential role for the MSP/Ron system in pancreatic cancer.

Correlation of clinicopathological features and leucine-rich repeat-containing G-protein-coupled receptor 5 expression in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer. Previous studies have established leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) as a cancer stem cell marker in gastrointestinal cancers. However, few reports have examined LGR5 in PDAC. Here we examined LGR5 expression and its clinicopathological significance in PDAC. We evaluated LGR5 expression in 78 PDAC patients who underwent surgical resection in our institution using RNAscope, a newly described RNA in situ hybridization technique. All 78 PDAC cases expressed LGR5 in cancer tissues, and LGR5 expression was prominent in the gland-forming part. LGR5 expression was significantly higher in patients with low histological grade (G1-G2) (p <  0.001) and early clinical stage (p =  0.004). Univariate analysis showed that low LGR5 expression (p =  0.034) was significantly associated with worse overall survival. However, LGR5 expression did not remain a predictor of prognosis in multivariate analysis (p =  0.639). All PDAC cases showed LGR5 expression to varying degrees, indicating LGR5 might be a cancer stem cell marker of PDAC, as in gastrointestinal cancer. Reduced LGR5 expression in tumor cells was associated with worse prognosis in PDAC. Further studies are required to elucidate the relationship between tumor progression and LGR5 expression in PDAC.

Combination Therapies and Drug Delivery Platforms in Combating Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC), the fourth leading cause of cancer-related death in the United States, is highly aggressive and resistant to both chemo- and radiotherapy. It remains one of the most difficult-to-treat cancers, not only due to its unique pathobiological features such as stroma-rich desmoplastic tumors surrounded by hypovascular and hypoperfused vessels limiting the transport of therapeutic agents, but also due to problematic early detection, which renders most treatment options largely ineffective, resulting in extensive metastasis. To elevate therapeutic effectiveness of treatments and overt their toxicity, significant enthusiasm was generated to exploit new strategies for combating PDAC. Combination therapy targeting different barriers to mitigate delivery issues and reduce tumor recurrence and metastasis has demonstrated optimal outcomes in patients' survival and quality of life, providing possible approaches to overcome therapeutic challenges. This paper aims to provide an overview of currently explored multimodal therapies using either conventional therapy or nanomedicines along with rationale, up-to-date progress, as well as the key challenges that must be overcome. Understanding the future directions of the field may assist in the successful development of novel treatment strategies for enhancing therapeutic efficacy in PDAC.

Target Deconvolution of a Multikinase Inhibitor with Antimetastatic Properties Identifies TAOK3 as a Key Contributor to a Cancer Stem Cell-Like Phenotype

Pancreatic cancer remains an incurable condition. Its progression is driven, in part, by subsets of cancer cells that evade the cytotoxic effects of conventional chemotherapies. These cells are often low-cycling, multidrug resistant, and adopt a stem cell-like phenotype consistent with the concept of cancer stem cells (CSC). To identify drugs impacting on tumor-promoting CSCs, we performed a differential high-throughput drug screen in pancreatic cancer cells cultured in traditional (2D) monolayers versus three-dimensional (3D) spheroids which replicate key elements of the CSC model. Among the agents capable of killing cells cultured in both formats was a 1H-benzo[d]imidazol-2-amine-based inhibitor of IL2-inducible T-cell kinase (ITK; NCGC00188382, inhibitor #1) that effectively mediated growth inhibition and induction of apoptosis in vitro, and suppressed cancer progression and metastasis formation in vivo An examination of this agent's polypharmacology via in vitro and in situ phosphoproteomic profiling demonstrated an activity profile enriched for mediators involved in DNA damage repair. Included was a strong inhibitory potential versus the thousand-and-one amino acid kinase 3 (TAOK3), CDK7, and aurora B kinases. We found that cells grown under CSC-enriching spheroid conditions are selectively dependent on TAOK3 signaling. Loss of TAOK3 decreases colony formation, expression of stem cell markers, and sensitizes spheroids to the genotoxic effect of gemcitabine, whereas overexpression of TAOK3 increases stem cell traits including tumor initiation and metastasis formation. By inactivating multiple components of the cell-cycle machinery in concert with the downregulation of key CSC signatures, inhibitor #1 defines a distinctive strategy for targeting pancreatic cancer cell populations.

Metabolism and epigenetics of pancreatic cancer stem cells

Pancreatic Cancer (PDA) is an aggressive malignancy characterized by early spread and a high mortality. Current studies suggest that a subpopulation of cells exist within tumors, cancer stem cell (CSC), which are capable of self-renewal and give rise to unique progeny which form the major neoplastic cellular component of tumors. While CSCs constitute a small cellular subpopulation within the tumor, their resistance to chemotherapy and radiation make them an important therapeutic target for eradication. Along with distinctive phenotypic properties, CSCs possess a unique metabolic plasticity allowing them to rapidly respond and adapt to environmental changes. These cells and their progeny also display a significantly altered epigenetic state with distinctive patterns of DNA methylation. Several mechanisms of cross-talk between epigenetic and metabolic pathways in PDA exist which ultimately contribute to the observed cellular plasticity and enhanced tumorigenesis. In this review we discuss various examples of this metabolic-epigenetic interplay and how it may constitute a new avenue for therapy specifically targeting CSCs in PDA.

MicroRNA-192-5p Promote the Proliferation and Metastasis of Hepatocellular Carcinoma Cell by Targeting SEMA3A

Side population (SP) cells are a small subset of cells isolated from a cultured cancer cell line with characteristics similar to those of cancer stem cells, such as high metastatic and tumorigenic potentials. However, the molecular mechanisms remain unclear for the malignant properties of SP cells. In this study, SP cells were isolated by staining cultured HCCLM3 cells with fluorescent DNA-binding dye Hoechst 33342 and sorted by flow cytometry. The proportion of SP cells was 2.79%±0.19% in the HCCLM3 cell line. Compared with non-SP cells, SP cells possessed stronger capability of sphere formation and tumorigenicity, and expressed higher levels of CD133 and CD90. Then, we found that SP cells possessed 25 upregulated and 34 downregulated microRNAs with differences of >3-fold. As one of the upregulated microRNAs, miR-192-5p was computationally predicted to target semaphorin 3A (SEMA3A), a potent suppressor of tumor angiogenesis in various cancer models. Luciferase reporter assay showed that SEMA3A was a direct target of miR-192-5p. Overexpression of miR-192-5p promoted cell proliferation and metastasis targeting SEMA3A in HCCLM3 cells. Immunohistochemical staining revealed that SEMA3A expression was significantly reverse associated with metastasis in hepatocellular carcinoma tissues. The results indicate that miR-192-5p contributes to targeting SEMA3A in HCCLM3 cells, and this may be used as a target in targeted therapy and a marker for cancer behavior and prognosis.

Exosomes, metastases, and the miracle of cancer stem cell markers

Cancer-initiating cells (CIC) are the driving force in tumor progression. There is strong evidence that CIC fulfill this task via exosomes (TEX), which modulate and reprogram stroma, nontransformed cells, and non-CIC. Characterization of CIC, besides others, builds on expression of CIC markers, many of which are known as metastasis-associated molecules. We here discuss that the linkage between CIC/CIC-TEX and metastasis-associated molecules is not fortuitously, but relies on the contribution of these markers to TEX biogenesis including loading and TEX target interactions. In addition, CIC markers contribute to TEX binding- and uptake-promoted activation of signaling cascades, transcription initiation, and translational control. Our point of view will be outlined for pancreas and colon CIC highly expressing CD44v6, Tspan8, EPCAM, claudin7, and LGR5, which distinctly but coordinately contribute to tumor progression. Despite overwhelming progress in unraveling the metastatic cascade and the multiple tasks taken over by CIC-TEX, there remains a considerable gap in linking CIC biomarkers, TEX, and TEX-initiated target modulation with metastasis. We will try to outline possible bridges, which could allow depicting pathways for new and expectedly powerful therapeutic interference with tumor progression.