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Background The interaction between tumor cells and stromal cells in tumor microenvironment is critical for cancer progression. MSCs represent a dominant source of tumor stromal cells and exert pro-oncogenic activities when reprogrammed by tumor. The precise mechanism for MSC reprogramming in gastric cancer has not been fully understood. Methods The gene and protein expression levels were examined by qRT-PCR, western blot, and immunohistochemistry. The biological functions of gastric cancer cells were detected by in vitro and in vivo experiments. RNA‐sequencing, RNA immunoprecipitation (RIP), and meRIP assays were conducted to explore the potential regulatory mechanisms. Results We identified that the expression and N6-methyladenosine (m6A) modification levels of colony stimulating factor 2 (CSF2) were significantly increased in gastric cancer MSCs. CSF2 upregulation and stimulation induced the reprogramming of normal MSCs to cancer-promoting MSCs, which promoted the proliferation, migration, and drug resistance of gastric cancer cells through the secretion of various pro-inflammatory factors. We further demonstrated that CSF2 mRNA was recognized and stabilized by m6A reader IGF2BP2, whose overexpression mimicked the effect of CSF2 on MSCs to promote gastric cancer progression. Finally, we found that CSF2 exerted the reprograming effect of MSCs by inducing the ubiquitination of Notch1. Conclusions The increased m6A modification of CSF2 by IGF2BP2 reprogrammed MSCs into a cancer-promoting phenotype. The IGF2BP2/CSF2/Notch1 axis represents a new mechanism for MSC programming in gastric cancer and offers a novel target for gastric cancer therapy.

Long non-coding RNAs (lncRNAs) have been suggested as important regulators of cancer development and progression in hepatocellular carcinoma (HCC). Nevertheless, the clinical value and biological roles of LINC00978 in HCC remain unclear. In this study, we detected the expression of LINC00978 in tumor tissues and serum of HCC patients, examined the roles of LINC00978 in HCC progression and elucidated the underlying molecular mechanisms. We found that LINC00978 expression was upregulated in tumor tissues and serum of HCC patients. Higher serum levels of LINC00978 could distinguish HCC patients from hepatitis and liver cirrhosis patients and healthy controls. LINC00978 knockdown inhibited HCC cell proliferation, migration and invasion while promoted cell cycle arrest and apoptosis. Overexpression of LINC00978 led to the opposite effects. LINC00978 knockdown also inhibited HCC growth and metastasis in mouse tumor models. Mechanistically, LINC00978 bound to EZH2 and mediated its accumulation at the promoter region of p21 and E-cadherin genes, leading to the trimethylation of H27K3 and the inhibition of p21 and E-cadherin expression. Moreover, the simultaneous depletion of p21 and E-cadherin expression reversed the inhibitory effects of LINC00978 knockdown on HCC cell proliferation, migration, and invasion. Taken together, these findings suggest that LINC00978 promotes HCC progression by inhibiting p21 and E-cadherin expression via EZH2-mediated epigenetic silencing. LINC00978 may represent a novel biomarker for HCC diagnosis, prognosis, and therapy.

Chemoresistance is one of the causes associated with poor prognosis in gastric cancer. MicroRNAs (miRNAs) are important regulators of chemoresistance. Exosome-mediated delivery of anti-cancer molecules and drugs have emerged as a new approach for cancer therapy. We first examined the expression of miR-374a-5p in gastric cancer serum by qRT-PCR and explored the clinicopathological parameters. We then performed in vitro cell and molecular studies, including CCK-8 assay, flow cytometry, qRT-PCR, and western blot, to determine the roles of miR-374a-5p in gastric cancer chemoresistance and identified its downstream target by luciferase reporter assay. We also used in vivo animal studies to evaluate the therapeutic efficacy of miR-374a-5p inhibitor and exosome-mediated delivery of miR-374a-5p inhibitor in gastric cancer. miR-374a-5p expression level was elevated in gastric cancer serum, and its upregulation predicted poor prognosis. miR-374a-5p overexpression promoted while miR-374a-5p knockdown inhibited gastric cancer chemoresistance in vitro and in vivo. miR-374a-5p bound to Neurod1 to antagonize its effect on chemoresistance. Exosome-mediated delivery of miR-374a-5p inhibitor could increase Neurod1 expression, promote cell apoptosis, and suppress chemoresistance. miR-374a-5p had a promoting role in gastric cancer chemoresistance, which would provide a novel biomarker for gastric cancer diagnosis and prognosis and offer a potential target for gastric cancer drug resistance therapy. Keywords: miR-374a-5p, chemoresistance, gastric cancer, exosome

MircoRNA-335 (miR-335) has been reported as a significant cancer-associated microRNA, which was often epigenetically silenced and acted as a tumor suppressor gene in diverse human solid tumors. Conversely, recent studies show that miR-335 overexpression was identified in both adult and pediatric acute myeloid leukemia (AML), suggesting that it might play an oncogenic role of miR-335 in AML. However, the role of miR-335 during leukemogenesis remains to be elucidated. MiR-335/ID4 expression was detected by real-time quantitative PCR and/or western blot. Survival analysis was performed to explore the association between miR-335/ID4 expression and the prognosis, and further validated by public databases. Gain-of-function experiments determined by cell proliferation, apoptosis, and differentiation were conducted to investigate the biological functions of miR-335/ID4. Herein, we found that miR-335 expression, independent of its methylation, was significantly increased and negatively correlated with reduced ID4 expression in AML. Moreover, aberrant miR-335/ID4 expression independently affected chemotherapy response and leukemia-free/overall survival in patients with AML. Gain-of-function experiments in vitro showed the oncogenic role of miR-335 by affecting cell apoptosis and proliferation in AML, and could be rescued by ID4 restoration. Mechanistically, we identified and verified that miR-335/ID4 contributed to leukemogenesis through activating PI3K/Akt signaling pathway. Collectively, aberrant miR-335/ID4 expression was an independent prognostic biomarker in AML. MiR-335/ID4 dysregulation facilitated leukemogenesis through the activation of PI3K/Akt signaling pathway.

The clinical activity of decitabine (5‐aza‐2‐deoxycytidine, DAC), a hypomethylating agent, has been demonstrated in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients. However, secondary resistance to this agent often occurs during treatment and leads to treatment failure. It is important to clarify the mechanisms underlying the resistance for improving the efficacy. In this study, by gradually increasing concentration after a continuous induction of DAC, we established the DAC‐resistant K562 cell line (K562/DAC) from its parental cell line K562. The proliferation and survival rate of K562/DAC was significantly increased, whereas the apoptosis rate was remarkably decreased than that of K562 after DAC treatment. In K562/DAC, a total of 108 genes were upregulated and 118 genes were downregulated by RNA‐Seq. In addition, we also observed aberrant expression of DDX43/H19/miR‐186 axis (increased DDX43/H19 and decreased miR‐186) in K562/DAC cells. Ectopic expression of DDX43 in parental K562 cells rendered cells resistant to the DAC. Taken together, we successfully established DAC‐resistant K562 cell line which can serve as a good model for investigating DAC resistance mechanisms, and DDX43/H19/miR‐186 may be involved in DAC resistance in K562.

Additional file 1:Table S1. Sequences of shRNA and siRNA

Additional file 2: Table S2. Sequences of PCR primers for target gene detection

Deregulated expression of chemokines in tumor microenvironment contributes to tumor metastasis by targeting distinct cells. Epithelial-derived neutrophil-activating peptide-78 (ENA78/CXCL5) is upregulated in many cancers and involved in tumor progression. The role and underlying mechanism of CXCL5 in gastric cancer (GC) metastasis remain unclear. In this study, we reported that the expression of CXCL5 was elevated in tumor tissues and positively associated with lymphatic metastasis and tumor differentiation. Stimulation by recombinant human CXCL5 (rhCXCL5) induced epithelial-mesenchymal transition (EMT) in GC cells through the activation of ERK pathway, which enhanced their migration and invasion abilities. The culture supernatant from tumor tissues also enhanced the migration and invasion abilities of GC cells, however, this effect was reversed by pre-treatment with CXCL5 neutralizing antibody. Further studies showed that rhCXCL5 could induce the expression of IL-6 and IL-23 in neutrophils through the activation of ERK and p38 signaling pathways, which in turn facilitated GC cell migration and invasion. The culture supernatant from tumor tissues showed similar effects on neutrophils in a CXCL5-dependent manner. Blockade of IL-6 and IL-23 with neutralizing antibodies reversed the induction of EMT and the increased migration and invasion abilities in GC cells by CXCL5-activated neutrophils. Moreover, CXCL5 activated neutrophils could promote gastric cancer metastasis in vivo. Taken together, our results indicate that CXCL5 acts on gastric cancer cells to induce EMT and mediates pro-tumor activation of neutrophils, which synergistically promotes the metastatic ability of GC cells.

Mesenchymal stem cells (MSCs) are a critical component of the tumor microenvironment. Upon distinct pathological stimulus, MSCs show phenotypic and functional changes. Gastric cancer is one of the leading causes of cancer-related deaths worldwide. The roles and mechanisms of MSCs in gastric cancer have not been well characterized. In the present study, we investigated the roles of MSCs in the malignant transformation from gastritis to gastric cancer using an N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer model. We isolated MSCs from the gastric tissues of normal (RGN-MSCs) and MNNG-exposed rats (RGI-MSCs), and compared the biological properties of RGI-MSCs with RGN-MSCs. We found that RGI-MSCs had increased proliferative and migratory capabilities than these capacities noted in the RGN-MSCs. In addition, RGI-MSCs produced higher levels of IL-6, CXCL10 and MCP-1 than RGN-MSCs. Moreover, RGI-MSCs promoted the migration of normal gastric mucosa epithelial cells by inducing epithelial-mesenchymal transition (EMT). The upregulation of miR-374 in RGI-MSCs was partially responsible for their increased proliferative and migratory capabilities. Collectively, our findings provide new evidence for the roles of MSCs in gastric carcinogenesis, suggesting that targeting gastric cancer-associated MSCs may represent a novel avenue for gastric cancer therapy.

Background Leukemia stem cell (LSC)-enriched genes have been shown to be highly prognostic in acute myeloid leukemia (AML). However, the prognostic value of tumor suppressor genes (TSGs) that are repressed early in LSC remains largely unknown. Methods We compared the public available expression/methylation profiling data of LSCs with that of hematopoietic stem cells (HSCs), in order to identify potential tumor suppressor genes in LSC. The prognostic relevance of PCDH17 was analyzed on a cohort of 173 AML patients from The Cancer Genome Atlas (TCGA), and further validated in three independent cohorts (n = 339). Results We identified protocadherin17 (PCDH17) and demonstrated that it was significantly down-regulated and hypermethylated in LSCs compared with HSCs. Our analyses of primary AML patient samples also confirmed these deregulations. Clinically, low PCDH17 expression was associated with female sex (P = 0.01), higher WBC (P

Emerging evidence has revealed that neutrophils have phenotypic and functional plasticity. Neutrophils could be polarized towards a pro-tumor phenotype by tumor-derived factors. In the present study, we investigated the role of the interaction with neutrophils on the functions of gastric cancer cells in vitro. Human promyelocytic leukemia HL-60 cells were induced to differentiate into neutrophil-like cells (HL-60N) using dimethyl sulfoxide (DMSO). Human gastric cancer cells were co-cultured with HL-60N cells or treated with the conditioned medium (CM) of cancer-activated HL-60N cells. The migration and invasion of gastric cancer cells were significantly enhanced while their proliferation was minimally altered. The expression of pro-inflammatory factors including IL-6, IL-8, IL-1β, and TNFα was significantly increased in cancer-activated HL-60N cells, which induced the activation of the ERK pathway and epithelial-mesenchymal transition (EMT) in gastric cancer cells. Blocking the ERK pathway activation reversed the promoting effects of cancer-activated HL-60N cells on gastric cancer cell migration and invasion. In addition, mouse gastric cancer cell derived CM could also increase the expression of pro-inflammatory factors in mouse bone marrow neutrophils, which in turn enhanced the migration and invasion of mouse gastric cancer cells. Collectively, our findings revealed that the interaction with neutrophils promoted gastric cancer cell migration and invasion through the activation of the ERK pathway and the induction of EMT, indicating that neutrophils may play an important role in gastric cancer metastasis. Therefore, targeting neutrophil-cancer cell interaction may provide a new strategy for the treatment of gastric cancer.

Mesenchymal stem cells (MSCs) are a component of the tumor microenvironment and can promote the development of gastric cancer through paracrine mechanism. However, the effects of MSC‑exosomes (MSC‑ex) on gastric cancer are less clear. The present study reported that MSC‑ex promoted the proliferative and metastatic potential of gastric cancer cells ex vivo. It was found that MSC‑ex enhanced the migration and invasion of HGC‑27 cells via the induction of the epithelial‑mesenchymal transition. MSC‑ex increased the expression of mesenchymal markers and reduced the expression of epithelial markers in gastric cancer cells. MSC‑ex also enhanced the tumorigenicity of gastric cancer cells ex vivo. MSC‑ex induced the stemness of gastric cancer cells. The expression of octamer‑binding transcription factor 4, ex determining region Y‑box 2 and Lin28B significantly increased in gastric cancer cells treated with MSC‑ex. The present study further demonstrated that MSC‑ex elicited these biological effects predominantly via the activation of the protein kinase B signaling pathway. Taken together, the present findings provided novel evidence for the role of MSC‑ex in gastric cancer and a new opportunity for improving the efficiency of gastric cancer treatment by targeting MSC‑ex.

Mesenchymal stem cells (MSCs) play an important role in chemoresistance. Exosomes have been reported to modify cellular phenotype and function by mediating cell-cell communication. In this study, we aimed to investigate whether exosomes derived from MSCs (MSC-exosomes) are involved in mediating the resistance to chemotherapy in gastric cancer and to explore the underlying molecular mechanism. We found that MSC-exosomes significantly induced the resistance of gastric cancer cells to 5-fluorouracil both in vivo and ex vivo. MSC-exosomes antagonized 5-fluorouracil-induced apoptosis and enhanced the expression of multi-drug resistance associated proteins, including MDR, MRP and LRP. Mechanistically, MSC-exosomes triggered the activation of calcium/calmodulin-dependent protein kinases (CaM-Ks) and Raf/MEK/ERK kinase cascade in gastric cancer cells. Blocking the CaM-Ks/Raf/MEK/ERK pathway inhibited the promoting role of MSC-exosomes in chemoresistance. Collectively, MSC-exosomes could induce drug resistance in gastric cancer cells by activating CaM-Ks/Raf/MEK/ERK pathway. Our findings suggest that MSC-exosomes have profound effects on modifying gastric cancer cells in the development of drug resistance. Targeting the interaction between MSC-exosomes and cancer cells may help improve the efficacy of chemotherapy in gastric cancer.

Background GTPase regulator associated with the focal adhesion kinase (GRAF), a putative tumor suppressor gene, is found inactivated in hematopoietic malignancies by either genetic or epigenetic abnormalities. However, the expression level of GRAF gene has not yet been studied in leukemia. The aim of this study was to investigate the expression level of GRAF gene in those patients with myeloid malignancies including acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and chronic myeloid leukemia (CML). Methods The expression levels of GRAF transcript were determined in 94 patients using real-time quantitative PCR (RQ-PCR). Clinical and laboratory data of these patients were collected and analyzed. Results The significantly decreased level of GRAF transcript was observed in three myeloid malignancies compared to controls. Within AML, there was no difference in the level of GRAF transcript among different FAB subtypes (P > 0.05). Difference was not observed in the amount of GRAF mRNA between CML at chronic phase and controls. As CML progressed, GRAF transcript significantly decreased. In MDS, three cases with 5q deletion had lower GRAF transcript than four without 5q deletion (median 0.76 vs 2.99) (P > 0.05). Conclusion our results demonstrate that the GRAF transcript is decreased in myeloid malignancies.