Cancer stem-like cells enriched in Panc-1 spheres possess increased migration ability and resistance to gemcitabine. Int J Mol Sci. 2011;12:1595-1604. [PMID: 21673909 PMCID: PMC3111620 DOI: 10.3390/ijms12031595]

High-density lipoprotein-based nanoplatform reprograms tumor microenvironment and enhances chemotherapy against pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is highly aggressive, with limited success in traditional therapies due to the fibrotic, immunosuppressive, pro-metastatic tumor microenvironment (TME), which collectively impede the drug accumulation and accelerate the tumor progression. In this work, we developed a PDAC-customized nutrient-mimicking reconstituted high-density lipoprotein (rHDL) capable of efficiently co-encapsulate versatile TME regulating cannabidiol and cytotoxic gemcitabine to simultaneously reprogram TME while suppressing PDAC progression. Specifically, a small-sized, nutrient-like rHDL was constructed to realize deep PDAC parenchyma penetration and efficient intra-tumoral uptake. Next, natural herbal compound cannabidiol was screened and incorporated into rHDL to regulate TME via attenuating fibrosis, reliving immunosuppression and mitigating metastatic tendency. At last, gemcitabine, the PDAC gold standard first-line therapy was co-delivered by the PDAC-customized rHDL to overcome drug resistance and amplify its PDAC suppression. Our findings demonstrate the feasibility of an integrated multi-stage TME regulation strategy for improved PDAC therapy, and might represent a modality in promoting chemotherapy against PDAC.

Investigation of the synergistic effect of metformin and FX11 on PANC-1 cell lines

BACKGROUND

Pancreatic cancer is among the most aggressive and malignant tumors and is a leading cause of cancer-related mortality. It is characterized by its metabolic Warburg effect and glucose dependence. Aerobic glycolysis is a key feature of metabolic reprogramming in cancer cells. This study investigates the combined effect of metformin and FX11, hypothesizing that disrupting cancer cell energetics through complementary mechanisms may result in a synergistic therapeutic effect. The combination of metformin and FX11 affects the axis that regulates vital functions in cancer cells; thus, the uncontrolled growth of tumor cells, especially those that use a lactose-dependent energy pathway, can be controlled. Several in vitro experiments were conducted to evaluate this hypothesis. PANC-1 cell proliferation was assessed using an MTS assay, lactate levels were measured via an LDH assay, and apoptosis was determined using a flow cytometry-based PE-annexin V assay. The downstream effects of metformin and FX11 treatment were evaluated via western blot analysis.

RESULTS

The findings of this study revealed that metformin and FX11 significantly decreased the viability of PANC-1 cells when used in combination, and this effect was achieved by significantly affecting the energy mechanism of the cells through the AMPKα axis. Furthermore, the lactate levels in PANC1 cells co-treated with metformin and FX11 were significantly decreased, while the increased cellular stress led the cells to apoptosis.

CONCLUSIONS

Compared with metformin treatment alone, the combination treatment of metformin and FX11 stimulates cellular stress in pancreatic cancer and targets various energy processes that encourage cancer cells to undergo apoptosis. This study provides a novel therapeutic strategy for the treatment of pancreatic cancer.

SOX2 promotes the glycolysis process to accelerate cervical cancer progression by regulating the expression of HK2

BACKGROUND

Cervical cancer is a major health burden in females worldwide, available studies indicated that sex-determining region Y-box 2 (SOX2) is closely related to the malignant phenotypes of multiple cancers including cervical cancer. However, the underlying mechanisms were blurred.

EXPERIMENTAL PROCEDURES

A bioinformatics analysis was conducted to investigate the clinical correlation between SOX2 and cervical cancer. Transient transfection and lentivirus infection were utilized to achieve overexpression and knockdown of SOX2, respectively. The role of SOX2 in cervical cancer was confirmed by transwell and colony-forming assays. Immunoblot, dual-luciferase reporter, chromatin immunoprecipitation (ChIP), and biochemical experiments were employed. In addition, the xenograft models and immunohistochemistry (IHC) experiments were performed to validate the findings in vivo.

RESULTS

The expression of SOX2 was significantly positively associated with the cell migration, invasion, and colony-forming abilities of cervical cancer cells. The following immunoblots revealed that the SOX2-induced malignant phenotypes might be related to the glycolysis process, since overexpressing SOX2 significantly promoted the hexokinase 2 (HK2) and glucose transporter-1 (GLUT1) expression, and increased the content of glucose and lactic acid. The further dual-luciferase reporter and ChIP experiments confirmed a binding relationship between SOX2 and HK2 promoter. More importantly, overexpressing SOX2 promoted tumor growth concomitant with a hyper-expression of HK2 and GLUT1 in xenograft tumor tissues, yet the treatment of glycolysis inhibitor significantly reversed those outcomes.

CONCLUSION

SOX2 promotes the malignant progression of cervical cancer by facilitating glycolysis.

Insights and therapeutic advances in pancreatic cancer: the role of electron microscopy in decoding the tumor microenvironment

Pancreatic cancer is one of the most lethal cancers, with a 5-year overall survival rate of less than 10%. Despite the development of novel therapies in recent decades, current chemotherapeutic strategies offer limited clinical benefits due to the high heterogeneity and desmoplastic tumor microenvironment (TME) of pancreatic cancer as well as inefficient drug penetration. Antibody- and nucleic acid-based targeting therapies have emerged as strong contenders in pancreatic cancer drug discovery. Numerous studies have shown that these strategies can significantly enhance drug accumulation in tumors while reducing systemic toxicity. Additionally, electron microscopy (EM) has been a critical tool for high-resolution analysis of the TME, providing insights into the ultrastructural changes associated with pancreatic cancer progression and treatment responses. This review traces the current and technological advances in EM, particularly the development of ultramicrotomy and improvements in sample preparation that have facilitated the detailed visualization of cellular and extracellular components of the TME. This review highlights the contribution of EM in assessing the efficacy of therapeutic agents, from revealing apoptotic changes to characterizing the effects of novel compounds like ionophore antibiotic gramicidin A on cellular ultrastructures. Moreover, the review delves into the potential of EM in studying the interactions between the tumor microbiome and cancer cell migration, as well as in aiding the development of targeted therapies like antibody-drug conjugates (ADCs) and aptamer-drug conjugates (ApDCs).

The Effect of Intratumor Heterogeneity in Pancreatic Ductal Adenocarcinoma Progression and Treatment

BACKGROUND AND OBJECTIVES

Pancreatic cancer is one of the most lethal malignancies. Even though many substantial improvements in the survival rates for other major cancer forms were made, pancreatic cancer survival rates have remained relatively unchanged since the 1960s. Even more, no standard classification system for pancreatic cancer is based on cellular biomarkers. This review will discuss and provide updates about the role of stem cells in the progression of PC, the genetic changes associated with it, and the promising biomarkers for diagnosis.

MATERIALS AND METHODS

The search process used PubMed, Cochrane Library, and Scopus databases to identify the relevant and related articles. Articles had to be published in English to be considered.

RESULTS

The increasing number of studies in recent years has revealed that the diversity of cancer-associated fibroblasts is far greater than previously acknowledged, which highlights the need for further research to better understand the various cancer-associated fibroblast subpopulations. Despite the huge diversity in pancreatic cancer, some common features can be noted to be shared among patients. Mutations involving CDKN2, P53, and K-RAS can be seen in a big number of patients, for example. Similarly, some patterns of genes and biomarkers expression and the level of their expression can help in predicting cancer behavior such as metastasis and drug resistance. The current trend in cancer research, especially with the advancement in technology, is to sequence everything in hopes of finding disease-related mutations.

CONCLUSION

Optimizing pancreatic cancer treatment requires clear classification, understanding CAF roles, and exploring stroma reshaping approaches.

Eudesmane-type sesquiterpenoids from the aerial parts of Artemisia lavandulaefolia and their anti-pancreatic cancer activities

Five undescribed eudesmane sesquiterpenoids, artemilavanins A-E, and one undescribed rearranged eudesmane sesquiterpenoid, artemilavanin F, were isolated from the 95% ethanol extract of the aerial parts of Artemisia lavandulaefolia DC., along with ten known compounds. The structures and configurations of undescribed compounds were mainly elucidated by spectroscopic analyses and single-crystal X-ray diffraction analysis. Among all isolated compounds, artemilavanin F exhibited inhibitory activity on PANC-1 pancreatic cancer cells with IC50 of 9.69 ± 2.39 μM. Artemilavanin F inhibited PANC-1 cell proliferation by induction of G2/M cell cycle arrest and apoptosis mediated by downregulation of cyclin-dependent kinases and accumulation of reactive oxygen species. Moreover, artemilavanin F inhibited the colony formation, cell migration and sphere formation of PANC-1 cells, indicating the suppression of stem-cell-like phenotype of PANC-1 cells. Further results confirmed that the expression of cancer stem cell markers such as Bmi1, CD44, CD133 were inhibited by artemilavanin F. Downregulation of epithelial-mesenchymal transition (EMT) markers such as N-cadherin and Oct-4 indicated the potential of artemilavanin F in prevention of metastasis.

Differences and Similarities between Colorectal Cancer Cells and Colorectal Cancer Stem Cells: Molecular Insights and Implications

Malignant tumors are formed by diverse groups of cancer cells. Cancer stem cells (CSCs) are a subpopulation of heterogeneous cells identified in tumors that have the ability to self-renew and differentiate. Colorectal cancer (CRC), the third most frequent malignant tumor, is progressively being supported by evidence suggesting that CSCs are crucial in cancer development. We aim to identify molecular differences between CRC cells and CRC CSCs, as well as the effects of those differences on cell behavior in terms of migration, EMT, pluripotency, morphology, cell cycle/control, and epigenetic characteristics. The HT-29 cell line (human colorectal adenocarcinoma) and HT-29 CSCs (HT-29 CD133+/CD44+ cells) were cultured for 72 h. The levels of E-cadherin, KLF4, p53, p21, p16, cyclin D2, HDAC9, and P300 protein expression were determined using immunohistochemistry staining. The migration of cells was assessed by employing the scratch assay technique. Additionally, the scanning electron microscopy method was used to examine the morphological features of the cells, and their peripheral/central elemental ratios were compared with the help of EDS. Furthermore, a Muse cell cycle kit was utilized to determine the cell cycle analysis. The HT-29 CSC group exhibited high levels of expression for E-cadherin, p53, p21, p16, cyclin D2, HDAC9, and P300, whereas KLF4 was found to be high in the HT-29. The two groups did not exhibit any statistically significant differences in the percentages of cell cycle phases. The identification of specific CSC characteristics will allow for earlier cancer detection and the development of more effective precision oncology options.

The ufmylation modification of ribosomal protein L10 in the development of pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PAAD) is the most malignant cancer with a high mortality rate. Despite the association of ribosomal protein L10 (RPL10) with PAAD and previous reports on RPL26 ufmylation, the relationship between RPL10 ufmylation and PAAD development remains unexplored. Here, we report the dissection of ufmylating process of RPL10 and potential roles of RPL10 ufmylation in PAAD development. The ufmylation of RPL10 was confirmed in both pancreatic patient tissues and cell lines, and specific modification sites were identified and verified. Phenotypically, RPL10 ufmylation significantly increased cell proliferation and stemness, which is principally resulted from higher expression of transcription factor KLF4. Moreover, the mutagenesis of ufmylation sites in RPL10 further demonstrated the connection of RPL10 ufmylation with cell proliferation and stemness. Collectively, this study reveals that PRL10 ufmylation plays an important role to enhance the stemness of pancreatic cancer cells for PAAD development.

Emodin reverses resistance to gemcitabine in pancreatic cancer by suppressing stemness through regulation of the epithelial‑mesenchymal transition

The present study aimed to explore the effects and underlying mechanisms of emodin (Emo) on gemcitabine (GEM)-resistant pancreatic cancer. GEM-resistant SW1990 cells (SW1990/GZ) were established by successively doubling the concentration of GEM. Cell viability was measured using the CCK-8 assay and flow cytometry was used to measure cell apoptosis. Cell migration was assessed using a Transwell assay. Sphere and colony-formation assays were used to evaluate cell self-renewal. The expression levels of epithelial-mesenchymal transition (EMT) and stem cell biomarkers were determined using western blotting. Snail family transcriptional repressor 1 gene (Snail) was overexpressed by transfecting cells with pcDNA3.1-Snail plasmids. A xenograft model was established in nude mice by using SW1990/GZ and Snail-overexpressing SW1990/GZ cells. Proliferation, migration, self-renewal and EMT progression of GEM-treated SW1990/GZ cells were significantly suppressed in vitro by Emo treatment, whereas the overexpression of Snail abolished the aforementioned effects. In in vivo, the antitumor activity of GEM and the inhibitory effect of GEM against EMT progression and stem-like characteristics were enhanced by treatment with Emo, whilst overexpression of Snail reversed these effects. In conclusion, Emo reversed GEM resistance in pancreatic cancer by suppressing stemness and regulating EMT progression.

A Novel 3D Culture Scaffold to Shorten Development Time for Multicellular Tumor Spheroids

Multicellular tumor spheroids and tumoroids are considered ideal in vitro models that reflect the features of the tumor microenvironment. Biomimetic components resembling the extracellular matrix form scaffolds to provide structure to 3-dimensional (3D) culture systems, supporting the growth of both spheroids and tumoroids. Although Matrigel has long been used to support 3D culture systems, batch variations, component complexity, and the use of components derived from tumors are complicating factors. To address these issues, we developed the ACD 3D culture system to provide better control and consistency. We evaluated spheroid and tumoroid formation using the ACD 3D culture system, including the assessment of cell viability and cancer marker expression. Under ACD 3D culture conditions, spheroids derived from cancer cell lines exhibited cancer stem cell characteristics, including a sphere-forming size and the expression of stem cell marker genes. The ACD 3D culture system was also able to support patient-derived primary cells and organoid cell cultures, displaying adequate cell growth, appropriate morphology, and resistance to oxaliplatin treatment. These spheroids could also be used for drug screening purposes. In conclusion, the ACD 3D culture system represents an efficient tool for basic cancer research and therapeutic development.

microRNA-497 prevents pancreatic cancer stem cell gemcitabine resistance, migration, and invasion by directly targeting nuclear factor kappa B 1

Objectives: Cancer stem cells (CSCs) comprise a small population of cells in cancerous tumors and play a critical role in tumor resistance to chemotherapy. miRNAs have been reported to enhance the sensitivity of pancreatic cancer to chemotherapy. However, the underlying molecular mechanism requires better understanding.

Methods: Cell viability and proliferation were examined with CCK8 assays. Quantitative real-time polymerase chain reaction was executed to assess mRNA expression. StarBase database was used to select the target genes of miRNA, which were further affirmed by dual luciferase assay. Transwell assay was used to analyze cell invasion and migration.

Results: We proved that miR-497 could be obviously downregulated in pancreatic cancer tissues and CSCs from Aspc-1 and Bxpc-3 cells. In addition, inhibition of miR-497 evidently accelerated pancreatic CSC gemcitabine resistance, migration and invasion. Moreover, we revealed that nuclear factor kappa B 1 (NFκB1) was prominently upregulated in pancreatic cancer tissues and pancreatic CSCs, and NFκB1 was also identified as a direct target of miR-497. Furthermore, we demonstrated that overexpression of NFκB1 could also notably promote the viability, migration, and invasion of gemcitabine-treated pancreatic CSCs, but this effect could be partially abolished by miR-497 overexpression.

Conclusions: Those findings suggest that miR-497 overexpression could suppress gemcitabine resistance and the metastasis of pancreatic CSCs and non-CSCs by directly targeting NFκB1.

Epithelial and Mesenchymal Features of Pancreatic Ductal Adenocarcinoma Cell Lines in Two- and Three-Dimensional Cultures

Pancreatic ductal adenocarcinoma (PDAC) is an intractable cancer that is difficult to diagnose early, and there is no cure other than surgery. PDAC is classified as an adenocarcinoma that has limited effective anticancer drug and molecular-targeted therapies compared to adenocarcinoma found in other organs. A large number of cancer cell lines have been established from patients with PDAC that have different genetic abnormalities, including four driver genes; however, little is known about the differences in biological behaviors among these cell lines. Recent studies have shown that PDAC cell lines can be divided into epithelial and mesenchymal cell lines. In 3D cultures, morphological and functional differences between epithelial and mesenchymal PDAC cell lines were observed as well as the drug effects of different anticancer drugs. These effects included gemcitabine causing an increased growth inhibition of epithelial PDAC cells, while nab-paclitaxel caused greater mesenchymal PDAC cell inhibition. Thus, examining the characteristics of epithelial or mesenchymal PDAC cells with stromal cells using a 3D co-culture may lead to the development of new anticancer drugs.

TGF-β1 increases cellular invasion of colorectal neuroendocrine carcinoma cell line through partial epithelial-mesenchymal transition

Epithelial–mesenchymal transition (EMT) plays a pivotal role in cancer progression and metastasis in many types of malignancies, including colorectal cancer. Although the importance of EMT is also considered in colorectal neuroendocrine carcinoma (NEC), its regulatory mechanisms have not been elucidated. We recently established a human colorectal NEC cell line, SS-2. In this study, we aimed to clarify whether these cells were sensitive to transforming growth factor beta 1 (TGF-β1) and whether EMT could be induced through TGF-β1/Smad signaling, with the corresponding NEC cell-specific changes in invasiveness. In SS-2 cells, activation of TGF-β1 signaling, as indicated by phosphorylation of Smad2/3, was dose-dependent, demonstrating that SS-2 cells were responsive to TGF-β1. Analysis of EMT markers showed that mRNA levels changed with TGF-β1 treatment and that E-cadherin, an EMT marker, was expressed in cell-cell junctions even after TGF-β1 treatment. Invasion assays showed that TGF-β1-treated SS-2 cells invaded more rapidly than non-treated cells, and these cells demonstrated increased metalloproteinase activity and cell adhesion. Among integrins involved in cell-to-matrix adhesion, α2-integrin was exclusively upregulated in TGF-β1-treated SS-2 cells, but not in other colon cancer cell lines, and adhesion and invasion were inhibited by an anti-α2-integrin blocking antibody. Our findings suggest that α2-integrin may represent a novel therapeutic target for the metastasis of colorectal NEC cells.

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NEC cell line SS-2 is responsive to TGF-β1.

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TGF-β1 stimulation induces partial EMT, maintaining E-cadherin in SS-2 cells.

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TGF-β1-treated SS-2 cells exhibit increase in metalloproteinase activity and cell adhesion.

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α2-integrin is exclusively upregulated in TGF-β1-treated SS-2 cells.

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Use of anti-α2-integrin blocking antibody inhibits enhanced adhesion and invasion.

A new era: tumor microenvironment in chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a solid malignant tumor with an extremely poor prognosis. Gemcitabine (GEM)-based chemotherapy remains one of the most important treatment choices for PDAC. However, either as monotherapy or as a part of the combination chemotherapy, GEM achieved only limited success in improving the survival of patients with advanced PDAC, primarily due to GEM resistance. PDAC is characterized by an extensive desmoplasia in the tumor microenvironment (TME). Increasing evidence indicates that this fibrotic TME not only actively participates in the tumor growth and spread of PDAC but also contributes to the induction of GEM resistance. Here we review the current advances of how TME components are involved in the induction of GEM resistance.

Fzd7/Wnt7b signaling contributes to stemness and chemoresistance in pancreatic cancer

Mining databases and data obtained from assays on human specimens had shown that Fzd7 is closely associated with Wnt7b, that Fzd7/Wnt7b expression is upregulated in pancreatic cancer tissues compared with normal tissues, and its expression is negatively correlated with survival. Fzd7/Wnt7b knockdown in Capan‐2 and Panc‐1 cells reduced the proliferative capacity of pancreatic cancer stem cells (PCSCs), reduced drug resistance, decreased the percentage of CD24⁺CD44⁺ subset of cells and the levels of ABCG2, inhibited cell‐sphere formation, and reduced gemcitabine (GEM) resistance. In contrast, Fzd7/Wnt7b overexpression increased the percentage of the CD24⁺CD44⁺ subset of cells, and increased the levels of ABCG2 detected in cell spheroids. The gem‐resistant cells exhibited higher levels of Fzd7/Wnt7b expression, an increased percentage of CD24⁺CD44⁺ cells, and higher levels of ABCG2 compared with the parental cells. Taken together, Fzd7/Wnt7b knockdown can reduce PDAC cell stemness and chemoresistance by reducing the percentage of CSCs. Mechanistically, Fzd7 binds with Wnt7b and modulates the levels of β‐catenin, and they may exert their role via modulation of the canonical Wnt pathway.

Advances in research of extracellular mechanisms underlying gemcitabine resistance in pancreatic cancer

Pancreatic cancer is a solid malignant tumor with the worst prognosis worldwide, and about 90% of cases are pancreatic ductal adenocarcinoma (PDAC). Although surgical resection is the only potential way to cure PDAC, the overall survival rate after surgery is still not optimistic. Consequently, gemcitabine (GEM)-based chemotherapy is still one of the most important treatment options for PDAC. However, the survival improvement by GEM monotherapy for advanced PDAC is very limited, and GEM resistance is the key reason. The mechanism underlying gemcitabine resistance is complex and still unclear in PDAC. The extensive and dense fibrous mesenchyme in the tumor microenvironment (TME) is an important feature of PDAC. More and more evidence has shown that TME is not only an active participant in tumor growth and spread, but also a contributor to the induction of GEM resistance. This article will review the recent advances in the understanding of the cellular and molecular mechanisms underlying GEM resistance in PDAC, and discuss potential GEM chemosensitization strategies, in order to improve the effective rate of chemotherapy and the outcome.

Pancreatic Cancer Stem-Like Cells With High Calreticulin Expression Associated With Immune Surveillance

OBJECTIVE

Pancreatic cancer stem-like cells (P-CSLCs) are thought to be associated with poor prognosis. Previously, we used proteomic analysis to identify a chaperone pro-phagocytic protein calreticulin (CALR) as a P-CSLC-specific protein. This study aimed to investigate the association between CALR and P-CSLC.

METHODS

PANC-1-Lm cells were obtained as P-CSLCs from a human pancreatic cancer cell line, PANC-1, using a sphere induction medium followed by long-term cultivation on laminin. To examine the cancer stem cell properties, subcutaneous injection of the cells into immune-deficient mice and sphere formation assay were performed. Cell surface expression analysis was performed using flow cytometry.

RESULTS

PANC-1-Lm showed an increased proportion of cell surface CALR-positive and side-population fractions compared with parental cells. PANC-1-Lm cells also had higher frequency of xenograft tumor growth and sphere formation than PANC-1 cells. Moreover, sorted CALRhigh cells from PANC-1-Lm had the highest sphere formation frequency among tested cells. Interestingly, the number of programmed death-ligand 1-positive cells among CALRhigh cells was increased as well, whereas that of human leukocyte antigen class I-positive cells decreased.

CONCLUSION

In addition to the cancer stem cell properties, the P-CSLC, which showed elevated CALR expression on the cell surface, might be associated with evasion of immune surveillance.

Hypoxia, partial EMT and collective migration: Emerging culprits in metastasis

Epithelial-mesenchymal transition (EMT) is a cellular biological process involved in migration of primary cancer cells to secondary sites facilitating metastasis. Besides, EMT also confers properties such as stemness, drug resistance and immune evasion which can aid a successful colonization at the distant site. EMT is not a binary process; recent evidence suggests that cells in partial EMT or hybrid E/M phenotype(s) can have enhanced stemness and drug resistance as compared to those undergoing a complete EMT. Moreover, partial EMT enables collective migration of cells as clusters of circulating tumor cells or emboli, further endorsing that cells in hybrid E/M phenotypes may be the 'fittest' for metastasis. Here, we review mechanisms and implications of hybrid E/M phenotypes, including their reported association with hypoxia. Hypoxia-driven activation of HIF-1α can drive EMT. In addition, cyclic hypoxia, as compared to acute or chronic hypoxia, shows the highest levels of active HIF-1α and can augment cancer aggressiveness to a greater extent, including enriching for a partial EMT phenotype. We also discuss how metastasis is influenced by hypoxia, partial EMT and collective cell migration, and call for a better understanding of interconnections among these mechanisms. We discuss the known regulators of hypoxia, hybrid EMT and collective cell migration and highlight the gaps which needs to be filled for connecting these three axes which will increase our understanding of dynamics of metastasis and help control it more effectively.

Peritoneal Metastatic Cancer Stem Cells of Gastric Cancer with Partial Mesenchymal-Epithelial Transition and Enhanced Invasiveness in an Intraperitoneal Transplantation Model

OBJECTIVES

This preliminary study is aimed at enriching and isolating peritoneal metastatic cancer stem cells (pMCSCs) of gastric cancer and assessing their epithelial-mesenchymal transition (EMT) phenotype and invasiveness.

METHODS

Cancer stem cells of human gastric cancer (CSC-hGC) were previously isolated and transfected with green fluorescent protein and luciferase genes to validate the mouse model of peritoneal metastasis established via transplantation. The first and second generations ([G1] and [G2], respectively) of pMCSCs were isolated from intraperitoneally transplanted CSC-hGC (pMCSC-tGC) by spherical culture. CSC and EMT-related markers and regulators in the two generations of intraperitoneally transplanted tumors were examined by immunohistochemistry, immunofluorescence staining, and quantitative PCR. Cell mobility was examined by a transwell assay.

RESULTS

The nude mouse model of intraperitoneally transplanted CSC-hGC was successful in establishing sequential formation of peritoneal tumors and enrichment of pMCSCs. CD44 and CD54 were consistently expressed in the two generations of transplanted tumors. In vitro cell (migration) assays and immunocytofluorescence assays showed that in pMCSC-tGC[G2], E-cad, Survivin, and Vimentin expression was stable; α-SMA expression was decreased; and OVOL2, GRHL2, and ZEB1 expression was increased. PCR analysis indicated that in pMCSC-tGC[G2], the mRNA expression of E-cad, α-SMA, MMP9, MMP2, and Vimentin was downregulated, while that of ZEB1, OVOL2, and GRHL2 was upregulated. In vivo tumor (homing) assays and immunohistochemical assays demonstrated that in pMCSC-tGC[G2], E-cad and Snail were upregulated, while α-SMA was downregulated. The numbers of migrated and invaded pMCSC-tGC[G1] and pMCSC-tGC[G2] were significantly higher than those of CSC-hGC in migration and invasion assays.

CONCLUSIONS

pMCSCs might be a specific subpopulation that can be sequentially enriched by intraperitoneal transplantation. pMCSCs exhibited a tendency towards partial mesenchymal-epithelial transition, enhancing their invasiveness during homing and the formation of peritoneal tumors. However, these preliminary findings require validation in further experiments.

Vitamin E δ-tocotrienol sensitizes human pancreatic cancer cells to TRAIL-induced apoptosis through proteasome-mediated down-regulation of c-FLIPs

BACKGROUND

Vitamin E δ-tocotrienol (VEDT), a vitamin E compound isolated from sources such as palm fruit and annatto beans, has been reported to have cancer chemopreventive and therapeutic effects.

METHODS

We report a novel function of VEDT in augmenting tumor necrosis factor-related apoptosis-inducing ligand- (TRAIL-) induced apoptosis in pancreatic cancer cells. The effects of VEDT were shown by its ability to trigger caspase-8-dependent apoptosis in pancreatic cancer cells.

RESULTS

When combined with TRAIL, VEDT significantly augmented TRAIL-induced apoptosis of pancreatic cancer cells. VEDT decreased cellular FLICE inhibitory protein (c-FLIP) levels without consistently modulating the expression of decoy death receptors 1, 2, 3 or death receptors 4 and 5. Enforced expression of c-FLIP substantially attenuated VEDT/TRAIL-induced apoptosis. Thus, c-FLIP reduction plays an important part in mediating VEDT/TRAIL-induced apoptosis. Moreover, VEDT increased c-FLIP ubiquitination and degradation but did not affect its transcription, suggesting that VEDT decreases c-FLIP levels through promoting its degradation. Of note, degradation of c-FLIP and enhanced TRAIL-induced apoptosis in pancreatic cancer cells were observed only with the anticancer bioactive vitamin E compounds δ-, γ-, and β-tocotrienol but not with the anticancer inactive vitamin E compounds α-tocotrienol and α-, β-, γ-, and δ-tocopherol.

CONCLUSIONS

c-FLIP degradation is a key event for death receptor-induced apoptosis by anticancer bioactive vitamin E compounds in pancreatic cancer cells. Moreover, VEDT augmented TRAIL inhibition of pancreatic tumor growth and induction of apoptosis in vivo. Combination therapy with TRAIL agonists and bioactive vitamin E compounds may offer a novel strategy for pancreatic cancer intervention.

The ionophore antibiotic gramicidin A inhibits pancreatic cancer stem cells associated with CD47 down-regulation

Background

Pancreatic cancer stem cells (CSCs), a special population of cells, renew themselves infinitely and resist to various treatment. Gramicidin A (GrA), an ionophore antibiotic derived from microorganism, can form channels across the cell membrane and disrupt cellular ionic homeostasis, leading to cell dysfunction and death. As reported, the ionophore antibiotic salinomycin (Sal) has been proved to kill CSCs effectively. Whether GrA owns the potential as a therapeutic drug for CSCs still remains unknown. This study investigated the effect of GrA on pancreatic CSCs and the mechanism.

Methods

Tumorsphere formation assay was performed to assess pancreatic CSCs self-renewal potential. In vitro hemolysis assay was determined to test the borderline concentration of GrA. CCK-8 assay was used to detect pancreatic cancer cell proliferation capability. Flow cytometry was performed to detect cell apoptosis and mitochondrial membrane potential. Scanning and transmission electron microscopy was used to observe ultrastructural morphological changes on cell membrane surface and mitochondria, respectively. Western blot analysis was used to determine relative protein expression levels. Immunofluorescence staining was performed to observe CD47 re-distribution.

Results

GrA at 0.05 μM caused tumorspheres disintegration and decrease in number of pancreatic cancer BxPC-3 and MIA PaCa-2 cells. GrA and Sal both inhibited cancer cell proliferation. The IC50 values of GrA and Sal for BxPC-3 cells were 0.025 μM and 0.363 μM; while for MIA PaCa-2 cells were 0.032 μM and 0.163 μM, respectively. Compared on equal concentrations, the efficacy of GrA was stronger than that of Sal. GrA at 0.1 μM or lower did not cause hemolysis. GrA induced ultrastructural changes, such as the decrease of microvilli-like protrusions on cell surface membrane and the swelling of mitochondria. GrA down-regulated the expression levels of CD133, CD44, and CD47; in addition, CD47 re-distribution was observed on cell surface. Moreover, GrA showed synergism with gemcitabine in suppressing cancer cell proliferation.

Conclusions

The study found that GrA was highly active against pancreatic CSCs. It indicates that GrA exerts inhibitory effects against pancreatic CSCs associated with CD47 down-regulation, implying that GrA might play a positive role in modulating the interaction between macrophages and tumor cells.

Dichloroacetate Affects Mitochondrial Function and Stemness-Associated Properties in Pancreatic Cancer Cell Lines

Targeting metabolism represents a possible successful approach to treat cancer. Dichloroacetate (DCA) is a drug known to divert metabolism from anaerobic glycolysis to mitochondrial oxidative phosphorylation by stimulation of PDH. In this study, we investigated the response of two pancreatic cancer cell lines to DCA, in two-dimensional and three-dimension cell cultures, as well as in a mouse model. PANC-1 and BXPC-3 treated with DCA showed a marked decrease in cell proliferation and migration which did not correlate with enhanced apoptosis indicating a cytostatic rather than a cytotoxic effect. Despite PDH activation, DCA treatment resulted in reduced mitochondrial oxygen consumption without affecting glycolysis. Moreover, DCA caused enhancement of ROS production, mtDNA, and of the mitophagy-marker LC3B-II in both cell lines but reduced mitochondrial fusion markers only in BXPC-3. Notably, DCA downregulated the expression of the cancer stem cells markers CD24/CD44/EPCAM only in PANC-1 but inhibited spheroid formation/viability in both cell lines. In a xenograft pancreatic cancer mouse-model DCA treatment resulted in retarding cancer progression. Collectively, our results clearly indicate that the efficacy of DCA in inhibiting cancer growth mechanistically depends on the cell phenotype and on multiple off-target pathways. In this context, the novelty that DCA might affect the cancer stem cell compartment is therapeutically relevant.

Yarrow supercritical extract exerts antitumoral properties by targeting lipid metabolism in pancreatic cancer

Metabolic reprogramming is considered a hallmark of cancer. Currently, the altered lipid metabolism in cancer is a topic of interest due to the prominent role of lipids regulating the progression of various types of tumors. Lipids and lipid-derived molecules have been shown to activate growth regulatory pathways and to promote malignancy in pancreatic cancer. In a previous work, we have described the antitumoral properties of Yarrow (Achillea Millefolium) CO₂ supercritical extract (Yarrow SFE) in pancreatic cancer. Herein, we aim to investigate the underlaying molecular mechanisms by which Yarrow SFE induces cytotoxicity in pancreatic cancer cells. Yarrow SFE downregulates SREBF1 and downstream molecular targets of this transcription factor, such as fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD). Importantly, we demonstrate the in vivo effect of Yarrow SFE diminishing the tumor growth in a xenograft mouse model of pancreatic cancer. Our data suggest that Yarrow SFE can be proposed as a complementary adjuvant or nutritional supplement in pancreatic cancer therapy.

Prevention of breast cancer by dietary polyphenols-role of cancer stem cells

Breast cancer is a common malignancy with poor prognosis. Cancer cells are heterogeneous and cancer stem cells (CSCs) are primarily responsible for tumor relapse, treatment-resistance and metastasis, so for breast cancer stem cells (BCSCs). Diets are known to be associated with carcinogenesis. Food-derived polyphenols are able to attenuate the formation and virulence of BCSCs, implying that these compounds and their analogs might be promising agents for preventing breast cancer. In the present review, we summarized the origin and surface markers of BCSCs and possible mechanisms responsible for the inhibitory effects of polyphenols on BCSCs. The suppressive effects of common dietary polyphenols against BCSCs, such as curcumin, epigallocatechin gallate (EGCG) and related polyphenolic compounds were further discussed.

Hypoxia potentiates gemcitabine-induced stemness in pancreatic cancer cells through AKT/Notch1 signaling

BACKGROUND

Profound chemoresistance remains an intractable obstacle in pancreatic cancer treatment. Pancreatic cancer stem cells (CSCs) and the ubiquitous hypoxic niche have been proposed to account for drug resistance. However, the mechanism involved requires further exploration. This study investigated whether the hypoxic niche enhances gemcitabine-induced stemness and acquired resistance in pancreatic cancer cells by activating the AKT/Notch1 signaling cascade. The therapeutic effects of blockading this signaling cascade on gemcitabine-enriched CSCs were also investigated.

METHODS

The expression levels of CSC-associated markers Bmi1 and Sox2 as well as those of proteins involved in AKT/Notch1 signaling were measured by Western blot analysis. The expression level of the pancreatic CSC marker CD24 was measured by flow cytometry. Change in gemcitabine sensitivity was evaluated by the MTT assay. The ability of sphere formation was tested by the sphere-forming assay in stem cell medium. The ability of migration and invasion was detected by the transwell migration/invasion assay. A mouse xenograft model of pancreatic cancer was established to determine the effect of Notch1 inhibition on the killing effect of gemcitabine in vivo. The ability of metastasis was investigated by an in vivo lung metastasis assay.

RESULTS

Gemcitabine promoted pancreatic cancer cell stemness and associated malignant phenotypes such as enhanced migration, invasion, metastasis, and chemoresistance. The AKT/Notch1 signaling cascade was activated after gemcitabine treatment and mediated this process. Blockading this pathway enhanced the killing effect of gemcitabine in vivo. However, supplementation with hypoxia treatment synergistically enhanced the AKT/Notch1 signaling pathway and collaboratively promoted gemcitabine-induced stemness.

CONCLUSIONS

These findings demonstrate a novel mechanism of acquired gemcitabine resistance in pancreatic cancer cells through induction of stemness, which was mediated by the activation of AKT/Notch1 signaling and synergistically aggravated by the ubiquitous hypoxic niche. Our results might provide new insights for identifying potential targets for reversing chemoresistance in patients with pancreatic cancer.

Hyaluronic Acid-Based Multilayer Films Regulate Hypoxic Multicellular Aggregation of Pancreatic Cancer Cells with Distinct Cancer Stem-Cell-like Properties

In vitro spherical cancer models have been widely used in cancer stem cell (CSC) research, and the ability of CSCs to form multicellular colonies is recognized as a morphological marker. However, although several spherical/colony models share a common three-dimensional (3D) conformation, each model displays its own intrinsic properties. Thus, the CSC phenotypes with distinct multicellular aggregate morphologies must be defined and clarified. Here, a novel 3D model was designed to regulate the type of pancreatic CSC colonies that form using niche mimetic hyaluronic acid (HA)-based multilayer nanofilms and hypoxia. The multicellular aggregate morphology, CSC phenotypes, CSC-related marker expression, cell cycle, invasion, and drug resistance were determined. On the basis of the results of a cell morphology analysis, colonies formed on multilayer nanofilms in response to both normoxia and hypoxia, but round and island-type colonies, were investigated. Immunostaining results revealed a significantly higher expression of stem cell markers, such as OCT4, CXCR4, and CD44v6, in colonies that formed on multilayer nanofilms. These colonies also expressed higher levels of E-cadherin, hypoxia-inducible factor-1α, and vimentin, particularly the round-type colonies that formed on HA-based multilayer nanofilms, [poly(allylamine) (PAH)/HA]₃, indicating that these colonies exhibit hybrid and metastable epithelial/mesenchymal phenotypes. Moreover, the cell cycle and invasion tests revealed that most of the cells in colonies growing on multilayer nanofilms showed a quiescent, slow cycling phenotype but displayed higher invasion after induction. Furthermore, a hypoxic environment strongly influences the drug resistance. This study describes a useful tool to investigate the diverse phenotypes of pancreatic CSC colonies and to study their regulatory factors that may benefit CSC research.

Pancreatic cancer stem cells: features and detection methods

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a high incidence of distant metastasis and recurrence. Cancer stem cells (CSCs), which are pluripotent, self-renewable, and capable of forming tumors, contribute to PDAC initiation and metastasis and are responsible for resistance to chemotherapy and radiation. Three types of experimental methods are commonly used to identify CSCs: CSC-specific marker detection, a sphere-formation assay that reveals cell proliferation under non-adherent conditions, and detection of side-population (SP) cells that possess high intracellular-to-extracellular pump functions. Several CSC-specific markers have been reported in PDACs, including CD133, CD24, CD44, CXCR4, EpCAM, ABCG2, c-Met, ALDH-1, and nestin. There remains controversy regarding which markers are specific to PDAC CSCs and which are expressed alone or in combination in CSCs. Examining characteristics of isolated CSCs and discovering CSC-specific treatment options are important to improve the prognosis of PDAC cases. This review summarizes CSC-detection methods for PDAC, including CSC-marker detection, the sphere-formation assay, and detection of SP cells.

Hybrid epithelial/mesenchymal phenotypes promote metastasis and therapy resistance across carcinomas

Cancer metastasis and therapy resistance are the major unsolved clinical challenges, and account for nearly all cancer-related deaths. Both metastasis and therapy resistance are fueled by epithelial plasticity, the reversible phenotypic transitions between epithelial and mesenchymal phenotypes, including epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET). EMT and MET have been largely considered as binary processes, where cells detach from the primary tumor as individual units with many, if not all, traits of a mesenchymal cell (EMT) and then convert back to being epithelial (MET). However, recent studies have demonstrated that cells can metastasize in ways alternative to traditional EMT paradigm; for example, they can detach as clusters, and/or occupy one or more stable hybrid epithelial/mesenchymal (E/M) phenotypes that can be the end point of a transition. Such hybrid E/M cells can integrate various epithelial and mesenchymal traits and markers, facilitating collective cell migration. Furthermore, these hybrid E/M cells may possess higher tumor-initiation and metastatic potential as compared to cells on either end of the EMT spectrum. Here, we review in silico, in vitro, in vivo and clinical evidence for the existence of one or more hybrid E/M phenotype(s) in multiple carcinomas, and discuss their implications in tumor-initiation, tumor relapse, therapy resistance, and metastasis. Together, these studies drive the emerging notion that cells in a hybrid E/M phenotype may occupy 'metastatic sweet spot' in multiple subtypes of carcinomas, and pathways linked to this (these) hybrid E/M state(s) may be relevant as prognostic biomarkers as well as a promising therapeutic targets.

Salvianolic acid B reverses multidrug resistance in nude mice bearing human colon cancer stem cells

Salvianolic acid B (SalB) is a water-soluble phenolic compound, extractable from Salvia miltiorrhiza, and has previously been demonstrated to reverse tumor multidrug resistance (MDR) in colon cancer cells. Cancer stem cells (CSCs) are closely associated with drug resistance. Therefore, establishing a nude mouse model bearing human colon CSCs is important for the study of the mechanisms underlying colon cancer drug resistance as well as the reversal of drug resistance. The present study aimed to establish a nude mouse model bearing human colon CSCs and to investigate the effects of SalB on the drug resistance exhibited by the nude mouse model as well as determine its underlying mechanism. Cells from two colon cancer cell lines (LoVo and HCT-116) were cultured in serum-free medium to obtain CSCs-enriched spheroid cells. Following this, nude mice were transplanted with LoVo and HCT-116 colon CSCs to establish the CSC nude mouse model, which was subsequently demonstrated to exhibit MDR. The results of the present study revealed that following treatment with SalB, the chemotherapeutic drug resistance of xenografts was reversed to a certain extent. Western blot analysis was performed to investigate the expression levels of cluster of differentiation (CD)44, CD133, transcription factor sox-2 (SOX2) and ATP-binding cassette sub-family G member 2 (ABCG2) proteins, and the results demonstrated that treatment with SalB downregulated the expression of CD44, SOX2 and ABCG2 proteins in both LoVo and HCT-116 colon CSCs xenografts. In conclusion, the results of the present study revealed that a serum-free suspension method can be performed to successfully isolate colon CSCs. In addition, a nude mice bearing colon CSCs animal model was successfully established, and associated tumors were confirmed to exhibit MDR. Furthermore, SalB was demonstrated to successfully reverse MDR in nude mice bearing LoVo and HCT-116 colon CSCs, as well as suppress the expression of CD44, SOX2 and ABCG2 proteins.

Metarrestin, a perinucleolar compartment inhibitor, effectively suppresses metastasis

Metastasis remains a leading cause of cancer mortality due to the lack of specific inhibitors against this complex process. To identify compounds selectively targeting the metastatic state, we used the perinucleolar compartment (PNC), a complex nuclear structure associated with metastatic behaviors of cancer cells, as a phenotypic marker for a high-content screen of over 140,000 structurally diverse compounds. Metarrestin, obtained through optimization of a screening hit, disassembles PNCs in multiple cancer cell lines, inhibits invasion in vitro, suppresses metastatic development in three mouse models of human cancer, and extends survival of mice in a metastatic pancreatic cancer xenograft model with no organ toxicity or discernable adverse effects. Metarrestin disrupts the nucleolar structure and inhibits RNA polymerase (Pol) I transcription, at least in part by interacting with the translation elongation factor eEF1A2. Thus, metarrestin represents a potential therapeutic approach for the treatment of metastatic cancer.

The role of cancer-associated fibroblast MRC-5 in pancreatic cancer

Background: Our previous study showed that cancer-associated fibroblast MRC-5 promoted hepatocellular carcinoma progression by enhancing migration and invasion capability. However, few studies have explored the role of MRC-5 in pancreatic cancer (PC). In this study, we examined the exact role and associated mechanisms of MRC-5. Methods: The conditioned media for MRC-5 was used to culture PC cell lines SW1990 and PANC-1. Cell proliferation was compared based on colony formation assays of PC cells in normal media and of PC cells cultured with conditioned media of MRC-5. Cell migration and invasion were assayed by transwell chambers. The expression of EMT-related proteins and apoptosis-related proteins was evaluated using Western blot. And confocal microscopy was used to further detect the expression of EMT-related proteins. qRT-PCR was used to confirm the expression changes of related genes at the mRNA level. We also used flow cytometry to examine the cell cycle, apoptotic rate, and expression of CD3, CD4, CD14, CD25, CD45, CD61, CD90, TLR1, and TLR4. Results: MRC-5 repressed the colony formation ability of PC cells and significantly inhibited cell migration and invasion potential. MRC-5 induced S-phase cell cycle arrest but did not augment the apoptotic effects in PC cells. We hypothesized that the weakened malignant biological behavior of PC cells was correlated with MRC-5-induced altered expression of the cancer stem cell marker CD90; the immune-related cell surface molecules CD14, CD25, TLR4, and TLR1; and cell polarity complexes Par, Scribble, and Crumbs. Conclusion: MRC-5 limits the malignant activities of PC cells by suppressing cancer stem cell expansion, remolding epithelial polarity, and blocking the protumoral cascade reaction coupled to TLR4, TLR1, CD14, and CD25.

SUV420H2 is an epigenetic regulator of epithelial/mesenchymal states in pancreatic cancer

Epithelial-to-mesenchymal transition is implicated in metastasis. Viotti et al. show that the histone methyltransferase SUV420H2 favors the mesenchymal identity in pancreatic tumor cells by silencing key drivers of the epithelial state. High levels of SUV420H2 also correlate with a loss of epithelial characteristics in invasive cancer.

Epithelial-to-mesenchymal transition is implicated in metastasis, where carcinoma cells lose sessile epithelial traits and acquire mesenchymal migratory potential. The mesenchymal state is also associated with cancer stem cells and resistance to chemotherapy. It might therefore be therapeutically beneficial to promote epithelial identity in cancer. Because large-scale cell identity shifts are often orchestrated on an epigenetic level, we screened for candidate epigenetic factors and identified the histone methyltransferase SUV420H2 (KMT5C) as favoring the mesenchymal identity in pancreatic cancer cell lines. Through its repressive mark H4K20me3, SUV420H2 silences several key drivers of the epithelial state. Its knockdown elicited mesenchymal-to-epithelial transition on a molecular and functional level, and cells displayed decreased stemness and increased drug sensitivity. An analysis of human pancreatic cancer biopsies was concordant with these findings, because high levels of SUV420H2 correlated with a loss of epithelial characteristics in progressively invasive cancer. Together, these data indicate that SUV420H2 is an upstream epigenetic regulator of epithelial/mesenchymal state control.

MiR-628-5p decreases the tumorigenicity of epithelial ovarian cancer cells by targeting at FGFR2

Micro RNAs (miRNAs) are small non-coding RNAs which are 19-24 nucleotides in length. MiRNAs play a vital role in the whole process of tumour development, but how they influence the tumourigenecity of epithelial ovarian cancer (EOC)cells is rarely researched. In our study, it was verified that miR-628-5p decreased the stem like cell percentage of EOC cells by inducing their apoptosis. The animal experiments showed that miR-628-5p decreased the tumourigenecity of EOC cells. Besides, we found miR-628-5p targeted at and down-regulated the expression of fibroblast growth factor receptor 2 (FGFR2). FGFR2 expressed higher in ovarian cancer tissues and was correlated with worse prognosis. Our findings indicated that miR-628-5pplays an important role in ovarian cancer stem cell driven tumorigenesis.

Electron microscopic analysis of different cell types in human pancreatic cancer spheres

Cancer stem cells (CSCs), which are pluripotent and self-renewable, contribute to the initiation and metastasis of cancer, and are responsible for resistance to chemotherapy and radiation. Pancreatic ductal adenocarcinoma (PDAC) is an aggressive type of cancer that is associated with a high incidence of distant metastasis and recurrence. Sphere formation reveals cell proliferation under nonadherent conditions and is commonly used to identify CSCs; measurements of the number, area and volume of the spheres are used to estimate stemness of PDAC cells. However, detailed morphological analysis of such spheres has not been performed. The aim of the present study was to examine the morphology of spheres isolated from PANC-1 human pancreatic cancer cells via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). PANC-1 cells formed round to irregular oblong spheres within 1 week following seeding in ultra-low-attachment plates. These spheres exhibited higher levels of expression of CSC markers, including nestin, sex determining region Y-box 2, and CD44 containing variant exon 9, compared with adherent cells. SEM analysis revealed that the spheres exhibited a grape-like appearance, harboring cancer cells with smooth or rough surfaces. Similarly, TEM analysis detected cancer cells with varying surface types within the spheres: Those with smooth surfaces, irregular large protrusions, protrusions and a small number of microvilli, and those with many microvilli throughout the entire cell surface. These morphological differences among cancer cells may be indicative of different stages in the differentiation process, from CSCs to non-CSCs, within the spheres.

Gemcitabine treatment causes resistance and malignancy of pancreatic cancer stem-like cells via induction of lncRNA HOTAIR

Gemcitabine is the first-line chemotherapeutic agent for advanced adenocarcinoma of the pancreas, despite the high risk of chemoresistance as a major disadvantage. In the past few years, significant advances have been made in the field of pancreatic cancer stem-like cells (CSCs) and their critical roles in drug resistance, invasion and metastasis, which are tightly regulated by long non-coding RNAs (lncRNAs). The present study demonstrated that HOX antisense intergenic RNA (HOTAIR) is not different between the pancreatic cancer cell line PANC-1 and its enriched CSC sub-population. However, after gemcitabine treatment, the expression levels of HOTAIR in CSCs were induced, but not in PANC-1 cells. HOTAIR induced by gemcitabine failed to cause chemoresistance, but promoted the clonogenicity, proliferation and migration of the cells. By introducing HOTAIR using lentivirus, chemoresistance was induced and the self-renewal capacity, proliferation and migration were significantly promoted. By contrast, HOTAIR knockdown in PANC-1 CSCs treated with or without gemcitabine decreased the cell proliferation, altered the cell cycle progression and induced apoptosis, demonstrating its critical roles in regulating the malignant character of PANC-1 CSCs. In conclusion, the present study demonstrated that HOTAIR may be induced by gemcitabine and acts as a tumor promoter by inhibiting the chemosensitivity, and promoting the self-renewal capacity, proliferation and migration of PANC-1 CSCs, which supports its potential application as a novel therapeutic approach for pancreatic cancer.

Histone deacetylases, microRNA and leptin crosstalk in pancreatic cancer

Because pancreatic cancer (PC) historically has had poor prognosis and five year survival rates, it has been intensely investigated. Analysis of PC incidence and biology has shown a link between different risk factors such as smoking, alcoholism, and obesity and disease progression. Important factors affecting PC include the epigenomic changes driven by DNA methylation and histone acetylation, and actions of microRNA inducing oncogenic or tumor suppressor effects. Studies have identified markers whose dysregulation seem to play important roles in PC progression. PC markers involve classical histone deacetylases (HDAC), PC stem cell (PCSC), and leptin. In this review, we discuss the role of several PC biomarkers, and the potential crosstalk between HDAC, microRNA, and leptin in PC progression. Dysregulated expression of these molecules can increase proliferation, survival, PCSC, resistance to chemotherapy and tumor angiogenesis. The potential relationships between these molecules are further analyzed using data from The Cancer Genome Atlas and crosstalk pathways generated by the Pathway Studio Platform (Ariadne Genomics, Inc.). Oncogenic miRNA21 and tumor suppressor miRNA200 have been previously linked to leptin signaling. Preliminary analysis of PC biopsies and signaling crosstalk suggests that the main adipokine leptin could affect the expression of microRNA and HDAC in PC. Data analysis suggests that HDAC-microRNA-leptin signaling crosstalk may be a new target for PC therapy.

Bmi-1 overexpression as an efficient prognostic marker in patients with nonsmall cell lung cancer

BACKGROUND

The prognostic effect of B-cell-specific Moloney leukemia virus insertion site 1 (Bmi-1) in patients with nonsmall cell lung cancer (NSCLC) remains controversial. We thus performed a meta-analysis to reveal the correlation between Bmi-1 with clinical features and overall survival (OS) in NSCLC.

METHODS

Relevant studies were searched through PubMed, Embase, and Web of Science. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) as well as odds ratios (ORs) and 95% CIs were calculated by using STATA version 12.0.

RESULTS

Fourteen studies consisting of 1323 patients were included for quantitative analysis. The results showed that Bmi-1 was significantly associated with tumor size (n = 7, OR = 1.79, 95% CI = 1.19-2.71, P = .005, fixed effect), poor differentiation (OR = 1.61, 95% CI = 1.11-2.33, P = .011, fixed effect), and distant metastasis (n = 4, OR = 4.69, 95% CI = 1.52-14.41, P = .007, fixed effect). In addition, high Bmi-1 expression also predicted poor OS (HR = 1.62, 95% CI = 1.14-2.3, P < .001). There was no significant publication bias for any of the analyses.

CONCLUSION

In conclusion, Bmi-1 overexpression was correlated with tumor size, poor differentiation, distant metastasis, and worse OS in NSCLC. Therefore, Bmi-1 could be recommended as an efficient prognostic marker for NSCLC.

The epithelial to mesenchymal transition (EMT) and cancer stem cells: implication for treatment resistance in pancreatic cancer

The mechanical properties of epithelial to mesenchymal transition (EMT) and a pancreatic cancer subpopulation with stem cell properties have been increasingly recognized as potent modulators of the effective of therapy. In particular, pancreatic cancer stem cells (PCSCs) are functionally important during tumor relapse and therapy resistance. In this review we have surveyed recent advances in the role of EMT and PCSCs in tumor progression, metastasis and treatment resistance, and the mechanisms of integrated with biochemical signals and the underlying pathways involved in treatment resistance of pancreatic cancer. These findings highlight the importance of confirming stem-cells markers and complex molecular signaling pathways controlling EMT and cancer stem cells in pancreatic cancer during tumor formation, progression, and response to therapy.

Yin Yang 1 is associated with cancer stem cell transcription factors (SOX2, OCT4, BMI1) and clinical implication

The transcription factor Yin Yang 1 (YY1) is frequently overexpressed in cancerous tissues compared to normal tissues and has regulatory roles in cell proliferation, cell viability, epithelial-mesenchymal transition, metastasis and drug/immune resistance. YY1 shares many properties with cancer stem cells (CSCs) that drive tumorigenesis, metastasis and drug resistance and are regulated by overexpression of certain transcription factors, including SOX2, OCT4 (POU5F1), BMI1 and NANOG. Based on these similarities, it was expected that YY1 expression would be associated with SOX2, OCT4, BMI1, and NANOG’s expressions and activities. Data mining from the proteomic tissue-based datasets from the Human Protein Atlas were used for protein expression patterns of YY1 and the four CSC markers in 17 types of cancer, including both solid and hematological malignancies. A close association was revealed between the frequency of expressions of YY1 and SOX2 as well as SOX2 and OCT4 in all cancers analyzed. Two types of dynamics were identified based on the nature of their association, namely, inverse or direct, between YY1 and SOX2. These two dynamics define distinctive patterns of BMI1 and OCT4 expressions. The relationship between YY1 and SOX2 expressions as well as the expressions of BMI1 and OCT4 resulted in the classification of four groups of cancers with distinct molecular signatures: 1) Prostate, lung, cervical, endometrial, ovarian and glioma cancers (YY1^loSOX2^hiBMI1^hiOCT4^hi) 2) Skin, testis and breast cancers (YY1^hiSOX2^loBMI1^hiOCT4^hi) 3) Liver, stomach, renal, pancreatic and urothelial cancers (YY1^loSOX2^loBMI1^hiOCT4^hi) and 4) Colorectal cancer, lymphoma and melanoma (YY1^hiSOX2^hiBMI1^loOCT4^hi). A regulatory loop is proposed consisting of the cross-talk between the NF-kB/PI3K/AKT pathways and the downstream inter-regulation of target gene products YY1, OCT4, SOX2 and BMI1.

Multifunctionalized iron oxide nanoparticles for selective drug delivery to CD44-positive cancer cells

Nanomedicine nowadays offers novel solutions in cancer therapy and diagnosis by introducing multimodal treatments and imaging tools in one single formulation. Nanoparticles acting as nanocarriers change the solubility, biodistribution and efficiency of therapeutic molecules, reducing their side effects. In order to successfully  apply these novel therapeutic approaches, efforts are focused on the biological functionalization of the nanoparticles to improve the selectivity towards cancer cells. In this work, we present the synthesis and characterization of novel multifunctionalized iron oxide magnetic nanoparticles (MNPs) with antiCD44 antibody and gemcitabine derivatives, and their application for the selective treatment of CD44-positive cancer cells. The lymphocyte homing receptor CD44 is overexpressed in a large variety of cancer cells, but also in cancer stem cells (CSCs) and circulating tumor cells (CTCs). Therefore, targeting CD44-overexpressing cells is a challenging and promising anticancer strategy. Firstly, we demonstrate the targeting of antiCD44 functionalized MNPs to different CD44-positive cancer cell lines using a CD44-negative non-tumorigenic cell line as a control, and verify the specificity by ultrastructural characterization and downregulation of CD44 expression. Finally, we show the selective drug delivery potential of the MNPs by the killing of CD44-positive cancer cells using a CD44-negative non-tumorigenic cell line as a control. In conclusion, the proposed multifunctionalized MNPs represent an excellent biocompatible nanoplatform for selective CD44-positive cancer therapy in vitro.

The Metastatic Potential and Chemoresistance of Human Pancreatic Cancer Stem Cells

Cancer stem cells (CSCs) typically have the capacity to evade chemotherapy and may be the principal source of metastases. CSCs for human pancreatic ductal carcinoma (PDAC) have been identified, but neither the metastatic potential nor the chemoresistance of these cells has been adequately evaluated. We have addressed these issues by examining side-population (SP) cells isolated from the Panc-1 and BxPC3 lines of human PDAC cells, the oncogenotypes of which differ. SP cells could be isolated from monolayers of Panc-1, but only from spheroids of BxPC3. Using orthotopic xenografts into the severely immunocompromised NSG mouse, we found that SP cells isolated from both cell lines produced tumors that were highly metastatic, in contrast to previous experience with PDAC cell lines. SP cells derived from both cell lines expressed the ABCG2 transporter, which was demonstrably responsible for the SP phenotype. SP cells gave rise to non-SP (NSP) cells in vitro and in vivo, a transition that was apparently due to posttranslational inhibition of the ABCG2 transporter. Twenty-two other lines of PDAC cells also expressed ABCG2. The sensitivity of PDAC SP cells to the vinca alkaloid vincristine could be greatly increased by verapamil, a general inhibitor of transporters. In contrast, verapamil had no effect on the killing of PDAC cells by gemcitabine, the current first-line therapeutic for PDAC. We conclude that the isolation of SP cells can be a convenient and effective tool for the study of PDAC CSCs; that CSCs may be the principal progenitors of metastasis by human PDAC; that the ABCG2 transporter is responsible for the SP phenotype in human PDAC cells, and may be a ubiquitous source of drug-resistance in PDAC, but does not confer resistance to gemcitabine; and that inhibition of ABCG2 might offer a useful adjunct in a therapeutic attack on the CSCs of PDAC.

Clinical significance of OCT4 and SOX2 protein expression in cervical cancer

Background

Cancer stem cell markers have become a major research focus because of their relationship with radiation or chemotherapy resistance in cancer therapy. Cancer stem cell markers including OCT4 and SOX2 have been found in various solid tumors. Here, we investigate the expression and clinical significance of OCT4 and SOX2 in cervical cancer.

Methods

To define the clinical significance of OCT4 and SOX2 expression, we performed immunohistochemistry for OCT4 and SOX2 on 305 normal cervical epithelium samples, 289 cervical intraepithelial neoplasia samples, and 161 cervical cancer cases and compared the data with clinicopathologic factors, including survival rates of patients with cervical cancer.

Results

OCT4 and SOX2 expression was higher in cervical cancer than normal cervix (both p < 0.001). OCT4 overexpression was associated with lymphovascular space invasion (p = 0.045), whereas loss of SOX2 expression was correlated with large tumor size (p = 0.015). Notably, OCT4 and SOX2 were significantly co-expressed in premalignant cervical lesions, but not in malignant cervical tumor. OCT4 overexpression showed worse 5-year disease-free and overall survival rates (p = 0.012 and p = 0.021, respectively) when compared to the low-expression group, while SOX2 expression showed favorable overall survival (p = 0.025). Cox regression analysis showed that OCT4 was an independent risk factor (hazard ratio = 11.23, 95 % CI, 1.31 - 95.6; p = 0.027) for overall survival while SOX2 overexpression showed low hazard ratio for death (hazard ratio = 0.220, 95 % CI, 0.06–0.72; p = 0.013).

Conclusions

These results suggest that OCT4 overexpression and loss of SOX2 expression are strongly associated with poor prognosis in patients with cervical cancer.

Targeting self-renewal pathways in cancer stem cells: clinical implications for cancer therapy

Extensive cancer research in the past few decades has identified the existence of a rare subpopulation of stem cells in the grove of cancer cells. These cells are known as the cancer stem cells marked by the presence of surface biomarkers, multi-drug resistance pumps and deregulated self-renewal pathways (SRPs). They have a crucial role in provoking cancer cells leading to tumorigenesis and its progressive metastasis. Cancer stem cells (CSCs) are much alike to normal stem cells in their self-renewal mechanisms. However, deregulations in the SRPs are seen in CSCs, making them resistant to conventional chemotherapeutic agents resulting in the tumor recurrence. Current treatment strategies in cancer fail to detect and differentiate the CSCs from their non-tumorigenic progenies owing to absence of specific biomarkers. Now, it has become imperative to understand complex functional biology of CSCs, especially the signaling pathways to design improved treatment strategies to target them. It is hopeful that the SRPs in CSCs offer a promising target to alter their survival strategies and impede their tumorigenic potential. However, there are many perils associated with the direct targeting method by conventional therapeutic agents such as off targets, poor bioavailability and poor cellular distribution. Recent evidences have shown an increased use of small molecule antagonists directly to target these SRPs may lead to severe side-effects. An alternative to solve these issues could be an appropriate nanoformulation. Nanoformulations of these molecules could provide an added advantage for the selective targeting of the pathways especially Hedgehog, Wnt, Notch and B-cell-specific moloney murine leukemia virus integration site 1 in the CSCs while sparing the normal stem cells. Hence, to achieve this goal a complete understanding of the molecular pathways corroborate with the use of holistic nanosystem (nanomaterial inhibition molecule) could possibly be an encouraging direction for future cancer therapy.

Minnelide effectively eliminates CD133(+) side population in pancreatic cancer

Background

Pancreatic Ductal Adenocarcinoma (PDAC) is a devastating disease hallmarked by limited patient survival. Resistance to chemotherapy, a major cause of treatment failure in PDAC patients, is often attributed to Cancer Stem Cells (CSCs). Pancreatic CSCs are a small subset of quiescent cells within a tumor represented by surface markers like CD133. These cells are responsible not only for tumor recurrence, but also poor prognosis based on their “stem-like” characteristics. At present, conventional therapy is directed towards rapidly dividing PDAC cells and thus fails to target the CSC population.

Methods

MIA PaCa-2, S2-013 and AsPC-1 were treated with 12.5 nM triptolide (12 T cells) for 7 days. The surviving cells were recovered briefly in drug-free growth media and then transferred to Cancer Stem cell Media (CSM). As a control, untreated cells were also transferred to CSM media (CSM). The 12 T and CSM cells were tested for stemness properties using RNA and protein markers. Low numbers of CSM and 12 T cells were implanted subcutaneously in athymic nude mice to study their tumorigenic potential. 12 T and CSM cells were sorted for CD133 expression and assayed for their colony forming ability and sphere forming ability. Invasiveness of 12 T cells, CSM and MIA PaCa-2 were compared using Boyden chamber assays.

Results

Treated 12 T cells displayed increased expression of the surface marker CD133 and the drug transporter ABCG2 compared to untreated cells (CSM cells). Both 12 T and CSM cells formed subcutaneous tumors in mice confirming their tumor-initiating properties. When tested for invasion, 12 T cells had increased invasiveness compared to CSM cells. CD133⁺ cells in both CSM and 12 T showed greater colony and sphere forming ability compared to CD133⁻ cells from each group. Consistent with these data, when injected subcutaneously in mice, CD133⁻ cells from CSM or 12 T did not form any tumors whereas CD133⁺ cells from both groups showed tumor formation at a very low cell number. Despite pre-exposure to triptolide in 12 T CD133⁺ cells, treatment of tumors formed by these cells with Minnelide, a triptolide pro-drug, showed significant tumor regression.

Conclusion

Our results indicated that triptolide enhanced and enriched the “stemness” in the PDAC cell lines at a low dose of 12.5 nM, but also resulted in the regression of tumors derived from these cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0470-6) contains supplementary material, which is available to authorized users.

Role of RHOT1 on migration and proliferation of pancreatic cancer

Pancreatic cancer (PC) is one of the most malignant tumors. Rho GTPases can affect several types of human cancers, including PC. In this study, we investigated the role of Ras homolog family member T1 (RHOT1), a new member of Rho GTPases in PC. IHC results showed that RHOT1 was expressed significantly higher in PC tissues than paracancerous tissues (P<0.01) and SMAD family member 4 (SMAD4) was expressed lower in PC tissues (P<0.01). RHOT1 was widely expressed in PC cell lines analyzed by reverse transcription PCR (RT-PCR), real-time quantitative PCR (RT-qPCR) and western blotting (WB). SiRNA-RHOT1 significantly suppressed the proliferation and migration of SW1990 cells. Moreover, SMAD4 was identified as an effector of RHOT1. Our findings suggest that RHOT1 can regulate cell migration and proliferation by suppressing the expression of SMAD4 in PC, which may provide a novel sight to explore the mechanism and therapeutic strategy for PC.

Dendritic cells loaded with pancreatic Cancer Stem Cells (CSCs) lysates induce antitumor immune killing effect in vitro

According to the cancer stem cells (CSCs) theory, malignant tumors may be heterogeneous in which a small population of CSCs drive the progression of cancer. Because of their intrinsic abilities, CSCs may survive a variety of treatments and then lead to therapeutic resistance and cancer recurrence. Pancreatic CSCs have been reported to be responsible for the malignant behaviors of pancreatic cancer, including suppression of immune protection. Thus, development of immune strategies to eradicate pancreatic CSCs may be of great value for the treatment of pancreatic cancer. In this study, we enriched pancreatic CSCs by culturing Panc-1 cells under sphere-forming conditions. Panc-1 CSCs expressed low levels of HLA-ABC and CD86, as measured by flow cytometry analysis. We further found that the Panc-1 CSCs modulate immunity by inhibiting lymphocyte proliferation which is promoted by phytohemagglutinin (PHA) and anti-CD3 monoclonal antibodies. The monocyte derived dendritic cells (DCs) were charged with total lysates generated from Panc-1 CSCs obtained from tumor sphere culturing. After co-culturing with lymphocytes at different ratios, the Panc-1 CSCs lysates modified DC effectively promoted lymphocyte proliferation. The activating efficiency reached 72.4% and 74.7% at the ratios of 1∶10 and 1∶20 with lymphocytes. The activated lymphocytes secreted high levels of INF-γ and IL-2, which are strong antitumor cytokines. Moreover, Panc-1 CSCs lysates modified DC induced significant cytotoxic effects of lymphocytes on Panc-1 CSCs and parental Panc-1 cells, respectively, as shown by lactate dehydrogenase (LDH) assay. Our study demonstrates that the development of CSCs-based vaccine is a promising strategy for treating pancreatic cancer.

The IL-8/CXCR1 axis is associated with cancer stem cell-like properties and correlates with clinical prognosis in human pancreatic cancer cases

CXCR1, a receptor for CXCL8/IL-8, has recently been demonstrated to be associated with cancer stem cell (CSC) populations in certain types of human cancers. However, the effect of CXCR1 on CSC and its prognostic value in human pancreatic cancer remain unknown. In this study, we evaluated the expression of CXCR1 in human pancreatic duct adenocarcinoma (PDAC) and found that positive CXCR1 expression correlated with lymph node metastasis (P = 0.017) and a poor survival rate (HR, 3.748; 95% CI, 1.822 to 7.712; P < 0.001) in patients with PDAC. In addition, we identified significant positive correlations between CXCR1 and CD44 (P = 0.002) and CD133 (P = 0.017). Further functional studies confirmed that IL-8 addition increased sphere formation, CSC populations, and cell invasion of pancreatic cancer cells and that these effects could be reversed by antagonizing CXCR1 with a CXCR1-specific antibody. Therefore, our study demonstrated that the IL-8/CXCR1 axis is associated with the CSC-like properties of pancratic cancer cells and prognosis in human pancreatic cancer. This suggested a way of targeting pancreatic CSCs by disrupting IL-8/CXCR1 axis.