5’isomiR-183-5p|+2 elicits tumor suppressor activity in a negative feedback loop with E2F1

Background

MicroRNAs (miRNAs) and isomiRs play important roles in tumorigenesis as essential regulators of gene expression. 5’isomiRs exhibit a shifted seed sequence compared to the canonical miRNA, resulting in different target spectra and thereby extending the phenotypic impact of the respective common pre-miRNA. However, for most miRNAs, expression and function of 5’isomiRs have not been studied in detail yet. Therefore, this study aims to investigate the functions of miRNAs and their 5’isomiRs.

Methods

The expression of 5’isomiRs was assessed in The Cancer Genome Atlas (TCGA) breast cancer patient dataset. Phenotypic effects of miR-183 overexpression in triple-negative breast cancer (TNBC) cell lines were investigated in vitro and in vivo by quantifying migration, proliferation, tumor growth and metastasis. Direct targeting of E2F1 by miR-183-5p|+2 was validated with a 3’UTR luciferase assay and linked to the phenotypes of isomiR overexpression.

Results

TCGA breast cancer patient data indicated that three variants of miR-183-5p are highly expressed and upregulated, namely miR-183-5p|0, miR-183-5p|+1 and miR-183-5p|+2. However, TNBC cell lines displayed reduced proliferation and invasion upon overexpression of pre-miR-183. While invasion was reduced individually by all three isomiRs, proliferation and cell cycle progression were specifically inhibited by overexpression of miR-183-5p|+2. Proteomic analysis revealed reduced expression of E2F target genes upon overexpression of this isomiR, which could be attributed to direct targeting of E2F1, specifically by miR-183-5p|+2. Knockdown of E2F1 partially phenocopied the effect of miR-183-5p|+2 overexpression on cell proliferation and cell cycle. Gene set enrichment analysis of TCGA and METABRIC patient data indicated that the activity of E2F strongly correlated with the expression of miR-183-5p, suggesting transcriptional regulation of the miRNA by a factor of the E2F family. Indeed, in vitro, expression of miR-183-5p was regulated by E2F1. Hence, miR-183-5p|+2 directly targeting E2F1 appears to be part of a negative feedback loop potentially fine-tuning its activity.

Conclusions

This study demonstrates that 5’isomiRs originating from the same arm of the same pre-miRNA (i.e. pre-miR-183-5p) may exhibit different functions and thereby collectively contribute to the same phenotype. Here, one of three isomiRs was shown to counteract expression of the pre-miRNA by negatively regulating a transcriptional activator (i.e. E2F1). We speculate that this might be part of a regulatory mechanism to prevent uncontrolled cell proliferation, which is disabled during cancer progression.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02380-8.

[Travel vaccinations in rheumatic diseases : Specific considerations in children and adults]

Children and adults with rheumatic diseases (RD) have a higher risk to contract infections due to the underlying disease and the frequently necessary immunosuppressive treatment (IT). The quality of life of the majority of patients with RD has remarkably improved due to IT-related reduction of inflammation. Therefore, RD patients usually have an international travel behavior similar to healthy individuals. An investigation indicated that patients with RD and IT have lower travel vaccination rates and are often less well-prepared for their trip in comparison to healthy travelers, even when visiting high risk destinations. As the risk for general and travel-acquired infections is increased for patients with RD with and without IT, pretravel consultations are important. These pretravel consultations should include recommendations addressing travel cancellation, travel modification and travel vaccinations depending on the patient's risk. Travel vaccinations include vaccinations against hepatitis A, typhoid fever, rabies, cholera, meningococcal diseases, tick-bone encephalitis, Japanese encephalitis, seasonal influenza, poliomyelitis and yellow fever. In patients with RD the indications for vaccination depend on the exposure risks, disease severity, individual travel behavior, and possible complications associated with vaccination. In the further evaluation process it is crucial to include the general health condition of the patient, the underlying RD (type and activity), duration and intensity of the IT. In general, live-attenuated vaccines are contraindicated under IT. In contrast, inactivated vaccines may be administered although reduced immunogenicity with the need for antibody measurement, special vaccine schedules or additional booster vaccinations should be considered under IT.

miRNA-1246 induces pro-inflammatory responses in mesenchymal stem/stromal cells by regulating PKA and PP2A

The tumor microenvironment (TME) has an impact on breast cancer progression by creating a pro-inflammatory milieu within the tumor. However, little is known about the roles of miRNAs in cells of the TME during this process. We identified six putative oncomiRs in a breast cancer dataset, all strongly correlating with poor overall patient survival. Out of the six candidates, miR-1246 was upregulated in aggressive breast cancer subtypes and expressed at highest levels in mesenchymal stem/stroma cells (MSCs). Functionally, miR-1246 led to a p65-dependent increase in transcription and release of pro-inflammatory mediators IL-6, CCL2 and CCL5 in MSCs, and increased NF-κB activity. The pro-inflammatory phenotype of miR-1246 in MSCs was independent of TNFα stimulations and mediated by direct targeting of the tumor-suppressors PRKAR1A and PPP2CB. In vitro recapitulation of the TME revealed increased Stat3 phosphorylation in breast epithelial (MCF10A) and cancer cells (SK-BR-3, MCF7, T47D) upon incubation with conditioned medium (CM) of MSCs overexpressing miR-1246. Additionally, this stimulation enhanced proliferation of MCF10A cells, increased migration of MDA-MB-231 cells and induced attraction of THP-1 monocytic cells. Our data shows that miR-1246 acts as both key-enhancer of pro-inflammatory responses in MSCs and putative oncomiR in breast cancer, suggesting its influence on cancer-related inflammation and breast cancer progression.

The highly expressed 5'isomiR of hsa-miR-140-3p contributes to the tumor-suppressive effects of miR-140 by reducing breast cancer proliferation and migration

Background

miRNAs are small noncoding RNA molecules that play an important role in post-transcriptional regulation of gene expression. Length and/or sequence variants of the same miRNA are termed isomiRs. While most isomiRs are functionally redundant compared to their canonical counterparts, the so-called 5’isomiRs exhibit a shifted 5’ end and therefore a shifted seed sequence resulting in a different target spectrum. However, not much is known about the functional relevance of these isoforms.

Results

Analysis of miRNA-seq data from breast cancer cell lines identified six pairs of highly expressed miRNAs and associated 5’isomiRs. Among them, hsa-miR-140-3p was of particular interest because its 5’isomiR showed higher expression compared to the canonical miRNA annotated in miRbase. This miRNA has previously been shown to control stemness of breast cancer cells. miRNAseq data of breast cancer patients (TCGA dataset) showed that both the canonical hsa-miR-140-3p and its 5’isomiR-140-3p were highly expressed in patients’ tumors compared to normal breast tissue. In the current work, we present the functional characterization of 5’isomiR-140-3p and the cellular phenotypes associated with its overexpression in MCF10A, MDA-MB-468 and MDA-MB-231 cell lines in comparison to the canonical hsa-miR-140-3p. Contrary to the effect of the canonical hsa-miR-140-3p, overexpression of the 5’isomiR-140-3p led to a decrease in cell viability. The latter observation was supported by cell cycle analysis, where the 5’isomiR-140-3p but not the hsa-miR-140-3p caused cell cycle arrest in G₀/G₁-phase. Additionally, 5’ismoiR-140-3p overexpression was found to cause a decrease in cell migration in the three cell lines. We identified three novel direct target genes of the 5’isomiR-140-3p; COL4A1, ITGA6 and MARCKSL1. Finally, we have shown that knocking down these genes partially phenocopied the effects of the 5’isomiR-140-4p overexpression, where COL4A1 and ITGA6 knockdown led to reduced cell viability and cell cycle arrest, while MARCKSL1 knockdown resulted in a decrease in the migratory potential of cells.

Conclusions

In summary, this work presents evidence that there is functional synergy between the canonical hsa-miR-140-3p and the newly identified 5’isomiR-140-3p in suppressing growth and progression of breast cancer by simultaneously targeting genes related to differentiation, proliferation, and migration.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2869-x) contains supplementary material, which is available to authorized users.

Supersilylverbindungen des Phosphors, V [1]. Darstellung, Struktur und Reaktivität des Pentaphosphids (tBu3Si)3P5Na2 und des Pentaphosphans (tBu3Si)3P5[2] / Supersilyl Compounds of Phosphorus, V [1]. Preparation, Structure, and Reactivity of the Pentaphosphide (tBu3Si)3P5Na2 and the Pentaphosphane (tBu3Si)3P5 [2]

The orange THF adduct (tBu3Si)3P5Na2 (THF)4 of the pentaphosphide (tBu3Si)3P5Na2 (3) has been prepared, (i) by protolysis of the tetraphosphide (tBu3Si)2P4Na2(THF)n (2) with CF3CO2H in THF (molar ratio 2 : 1 ) , (ii) by dissolving crystalline 2 in toluene, and (iii) by the reaction of P4 with tBu3SiNa(THF)2 in benzene (molar ratio 1 : 4). According to an X-ray structural analysis, the THF adduct of 3 contains a P3 ring with two PNa(SitBu3) substituents in cis position and one SitBu3 substituent in trans position to the former groups. The protolysis of 3 with CF3CO2H leads to the pentaphosphane P5H2(SitBu3)3 (9), the silylation of 3 with Me2SiCl2 to the pentaphosphane P5 (SiMe2)(SitBu3)3 (10), and the oxidation of 3 with C2(CN)4 to the pentaphosphane P5(SitBu3)3 (5). The structures of 3,5,9, and 10 have been assigned from 31P and 29Si NMR data. The pentaphosphane 5 contains a hitherto unknown P5 backbone of a P3 ring anellated with a P4 ring.

Zur Reaktion von PCl3 mit NaR*, KR* und ZnR*2 (R* = SitBu3) [1]: Bildung des Diphosphens R*P=PR*, Tetraphosphans P4R* 2 , Tetraphosphanids NaP4R* 3 sowie von Halogenphosphanen R* mPmClp / On the Reaction of PCl3 with NaR*, KR* and ZnR*2 (R*= SitBu3) [1]: Formation of the Diphosphene R*P=PR*, Tetraphosphane P4R*2, Tetraphosphanide NaP4R*3 as well as Halogenophosphanes R*mPnClp

The reaction of PCl3 at r. t. with an equimolar amount of NaR* in heptane gives the colorless phosphane R*PCl2 (1), the colorless diphosphane R*ClP-PClR* (2), the light green diphosphene R*P=PR* (4), the cyclotetraphosphane R*2P4Cl2 (6) (not isolated), the light yellow bis(cyclotriphosphanyl) P6R*4 (7), the cyclotriphosphane R*2P3Cl (8) (not isolated), and the colorless bicyclophosphane P4R*2 (9).With a threefold molar amount of NaR* in tetrahydrofuran the blue violet triphosphanide NaP3R*2 (10), the dark red tetraphosphanide NaP4R*3 (11), and the orange pentaphosphanediide Na2P5R*3 (12) are formed from PCl3 besides the phosphanides NaPR*2, Na2PR* (isolated), NaP2R*3 and Na2P2R*2. With a four-fold molar amount of KR* in benzene PCl3 gives the green diphosphanediide K2P2R*2 and the red phosphanediide K2PR*, and with an equimolar amount of ZnR*2 in heptane the compounds 1, 2, 4, 7 and 8 are obtained. The compound R*P=PR* (4), the first diphosphene with two silyl substituents, is formed in high yields from the action of Na on R*PCl2 in heptane at 90 "C. It gives a [2+4] cycloadduct with 2,3-dimethylbutadiene and phosphanides (Na2P2R*2 or Na2PR*) with Na or NaR*. Bicyclotetraphosphane P4R*2 (9) (structure: two R*P3 rings with a common edge) is exclusively obtained from Na2P4R*2 (formed quantitatively from P4 and 2 NaR*) and TCNE. 9 may be reduced (Na, THF) with reformation of Na2P4R*2 and reacts in the presence of NaR* with formation of dark red NaP4R*3 (11) (structure: P3 ring with two R* substituents in trans position and one PNaR* substituent). Straightforward syntheses of halogenophosphanes include (i) reactions of ZnR*2 with PCl3 or PBr3 (mole ratio 1 : 2) in heptane to form R*PCl2 (1) or R*PBr2, and (ii) reaction of R*2 with R*PCl2 (mole ratio 1 : 2) without a solvent, or of KR* and PCl3 (mole ratio 2 : 1) in benzene to formR*ClP-PClR* (2). The halogenophosphanes R*2P3Cl (8) (structure: P3 ring with two R* substituents in trans position and one Cl substituent) as well as R*2P4Cl2 (6) (structure: P4 ring with alternating R* and Cl substituents) have not been isolated. The 31P-NMR spectra and the pathways of formation of the phosphorus compounds are discussed

MicroRNA-31 sensitizes human breast cells to apoptosis by direct targeting of protein kinase C epsilon (PKCepsilon)

MicroRNAs post-transcriptionally regulate gene expression and thereby contribute to the modulation of numerous complex and disease-relevant cellular phenotypes, including cell proliferation, cell motility, apoptosis, and stress response. In breast cancer cell systems, miR-31 has been shown to inhibit cell migration, invasion, and metastasis. Here, we link enhanced expression of miR-31 to the inhibition of the oncogenic NF-κB pathway, thus supporting the tumor-suppressive function of this microRNA. We identified protein kinase C epsilon (PKCε encoded by the PRKCE gene) as a novel direct target of miR-31 and show that down-regulation of PKCε results in impaired NF-κB signaling, enhanced apoptosis, and increased sensitivity of MCF10A breast epithelial and MDA-MB-231 triple-negative breast cancer cells toward ionizing radiation as well as treatment with chemotherapeutics. Mechanistically, we attribute this sensitization to anti-cancer treatments to the PRKCE-mediated down-regulation of the anti-apoptotic factor BCL2. In clinical breast cancer samples, high BCL2 expression was associated with poor prognosis. Furthermore, we found an inverse correlation between miR-31 and BCL2 expression, highlighting the functional relevance of the indirect down-regulation of BCL2 via direct targeting of PRKCE by miR-31.