miR-199a-3p targets CD44 and reduces proliferation of CD44 positive hepatocellular carcinoma cell lines

MicroRNA-dependent targeting of the extracellular matrix as a mechanism of regulating cell behavior

BACKGROUND

MicroRNAs are small noncoding RNAs which regulate gene expression at the posttranscriptional level by inducing mRNA degradation or translational repression. MicroRNA-dependent modulation of the extracellular matrix and its cellular receptors has emerged as a novel mechanism of regulating numerous matrix-dependent processes, including cell proliferation and apoptosis, cell adhesion and migration, cell differentiation and stem cell properties.

SCOPE OF REVIEW

In this review, we will present different mechanisms by which microRNAs and extracellular matrix constituents mutually regulate their expression, and we will demonstrate how these expression changes affect cell behavior. We will also highlight the importance of dysregulated matrix-related microRNA expression for the pathogenesis of inflammatory and malignant disease, and discuss the potential for diagnostic and therapeutic applications.

MAJOR CONCLUSIONS

MicroRNAs and matrix-dependent signal transduction processes form novel regulatory circuits, which profoundly affect cell behavior. As misexpression of microRNAs targeting extracellular matrix constituents is observed in a variety of diseases, a pharmacological intervention with these processes has therapeutic potential, as successfully demonstrated in vitro and in advanced animal models. However, a deeper mechanistic understanding is required to address potential side effects prior to clinical applications in humans.

GENERAL SIGNIFICANCE

A full understanding of the role and function of microRNA-dependent regulation of the extracellular matrix may lead to new targeted therapies and new diagnostics for malignant and inflammatory diseases in humans. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Role for putative hepatocellular carcinoma stem cell subpopulations in biological response to incomplete thermal ablation: in vitro and in vivo pilot study

PURPOSE

To investigate the potential role for CD44(+) and CD90(+) hepatocellular carcinoma (HCC) cellular subpopulations in biological response to thermal ablation-induced heat stress.

METHODS

This study was approved by the institutional animal care committee. The N1S1 rat HCC cell line was subjected to sublethal heat stress (45 °C) or control (37 °C) for 10 min, costained with fluorescent-labeled antibodies against CD44, CD90, and 7-AAD after a 48-h recovery and analyzed by flow cytometry to assess the percentage of live CD44(+) and CD90(+) HCC cells (n = 4). Experiments were repeated with pretreatment of N1S1 cells with a dose titration of the dual PI3K-mTOR inhibitor BEZ235 or vehicle control (n = 3). Rats bearing orthotopic N1S1 tumors were subjected to ultrasound-guided partial laser ablation (n = 5) or sham ablation (n = 3), euthanized 24 h after ablation, and liver/tumor analyzed for immunohistochemical staining of CD44 and CD90. Differences between groups were compared with an unpaired t test.

RESULTS

Sublethal heat stress induced a significant increase in the relative proportion of live CD44(+) and CD90(+) HCC cells compared to the control group: CD44(+)CD90(-) (5.3-fold; p = 0.0001), CD44(-)CD90(+) (2.4-fold; p = 0.003), and CD44(+)CD90(+) (22.0-fold; p < 0.03). Inhibition of PI3K-mTOR prevented heat stress-induced enrichment of the population of live CD44(+) HCC cells (p < 0.01), but not CD90(+) cells (p > 0.10). Immunohistochemical analysis demonstrated preferential localization of clusters of CD44(+) cells at both the tumor margin and ablation margin.

CONCLUSION

These studies provide experimental evidence supporting a role for HCC cells expressing the putative stem cell marker CD44 in HCC response to heat stress.

Impaired DICER1 function promotes stemness and metastasis in colon cancer

Disruption of microRNA (miRNA) expression patterns is now being recognized as a hallmark of human cancer. The causes of these altered profiles are diverse, and, among them, we found the existence of defects in the miRNA processing machinery. However, little is known about how these alterations affect the biology of the underlying tumors. Herein, we show that colorectal cancer cells with an impairment in DICER1, a major miRNA biogenesis gene, undergo enrichment of tumor stemness features and an epithelial-to-mesenchymal transition. These phenotypes are associated with the downregulation of miRNAs, such as miR-34a, miR-126 and those of the miR-200 family, that target critical coding genes in these pathways. Most importantly, DICER1 impairment also induces the acquisition of a greater capacity for tumor initiation and metastasis, two properties associated with cancer stem cells.

Anti-tumor activity of a miR-199-dependent oncolytic adenovirus

The down-regulation of miR-199 occurs in nearly all primary hepatocellular carcinomas (HCCs) and HCC cell lines in comparison with normal liver. We exploited this miR-199 differential expression to develop a conditionally replication-competent oncolytic adenovirus, Ad-199T, and achieve tumor-specific viral expression and replication. To this aim, we introduced four copies of miR-199 target sites within the 3’ UTR of E1A gene, essential for viral replication. As consequence, E1A expression from Ad-199T virus was tightly regulated both at RNA and protein levels in HCC derived cell lines, and replication controlled by the level of miR-199 expression. Various approaches were used to asses in vivo properties of Ad-199T. Ad-199T replication was inhibited in normal, miR-199 positive, liver parenchyma, thus resulting in reduced hepatotoxicity. Conversely, the intrahepatic delivery of Ad-199T in newborn mice led to virus replication and fast removal of implanted HepG2 liver cancer cells. The ability of Ad-199T to control tumor growth was also shown in a subcutaneous xenograft model in nude mice and in HCCs arising in immune-competent mice. In summary, we developed a novel oncolytic adenovirus, Ad-199T, which could demonstrate a therapeutic potential against liver cancer without causing significant hepatotoxicity.

Role of microRNAs in hepatocellular carcinoma: a clinical perspective

Hepatocellular carcinoma (HCC) is one of the most deadly tumors, and current treatments for the disease are often ineffective. The discovery of the involvement of microRNAs (miRNAs) in hepatocarcinogenesis represents an important area of investigation for the development of their clinical applications. These molecules may act as oncogenes or tumor suppressors by directly or indirectly controlling the expression of key proteins involved in cancer-associated pathways. On the clinical side, because of their tumor-specific expression and stability in tissues and in the circulation, miRNAs have been proposed as novel diagnostic tools for classification and prognostic stratification of HCC. In recent years, the therapeutic potential of miRNAs has been demonstrated in various preclinical studies. Anti-miRNA oligonucleotides and miRNA mimics have been found to have antitumor activity. Moreover, by exploiting tumor-specific expression of miRNA, efforts have been aimed at improving targeting of tumor cells by replicative oncolytic viruses while sparing normal cells. These areas are expected to be explored further in the upcoming years to assess the clinical value of miRNA-based approaches in HCC and cancer in general.

An exploration of heat tolerance in mice utilizing mRNA and microRNA expression analysis

BACKGROUND

Individuals who rapidly develop hyperthermia during heat exposure (heat-intolerant) are vulnerable to heat associated illness and injury. We recently reported that heat intolerant mice exhibit complex alterations in stress proteins in response to heat exposure. In the present study, we further explored the role of genes and molecular networks associated with heat tolerance in mice.

METHODOLOGY

Heat-induced physiological and biochemical changes were assessed to determine heat tolerance levels in mice. We performed RNA and microRNA expression profiling on mouse gastrocnemius muscle tissue samples to determine novel biological pathways associated with heat tolerance.

PRINCIPAL FINDINGS

Mice (n = 18) were assigned to heat-tolerant (TOL) and heat-intolerant (INT) groups based on peak core temperatures during heat exposures. This was followed by biochemical assessments (Hsp40, Hsp72, Hsp90 and Hsf1 protein levels). Microarray analysis identified a total of 3,081 mRNA transcripts that were significantly misregulated in INT compared to TOL mice (p<0.05). Among them, Hspa1a, Dnajb1 and Hspb7 were differentially expressed by more than two-fold under these conditions. Furthermore, we identified 61 distinct microRNA (miRNA) sequences significantly associated with TOL compared to INT mice; eight miRNAs corresponded to target sites in seven genes identified as being associated with heat tolerance pathways (Hspa1a, Dnajb1, Dnajb4, Dnajb6, Hspa2, Hspb3 and Hspb7).

CONCLUSIONS

The combination of mRNA and miRNA data from the skeletal muscle of adult mice following heat stress provides new insights into the pathophysiology of thermoregulatory disturbances of heat intolerance.

Clinical implications of microRNAs in liver cancer stem cells

The prognosis of patients diagnosed with hepatocellular carcinoma (HCC) is often dismal, mainly due to late presentation, high recurrence rate, and frequent resistance to chemotherapy and radiotherapy. Accumulating evidence on the differential microRNA (miRNA) expression patterns between non-tumor and HCC tissues or between liver cancer stem cells (CSCs) and non-CSC subsets and the significant clinical implications of these differences suggest that miRNAs are a promising, non-invasive marker for the prognosis and diagnosis of the disease. This perspective article summarizes the current knowledge of miRNAs in liver CSCs and highlights the need for further investigations of the role of miRNAs in regulating liver CSC subsets for possible future clinical applications.

microRNA-199a-5p protects hepatocytes from bile acid-induced sustained endoplasmic reticulum stress

Sustained endoplasmic reticulum (ER) stress has been linked to cell death and the pathogenesis of many liver diseases, including toxic liver, cholestasis, and infectious liver disease. The cellular pathways that attenuate hepatic ER stress have been the focus of many recent studies, but the role of microRNAs (miRNA) in this process remains unknown. Here, we report that one of the most abundant miRNAs in hepatocytes, miR-199a-5p, was elevated in both bile acid- and thapsigargin (TG)-stimulated cultured hepatocytes, as well as in the liver of bile duct-ligated mice. We identify the misfolded protein chaperone GRP78, as well as the unfolded protein response transducers endoplasmic reticulum to nucleus signaling 1 and activating transcription factor 6 as direct targets of miR-199a-5p, and show that endogenous miR-199a-5p represses the 3′ untranslated regions (UTRs) of their mRNAs. Through gain-of-function and loss of function approaches, we demonstrate that the elevated miR-199-5p disrupts sustained ER stress and prevents hepatocytes from undergoing bile acid- or TG-induced cell death. Furthermore, we reveal that the transcription factor AP-1 is a strong positive regulator of miR-199a-5p. In brief, our study demonstrates that AP-1/miR-199a-5p and ER stress mediators form a feedback loop, which shields hepatocytes from sustained ER stress and protects the liver from injury. On the basis of these findings, we also suggest that the miRNA miR-199a-5p is a potential target for clinical approaches aiming to protect hepatocytes in liver disease.

Reduction of the ST6 β-galactosamide α-2,6-sialyltransferase 1 (ST6GAL1)-catalyzed sialylation of nectin-like molecule 2/cell adhesion molecule 1 and enhancement of ErbB2/ErbB3 signaling by microRNA-199a

Nectin-like molecule 2 (Necl-2)/cell adhesion molecule 1 (CADM1) is shown to be down-regulated by the promoter hypermethylation and/or loss of heterozygosity at chromosome 11q23.2 in many types of cancers, including lung and breast cancers, and is proposed to serve as a tumor suppressor. However, the incidence of these epigenetic and genetic abnormalities of Necl-2 is 30-60% in these cancers, and other mechanisms for the suppression of Necl-2 are presumed to be present. We previously showed that Necl-2 interacts in cis with ErbB3 and suppresses the heregulin (HRG)-induced ErbB2/ErbB3 signaling for cell movement and death. We studied here the relationship between Necl-2 and microRNA-199a (miR-199a) that is up-regulated or down-regulated in a variety of cancers. miR-199a did not directly target the Necl-2 mRNA or affect its mRNA level in human lung cancer A549 cells and human embryonic kidney HEK293 cells. Necl-2 was at least sialylated by the sialyltransferase ST6 β-galactosamide α-2,6-sialyltransferase 1 (ST6GAL1). miR-199a targeted ST6GAL1 and reduced both the sialylation and the protein level of Necl-2. In addition, miR-199a enhanced the HRG-induced ErbB2/ErbB3 signaling. These results indicate that the suppressive role of Necl-2 in the HRG-induced ErbB2/ErbB3 signaling is regulated by miR-199a at least through the reduction of the ST6GAL1-catalyzed sialylation of Necl-2 and/or through the reduction of the protein level of Necl-2 presumably by the protein degradation.

Salinomycin induces cell death and differentiation in head and neck squamous cell carcinoma stem cells despite activation of epithelial-mesenchymal transition and Akt

Background

Cancer stem cells (CSC) are believed to play a crucial role in cancer recurrence due to their resistance to conventional chemotherapy and capacity for self-renewal. Recent studies have reported that salinomycin, a livestock antibiotic, selectively targets breast cancer stem cells 100-fold more effectively than paclitaxel. In our study we sought to determine the effects of salinomycin on head and neck squamous cell carcinoma (HNSCC) stem cells.

Methods

MTS and TUNEL assays were used to study cell proliferation and apoptosis as a function of salinomycin exposure in JLO-1, a putative HNSCC stem cell culture. MTS and trypan blue dye exclusion assays were performed to investigate potential drug interactions between salinomycin and cisplatin or paclitaxel. Stem cell-like phenotype was measured by mRNA expression of stem cell markers, sphere-forming capacity, and matrigel invasion assays. Immunoblotting was also used to determine expression of epithelial-mesenchymal transition (EMT) markers and Akt phosphorylation. Arrays by Illumina, Inc. were used to profile microRNA expression as a function of salinomycin dose.

Results

In putative HNSCC stem cells, salinomycin was found to significantly inhibit cell viability, induce a 71.5% increase in levels of apoptosis, elevate the Bax/Bcl-2 ratio, and work synergistically with cisplatin and paclitaxel in inducing cell death. It was observed that salinomycin significantly inhibited sphere forming-capability and repressed the expression of CD44 and BMI-1 by 3.2-fold and 6.2-fold, respectively. Furthermore, salinomycin reduced invasion of HNSCC stem cells by 2.1 fold. Contrary to expectations, salinomycin induced the expression of EMT markers Snail, vimentin, and Zeb-1, decreased expression of E-cadherin, and also induced phosphorylation of Akt and its downstream targets GSK3-β and mTOR.

Conclusions

These results demonstrate that in HNSCC cancer stem cells, salinomycin can cause cell death and decrease stem cell properties despite activation of both EMT and Akt.

Non-coding RNAs as therapeutic targets in hepatocellular cancer

Hepatocellular carcinoma (HCC) is a common malignancy that affects a large number of patients worldwide, with an increasing incidence in the United States and Europe. The therapies that are currently available for patients with inoperable HCC have limited benefits. Although molecular targeted therapies against selected cell signaling pathways have shown some promising results, their impact has been minimal. There is a need to identify and explore other targets for the development of novel therapeutics. Several non-protein coding RNAs (ncRNA) have recently been implicated in hepatocarcinogenesis and tumor progression. These ncRNA genes represent promising targets for cancer. However, therapeutic targeting of ncRNA genes has not been employed for HCC. The use of antisense oligonucleotides and viral vector delivery approaches have been shown to be feasible approaches to modulate ncRNA expression. HCC is an optimal cancer to evaluate novel RNA based therapeutic approaches because of the potential of effective delivery and uptake of therapeutic agents to the liver. In this review, we discuss selected ncRNA that could function as potential targets in HCC treatment and outline approaches to target ncRNA expression. Future challenges include the need to achieve site-specific targeting with acceptable safety and efficacy.

The role and clinical implications of microRNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is common and one of the most aggressive of all human cancers. Recent studies have indicated that miRNAs, a class of small noncoding RNAs that regulate gene expression post-transcriptionally, directly contribute to HCC by targeting many critical regulatory genes. Several miRNAs are involved in hepatitis B or hepatitis C virus replication and virus-induced changes, whereas others participate in multiple intracellular signaling pathways that modulate apoptosis, cell cycle checkpoints, and growth-factor-stimulated responses. When disturbed, these pathways appear to result in malignant transformation and ultimately HCC development. Recently, miRNAs circulating in the blood have acted as possible early diagnostic markers for HCC. These miRNA also could serve as indicators with respect to drug efficacy and be prognostic in HCC patients. Such biomarkers would assist stratification of HCC patients and help direct personalized therapy. Here, we summarize recent advances regarding the role of miRNAs in HCC development and progression. Our expectation is that these and ongoing studies will contribute to the understanding of the multiple roles of these small noncoding RNAs in liver tumorigenesis.

The expression and functions of microRNAs in pancreatic adenocarcinoma and hepatocellular carcinoma

Pancreatic adenocarcinoma and hepatocellular carcinoma are devastating human malignancies that are characterized by poor prognosis, late onset, and a lack of known biomarkers. New diagnostic and therapeutic molecular targets are desperately needed to develop novel and effective treatment strategies. MicroRNAs (miRNAs) are an emerging class of molecules with roles in various cellular processes, including growth, survival, and apoptosis. Most importantly, aberrant expression of miRNAs has been implicated in cancer pathogenesis. miRNA expression profiles of pancreatic adenocarcinoma and hepatocellular carcinoma indicate selective overexpression of oncogenic miRNAs and down-regulation of tumor suppressive miRNAs in these cancers. This review summarizes results from key studies conducted to characterize the miRNA expression profiles of pancreatic adenocarcinoma and hepatocellular carcinoma and describes the potential mechanisms by which some oncogenic or tumor suppressive miRNAs act. Furthermore, this review outlines novel therapeutic strategies for targeting miRNAs.

Heparin inhibits Hepatocyte Growth Factor induced motility and invasion of hepatocellular carcinoma cells through early growth response protein 1

The Hepatocyte Growth Factor (HGF)/c-Met signaling pathway regulates hepatocyte proliferation, and pathway aberrations are implicated in the invasive and metastatic behaviors of hepatocellular carcinoma (HCC). In addition to c-Met, heparin acts as a co-receptor to modulate pathway activity. Recently, anti-metastatic and anti-cancer effects of heparin have been reported. However, the role of heparin in the regulation of HGF signaling remains controversial and the effects of heparin on HGF-induced biological responses during hepatocarcinogenesis is not yet defined. In this study we determined the effects of heparin on HGF-induced activities of HCC cells and the underlying molecular mechanisms. Here, we report for the first time that heparin inhibits HGF-induced adhesion, motility and invasion of HCC cells. In addition, heparin reduced HGF-induced activation of c-Met and MAPK in a dose-dependent manner, as well as decreased transcriptional activation and expression of Early growth response factor 1 (Egr1). HGF-induced MMP-2 and MMP-9 activation, and MT1-MMP expression, also were inhibited by heparin. Stable knockdown of Egr1 caused a significant decrease in HGF-induced invasion, as well as the activation and expression of MMPs. Parallel to these findings, the overexpression of Egr1 increased the invasiveness of HCC cells. Our results suggest that Egr1 activates HGF-induced cell invasion through the regulation of MMPs in HCC cells and heparin inhibits HGF-induced cellular invasion via the downregulation of Egr1. Therefore, heparin treatment might be a therapeutic approach to inhibit invasion and metastasis of HCC, especially for patients with active HGF/c-Met signaling.

Flexible and versatile as a chameleon-sophisticated functions of microRNA-199a

Although widely studied in the past decade, our knowledge of the functional role of microRNAs (miRNAs) remains limited. Among the many miRNAs identified in humans, we focus on miR-199a due to its varied and important functions in diverse models and systems. Its expression is finely regulated by promoter methylation and direct binding of transcription factors such as TWIST1. During tumorigenesis, depending on the nature of the cancer, miR-199a, especially its -3p mature form, may act as either a potential tumor suppressor or an oncogene. Its 5p mature form has been shown to protect cardiomyocytes from hypoxic damage via its action on HIF1α. It also has a functional role in stem cell differentiation, embryo development, hepatitis, liver fibrosis, etc. Though it has varied biological activities, its regulation has not been reviewed. The varied and protean functions of miR-199a suggest that efforts to generalize the action of a miRNA are problematic. This review provides a comprehensive survey of the literature on miR-199a as an example of the complexity of miRNA biology and suggests future directions for miRNA research.

Distinct microRNA expression profiles in prostate cancer stem/progenitor cells and tumor-suppressive functions of let-7

MiRNAs regulate cancer cells, but their potential effects on cancer stem/progenitor cells are still being explored. In this study, we used quantitative real-time-PCR to define miRNA expression patterns in various stem/progenitor cell populations in prostate cancer, including CD44+, CD133+, integrin α2β1+, and side population cells. We identified distinct and common patterns in these different tumorigenic cell subsets. Multiple tumor-suppressive miRNAs were downregulated coordinately in several prostate cancer stem/progenitor cell populations, namely, miR-34a, let-7b, miR-106a, and miR-141, whereas miR-301 and miR-452 were commonly overexpressed. The let-7 overexpression inhibited prostate cancer cell proliferation and clonal expansion in vitro and tumor regeneration in vivo. In addition, let-7 and miR-34a exerted differential inhibitory effects in prostate cancer cells, with miR-34a inducing G1 phase cell-cycle arrest accompanied by cell senescence and let-7 inducing G2-M phase cell-cycle arrest without senescence. Taken together, our findings define distinct miRNA expression patterns that coordinately regulate the tumorigenicity of prostate cancer cells.

MicroRNAs and hepatitis C virus: toward the end of miR-122 supremacy

The most common etiologic agents causing chronic hepatitis are hepatitis C and B viruses (HCV and HBV, respectively). Chronic infection caused by HCV is considered one of the major causative agents of liver cirrhosis and hepatocellular carcinoma worldwide. In combination with the increasing rate of new HCV infections, the lack of a current vaccine and/or an effective treatment for this virus continues to be a major public health challenge. The development of new treatments requires a better understanding of the virus and its interaction with the different components of the host cell. MicroRNAs (miRNAs) are small non-coding RNAs functioning as negative regulators of gene expression and represent an interesting lead to study HCV infection and to identify new therapeutic targets. Until now, microRNA-122 (miR-122) and its implication in HCV infection have been the focus of different published studies and reviews. Here we will review recent advances in the relationship between HCV infection and miRNAs, showing that some of them emerge in publications as challengers against the supremacy of miR-122.

Suppression of human breast tumors in NOD/SCID mice by CD44 shRNA gene therapy combined with doxorubicin treatment

Background

Breast cancer stem cells with a CD44⁺CD24⁻ phenotype are the origin of breast tumors. Strong CD44 expression in this population indicates its important role in maintaining the stem cell phenotype. Previous studies show that CD44 down-regulation causes CD44⁺CD24⁻ breast cancer stem cells to differentiate into non-stem cells that are sensitive to antitumor drugs and lose many characteristics of the original cells. In this study, we determined tumor suppression in non-obese severe combined immunodeficiency mice using CD44 shRNA therapy combined with doxorubicin treatment.

Methods

Tumor-bearing non-obese severe combined immunodeficiency mice were established by injection of CD44⁺CD24⁻ cells. To track CD44⁺CD24⁻ cells, green fluorescence protein was stably transduced using a lentiviral vector prior to injection into mice. The amount of CD44 shRNA lentiviral vector used for transduction was based on CD44 down-regulation by in vitro CD44 shRNA transduction. Mice were treated with direct injection of CD44 shRNA lentiviral vector into tumors followed by doxorubicin administration after 48 hours. The effect was evaluated by changes in the size and weight of tumors compared with that of the control.

Results

The combination of CD44 down-regulation and doxorubicin strongly suppressed tumor growth with significant differences in tumor sizes and weights compared with that of CD44 down-regulation or doxorubicin treatment alone. In the combination of CD44 down-regulation and doxorubicin group, the tumor weight was significantly decreased by 4.38-fold compared with that of the control group.

Conclusion

These results support a new strategy for breast cancer treatment by combining gene therapy with chemotherapy.

MicroRNA-199a targets CD44 to suppress the tumorigenicity and multidrug resistance of ovarian cancer-initiating cells

In ovarian cancer, CD44(+) /CD117(+) stem cells, also known as cancer-initiating cells (CICs), are highly proliferative, have a low degree of differentiation, and are resistant to chemotherapeutics. Therefore, the CD44(+) /CD117(+) subpopulation is thought to be an important target for novel therapeutic strategies. In this study, we investigated the role of microRNA-199a (miR-199a) in ovarian cancer stem cells. Luciferase reporter gene assays confirmed that miR-199a targets CD44 via an miR-199a-binding site in the 3'-UTR. CD44(+) /CD117(+) ovarian CICs were enriched from human primary ovarian tumor tissues and confirmed by flow cytometric sorting. miR-199a was cloned and transfected into ovarian CICs. CD44 mRNA and protein expression was significantly decreased in miR-199a-transfected ovarian CICs as compared with miR-199a mutant-transfected and untransfected cells. Cell cycle analysis, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide proliferation assays, the colony formation assay and the transwell migration assay indicated that miR-199a significantly affected cell cycle regulation and suppressed the proliferation and invasive capacity of ovarian CICs in vitro. miR-199a significantly increased the chemosensitivity of ovarian CICs to cisplatin, pacitaxel, and adriamycin, and reduced mRNA expression of the multidrug resistance gene ABCG2 as compared with miR-199a mutant-transfected and untransfected cells. The expression of stemness markers was also significantly reduced in miR-199a-transfected CICs as compared with miR-199a mutant-transfected and untransfected ovarian cells. Furthermore, xenograft experiments confirmed that miR-199a suppressed the growth of xenograft tumors formed by ovarian CICs in vivo. Thus, expression of endogenous mature miR-199a may prevent tumorigenesis in human ovarian cancer by regulating expression of its target gene CD44.

Non-coding RNAs in hepatitis B or C-associated hepatocellular carcinoma: potential diagnostic and prognostic markers and therapeutic targets

Non-coding RNA (ncRNA), a class of RNAs that do not code protein but have regulatory functions, can regulate gene expression and replication of hepatitis B virus or hepatitis C virus and play an important role in the virus-host interaction and the development of hepatocellular carcinoma (HCC). Deregulated ncRNAs in surgically removed hepatic tissues and circulation can be prognostic and diagnostic markers, respectively. ncRNAs functioning as either tumor suppressors or oncogenes can be therapeutic options. Here, we summarize the deregulated ncRNAs associated with the infections and HCC and focus on their roles on early diagnosis, prognosis prediction and therapeutic option of HCC.

miR-125b suppresses the proliferation and migration of osteosarcoma cells through down-regulation of STAT3

There is accumulating evidence that microRNAs are involved in multiple processes in development and tumor progression. Abnormally expressed miR-125b was found to play a fundamental role in several types of cancer; however, whether miR-125b participates in regulating the initiation and progress of osteosarcoma still remains unclear. Here we demonstrate that miR-125b is frequently down-regulated in osteosarcoma samples and human osteosarcoma cell lines. The ectopic restoration of miR-125b expression in human osteosarcoma cells suppresses proliferation and migration in vitro and inhibits tumor formation in vivo. We further identified signal transducer and activator of transcription 3 (STAT3) as the direct and functional downstream target of miR-125b. Interestingly, we discovered that the expression of miR-125b is regulated by STAT3 at the level of transcription. STAT3 binds to the promoter region of miR-125b in vitro and serves as a transactivator. Taken together, our findings point to an important role in the molecular etiology of osteosarcoma and suggest that miR-125b is a potential target in the treatment of osteosarcoma.

Cancer stem cell theory in gastrointestinal malignancies: recent progress and upcoming challenges

A growing body of evidence supports the notion that malignant tumors are heterogeneous and contain diverse subpopulations of cells with unique characteristics including the ability to initiate a tumor and metastasize. This phenomenon might be explained by the so-called cancer stem cell (CSC) theory. Recent technological developments have allowed a deeper understanding and characterization of CSCs. Even though the application of this theory to hematopoietic malignancies and solid tumors holds promise for new ways to treat cancer, it also brings some skepticism. Efficacious therapeutic approaches targeting the CSC population should be explored to overcome therapeutic failure and improve patient outcomes. This review will focus on the intrinsic and extrinsic regulation of CSCs, as well as the development of therapeutic approaches against CSCs, predominantly focusing on gastrointestinal malignancies.

The critical role of CD133(+)CD44(+/high) tumor cells in hematogenous metastasis of liver cancers

Metastatic hepatocellular carcinoma (HCC) is one of the most lethal cancers worldwide. However, the cell population responsible for its metastasis remains largely unknown. Here, we reported that CD133(+)CD44(+/high) defined a subgroup of tumor cells that was responsible for hematogenous metastasis of liver cancers. Immunohistochemical investigation of human HCC specimens revealed that the number of CD133(+) and CD44(+) HCC cells was increased and was associated with portal vein invasion. Purified CD133(+) or CD44(high) HCC cells were superior in clonogenic growth and vascular invasion, respectively. Thus, the combination of CD133 and CD44 was used to define a novel HCC sub-population. CD133(+)CD44(high), but not CD133(+)CD44(low/-), CD133(-)CD44(high) or CD133(-)CD44(low/-) xenografts, produced intrahepatic or lung metastasis in nude mice. Further analysis of human HCC samples by flow cytometry showed that the number of CD133(+)CD44(+) tumor cells was associated with portal vein metastasis. The cDNA microarray analysis of CD133(+)CD44(+) and CD133(+)CD44(-) tumor cells isolated from metastatic HCC patients revealed that these cells comprised of two different populations possessing distinct gene expression profiles. Our results suggest that CD133(+)CD44(+) tumor cells are a particular population responsible for hematogenous metastasis in liver cancers and that these cells might be targets for treatment of HCC metastasis.

Role of early growth response 1 in liver injury

Liver injury is a sophisticated pathophysiological process caused by many factors. Currently, the role of early growth response 1 (EGR1) in liver injury is still controversial. Some studies show that EGR1 can amplify the systemic inflammatory response and promote apoptosis in galactosamine/lipopolysaccharide-induced acute liver injury and alpha-naphthylisothiocyanate (ANIT)-induced intrahepatic cholestasis as well as other non-liver injuries, while some other studies indicate that EGR1 protects the liver from CCl₄ exposure by regulating the expression of inducible nitric oxide synthase, cyclooxygenase-2, and tumor necrosis factor-α-regulated genes that have hepatoprotective function.

Downregulation of CD44 reduces doxorubicin resistance of CD44CD24 breast cancer cells

BACKGROUND

Cells within breast cancer stem cell populations have been confirmed to have a CD44(+)CD24(-) phenotype. Strong expression of CD44 plays a critical role in numerous types of human cancers. CD44 is involved in cell differentiation, adhesion, and metastasis of cancer cells.

METHODS

In this study, we reduced CD44 expression in CD44(+)CD24(-) breast cancer stem cells and investigated their sensitivity to an antitumor drug. The CD44(+)CD24(-) breast cancer stem cells were isolated from breast tumors; CD44 expression was downregulated with siRNAs followed by treatment with different concentrations of the antitumor drug.

RESULTS

The proliferation of CD44 downregulated CD44(+)CD24(-) breast cancer stem cells was decreased after drug treatment. We noticed treated cells were more sensitive to doxorubicin, even at low doses, compared with the control groups.

CONCLUSIONS

It would appear that expression of CD44 is integral among the CD44(+)CD24(-) cell population. Reducing the expression level of CD44, combined with doxorubicin treatment, yields promising results for eradicating breast cancer stem cells in vitro. This study opens a new direction in treating breast cancer through gene therapy in conjunction with chemotherapy.