Mel-18 negatively regulates stem cell-like properties through downregulation of miR-21 in gastric cancer

Molecular Aspects of Regeneration Mechanisms in Holothurians

Holothurians, or sea cucumbers, belong to the phylum Echinodermata. They show good regenerative abilities. The present review provides an analysis of available data on the molecular aspects of regeneration mechanisms in holothurians. The genes and signaling pathways activated during the asexual reproduction and the formation of the anterior and posterior parts of the body, as well as the molecular mechanisms that provide regeneration of the nervous and digestive systems, are considered here. Damage causes a strong stress response, the signs of which are recorded even at late regeneration stages. In holothurian tissues, the concentrations of reactive oxygen species and antioxidant enzymes increase. Furthermore, the cellular and humoral components of the immune system are activated. Extracellular matrix remodeling and Wnt signaling play a major role in the regeneration in holothurians. All available morphological and molecular data show that the dedifferentiation of specialized cells in the remnant of the organ and the epithelial morphogenesis constitute the basis of regeneration in holothurians. However, depending on the type of damage, the mechanisms of regeneration may differ significantly in the spatial organization of regeneration process, the involvement of different cell types, and the depth of reprogramming of their genome (dedifferentiation or transdifferentiation).

Role of Exosomal miRNA in Bladder Cancer: A Promising Liquid Biopsy Biomarker

Bladder cancer (BCa) is the most prevalent neoplasia of the urinary tract. Unfortunately, limited improvements in effective BCa management have meant that it remains a challenging disease. Cystoscopy has been the gold standard for BCa diagnosis and surveillance for over two centuries but is an invasive and expensive approach. Recently, liquid biopsy has been identified as a promising field of cancer research, due to its noninvasiveness and ease of sampling. Liquid biopsy samples could provide comprehensive information regarding the genetic landscape of cancer and could track genomic evolution of the disease over time. Exosomes, which contain RNAs, DNAs, and proteins, are a potential source of tumor biomarkers in liquid biopsy samples. In particular, exosomal miRNAs (exomiRs) hold great promise as biomarkers for tumor development and progression. In this review, we provide an overview of liquid biopsy biomarkers, with a particular focus on the use of exomiRs as biomarkers of cancer, and summarize their clinical implications for BCa. Finally, we discuss the future perspectives of these biomarkers in cancer research.

Role of exosomes and exosomal microRNAs in cancer

A growing body of evidence indicates that exosomes play a critical role in the cell-cell communication process. Exosomes are biological nanoparticles with an average diameter of 30-100 nm in size and are produced by almost all cell types in the human body; however, cancer cells contain higher concentrations of exosomes than healthy cells. They are released into all body fluids and contain double-stranded DNA (originated from nucleus and mitochondria), a variety of RNA species, and specific protein biomarkers that can be utilized as cancer biomarkers and therapeutic targets, and lipids. Therefore, the specific exosomes secreted by tumor cells could be used to predict the existence of the presence of a tumor in cancer patients. This review summarizes the role of exosomes in cancer development and their potential utility in the clinic.

The Eupentacta fraudatrix transcriptome provides insights into regulation of cell transdifferentiation

The holothurian Eupentacta fraudatrix is a unique organism for studying regeneration mechanisms. Moreover, E. fraudatrix can quickly restore parts of its body and entire organ systems, yet at the moment, there is no data on the participation of stem cells in the process. To the contrary, it has been repeatedly confirmed that this process is only due to the transformation of terminally differentiated cells. In this study, we examine changes in gene expression during gut regeneration of the holothurian E. fraudatrix. Transcriptomes of intestinal anlage of the three stages of regeneration, as well as the normal gut, were sequenced with an Illumina sequencer (San Diego, CA, USA). We identified 14,617 sea urchin protein homologs, of which 308 were transcription factors. After analysing the dynamics of gene expression during regeneration and the map of biological processes in which they participate, we identified 11 factors: Ef-EGR1, Ef-ELF, Ef-GATA3, Ef-ID2, Ef-KLF1/2/4, Ef-MSC, Ef-PCGF2, Ef-PRDM9, Ef-SNAI2, Ef-TBX20, and Ef-TCF24. With the exception of TCF24, they are all involved in the regeneration, development, epithelial-mesenchymal transition, and immune response in other animals. We suggest that these transcription factors may also be involved in the transdifferentiation of coelomic epithelial cells into enterocytes in holothurians.

Increased expression of miR-146a, miR-10b, and miR-21 in cancer stem-like gastro-spheres

BACKGROUND

Gastric cancer remains one of the leading causes of cancer-associated mortalities globally. Accumulating evidence support the presence of gastric cancer stem cells (CSCs) and their role in the pathogenesis and therapeutic challenges of gastric cancer. MicroRNAs (miRNAs) may be influenced by the cellular differentiative state and as critical regulators of the cellular fate in development and cancer, can modulate the behavior of CSCs too. Here, we aimed to investigate the expression relevance of three prognostic miRNAs (miR-21, miR-10b, and miR-146a) in CSCs of AGS and MKN-45 gastric cancer cell lines.

METHODS

Serial sphere-forming assay in serum-free culture medium was used to enrich the cellular population with stem-like properties. Gastro-spheres were characterized by evaluating the stemness gene expression, clonogenicity, and resistance to docetaxel and cisplatin in comparison with their parental cells. The expression level of miRNAs in gastro-spheres and their parental cells was measured using quantitative reverse transcription polymerase chain reaction.

RESULTS

Gastro-spheres from both cell lines exhibit stem-like properties: upregulated stemness associated genes (P < 0.05), more colonogenicity and more resistance to docetaxel (P < 0.05). MKN-45 gastro-spheres exhibited upregulated expression of miR-21 (1.8-folds), miR-10b (1.34-folds) and miR-146a (4.8-folds; P < 0.05) compared with the parental cells. AGS-derived gastro-spheres showed upregulation of miR-21 (4.7-folds; P < 0.01), miR-10b (15.2-folds; P < 0.001) and miR-146a (39.3-folds; P < 0.05).

CONCLUSION

Our data exhibited upregulation of miR-21, miR-10b, and miR-146a in the stem-like gastro-spheres; however; their function in gastric CSCs remains to be verified by further experiments.

MiR-876-3p regulates cisplatin resistance and stem cell-like properties of gastric cancer cells by targeting TMED3

BACKGROUND AND AIM

Gastric cancer (GC), a prevalent tumor, exerts a major economic burden, and we aimed to explore miR-876-3p's effects on GC and related mechanisms.

METHODS

Cell viability was analyzed via CCK-8 and colony formation assay. Stem cell-like properties were examined via spheroid colony formation assay. mRNA abundance of key genes was analyzed via quantitative polymerase chain reaction. Protein level of TMED3 and stem cell markers was examined by western blot. TargetScan, luciferase, and biotin-miRNA pulldown assay were used to identify miR-876-3p's target.

RESULTS

MiR-876-3p was downregulated in GC, and its mRNA level had negative relationship with cisplatin resistance of GC. Moreover, decreased miR-876-3p expression level suggested poor prognosis of GC patients. MiR-876-3p inhibited drug resistance of cisplatin-resistant cell line SGC-7901/DDP and MKN-45/DDP, as shown by decreased cell viability, IC₅₀ , and colony formation ability. MiR-876-3p inhibited stem cell-like features and downregulated the expressions of Sox-2, Oct-4, CD133, and CD44 in GC cells. Luciferase and biotin-miRNA pulldown assay confirmed that TMED3 was miR-876-3p's direct target. TMED3 siRNA inhibited miR-876-3p's effects on cisplatin resistance and stem cell-like features of SGC-7901/DDP cells.

CONCLUSION

MiR-876-3p enhanced cisplatin sensitivity and restricted stem cell-like features of GC through targeting TMED3.

Overexpression of miR‑21 is involved in acute monocytic leukemia‑associated angiogenesis by targeting IL‑12

Angiogenesis is important in pathophysiological processes, including the pathogenesis of acute monocytic leukemia (AML). MicroRNA‑21 (miR‑21) is overexpressed and exhibits oncogenic activity in cancer. However, the biological mechanism underlying the effect of miR‑21 in AML remains to be fully elucidated. In the present study, the expression levels of miR‑21 and vascular endothelial growth factor (VEGF) were determined in 26 patients with AML and 28 healthy individuals. The secretion of VEGF was also measured following the transfection of THP‑1 cells with miR‑21 mimic or inhibitor. The supernatants of the THP‑1 cells, which were transfected with miR‑21 mimic, inhibitor or small interfering RNA (si)VEGF, respectively, were used to incubate human umbilical vein endothelial cells (HUVECs), following which tube formation of the HUVECs was measured. miR‑21 targets were predicted using a biological target prediction website and confirmed using a luciferase assay. The effects of interleukin (IL)‑12 were investigated by examining the tube formation of HUVECs and the secretion of VEGF following recombinant human (rh) IL‑12 pretreatment. The results revealed that miR‑21 and VEGF expression was significantly increased in the peripheral blood monocytes of the patients, compared with the healthy controls. There was negative correlation between the expression of IL‑12 and miR‑21 in the serum of patients with AML. Furthermore, supernatant VEGF levels from the miR‑21 mimic‑transfected THP‑1 cells were increased, whereas a decreasing trend was observed in the miR‑21 inhibitor group. The angiogenic ability of the HUVECs pretreated with supernatant from the THP‑1 cells transfected with miR‑21 mimic was higher, and was lower in THP‑1 cells co‑transfected with miR‑21 mimic and siVEGF, compared with the miR‑21 mimic only group. A luciferase assay demonstrated that IL‑12 was the direct target of miR‑21, and the level of IL‑12 in the supernatant of THP‑1 cells transfected with miR‑21 mimic was increased. IL‑12 pretreatment increased VEGF expression and angiogenic ability in HUVECs. The inactivation of miR‑21 or activation of its target gene may be a potential therapeutic strategy in human AML.

CBX7 regulates stem cell-like properties of gastric cancer cells via p16 and AKT-NF-κB-miR-21 pathways

Background

Chromobox protein homolog 7 (CBX7), a member of the polycomb group (PcG) family of proteins, is involved in the regulation of cell proliferation and cancer progression. PcG family members, such as BMI, Mel-18, and EZH2, are integral constituents of the polycomb repressive complexes (PRCs) and have been known to regulate cancer stem cell (CSC) phenotype. However, the role of other PRCs’ constituents such as CBX7 in the regulation of CSC phenotype remains largely elusive. This study was to investigate the role of CBX7 in regulating stem cell-like properties of gastric cancer and the underlying mechanisms.

Methods

Firstly, the role of CBX7 in regulating stem cell-like properties of gastric cancer was investigated using sphere formation, Western blot, and xenograft tumor assays. Next, RNA interference and ectopic CBX7 expression were employed to determine the impact of CBX7 on the expression of CSC marker proteins and CSC characteristics. The expression of CBX7, its downstream targets, and stem cell markers were analyzed in gastric stem cell spheres, common cancer cells, and gastric cancer tissues. Finally, the pathways by which CBX7 regulates stem cell-like properties of gastric cancer were explored.

Results

We found that CBX7, a constituent of the polycomb repressive complex 1 (PRC1), plays an important role in maintaining stem cell-like characteristics of gastric cancer cells via the activation of AKT pathway and the downregulation of p16. Spearman rank correlation analysis showed positive correlations among the expression of CBX7 and phospho-AKT (pAKT), stem cell markers OCT-4, and CD133 in gastric cancer tissues. In addition, CBX7 was found to upregulate microRNA-21 (miR-21) via the activation of AKT-NF-κB pathway, and miR-21 contributes to CBX7-mediated CSC characteristics.

Conclusions

CBX7 positively regulates stem cell-like characteristics of gastric cancer cells by inhibiting p16 and activating AKT-NF-κB-miR-21 pathway.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0562-z) contains supplementary material, which is available to authorized users.

Exosomal miRNAs and miRNA dysregulation in cancer-associated fibroblasts

Purpose

The present review aimed to assess the role of exosomal miRNAs in cancer-associated fibroblasts (CAFs), normal fibroblasts (NFs), and cancer cells. The roles of exosomal miRNAs and miRNA dysregulation in CAF formation and activation were summarized.

Methods

All relevant publications were retrieved from the PubMed database, with key words such as CAFs, CAF, stromal fibroblasts, cancer-associated fibroblasts, miRNA, exosomal, exosome, and similar terms.

Results

Recent studies have revealed that CAFs, NFs, and cancer cells can secrete exosomal miRNAs to affect each other. Dysregulation of miRNAs and exosomal miRNAs influence the formation and activation of CAFs. Furthermore, miRNA dysregulation in CAFs is considered to be associated with a secretory phenotype change, tumor invasion, tumor migration and metastasis, drug resistance, and poor prognosis.

Conclusions

Finding of exosomal miRNA secretion provides novel insights into communication among CAFs, NFs, and cancer cells. MicroRNA dysregulation is also involved in the whole processes of CAF formation and function. Dysregulation of miRNAs in CAFs can affect the secretory phenotype of the latter cells.