Acquisition of epithelial-mesenchymal transition phenotype of gemcitabine-resistant pancreatic cancer cells is linked with activation of the notch signaling pathway

Gemcitabine resistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) ranks fourth among cancer related deaths. The disappointing 5-year survival rate of below 5% stems from drug resistance to all known therapies, as well as from disease presentation at a late stage when PDA is already metastatic. Gemcitabine has been the cornerstone of PDA treatment in all stages of the disease for the last two decades, but gemcitabine resistance develops within weeks of chemotherapy initiation. From a mechanistic perspective, gemcitabine resistance may result from alterations in drug metabolism until the point that the cytidine analog is incorporated into the DNA, or from mitigation of gemcitabine-induced apoptosis. Both of these drug resistance modalities can be either intrinsic to the cancer cell, or influenced by the cancer microenvironment. Mechanisms of intrinsic gemcitabine resistance are difficult to tackle, as many of the genes that drive the carcinogenic process itself also interfere with gemcitabine-induced apoptosis. In this regard, recent understanding of the involvement of microRNAs in gemcitabine resistance may offer new opportunities to overcome intrinsic gemcitabine resistance. The characteristically fibrotic and immune infiltrated stroma of PDA that accompanies tumor inception and expansion is a lush ground for treatments aimed at targeting tumor microenvironment-mediated drug resistance. In the last couple of years, drugs interfering with tumor microenvironment have matured to clinical trials. Although drugs inducing 'stromal depletion' have yet failed to improve survival, they have greatly increased our understanding of tumor microenvironment-mediated drug resistance. In this review we summarize the current knowledge on intrinsic and environment-mediated gemcitabine resistance, and discuss the impact of these pathways on patient screening, and on future treatments aimed to potentiate gemcitabine activity.

Mathematical Modelling of Molecular Pathways Enabling Tumour Cell Invasion and Migration

Understanding the etiology of metastasis is very important in clinical perspective, since it is estimated that metastasis accounts for 90% of cancer patient mortality. Metastasis results from a sequence of multiple steps including invasion and migration. The early stages of metastasis are tightly controlled in normal cells and can be drastically affected by malignant mutations; therefore, they might constitute the principal determinants of the overall metastatic rate even if the later stages take long to occur. To elucidate the role of individual mutations or their combinations affecting the metastatic development, a logical model has been constructed that recapitulates published experimental results of known gene perturbations on local invasion and migration processes, and predict the effect of not yet experimentally assessed mutations. The model has been validated using experimental data on transcriptome dynamics following TGF-β-dependent induction of Epithelial to Mesenchymal Transition in lung cancer cell lines. A method to associate gene expression profiles with different stable state solutions of the logical model has been developed for that purpose. In addition, we have systematically predicted alleviating (masking) and synergistic pairwise genetic interactions between the genes composing the model with respect to the probability of acquiring the metastatic phenotype. We focused on several unexpected synergistic genetic interactions leading to theoretically very high metastasis probability. Among them, the synergistic combination of Notch overexpression and p53 deletion shows one of the strongest effects, which is in agreement with a recent published experiment in a mouse model of gut cancer. The mathematical model can recapitulate experimental mutations in both cell line and mouse models. Furthermore, the model predicts new gene perturbations that affect the early steps of metastasis underlying potential intervention points for innovative therapeutic strategies in oncology.

Links between cancer stem cells and epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) has been reported to be an important program that is often activated during the process of cancer invasion and metastasis. Cancer stem cells (CSCs) that can initiate and maintain cancer are also involved in invasion and metastasis of cancer. Recently, insights into the molecular mechanisms and functional features of mesenchymal cells have been greatly colored by findings that some of them have been endowed with the self-renewal trait associated with normal tissue stem cells and CSCs. Among cancer cells experiencing EMT, only some of the most competent CSCs will succeed in planting in another organ. In this paper, we review the molecular mechanism behind the link of EMT and CSCs in cancer progression.

Molecular signature of pancreatic adenocarcinoma: an insight from genotype to phenotype and challenges for targeted therapy

INTRODUCTION

Pancreatic adenocarcinoma remains one of the most clinically challenging cancers despite an in-depth characterization of the molecular underpinnings and biology of this disease. Recent whole-genome-wide studies have elucidated the diverse and complex genetic alterations which generate a unique oncogenic signature for an individual pancreatic cancer patient and which may explain diverse disease behavior in a clinical setting.

AREAS COVERED

In this review article, we discuss the key oncogenic pathways of pancreatic cancer including RAS-MAPK, PI3KCA and TGF-β signaling, as well as the impact of these pathways on the disease behavior and their potential targetability. The role of tumor suppressors particularly BRCA1 and BRCA2 genes and their role in pancreatic cancer treatment are elaborated upon. We further review recent genomic studies and their impact on future pancreatic cancer treatment.

EXPERT OPINION

Targeted therapies inhibiting pro-survival pathways have limited impact on pancreatic cancer outcomes. Activation of pro-apoptotic pathways along with suppression of cancer-stem-related pathways may reverse treatment resistance in pancreatic cancer. While targeted therapy or a 'precision medicine' approach in pancreatic adenocarcinoma remains an elusive challenge for the majority of patients, there is a real sense of optimism that the strides made in understanding the molecular underpinnings of this disease will translate into improved outcomes.

A new role for the PI3K/Akt signaling pathway in the epithelial-mesenchymal transition

Tumor metastasis is not only a sign of disease severity but also a major factor causing treatment failure and cancer-related death. Therefore, studies on the molecular mechanisms of tumor metastasis are critical for the development of treatments and for the improvement of survival. The epithelial-mesenchymal transition (EMT) is an orderly, polygenic biological process that plays an important role in tumor cell invasion, metastasis and chemoresistance. The complex, multi-step process of EMT involves multiple regulatory mechanisms. Specifically, the PI3K/Akt signaling pathway can affect the EMT in a variety of ways to influence tumor aggressiveness. A better understanding of the regulatory mechanisms related to the EMT can provide a theoretical basis for the early prediction of tumor progression as well as targeted therapy.

Notch1 pathway in adrenocortical carcinomas: correlations with clinical outcome

Previous SNP array analyses have revealed genomic alterations of the Notch pathway as being the most frequent abnormality in adrenocortical tumors (ACTs). The aim of the present study was to evaluate the expression of components of Notch signaling in ACTs and to correlate them with clinical outcome. The mRNA expression of JAG1, NOTCH1, and selected target genes of NOTCH1 (HES1, HES5, and HEY2) was evaluated in 80 fresh frozen samples (28 normal adrenal glands (NAGs), 24 adenomas (ACAs), and 28 carcinomas (ACCs)) by quantitative RT-PCR. Immunohistochemistry was performed in 221 tissues on paraffin slides (16 NAGs, 27 ACAs, and 178 ACCs) for JAG1, activated NOTCH1 (aNOTCH1), and HEY2. An independent ACC validation cohort (n=77) was then also investigated. HEY2 mRNA expression was higher in ACCs than it was in ACAs (P<0.05). The protein expression of all of the factors was high (H-score 2-3) in a larger proportion of ACCs as compared to ACAs and NAGs (JAG1 in 27, 15, and 10%; aNOTCH1 in 13, 8, and 0%; HEY2 in 66, 61, and 33% respectively, all P<0.001). High JAG1 expression was associated with earlier tumor stages and lower numbers of metastases in ACCs (both P=0.08) and favorably impacted overall and progression-free survival (PFS) (131 vs 30 months, hazard ratio (HR) 0.45, and 37 vs 9 months, HR 0.51, both P<0.005). This impact on overall survival (OS) was confirmed in the validation cohort. No such association was observed for aNOTCH1 or HEY2. In conclusion, different components of the Notch1 signaling pathway are overexpressed in ACCs, which suggests a role for the pathway in malignant transformation. However, JAG1 is overexpressed in a subgroup of ACCs with a better clinical outcome.

Blockade of dual-specificity phosphatase 28 decreases chemo-resistance and migration in human pancreatic cancer cells

Pancreatic cancer remains one of the most deadly cancers, with a grave prognosis. Despite numerous endeavors to improve treatment of the neoplasm, limited progress has been made. In the present study, we investigated the role of dual specificity phosphatase 28 (DUSP28) in relation to anti-cancer drug sensitivity and migratory activity in human pancreatic cancer cells for the first time. Analysis using Universal exPress Codes (UPCs) with the GEO database showed significantly higher DUSP28 mRNA expression in pancreatic cancers. We found that DUSP28 was highly expressed in several human pancreatic cancer cell lines that showed resistance to anti-cancer drugs. Overexpression of DUSP28 decreased anti-cancer drug-sensitivity and enhanced cellular migration via the ERK1/2 pathway in DUSP28-negative cell lines. Knockdown of DUSP28 re-sensitized cells to anti-cancer drugs even at sublethal doses by inducing an apoptotic pathway and significantly reduced migration in DUSP28-positive human pancreatic cancer cell lines. Furthermore, DUSP28-positive cell line (Panc-1) xenograft models were more resistant to gemcitabine treatment than DUSP28-negative cell line (SNU-213) xenograft models. Collectively, these results indicate that DUSP28 plays a key role in drug resistance and migratory activity in human pancreatic cells, and suggest that targeting DUSP28 might have clinical relevance in eradicating malignant pancreatic cancers.

Implications of the Hybrid Epithelial/Mesenchymal Phenotype in Metastasis

Transitions between epithelial and mesenchymal phenotypes – the epithelial to ­mesenchymal transition (EMT) and its reverse the mesenchymal to epithelial transition (MET) – are hallmarks of cancer metastasis. While transitioning between the epithelial and mesenchymal phenotypes, cells can also attain a hybrid epithelial/mesenchymal (E/M) (i.e., partial or intermediate EMT) phenotype. Cells in this phenotype have mixed epithelial (e.g., adhesion) and mesenchymal (e.g., migration) properties, thereby allowing them to move collectively as clusters. If these clusters reach the bloodstream intact, they can give rise to clusters of circulating tumor cells (CTCs), as have often been seen experimentally. Here, we review the operating principles of the core regulatory network for EMT/MET that acts as a “three-way” switch giving rise to three distinct phenotypes – E, M and hybrid E/M – and present a theoretical framework that can elucidate the role of many other players in regulating epithelial plasticity. Furthermore, we highlight recent studies on partial EMT and its association with drug resistance and tumor-initiating potential; and discuss how cell–cell communication between cells in a partial EMT phenotype can enable the formation of clusters of CTCs. These clusters can be more apoptosis-resistant and have more tumor-initiating potential than singly moving CTCs with a wholly mesenchymal (complete EMT) phenotype. Also, more such clusters can be formed under inflammatory conditions that are often generated by various therapies. Finally, we discuss the multiple advantages that the partial EMT or hybrid E/M phenotype have as compared to a complete EMT phenotype and argue that these collectively migrating cells are the primary “bad actors” of metastasis.

miR-15b promotes epithelial-mesenchymal transition by inhibiting SMURF2 in pancreatic cancer

The epithelial-mesenchymal transition (EMT) is a key developmental program that is often activated during cancer invasion and metastasis. We report here that silencing SMURF2 (SMAD specific E3 ubiquitin protein ligase 2) promoted EMT in HPDE6c7 normal pancreas cells and overexpression of SMURF2 inhibited TGF-β-mediated EMT in the cells. Subsequent studies showed that SMURF2 was downregulated in pancreatic cancer tissues and it promoted mesenchymal-epithelial transition (MET) in pancreatic cancer cells as well as its expression negatively associated with gemcitabine-resistance, but it did not alter cell viability, cell cycle and cell senescence. In addition, we demonstrated that miR‑15b degraded SMURF2 and its overexpression promoted EMT in pancreatic cancer, and its expression was associated with metastasis in the disease. Elucidating molecular mechanism of EMT in pancreatic cancer not only will help us to further understand the pathogenesis and progression of the disease, but also offers new targets for effective therapies.

Zidovudine, an anti-viral drug, resensitizes gemcitabine-resistant pancreatic cancer cells to gemcitabine by inhibition of the Akt-GSK3β-Snail pathway

Pancreatic cancer is one of the most difficult malignancies to treat owing to the rapid acquisition of resistance to chemotherapy. Gemcitabine, a first-line treatment for pancreatic cancer, prolongs patient survival by several months, and combination treatment with gemcitabine and other anti-cancer drugs in the clinic do not show any significant effects on overall survival. Thus, identification of a drug that resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine and a better understanding of the molecular mechanisms of gemcitabine resistance are critical to develop new therapeutic options for pancreatic cancer. Here, we report that zidovudine resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine as shown by screening a compound library, including clinical medicine, using gemcitabine-resistant cells. In analyzing the molecular mechanisms of zidovudine effects, we found that the epithelial-to-mesenchymal transition (EMT)-like phenotype and downregulation of human equilibrative nucleoside transporter 1 (hENT1) are essential for the acquisition of gemcitabine resistance, and zidovudine restored these changes. The chemical biology investigations also revealed that activation of the Akt-GSK3β-Snail1 pathway in resistant cells is a key signaling event for gemcitabine resistance, and zidovudine resensitized resistant cells to gemcitabine by inhibiting this activated pathway. Moreover, our in vivo study demonstrated that co-administration of zidovudine and gemcitabine strongly suppressed the formation of tumors by gemcitabine-resistant pancreatic cancer and prevented gemcitabine-sensitive pancreatic tumors from acquiring gemcitabine-resistant properties, inducing an EMT-like phenotype and downregulating hENT1 expression. These results suggested that co-treatment with zidovudine and gemcitabine may become a novel therapeutic strategy for pancreatic cancer by inhibiting chemoresistance-specific signaling.

Mechanism of fatty acid synthase in drug tolerance related to epithelial-mesenchymal transition of breast cancer

OBJECTIVE

The mechanism of action of fatty acid synthase (FASN) in drug tolerance of breast cancer cells with epithelial-mesenchymal transition (EMT) features was investigated.

METHODS

The breast cancer cell line MCF-7-MEK5 with stably occurring EMT and tumour necrosis factor-α (TNF-α) tolerance was used as the experimental model, whereas MCF-7 acted as the control. Tumour cells were implanted into nude mice for in vivo analysis, and cerulenin was used as a FASN inhibitor. RT-PCR, real-time quantitative PCR and Western blot were employed to detect the expression of FASN, TNFR-1, TNFR-2, Wnt-1, β-catenin and cytC at the RNA and protein levels.

RESULTS

Compared with MCF-7, TNFR-1 expression in MCF-7-MEK5 was slightly changed, TNFR-2 was decreased, and FASN, Wnt-1, β-catenin and cytC were increased. The expression of Wnt-1 and β-catenin in MCF-7-MEK5 decreased after cerulenin treatment, whereas cytC expression increased.

CONCLUSIONS

The important function of FASN in the drug tolerance of breast cancer may be due to the following mechanisms: FASN downregulated TNFR-2 expression through lipid rafts to make the cells less sensitive to TNF-α, and simultaneously activated the Wnt-1/β-catenin signalling pathway. Thus, cytC expression increased, which provided cells with anti-apoptotic capacity and induced drug tolerance.

Slug contributes to gemcitabine resistance through epithelial-mesenchymal transition in CD133(+) pancreatic cancer cells

CD133-positive pancreatic cancer is correlated with unfavorable survival despite current development of therapy. Slug acts as a master regulator of epithelial-mesenchymal transition (EMT) which is the essential process in cancer progression. The aim of this study was to investigate the role of Slug in gemcitabine treatment for CD133-positive pancreatic cancer cells. We used a previously established pancreatic cancer cell line expressing high level of CD133 (Capan-1M9), which also expresses high level of Slug. We generated Slug knock-down subclone (shSlug M9) from this cell line, and compared expression of EMT-related genes, migration, invasion and gemcitabine resistance between two cell lines. Slug knock-down in CD133-positive pancreatic cancer cell line led to the reduction of migration and invasion ability. Furthermore, Slug knock-down sensitized CD133-positive pancreatic cancer cell line to gemcitabine. These results suggest that Slug plays an important role in not only invasion ability through EMT but also gemcitabine resistance of CD133-positive pancreatic cancer cells.

Overexpression of SIX1 is an independent prognostic marker in stage I-III colorectal cancer

Epithelial-to-mesenchymal transition (EMT) contributes significantly to tumor progression and metastasis. The assessment of EMT-associated transcription factors could be a promising approach to identify biomarkers and potential therapeutic targets in colorectal cancer. In our study, we focused on the transcription factor "Sine oculis homeobox" (SIX) 1, which is a member of the superfamily of the homeobox genes and has been described to promote EMT in different types of tumors. Immunohistochemistry against SIX1 was performed on colorectal mucosa, adenomas, carcinomas-in situ and primary adenocarcinomas. An expression score was developed and subsequently assessed for its prognostic value in two independent cohorts. Cohort 1 consisted of 128 patients with stage I-III colorectal cancer; cohort 2 included 817 patients with stage I-III colorectal cancer who had participated in the DACHS study. HCT-116 cells were transfected with SIX1 plasmids and subjected to migration and colony formation assays. The expression of SIX1 increases gradually from mucosa to colorectal adenocarcinomas (p > 0.0001). Univariate and multivariate analyses reveal that high expression of SIX1 is associated with decreased overall survival (cohort 1: HR: 4.01, CI: 1.20-14.07, p = 0.025; cohort 2: HR: 1.43, CI: 1.014-2.02, p = 0.047). Overexpression of SIX1 induces a more mesenchymal-like phenotype in HCT-116 cells and enhances tumor migration. High expression of SIX1 is an independent prognostic marker in colorectal cancer. It might be a promising biomarker to stratify patients into different risk groups. Moreover, targeting SIX1 might be a novel therapeutic approach in patients with colorectal cancer.

Novel strategies targeting cancer stem cells through phytochemicals and their analogs

Cancer stem cells (CSCs) are cells that exist within a tumor with a capacity of self-renewal and an ability to differentiate, giving rise to heterogeneous populations of cancer cells. These cells are increasingly being implicated in resistance to conventional therapeutics and have also been implicated in tumor recurrence. Several cellular signaling pathways including Notch, Wnt, phosphoinositide-3-kinase-Akt-mammalian target of rapamycin pathways, and known markers such as CD44, CD133, CD166, ALDH, etc. have been associated with CSCs. Here, we have reviewed our current understanding of self-renewal pathways and factors that help in the survival of CSCs with special emphasis on those that have been documented to be modulated by well characterized natural agents such as curcumin, sulforaphane, resveratrol, genistein, and epigallocatechin gallate. With the inclusion of a novel derivative of curcumin, CDF, we showcase how natural agents can be effectively modified to increase their efficacy, particularly against CSCs. We hope that this article will generate interest among researchers for further mechanistic and clinical studies exploiting the cancer preventive and therapeutic role of nutraceuticals by targeted elimination of CSCs.

γ-Secretase inhibitor inhibits bladder cancer cell drug resistance and invasion by reducing epithelial-mesenchymal transition

A previous study by our group demonstrated that the expression levels of Notch 1 and Jagged 1 in bladder cancer cells was significantly lower compared with those in normal bladder mucosa, while the expression levels of Notch 1 and Jagged 1 in invasive bladder cancer were higher compared with those in superficial bladder cancer. The present study investigated the effect of the Notch signaling pathway on the drug resistance and invasiveness of bladder cancer cells. It was demonstrated that complete inhibition of the Notch signaling pathway induced significant morphological changes and inhibited cell proliferation and migration (P<0.05). Reverse transcription quantitative polymerase chain reaction and western blot analyses revealed that the mRNA and protein expression levels of E-cadherin were upregulated (P<0.05) and the mRNA and protein expression levels of N-cadherin, vimentin and α-smooth muscle actin were downregulated (P<0.05). The present study concluded that complete inhibition of the Notch signaling pathway inhibited cell proliferation and invasion, and reduced drug resistance in bladder cancer cells, a phenomenon which may be associated with the inhibition of the epithelial-mesenchymal transition.

Functional Impact of Autophagy-Related Genes on the Homeostasis and Dynamics of Pancreatic Cancer Cell Lines

Pancreatic cancer is a highly aggressive and chemotherapy-resistant malignant neoplasm. In basal condition, it is characterized by elevated autophagy activity, which is required for tumor growth and that correlates with treatment failure. We analyzed the expression of autophagy related genes in different pancreatic cancer cell lines. A correlation-based network analysis evidenced the sociality and topological roles of the autophagy-related genes after serum starvation. Structural and functional tests identified a core set of autophagy related genes, suggesting different scenarios of autophagic responses to starvation, which may be responsible for the clinical variations associated with pancreatic cancer pathogenesis.

The epithelial to mesenchymal transition in pancreatic cancer: A systematic review

BACKGROUND/OBJECTIVES

The present article summarizes and analyzes the current knowledge about the role of the epithelial to mesenchymal transition (EMT) in the systemic invasiveness of pancreatic cancer.

METHOD

An electronic search of PubMed/MEDLINE, EMBASE, and the Web of Science was used to identify relevant original articles and reviews.

RESULTS

The EMT represents a key step during normal embryogenesis. However, increasing evidence reveals its essential role in the local progression and metastasis of pancreatic cancer. Areas of interest are the cross-linking between cells undergoing the EMT and pancreatic cancer stem cells, and the correlation between the EMT and chemoresistance to standard therapies. During carcinogenesis, malignant pancreatic cells at the primary site acquire the ability to undergo the EMT, a transformation associated with increased mobility. The reverse process at secondary sites, the mesenchymal to epithelial transition (MET), has devastating consequences, allowing neoplastic epithelial cells to invade surrounding tissues and spread to distant sites. Consequences of the EMT are the loss of E-cadherin expression and the acquisition of mesenchymal markers including fibronectin or vimentin. Detailed knowledge of the molecular processes underlying the EMT has opened possibilities for new therapeutic agents. These include an EMT approach for patients with early cancers, to prevent invasion and dissemination, and anti-MET therapy for patients with established metastasis.

CONCLUSIONS

The current literature shows a strong correlation between the EMT and the systemic aggressiveness of pancreatic tumors. Individualized therapy, targeting the process of EMT and its cross-linking with cancer stem cells, may increase survival of patients with pancreatic cancer.

Anti-tumor effect of the extract from qingyihuaji formula on pancreatic cancer by down-regulating Notch-4 and Jagged-1

OBJECTIVE

To investigate, in terms of Notch signaling pathway, the effect on pancreatic cancer of the extract of an anti-tumor prescription--Qingyi-huaji formula (QYHJ)--from Traditional Chinese Medicine (TCM).

METHODS

Nude mice were implanted subcutaneously with human pancreatic cancer cell line SW1990 and then randomly divided into four groups: Control, QYHJ extract, Gemcitabine, and Combination of QYHJ extract and gemcitabine. Treatments were given for 21 days and tumor growth was evaluated simultaneously. Then, expression of Notch receptors (Notch-1, Notch-2, Notch-3, and Notch-4) and their Jagged ligands (Jagged-1 and Jagged-2) in dissected tumor tissue were detected by real-time quantitative reverse transcription-polymerase chain reaction and Western blot. Finally, immunohistochemistry was performed to detect CD133, a marker of pancreatic cancer stem cells (CSCs), to evaluate the impact of QYHJ extract on pancreatic CSCs.

RESULTS

QYHJ extract treatment effectively inhibited the tumor growth in nude mice. The expression of both Notch-4 and Jagged-1 were decreased significantly in QYHJ treatment groups (P < 0.05), while gemcitabine alone had no significant effect in down-regulating Jagged-1 (P > 0.05). No significant difference was observed in the ex- pression of Notch-1, Notch-2, Notch-3, and Jagged-2 between three treatment groups and control group (P > 0.05). Moreover, immunohistochemical analysis showed that the number of CD133 positive cells was significantly reduced by QYHJ treatment (P < 0.05), and the combined treatment was more effective than gemcitabine alone (P < 0.05).

CONCLUSION

The role of the extract in pancreatic cancer treatment was associated with down-regulation of Notch-4 and Jagged-1 in Notch signaling pathway. The extract could enhance the antitumor activity of gemcitabine and was more effective than gemcitabine in regulating Notch signaling pathway to some extent.

Establishment and characterization of GCSR1, a multi-drug resistant signet ring cell gastric cancer cell line

Signet ring cell gastric cancer (SRCGC) has very poor prognosis worldwide, and studying its molecular characteristics is urgent for improving the outcome. However, few well-characterized SRCGC cell lines are available for research. Therefore, we established a novel cell line GCSR1, from a Chinese male SRCGC patient. Cell morphology of GCSR1 in culture, maintained in vitro for over 90 passages, is similar to the cells from the patient. GCSR1 cells proliferated in vitro with a doubling time of 67.65 h. Karyotyping showed they were aneuploid. Missense mutation occurred in codon 193 of P53 and deletion occurred in exons 1 and 3 of P16. Results of CCK8 assay revealed that GCSR1 was more resistant to 5-fluorouracil (5-FU) and mitomycin (MMC) than other gastric cancer cell lines. Stem cell marker assay by flow cytometry showed that GCSR1 had high proportion of CD44+ and/or CD133+ cells. It formed colonies easily in soft agar and generated xenograft tumors in nude mice. In conclusion, GCSR1 is a well-established, well-characterized multi-drug resistant cell line with abundant cancer stem cells.

miR-186 regulation of Twist1 and ovarian cancer sensitivity to cisplatin

Epithelial-mesenchymal transition (EMT) has an established role in promoting tumor progression and the acquisition of therapeutic resistance. Here, the EMT phenotype was detected in cisplatin-resistant ovarian cancer tissues and cell lines, and correlated with decreased miR-186 expression, increased Twist1 expression, chemoresistance and poor prognosis in epithelial ovarian cancer (EOC) patients. Introducing miR-186 into EOC cells led to a reduction in twist family bHLH transcription factor 1 (Twist1) expression along with morphological, functional and molecular changes consistent with mesenchymal-to-epithelial transition, G1 cell-cycle arrest and enhanced cell apoptosis, which consequently rendered the cells more sensitive to cisplatin in vitro and in vivo. Furthermore, luciferase reporter and rescue assay results showed that the EMT and drug resistance reversal in response to miR-186 was mediated by Twist1. Collectively, these findings implicate miR-186 as an attractive candidate for overcoming chemoresistance in ovarian cancer therapy.

The effectiveness of an anti-human IL-6 receptor monoclonal antibody combined with chemotherapy to target colon cancer stem-like cells

Recent studies have demonstrated that cancer stem cells (CSCs) can initiate and sustain tumor growth and exhibit resistance to clinical cytotoxic therapies. Therefore, CSCs represent the main target of anticancer therapy. Interleukin-6 (IL-6) promotes cellular proliferation and drug resistance in colorectal cancer, and its serum levels correlate with patient survival. Therefore, IL-6 and its downstream signaling molecule the signal transducer and activator of transcription-3 (STAT3) represent potential molecular targets. In the present study, we investigated the effects of IL-6 and its downstream signaling components on stem cell biology, particularly the chemoresistance of CSCs, to explore potential molecular targets for cancer therapy. The colon cancer cell line WiDr was cultured in serum-free, non-adherent, and three-dimensional spheroid-forming conditions to enrich the stem cell-like population. Spheroid-forming cells slowly proliferated and expressed high levels of Oct-4, Klf4, Bmi-1, Lgr5, IL-6, and Notch 3 compared with adherent cells. Treatment with an anti-human IL-6 receptor monoclonal antibody reduced spheroid formation, stem cell-related gene expression, and 5-fluorouracil (5-FU) resistance. In addition, IL-6 treatment enhanced the levels of p-STAT3 (Tyr705), the expression of Oct-4, Klf4, Lgr5, and Notch 3, and chemoresistance to 5-FU. siRNA targeting Notch 3 suppressed spheroid formation, Oct-4 and Lgr5 expression, and 5-FU chemoresistance, whereas STAT3 inhibition enhanced Oct-4, Klf4, Lgr5, and Notch 3 expression and 5-FU chemoresistance along with reduced spheroid growth. Taken together, these results indicate that IL-6 functions in dichotomous pathways involving Notch 3 induction and STAT3 activation. The former pathway is involved in cancer stem-like cell biology and enhanced chemoresistance, and the latter pathway leads to accelerated proliferation and reduced chemoresistance. Thus, an anti-human IL-6 receptor monoclonal antibody or Notch 3 inhibition may be superior to STAT3 inhibition for CSC-targeting therapies concomitant with anticancer drugs.

The Regulatory Role of MicroRNAs in EMT and Cancer

The epithelial to mesenchymal transition (EMT) is a powerful process in tumor invasion, metastasis, and tumorigenesis and describes the molecular reprogramming and phenotypic changes that are characterized by a transition from polarized immotile epithelial cells to motile mesenchymal cells. It is now well known that miRNAs are important regulators of malignant transformation and metastasis. The aberrant expression of the miR-200 family in cancer and its involvement in the initiation and progression of malignant transformation has been well demonstrated. The metastasis suppressive role of the miR-200 members is strongly associated with a pathologic EMT. This review describes the most recent advances regarding the influence of miRNAs in EMT and the control they exert in major signaling pathways in various cancers. The ability of the autocrine TGF-β/ZEB/miR-200 signaling regulatory network to control cell plasticity between the epithelial and mesenchymal state is further discussed. Various miRNAs are reported to directly target EMT transcription factors and components of the cell architecture, as well as miRNAs that are able to reverse the EMT process by targeting the Notch and Wnt signaling pathways. The link between cancer stem cells and EMT is also reported and the most recent developments regarding clinical trials that are currently using anti-miRNA constructs are further discussed.

GLI2-dependent c-MYC upregulation mediates resistance of pancreatic cancer cells to the BET bromodomain inhibitor JQ1

JQ1 and I-BET151 are selective inhibitors of BET bromodomain proteins that have efficacy against a number of different cancers. Since the effectiveness of targeted therapies is often limited by development of resistance, we examined whether it was possible for cancer cells to develop resistance to the BET inhibitor JQ1. Here we show that pancreatic cancer cells developing resistance to JQ1 demonstrate cross-resistance to I-BET151 and insensitivity to BRD4 downregulation. The resistant cells maintain expression of c-MYC, increase expression of JQ1-target genes FOSL1 and HMGA2, and demonstrate evidence of epithelial-mesenchymal transition (EMT). However, reverting EMT fails to sensitize the resistant cells to JQ1 treatment. Importantly, the JQ1-resistant cells remain dependent on c-MYC that now becomes co-regulated by high levels of GLI2. Furthermore, downregulating GLI2 re-sensitizes the resistant cells to JQ1. Overall, these results identify a mechanism by which cancer cells develop resistance to BET inhibitors.

Long noncoding RNA MALAT-1 enhances stem cell-like phenotypes in pancreatic cancer cells

Cancer stem cells (CSCs) play a vital role in tumor initiation, progression, metastasis, chemoresistance, and recurrence. The mechanisms that maintain the stemness of these cells remain largely unknown. Our previous study indicated that MALAT-1 may serve as an oncogenic long noncoding RNA in pancreatic cancer by promoting epithelial-mesenchymal transition (EMT) and regulating CSCs markers expression. More significantly, there is emerging evidence that the EMT process may give rise to CSCs, or at least cells with stem cell-like properties. Therefore, we hypothesized that MALAT-1 might enhance stem cell-like phenotypes in pancreatic cancer cells. In this study, our data showed that MALAT-1 could increase the proportion of pancreatic CSCs, maintain self-renewing capacity, decrease the chemosensitivity to anticancer drugs, and accelerate tumor angiogenesis in vitro. In addition, subcutaneous nude mouse xenografts revealed that MALAT-1 could promote tumorigenicity of pancreatic cancer cells in vivo. The underlying mechanisms may involve in increased expression of self-renewal related factors Sox2. Collectively, we for the first time found the potential effects of MALAT-1 on the stem cell-like phenotypes in pancreatic cancer cells, suggesting a novel role of MALAT-1 in tumor stemness, which remains to be fully elucidated.

Codelivery of small molecule hedgehog inhibitor and miRNA for treating pancreatic cancer

Successful treatment of pancreatic ductal adenocarcinoma (PDAC) remains a challenge due to the desmoplastic microenvironment that promotes both tumor growth and metastasis and forms a barrier to chemotherapy. Hedgehog (Hh) signaling is implicated in initiation and progression of PDAC and also contributes to desmoplasia. While Hh levels are increased in pancreatic cancer cells, levels of tumor suppressor miR-let7b, which targets several genes involved in PDAC pathogenesis, is downregulated. Therefore, our overall objective was to inhibit Hh pathway and restore miR-let7b simultaneously for synergistically treating PDAC. miR-let7b and Hh inhibitor GDC-0449 could inhibit the proliferation of human pancreatic cancer cells (Capan-1, HPAF-II, T3M4, and MIA PaCa-2), and there was synergistic effect when miR-let7b and GDC-0449 were coformulated into micelles using methoxy poly(ethylene glycol)-block-poly(2-methyl- 2-carboxyl-propylenecarbonate-graft-dodecanol-graft-tetraethylene-pentamine) (mPEG-b-PCC-g-DC-g-TEPA). This copolymer self-assembled into micelles of <100 nm and encapsulated hydrophobic GDC-0449 into its core with 5% w/w drug loading and allowed complex formation between miR-let7b and its cationic pendant chains. Complete polyplex formation with miRNA was observed at the N/P ratio of 16/1. Almost 80% of GDC-0449 was released from the polyplex in a sustained manner in 2 days. miRNA in the micelle formulation was stable for up to 24 h in the presence of serum and high uptake efficiency was achieved with low cytotoxicity. This combination therapy effectively inhibited tumor growth when injected to athymic nude mice bearing ectopic tumor generated using MIA PaCa-2 cells compared to micelles carrying GDC-0449 or miR-let7b alone. Immunohistochemical analysis revealed decreased tumor cell proliferation with increased apoptosis in the animals treated with miR-let7b and GDC-0449 combination.

VGLL4 inhibits EMT in part through suppressing Wnt/β-catenin signaling pathway in gastric cancer

VGLL4 is a member of the Vestigial-like proteins that functions as a tumor suppressor, which directly competes with YAP for binding TEADs in several cancer types. Recently, an increasing number of studies have reported that VGLL4 acts as a crucial role in regulating cell mobility, migration, and invasion. However, little is known about the signaling mechanisms in regulating epithelial-mesenchymal transition (EMT) of gastric cancer. In our study, we confirmed that the expression level of VGLL4 was down-regulated in gastric cancer tissues, and reduced VGLL4 expression levels inhibited apoptosis and promoted proliferation, migration, and invasion. Additionally, we found a phenomenon that VGLL4 was associated with the change in nuclear location of β-catenin, which suggested that β-catenin was a significant downstream factor of VGLL4. These results suggest that VGLL4 suppressed EMT in part via negative regulation of Wnt/β-catenin signaling pathway. Taken together, our study demonstrated that VGLL4 is important in the process of suppressing tumor progression of gastric cancer and provided a potential therapeutic strategy for gastric cancer.

Simultaneous silencing of XIAP and survivin causes partial mesenchymal-epithelial transition of human pancreatic cancer cells via the PTEN/PI3K/Akt pathway

Pancreatic cancer has one of the highest mortality rates among malignant tumors and is characterized by rapid invasion, early metastasis and chemoresistance. X-linked inhibitor of apoptosis (XIAP) and survivin are two of the most important members of the IAP family. Previous studies have shown that XIAP and survivin were overexpressed in pancreatic cancer and were closely associated with cell proliferation and chemoresistance to gemcitabine. In the present study, stable inhibition of XIAP and survivin in Panc-1 cells was performed using lentivirus-carried short hairpin RNAs. The expression of XIAP, survivin, E-cadherin, Slug, phosphatase and tensin homolog (PTEN) and phosphorylated Akt was then measured. In addition, cell proliferation, apoptosis, invasion and migration were assessed. The results showed that stable inhibition of XIAP and survivin expression in Panc-1 cells significantly reduced cell proliferation, increased apoptosis and partially reversed the epithelial-mesenchymal transition (EMT). Furthermore, the results of the present study demonstrated that the partial reversal of the EMT was accompanied by inhibited cell invasion and migration as well as increased chemosensitivity to gemcitabine in pancreatic cancer cells; this was indicated to be mediated via the PTEN/phosphatidylinositol 3-kinase/Akt signaling pathway. In conclusion, these results suggested that simultaneous inhibition of XIAP and survivin may be a promising strategy for the treatment of pancreatic cancer.

HES 1 is essential for chemoresistance induced by stellate cells and is associated with poor prognosis in pancreatic cancer

The role of pancreatic stellate cells (PSCs) has been established in many studies. However, the potential mechanism for the chemoresistance induced by PSCs has not been fully elucidated. In the present study, human pancreatic cancer cell lines were directly or indirectly co-cultured with PSCs. The inhibition rate and IC50 values were assessed to determine the ability of chemoresistance. RT-PCR and western blot analysis were used to evaluate Hes 1 and Jagged 1 expression before and after co-culture with PSCs. To determine the relationship between Hes 1 expression and survival in pancreatic cancer patients, Kaplan-Meier survival analysis was performed. PSCs promoted the expression of Hes 1 in both PANC-1 and BxPC-3 cell lines and induced chemoresistance to gemcitabine. A Notch signaling pathway inhibitor (L1790) and Hes 1 siRNA reversed the chemoresistance induced by PSCs. In 72 resected pancreatic cancer patients, high Hes 1 expression was observed in 34 patients with shorter overall and progression-free survival times. In conclusion, Hes 1 is essential for chemoresistance induced by PSCs and is associated with poor prognosis in pancreatic cancer patients. Therapy targeting the Notch signaling pathway may reverse chemoresistance and improve survival in patients with pancreatic cancer.

A phase I dose-escalation study of eribulin and S-1 for metastatic breast cancer

Background:

We evaluated the safety, maximum-tolerated dose (MTD), pharmacokinetics, recommended dose for phase II (P2RD), and preliminary anticancer activity of a combination eribulin and S-1 therapeutic in metastatic breast cancer patients pretreated with anthracycline and taxane.

Method:

Patients aged 20–74 years were recruited. In level 1, patients received S-1 (65 mg m⁻²) from day 1 to 14, and eribulin (1.1 mg m⁻²) on day 1 and 8 in a 21-day cycle. In level 2, eribulin was increased to 1.4 mg m⁻². In level 3, S-1 was increased to 80 mg m⁻².

Results:

Twelve patients were enrolled into three cohorts. Planned dose escalation was completed, with one case exhibiting dose-limiting toxicity (grade 3 hypokalaemia) at level 3, without reaching the MTD. The P2RD was determined to be level 2 (eribulin 1.4 mg m⁻² and S-1 65 mg m⁻²). The most common grade 3 or 4 toxicity was neutropenia (83.3%), followed by febrile neutropenia (25.0%). Five of eleven patients (41.7%) with measurable disease had a partial response. Pharmacokinetics were characterised by dose-dependent elimination and nonlinear exposure.

Conclusion:

Dose level 3 was not tolerated owing to febrile neutropenia development. Thus, intermediate dose level 2 was recommended for further evaluation. Preliminary antitumour activity warrants further investigation in this setting.

Notch1 signaling regulates the epithelial-mesenchymal transition and invasion of breast cancer in a Slug-dependent manner

BACKGROUND

The epithelial-mesenchymal transition (EMT) is crucial for the invasion and metastasis of breast cancer. However, how Notch signaling regulates the EMT process and invasion in breast cancer remains largely unknown.

METHODS

The impact of Notch1 silencing by specific shRNAs on the EMT and invasion of human breast cancer MCF-7 and MDA-MB-231 cells as well as xenografts was tested by western blot, real-time polymerase chain reaction (RT-PCR), immunofluorescence, transwell, and immunohistochemistry assays. The effect of Slug silencing or upregulation on the EMT and invasion of breast cancer cells was analyzed, and the effect of Notch1 signaling on Slug expression was determined by the luciferase reporter assay.

RESULTS

The Notch1 intracellular domain (N1ICD) and Jagged1 were expressed in breast cancer cells. Notch1 silencing reversed the spontaneous EMT process and inhibited the migration and invasion of breast cancer cells and the growth of xenograft breast cancers. The expression of N1ICD was upregulated significantly by Jagged1-mediated Notch signaling activation. Moreover, Jagged1-mediated Notch signaling promoted the EMT process, migration, and invasion of breast cancer cells, which were abrogated by Notch silencing. Furthermore, the N1ICD positively regulated the Slug expression by inducing Slug promoter activation. Importantly, the knockdown of Slug weakened the invasion ability of breast cancer cells and reversed the Jagged1-induced EMT process with significantly decreased expression of vimentin and increased expression of E-cadherin. In addition, Slug overexpression restored the Notch1 knockdown-suppressed EMT process.

CONCLUSIONS

Our novel data indicate that Notch signaling positively regulates the EMT, invasion, and growth of breast cancer cells by inducing Slug expression. The Notch1-Slug signaling axis may represent a potential therapeutic target for breast cancer therapy.

Involvement of epithelial to mesenchymal transition in the development of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an intractable disease as a result of its rapid dissemination and resistance to conventional chemotherapy and radiotherapy. Surgical resection is the only curative therapy, but most of the tumors are unresectable at the time of diagnosis. The molecular mechanisms underlying the biological aggressiveness of this tumor type remain to be clarified. Epithelial to mesenchymal transition (EMT) is a developmental process that leads the phenotype shift from an epithelial morphology to a motile, fibroblast-like morphology. Recent studies showed that EMT is involved in the invasion and metastasis of many types of carcinomas including PDAC. In addition, PDAC cells with the EMT phenotype also exhibit chemoresistance and the cancer stem cell property. Various factors such as cytokines, growth factors, or transcriptional factors were found to promote the EMT program in PDAC cells. In this review, we summarize the current knowledge about the EMT in PDAC cells, focusing on the involvement of this process and its regulatory molecules including microRNA during the development of PDAC cells.

Pancreatic ductal adenocarcinoma: From genetics to biology to radiobiology to oncoimmunology and all the way back to the clinic

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death. Despite improvements in the clinical management, the prognosis of PDAC remains dismal. In the present comprehensive review, we will examine the knowledge of PDAC genetics and the new insights into human genome sequencing and clonal evolution. Additionally, the biology and the role of the stroma in tumour progression and response to treatment will be presented. Furthermore, we will describe the evidence on tumour chemoresistance and radioresistance and will provide an overview on the recent advances in PDAC metabolism and circulating tumour cells. Next, we will explore the characteristics and merits of the different mouse models of PDAC. The inflammatory milieu and the immunosuppressive microenvironment mediate tumour initiation and treatment failure. Hence, we will also review the inflammatory and immune escaping mechanisms and the new immunotherapies tested in PDAC. A better understanding of the different mechanisms of tumour formation and progression will help us to identify the best targets for testing in future clinical studies of PDAC.

Epithelial-mesenchymal transition in pancreatic cancer: Is it a clinically significant factor?

Pancreatic cancer is one of the most aggressive solid malignancies. This aggressiveness is partly attributable to extensive local tumor invasion and early systemic dissemination as well as resistance to chemotherapy. Epithelial-mesenchymal transition (EMT) plays fundamental roles in embryonic development and in the differentiation of normal tissues and organs. EMT also plays critical roles in tumor formation, dissemination and drug resistance in pancreatic cancer. Emerging data suggest that inhibiting EMT may reverse the EMT phenotype and enhance the efficacy of chemotherapeutic agents against pancreatic cancer cells. Thus, an understanding of the molecular biology of EMT in pancreatic cancer may provide insights into the mechanisms of tumor invasion and metastatic progression and facilitate the development of alternative therapeutic approaches to improve the treatment outcomes for patients suffering from pancreatic cancer.

Gemcitabine resistant pancreatic cancer cell lines acquire an invasive phenotype with collateral hypersensitivity to histone deacetylase inhibitors

Gemcitabine based treatment is currently a standard first line treatment for patients with advanced pancreatic cancer, however overall survival remains poor, and few options are available for patients that fail gemcitabine based therapy. To identify potential molecular targets in gemcitabine refractory pancreatic cancer, we developed a series of gemcitabine resistant (GR) cell lines. Initial drug exposure selected for an early resistant phenotype that was independent of drug metabolic pathways. Prolonged drug selection pressure after 16 weeks, led to an induction of cytidine deaminase (CDA) and enhanced drug detoxification. Cross resistance profiles demonstrate approximately 100-fold cross resistance to the pyrimidine nucleoside cytarabine, but no resistance to the same in class agents, azacytidine and decitabine. GR cell lines demonstrated a dose dependent collateral hypersensitivity to class I and II histone deacetylase (HDAC) inhibitors and decreased expression of 3 different global heterochromatin marks, as detected by H4K20me3, H3K9me3 and H3K27me3. Cell morphology of the drug resistant cell lines demonstrated a fibroblastic type appearance with loss of cell-cell junctions and an altered microarray expression pattern, using Gene Ontology (GO) annotation, consistent with progression to an invasive phenotype. Of particular note, the gemcitabine resistant cell lines displayed up to a 15 fold increase in invasive potential that directly correlates with the level of gemcitabine resistance. These findings suggest a mechanistic relationship between chemoresistance and metastatic potential in pancreatic carcinoma and provide evidence for molecular pathways that may be exploited to develop therapeutic strategies for refractory pancreatic cancer.

miRNAs in pancreatic cancer: therapeutic potential, delivery challenges and strategies

Pancreatic ductal adenocarcinoma (PDAC) is a severe pancreatic malignancy and is predicted to victimize 1.5% of men and women during their lifetime (Cancer statistics: SEER stat fact sheet, National Cancer Institute, 2014). miRNAs have emerged as a promising prognostic, diagnostic and therapeutic tool to fight against pancreatic cancer. miRNAs could modulate gene expression by imperfect base-pairing with target mRNA and hence provide means to fine-tune multiple genes simultaneously and alter various signaling pathways associated with the disease. This exceptional miRNA feature has provided a paradigm shift from the conventional one drug one target concept to one drug multiple target theory. However, in vivo miRNA delivery is not fully realized due to challenges posed by this special class of therapeutic molecules, which involves thorough understanding of the biogenesis and physicochemical properties of miRNA and delivery carriers along with the pathophysiology of the PDAC. This review highlights the delivery strategies of miRNA modulators (mimic/inhibitor) in cancer with special emphasis on PDAC since successful delivery of miRNA in vivo constitutes the major challenge in clinical translation of this promising class of therapeutics.

Expression of ERCC1, TYMS, RRM1, TUBB3, non-muscle myosin II, myoglobin and MyoD1 in lung adenocarcinoma pleural effusions predicts survival in patients receiving platinum-based chemotherapy

The association between the expression of excision repair cross‑complementing gene 1 (ERCC1), thymidylate synthase (TYMS), ribonuleotide reductase M1 (RRM1), βIII‑tubulin (TUBB3), non‑muscle myosin II, myoglobin and MyoD1 in metastatic lung adenocarcinoma, and clinical outcomes with platinum‑based chemotherapy treatment is not well‑established. Recently, increasing attention has been focused on the involvement of ERCC1, TYMS, RRM1 and TUBB3 in the development of drug resistance. There has been less research into the role of muscle myosin II, myoglobin and MyoD1 in the pathogenesis of lung cancer, although these genes are known to have important functions within tumor cells. In the current study, malignant pleural effusion from 116 patients with untreated lung adenocarcinoma diagnosed between 2011 and 2012, were collected. The protein expression levels of ERCC1, TYMS, RRM1 and TUBB3 were evaluated with immunocytochemistry and western blot analysis. The expression levels of non‑muscle myosin II, myoglobin and MyoD1 were measured in a subset of 50 patients, treated with platinum‑based chemotherapy. The association of each of these seven factors with one another, as well as with patient survival were analyzed. Immunohistochemistry demonstrated that the percentage of pleural fluid samples from patients with lung adenocarcinoma expressing ERCC1, TYMS, RRM1 and TUBB3 was 37, 36.2, 82.7 and 69.8%, respectively. In the subset of 50 patients in whom the remaining factors were analyzed, the percentage expressing non‑muscle myosin II was 48%, for myoglobin the figure was 40% and for MyoD1 it was 38%. There was a positive correlation between each pair of the above seven molecules with the exception of TYMS and RRM1. Expression of ERCC1, TYMS, TUBB3, non‑muscle myosin II, myoglobin and MyoD1 genes was associated with decreased survival in patients with metastatic lung adenocarcinoma. Expression of ERCC1, TYMS, TUBB3, non‑muscle myosin II, myoglobin and MyoD1 was also associated with decreased survival rates of patients with lung adenocarcinoma treated with platinum‑based chemotherapy. These factors may be used as clinical biomarkers to predict the biological behavior and chemoresistance of tumor cells, and the survival of patients with lung carcinoma.

Notch signaling and EMT in non-small cell lung cancer: biological significance and therapeutic application

Through epithelial-mesenchymal transition (EMT), cancer cells acquire enhanced ability of migration and invasion, stem cell like characteristics and therapeutic resistance. Notch signaling regulates cell-cell connection, cell polarity and motility during organ development. Recent studies demonstrate that Notch signaling plays an important role in lung cancer initiation and cross-talks with several transcriptional factors to enhance EMT, contributing to the progression of non-small cell lung cancer (NSCLC). Correspondingly, blocking of Notch signaling inhibits NSCLC migration and tumor growth by reversing EMT. Clinical trials have showed promising effect in some cancer patients received treatment with Notch1 inhibitor. This review attempts to provide an overview of the Notch signal in NSCLC: its biological significance and therapeutic application.

Pancreatic cancer cells express CD44 variant 9 and multidrug resistance protein 1 during mitosis

Pancreatic cancer is one of the most lethal cancers with high metastatic potential and strong chemoresistance. Its intractable natures are attributed to high robustness in tumor cells for their survival. We demonstrate here that pancreatic cancer cells (PCCs) with an epithelial phenotype upregulate cell surface expression of CD44 variant 9 (CD44v9), an important cancer stem cell marker, during the mitotic phases of the cell cycle. Of five human CD44(+) PCC lines examined, three cell lines, PCI-24, PCI-43 and PCI-55, expressed E-cadherin and CD44 variants, suggesting that they have an epithelial phenotype. By contrast, PANC-1 and MIA PaCa-2 cells expressed vimentin and ZEB1, suggesting that they have a mesenchymal phenotype. PCCs with an epithelial phenotype upregulated cell surface expression of CD44v9 in prophase, metaphase, anaphase and telophase and downregulated CD44v9 expression in late-telophase, cytokinesis and interphase. Sorted CD44v9-negative PCI-55 cells resumed CD44v9 expression when they re-entered the mitotic stage. Interestingly, CD44v9(bright) mitotic cells expressed multidrug resistance protein 1 (MDR1) intracellularly. Upregulated expression of CD44v9 and MDR1 might contribute to the intractable nature of PCCs with high proliferative activity.

Transcriptional factor snail controls tumor neovascularization, growth and metastasis in mouse model of human ovarian carcinoma

BACKGROUND

Snail, a transcriptional factor and repressor of E-cadherin is well known for its role in cellular invasion. It can regulate epithelial to mesenchymal transition (EMT) during embryonic development and in epithelial cells. Snail also mediates tumor progression and metastases. Silencing of Snail and its associate member Slug in human A2780 ovarian epithelial carcinoma cell line was investigated to identify its role in tumor neovascularization.

METHODS

Live cell sialidase, WST-1 cell viability and immunohistochemistry assays were used to evaluate sialidase activity, cell survival and the expression levels of tumor E-cadherin, N-cadherin, VE-cadherin, and host endothelial CD31+(PECAM-1) cells in archived paraffin-embedded ovarian A2780, A2780 Snail shRNA GIPZ lentiviral knockdown (KD) and A2780 Slug shRNA GIPZ lentiviral KD tumors grown in RAGxCγ double mutant mice.

RESULTS

Oseltamivir phosphate (OP), anti-Neu1 antibodies and MMP-9 specific inhibitor blocked Neu1 activity associated with epidermal growth factor (EGF) stimulated A2780 ovarian epithelial carcinoma cells. Silencing Snail in A2780 cells abrogated the Neu1 activity following EGF stimulation of the cells compared to A2780 and A2780 Slug KD cells. OP treatment of A2780 and cisplatin-resistant A2780cis cells reproducibly and dose-dependently abated the cell viability with a LD50 of 7 and 4 μm, respectively, after 48 h of incubation. Heterotopic xenografts of A2780 and A2780 Slug KD tumors developed robust and bloody tumor vascularization in RAG2xCγ double mutant mice. OP treatment at 50 mg/kg daily intraperitoneally did not significantly impede A2780 tumor growth rate but did cause a significant reduction of lung metastases compared with the untreated and OP 30mg/kg cohorts. Silencing Snail in A2780 tumor cells completely abrogated tumor vascularization, tumor growth and spread to the lungs in RAGxCγ double mutant mice. A2780 and A2780 Slug KD tumors expressed high levels of human N- and VE-cadherins, and host CD31+ endothelial cells, while A2780 Snail KD tumors expressed E-cadherin and reduced host CD31+ cells. OP 50mg/kg cohort tumors had reduced numbers of host CD31+ cells compared to a higher expression levels of CD31+ cells in tumors from the untreated control and OP 30mg/kg cohorts.

CONCLUSION

Snail transcriptional factor is an important intermediate player in human ovarian tumor neovascularization.

Epithelial Notch signaling is a limiting step for pancreatic carcinogenesis

Background

Pancreatic cancer is one of the deadliest human malignancies, with few therapeutic options. Re-activation of embryonic signaling pathways is commonly in human pancreatic cancer and provided rationale to explore inhibition of these pathways therapeutically. Notch signaling is important during pancreatic development, and it is re-activated in pancreatic cancer. The functional role of Notch signaling during pancreatic carcinogenesis has been previously characterized using both genetic and drug-based approaches. However, contrasting findings were reported based on the study design. In fact, Notch signaling has been proposed to act as tumor-promoter or tumor-suppressor. Given the availability of Notch inhibitors in the clinic, understanding how this signaling pathway contributes to pancreatic carcinogenesis has important therapeutic implications. Here, we interrogated the role of Notch signaling specifically in the epithelial compartment of the pancreas, in the context of a genetically engineered mouse model of pancreatic cancer.

Methods

To inhibit Notch signaling in the pancreas epithelium, we crossed a mouse model of pancreatic cancer based on pancreas-specific expression of mutant Kras with a transgenic mouse that conditionally expresses a dominant negative form of the Mastermind-like 1 gene. MAML is an essential co-activator of the canonical Notch signaling-mediated transcription. DNMAML encodes a truncated MAML protein that represses all canonical Notch mediated transcription in a cell autonomous manner, independent of which Notch receptor is activated. As a result, in mice co-expressing mutant Kras and DNMAML, Notch signaling is inhibited specifically in the epithelium upon Cre-mediated recombination. We explored the effect of epithelial-specific DNMAML expression on Kras-driven carcinogenesis both during normal aging and following the induction of acute pancreatitis.

Results

We find that DNMAML expression efficiently inhibits epithelial Notch signaling and delays PanIN formation. However, over time, loss of Notch inhibition allows PanIN formation and progression.

Conclusions

Epithelial-specific Notch signaling is important for PanIN initiation. Our findings indicate that PanIN formation can only occur upon loss of epithelial Notch inhibition, thus supporting an essential role of this signaling pathway during pancreatic carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-862) contains supplementary material, which is available to authorized users.

Genetic and non-genetic instability in tumor progression: link between the fitness landscape and the epigenetic landscape of cancer cells

Genetic instability is invoked in explaining the cell phenotype changes that take place during cancer progression. However, the coexistence of a vast diversity of distinct clones, most prominently visible in the form of non-clonal chromosomal aberrations, suggests that Darwinian selection of mutant cells is not operating at maximal efficacy. Conversely, non-genetic instability of cancer cells must also be considered. Such mutation-independent instability of cell states is most prosaically manifest in the phenotypic heterogeneity within clonal cell populations or in the reversible switching between immature "cancer stem cell-like" and more differentiated states. How are genetic and non-genetic instability related to each other? Here, we review basic theoretical foundations and offer a dynamical systems perspective in which cancer is the inevitable pathological manifestation of modes of malfunction that are immanent to the complex gene regulatory network of the genome. We explain in an accessible, qualitative, and permissively simplified manner the mathematical basis for the "epigenetic landscape" and how the latter relates to the better known "fitness landscape." We show that these two classical metaphors have a formal basis. By combining these two landscape concepts, we unite development and somatic evolution as the drivers of the relentless increase in malignancy. Herein, the cancer cells are pushed toward cancer attractors in the evolutionarily unused regions of the epigenetic landscape that encode more and more "dedifferentiated" states as a consequence of both genetic (mutagenic) and non-genetic (regulatory) perturbations-including therapy. This would explain why for the cancer cell, the principle of "What does not kill me makes me stronger" is as much a driving force in tumor progression and development of drug resistance as the simple principle of "survival of the fittest."

Stem cell signature in glioblastoma: therapeutic development for a moving target

Tumor heterogeneity of adult high-grade glioma (HGG) is recognized in 3 major subtypes based on core gene signatures. However, the molecular signatures and clinical implications of glioma stem cells (GSCs) in individual HGG subtypes remain poorly characterized. Recently genome-wide transcriptional analysis identified two mutually exclusive GSC subtypes with distinct dysregulated signaling and metabolic pathways. Analysis of genetic profiles and phenotypic assays distinguished proneural (PN) from mesenchymal (MES) GSCs and revealed a striking correlation with the corresponding PN or MES HGGs. Similar to HGGs with a MES signature, MES GSCs display more aggressive phenotypes both in vitro and in vivo. Furthermore, MES GSCs are markedly resistant to radiation as compared with PN GSCs, consistent with the relative radiation resistance of MES GBM compared with other subtypes. A systems biology approach has identified a set of transcription factors as the master regulators for the MES signature. Metabolic reprogramming in MES GSCs has also been noticed with the prominent activation of the glycolytic pathway, comprising aldehyde dehydrogenase (ALDH) family genes. This review summarizes recent progress in the characterization of the molecular signature in distinct HGG and GSC subtypes and plasticity between different GSC subtypes as well as between GSCs and non-GSCs in HGG tumors. Clinical implications of the translational GSC research are also discussed.

Mutated K-ras activates CDK8 to stimulate the epithelial-to-mesenchymal transition in pancreatic cancer in part via the Wnt/β-catenin signaling pathway

Cyclin-dependent kinase 8 (CDK8), a gene encoding the cyclin-dependent kinase (CDK) component of the Mediator complex, is known as a colon cancer oncogene. Our recent study showed that CDK8 plays an important role in the formation of pancreatic cancer, but the CDK8 expression levels were not completely identical in different pancreatic cancer samples. The level of CDK8 expression depended on whether the K-ras gene was mutated; its expression was much higher in samples carrying a K-ras mutation than in wild-type K-ras samples. Moreover, CDK8 expression was reduced following mutated K-ras knockdown in K-ras-mutated pancreatic cancer cells, whereas CDK8 expression was increased following expression of mutated K-ras in wild-type K-ras cells. Our study demonstrates that mutated K-ras stimulates CDK8 expression, possibly by regulating HIF-1α, and both CDK8 and mutated K-ras were confirmed to promote cell proliferation and prevent apoptosis in vitro. Additionally, we found that both CDK8 and mutated K-ras promote the invasion and migration of pancreatic cancer cells via the positive regulation of the Wnt/β-catenin signaling pathway, thereby increasing the expression of Snail1 and ZEB1, which act as important stimulating factors of the epithelial-to-mesenchymal transition (EMT). Finally, knockdown of either CDK8 or mutated K-ras contributed to attenuated pancreatic cancer growth in BALB/c nude mice. In conclusion, these findings demonstrate that mutated K-ras promotes CDK8 expression and that the regulatory effects of CDK8 on the EMT are partially attributed to the Wnt/β-catenin signaling pathway.

Up-regulation of S100A16 expression promotes epithelial-mesenchymal transition via Notch1 pathway in breast cancer

BACKGROUND

Our previous studies demonstrated that S100A16 promotes adipogenesis and is involved in weight gain attenuation induced by dietary calcium. Till now, the function of S100A16 in the breast cancer remains to be elucidated.

RESULTS

In this study, we observed that S100A16 was expressed in higher levels in human breast cancer tissues compared with paired adjacent non-cancerous tissues. Further examination showed that overexpression of S100A16 in MCF-7 cells could increase cell proliferation and colony formation. One major mechanistic change was that S100A16 was able to up-regulate the transcription factors Notch1, ZEB1, and ZEB2, which had the capacities to directly repress the expression of epithelial markers E-cadherin and β-catenin but increase mesenchymal markers N-cadherin and vimentin, a characterized phenotype of epithelial-mensenchymal transition (EMT). In addition to display with morphologic change, migration and invasion were increased in S100A16 over-expressed MCF-7 cells. Importantly, knockdown of Notch1 by specific siRNA could reverse the EMT induced by S100A16 overexpression, which confirmed that Notch1 played a critical role in the process of EMT induced by S100A16.

CONCLUSIONS

All together, our data indicated that S100A16 had a potential function to regulate some embryonic transcription factors to promote EMT in breast cancer cells which may be an important target site for the therapy of breast cancer.

Analysis of a cytoskeleton-associated kinase PEAK1 and E-cadherin in gastric cancer

The expression of pseudopodium-enriched atypical kinase 1(PEAK1) has been studied in human cancers. However, their roles in gastric cancer are still unknown. In this study, gastric cancer tissue microarrays were constructed with 159 gastric cancer tissue samples, 150 non-neoplastic gastric epithelium specimens and 152 lymph node samples. Immunohistochemical staining for PEAK1 and E-cadherin was performed. Our study found negative expression of PEAK1 in 113 of 159 (71.1%) gastric cancers, in 46 of 150 (30.7%) non-neoplastic gastric epithelium tissues and in 69 of 94 (73.4%) metastatic lymph nodes. Negative expression of PEAK1 and E-cadherin associated with tumor grading, depth of invasion, lymph node metastases, pTNM stage and macroscopic type. Patients with either positive PEAK1 or E-cadherin expression had a significantly higher survival than those with negative expression. When combined, PEAK1(-)/E-cadherin(-) had a significantly poor prognosis than the rest of the patients. The expression of PEAK1 protein was positively correlated with E-cadherin in cancer tissues. Cox regression analyses showed that PEAK1, E-cadherin and PEAK1(-)/E-cadherin(-) were independent predictors of overall survival. In conclusion, our findings suggest that loss of PEAK1 may play an important role in carcinogenesis and development of gastric cancer through activating epithelial to mesenchymal transition.

MiR200-upregulated Vasohibin 2 promotes the malignant transformation of tumors by inducing epithelial-mesenchymal transition in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) typically relies on tumor transformation and angiogenesis for its malignant behavior, including growth and metastasis. Previously, we reported that Vasohibin2 (VASH2) is preferentially expressed in hepatocellular carcinoma (HCC) tumor tissues and promotes angiogenesis. Here, we further investigated the role of VASH2 in HCC tumor progression.

Results

Bioinformatics analyses and luciferase reporter gene assays confirmed the post-transcriptional regulation of VASH2 by miR-200a/b/c. We then used HepG2 and Hep3B cells, two representative hepatic cancer cell lines, to examine the role of VASH2 in tumors. VASH2 knockdown in HepG2 cells inhibited epithelial-mesenchymal transition (EMT), but VASH2 overexpression in Hep3B cells promoted EMT. Western blot analyses showed that VASH2 promoted EMT through the ZEB1/2 pathway.

Conclusion

VASH2 promoted invasion, reduced apoptosis and increased the proportion of stem cells in vitro and in vivo. These results indicated that VASH2 expression in HCC cells promotes the malignant transformation of tumors by inducing EMT.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-014-0062-x) contains supplementary material, which is available to authorized users.

The network of epithelial-mesenchymal transition: potential new targets for tumor resistance

PURPOSE

In multiple cell metazoans, the ability of polarized epithelial cells to convert to motile mesenchymal cells in order to relocate to another location is governed by a unique process termed epithelial-mesenchymal transition (EMT). While being an essential process of cellular plasticity for normal tissue and organ developments, EMT is found to be involved in an array of malignant phenotypes of tumor cells including proliferation and invasion, angiogenesis, stemness of cancer cells and resistance to chemo-radiotherapy. Although EMT is being extensively studied and demonstrated to play a key role in tumor metastasis and in sustaining tumor hallmarks, there is a lack of clear picture of the overall EMT signaling network, wavering the potential clinical trials targeting EMT.

METHODS

In this review, we highlight the potential key therapeutic targets of EMT linked with tumor aggressiveness, hypoxia, angiogenesis and cancer stem cells, emphasizing on an emerging EMT-associated NF-κB/HER2/STAT3 pathway in radioresistance of breast cancer stem cells.

RESULTS

Further definition of cancer stem cell repopulation due to EMT-controlled tumor microenvironment will help to understand how tumors exploit the EMT mechanisms for their survival and expansion advantages.

CONCLUSIONS

The knowledge of EMT will offer more effective targets in clinical trials to treat therapy-resistant metastatic lesions.

Altered gene products involved in the malignant reprogramming of cancer stem/progenitor cells and multitargeted therapies

Recent studies in the field of cancer stem cells have revealed that the alterations in key gene products involved in the epithelial-mesenchymal transition (EMT) program, altered metabolic pathways such as enhanced glycolysis, lipogenesis and/or autophagy and treatment resistance may occur in cancer stem/progenitor cells and their progenies during cancer progression. Particularly, the sustained activation of diverse developmental cascades such as hedgehog, epidermal growth factor receptor (EGFR), Wnt/β-catenin, Notch, transforming growth factor-β (TGF-β)/TGF-βR receptors and/or stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) can play critical functions for high self-renewal potential, survival, invasion and metastases of cancer stem/progenitor cells and their progenies. It has also been observed that cancer cells may be reprogrammed to re-express different pluripotency-associated stem cell-like markers such as Myc, Oct-3/4, Nanog and Sox-2 along the EMT process and under stressful and hypoxic conditions. Moreover, the enhanced expression and/or activities of some drug resistance-associated molecules such as Bcl-2, Akt/molecular target of rapamycin (mTOR), nuclear factor-kappaB (NF-κB), hypoxia-inducible factors (HIFs), macrophage inhibitory cytokine-1 (MIC-1) and ATP-binding cassette (ABC) multidrug transporters frequently occur in cancer cells during cancer progression and metastases. These molecular events may cooperate for the survival and acquisition of a more aggressive and migratory behavior by cancer stem/progenitor cells and their progenies during cancer transition to metastatic and recurrent disease states. Of therapeutic interest, these altered gene products may also be exploited as molecular biomarkers and therapeutic targets to develop novel multitargeted strategies for improving current cancer therapies and preventing disease relapse.