Hypoxia-induced aggressiveness of pancreatic cancer cells is due to increased expression of VEGF, IL-6 and miR-21, which can be attenuated by CDF treatment. PLoS One. 2012;7:e50165. [PMID: 23272057 PMCID: PMC3521759 DOI: 10.1371/journal.pone.0050165]

PTEN inhibits macrophage polarization from M1 to M2 through CCL2 and VEGF-A reduction and NHERF-1 synergism

PTEN has been studied in several tumor models as a tumor suppressor. In this study, we explored the role of PTEN in the inhibition state of polarized M2 subtype of macrophage in tumor microenvironment (TME) and the underlying mechanisms. To elucidate the potential effect in TME, RAW 264.7 macrophages and 4T1 mouse breast cancer cells were co-cultured to reconstruct tumor microenvironment. After PTEN was down-regulated with shRNA, the expression of CCL2 and VEGF-A, which are definited to promote the formation of M2 macrophages, have a dramatically increase on the level of both gene and protein in co-cultured RAW 264.7 macrophages. And at the same time, NHERF-1 (Na(+)/H(+) exchanger regulating factor-1), another tumor suppressor has a similar tendency to PTEN. Q-PCR and WB results suggested that PTEN and NHERF-1 were consistent with one another no matter at mRNA or protein level when exposed to the same stimulus. Coimmunoprecipitation and immunofluorescence techniques confirmed that PTEN and NHERF-1 were coprecipitated, and NHERF-1 protein expression was properly reduced with rCCL2 effect. In addition, cell immunofluorescence images revealed a profound transferance, in co-cultured RAW 264.7 macrophages, an up-regulation of NHERF-1 could promote the PTEN marked expression on the cell membrane, and this form for the interaction was not negligible. These observations illustrate PTEN with a certain synergy of NHERF-1, as well as down-regulation of CCL2 suppressing M2 macrophage transformation pathway. The results suggest that the activation of PTEN and NHERF-1 may impede the evolution of macrophages beyond the M1 into M2 phenotype in tumor microenvironment.

Emerging role of microRNAs in cancer stem cells: Implications in cancer therapy

A small subset of cancer cells that act as tumor initiating cells or cancer stem cells (CSCs) maintain self-renewal and growth promoting capabilities of cancer and are responsible for drug/treatment resistance, tumor recurrence and metastasis. Due to their potential clinical importance, many researchers have put their efforts over decades to unravel the molecular mechanisms that regulate CSCs functions. MicroRNAs (miRNAs) which are 21-23 nucleotide long, endogenous non-coding RNAs, regulate gene expression through gene silencing at post-transcriptional level by binding to the 3'-untranslated regions or the open reading frames of target genes, thereby result in target mRNA degradation or its translational repression and serve important role in several cellular, physiological and developmental processes. Aberrant miRNAs expression and their implication in CSCs regulation by controlling asymmetric cell division, drug/treatment resistance and metastasis make miRNAs a tool of great therapeutic potential against cancer. Recent advancements on the biological complexities of CSCs, modulation in CSCs properties by miRNA network and development of miRNA based treatment strategies specifically targeting the CSCs as an attractive therapeutic targets for clinical application are being critically analysed.

MicroRNA-21 coordinates human multipotent cardiovascular progenitors therapeutic potential

Published clinical trials in patients with ischemic diseases show limited benefit of adult stem cell-based therapy, likely due to their restricted plasticity and commitment toward vascular cell lineage. We aim to uncover the potent regenerative ability of MesP1/stage-specific embryonic antigen 1 (SSEA-1)-expressing cardiovascular progenitors enriched from human embryonic stem cells (hESCs). Injection of only 10(4) hESC-derived SSEA-1(+) /MesP1(+) cells, or their progeny obtained after treatment with VEGF-A or PDGF-BB, was effective enough to enhance postischemic revascularization in immunodeficient mice with critical limb ischemia (CLI). However, the rate of incorporation of hESC-derived SSEA-1(+) /MesP1(+) cells and their derivatives in ischemic tissues was modest. Alternatively, these cells possessed a unique miR-21 signature that inhibited phosphotase and tensin homolog (PTEN) thereby activating HIF-1α and the systemic release of VEGF-A. Targeting miR-21 limited cell survival and inhibited their proangiogenic capacities both in the Matrigel model and in mice with CLI. We next assessed the impact of mR-21 in adult angiogenesis-promoting cells. We observed an impaired postischemic angiogenesis in miR-21-deficient mice. Notably, miR-21 was highly expressed in circulating and infiltrated monocytes where it targeted PTEN/HIF-1α/VEGF-A signaling and cell survival. As a result, miR-21-deficient mice displayed an impaired number of infiltrated monocytes and a defective angiogenic phenotype that could be partially restored by retransplantation of bone marrow-derived cells from wild-type littermates. hESC-derived SSEA-1(+) /MesP1(+) cells progenitor cells are powerful key integrators of therapeutic angiogenesis in ischemic milieu and miR-21 is instrumental in this process as well as in the orchestration of the biological activity of adult angiogenesis-promoting cells.

miRNA therapy targeting cancer stem cells: a new paradigm for cancer treatment and prevention of tumor recurrence

Cancer stem cells (CSCs) are a small subpopulation of cells within tumors that retain the properties of self-renewal and tumorigenicity in vivo. Although CSCs have been reported in multiple cancers, the regulation of CSCs has not been described at the molecular level. miRNAs are endogenous small noncoding RNAs that post-transcriptionally regulate the expression of their target genes via RNA interference and are involved in almost all cellular processes. Since aberrant miRNA expression occurs in CSCs, such dysregulated miRNAs may be promising therapeutic targets. In this review, we summarize the current knowledge regarding miRNAs that regulate CSC properties and discuss an in vivo delivery system for synthetic miRNA mimics and miRNA inhibitors for the development of innovative miRNA therapy against CSCs.

New targeted therapies in pancreatic cancer

Patients with pancreatic cancer have a poor prognosis with a median survival of 4-6 mo and a 5-year survival of less than 5%. Despite therapy with gemcitabine, patient survival does not exceed 6 mo, likely due to natural resistance to gemcitabine. Therefore, it is hoped that more favorable results can be obtained by using guided immunotherapy against molecular targets. This review summarizes the new leading targeted therapies in pancreatic cancers, focusing on passive and specific immunotherapies. Passive immunotherapy may have a role for treatment in combination with radiochemotherapy, which otherwise destroys the immune system along with tumor cells. It includes mainly therapies targeting against kinases, including epidermal growth factor receptor, Ras/Raf/mitogen-activated protein kinase cascade, human epidermal growth factor receptor 2, insulin growth factor-1 receptor, phosphoinositide 3-kinase/Akt/mTOR and hepatocyte growth factor receptor. Therapies against DNA repair genes, histone deacetylases, microRNA, and pancreatic tumor tissue stromal elements (stromal extracellular matric and stromal pathways) are also discussed. Specific immunotherapies, such as vaccines (whole cell recombinant, peptide, and dendritic cell vaccines), adoptive cell therapy and immunotherapy targeting tumor stem cells, have the role of activating antitumor immune responses. In the future, treatments will likely include personalized medicine, tailored for numerous molecular therapeutic targets of multiple pathogenetic pathways.

Interactional role of microRNAs and bHLH-PAS proteins in cancer (Review)

MicroRNAs (miRNAs) are recognized as an emerging class of master regulators that regulate human gene expression at the post-transcriptional level and are involved in many normal and pathological cellular processes. Mammalian basic HLH (helix-loop-helix)-PER-ARNT-SIM (bHLH-PAS) proteins are heterodimeric transcriptional regulators that sense and respond to environmental signals (such as chemical pollutants) or to physiological signals (for instance hypoxia). In the normal state, bHLH-PAS proteins are responsible for multiple critical aspects of physiology to ensure the cell accurate homeostasis, but dysregulation of these proteins has been shown to contribute to carcinogenic events such as tumor initiation, promotion, and progression. Increasing epidemiological and experimental studies have shown that bHLH-PAS proteins regulate a panel of miRNAs, whereas some miRNAs also target bHLH-PAS proteins. The interaction between miRNAs and certain bHLH-PAS proteins [hypoxia-inducible factor (HIF) and aryl hydrocarbon receptor (AHR)] is relevant to many vital events associated with tumorigenesis. This review will summarize recent findings on the interesting and complicated underlying mechanisms that miRNAs interact with HIFs or AHR in tumors, hopefully to benefit the discovery of novel drug-interfering targets for cancer therapy.

Antioxidant Mechanisms and ROS-Related MicroRNAs in Cancer Stem Cells

Increasing evidence indicates that most of the tumors are sustained by a distinct population of cancer stem cells (CSCs), which are responsible for growth, metastasis, invasion, and recurrence. CSCs are typically characterized by self-renewal, the key biological process allowing continuous tumor proliferation, as well as by differentiation potential, which leads to the formation of the bulk of the tumor mass. CSCs have several advantages over the differentiated cancer cell populations, including the resistance to radio- and chemotherapy, and their gene-expression programs have been shown to correlate with poor clinical outcome, further supporting the relevance of stemness properties in cancer. The observation that CSCs possess enhanced mechanisms of protection from reactive oxygen species (ROS) induced stress and a different metabolism from the differentiated part of the tumor has paved the way to develop drugs targeting CSC specific signaling. In this review, we describe the role of ROS and of ROS-related microRNAs in the establishment and maintenance of self-renewal and differentiation capacities of CSCs.

Hypoxia-induced miR-181b enhances angiogenesis of retinoblastoma cells by targeting PDCD10 and GATA6

Previous findings showed that miR-181b is upregulated under hypoxic conditions in retinoblastoma cells. Since hypoxia is a common feature of retinoblastoma that affects tumor progression as well as tumor therapy, in the present study, we investigated the regulatory mechanism of miR-181b under hypoxic conditions, and examined the role of miR-181b in retinoblastoma responses to hypoxia (chemoresistance and angiogenesis) and possible downstream genes. The level of hypoxia-inducible factor-1α (HIF-1α) and miR-181b was detected to examine the link between them. Tube formation and cell cytotoxicity assays were used to clarify the effects of miR-181b on hypoxic responses of retinoblastoma cells. Bioinformatics analysis was performed to predict potential targets of miR-181b and western blotting was used to verify these targets. The results showed a significantly increased expression of HIF-1α in hypoxia-treated retinoblastoma cells. Downregulation of HIF-1α using a small-interfering RNA (siRNA) knockdown technology did not decrease the expression of miR-181b. Through gain- and loss-of-function studies, miR-181b was demonstrated to significantly stimulate the ability of capillary tube formation of endothelial cells. Programmed cell death-10 (PDCD10) and GATA binding protein 6 (GATA6) were identified as the target genes of miR‑181b. To the best of our knowledge, results of the present study provide the first evidence that miR-181b was upregulated by hypoxia in retinoblastoma in an HIF-1α-independent manner. miR-181b increased tumor angiogenesis of retinoblastoma cells. Additionally, miR-181b exerts its angiogenic function, at least in part, by inhibiting PDCD10 and GATA6. Thus, it is a new potentially useful therapeutic target for retinoblastoma.

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.

Contribution of microRNAs in understanding the pancreatic tumor microenvironment involving cancer associated stellate and fibroblast cells

Understanding of molecular events associated with tumor microenvironment in pancreatic cancer (PC) is an active area of research especially because of the rich desmoplasia seen in human PC. Desmoplasia is contributed by several cell types including cancer-associated fibroblast (CAF) and stellate cells (PSCs), which are believed to play critical roles in conferring aggressiveness to PC. The aberrant expression of microRNAs (miRNAs) in PSCs and CAF cells appears to play a pivotal role in the development and progression of PC. In this study, expression analysis of miR-21/miR-221 in conditioned media derived from PSCs/CAF cells, and from PSCs/CAF cells showed up-regulation of both miRNAs compared to MIAPaCa-2 PC cells. In addition, miR-21 expression in stellate cells derived from normal pancreas was substantially lower when compared to PSCs or CAF cells. COLO-357 PC cells cultured in the presence of conditioned media derived from PSC/CAF cells led to a significant increase in clonogenicity and pancreatosphere formation. Furthermore, inhibition of miR-21 with antisense oligonucleotide (ASO) transfection resulted in decreased migration/invasive capacity of PSCs. Similarly, the effect of ASO-miR-221 transfection in CAF cells reduced the expression of NF-κB and K-Ras (target of miR-221) along with inhibition of migration/invasion. Moreover, miRNA expression profiling of PSCs, MIAPaCa-2, and COLO-357 cells, and further validation by real-time PCR, showed several differentially expressed miRNAs, among which four was significantly up-regulated. Collectively, these results suggest a crosstalk between PSCs/CAF cells and PC cells, resulting in the up-regulation of miR-21/miR-221 expression which in part may confer aggressiveness to PC. We conclude that targeting these miRNAs could be useful for developing precision medicine for the prevention of tumor progression and/or for the treatment of PC.

Inhibition of IL-6 signaling significantly reduces primary tumor growth and recurrencies in orthotopic xenograft models of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal human tumors, with radical surgical resection as the only curative treatment option. However, resection is only possible in a small fraction of patients, and about 80% of the patients develop recurrencies. PDAC development is facilitated by the cytokine interleukin-6 (IL-6), which acts via classic and trans-signaling. Both pathways are inhibited by the anti-IL-6-receptor antibody tocilizumab, whereas the fusion protein sgp130Fc specifically blocks trans-signaling. Here, we show that conservative or adjuvant therapy with both inhibitors reduces tumor growth in an orthotopic model of human Colo357 cells in SCID/bg mice. In the conservative setting, median primary tumor weight was reduced 2.4-fold for tocilizumab and 4.4-fold for sgp130Fc. sgp130Fc additionally led to a decrease in microvessel density, which was not observed with tocilizumab. In the adjuvant therapeutic setting after surgical resection of the primary tumor, treatment with tocilizumab or sgp130Fc decreased the local recurrence rate from 87.5% in the control group to 62.5 or 50%, respectively. Furthermore, the median weight of the local recurrent tumors was clearly diminished, and both inhibitors reduced the number of distant metastases. A significant reduction of tumor weight and metastases-comparable to gemcitabine treatment-was also observed with both inhibitors in another model using the poorly differentiated PancTuI cells. Our findings demonstrate the inhibition of IL-6 as a new treatment option in PDAC.

Insights into the Role of microRNAs in Pancreatic Cancer Pathogenesis: Potential for Diagnosis, Prognosis, and Therapy

Pancreatic cancer is a highly lethal malignancy and a fourth leading cause of cancer-related death in the United States. Poor survival of pancreatic cancer patients is largely because of its asymptomatic progression to advanced stage against which no effective therapy is currently available. Over the years, we have developed significant knowledge of molecular progression of pancreatic cancer and identified several genetic and epigenetic aberrations to be involved in its etiology and aggressive behavior. In that regard, recent lines of evidence have suggested important roles of microRNAs (miRNAs/miRs) in pancreatic cancer pathogenesis. microRNAs belonging to a family of small, noncoding RNAs are able to control diverse biological processes due to their ability to regulate gene expression at the posttranscriptional level. Accordingly, dysregulation of miRNAs can lead to several disease conditions, including cancer. There is a long list of microRNAs that exhibit aberrant expression in pancreatic cancer and serve as key microplayers in its initiation, progression, metastasis, and chemoresistance. These findings have suggested that microRNAs could be exploited as novel biomarkers for diagnostic and prognostic assessments of pancreatic cancer and as targets for therapy. This book chapter describes clinical problems associated with pancreatic cancer, roles that microRNAs play in various aspects of pancreatic cancer pathogenesis, and envision opportunities for potential use of microRNAs in pancreatic cancer management.

Metformin may function as anti-cancer agent via targeting cancer stem cells: the potential biological significance of tumor-associated miRNAs in breast and pancreatic cancers

Metformin is one of the most used diabetic drugs for the management of type II diabetes mellitus (DM) in the world. Increased numbers of epidemiological and clinical studies have provided convincing evidence supporting the role of metformin in the development and progression of a variety of human tumors including breast and pancreatic cancer. Substantial pre-clinical evidence from in vitro and in vivo experimental studies strongly suggests that metformin has an anti-cancer activity mediated through the regulation of several cell signaling pathways including activation of AMP kinase (AMPK), and other direct and indirect mechanisms; however, the detailed mechanism(s) has not yet been fully understood. The concept of cancer stem cells (CSCs) has gained significant attention in recent years due its identification and defining its clinical implications in many different tumors including breast cancer and pancreatic cancer. In this review, we will discuss the protective role of metformin in the development of breast and pancreatic cancers. We will further discuss the role of metformin as an anti-cancer agent, which is in part mediated through targeting CSCs. Finally, we will discuss the potential role of metformin in the modulation of tumor-associated or CSC-associated microRNAs (miRNAs) as part of the novel mechanism of action of metformin in the development and progression of breast and pancreatic cancers.

Molecular mechanisms underlying the role of microRNAs in the chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an extremely severe disease where the mortality and incidence rates are almost identical. This is mainly due to late diagnosis and limited response to current treatments. The tumor macroenvironment/microenvironment have been frequently reported as the major contributors to chemoresistance in PDAC, preventing the drugs from reaching their intended site of action (i.e., the malignant duct cells). However, the recent discovery of microRNAs (miRNAs) has provided new directions for research on mechanisms underlying response to chemotherapy. Due to their tissue-/disease-specific expression and high stability in tissues and biofluids, miRNAs represent new promising diagnostic and prognostic/predictive biomarkers and therapeutic targets. Furthermore, several studies have documented that selected miRNAs, such as miR-21 and miR-34a, may influence response to chemotherapy in several tumor types, including PDAC. In this review, we summarize the current knowledge on the role of miRNAs in PDAC and recent advances in understanding their role in chemoresistance through multiple molecular mechanisms.

Novel therapeutic targets for pancreatic cancer

Pancreatic cancer has become the fourth leading cause of cancer death in the last two decades. Only 3%-15% of patients diagnosed with pancreatic cancer had 5 year survival rate. Drug resistance, high metastasis, poor prognosis and tumour relapse contributed to the malignancies and difficulties in treating pancreatic cancer. The current standard chemotherapy for pancreatic cancer is gemcitabine, however its efficacy is far from satisfactory, one of the reasons is due to the complex tumour microenvironment which decreases effective drug delivery to target cancer cell. Studies of the molecular pathology of pancreatic cancer have revealed that activation of KRAS, overexpression of cyclooxygenase-2, inactivation of p16^INK4A and loss of p53 activities occurred in pancreatic cancer. Co-administration of gemcitabine and targeting the molecular pathological events happened in pancreatic cancer has brought an enhanced therapeutic effectiveness of gemcitabine. Therefore, studies looking for novel targets in hindering pancreatic tumour growth are emerging rapidly. In order to give a better understanding of the current findings and to seek the direction in future pancreatic cancer research; in this review we will focus on targets suppressing tumour metastatsis and progression, KRAS activated downstream effectors, the relationship of Notch signaling and Nodal/Activin signaling with pancreatic cancer cells, the current findings of non-coding RNAs in inhibiting pancreatic cancer cell proliferation, brief discussion in transcription remodeling by epigenetic modifiers (e.g., HDAC, BMI1, EZH2) and the plausible therapeutic applications of cancer stem cell and hyaluronan in tumour environment.

Atypical cell populations associated with acquired resistance to cytostatics and cancer stem cell features: the role of mitochondria in nuclear encapsulation

Until recently, acquired resistance to cytostatics had mostly been attributed to biochemical mechanisms such as decreased intake and/or increased efflux of therapeutics, enhanced DNA repair, and altered activity or deregulation of target proteins. Although these mechanisms have been widely investigated, little is known about membrane barriers responsible for the chemical imperviousness of cell compartments and cellular segregation in cytostatic-treated tumors. In highly heterogeneous cross-resistant and radiorefractory cell populations selected by exposure to anticancer agents, we found a number of atypical recurrent cell types in (1) tumor cell cultures of different embryonic origins, (2) mouse xenografts, and (3) paraffin sections from patient tumors. Alongside morphologic peculiarities, these populations presented cancer stem cell markers, aberrant signaling pathways, and a set of deregulated miRNAs known to confer both stem-cell phenotypes and highly aggressive tumor behavior. The first type, named spiral cells, is marked by a spiral arrangement of nuclei. The second type, monastery cells, is characterized by prominent walls inside which daughter cells can be seen maturing amid a rich mitochondrial environment. The third type, called pregnant cells, is a giant cell with a syncytium-like morphology, a main nucleus, and many endoreplicative functional progeny cells. A rare fourth cell type identified in leukemia was christened shepherd cells, as it was always associated with clusters of smaller cells. Furthermore, a portion of resistant tumor cells displayed nuclear encapsulation via mitochondrial aggregation in the nuclear perimeter in response to cytostatic insults, probably conferring imperviousness to drugs and long periods of dormancy until nuclear eclosion takes place. This phenomenon was correlated with an increase in both intracellular and intercellular mitochondrial traffic as well as with the uptake of free extracellular mitochondria. All these cellular disorders could, in fact, be found in untreated tumor cells but were more pronounced in resistant entities, suggesting a natural mechanism of cell survival triggered by chemical injury, or a primitive strategy to ensure stemming, self-renewal, and differentiation under adverse conditions, a fact that may play a significant role in chemotherapy outcomes.

Interleukin-6: a villain in the drama of pancreatic cancer development and progression

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with a poor prognosis and little treatment options. The development and progression of the disease is fostered by inflammatory cells and cytokines. One of these cytokines is interleukin-6 (IL-6), which plays an important role in a wide range of biologic activities.

DATA SOURCES

A systematic search of PubMed was performed to identify relevant studies using key words such as interleukin-6, inflammatory cytokines, inflammation and pancreatic cancer or PDAC. Articles related to IL-6 and pancreatic cancer were systematically reviewed.

RESULTS

IL-6 is elevated in the serum of pancreatic cancer patients and correlates with cachexia, advanced tumor stage and poor survival. Its expression is enhanced by hypoxia and proteins involved in pancreatic cancer development like Kras, mesothelin or ZIP4. IL-6 in turn contributes to the generation of a pro-tumorigenic microenvironment and is probably involved in angiogenesis and metastasis. In experimental mouse models of PDAC, IL-6 was important for the development and progression of precursor lesions.

CONCLUSION

IL-6 emerges as a key player in pancreatic cancer development and progression, and hence should be considered as a new therapeutic target.

Regulation of SOD2 and β-arrestin1 by interleukin-6 contributes to the increase of IGF-1R expression in docetaxel resistant prostate cancer cells

Although several mechanisms behind resistance to docetaxel in castration-refractory prostate cancer (CRPC) have been investigated, molecular determinants of evolved resistance are still not entirely understood. Proteomics-based analysis in this study revealed that SOD2, associated with downregulation of reactive oxygen species (ROS), was significantly up-regulated in docetaxel-resistant (PC3/Doc) cells if compared to sensitive cells, and the expression of redox-regulated genes such as IGF-1R, CXCR4, and BCL2 was increased as well. Forced expression of SOD2 in sensitive cells led to the increase of IGF-1R and association with drug resistance, whereas silencing of SOD2 resulted in the decrease of IGF-1R at the protein level in resistant cells. Further study revealed that SOD2 acted as a negative regulator of β-arrestin1 that is an important adaptor responsible for degradation of IGF-1R via the changes in ROS, as evidenced by observations that an antioxidant agent substantially attenuated β-arrestin1 expression in vitro and in vivo. Finally, we found that blocking of IL6 that was up-regulated in resistant cells resulted in attenuation of SOD2 and STAT3, and simultaneously in increased expression of β-arrestin1. The modulation consequently led to the decreased IGF-1R at both protein and transcription levels. Together, our data provide a novel explanation that high level of IL6 stimulated SOD2 expression that, at least partially, contributed to the low level of ROS that would likely result in a sustained increase in the expression of IGF-1R through abolishment of β-arrestin1 in docetaxel resistant cells.

Chemical approaches to targeting drug resistance in cancer stem cells

Cancer stem cells (CSCs) are a subpopulation of cancer cells with high clonogenic capacity and ability to reform parental tumors upon transplantation. Resistance to therapy has been shown for several types of CSC and, therefore, they have been proposed as the cause of tumor relapse. Consequently, much effort has been made to design molecules that can target CSCs specifically and sensitize them to therapy. In this review, we summarize the mechanisms underlying CSC resistance, the potential biological targets to overcome resistance and the chemical compounds showing activity against different types of CSC. The chemical compounds discussed here have been divided according to their origin: natural, natural-derived and synthetic compounds.

Inflammation and pancreatic cancer: disease promoter and new therapeutic target

Chronic inflammation has a certain impact on the carcinogenesis of the digestive organs. The characteristic tissue structure of pancreatic cancer, desmoplasia, results from inflammatory processes induced by cancer cells and stromal cells. Concerning the progression of pancreatic cancer, recent research has clarified the pivotal role of tumor-stromal interaction, which promotes the development of an invasive phenotype of cancer and provides survival advantages against chemotherapeutic agents or immune surveillance. Tumor stromal cells such as pancreatic stellate cells and immune cells establish a microenvironment that protects cancer cells through complex interactions. The microenvironment of pancreatic cancer acts as a niche for pancreatic cancer stem cells from which therapy-resistance and disease recurrence develop. Inhibition of the stromal functions or restoration of the immune reaction against cancer cells has therapeutic benefits that enhance the efficacy of conventional therapies. Some of the recent advances in this field are now under evaluation in clinical settings, but many problems must be overcome to establish a radical therapy for pancreatic cancer. This review summarizes current knowledge about the tumor-promoting stromal functions, immune system modulation and therapeutic strategies targeting tumor-stromal interactions in pancreatic cancer.

MicroRNAs in personalized cancer therapy

MicroRNAs (miRNAs) are small endogenous noncoding single-stranded RNAs. They critically regulate the post-transcriptional activity of several key physiological and pathological cell processes including cancer. Through their transcriptional regulatory functions, miRNAs control tumor proliferation, invasion and metastasis. The expression of miRNAs is altered in malignancies. It could be either upregulated or downregulated depending upon the role of a particular miRNA in the pathogenetic development of the tumor. The upregulated miRNAs exert an 'oncogenic' effect leading to tumor proliferation and metastasis. The downregulated miRNAs have 'tumor suppressor' effects. Recent studies have demonstrated that miRNAs have a role in the early diagnosis, prognosis and treatment outcome assessment of cancers. Every tumor has specific miRNA alterations, i.e. some are overexpressed and others are downregulated. These altered miRNAs can be used as a tumor-specific 'signature' for potential clinical use in improving the accuracy of diagnosis, determining prognosis and as therapeutic targets for therapy. Specific miRNAs can be targeted using oligonucleotide sequences corresponding to the altered miRNAs. These are referred to as 'antagomirs'. Depending upon the miRNA alterations in the tumor of an individual patient, one could design targeted therapies for personalized medicine in patients. Hence, miRNAs have an immense role in personalized cancer therapy.

Hypoxia-inducible MiR-210 is an independent prognostic factor and contributes to metastasis in colorectal cancer

MicroRNA-210 (miR-210), the master hypoxamir, plays pleiotropic roles in certain cancers; however, its role in the development of human colorectal cancer remains unclear. Herein, we report that miR-210 is frequently up-regulated in colorectal cancer tissues, with high miR-210 expression significantly correlating with large tumor size, lymph node metastasis, advanced clinical stage and poor prognosis. Functionally, miR-210 overexpression promotes the migration and invasion of colorectal cancer cells. Furthermore, miR-210 can be induced by hypoxia and mediates the hypoxia-induced metastasis of colorectal cancer cells. In addition, vacuole membrane protein 1 (VMP1) is identified as the direct and functional target of miR-210. Thus, miR-210 is a useful biomarker for hypoxic tumor cells and a prognostic factor that plays an essential role in colorectal cancer metastasis.

The IL-6 feed-forward loop: a driver of tumorigenesis

IL-6 signaling plays a prominent role in tumorigenesis and metastasis. In this review we discuss the recent evidence describing the tumor intrinsic and extrinsic functions of this signaling pathway. Although blockade of this pathway in pre-clinical models leads to a reduction in tumor growth and metastasis, its clinical success is less evident. Thus, identifying the features of tumors/patients that predict response to anti-IL6 therapy are needed.

Targeting CSCs in tumor microenvironment: the potential role of ROS-associated miRNAs in tumor aggressiveness

Reactive oxygen species (ROS) have been widely considered as critical cellular signaling molecules involving in various biological processes such as cell growth, differentiation, proliferation, apoptosis, and angiogenesis. The homeostasis of ROS is critical to maintain normal biological processes. Increased production of ROS, namely oxidative stress, due to either endogenous or exogenous sources causes irreversible damage of bio-molecules such as DNA, proteins, lipids, and sugars, leading to genomic instability, genetic mutation, and altered gene expression, eventually contributing to tumorigenesis. A great amount of experimental studies in vitro and in vivo have produced solid evidence supporting that oxidative stress is strongly associated with increased tumor cell growth, treatment resistance, and metastasis, and all of which contribute to tumor aggressiveness. More recently, the data have indicated that altered production of ROS is also associated with cancer stem cells (CSCs), epithelial-to-mesenchymal transition (EMT), and hypoxia, the most common features or phenomena in tumorigenesis and tumor progression. However, the exact mechanism by which ROS is involved in the regulation of CSC and EMT characteristics as well as hypoxia- and, especially, HIF-mediated pathways is not well known. Emerging evidence suggests the role of miRNAs in tumorigenesis and progression of human tumors. Recently, the data have indicated that altered productions of ROS are associated with deregulated expression of miRNAs, suggesting their potential roles in the regulation of ROS production. Therefore, targeting ROS mediated through the deregulation of miRNAs by novel approaches or by naturally occurring anti-oxidant agents such as genistein could provide a new therapeutic approach for the prevention and/or treatment of human malignancies. In this article, we will discuss the potential role of miRNAs in the regulation of ROS production during tumorigenesis. Finally, we will discuss the role of genistein, as a potent anti-tumor agent in the regulation of ROS production during tumorigenesis and tumor development.

A mathematical model of HiF-1α-mediated response to hypoxia on the G1/S transition

Hypoxia is known to influence the cell cycle by increasing the G1 phase duration or by inducing a quiescent state (arrest of cell proliferation). This entry into quiescence is a mean for the cell to escape from hypoxia-induced apoptosis. It is suggested that some cancer cells have gain the advantage over normal cells to easily enter into quiescence when environmental conditions, such as oxygen pressure, are unfavorable [43,1]. This ability contributes in the appearance of highly resistant and aggressive tumor phenotypes [2]. The HiF-1α factor is the key actor of the intracellular hypoxia pathway. As tumor cells undergo chronic hypoxic conditions, HiF-1α is present in higher level in cancer than in normal cells. Besides, it was shown that genetic mutations promoting overstabilization of HiF-1α are a feature of various types of cancers [7]. Finally, it is suggested that the intracellular level of HiF-1α can be related to the aggressiveness of the tumors [53,24,4,10]. However, up to now, mathematical models describing the G1/S transition under hypoxia, did not take into account the HiF-1α factor in the hypoxia pathway. Therefore, we propose a mathematical model of the G1/S transition under hypoxia, which explicitly integrates the HiF-1α pathway. The model reproduces the slowing down of G1 phase under moderate hypoxia, and the entry into quiescence of proliferating cells under severe hypoxia. We show how the inhibition of cyclin D by HiF-1α can induce quiescence; this result provides a theoretical explanation to the experimental observations of Wen et al. (2010) [50]. Thus, our model confirms that hypoxia-induced chemoresistance can be linked, for a part, to the negative regulation of cyclin D by HiF-1α.

Alteration of pancreatic cancer cell functions by tumor-stromal cell interaction

Pancreatic cancer shows a characteristic tissue structure called desmoplasia, which consists of dense fibrotic stroma surrounding cancer cells. Interactions between pancreatic cancer cells and stromal cells promote invasive growth of cancer cells and establish a specific microenvironment such as hypoxia which further aggravates the malignant behavior of cancer cells. Pancreatic stellate cells (PSCs) play a pivotal role in the development of fibrosis within the pancreatic cancer tissue, and also affect cancer cell function. PSCs induce epithelial-mesenchymal transition and cancer stem cell (CSC)-related phenotypes in pancreatic cancer cells by activating multiple signaling pathways. In addition, pancreatic cancer cells and PSCs recruit myeloid-derived suppressor cells which attenuate the immune reaction against pancreatic cancer cells. As a result, pancreatic cancer cells become refractory against conventional therapies. The formation of the CSC-niche by stromal cells facilitates postoperative recurrence, re-growth of therapy-resistant tumors and distant metastasis. Conventional therapies targeting cancer cells alone have failed to conquer pancreatic cancer, but targeting the stromal cells and immune cells in animal experiments has provided evidence of improved therapeutic responses. A combination of novel strategies altering stromal cell functions could contribute to improving the pancreatic cancer prognosis.

Progress in research of hypoxia and angiogenesis in pancreatic cancer

Pancreatic cancer remains one of the most lethal solid tumors of the gastrointestinal tract. Hypoxia is the driving force behind angiogenesis in cancer. Angiogenesis is an essential factor for tumors to grow and metastasize. Studies in recent years have demonstrated that hypoxia and angiogenesis play important roles in the pathogenesis of pancreatic cancer. In this paper we will review recent advances in understanding the role of hypoxia and angiogenesis in the pathogenesis of pancreatic cancer.

Interleukin-6: an angiogenic target in solid tumours

During the past decade, incorporating anti-angiogenic agents into the therapeutic management of a myriad of malignancies has in certain cases made a significant impact on survival. However, the development of resistance to these drugs is inevitable and swift disease progression on their cessation often ensues. Hence, there is a drive to devise strategies that aim to enhance response to anti-angiogenic therapies by combining them with other targeted agents that facilitate evasion from resistance. The pleiotropic cytokine, interleukin-6 (IL-6), exerts pro-angiogenic effects in the tumour microenvironment of several solid malignancies and there is emerging evidence that reveals significant relationships between IL-6 signalling and treatment failure with antibodies directed against vascular endothelial growth factor (VEGF). This review summarises the role of IL-6 in pivotal angiogenic processes and preclinical/clinical research to support the future introduction of anti-IL-6 therapies to be utilised either in combination with other anti-angiogenic drugs or as a salvage therapy for patients with diseases that become refractory to these approaches.

Knockdown of Oct4 and Nanog expression inhibits the stemness of pancreatic cancer cells

Pancreatic cancer is notorious for its difficult diagnosis at early stage and poor recurrence-free prognosis. This study aimed to investigate the possible involvement of Oct4 and Nanog in pancreatic cancer. The high expressions of Oct4 and Nanog in human pancreatic cancer tissues were found to indicate a worse prognostic value of patients. The pancreatic cancer stem cells (PCSCs) that isolated from PANC-1 cell line by flow cytometry exhibited high expressions of Oct4 and Nanog. To investigate whether Oct4 and Nanog play crucial role in maintaining the stemness of PCSCs, double knockdown of Oct4 and Nanog demonstrated that Oct4 and Nanog significantly reduced proliferation, migration, invasion, chemoresistance, and tumorigenesis of PCSCs in vitro and in vivo. The altered expression of the genes related to pancreatic carcinogenesis, metastasis, drug resistance and epithelial-mesenchymal transdifferentiation (EMT) might affect the biological characteristics of PCSCs. Our results suggest that Oct4 and Nanog may serve as a potential marker of prognosis and a novel target of therapy for pancreatic cancer.

The metastasis suppressor, N-myc downregulated gene 1 (NDRG1), is a prognostic biomarker for human colorectal cancer

Metastasis remains to be one of the most prevalent causes leading to poor long-term survival of colorectal cancer (CRC) patients. The clinical significances of tumor metastatic suppressor, N-myc downregulated gene 1 (NDRG1), have been inconsistently reported in a variety of cancerous diseases. In this study with 240 CRC clinical specimens, we showed that NDRG1 expression was significantly decreased in most of CRC tissues compared to the paired non-tumor counterparts. Statistical analysis revealed a significant inverse correlation of NDRG1 expression with tumor stage, differentiation status and metastasis. Compared with NDRG1-negative group, NDRG1-positve group had better disease-free/overall survival (p = 0.000) over 5 years’ follow-up. Furthermore, NDRG1 was considered to be an independent prognostic factor for overall survival (p = 0.001) and recurrence (p = 0.003). Our study concludes that NDRG1 is a novel favorable predictor for the prognosis in CRC patients.

miR-210 regulates the interaction between pancreatic cancer cells and stellate cells

There is accumulating evidence that pancreatic stellate cells (PSCs) promote the progression of pancreatic cancer. microRNAs (miRNAs) are small non-coding RNAs acting as negative regulators of gene expression at the post-transcriptional level. This study aimed to clarify the role of miRNAs in the interaction between PSCs and pancreatic cancer cells. Pancreatic cancer cells were mono-cultured or indirectly co-cultured with PSCs. miRNAs were prepared, and Agilent's miRNA microarray containing probes for 904 human miRNAs was used to identify differentially expressed miRNAs. miR-210 was identified as an upregulated miRNA by co-culture with PSCs. Conditioned media of PSCs activated ERK and Akt, but not hypoxia-inducible factor-1α pathway. PSCs-induced miR-210 upregulation was inhibited by inhibitors of ERK and PI3K/Akt pathways. Inhibition of miR-210 expression decreased migration, decreased the expression of vimentin and snai-1, and increased the membrane-associated expression of β-catenin in Panc-1 cells co-cultured with PSCs. In conclusion, our results suggest a novel role of miR-210 in the interaction between PSCs and pancreatic cancer cells.

MicroRNA-21 is induced by rapamycin in a model of tuberous sclerosis (TSC) and lymphangioleiomyomatosis (LAM)

Lymphangioleiomyomatosis (LAM), a multisystem disease of women, is manifest by the proliferation of smooth muscle-like cells in the lung resulting in cystic lung destruction. Women with LAM can also develop renal angiomyolipomas. LAM is caused by mutations in the tuberous sclerosis complex genes (TSC1 or TSC2), resulting in hyperactive mammalian Target of Rapamycin (mTOR) signaling. The mTOR inhibitor, Rapamycin, stabilizes lung function in LAM and decreases the volume of renal angiomyolipomas, but lung function declines and angiomyolipomas regrow when treatment is discontinued, suggesting that factors induced by mTORC1 inhibition may promote the survival of TSC2-deficient cells. Whether microRNA (miRNA, miR) signaling is involved in the response of LAM to mTORC1 inhibition is unknown. We identified Rapamycin-dependent miRNA in LAM patient angiomyolipoma-derived cells using two separate screens. First, we assayed 132 miRNA of known significance to tumor biology. Using a cut-off of >1.5-fold change, 48 microRNA were Rapamycin-induced, while 4 miRs were downregulated. In a second screen encompassing 946 miRNA, 18 miRs were upregulated by Rapamycin, while eight were downregulated. Dysregulation of miRs 29b, 21, 24, 221, 106a and 199a were common to both platforms and were classified as candidate “RapamiRs.” Validation by qRT-PCR confirmed that these microRNA were increased. miR-21, a pro-survival miR, was the most significantly increased by mTOR-inhibition (p<0.01). The regulation of miR-21 by Rapamycin is cell type independent. mTOR inhibition promotes the processing of the miR-21 transcript (pri-miR-21) to a premature form (pre-miR-21). In conclusion, our findings demonstrate that Rapamycin upregulates multiple miRs, including pro-survival miRs, in TSC2-deficient patient-derived cells. The induction of miRs may contribute to the response of LAM and TSC patients to Rapamycin therapy.