Background Ferroptosis is a novel mode of non-apoptotic cell death induced by build-up of toxic lipid peroxides (lipid-ROS) in an iron dependent manner. Cancer-associated fibroblasts (CAFs) support tumor progression and drug resistance by secreting various bioactive substances, including exosomes. Yet, the role of CAFs in regulating lipid metabolism as well as ferroptosis of cancer cells is still unexplored and remains enigmatic. Methods Ferroptosis-related genes in gastric cancer (GC) were screened by using mass spectrum; exosomes were isolated by ultra-centrifugation and CAF secreted miRNAs were determined by RT-qPCR. Erastin was used to induce ferroptosis, and ferroptosis levels were evaluated by measuring lipid-ROS, cell viability and mitochondrial membrane potential. Results Here, we provide clinical evidence to show that arachidonate lipoxygenase 15 (ALOX15) is closely related with lipid-ROS production in gastric cancer, and that exosome-miR-522 serves as a potential inhibitor of ALOX15. By using primary stromal cells and cancer cells, we prove that exosome-miR-522 is mainly derived from CAFs in tumor microenvironment. Moreover, heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) was found to mediate miR-522 packing into exosomes, and ubiquitin-specific protease 7 (USP7) stabilizes hnRNPA1 through de-ubiquitination. Importantly, cisplatin and paclitaxel promote miR-522 secretion from CAFs by activating USP7/hnRNPA1 axis, leading to ALOX15 suppression and decreased lipid-ROS accumulation in cancer cells, and ultimately result in decreased chemo-sensitivity. Conclusions The present study demonstrates that CAFs secrete exosomal miR-522 to inhibit ferroptosis in cancer cells by targeting ALOX15 and blocking lipid-ROS accumulation. The intercellular pathway, comprising USP7, hnRNPA1, exo-miR-522 and ALOX15, reveals new mechanism of acquired chemo-resistance in GC. Graphical abstract

Phosphofructokinase 1 (PFK1) plays a critical role in glycolysis; however, its role and regulation in tumorigenesis are not well understood. Here, we demonstrate that PFK1 platelet isoform (PFKP) is the predominant PFK1 isoform in human glioblastoma cells and its expression correlates with total PFK activity. We show that PFKP is overexpressed in human glioblastoma specimens due to an increased stability, which is induced by AKT activation resulting from phosphatase and tensin homologue (PTEN) loss and EGFR-dependent PI3K activation. AKT binds to and phosphorylates PFKP at S386, and this phosphorylation inhibits the binding of TRIM21 E3 ligase to PFKP and the subsequent TRIM21-mediated polyubiquitylation and degradation of PFKP. PFKP S386 phosphorylation increases PFKP expression and promotes aerobic glycolysis, cell proliferation, and brain tumor growth. In addition, S386 phosphorylation in human glioblastoma specimens positively correlates with PFKP expression, AKT S473 phosphorylation, and poor prognosis. These findings underscore the potential role and regulation of PFKP in human glioblastoma development.

Cardiac injury in neonatal 1-day-old mice stimulates a regenerative response characterized by reactive cardiomyocyte proliferation, which is distinguished from the fibrotic repair process in adults. Acute inflammation occurs immediately after heart injury and has generally been believed to exert a negative effect on heart regeneration by promoting scar formation in adults; however, little is known about the role of acute inflammation in the cardiac regenerative response in neonatal mice. Here, we show that acute inflammation induced cardiomyocyte proliferation after apical intramyocardial microinjection of immunogenic zymosan A particles into the neonatal mouse heart. We also found that cardiac injury-induced regenerative response was suspended after immunosuppression in neonatal mice, and that cardiomyocytes could not be reactivated to proliferate after neonatal heart injury in the absence of interleukin-6 (IL-6). Furthermore, cardiomyocyte-specific deletion of signal transducer and activator of transcription 3 (STAT3), the major downstream effector of IL-6 signaling, decreased reactive cardiomyocyte proliferation after apical resection. Our results indicate that acute inflammation stimulates the regenerative response in neonatal mouse heart, and suggest that modulation of inflammatory signals might have important implications in cardiac regenerative medicine.

microRNAs (miRNAs) play critical roles in cancer development and progression. This study investigated the effects of miR-138-5p in human colorectal cancer (CRC) development. miR-138-5p was frequently downregulated in CRC tissues and was associated with advanced clinical stage, lymph node metastasis and poor overall survival. We found that miR-138-5p decreased expression of programmed cell death ligand 1 (PD-L1) through interaction with its PD-L1 3′ untranslated region. miR-138-5p also dramatically suppressed CRC cell growth in vitro and inhibited tumorigenesis in vivo. PD-L1 and miR-138-5p levels were inversely correlated in human CRC tumors, and miR-138-5p inhibited PD-L1 expression in tumor models. These results suggest that miR-138-5p is a tumor suppressor in CRC, and its effects are exerted at least partially through PD-L1 downregulation. Low miR-138-5p and high PD-L1 levels correlated with shorter overall CRC patient survival, indicating that miR-138-5p and PD-L1 may serve as CRC biomarkers for risk group assignment, optimal therapy selection and clinical outcome prediction. Targeting PD-L1, possibly by administering miR-138-5p mimics, might be a clinically effective anti-CRC therapeutic strategy.

The mammalian SWI/SNF-like chromatin-remodeling BAF complex plays several important roles in controlling cell proliferation and differentiation. Interferons (IFNs) are key mediators of cellular antiviral and antiproliferative activities. In this report, we demonstrate that the BAF complex is required for the maximal induction of a subset of IFN target genes by alpha IFN (IFN-␣). The BAF complex is constitutively associated with the IFITM3 promoter in vivo and facilitates the chromatin remodeling of the promoter upon IFN-␣ induction. Furthermore, we show that the ubiquitous transcription activator Sp1 interacts with the BAF complex in vivo and augments the BAF-mediated activation of the IFITM3 promoter. Sp1 binds constitutively to the IFITM3 promoter in the absence of the BAF complex, suggesting that it may recruit and/or stabilize the BAF complex binding to the IFITM3 promoter. Our results bring new mechanistic insights into the antiproliferative effects of the chromatin-remodeling BAF complex.Interferons (IFNs) play several fundamental roles in cellular antiviral and antiproliferative activities (35,40). The signal of alpha/beta IFNs (IFN-␣/␤s) is mainly mediated by IFN-stimulated gene factor 3 (ISGF3), a trimeric complex consisting of STAT1, STAT2, and p48 (14,38,44), which binds to IFNstimulated regulatory elements (ISREs) to activate their target genes (6). Transcriptional activation of the IFN-induced genes is required for the actions of the IFNs (4, 40).The genomic DNA in the nucleus is packaged into nucleosomes that are inhibitory to the access of transcription factors to their target sites. Modification of the nucleosomal template is thought necessary to allow transcriptional activation. This modification can be either covalent bond formation by acetylation, phosphorylation, and methylation at the histone tails and/or noncovalent action by ATP-utilizing remodeling enzymes (1,13,17,19,30,36,41,43,47). Whereas the mechanism by which ISGF3 overcomes the chromatin barrier for binding to its targeting sites is not clear, signal transducer and activator of transcription (STAT) proteins have been found to interact with the highly conserved and ubiquitously expressed cyclic AMP response element-binding proteins, CBP/p300 (3, 15, 34, 49, 52). Both CBP and p300 have histone acetyltransferase activity (33). Overexpression of E1A, which binds to CBP/p300 and inhibits its histone acetyltransferase activity, blocks the ISRE-mediated responses to IFN-␣/␤ (3), suggesting that the modification of the chromatin structure might be an important step in the induction of IFN target genes.It was reported recently that the reconstitution of the active BAF complex by transient expression of the essential ATPase subunit BRG1 in BRG1-deficient SW-13 cells up-regulates several IFN target genes (27), suggesting that the chromatinremodeling activity of the BAF complex might be required for the induction of these genes by IFNs. In this report, we demonstrate that reconstitution of the BAF complex by transiently expressing BRG1 in SW-1...

We reported that complement cascade (CC) becomes activated in bone marrow (BM) during mobilization of hematopoietic stem/progenitor cells (HSPCs) induced by granulocyte-colony stimulating factor (G-CSF) and C5 cleavage plays an important role in optimal egress of HSPCs. In the current work, we explored whether CC is involved in mobilization of HSPCs induced by the CXCR4 antagonist, AMD3100. To address this question, we performed mobilization studies in mice that display a defect in the activation of the proximal steps of CC (Rag−/−, SCID, C2.Cfb−/−) as well as in mice that do not activate the distal steps of CC (C5−/−). We noticed that proximal CC activation-deficient mice (above C5 level), in contrast to distal step CC activation-deficient C5−/− ones mobilize normally in response to AMD3100 administration. We hypothesized that this discrepancy in mobilization could be explained by AMD3100 activating C5 in Rag−/−, SCID, C2.Cfb−/− animals in a non-canonical mechanism involving activated granulocytes. To support this granulocytes i) as first egress from BM and ii) secrete several proteases that cleave/activate C5 in response to AMD3100. We conclude that AMD3100-directed mobilization of HSPCs, similarly to G-CSF-induced mobilization, depends on activation of CC; however, in contrast to G-CSF, AMD3100 activates the distal steps of CC directly at the C5 level. Overall, these data support that C5 cleavage fragments and distal steps of CC activation are required for optimal mobilization of HSPCs.

Chemoresistance is one of the causes of adverse effects in gastric cancer, including a poor response to cisplatin (DDP). Exosomes loaded with microRNA (miRNA), mRNA, and other non-coding RNAs could regulate drug resistance. Exo-anti-214 was extracted and verified. A Cell Counting Kit-8 (CCK-8) cell viability assay, flow cytometry, and transwell and immunofluorescence assays were performed to determine whether exo-anti-214 could sensitize cells to DDP in vitro. A combination of intravenously injected exo-anti-214 and intraperitoneal DDP was utilized in vivo. Additionally, potential targets of miR-214 were screened by mass spectrometry (MS) and confirmed via western blotting (WB). The levels of miR-214 in the human immortalized gastric epithelial cell line ges-1 and the human gastric adenocarcinoma cell lines SGC7901 and SGC7901/DDP gradually increased. Exo-anti-214 could fuse with cells and regulate potential targets, reducing cell viability, suppressing migration, and promoting apoptosis in vitro. Caudally injected exo-anti-214 was applied to reverse chemoresistance and repress tumor growth in vivo due to the downregulation of miR-214 and overexpression of possible target proteins in tumors. Exo-anti-214 could reverse the resistance to DDP in gastric cancer, which might serve as a potential alternative for the treatment of cisplatin-refractory gastric cancer in the future.

Recently, we identified a population of Oct4 + Sca-1 + Lin -CD45 -very small embryonic-like stem cells (VSELs) in murine and human adult tissues. VSELs can differentiate in vitro into cells from all 3 germ layers and in vivo tissue-committed stem cells. Open chromatin structure of core pluripotency transcription factors (TFs) supports the pluripotent state of VSELs. However, it has been difficult to determine how primitive VSELs maintain pluripotency, owing to their limited number in adult tissues. Here, we demonstrate by genome-wide geneexpression analysis with a small number of highly purified murine bone marrow-derived VSELs that Oct4 + VSELs (i) express a similar, yet nonidentical, transcriptome as embryonic stem cells (ESCs), (ii) highly express cell cycle checkpoint genes, (iii) express at a low level genes involved in protein turnover and mitogenic pathways, and (iv) highly express enhancer of zeste drosophila homolog 2 (Ezh2), a polycomb group protein. Furthermore, as a result of high expression of Ezh2, VSELs, like ESCs, exhibit bivalently modified nucleosomes (trimethylated H3K27 and H3K4) at promoters of important homeodomain-containing developmental TFs, thus preventing premature activation of the lineage-committing factors. Notably, spontaneous or RNA interferenceenforced downregulation of Ezh2 during VSEL differentiation removes the bivalent domain (BD) structure, which leads to de-repression of several BD-regulated genes. Therefore, we suggest that Oct4 + VSELs, like other pluripotent stem cells, maintain their pluripotent state through an Ezh2-dependent BD-mediated epigenetic mechanism. Furthermore, our global survey of VSEL gene expression signature would not only advance our understanding of biological process for their pluripotency, differentiation, and quiescence but should also help to develop better protocols for ex vivo expansion of VSELs.