Non-coding RNAs Functioning in Colorectal Cancer Stem Cells

Resistance to targeted therapy in metastatic colorectal cancer: Current status and new developments

Colorectal cancer (CRC) is one of the most lethal and common malignancies in the world. Chemotherapy has been the conventional treatment for metastatic CRC (mCRC) patients. However, the effects of chemotherapy have been unsatisfactory. With the advent of targeted therapy, the survival of patients with CRC have been prolonged. Over the past 20 years, targeted therapy for CRC has achieved substantial progress. However, targeted therapy has the same challenge of drug resistance as chemotherapy. Consequently, exploring the resistance mechanism and finding strategies to address the resistance to targeted therapy, along with searching for novel effective regimens, is a constant challenge in the mCRC treatment, and it is also a hot research topic. In this review, we focus on the current status on resistance to existing targeted therapies in mCRC and discuss future developments.

Long Intergenic Noncoding RNA 00641 Promotes Growth and Invasion of Colorectal Cancer through Regulating miR-450b-5p/GOLPH3 Axis

Background

Long noncoding RNAs (lncRNAs) have a vital function in tumor onset and progress. For instance, long intergenic noncoding RNA 00641 (LINC00641) has been linked to cancer modulation. Nonetheless, the precise biological roles of LINC00641 in colorectal cancer (CRC) remain elusive.

Methods

The expression levels of LINC00641 as well as the docking sites for LINC00641 and miR-450b-5p were analyzed using public data resources and web-based analytic tools. The putative downstream targets of miR-450b-5p were also predicted. Next, we evaluated the biological functions and the contents of LINC00641 in CRC both in vivo and in vitro. We next explored the influence of LINC00641 on the growth, migration, and infiltration of CRC cells via cell proliferation, migration, and invasion experiments. Besides, qRT-PCR, western blotting, flow cytometry, luciferase enzyme reporter assay, and in vivo tumorigenicity assays were conducted.

Results

Our results confirmed that LINC00641 was markedly upmodulated in CRC tissues and CRC cell lines, and the upmodulation was linked to poor survival. Notably, the proliferative and migratory abilities of HCT-116 and SW480 cells were significantly inhibited by the knockdown of LINC00641 both in vitro and in vivo, illustrating that LINC00641 exerted a tumor-promotion role in CRC. Mechanistically, LINC00641 could competitively bind miR-450b-5p, thereby expunging its inhibitory effect on GOLPH3 expression. Moreover, miR-450-5p and GOLPH3 were able to reverse LINC00641-mediated cellular processes.

Conclusions

Overall, the findings of this study suggest that LINC00641 promotes the proliferative and migratory abilities of CRC through sponging the miR-450b-5p/GOLPH3 axis.

Potential Prognosis and Diagnostic Value of AKT3, LSM12, MEF2C, and RAB30 in Exosomes in Colorectal Cancer on Spark Framework

Colorectal cancer (CRC) is a common malignant tumor and one of the leading causes of cancer-related deaths worldwide. CRC progression is greatly affected by the local microenvironment. In the study, we proposed a deep computational-based model for the classification of mRNA, lncRNA, and circRNA in exosomes. We, first, analyzed mRNA expression levels in CRC tumors and normal tissues. Secondly, we used GO and KEGG to analyze their functional enrichment. Thirdly, we analyzed the composition of immune cells in all TCGA samples and then evaluated the prognostic value of tumor-infiltrating immune cells in CRC. Lastly, we combined the TCGA dataset, i.e., COADN = 449 and ROADN = 6, for analysis and found that the expression levels of AKT3, LSM12, MEF2C, and RAB30 in exosomes were significantly correlated with tumor immune infiltration levels. The performance evaluation has shown that the proposed model based on neural networks performs better as compared to the existing methods. The proposed model can be used as a potential tool for the immune infiltration level and their role in cancer metastasis and progression, which can help us to explore potential strategies for CRC diagnosis, therapy, and prognosis.

Hypoxia effects on cancer stem cell phenotype in colorectal cancer: a mini-review

Colorectal cancer (CRC) is ranked third most incident and second most deadly around the world, and even though treatments significantly developed over the years, overall survival remains low. This scenario has the contribution of cancer stem cells (CSC), a subpopulation of the heterogeneous tumor bulk, considered to be responsible for the tumor maintenance, conventional therapies resistance, metastasis, and recurrence. In this regard, hypoxia appears as an important component of tumor microenvironment and CSC niche, being associated with a worse prognosis. Therefore, it is vital the study of hypoxia influence on CSC phenotype in CRC. The aim of this mini-review article is to present a brief overview on this field. Recent articles discoursed about CSC molecular regulation, signalling pathways, methods for the study of the topic, as well as molecules and drugs capacity of inhibiting the interplay of hypoxia-CSC. Finally, the studies demonstrated important results, extensively accessing the topics of cellular and molecular regulation and therapeutic intervention, being morphology an area to be more explored.

microRNAs: Small molecules with a large impact on colorectal cancer

Colorectal cancer (CRC) accounts for one of the main cancer-related mortality and morbidity worldwide. The molecular mechanisms of CRC development have been broadly investigated and, over the last decade, it has become evident that aberrant transcription of microRNAs (miRNAs), a class of small, noncoding RNA molecules, has a significant role in the inception and promotion of CRC. In the involved tissues of CRC, the transcription profile of miRNAs is modulated, and their expression templates are related with prognosis, diagnosis, and treatment outcomes. Here, in the current review, we attempted to discuss the latest information regarding the aberrantly expressed miRNAs in CRC and the advantages of utilizing miRNAs as biomarkers for early diagnosis and prognosis of CRC as well as potential therapeutic application. The effect of miRNAs involved in various signaling pathways, primarily p53, EGFR, Wnt, and TGF-β pathways, was clarified.

Melatonin: A regulator of the interplay between FoxO1, miR96, and miR215 signaling to diminish the growth, survival, and metastasis of murine adenocarcinoma

Melatonin (Mel.), also known as the magic hormone, is a nocturnally secreted hormone orchestrates the clearance of free radicals that have been built up and cumulated during day. This study aims to detect the impact of pineal gland removal on the incidence of tumor development and to assess the signaling pathways via which exogenous melatonin counteract cancer growth. This goal has been achieved by novel approach for pineal destruction using dental micromotor which validated by melatonin downregulation in blood plasma. Mice were injected sub-cutenously with Ehrlich cells to develop solid tumor as a murine model of breast cancer. The increase at tumor markers carcino embryonic antigen, TNFα, and nuclear factor kappa-light-chain-enhancer of activated B cells was over countered by exogenous melatonin supplementation (20 mg/kg) daily for 1 month. The anticancer effects of melatonin were significantly mediated by scavenging H₂ O₂ and NO and diminishing of lipid peroxidation marker malondialdehyde. The real-time polymerase chain Rx analyses indicated a significant effect of Melatonin in upregulating the expression of miR215, fork head box protein O1 (foxO1), and downregulation of miR96. Flowcytometric analyses indicated a significant effect of melatonin on induction of cell cycle arrest at G1 phase which was further confirmed by Ki67 downregulation. Immunohistochemical analyses indicated the role of melatonin in upregulating P53-dependent apoptosis and downregulating CD44 signaling for survivin, matrix metallo-protein kinase 2, and vascular endothelial growth factor to inhibit cell survival and metastasis. In conclusion, this study sheds the light on M./P53/miR215/CD44 with an emphasis on M./miR96//foxO1 signaling cascades, as a novel pathway of melatonin signaling in adenocarcinoma to diminish cancer cell growth, survival and metastasis.

Identification of a lncRNA prognostic signature-related to stem cell index and its significance in colorectal cancer

Background: The relationship between long noncoding RNAs (lncRNAs) and the mRNA stemness index (mRNAsi) in colorectal cancer (CRC) is still unclear. Materials & methods: The mRNAsi, mRNAsi-related lncRNAs and their clinical significance were analyzed by bioinformatic approaches in The Cancer Genome Atlas (TCGA)-COREAD dataset. Results: mRNAsi was negatively related to pathological features but positively related to overall survival and recurrence-free survival in CRC. A five mRNAsi-related lncRNAs prognostic signature was further developed and showed independent prognostic factors related to overall survival in CRC patients, due to the five mRNAsi-related lncRNAs involved in several pathways of the cancer stem cells and malignant cancer cell phenotypes. Conclusion: The present study highlights the potential roles of mRNAsi-related lncRNAs as alternative prognostic markers.

The Role of non-coding RNAs in colorectal cancer, with a focus on its autophagy

Colorectal cancer (CRC) is one of malignant afflictions burdening people worldwide, mainly caused by shortages of effective medical intervention and poorly mechanistic understanding of the pathogenesis of CRC. Non-coding RNAs (ncRNAs) are a type of heterogeneous transcripts without the capability of coding protein, but have the potency of regulating protein-coding gene expression. Autophagy is an evolutionarily conserved catabolic process in which cytoplasmic contents are delivered to cellular lysosomes for degradation, resulting in the turnover of cellular components and producing energy for cell functions. A growing body of evidence reveals that ncRNAs, autophagy, and the crosstalks of ncRNAs and autophagy play intricate roles in the initiation, progression, metastasis, recurrence and therapeutic resistance of CRC, which confer ncRNAs and autophagy to serve as clinical biomarkers and therapeutic targets for CRC. In this review, we sought to delineate the complicated roles of ncRNAs, mainly including miRNAs, lncRNAs and circRNAs, in the pathogenesis of CRC, particularly focus on the regulatory role of ncRNAs in CRC-related autophagy, attempting to shed light on the complex pathological mechanisms, involving ncRNAs and autophagy, responsible for CRC tumorigenesis and development, so as to underpin the ncRNAs- and autophagy-based therapeutic strategies for CRC in clinical setting.

Cancer stem cells in colorectal cancer and the association with chemotherapy resistance

The incidence and mortality of colorectal cancer (CRC) have always been among the highest in the world, although the diagnosis and treatment are becoming more and more advanced. At present, the main reason is that patients have acquired drug resistance after long-term conventional drug treatment. An increasing number of evidences confirm the existence of cancer stem cells (CSCs), which are a group of special cells in cancer, only a small part of cancer cells. These special cell populations are not eliminated by chemotherapeutic drugs and result in tumor recurrence and metastasis after drug treatment. CSCs have the ability of self-renewal and multidirectional differentiation, which is associated with the occurrence and development of cancer. CSCs can be screened and identified by related surface markers. In this paper, the characteristic surface markers of CSCs in CRC and the related mechanism of drug resistance will be discussed in detail. A better understanding of the mechanism of CSCs resistance to chemotherapy may lead to better targeted therapy.

FENDRR: A pivotal, cancer-related, long non-coding RNA

Long non-coding RNAs (lncRNAs) have more than 200 nucleotides and do not encode proteins. Based on numerous studies, lncRNAs have emerged as new and crucial regulators of biological function and have been implicated in the pathogenesis of a variety of diseases, especially cancers. Specific lncRNAs have been identified as novel molecular biomarkers for cancer diagnosis, prognosis, and treatment efficacy. Fetal-lethal non-coding developmental regulatory RNA (FENDRR, also known as FOXF1-AS1) is a novel lncRNA that is located at chr3q13.31 and has four exons and 3099 nucleotides, and its genomic site is located at chr3q13.31. FENDRR is abnormally expressed in a variety of cancers and is significantly associated with different clinical characteristics. In addition, FENDRR has shown potential as a biomarker for cancer diagnosis, prognosis, and treatment. In this review, we summarize the current understanding of FENDRR and its mechanistic role in cancer progression. We also discuss recent insights into the clinical significance of FENDRR for cancer diagnosis, prognosis, and treatment.

Effects of long non-coding RNA myocardial infarction-associated transcript on retinal neovascularization in a newborn mouse model of oxygen-induced retinopathy

Whether long non-coding RNA myocardial infarction-associated transcript is involved in oxygen-induced retinopathy remains poorly understood. To validate this hypothesis, we established a newborn mouse model of oxygen-induced retinopathy by feeding in an oxygen concentration of 75 ± 2% from postnatal day 8 to postnatal day 12, followed by in normal air. On postnatal day 11, the mice were injected with the myocardial infarction-associated transcript siRNA plasmid via the vitreous cavity to knockdown long non-coding RNA myocardial infarction-associated transcript. Myocardial infarction-associated transcript siRNA transcription significantly inhibited myocardial infarction-associated transcript mRNA expression, reduced the phosphatidylinosital-3-kinase, phosphorylated Akt and vascular endothelial growth factor immunopositivities, protein and mRNA expression, and alleviated the pathological damage to the retina of oxygen-induced retinopathy mouse models. These findings suggest that myocardial infarction-associated transcript is likely involved in the retinal neovascularization in retinopathy of prematurity and that inhibition of myocardial infarction-associated transcript can downregulate phosphatidylinosital-3-kinase, phosphorylated Akt and vascular endothelial growth factor expression levels and inhibit neovascularization. This study was approved by the Animal Ethics Committee of Shengjing Hospital of China Medical University, China (approval No. 2016PS074K) on February 25, 2016.

Wnt/β‑catenin signaling: Causes and treatment targets of drug resistance in colorectal cancer (Review)

Colorectal cancer (CRC) is the third most common malignant tumor in humans. Chemotherapy is used for the treatment of CRC. However, the effect of chemotherapy remains unsatisfactory due to drug resistance. Growing evidence has shown that the presence of highly metastatic tumor stem cells, regulation of non-coding RNAs and the tumor microenvironment contributes to drug resistance mechanisms in CRC. Wnt/β-catenin signaling mediates the chemoresistance of CRC in these three aspects. Therefore, the present study analyzed the abundant evidence of the contribution of Wnt/β-catenin signaling to the development of drug resistance in CRC and discussed its possible role in improving the chemosensitivity of CRC, which may provide guidelines for its clinical treatment.

Emerging roles of long noncoding RNAs in cholangiocarcinoma: Advances and challenges

Cholangiocarcinoma (CCA), a cancer with a relatively low incidence rate, is usually associated with poor prognosis. Current modalities for the diagnosis and treatment of CCA patients are still far from satisfactory. In recent years, numerous long noncoding RNAs (lncRNAs) have been identified as crucial players in the development of various cancers, including CCA. Abnormally expressed lncRNAs in CCA, regulated by some upstream molecules, significantly influence the biological behavior of tumor cells and are involved in tumor development through various mechanisms, including interactions with functional proteins, participation in competing for endogenous RNA (ceRNA) regulatory networks, activation of cancer‐related signaling pathways and epigenetic modification of gene expression. Furthermore, several lncRNAs are closely associated with the clinicopathological features of CCA patients, and are promising biomarkers for diagnosing and prognostication of CCA. Some of these lncRNAs play an important role in chemotherapy drug resistance. In addition, lncRNAs have also been shown to be involved in the inflammation microenvironment of CCA and malignant outcome of CCA risk factors, such as cholestatic liver diseases. In view of the difficulty of diagnosing CCA, more attention should be paid to detectable lncRNAs in the serum or bile. This review summarizes the recent knowledge on lncRNAs in CCA and provides a new outlook on the molecular mechanisms of CCA development from the perspective of lncRNAs. Moreover, we also discussed the limitations of the current studies and differential expression of lncRNAs in different types of CCA.

WBSCR22 Competes with Long Non-coding RNA Linc00346 for miR-509-5p Binding Site to Regulate Cancer Stem Cell Phenotypes of Colorectal Cancer

Various Long non-coding RNAs (lncRNAs) and MicroRNAs (miRNAs) have been demonstrated to be involved in colorectal cancer stem cells (CSCs). WBSCR22 is a key gene we previously found that functions in colorectal cancer (CRC). This paper aims to investigate the effects of WBSCR22 and its corresponding miRNA and lncRNA in CRC. The expression of WBSCR22 was detected by Western blot and qRT-PCR analysis. Tumor sphere formation assays, CCK-8 analysis, and Transwell assays were applied to examine the colorectal cancer stem cell properties. Luciferase assay and biotin RNA pulldown assay were used to detect the interaction between miR-509-5p and WBSCR22/Linc00346. WBSCR22 is highly expressed in CRC and correlates with poor prognosis. Knockdown of WBSCR22 decreased the sphere-forming capacities, cell proliferation, and invasion abilities. WBSCR22 was negatively regulated by miR-509-5p. Linc00346 promoted the expression of WBSCR22 by adsorbing miR-509-5p. The Linc00346/miR-509-5p/WBSCR22 signal axis regulated the characteristics of colon cancer stem cells. Linc00346 regulated the expression of WBSCR22 by binding to miR-509-5p, thereby monitoring the characteristics of colorectal cancer stem cells. Thus, WBSCR22, Linc00346, and miR-509-5p might be utilized as potential targets for clinical diagnosis and treatment of CRC.

Are Long Noncoding RNAs New Potential Biomarkers in Gastrointestinal Stromal Tumors (GISTs)? The Role of H19 and MALAT1

Long noncoding RNAs (lncRNAs) are emerging as key regulators of genetic and epigenetic networks, and their deregulation may underlie complex diseases, such as carcinogenesis. Several studies described lncRNA alterations in patients with solid tumors. In particular, HOTAIR upregulation has been associated with tumor aggressiveness, metastasis, and poor survival in gastrointestinal stromal tumor (GIST) patients. We analyzed expression levels of other lncRNAs, H19 and MALAT1, in FFPE tissue specimens from 40 surgically resected and metastatic GIST patients, using real-time PCR analysis. H19 and MALAT1 were both upregulated in 50% of GIST patients. MALAT1 lncRNA expression levels seem to be correlated with c-KIT mutation status. The percentage of both H19 and MALAT1 upregulation was significantly higher in patients with time to progression (TTP) < 6 months as compared to patients with TTP > 6 months. The median TTP was significantly lower in patients with both H19 and MALAT1 lncRNA upregulation as compared to those with lncRNA downregulation. These data suggest a potential role for both H19 and MALAT1 lncRNAs as prognostic biomarker for the clinical selection of the best candidate to first-line treatment with imatinib.

LncRNA-cCSC1 modulates cancer stem cell properties in colorectal cancer via activation of the Hedgehog signaling pathway

Several long noncoding RNAs (lncRNAs) have been identified in various malignant tumors and determined to contribute to the process of tumorigenesis, including that of colorectal cancer (CRC). Cancer stem cells (CSCs) have been demonstrated to promote the expansion and maintain the invasion and metastasis of cancer cells, owing to their self-renewal capacity. However, the underlying modulation mechanism of CSC-associated lncRNAs in CRC remains largely unclear. Using integrated bioinformatic analysis, we identified a novel lncRNA (lncRNA-cCSC1) that is highly expressed in CRC and colorectal cancer stem cells (CRCSCs). The biological functions of lncRNA-cCSC1 were assessed in vitro and vivo through the silencing or upregulation of its expression. The depletion of lncRNA-cCSC1 markedly inhibited the self-renewal capacity of the CRCSCs and reduced their drug resistance to 5-fluorouracil. In contrast, lncRNA-cCSC1 overexpression increased the self-renewal effect. Furthermore, aberrant lncRNA-cCSC1 expression resulted in a concomitant alteration of smoothened (SMO) and GLI family zinc finger 1 (Gli1) expression in the Hedgehog (Hh) signaling pathway. Our study is the first to identify a novel lncRNA-cCSC1 in CRC and to indicate that it may regulate CSC-like properties via the Hh signaling pathway. Thus, lncRNA-cCSC1 could be a potential biomarker and promising therapeutic target for CRC.

Targeting Wnt Signaling via Notch in Intestinal Carcinogenesis

Proliferation and differentiation of intestinal epithelial cells is assisted by highly specialized and well-regulated signaling cascades. The Wnt pathway, which is one of the fundamental pathways in the intestine, contributes to the organization of proliferative intestinal crypts by positioning and cycling of intestinal stem cells and their derivatives. The Wnt pathway promotes differentiation of intestinal secretory cell types along the crypt-plateau and crypt-villus axis. In contrast to the Wnt pathway, the intestinal Notch cascade participates in cellular differentiation and directs progenitor cells towards an absorptive fate with diminished numbers of Paneth and goblet cells. Opposing activities of Notch and Wnt signaling in the regulation of intestinal stem cells and the enterocytic cell fate have been elucidated recently. In fact, targeting Notch was able to overcome tumorigenesis of intestinal adenomas, prevented carcinogenesis, and counteracted Paneth cell death in the absence of caspase 8. At present, pharmacological Notch inhibition is considered as an interesting tool targeting the intrinsic Wnt pathway activities in intestinal non-neoplastic disease and carcinogenesis.

lncRNA LINC00460 promoted colorectal cancer cells metastasis via miR-939-5p sponging

Background

lncRNAs are widely involved in multiple malignancies including colorectal cancer (CRC). The expression and function of long intergenic non-protein coding RNA 460 (LINC00460) in CRC remains obscure.

Methods

In the present study, quantitative real-time PCR assays were applied to detect the expression changes of LINC00460 and microRNA-939-5p (miR-939-5p) in CRC tissue specimens and cell lines. Western blot assays were used to measure the changes of LIMK2. Bioinformatics analysis, luciferase assays, and RNA pull-down assays were applied to determine the targeting binding effect between LINC00460 and miR-939-5p as well as LIMK2 and miR-939-5p. Transwell assays were used to evaluate the metastatic ability changes of CRC line HT29 and LOVO cells.

Results

We found that LINC00460 was upregulated and closely correlated to clinicopathological features and poor prognosis of patients with CRC. Functionally, we elucidated that LINC00460 promoted metastasis in CRC cell lines HT29 and LOVO. Further, we showed that LIMK2 was a downstream effector in the LINC00460-induced promotion of metastasis in CRC cells HT29 and LOVO. Through online bioinformatics analysis, LINC00460 and LIMK2 were demonstrated to share similar microRNA response elements for miR-939-5p. Then, LINC00460 and LIMK2 were verified to be the targets of miR-939-5p via a luciferase assay and an RNA pull-down assay. Also, miR-939-5p was showed to suppress metastasis by targeting of LIMK2. Lastly, we revealed that LINC00460 promoted LIMK2-mediated metastasis via miR-939-5p sponging in CRC cells HT29 and LOVO.

Conclusion

The findings of this study showed that LINC00460 works as an oncogene in CRC and promoted CRC cell metastasis via regulation of miR-939-3p/LIMK2 axial. The present study might provide a new target in treating CRC.

Circular RNA in Exosomes

Circular RNAs (circRNAs) are a novel family of non-coding endogenous RNAs discovered in all eukaryotic cells and generated through a particular mechanism of alternative splicing called "back-splicing". These molecules show multiple functions, by acting as modulators of gene and miRNA expression, and may have a role in several biological processes, such as cell proliferation and invasion with, tumour development and progression, and in several mechanisms underlying other diseases. Their presence has been shown to be abundant in several body fluids such as blood and saliva. Based on their biogenesis mechanism, circRNAs may be categorized into five classes: exonic circRNAs, intronic circRNAs, antisense circRNAs, sense overlapping circRNAs and intergenic circRNAs. Recently, the presence of circRNAs, in addition to that of miRNAs and long non-coding RNAs, has been detected also in small extracellular vesicles called exosomes. Investigating the presence and expression levels of serum exosomal circRNAs could allow us, in future, to discriminate cancer patients from healthy individuals, identifying new potential exosome-based cancer biomarkers.In this chapter, we briefly will describe the major features and functions of exosomal circRNAs, discussing their potential role as molecular biomarkers for diagnosis, prognosis and monitoring of complex diseases, including cancer.

Upregulation of NETO2 gene in colorectal cancer

BACKGROUND

Neuropilin and tolloid-like 2 (NETO2) is a single-pass transmembrane protein that has been shown primarily implicated in neuron-specific processes. Upregulation of NETO2 gene was also detected in several cancer types. In colorectal cancer (CRC), it was associated with tumor progression, invasion, and metastasis, and seems to be involved in epithelial-mesenchymal transition (EMT). However, the mechanism of NETO2 action is still poorly understood.

RESULTS

We have revealed significant increase in the expression of NETO2 gene and deregulation of eight EMT-related genes in CRC. Four of them were upregulated (TWIST1, SNAIL1, LEF1, and FOXA2); the mRNA levels of other genes (FOXA1, BMP2, BMP5, and SMAD7) were decreased. Expression of NETO2 gene was weakly correlated with that of genes involved in the EMT process.

CONCLUSIONS

We found considerable NETO2 upregulation, but no significant correlation between the expression of NETO2 and EMT-related genes in CRC. Thus, NETO2 may be involved in CRC progression, but is not directly associated with EMT.

Hedgehog signaling pathway in colorectal cancer: function, mechanism, and therapy

Colorectal cancer (CRC) is one of the most common gastrointestinal cancers worldwide. It is a complicated and often fatal cancer, and is related to a high disease-related mortality. Around 90% of mortalities are caused by the metastasis of CRC. Current treatment statistics shows a less than 5% 5-year survival for patients with metastatic disease. The development and metastasis of CRC involve multiple factors and mechanisms. The Hedgehog (Hh) signaling plays an important role in embryogenesis and somatic development. Abnormal activation of the Hh pathway has been proven to be related to several types of human cancers. The role of Hh signaling in CRC, however, remains controversial. In this review, we will go through previous literature on the Hh signaling and its functions in the formation, proliferation, and metastasis of CRC. We will also discuss the potential of targeting Hh signaling pathway in the treatment, prognosis, and prevention of CRC.

Knockdown of a DIS3L2 promoter upstream long noncoding RNA (AC105461.1) enhances colorectal cancer stem cell properties in vitro by down-regulating DIS3L2

A large number of studies have identified plentiful long noncoding RNAs (lncRNAs) associated with the development of multiple cancers. Some lncRNAs have also been found to be strongly linked with stem cell properties such as pluripotency and differentiation. However, only in a few cases have cancer stem cell (CSC)-related lncRNAs been studied. Commonly, the expression and function of lncRNAs are associated with adjacent protein coding transcripts. In the present study, we found an lncRNA (AC105461.1), a promoter upstream transcript of DIS3 mitotic control homolog (Saccharomyces cerevisiae)-like 2 (DIS3L2), may be closely connected with “stem cell-like” properties. We firstly investigated whether the expression of AC105461.1 was down-regulated in colorectal cancer (CRC) tissue samples. Subsequently, we explored the expression pattern of the lncRNA/mRNA gene pair between AC105461.1 and DIS3L2 in 47 CRC specimens by real-time polymerase chain reaction. The results showed that the expression of AC105461.1 was positively correlated with that of DIS3L2. Through CRC cell lines screening experiment, we found that AC105461.1 expression was highest in SW480 and lowest in SW620 cells. Moreover, the results obtained by overexpression experiment indicated that AC105461.1 expression was markedly elevated and DIS3L2 expression level was also apparently upregulated by plasmid cDNA-AC105461.1. In contrast, we further found that AC105461.1 expression level in AC105461.1 siRNA group was significantly knocked down in SW480 cells. Meanwhile, DIS3L2 expression was also markedly decreased. Importantly, we noticed that AC105461.1 overexpression impaired CSC properties, while its knockdown enhanced CSC properties, including self-renewal, migration, and invasion abilities. To further identify the influence of AC105461.1 expression on CSCs properties in CRC, CD133 and CD44, as current universal markers for characterizing CRC stem cells, were selected to perform flow cytometry analysis. As a result, we found that AC105461.1 overexpression reduced the percentage of CD133⁺CD44⁺, whereas its knockdown increased the percentage of CD133⁺CD44⁺. Taken together, our findings indicated that AC105461.1 may be a regulator of DIS3L2 and a mediator of CRC stem cells, and we speculate that AC105461.1 could be regarded as a promising biomarker and therapeutic target for CRC.