MicroRNA regulation of cancer stem cells and therapeutic implications

The Multifaceted Roles of MicroRNA-181 in Stem Cell Differentiation and Cancer Stem Cell Plasticity

Stem cells are undifferentiated or partially differentiated cells with an extraordinary ability to self-renew and differentiate into various cell types during growth and development. The epithelial-mesenchymal transition (EMT), a critical developmental process, enhances stem cell-like properties in cells, and is associated with both normal stem cell function and the formation of cancer stem cells. Cell stemness and the EMT often coexist and are interconnected in various contexts. Cancer stem cells are a critical tumor cell population that drives tumorigenesis, cancer progression, drug resistance, and metastasis. Stem cell differentiation and the generation of cancer stem cells are regulated by numerous molecules, including microRNAs (miRNAs). These miRNAs, particularly through the modulation of EMT-associated factors, play major roles in controlling the stemness of cancer stem cells. This review presents an up-to-date summary of the regulatory roles of miR-181 in human stem cell differentiation and cancer cell stemness. We outline studies from the current literature and summarize the miR-181-controlled signaling pathways responsible for driving human stem cell differentiation or the emergence of cancer stem cells. Given its critical role in regulating cell stemness, miR-181 is a promising target for influencing human cell fate. Modulation of miR-181 expression has been found to be altered in cancer stem cells' biological behaviors and to significantly improve cancer treatment outcomes. Additionally, we discuss challenges in miRNA-based therapies and targeted delivery with nanotechnology-based systems.

miR-3191 promotes the proliferation and metastasis of hepatocellular carcinoma via regulating PAK6

BACKGROUND/AIMS

microRNAs (miRNAs) contribute to tumorigenesis, progression and drug resistance of hepatocellular carcinoma (HCC). miR-3191 is a newly discovered miRNA, and its function and mechanism of action in biological processes and diseases are not completely understood.

METHODS

miR-3191 expression is determined via quantitative real-time polymerase chain reaction. Knockdown and overexpression of miR-3191 influence the proliferation and metastasis of HCC cells, which is measured by Cell Counting Kit-8 assay, Colony Formation assay and Cell metastasis assay. Protein expression is estimated by Western blot. The interplay between miR-3191 and target is validated by dual-luciferase reporter assay.

RESULTS

Here, we show that miR-3191 is upregulated in HCC tissues and associated with poor prognosis of HCC patients. Mechanistically, p21-activated protein kinase 6 (PAK6) was identified as a direct target of miR‑3191 in HCC. PAK6 knockdown partially recovered interference of miR‑3191‑induced decrease in cell proliferation and invasion. The accuracy of HCC patient prognosis could be improved by employing a combination of miR-3191 and PAK6 values.

CONCLUSIONS

miR-3191 promotes the proliferation and metastasis of HCC cells via targeting PAK6 and may serve as a prognostic biomarker and potential therapeutic target.

MicroRNA-206 as a promising epigenetic approach to modulate tumor-associated macrophages in hepatocellular carcinoma

This letter comments on the recently published manuscript by Huang et al in the World Journal of Gastroenterology, which focused on the immunomodulatory effect of Calculus bovis on hepatocellular carcinoma (HCC) tumor microenvironments (TME) by inhibiting M2-tumor-associated macrophage (M2-TAM) polarization via Wnt/β-catenin pathway modulation. Recent research highlights the crucial role of TAMs and their polarization towards the M2 phenotype in promoting HCC progression. Epigenetic regulation, particularly through microRNAs (miR), has emerged as a key factor in modulating immune responses and TAM polarization in the TME, influencing treatment responses and tumor progression. This editorial focuses on miR-206, which has been found to inhibit HCC cell proliferation and migration and promote apoptosis. Moreover, miR-206 enhances anti-tumor immune responses by promoting M1-polarization of Kupffer cells, facilitating CD8+ T cell recruitment and suppressing liver cancer stem cell expansion. However, challenges remain in understanding the precise mechanisms regulating miR-206 and its potential as a therapeutic agent. Targeting epigenetic mechanisms and improving strategies, whether through pharmacological or genetic approaches, offer promising avenues to sensitize tumor cells to chemotherapy. Understanding the intricate interactions between cancer and non-coding RNA regulation opens new avenues for developing targeted therapies, potentially improving HCC prognosis.

MHESMMR: a multilevel model for predicting the regulation of miRNAs expression by small molecules

According to the expression of miRNA in pathological processes, miRNAs can be divided into oncogenes or tumor suppressors. Prediction of the regulation relations between miRNAs and small molecules (SMs) becomes a vital goal for miRNA-target therapy. But traditional biological approaches are laborious and expensive. Thus, there is an urgent need to develop a computational model. In this study, we proposed a computational model to predict whether the regulatory relationship between miRNAs and SMs is up-regulated or down-regulated. Specifically, we first use the Large-scale Information Network Embedding (LINE) algorithm to construct the node features from the self-similarity networks, then use the General Attributed Multiplex Heterogeneous Network Embedding (GATNE) algorithm to extract the topological information from the attribute network, and finally utilize the Light Gradient Boosting Machine (LightGBM) algorithm to predict the regulatory relationship between miRNAs and SMs. In the fivefold cross-validation experiment, the average accuracies of the proposed model on the SM2miR dataset reached 79.59% and 80.37% for up-regulation pairs and down-regulation pairs, respectively. In addition, we compared our model with another published model. Moreover, in the case study for 5-FU, 7 of 10 candidate miRNAs are confirmed by related literature. Therefore, we believe that our model can promote the research of miRNA-targeted therapy.

Cancer Stem Cells and Treatment of Cancer: An Update and Future Perspectives

Cancer stem cells (CSCs) play an essential role in tumour progression and metastasis. Stem cell ability of self-renewal enables it to persist over time, thereby contributing to cancer relapse or recurrence and also resistance to current therapies. Therefore, targeting CSCs emerged as a promising strategy of cancer treatment. CSCs exhibit differentiation, self-renewal, and plasticity, they contribute to formation of malignant tumours, also favors, metastasis, heterogeneity, multidrug resistance, and radiation resistance. Coventional cancer treatments predominantly target cancer cells that are not CSCs, CSCs frequently survive, eventually leading to relapse. This article focuses on the development of novel therapeutic strategies that combine conventional treatments and CSC inhibitors to eradicate cancer cells and CSCs, for the better and permanent treatment. However, the diversity of CSCs is a significant obstacle in the development of CSC-targeted therapies, necessitating extensive research for a better understanding and exploration of therapeutic approaches. Future development of CSC-targeted therapies will rely heavily on overcoming this obstacle.

Cytotoxicity of curcumin against CD44± prostate cancer cells: Roles of miR-383 and miR-708

Objective

Cancer stem cells (CSCs) remaining in the tumor tissues after applying treatments may cause recurrence or metastasis of prostate cancer (PC). Curcumin has the promising potential to target CSCs. Here, we aim to evaluate the cytotoxic effects of curcumin on the expression of miR-383-5p and miR-708-5p and their target genes in CD44+ CSCs and CD44- non-CSCs isolated from the PC3 prostate cancer cell line.

Materials and Methods

We used MTT assay to determine the optimal cytotoxic dose of curcumin on CD44± PC cells. Then, we assessed nuclear morphological changes using DAPi staining. We used Annexin V-FITC/PI to quantify apoptotic cell death. qRT-PCR was also used to detect miRNA and gene expression levels after curcumin treatment.

Results

Curcumin significantly enhanced the apoptosis in both CD44- and CD44+ PC cells in a dose-dependent manner (p < 0.05). The cytotoxicity of curcumin against CD44- cells (IC50 40.30±2.32 μM) was found to be greater than that against CD44+ cells (IC50 83.31±2.91 μM). Also, curcumin promoted miR-383-5p and miR-708-5p overexpression while downregulating their target genes LDHA, PRDX3, and RAP1B, LSD1, respectively.

Conclusion

Our findings indicate that curcumin, by promoting the expression of tumor suppressors, miR-383-5p and miR-708-5p, and inhibiting their target genes, induced its cytotoxicity against CD44± PC cells. We trust that curcumin could be established as a promising adjuvant therapy to current PC treatment options following more research in clinical settings.

Osteogenic and Adipogenic Differentiation Potential of Oral Cancer Stem Cells May Offer New Treatment Modalities

(1) Treatment failure of oral squamous cell carcinoma (OSCC) is generally due to the development of therapeutic resistance caused by the existence of cancer stem cells (CSCs), a small cell subpopulation with marked self-renewal and differentiation capacity. Micro RNAs, notably miRNA-21, appear to play an important role in OSCC carcinogenesis. Our objectives were to explore the multipotency of oral CSCs by estimating their differentiation capacity and assessing the effects of differentiation on stemness, apoptosis, and several miRNAs' expression. (2) A commercially available OSCC cell line (SCC25) and five primary OSCC cultures generated from tumor tissues obtained from five OSCC patients were used in the experiments. Cells harboring CD44, a CSC marker, were magnetically separated from the heterogeneous tumor cell populations. The CD44⁺ cells were then subjected to osteogenic and adipogenic induction, and the specific staining was used for differentiation confirmation. The kinetics of the differentiation process was evaluated by qPCR analysis of osteogenic (Bone Morphogenetic Protein-BMP4, Runt-related Transcription Factor 2-RUNX2, Alkaline Phosphatase-ALP) and adipogenic (Fibroblast Activation Protein Alpha-FAP, LIPIN, Peroxisome Proliferator-activated Receptor Gamma-PPARG) markers on days 0, 7, 14, and 21. Embryonic markers (Octamer-binding Transcription Factor 4-OCT4, Sex Determining Region Y Box 2-SOX2, and NANOG) and micro RNAs (miRNA-21, miRNA-133, and miRNA-491) were also correspondingly evaluated by qPCR. An Annexin V assay was used to assess the potential cytotoxic effects of the differentiation process. (3) Following differentiation, the levels of markers for the osteo/adipo lineages showed a gradual increase from day 0 to day 21 in the CD44⁺ cultures, while stemness markers and cell viability decreased. The oncogenic miRNA-21 also followed the same pattern of gradual decrease along the differentiation process, while tumor suppressor miRNA-133 and miRNA-491 levels increased. (4) Following induction, the CSCs acquired the characteristics of the differentiated cells. This was accompanied by loss of stemness properties, a decrease of the oncogenic and concomitant, and an increase of tumor suppressor micro RNAs.

Epigenetic Inheritance From Normal Origin Cells Can Determine the Aggressive Biology of Tumor-Initiating Cells and Tumor Heterogeneity

The acquisition of genetic- and epigenetic-abnormalities during transformation has been recognized as the two fundamental factors that lead to tumorigenesis and determine the aggressive biology of tumor cells. However, there is a regularity that tumors derived from less-differentiated normal origin cells (NOCs) usually have a higher risk of vascular involvement, lymphatic and distant metastasis, which can be observed in both lymphohematopoietic malignancies and somatic cancers. Obviously, the hypothesis of genetic- and epigenetic-abnormalities is not sufficient to explain how the linear relationship between the cellular origin and the biological behavior of tumors is formed, because the cell origin of tumor is an independent factor related to tumor biology. In a given system, tumors can originate from multiple cell types, and tumor-initiating cells (TICs) can be mapped to different differentiation hierarchies of normal stem cells, suggesting that the heterogeneity of the origin of TICs is not completely chaotic. TIC’s epigenome includes not only genetic- and epigenetic-abnormalities, but also established epigenetic status of genes inherited from NOCs. In reviewing previous studies, we found much evidence supporting that the status of many tumor-related “epigenetic abnormalities” in TICs is consistent with that of the corresponding NOC of the same differentiation hierarchy, suggesting that they may not be true epigenetic abnormalities. So, we speculate that the established statuses of genes that control NOC’s migration, adhesion and colonization capabilities, cell-cycle quiescence, expression of drug transporters, induction of mesenchymal formation, overexpression of telomerase, and preference for glycolysis can be inherited to TICs through epigenetic memory and be manifested as their aggressive biology. TICs of different origins can maintain different degrees of innate stemness from NOC, which may explain why malignancies with stem cell phenotypes are usually more aggressive.

Autophagy inhibits cancer stemness in triple-negative breast cancer via miR-181a-mediated regulation of ATG5 and/or ATG2B

Autophagy has a dual role in the maintenance of cancer stem cells (CSCs), but the precise relationship between autophagy and cancer stemness requires further investigation. In this study, it was found that luminal and triple‐negative breast cancers require distinct therapeutic approaches because of their different amounts of autophagy flux. We identified that autophagy flux was inhibited in triple‐negative breast cancer (TNBC) CSCs. Moreover, miRNA‐181a (miR‐181a) expression is upregulated in both TNBC CSCs and patient tissues. Autophagy‐related 5 (ATG5) and autophagy‐related 2B (ATG2B) participate in the early formation of autophagosomes and were revealed as targets of miR‐181a. Inhibition of miR‐181a expression led to attenuation of TNBC stemness and an increase in autophagy flux. Furthermore, treatment with curcumin led to attenuation of cancer stemness in TNBC CSCs; the expression of ATG5 and ATG2B was enhanced and there was an increase of autophagy flux. These results indicated that ATG5 and ATG2B are involved in the suppression of cancer stemness in TNBC. In summary, autophagy inhibits cancer stemness through the miR‐181a‐regulated mechanism in TNBC. Promoting tumor‐suppressive autophagy using curcumin may be a potential method for the treatment of TNBC.

MiR-552-3p facilitated cell proliferation, migration and invasion by sponging Fibulin 5 in non-small cell lung cancer via activation of ERK/GSK3β/β-catenin signaling pathway

Apart from the fact that miR-552-3p is known to promote cell progression among various cancers, its function on non-small cell lung cancer (NSCLC) is unknown which therefore emerges as the purpose of this research. TargetScan, Starbase, miRWalk, miRDB and the Cancer Genome Atlas Lung Adenocarcinoma (TCGA-LUAD) were utilized to analyze the target genes of miR-552-3p. NSCLC cells were transfected with miR-552-3p mimic, miR-552-3p inhibitor, Fibulin 5 (FBLN5) overexpression plasmid, and small interfering FBLN5 (siFBLN5) and treated with extracellular regulated protein kinases (ERK) pathway inhibitor PD98059. MiR-552-3p, FBLN5, p-ERK, ERK, p-glycogen synthase kinase 3β (GSK3β) and β-catenin levels were detected through quantitative reverse transcription-polymerase chain reaction and western blot. The binding sites between miR-552-3p and FBLN5 were predicted by TargetScan, which was tested through dual luciferase reporter analysis. Cell viability, migration and invasion were determined by cell counting kit-8 (CCK-8) assay, wound healing assay and transwell assay, respectively. MiR-552-3p expression was upregulated in NSCLC and FBLN5 functioned as its target. MiR-552-3p mimic promoted proliferation, migration, invasion, p-ERK, p-GSK3β and β-catenin expressions in NSCLC cells while miR-552-3p inhibitor did the opposite. Overexpressed FBLN5 suppressed proliferation, migration, invasion, p-ERK, p-GSK3β and β-catenin expressions in NSCLC cells whereas siFBLN5 exerted the effects opposite to overexpressed FBLN5. PD98059 enhanced the effect of overexpressed FBLN5 on NSCLC cell migration and invasion while reversing the effect of siFBLN5. MiR-552-3p facilitated cell proliferation, migration and invasion in NSCLC through sponging FBLN5 via activation of ERK/GSK3β/β-catenin pathway.

Re-Recognizing the Cellular Origin of the Primary Epithelial Tumors of the Liver

The primary epithelial tumors of the liver (PETL) are composed of a series of heterogeneous tumors. Although the classification of PETLs has been updated several times by the World Health Organization, the cellular origins of some tumors in this family remain to be precisely depicted. In addition, certain tumors in different categories have similar histology, molecular phenotypes and biological characteristics, suggesting that they may have the same cellular origin. In this work, a narrative review method was adopted to review the relevant papers. By comparing the expression profiles of biomarkers of liver epithelium at different lineages and stages of differentiation, the cells-of-origin of some major members of the PETL family were reassessed. We propose that 1) hepatic adenomas, hepatocellular carcinomas (HCCs) and pure fetal hepatoblastomas (HBs) share the same spectrum in their cellular origin including the hepatocytic-committed progenitors (HCP) and their differentiated descendants. 2) Bile duct adenomas, peribiliary cysts and intrahepatic cholangiocellular carcinomas (ICCs) can share the same spectrum in their cellular origin including the cholangiocytic-committed progenitors (CCP) and their differentiated descendants. 3) The cells-of-origin of embryonal HBs include liver stem cells (LSCs), hepatoblasts, and transitional cells between them. Embryonal HB with small cell element, small cell undifferentiated HB and small cell neuroendocrine carcinoma of the liver can have the same or similar cells-of-origin from LSC. Embryonal HB lacking the small cell component of the LSC phenotype and presenting both hepatocytic and bile duct/ductule components may originate from actual hepatoblasts/hepatic progenitor cells (HPCs) as the combined HCC-ICC does. 4) Teratoid hepatoblastoma and mixed epithelial/mesenchymal HBs can be derived from the LSCs or even less committed extrahepatic pluripotent stem cell. 5) Many members of the PETLs family, including those derived from LSCs, hepatoblasts/HPCs, early HCPs and CCPs, have neuroendocrine potentiality. Except for those primary hepatic neuroendocrine tumor (PHNET) exhibit hepatocytic and/or cholangiocytic phenotypes, other PHNETs subtype may be derived from the descendants of LSC that differentiate towards the upper digestive tract, pancreas or other lineages.

Potential Biomarkers of miR-371-373 Gene Cluster in Tumorigenesis

microRNAs (miRNAs) are small non-coding RNA transcripts (20–24 nucleotides) that bind to their complementary sequences in the 3′-untranslated regions (3′-UTR) of targeted genes to negatively or positively regulate their expression. miRNAs affect the expression of genes in cells, thereby contributing to several important biological processes, including tumorigenesis. Identifying the miRNA cluster as a human embryonic stem cell (hESC)-specific miRNAs initially led to the identification of miR-371, miR-372, miR-373, and miR-373*, which can ultimately be translated into mature miRNAs. Recent evidence suggests that miR-371–373 genes are abnormally expressed in various cancers and act either as oncogenes or tumor suppressors, indicating they may be suitable as molecular biomarkers for cancer diagnosis and prevention. In this article, we summarize recent studies linking miR-371–373 functions to tumorigenesis and speculate on the potential applications of miR-371–373 as biomarkers for cancer diagnosis and treatment.

Ketogenic Diet in Cancer Prevention and Therapy: Molecular Targets and Therapeutic Opportunities

Although cancer is still one of the most significant global challenges facing public health, the world still lacks complementary approaches that would significantly enhance the efficacy of standard anticancer therapies. One of the essential strategies during cancer treatment is following a healthy diet program. The ketogenic diet (KD) has recently emerged as a metabolic therapy in cancer treatment, targeting cancer cell metabolism rather than a conventional dietary approach. The ketogenic diet (KD), a high-fat and very-low-carbohydrate with adequate amounts of protein, has shown antitumor effects by reducing energy supplies to cells. This low energy supply inhibits tumor growth, explaining the ketogenic diet's therapeutic mechanisms in cancer treatment. This review highlights the crucial mechanisms that explain the ketogenic diet's potential antitumor effects, which probably produces an unfavorable metabolic environment for cancer cells and can be used as a promising adjuvant in cancer therapy. Studies discussed in this review provide a solid background for researchers and physicians to design new combination therapies based on KD and conventional therapies.

MiR-146b-3p regulates proliferation of pancreatic cancer cells with stem cell-like properties by targeting MAP3K10

Purpose: Cancer stem cells (CSCs) initiate and maintain tumorigenesis due to their unique pluripotency. However, pancreatic stem cell gene signatures are not completely revealed yet. Here, we isolated pancreatic cancer stem cells (P-CSCs) and exploited their distinct genome-wide mRNA and miRNA expression profiles using microarrays.

Methods: CD24⁺ CD44⁺ ESA⁺ cells were isolated from two pancreatic xenograft cells by the flow cytometry and identified the stem cell-like properties by the tumor formation, self-renew and chemoresistance. Microarrays and qRT-PCR were used to exploit their distinct Genome-wide mRNA and miRNA expression profiles. The function and candidate target genes of key microRNA were detected after Ectopic restoration in the pancreatic cancer cell lines MIA Paca-2 (CSC^high) and BxPC-3 (CSC^low).

Results: In this study, we isolated P-CSCs from two xenografts cells. Genome-wide profiling experiments showed 479 genes and 15 microRNAs specifically expressed in the P-CSCs, including genes involved in TGF-β and p53 signaling pathways and particularly miR-146b-3p as the most significantly downregulated miRNA. We confirmed miR-146b-3p as a downregulated signature in pancreatic cancer tissues and cell line MIA Paca-2 (CSC^high) cells. Ectopic restoration of miR-146b-3p expression with pre-miR reduced cell proliferation, induced apoptosis, increased G1 phase and reduced S phase in cell cycle in MIA Paca-2 (CSC^high), but not in BxPC-3 (CSC^low). Re-expression of miR-146b-3p with lentivirus significantly inhibited tumorigenicity in vivo in MIA Paca-2, but slightly in BxPC-3. Furthermore, we demonstrated that miR-146b-3p directly targeted MAP3K10 and might activate Hedgehog pathway as well through DYRK2 and GLI2.

Conclusions: These results suggest that P-CSCs have distinct gene expression profiles. MiR-146b-3p inhibits proliferation and induced apoptosis in P-CSCs high cells lines by targeting MAP3K10. Targeting P-CSCs specific genes may provide novel strategies for therapeutic purposes.

miR-93 regulates liver tumor initiating cells expansion and predicts chemotherapeutic response of patients

Tumor initiating cells (T-ICs) play an important role in tumorigenesis, progression, metastasis, recurrence and drug resistance, but the underlying mechanism was not clearly elucidated. In our study, we found that miR-93 was highly expressed in liver T-ICs. Self-renewal and tumorigenesis ability of liver T-ICs were enhanced by miR-93 overexpression and attenuated by miR-93 interference. Mechanically, miR-93 regulated liver T-ICs by binding to 3'-UTR of myotubularin-related protein 3 (MTMR3). In addition, miR-93 was found highly expressed in cisplatin or sorafenib-resistant liver cancer tissues. Interference of miR-93 sensitizes hepatoma cells to cisplatin or sorafenib treatment. Clinical cohort analysis showed that Hepatocellular carcinoma (HCC) patients with low miR-93 were benefit more from TACE or sorafenib treatment. In conclusion, our study demonstrates a new regulation mechanism of liver T-ICs, a new target for HCC, and a biomarker for postoperative TACE or sorafenib.

A Peptide-Based Small RNA Delivery System to Suppress Tumor Growth by Remodeling the Tumor Microenvironment

MicroRNAs can regulate a variety of physiological and pathological processes and are increasingly recognized as being involved in regulating the malignant progression of cancer, which is an important direction for the study and treatment of cancer. In addition, the tumor microenvironment has gradually become an important direction of study for combating cancer. Researchers can inhibit tumor growth by remodeling and suppressing an immunosuppressive phenotype in the tumor microenvironment. Therefore, the combination of microRNA delivery and tumor microenvironment remodeling may be a potential research direction. In a previous study, we developed a novel cationic and hydrophilic antimicrobial peptide, DP7, by computer simulation. It was found that cholesterol-modified DP7 (DP7-C) has dual functions as a carrier and an immune adjuvant. In this experiment, we used DP7-C to deliver microRNAs or inhibitors intratumorally, where it played a dual role as a carrier and an immune adjuvant. As a delivery vector, DP7-C has more advantages in terms of transfection efficiency and cytotoxicity than Lipo2000 and PEI25K. Components of the DP7-C/RNA complex can effectively escape endosomes after uptake via caveolin- and clathrin-dependent pathways. As an immune adjuvant, DP7-C can activate dendritic cells and promote macrophage polarization. Moreover, it can transform the immunosuppressive tumor microenvironment into an immune-activated tumor microenvironment, indicating its potential as an anticancer therapy. In conclusion, this study identifies a novel microRNA and inhibitor delivery system that can remodel the tumor microenvironment and introduces an alternative scheme for antitumor treatment.

miR-365 inhibits the progression of gallbladder carcinoma and predicts the prognosis of Gallbladder carcinoma patients

Gallbladder carcinoma (GBC) is one of the most common fatal biliary tract tumors in the world. Its 3-year survival rate is 30% and the recurrence rate remains very high. miR-365 was downregulated in numerous tumors and worked as tumor suppressor gene. However, the role of miR-365 in GBC was unclear. In this study, our results found that the expression of miR-365 in GBC tissues was reduced rather than that in non-cancerous tissues. miR-365 overexpression inhibited the proliferation, metastasis and expansion of GBC CSCs. Mechanically, bioinformatic and luciferase reporter analysis identified Ras-related C3 botulinum toxin substrate 1 (RAC1) as a direct target of miR-365. Overexpression of miR-365 in GBC cells reduced the RAC1 mRNA and protein expression. The special RAC1 inhibitor EHop-106 abolished the discrepancy of growth, metastasis and self-renewal ability between miR-365-overexpression GBC cells and their control cells, which further demonstrated that RAC1 was involved in miR-365-disrupted GBC cells growth, metastasis and self-renewal. More importantly, reduced expression of miR-365 was a predictor of poor prognosis of GBC patients. In conclusion, miR-365 inhibited GBC cell growth, metastasis and self-renewal capacity by directly targeting RAC1, and may therefore prove to be a novel prognosis biomarker for GBC patients.

Recent Advances in Liver Cancer Stem Cells: Non-coding RNAs, Oncogenes and Oncoproteins

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies worldwide, with high morbidity, relapse, metastasis and mortality rates. Although liver surgical resection, transplantation, chemotherapy, radiotherapy and some molecular targeted therapeutics may prolong the survival of HCC patients to a certain degree, the curative effect is still poor, primarily because of tumor recurrence and the drug resistance of HCC cells. Liver cancer stem cells (LCSCs), also known as liver tumor-initiating cells, represent one small subset of cancer cells that are responsible for disease recurrence, drug resistance and death. Therefore, understanding the regulatory mechanism of LCSCs in HCC is of vital importance. Thus, new studies that present gene regulation strategies to control LCSC differentiation and replication are under development. In this review, we provide an update on the latest advances in experimental studies on non-coding RNAs (ncRNAs), oncogenes and oncoproteins. All the articles addressed the crosstalk between different ncRNAs, oncogenes and oncoproteins, as well as their upstream and downstream products targeting LCSCs. In this review, we summarize three pathways, the Wnt/β-catenin signaling pathway, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway, and interleukin 6/Janus kinase 2/signal transducer and activator of transcription 3 (IL6/JAK2/STAT3) signaling pathway, and their targeting gene, c-Myc. Furthermore, we conclude that octamer 4 (OCT4) and Nanog are two important functional genes that play a pivotal role in LCSC regulation and HCC prognosis.

The oncogenic potential of NANOG: An important cancer induction mediator

Cancer stem cells (CSCs) are a unique population in the tumor, but they only comprise 2%-5% of the tumor bulk. Although CSCs share several features with embryonic stem cells, CSCs can give rise to the tumor cells. CSCs overexpress embryonic transcription factor NANOG, which is downregulated in differentiated tissues. This transcription factor confers CSC's stemness, unlimited self-renewal, metastasis, invasiveness, angiogenesis, and drug-resistance with the assistance of WNT, OCT4, SOX2, Hedgehog, BMI-1, and other complexes. NANOG facilitates CSCs development via multiple pathways, like angiogenesis and lessening E-cadherin expression levels, which paves the road for metastasis. Moreover, NANOG represses apoptosis and leads to drug-resistance. This review aims to highlight the pivotal role of NANOG and the pertained pathways in CSCs. Also, this current study intends to demonstrate that targeting NANOG can dimmish the CSCs, sensitize the tumor to chemotherapy, and eradicate the cancer cells.

Cancer Stem Cells as a Potential Target to Overcome Multidrug Resistance

Multidrug resistance (MDR), which is a significant impediment to the success of cancer chemotherapy, is attributable to various defensive mechanisms in cancer. Initially, overexpression of ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp) was considered the most important mechanism for drug resistance; hence, many investigators for a long time focused on the development of specific ABC transporter inhibitors. However, to date their efforts have failed to develop a clinically applicable drug, leaving only a number of problems. The concept of cancer stem cells (CSCs) has provided new directions for both cancer and MDR research. MDR is known to be one of the most important features of CSCs and thus plays a crucial role in cancer recurrence and exacerbation. Therefore, in recent years, research targeting CSCs has been increasing rapidly in search of an effective cancer treatment. Here, we review the drugs that have been studied and developed to overcome MDR and CSCs, and discuss the limitations and future perspectives.

MicroRNA Expression Profiling of Normal and Malignant Human Colonic Stem Cells Identifies miRNA92a as a Regulator of the LRIG1 Stem Cell Gene

MicroRNAs (miRNAs) have a critical role in regulating stem cells (SCs) during development, and because aberrant expression of miRNAs occurs in various cancers, our goal was to determine if dysregulation of miRNAs is involved in the SC origin of colorectal cancer (CRC). We previously reported that aldehyde dehydrogenase (ALDH) is a marker for normal and malignant human colonic SCs and tracks SC overpopulation during colon tumorigenesis. MicroRNA expression was studied in ALDH-positive SCs from normal and malignant human colon tissues by Nanostring miRNA profiling. Our findings show that: (1) A unique miRNA signature distinguishes ALDH-positive CRC cells from ALDH-positive normal colonic epithelial cells, (2) Expression of four miRNAs (miRNA200c, miRNA92a, miRNA20a, miRNA93) are significantly altered in CRC SCs compared to normal colonic SCs, (3) miRNA92a expression is also upregulated in ALDH-positive HT29 CRC SCs as compared to ALDH-negative SCs, (4) miRNA92a targets the 3′UTR of LRIG1 SC gene, and (5) miRNA92a modulates proliferation of HT29 CRC cells. Thus, our findings indicate that overexpression of miRNA92a contributes to the SC origin of CRC. Strategies designed to modulate miRNA expression, such as miRNA92a, may provide ways to target malignant SCs and to develop more effective therapies against CRC.

miR-206 inhibits liver cancer stem cell expansion by regulating EGFR expression

Liver cancer stem cells (CSCs) are involved in tumorigenesis, progression, drug resistance and recurrence of hepatocellular carcinoma (HCC). However, the underlying mechanism for the propagation of liver cancer stem cells was unclear. Herein, we observed miR-206 expression was reduced in both chemoresistant HCCs and recurrent HCCs from patients. A dramatically decrease of miR-206 was detected in cluster of differentiation 133 (CD133) or epithelial cell adhesion molecule (EpCAM)-positive liver CSCs and in CSC-enriched hepatoma spheres. Functional studies revealed that a forced expression of miR-206 inhibited liver CSCs expansion by suppressing the dedifferentiation of hepatoma cells and attenuating the self-renewal of liver CSCs. Mechanistically, bioinformatic and luciferase reporter analysis identified epidermal growth factor receptor (EGFR) as a direct target of miR-206. Moreover, miR-206 downregulated the expression of EGFR in liver CSCs. There was a significant inverse correlation between miR-206 and EGFR mRNA expression in HCC samples. Special EGFR inhibitor Gefitinib abolished the discrepancy in liver CSC proportion and the self-renewal capacity between miR-206 overexpression hepatoma cells and control cells, which further confirmed that EGFR was required in miR-206-inhibited liver CSCs expansion. Conclusion: miR-206 could suppress HCC cell dedifferentiation and liver CSCs expansion by targeting EGFR signaling.

SET domain-containing 5 is a potential prognostic biomarker that promotes esophageal squamous cell carcinoma stemness

SET domain-containing 5 (SETD5) is an uncharacterized member of the protein lysine methyltransferase family. Although it was reported that SETD5 gene mutations are associated with the several types of human cancer, its functional role in esophageal squamous cell carcinoma (ESCC) progression has not been fully elucidated. In the present study, we used tissue samples from 147 patients with ESCC and ESCC cell lines to determine the clinicopathological significance of SETD5 in ESCC and its effects on ESCC stemness. We performed immunohistochemical staining, immunofluorescence imaging, and tumor sphere formation, colony formation, flow cytometry, wound healing, Transwell, and western blotting assays. SETD5 expression was upregulated in ESCC tissue and associated with primary tumor (pT) stage, clinical stage, lymph node metastasis, shorter overall survival rate, and disease-free survival rate. Cox regression analyses indicated that SETD5 is an independent poor prognostic factor of ESCC. In addition, SETD5 expression was correlated with cancer stemness-related protein, hypoxia-inducible factor-1α (HIF-1α), and CD68 expression. Moreover, immunofluorescence analysis revealed that SETD5 was co-localized with CD44 and SOX2 in TE10 and TE11 cells and that exposing cells to cobalt chloride increased HIF-1α, SETD5, and stemness-related protein expression in a time-dependent manner. Furthermore, SETD5 expression was significantly correlated with the expression of cell cycle-related genes and PI3K/Akt signaling pathway-related proteins. Finally, knocking down SETD5 downregulated the expression of stemness-related and PI3K/Akt signaling pathway proteins, while inhibiting tumor spheroid formation, cell proliferation, migration, and invasion in ESCC cells. These results indicate that SETD5 expression is associated with cancer stemness and that SETD5 is a potential prognostic biomarker and therapeutic target for ESCC.

miR-552 Regulates Liver Tumor-Initiating Cell Expansion and Sorafenib Resistance

MicroRNAs (miRNAs) are involved in tumorigenesis, progression, recurrence, and drug resistance of hepatocellular carcinoma (HCC). However, few miRNAs have been identified and entered clinical practice. Herein, we report that microRNA (miR)-552 is upregulated in HCC tissues and has an important function in liver tumor-initiating cells (T-ICs). Functional studies revealed that a forced expression of miR-552 promotes liver T-IC self-renewal and tumorigenesis. Conversely, miR-552 knockdown inhibits liver T-IC self-renewal and tumorigenesis. Mechanistically, miR-552 downregulates phosphatase and tensin homolog (PTEN) via its mRNA 3' UTR and activates protein kinase B (AKT) phosphorylation. Our clinical investigations elucidated the prognostic value of miR-552 in HCC patients. Furthermore, miR-552 expression determines the responses of hepatoma cells to sorafenib treatment. The analysis of patient cohorts and patient-derived xenografts (PDXs) further demonstrated that miR-552 may predict sorafenib benefits in HCC patients. In conclusion, our findings revealed the crucial role of the miR-552 in liver T-IC expansion and sorafenib response, rendering miR-552 an optimal target for the prevention and intervention in HCC.

miR-552 promotes ovarian cancer progression by regulating PTEN pathway

Background

Increasing researches have demonstrated the critical functions of MicroRNAs (miRNAs) in the progression of malignant tumors, including ovarian cancer. It was reported that miR-552 was an important oncogene in both breast cancer and colorectal cancer. However, the role of miR-552 in ovarian cancer (OC) remains to be elucidated.

Methods

RT-PCR and western blot analysis were used to detect the expression of miR-552 and PTEN. The impact of miR-552 on ovarian cancer proliferation and metastasis was investigated in vitro. The prognostic value of miR-552 was evaluated using the online bioinformatics tool Kaplan-Meier plotter.

Results

In the present study, we for first found that miR-552 was upregulated in ovarian cancer, especially in metastatic and recurrence ovarian cancer. Forced miR-552 expression promotes the growth and metastasis of ovarian cancer cells. Consistently, miR-552 interference inhibits the proliferation and metastasis of ovarian cancer cells. Mechanically, bioinformatics and luciferase reporter analysis identified Phosphatase and tension homolog (PTEN) as a direct target of miR-552. miR-552 downregulated the PTEN mRNA and protein expression in ovarian cancer cells. Furthermore, the PTEN siRNA abolishes the discrepancy of growth and metastasis capacity between miR-552 mimic ovarian cells and control cells. More importantly, upregulation of miR-552 predicts the poor prognosis of ovarian cancer patients.

Conclusion

Our findings revealed that miR-552 could promote ovarian cancer cells progression by targeting PTEN signaling and might therefore be useful to predict patient prognosis.

miR-219 regulates liver cancer stem cell expansion via E-cadherin pathway

Liver cancer stem cells contribute to tumorigenesis, progression, recurrence and drug resistance of hepatocellular carcinoma (HCC). However, the underlying mechanism for the propagation of liverCSCs is not fully understood yet. Here we show that miR-219 is upregulated in liver CSCs. Knockdown of miR-219 attenuates the self-renewal and tumorigenicity of liver CSCs. Conversely, miR-219 overexpressing enhances the self-renewal and tumorigenicity of liver CSCs.Mechanistically,miR-219 downregulates E-cadherin via itsmRNA 3'UTR in liver CSCs. The correlation between miR-219 and E-cadherin is validated in human HCC tissues. Furthermore, the miR-219 expression determines the responses of hepatoma cells to sorafenib treatment. Our findings indicate that miR-219 plays a critical role in liver CSCs expansion and sorafenib response, rendering miR-219 as an optimal target for the prevention and intervention of HCC.Abbreviations: HCC: Hepatocellular carcinoma; CSCs: cancer stem cells; DMEM: Dulbecco's modified Eagle's medium; FBS: fetal bovine serum; OS: overall survival.

miR-613 inhibits liver cancer stem cell expansion by regulating SOX9 pathway

Liver cancer stem cells (CSCs) contribute to tumorigenesis, progression, drug resistance and recurrence of hepatocellular carcinoma (HCC). However, the underlying mechanism for the propagation of liver CSCs remains unclear. Herein, we observed miR-613 expression was downregulated in both chemoresistant and recurrent HCC patients. A remarkable decrease in miR-613 was detected in CD24 or OV6-positive liver CSCs and CSC-enriched hepatoma spheres. Down-regulation of miR-613 facilitated liver CSCs expansion by promoting the dedifferentiation of hepatoma cells and enhancing the self-renewal of liver CSCs. Mechanistically, bioinformatic and luciferase reporter analysis identified SOX9 as a direct target of miR-613. Overexpression of miR-613 inhibited the expression of SOX9 in HCC cells. Special SOX9 siRNA abolished the discrepancy in liver CSCs proportion and the self-renewal capacity between miR-613 overexpression hepatoma cells and control cells, which further confirmed that SOX9 was required in miR-613-inhibited liver CSCs expansion. Furthermore, hepatoma cells with miR-613 overexpression performed more sensitivity to cisplatin or sorafenib treatment. Conclusion: miR-613 could inhibit HCC cell dedifferentiation and liver CSCs expansion by targeting SOX9 signaling and may prove to be a novel therapeutic target for HCC patients.

Dual Laplacian regularized matrix completion for microRNA-disease associations prediction

Since lots of miRNA-disease associations have been verified, it is meaningful to discover more miRNA-disease associations for serving disease diagnosis and prevention of human complex diseases. However, it is not practical to identify potential associations using traditional biological experimental methods since the process is expensive and time consuming. Therefore, it is necessary to develop efficient computational methods to accomplish this task. In this work, we introduced a matrix completion model with dual Laplacian regularization (DLRMC) to infer unknown miRNA-disease associations in heterogeneous omics data. Specifically, DLRMC transformed the task of miRNA-disease association prediction into a matrix completion problem, in which the potential missing entries of the miRNA-disease association matrix were calculated, the missing association can be obtained based on the prediction scores after the completion procedure. Meanwhile, the miRNA functional similarity and the disease semantic similarity were fully exploited to serve the miRNA-disease association matrix completion by using a dual Laplacian regularization term. In the experiments, we conducted global and local Leave-One-Out Cross Validation (LOOCV) and case studies to evaluate the efficacy of DLRMC on the Human miRNA-disease associations dataset obtained from the HMDDv2.0 database. As a result, the AUCs of DLRMC is 0.9174 and 0.8289 in global LOOCV and local LOOCV, respectively, which significantly outperform a variety of previous methods. In addition, in the case studies on four significant diseases related to human health including Colon Neoplasms, Kidney neoplasms, Lymphoma and Prostate neoplasms, 90%, 92%, 92% and 94% out of the top 50 predicted miRNAs has been confirmed, respectively.

miR-186-5p promotes cell growth, migration and invasion of lung adenocarcinoma by targeting PTEN

OBJECTIVE

To explore the expression of miR-186-5p in lung adenocarcinoma (LUAD) and its possible function associated with cancer cell proliferation, migration and invasion.

METHODS

MiR-186-5p expression levels in LUAD samples, human LUAD cell lines H1299 and NCI-H1975, and normal human lung epithelial cell line BEAS-IB were assessed by quantitative real-time PCR (qRT-PCR). H1299 and NCI-H1975 cells were transfected with miR-186-5p mimic or miRNA negative control. CCK-8 assay was performed to evaluate the cell proliferation. Transwell assay and transwell-matrigel™ invasion assay were applied to assess the migration and invasion abilities of H1299 and NCI-H1975 cells.

RESULTS

miR-186-5p expression was significantly up-regulated in LUAD tumor tissues and LUAD cell lines as compared with tumor-adjacent tissues and normal human lung epithelial cells, respectively. MiR-186-5p overexpression remarkably promoted the proliferation, migration and invasion of LUAD cells. Furthermore, phosphatase and tensin homolog (PTEN) was a direct target of miR-186-5p verified by luciferase reporter assay. Overexpression of PTEN significantly suppressed LUAD cells to proliferate, migrate and invade. MiR-186-5p overexpression-induced LUAD cell phenotype could be partially rescued by co-overexpression of miR-186-5p and PTEN.

CONCLUSION

This study demonstrated that miR-186-5p is up-regulated in LUAD, and functionally associated with cell proliferation, migration and invasion. MiR-186-5p promotes the proliferation, migration and invasion of LUAD cells by targeting PTEN. MiR-186-5p may be utilized as a novel molecular marker and therapeutic target of LUAD.

Enhancer Domains in Gastrointestinal Stromal Tumor Regulate KIT Expression and Are Targetable by BET Bromodomain Inhibition

Gastrointestinal stromal tumor (GIST) is a mesenchymal neoplasm characterized by activating mutations in the related receptor tyrosine kinases KIT and PDGFRA. GIST relies on expression of these unamplified receptor tyrosine kinase (RTK) genes through a large enhancer domain, resulting in high expression levels of the oncogene required for tumor growth. Although kinase inhibition is an effective therapy for many patients with GIST, disease progression from kinase-resistant mutations is common and no other effective classes of systemic therapy exist. In this study, we identify regulatory regions of the KIT enhancer essential for KIT gene expression and GIST cell viability. Given the dependence of GIST upon enhancer-driven expression of RTKs, we hypothesized that the enhancer domains could be therapeutically targeted by a BET bromodomain inhibitor (BBI). Treatment of GIST cells with BBIs led to cell-cycle arrest, apoptosis, and cell death, with unique sensitivity in GIST cells arising from attenuation of the KIT enhancer domain and reduced KIT gene expression. BBI treatment in KIT-dependent GIST cells produced genome-wide changes in the H3K27ac enhancer landscape and gene expression program, which was also seen with direct KIT inhibition using a tyrosine kinase inhibitor (TKI). Combination treatment with BBI and TKI led to superior cytotoxic effects in vitro and in vivo, with BBI preventing tumor growth in TKI-resistant xenografts. Resistance to select BBI in GIST was attributable to drug efflux pumps. These results define a therapeutic vulnerability and clinical strategy for targeting oncogenic kinase dependency in GIST. SIGNIFICANCE: Expression and activity of mutant KIT is essential for driving the majority of GIST neoplasms, which can be therapeutically targeted using BET bromodomain inhibitors.

miR-181b/Notch2 overcome chemoresistance by regulating cancer stem cell-like properties in NSCLC

Background

Lung cancer stem cells have the ability to self-renew and are resistant to conventional chemotherapy. MicroRNAs (miRNAs) regulate and control the expression and function of many target genes; therefore, miRNA disorders are involved in the pathogenesis of human diseases, such as cancer. However, the effects of miRNA dysregulation on tumour stemness and drug resistance have not been fully elucidated. miR-181b has been reported to be a tumour suppressor miRNA and is associated with drug-resistant non-small cell lung cancer.

Methods

Cancer stem cell (CSC)-like properties were tested by a cell proliferation assay and flow cytometry; miR-181b expression was measured by real-time PCR; and Notch2 and related proteins were detected by Western blotting and immunohistochemistry. A mouse xenograft model was also established.

Results

In this study, we found that ectopic miR-181b expression suppressed cancer stem cell properties and enhanced sensitivity to cisplatin (DDP) treatment by directly targeting Notch2. miR-181b could inactivate the Notch2/Hes1 signalling pathway. In addition, tumours from nude mice treated with miR-181b were significantly smaller than tumours from mice treated with control agomir. Decreased miR-181b expression and increased Notch2 expression were observed to have a significant relationship with overall survival (OS) and CSC-like properties in non-small cell lung cancer (NSCLC) patients.

Conclusions

This study elucidates an important role of miR-181b in the regulation of CSC-like properties, suggesting a potential therapeutic target for overcoming drug resistance in NSCLC.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1072-1) contains supplementary material, which is available to authorized users.

miR-365 regulates liver cancer stem cells via RAC1 pathway

Liver cancer stem cells (CSCs) were involved in tumorigenesis, progression, recurrence, and drug resistance of hepatocellular carcinoma (HCC). miR-365 was downregulated in hepatocellular carcinoma and inhibited HCC cell proliferation and invasion. However, the role of miR-365 in liver cancer stem cells was unknown. Herein, we observed a remarkable decrease of miR-365 expression in CD133 or EpCAM-positive liver CSCs as well as in CSC-enriched hepatoma spheres. Up-regulated miR-365 suppressed liver CSC expansion by inhibiting the dedifferentiation of hepatoma cells and decreasing the self-renewal ability of liver CSCs. Mechanistically, bioinformatic and luciferase reporter analysis identified Ras-related C3 botulinum toxin substrate 1 (RAC1) as a direct target of miR-365. Overexpression of miR-365 in hepatoma cells downregulated the RAC1 mRNA and protein expression. RAC1 also could promote the expansion of liver CSCs. The special RAC1 inhibitor EHop-106 or RAC1 overexpression abolished the discrepancy in liver CSC proportion and the self-renewal capacity between miR-365 overexpression hepatoma cells and control cells, which further confirmed that RAC1 was required in miR-365-suppressed liver CSCs expansion. miR-365 was downregulated in liver CSCs and could inhibit HCC cells dedifferentiation and liver CSCs expansion by targeting RAC1 signaling.

HGIMDA: Heterogeneous graph inference for miRNA-disease association prediction

Recently, microRNAs (miRNAs) have drawn more and more attentions because accumulating experimental studies have indicated miRNA could play critical roles in multiple biological processes as well as the development and progression of human complex diseases. Using the huge number of known heterogeneous biological datasets to predict potential associations between miRNAs and diseases is an important topic in the field of biology, medicine, and bioinformatics. In this study, considering the limitations in the previous computational methods, we developed the computational model of Heterogeneous Graph Inference for MiRNA-Disease Association prediction (HGIMDA) to uncover potential miRNA-disease associations by integrating miRNA functional similarity, disease semantic similarity, Gaussian interaction profile kernel similarity, and experimentally verified miRNA-disease associations into a heterogeneous graph. HGIMDA obtained AUCs of 0.8781 and 0.8077 based on global and local leave-one-out cross validation, respectively. Furthermore, HGIMDA was applied to three important human cancers for performance evaluation. As a result, 90% (Colon Neoplasms), 88% (Esophageal Neoplasms) and 88% (Kidney Neoplasms) of top 50 predicted miRNAs are confirmed by recent experiment reports. Furthermore, HGIMDA could be effectively applied to new diseases and new miRNAs without any known associations, which overcome the important limitations of many previous computational models.

miR-106b-5p promotes stem cell-like properties of hepatocellular carcinoma cells by targeting PTEN via PI3K/Akt pathway

Background

The miRNA miR-106b-5p has been previously reported to be increased in hepatocellular carcinoma (HCC) tissues compared to cirrhotic tissues. The purpose of this study was to detect its expression in HCC cell lines with distinct metastatic potentials and to explore the molecular mechanisms underlying HCC stemness and migration.

Methods

miR-106b-5p expression was studied in HCC tissues and cell lines. In vitro cancer stem cell (CSC)-like properties, cell migration and invasion were compared between HCC cell lines with upregulation or downregulation of miR-106b-5p. In vivo tail vein injection models were established to evaluate the role of miR-106b-5p in lung metastasis. Bioinformatics programs, luciferase reporter assay and rescue experiments were used to validate the downstream targets of miR-106b-5p. The relationship between the expression of the targeted gene and clinicopathological parameters was also analyzed.

Results

miR-106b-5p expression was higher in HCC tissues and cell lines than that in non-tumor tissues and hepatocyte Chang liver, respectively. Upregulation of miR-106b-5p exhibited a promoting role in CSC properties, cell migration and activation of phosphatidylinositol-3 kinase (PI3K)/Akt signaling in vitro, as well as in lung metastasis in vivo. However, downregulation of miR-106b-5p exhibited the opposite effect. Furthermore, PTEN was verified as a direct target of miR-106b-5p. Upon clinicopathological analysis, lower level of PTEN was significantly associated with more aggressive characteristics. Patients with high PTEN expression had longer overall survival and disease-free survival.

Conclusion

miR-106b-5p promotes HCC stemness maintenance and metastasis by targeting PTEN via PI3K/Akt pathway. Inhibition of miR-106b-5p might be effective therapeutic strategies to treat advanced HCC.

DICER governs characteristics of glioma stem cells and the resulting tumors in xenograft mouse models of glioblastoma

The RNAse III endonuclease DICER is a key regulator of microRNA (miRNA) biogenesis and is frequently decreased in a variety of malignancies. We characterized the role of DICER in glioblastoma (GB), specifically demonstrating its effects on the ability of glioma stem-like cells (GSCs) to form tumors in a mouse model of GB. DICER silencing in GSCs reduced their stem cell characteristics, while tumors arising from these cells were more aggressive, larger in volume, and displayed a higher proliferation index and lineage differentiation. The resulting tumors, however, were more sensitive to radiation treatment. Our results demonstrate that DICER silencing enhances the tumorigenic potential of GSCs, providing a platform for analysis of specific relevant miRNAs and development of potentially novel therapies against GB.

ABC Transporters in Cancer Stem Cells: Beyond Chemoresistance

The efficacy of chemotherapy is one of the main challenges in cancer treatment and one of the major obstacles to overcome in achieving lasting remission and a definitive cure in patients with cancer is the emergence of cancer resistance. Indeed, drug resistance is ultimately accountable for poor treatment outcomes and tumour relapse. There are various molecular mechanisms involved in multidrug resistance, such as the change in the activity of membrane transporters primarily belonging to the ATP binding cassette (ABC) transporter family. In addition, it has been proposed that this common feature could be attributed to a subpopulation of slow-cycling cancer stem cells (CSCs), endowed with enhanced tumorigenic potential and multidrug resistance. CSCs are characterized by the overexpression of specific surface markers that vary in different cancer cell types. Overexpression of ABC transporters has been reported in several cancers and more predominantly in CSCs. While the major focus on the role played by ABC transporters in cancer is polarized by their involvement in chemoresistance, emerging evidence supports a more active role of these proteins, in which they release specific bioactive molecules in the extracellular milieu. This review will outline our current understanding of the role played by ABC transporters in CSCs, how their expression is regulated and how they support the malignant metabolic phenotype. To summarize, we suggest that the increased expression of ABC transporters in CSCs may have precise functional roles and provide the opportunity to target, particularly these cells, by using specific ABC transporter inhibitors.

MicroRNA-31 suppresses the self-renewal capability of α2δ1+ liver tumor-initiating cells by targeting ISL1

Accumulating evidence demonstrates that miRNAs, a class of small non-coding RNAs, are involved in the regulation of tumor-initiating cells (TICs) which are considered to be the origin of cancer development according to the cancer stem cell hypothesis. We have previously identified that miR-31 may play suppressive roles in α2δ1⁺ hepatocellular carcinoma (HCC) TICs. Here, we confirm that the expression of miR-31 is significantly downregulated in α2δ1⁺ HCC TICs. Overexpression of miR-31 in α2δ1⁺ HCC TICs results in significant suppression of the self-renewal and tumorigenicity abilities of these cells. Conversely, knockdown the expression of miR-31 in PLC/PRF/5 cells is able to reprogram them into TICs with stem cell-like properties. Furthermore, the expression of ISL LIM Homeobox 1(ISL1), a transcription factor involved in recognition of undifferentiated cardiac progenitors, is negatively regulated by miR-31, and the luciferase reporters’ activities with the 3′-UTRs of ISL1 are inhibited significantly by miR-31. Collectively, our results suggest that miR-31 can negatively regulate the self-renewal ability of α2δ1⁺ liver TICs via silencing ISL1.

Oct4 induces EMT through LEF1/β-catenin dependent WNT signaling pathway in hepatocellular carcinoma

Octamer 4 (Oct4), a member of the Pit-Oct-Unc transcription factor family required to maintain self-renewal and pluripotency of embryonic stem cells, has been previously identified to be associated with tumorigenesis and malignant transformation of numerous types of cancer including hepatocellular carcinoma (HCC). The present data shows that Oct4 enhances cancer stem cell properties and increases invasion ability in the Huh7 cell line. To increase understanding of the role of Oct4 in HCC, the present study used a functional genomics approach and analyzed the resulting transcriptional profiles to identify Oct4-dependent genes in Huh7. Affymetrix GeneChip Human genome U133 Plus 2.0 Arrays were used to determine differential gene expression profiles and then validated by quantitative polymerase chain reaction. The present study found that altered expression of 673 genes (fold-change ≥2) affected multiple signaling pathways linked with self-renew and metastasis. Among these differentially expressed genes, the present study noticed that the key component of the WNT signaling pathway lymphoid enhancer binding factor 1 (LEF1) and Twist Family BHLH transcription factor 1 were upregulated by Oct4, whilst cadherin 2 was downregulated. Additional studies found that the nuclear β-catenin aggregation was increased in Oct4 overexpressed HCC cell lines. These results suggest that Oct4 regulates LEF1 to active LEF1/β-catenin dependent WNT signaling pathway and promote epithelial-mesenchymal transition. The present findings provide novel mechanistic insight into an important role of Oct4 in HCC.

Implications of cancer stem cells in developing therapeutic resistance in oral cancer

Conventional therapeutics are often frequented with recurrences, refraction and regimen resistance in oral cavity cancers which are predominantly manifested by cancer stem cells (CSCs). During oncoevolution, cancer cells may undergo structural and functional reprogramming wherein they evolve as highly tolerant CSC phenotypes with greater survival advantages. The CSCs possess inherent and exclusive properties including self-renewal, hierarchical differentiation, and tumorigenicity that serve as the basis of chemo-radio-resistance in oral cancer. However, the key mechanisms underlying the CSC-mediated therapy resistance need to be further elucidated. A spectrum of dysfunctional cellular pathways including the developmental signaling, apoptosis, autophagy, cell cycle regulation, DNA damage responses and epigenetic regulations protect the CSCs from conventional therapies. Moreover, tumor niche shelters CSCs and creates an immunosuppressive environment favoring the survival of CSCs. Maintenance of lower redox status, epithelial-to-mesenchymal transition (EMT), metabolic reprogramming and altered drug responses are the accessory features that aid in the process of chemo-radio-resistance in oral CSCs. This review deals with the functional and molecular basis of cancer cell pluripotency-associated resistance highlighting the abrupt fundamental cellular processes; targeting these events may hold a great promise in the successful treatment of oral cancer.

Regulatory mechanisms of microRNAs in lung cancer stem cells

Increasing evidence suggests that cancer stem cells (CSCs) are a key occurrence in the process of many human cancers. Lung cancer is the most common aggressive malignancy and cause of cancer death worldwide. The research on lung cancer stem cells has been highlighted for many years. Lung CSCs seem to play a major role in lung cancer metastasis, drug resistance and tumour-self-renewal. MicroRNAs (miRNAs), a class of newly emerging small noncoding RNAs that act as post-transcriptional regulators of gene expression, have been demonstrated to serve as a vital player in fine-tuning a number of biological activities ranging from embryogenesis to programmed cell death as well as tumourigenesis. In recent years, several miRNAs have been highlighted to be specifically expressed in CSCs. The miRNA profile of CSCs is remarkably different from non-stem cancer cells. As such, many miRNAs have been shown to regulate self-renewal and differentiation properties of CSCs. In this review, we present the latest findings on miRNAs that regulate the tumour microenvironment of lung CSCs with the goal to prompt the development of novel therapeutic strategies for patients with lung cancer.

miR-612 suppresses stem cell-like property of hepatocellular carcinoma cells by modulating Sp1/Nanog signaling

In our previous study we found that miR-612 negatively regulated stem cell-like property and tumor metastasis of hepatocellular carcinoma cells (HCC). In this study, we try to elucidate underlying mechanism of the regulation, and find that miR-612 inversely modulate the mRNA and protein level of epithelial cell adhesion molecule as well as CD133, negatively regulate the numbers and sizes of tumor spheres, directly inhibit the protein level of Sp1, and subsequently reduce transcription activity of Nanog. Of importance, the higher levels of Sp1 and Nanog in biopsies are the more unfavorable prognoses of HCC patients are found after tumor resection. Taken together, miR-612 has a suppressive role on HCC stemness via Sp1/Nanog signaling pathway.

The roles of microRNAs in the progression of castration-resistant prostate cancer

Prostate cancer (PCa) is one of the leading causes of cancer-related death in men. PCa is androgen-dependent, and androgen-deprivation therapy is effective for first-line hormonal treatment, but the androgen-independent phenotype of PCa eventually develops, which is difficult to treat and has no effective cure. Recently, microRNAs have been discovered to have important roles in the initiation and progression of PCa, suggesting their use in diagnosis, predicting prognosis and development of treatment for castration-resistant PCa (CRPC). Understanding the networks of microRNAs and their target genes is necessary to ascertain their roles and importance in the development and progression of PCa. This review summarizes the current knowledge about microRNAs regulating PCa progression and elucidates the mechanism of progression to CRPC.

Anti-Apoptotic Effects of Lentiviral Vector Transduction Promote Increased Rituximab Tolerance in Cancerous B-Cells

Diffuse large B-cell lymphoma (DLBCL) is characterized by great genetic and clinical heterogeneity which complicates prognostic prediction and influences treatment efficacy. The most common regimen, R-CHOP, consists of a combination of anthracycline- and immuno-based drugs including Rituximab. It remains elusive how and to which extent genetic variability impacts the response and potential tolerance to R-CHOP. Hence, an improved understanding of mechanisms leading to drug tolerance in B-cells is crucial, and modelling by genetic intervention directly in B-cells is fundamental in such investigations. Lentivirus-based gene vectors are widely used gene vehicles, which in B-cells are an attractive alternative to potentially toxic transfection-based methodologies. Here, we investigate the use of VSV-G-pseudotyped lentiviral vectors in B-cells for exploring the impact of microRNAs on tolerance to Rituximab. Notably, we find that robust lentiviral transduction of cancerous B-cell lines markedly and specifically enhances the resistance of transduced germinal center B-cells (GCBs) to Rituximab. Although Rituximab works partially through complement-mediated cell lysis, increased tolerance is not achieved through effects of lentiviral transduction on cell death mediated by complement. Rather, reduced levels of PARP1 and persistent high levels of CD43 in Rituximab-treated GCBs demonstrate anti-apoptotic effects of lentiviral transduction that may interfere with the outcome and interpretation of Rituximab tolerance studies. Our findings stress that caution should be exercised exploiting lentiviral vectors in studies of tolerance to therapeutics in DLBCL. Importantly, however, we demonstrate the feasibility of using the lentiviral gene delivery platform in studies addressing the impact of specific microRNAs on Rituximab responsiveness.