mPGES-1/PGE2 promotes the growth of T-ALL cells in vitro and in vivo by regulating the expression of MTDH via the EP3/cAMP/PKA/CREB pathway

cAMP-PKA/EPAC signaling and cancer: the interplay in tumor microenvironment

Cancer is a complex disease resulting from abnormal cell growth that is induced by a number of genetic and environmental factors. The tumor microenvironment (TME), which involves extracellular matrix, cancer-associated fibroblasts (CAF), tumor-infiltrating immune cells and angiogenesis, plays a critical role in tumor progression. Cyclic adenosine monophosphate (cAMP) is a second messenger that has pleiotropic effects on the TME. The downstream effectors of cAMP include cAMP-dependent protein kinase (PKA), exchange protein activated by cAMP (EPAC) and ion channels. While cAMP can activate PKA or EPAC and promote cancer cell growth, it can also inhibit cell proliferation and survival in context- and cancer type-dependent manner. Tumor-associated stromal cells, such as CAF and immune cells, can release cytokines and growth factors that either stimulate or inhibit cAMP production within the TME. Recent studies have shown that targeting cAMP signaling in the TME has therapeutic benefits in cancer. Small-molecule agents that inhibit adenylate cyclase and PKA have been shown to inhibit tumor growth. In addition, cAMP-elevating agents, such as forskolin, can not only induce cancer cell death, but also directly inhibit cell proliferation in some cancer types. In this review, we summarize current understanding of cAMP signaling in cancer biology and immunology and discuss the basis for its context-dependent dual role in oncogenesis. Understanding the precise mechanisms by which cAMP and the TME interact in cancer will be critical for the development of effective therapies. Future studies aimed at investigating the cAMP-cancer axis and its regulation in the TME may provide new insights into the underlying mechanisms of tumorigenesis and lead to the development of novel therapeutic strategies.

Long noncoding RNA SENCR facilitates the progression of acute myeloid leukemia through the miR-4731-5p/IRF2 pathway

BACKGROUND

Acute myeloid leukemia (AML) is a type of hematological tumor caused by malignant clone hematopoietic stem cells. The relationship between lncRNAs and tumor occurrence and progression has been gaining attention. Research has shown that Smooth muscle and endothelial cell-enriched migration/differentiation-associated lncRNA (SENCR) is abnormally expressed in various diseases, whereas its role in AML is still poorly understood.

METHODS

The expression of SENCR, microRNA-4731-5p (miR-4731-5p) and Interferon regulatory factor 2 (IRF2) were measured using qRT-PCR. The proliferation, cycle and apoptosis of AML cells with or without knockdown of SENCR were detected by CCK-8 assay, EdU assay, flow cytometry, western blotting and TUNEL assay, respectively. Consistently, SENCR knockdown was impaired the AML progression in immunodeficient mice. In addition, the binding of miR-4731-5p to SENCR or IRF2 was confirmed by luciferase reporter genes assay. Finally, rescue experiments were conducted to confirm the role of SENCR/miR-4731-5p/IRF2 axis in AML.

RESULTS

SENCR is highly expressed in AML patients and cell lines. The patients with high SENCR expression had poorer prognosis compared with those with low SENCR expression. Interestingly, knockdown of SENCR inhibits the growth of AML cells. Further results demonstrated that the reduction of SENCR slows the progression of AML in vivo. SENCR could function as a competing endogenous RNA (ceRNA) to negatively regulate miR-4731-5p in AML cells. Furthermore, IRF2 was validated as a direct target gene of miR-4731-5p in AML cells.

CONCLUSIONS

Our findings underscore the important role of SENCR in regulating the malignant phenotype of AML cells by targeting the miR-4731-5p/IRF2 axis.

Prognostic and therapeutic significance of XPO1 in T-cell lymphoma

T-cell lymphoma (TCL) is a highly heterogeneous group of invasive non-Hodgkin lymphoma with adverse prognosis and limited treatment options. The relationship between TCL and Exportin-1 (XPO1), a major nuclear export receptor, has not been established yet. We here investigated the prognostic role and therapeutic implication of XPO1 in TCL. We analyzed XPO1 expression in a cohort of 69 TCL tumors and found that XPO1 was over-expressed in 76.8% of TCL and correlated with decreased progression-free survival (PFS) and overall survival (OS). In vitro treatment of TCL cell lines with KPT-8602, the second-generation selective inhibitor of nuclear export (SINE), inhibited XPO1 expression and showed significant anti-proliferative, cell-cycle arrest and pro-apoptotic efficacy. In mechanism, KPT-8602 restored the localization of cytoplasmic FOXO3A, p27, p21, IκBα and PP2A into the nucleus, leading to AKT and NF-κB deactivation. Our data demonstrate for the first time that XPO1 could be an unfavorable prognostic factor for TCL, and provide a rationale for further investigation of the efficacy of KPT-8602 in TCL patients.

MTDH Promotes Intestinal Inflammation by Positively Regulating TLR Signalling

Macrophages in the intestinal mucosa can rapidly engage Toll-like receptor [TLR]-mediated inflammatory responses to protect against pathogen invasion, but these same innate immune responses can also drive the induction of colitis. Our previous research revealed that metadherin [MTDH] is overexpressed in multiple cancers and plays vital roles in tumour progression. However, the role of MTDH in intestinal inflammation is largely unknown. In this study, we found the MTDH expression in colonic lamina propria [CLP] macrophages was positively correlated with inflammatory colitis severity. MTDH-/- mice were protected against the symptoms of dextran sodium sulphate [DSS]-induced colitis; however, adoptive transfer of MTDH wild-type [WT] monocytes partially restored the susceptibility of MTDH-/- mice to DSS-induced colitis. TLR stimulation was sufficient to induce the expression of MTDH, whereas the absence of MTDH was sufficient to suppress TLR-induced production of inflammatory cytokines by macrophages. From a mechanistic perspective, MTDH recruited TRAF6 to TAK1, leading to TRAF6-mediated TAK1 K63 ubiquitination and phosphorylation, ultimately facilitating TLR-induced NF-κB and MAPK signalling. Taken together, our results indicate that MTDH contributes to colitis development by promoting TLR-induced pro-inflammatory cytokine production in CLP macrophages and might represent a potential therapeutic approach for intestine inflammation intervention.

Construction and Evaluation of Short Hairpin RNAs for Knockdown of Metadherin mRNA

BACKGROUND

Short hairpin RNA (shRNA) has proven to be a powerful tool to study genes' function through RNA interference mechanism. Three different methods have been used in previous studies to produce shRNA expression vectors including oligonucleotide-based cloning, polymerase chain reaction (PCR)-based cloning, and primer extension PCR approaches. The aim of this study was designing a reliable and simple method according to the primer extension strategy for constructing four shRNA vectors in order to target different regions of Metadherin (MTDH) mRNA in human leukemic cell line Jurkat.

METHODS

Oligonucleotides for construction of four shRNA vectors were designed, synthesized and fused to U6 promoter. Each U6-shRNA cassette was cloned into a pGFP-V-RS vector. MTDH shRNAs were transfected into the Jurkat cell line by using the electroporation method. The ability of shRNAs to knock down MTDH mRNA was analyzed through qRT-PCR. Apoptosis assay was used to evaluate the effect of down regulation of MTDH expression on cell integrity.

RESULTS

A significant reduction (about 80%) in the expression levels of MTDH mRNA and an increase in the percentages of apoptotic cells (about 20%) were observed in the test group in comparison with control.

CONCLUSION

MTDH shRNA constructs effectively inhibited gene expression. However, simplicity and inexpensiveness of the method were additional advantages for its application.