Methylated lncRNAs suppress apoptosis of gastric cancer stem cells via the lncRNA-miRNA/protein axis

BACKGROUND

Long noncoding RNAs (lncRNAs) play essential roles in the tumorigenesis of gastric cancer. However, the influence of lncRNA methylation on gastric cancer stem cells (GCSCs) remains unclear.

METHODS

The N6-methyladenosine (m6A) levels of lncRNAs in gastric cancer stem cells were detected by methylated RNA immunoprecipitation sequencing (MeRIP-seq), and the results were validated by MeRIP-quantitative polymerase chain reaction (qPCR). Specific sites of m6A modification on lncRNAs were detected by single-base elongation- and ligation-based qPCR amplification (SELECT). By constructing and transfecting the plasmid expressing methyltransferase-like 3 (METTL3) fused with catalytically inactivated Cas13 (dCas13b) and guide RNA targeting specific methylation sites of lncRNAs, we obtained gastric cancer stem cells with site-specific methylation of lncRNAs. Reverse transcription (RT)-qPCR and Western blot were used for detecting the stemness of treated gastric cancer stem cells.

RESULTS

The site-specific methylation of PSMA3-AS1 and MIR22HG suppressed apoptosis and promoted stemness of GCSCs. LncRNA methylation enhanced the stability of PSMA3-AS1 and MIR22HG to suppress apoptosis of GCSCs via the PSMA3-AS1-miR-411-3p- or MIR22HG-miR-24-3p-SERTAD1 axis. Simultaneously, the methylated lncRNAs promoted the interaction between PSMA3-AS1 and the EEF1A1 protein or MIR22HG and the LRPPRC protein, stabilizing the proteins and leading to the suppression of apoptosis. The in vivo data revealed that the methylated PSMA3-AS1 and MIR22HG triggered tumorigenesis of GCSCs.

CONCLUSIONS

Our study revealed the requirement for site-specific methylation of lncRNAs in the tumorigenesis of GCSCs, contributing novel insights into cancer development.

Formulation and characterization of cisplatin-loaded hydroxyl functionalized single-walled carbon nanotubes for targeting gastric cancer stem cells

Chemotherapy is the most commonly used therapeutic method for treating many malignancies including gastric cancer. Due to their non-specific and non-targeted drug delivery, it causes resistance leading to cancer progression, relapse, and metastasis of cancer. To overcome this problem we carried out a study aimed to develop a new cisplatin (Cisp) loaded hydroxyl functionalized single-walled carbon nanotube (OH-SWCNT) nanocarrier system to selectively eliminate gastric cancer stem cells. To our understanding, this is the first study of the non-covalent interaction of cisplatin loaded on the surface of hydroxyl-functionalized single-walled carbon nanotubes by ultrasonication. The physical and morphological characterization was carried out by UV-Vis, FTIR spectroscopy, and TEM. A sustained and controlled release of cisp from OH-SWCNT at all three pHs 3.5, 5.5, and 7.4 was observed. Gastric cancer stem cells were isolated from primary cells and were identified by using CD133+ and CD44+ specific markers. Cisplatin-loaded OH-SWCNT nanocarrier was capable of limiting the self-renewal capacity of both CD133+ and CD44+ populations and also decreasing the number of tumorspheres in gastric CSCs. The cell viability percent of AGS cells was 20% at 250 μg/ml concentration. The IC50 value was less than 50% mol/L at both 200 μg/ml and 250 μg/ml of cisplatin-loaded OH-SWCNT. Our findings suggest that cisplatin-loaded OH-SWCNT nanocarrier complexes could target gastric CSCs and also could provide a potential strategy for selectively targeting and efficiently eliminating gastric CSCs. This could be a promising approach to prevent gastric cancer recurrence and metastasis and also improve gastric cancer therapy.

B-cell-specific Moloney murine leukemia virus integration site 1 knockdown impairs adriamycin resistance of gastric cancer cells

BACKGROUND AND STUDY AIMS

The B-cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) is associated with the progression of gastric cancer (GC). However, its role in drug resistance of gastric cancer stem cell (GCSC) remains unclear. This study aimed to explore the biological function of BMI-1 in GC cells and its role in drug resistance of GCSCs.

PATIENTS AND METHODS

We assessed BMI-1 expression in the GEPIA database and in our collected samples from patients with GC. We silenced BMI-1 using siRNA to study the cell proliferation and migration of GC cells. We also used Hoechst 33342 staining to verify the effect of adriamycin (ADR) on side population (SP) cells, and measured the effects of BMI-1 on the expression of N-cadherin, E-cadherin, and drug-resistance-related proteins (multidrug resistance mutation 1 and lung resistance-related protein). Finally, we analyzed BMI-1-related proteins uing the STRING and GEPIA databases.

RESULTS

BMI-1 mRNA was upregulated in GC tissues and cell lines, especially in MKN-45 and HGC-27 cells. Silencing BMI-1 reduced the proliferation and migration of GC cells. Knocking down BMI-1 significantly decreased epithelial-mesenchymal transition progression, expression levels of drug-resistant proteins, and the number of SP cells in ADR-treated GC cells. Bioinformatics analysis showed that EZH2, CBX8, CBX4, and SUZ12 were positively correlated with BMI-1 in GC tissues.

CONCLUSION

Our study demonstrates that BMI-1 affects the cellular activity, proliferation, migration, and invasion of GC cells. Silencing the BMI-1 gene significantly reduces the number of SP cells and the expression of drug-resistant proteins in ADR-treated GC cells. We speculate that inhibition of BMI-1 increases the drug resistance of GC cells by affecting GCSCs, and that EZH2, CBX8, CBX4, and SUZ12 may participate in BMI-1-induced enhancement of GCSC-like phenotype and viability.

Gastric cancer stem cell-derived exosomes promoted tobacco smoke-triggered development of gastric cancer by inducing the expression of circ670

As one of the most common malignant cancers in the world, gastric cancer is caused by mang factors among which tobacco smoke is an important risk factor. Gastric cancer stem cells (GCSCs) and the derived exosomes play a key role in the occurrence and development of gastric cancer, and exosomal circRNA is considered as a new regulatory factor in the development of gastric cancer. However, it is unclear whether tobacco smoke can affect exosomes and their transport circRNAs to promote the development of gastric cancer. Herein, we provided a new insight into tobacco smoke promoting the progression of gastric cancer. In the present study, we demonstrated that tobacco smoke-induced exosomes promoted the spheroidizing ability, stemness genes expression, and epithelial-mesenchymal transition (EMT) process of GCSCs. We further found that hsa-circRNA-000670 (circ670) was up-regulated in tissues of gastric cancer patients with smoking history, tobacco smoke-induced GCSCs, and their exosomes. Functional assays have shown that circ670 knockdown inhibited the stemness and EMT process of GCSCs, whereas circ670 overexpression appeared to have an opposite effect. Our findings indicated that exosomal circ670 promotes the development of tobacco smoke-induced gastric cancer, which may provide insight into the mechanism of tobacco smoke promoting the progression of gastric cancer.

Molecular mechanism of therapeutic approaches for human gastric cancer stem cells

Gastric cancer (GC) is a primary cause of cancer-related mortality worldwide, and even after therapeutic gastrectomy, survival rates remain poor. The presence of gastric cancer stem cells (GCSCs) is thought to be the major reason for resistance to anticancer treatment (chemotherapy or radiotherapy), and for the development of tumor recurrence, epithelial–mesenchymal transition, and metastases. Additionally, GCSCs have the capacity for self-renewal, differentiation, and tumor initiation. They also synthesize antiapoptotic factors, demonstrate higher performance of drug efflux pumps, and display cell plasticity abilities. Moreover, the tumor microenvironment (TME; tumor niche) that surrounds GCSCs contains secreted growth factors and supports angiogenesis and is thus responsible for the maintenance of the growing tumor. However, the genesis of GCSCs is unclear and exploration of the source of GCSCs is essential. In this review, we provide up-to-date information about GCSC-surface/intracellular markers and GCSC-mediated pathways and their role in tumor development. This information will support improved diagnosis, novel therapeutic approaches, and better prognosis using GCSC-targeting agents as a potentially effective treatment choice following surgical resection or in combination with chemotherapy and radiotherapy. To date, most anti-GCSC blockers when used alone have been reported as unsatisfactory anticancer agents. However, when used in combination with adjuvant therapy, treatment can improve. By providing insights into the molecular mechanisms of GCSCs associated with tumors in GC, the aim is to optimize anti-GCSCs molecular approaches for GC therapy in combination with chemotherapy, radiotherapy, or other adjuvant treatment.

Distinct biological characterization of the CD44 and CD90 phenotypes of cancer stem cells in gastric cancer cell lines

Recent study implicates that gastric cancer stem cells (CSCs) are capable of generating multiple types of cells to promote tumor growth and heterogeneity important for the development of gastric cancer. However, knowledge is limited regarding the expression and characteristics of marker-positive gastric CSCs. Therefore, gastric CSCs from a series of human gastric cancer cell lines (SNU-5, SNU-16, BGC-823, PAMC-82, MKN-45, and NCI-N87) using four putative CSC surface markers (CD44, CD90, CD133, and epithelial-cell adhesion molecule) were investigated the underlying mechanisms regulating such subpopulations. Only SNU-5 and SNU-16 exhibited independent co-expression of CD44⁺ and CD90⁺, which exhibited spheroid-colony formation in vitro and tumor formation in immunodeficient mice. Functional studies revealed that CD44⁺ cells were more invasive compared with CD90⁺ cells, whereas CD90⁺ cells exhibited higher levels of proliferation than CD44⁺ cells. Furthermore, serial xenotransplantation in mice of CD44⁺/CD90⁺ cells derived from SNU-5 and SNU-16 revealed rapid growth of CD90⁺ cells in subcutaneous lesions and a high metastatic capacity of CD44⁺ cells in the lung. Mechanistic analyses revealed that CD44⁺ cells underwent epithelial-to-mesenchymal transition (EMT) following acquisition of mesenchymal features, whereas CD90⁺ cells enhanced the activation of retinoblastoma phosphorylation at Ser780 and oncogenic cell cycle regulators. The expression of CD44 and CD90 in gastric cancer tissues was associated with distant metastasis and the differentiation state of tumors. These results demonstrated that CD44 and CD90 are specific biomarkers capable of identifying and isolating metastatic and tumorigenic CSCs through their ability to regulate EMT and the cell cycle in gastric cancer cell lines.

Hyaluronic acid-modified polyamidoamine dendrimer G5-entrapped gold nanoparticles delivering METase gene inhibits gastric tumor growth via targeting CD44+ gastric cancer cells

BACKGROUND

Gastric cancer (GC) is the second most common leading cause of cancer-related death. Cancer stem cell (CSC) with the mark of CD44 played an important role in GC. rMETase was wildly exploited as chemotherapeutic option for GC. Polymers synthetic nanoparticle drug delivery systems have been commonly used for cancer therapy. With the decorating of Hyaluronic acid (HA), a receptor of CD44, nanoparticles exhibit with good biocompatibility and aqueous solubility.

METHODS

The characteristic of nanoparticles (NPs) was analyzed by TEM and DLS. The viability and proliferation of GC cells were examined by MTT assays. The levels of CD44, Cyt C, and c-caspase 3 were examined by Western blot. The level of ROS was measured by DCFH-DA assays. The morphology of tissues was detected using hematoxylin-eosin (H&E) stain. Nude mice xenograft models were used to evaluate the effect of HA-PAMAM-Au-METase on GC.

RESULTS

The transfection of rMETase carried by HA-G5 PAMAM-Au visibly inhibited the proliferation and tumorsphere formation of GC cells through obviously enhancing METase activity. Elevation of METase activity suppressed the proliferation of CD44(+) GC cells through down-regulating MET in cellular supernatant that resulted in the increase of Cyc C and ROS levels. The number of CD44(+) GC cells in nude mice injected with G5 PAMAM-Au-METase decorated by HA was markly declined resulting in the inhibition of tumor growth.

CONCLUSION

HA-G5 PAMAM-Au-METase significantly suppressed tumor growth of GC by targeted damaging the mitochondrial function of CD44(+) gastric CSCs.

MicroRNA-145 exerts tumor-suppressive and chemo-resistance lowering effects by targeting CD44 in gastric cancer

AIM

To determine the potential roles of CD4 and microRNA (miR)-145 in gastric cancer.

METHODS

The levels of CD44 and miR-145 were determined in gastric cancer cells. Quantitative real-time polymerase chain reaction was used to measure to the level of CD44 mRNA. A luciferase reporter assay and western blotting were performed to examine the effect of miR-145 on CD44 expression. Tumor sphere and MTT assays were carried out to evaluate the self-renewal and chemo-resistance properties of gastric cancer cells.

RESULTS

The expression of CD44 was greatly increased and miR-145 was decreased in gastric cancer cells that were highly enriched in cancer stem cells (CSCs). The results demonstrated that miR-145 regulated CD44 by targeting directly the CD44 3’-untranslated region (3’-UTR). In gastric cancer cells, overexpression of miR-145 repressed the activity of the CD44 3’-UTR, and disruption of miR-145/CD44 3’-UTR interactions abrogated the silencing effects. In addition, miR-145 inhibition stimulated CD44 3’-UTR activity and disruption of miR-145/CD44 3’-UTR interactions abrogated this stimulatory effect. Enforced CD44 expression greatly increased tumor sphere formation and chemo-resistance in gastric cancer cells. Furthermore, the inhibition of CSCs and the chemo-sensitivity of gastric cancer cells treated with miR-145 were significantly abrogated by overexpression of CD44.

CONCLUSION

miR-145 targeting of CD44 plays critical roles in the regulation of tumor growth and chemo-resistance in gastric cancer.

Role of Helicobacter pylori infection in generation of gastric cancer stem cells

Helicobacter pylori (H. pylori) is a key cause of gastric cancer, and gastric cancer stem cells play an important role in the development of gastric cancer. Therefore in this paper, we try to explore the relationship between H. pylori infection and stem cells in gastric cancer. H. pylori infection promotes the generation of gastric cancer stem cells through the epithelial-mesenchymal transition (EMT). In addition, H. pylori participates in the processes of the formation and progression of gastric cancer stem cells by affecting related signal pathways, such as Wnt/β-catenin, Hh/SHH, Notch, FGF/BMP. On this basis, we disscuss the challenges and future directions in the research of H. pylori infection and gastric cancer stem cells.

Notch signaling pathway and gastric cancer

Gastric cancer is still the second leading cause of cancer-related death. Currently, all the available therapeutic methods in practice appear to be blunt for the majority of advanced-stage patients and their long time-survival rate is also still rather frustrating. The Notch signaling pathway is increasingly demonstrated to play an important role in controlling the fate of gastric cancer cells and gastric cancer stem cells, and some previous studies have indicated that different Notch receptors and ligands, such as Notch-1, 2, 3, Dll-1, 4 and Jag-1, 2, were highly expressed in gastric cancer tissues and were associated with various clinical parameters. More notably, these receptors and ligands were also found to be expressed in gastric cancer stem cells, which were CD44 positive, and could have a key role in regulating the fate of these cells. Taking into consideration the pivotal role of Notch signaling pathway in gastric cancer and cancer stem cells, it would be promising to predict that it could become therapeutic targets in the future.

The effect of hyaluronic acid functionalized carbon nanotubes loaded with salinomycin on gastric cancer stem cells

Gastric cancer stem cells (CSCs) play a crucial role in the initiation, development, relapse and metastasis of gastric cancer because they are resistant to a standard chemotherapy and the residual CSCs are able to proliferate indefinitely. Therefore, eradication of this cell population is a primary objective in gastric cancer therapy. Here, we report a gastric CSCs-specifically targeting drug delivery system (SAL-SWNT-CHI-HA complexes) based on chitosan(CHI) coated single wall carbon nanotubes (SWNTs) loaded with salinomycin (SAL) functionalized with hyaluronic acid (HA) can selectively eliminate gastric CSCs. Gastric CSCs were identified as CD44+ cells and cultured in serum-free medium. SAL-SWNT-CHI-HA complexes were capable of inhibiting the self-renewal capacity of CD44+ population, and decrease mammosphere- and colon-formation of CSCs. In addition, the migration and invasion of gastric CSCs were significantly blocked by SAL-SWNT-CHI-HA complexes. Quantitative and qualitative analysis of cellular uptake demonstrated that HA functionalization facilitated the uptake of SWNTs in gastric CSCs while free HA competitively inhibited cellular uptake of SAL-SWNT-CHI-HA delivery system, revealing the mechanism of CD44 receptor-mediated endocytosis. The SAL-SWNT-CHI-HA complexes showed the strongest antitumor efficacy in gastric CSCs by inducing apoptosis, and in CSCs mammospheres by penetrating deeply into the core. Taken altogether, our studies demonstrated that this gastric CSCs-targeted SAL-SWNT-CHI-HA complexes would provide a potential strategy to selectively target and efficiently eradicate gastric CSCs, which is promising to overcome the recurrence and metastasis of gastric cancer and improve gastric cancer treatment.

Recent advances in research of gastric cancer stem cells

Gastric cancer is a common malignancy of the digestive tract that has a high mortality and seriously affects people's health. At present, the pathogenesis of gastric cancer is still unclear. According to the cancer stem cell theory, cancer stem cells are malignant cells with the characteristics of normal stem cells, probably formed by the mutation of normal stem cells. Tumor stem cells have been identified in a variety of solid tumors. Recent studies have shown that the location of gastric cancer is consistent with the settlement area of stem cells, indicating that gastric cancer may be a kind of stem cells disease. In this article we will review the existence, origin, identification and separation of cancer stem cells.