Prostaglandin D2 regulation of autophagy affects stemness of gastric cancer stem cells

Objective:To explore the effect and mechanism of prostaglandins D2(PGD2)on the stemness of gastric cancer stem cells(GCSCs).Methods:7901-GCSCs were enriched by serum-free culture method;then the positivity rate of CD44,a stemness marker,was detected by flow cytometry in serum-free cultured 7901-GCSCs;the sphere-forming ability was detected by the sphere-forming assay after stimulation with different concentrations of PGD2(2.5,5,10)μg/mL,and the expression of stemness-related indicators(OCT4,CD44)and autophagyrelated proteins(LC3,Beclin-1)after PGD2 stimulation was detected by the western blot assay in different concentrations.The expression of stemness-related indexes(OCT4,CD44)and autophagy-related proteins(LC3,Beclin-1)were detected by Western blot assay after stimulation with different concentrations of PGD2.The expression of autophagy-related proteins after stimulation with different concentrations of CQ(2.5,5,10)μM was detected by Western blot experiment.The protein expression of autophagy-related proteins(LC3,Beclin-1)and stemness-related indexes(OCT4,CD44)was detected by Western blot experiment after PGD2 as well as PGD2+CQ treatment.Results:Flow cytometry results showed that the expression of CD44 positivity was increased in serum-free cultured 7901-GCSCs compared with gastric cancer cells SGC-7901(P<0.05),which fulfilled the needs of subsequent experiments.The results of stem cell spheroid formation assay showed that the spheroid formation ability of 7901-GCSCs in the PGD2 group was significantly weakened compared with that of the DMSO group(P<0.05).Western blot results showed that the protein expression of stemness-related indexes(OCT4,CD44)was down-regulated in the 7901-GCSCs in the PGD2 group compared with that of the DMSO group(P<0.05),and the expression of autophagy-related proteins(LC3,Beclin-1)expression increased(P<0.05).Compared with the DMSO group,the expression of autophagy-related proteins(LC3,Beclin-1)was decreased in the CQ group(P<0.05).Western blot results also showed that the expression of cellular autophagy-related proteins and stemness-related indexes in the PGD2+CQ group was not significantly changed compared with that of the DMSO group(ns:the difference was not significant),suggesting that the CQ could block the effect of PGD2 on the expression of stemness markers in 7901-GCSCs.7901-GCSCs stemness inhibition.Conclusion:PGD2 may affect the stemness of 7901-GCSCs by regulating autophagy.

Multifaceted role of microRNAs in gastric cancer stem cells: Mechanisms and potential biomarkers

MicroRNAs(miRNAs)have received much attention in the past decade as potential key epigenomic regulators of tumors and cancer stem cells(CSCs).The abnormal expression of miRNAs is responsible for different phenotypes of gastric cancer stem cells(GCSCs).Some specific miRNAs could be used as promising biomarkers and therapeutic targets for the identification of GCSCs.This review summarizes the coding process and biological functions of miRNAs and demon-strates their role and efficacy in gastric cancer(GC)metastasis,drug resistance,and apoptosis,especially in the regulatory mechanism of GCSCs.It shows that the overexpression of onco-miRNAs and silencing of tumor-suppressor miRNAs can play a role in promoting or inhibiting tumor metastasis,apart from the initial formation of GC.It also discusses the epigenetic regulation and potential clinical applications of miRNAs as well as the role of CSCs in the pathogenesis of GC.We believe that this review may help in designing novel therapeutic approaches for GC.

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-todate 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.

Therapeutic targets against gastric cancer stem cells interacting with tumor microenvironment

Gastric cancer(GC)is a major cause of cancer-related deaths worldwide.The existe nee of cancer stem cells(CSCs)is known to be the main reas on for resista nee to an ticanceragents as well as for the development of distant metastases.Although CSCs themselves harbor self-renewal and differentiation abilities,the tumor microenvironment that surrounds CSCs provides secreted factors and supports angiogenesis and is thus responsible for the maintenance of their CSC properties.The current review provides information regarding the impact of the tumor microenvironment on gastric CSCs,which will support the development of novel therapeutic strategies for targeting gastric CSCs.

Side population cells isolated from KATO Ⅲ human gastric cancer cell line have cancer stem cell-like characteristics

AIM: To investigate whether the side population (SP) cells possess cancer stem cell-like characteristics in vitro and the role of SP cells in tumorigenic process in gastric cancer. METHODS: We analyzed the presence of SP cells indifferent human gastric carcinoma cell lines, and then isolated and identified the SP cells from the KATO Ⅲ human gastric cancer cell line by flow cytometry. The clonogenic ability and self-renewal were evaluated by clone and sphere formation assays. The related genes were determined by reverse transcription polymerase chain reaction. To compare tumorigenic ability, SP and non-side population (NSP) cells from the KATO Ⅲ human gastric cancer cell line were subcutaneously injected into nude mice. RESULTS: SP cells from the total population accounted for 0.57% in KATO Ⅲ, 1.04% in Hs-746T, and 0.02% in AGS (CRL-1739). SP cells could grow clonally and have self-renewal capability in conditioned media. The expression of ABCG2, MDRI, Bmi-1 and Oct-4 was different between SP and NSP cells. However, there was no apparent difference between SP and NSP cells when they were injected into nude mice. CONCLUSION: SP cells have some cancer stem celllike characteristics in vitro and can be used for studying the tumorigenic process in gastric cancer.

Micro RNA-145 exerts tumor-suppressive and chemoresistance lowering effects by targeting CD44 in gastric cancer

AIM To determine the potential roles of CD4 and micro RNA(mi R)-145 in gastric cancer.METHODS The levels of CD44 and mi R-145 were determined in gastric cancer cells. Quantitative real-time polymerase chain reaction was used to measure to the level of CD44 m RNA. A luciferase reporter assay and western blotting were performed to examine the effect of mi R-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 mi R-145 was decreased in gastric cancer cells that were highly enriched in cancer stem cells(CSCs). The results demonstrated that mi R-145 regulated CD44 by targeting directly the CD44 3'-untranslated region(3'-UTR). In gastric cancer cells, overexpression of mi R-145 repressed the activity of the CD44 3'-UTR, and disruption of mi R-145/CD44 3'-UTR interactions abrogated the silencing effects. In addition, mi R-145 inhibition stimulated CD44 3'-UTR activity and disruption of mi R-145/CD44 3'-UTR interactions abrogated this stimulatory effect. Enforced CD44 expression greatly increased tumor sphere formation and chemoresistance in gastric cancer cells. Furthermore, the inhibition of CSCs and the chemo-sensitivity of gastric cancer cells treated with mi R-145 were significantly abrogated by overexpression of CD44. CONCLUSION mi R-145 targeting of CD44 plays critical roles in the regulation of tumor growth and chemo-resistance in gastric cancer.

Insight into the molecular mechanisms of gastric cancer stem cell in drug resistance of gastric cancer

Gastric cancer(GC)is one of the most common causes of cancer-related death worldwide,and gastric cancer stem cells(GCSCs)are considered as the major factor for resistance to conventional radio-and chemotherapy.Accumulating evidence in recent years implies that GCSCs regulate the drug resistance in GC through multiple mechanisms,including dormancy,drug trafficking,drug metabolism and targeting,apoptosis,DNA damage,epithelial-mesenchymal transition,and tumor microenvironment.In this review,we summarize current advancements regarding the relationship between GCSCs and drug resistance and evaluate the molecular bases of GCSCs in drug resistance.