Uev1A facilitates osteosarcoma differentiation by promoting Smurf1-mediated Smad1 ubiquitination and degradation

Aberrant LETM1 elevation dysregulates mitochondrial functions and energy metabolism and promotes lung metastasis in osteosarcoma

Osteosarcoma is a differentiation-deficient disease, and despite the unique advantages and great potential of differentiation therapy, there are only a few known differentiation inducers, and little research has been done on their targets. Cell differentiation is associated with an increase in mitochondrial content and activity. The metabolism of some tumor cells is characterized by impaired oxidative phosphorylation, as well as up-regulation of aerobic glycolysis and pentose phosphate pathways. Leucine-containing zipper and EF-hand transmembrane protein 1 (LETM1) is involved in the maintenance of mitochondrial morphology and is closely associated with tumorigenesis and progression, as well as cancer cell stemness. We found that MG63 and 143B osteosarcoma cells overexpress LETM1 and exhibit abnormalities in mitochondrial structure and function. Knockdown of LETM1 partially restored the mitochondrial structure and function, inhibited the pentose phosphate pathway, promoted oxidative phosphorylation, and led to osteogenic differentiation. It also inhibited spheroid cell formation, proliferation, migration, and invasion in an in vitro model. When LETM1 was knocked down in vivo, there was reduced tumor formation and lung metastasis. These data suggest that mitochondria are aberrant in LETM1-overexpressing osteosarcoma cells, and knockdown of LETM1 partially restores the mitochondrial structure and function, inhibits the pentose phosphate pathway, promotes oxidative phosphorylation, and increases osteogenic differentiation, thereby reducing malignant biological behavior of the cells.

Echinococcus granulosus ubiquitin-conjugating enzymes (E2D2 and E2N) promote the formation of liver fibrosis in TGFβ1-induced LX-2 cells

BACKGROUND

Cystic echinococcosis (CE) is a widespread zoonosis caused by the infection with Echinococcus granulosus sensu lato (E. granulosus s.l.). CE cysts mainly develop in the liver of intermediate hosts, characterized by the fibrotic tissue that separates host organ from parasite. However, precise mechanism underlying the formation of fibrotic tissue in CE remains unclear.

METHODS

To investigate the potential impact of ubiquitin-conjugating enzymes on liver fibrosis formation in CE, two members of ubiquitin-conjugating (UBC) enzyme of Echinococcus granulosus (EgE2D2 and EgE2N) were recombinantly expressed in Escherichia coli and analyzed for bioinformatics, immunogenicity, localization, and enzyme activity. In addition, the secretory pathway and their effects on the formation of liver fibrosis were also explored.

RESULTS

Both rEgE2D2 and rEgE2N possess intact UBC domains and active sites, exhibiting classical ubiquitin binding activity and strong immunoreactivity. Additionally, EgE2D2 and EgE2N were widely distributed in protoscoleces and germinal layer, with differences observed in their distribution in 25-day strobilated worms. Further, these two enzymes were secreted to the hydatid fluid and CE-infected sheep liver tissues via a non-classical secretory pathway. Notably, TGFβ1-induced LX-2 cells exposed to rEgE2D2 and rEgE2N resulted in increasing expression of fibrosis-related genes, enhancing cell proliferation, and facilitating cell migration.

CONCLUSIONS

Our findings suggest that EgE2D2 and EgE2N could secrete into the liver and may interact with hepatic stellate cells, thereby promoting the formation of liver fibrosis.

Protein Stability Regulation in Osteosarcoma: The Ubiquitin-like Modifications and Glycosylation as Mediators of Tumor Growth and as Targets for Therapy

The identification of new therapeutic targets and the development of innovative therapeutic approaches are the most important challenges for osteosarcoma treatment. In fact, despite being relatively rare, recurrence and metastatic potential, particularly to the lungs, make osteosarcoma a deadly form of cancer. In fact, although current treatments, including surgery and chemotherapy, have improved survival rates, the disease's recurrence and metastasis are still unresolved complications. Insights for analyzing the still unclear molecular mechanisms of osteosarcoma development, and for finding new therapeutic targets, may arise from the study of post-translational protein modifications. Indeed, they can influence and alter protein structure, stability and function, and cellular interactions. Among all the post-translational modifications, ubiquitin-like modifications (ubiquitination, deubiquitination, SUMOylation, and NEDDylation), as well as glycosylation, are the most important for regulating protein stability, which is frequently altered in cancers including osteosarcoma. This review summarizes the relevance of ubiquitin-like modifications and glycosylation in osteosarcoma progression, providing an overview of protein stability regulation, as well as highlighting the molecular mediators of these processes in the context of osteosarcoma and their possible targeting for much-needed novel therapy.

Cellular functions and molecular mechanisms of ubiquitination in osteosarcoma

Although some advances have been made in the treatment of osteosarcoma in recent years, surgical resection remains the mainstream treatment. Initial and early diagnosis of osteosarcoma could be very difficult to achieve due to the insufficient sensitivity for the means of examination. The distal metastasis of osteosarcoma also predicts the poor prognosis of osteosarcoma. In order to solve this series of problems, people begin to discover a new method of diagnosing and treating osteosarcoma. Ubiquitination, as an emerging posttranslational modification, has been shown to be closely related to osteosarcoma in studies over the past decades. In general, this review describes the cellular functions and molecular mechanisms of ubiquitination during the development of osteosarcoma.

A ubiquitin-related gene signature for predicting prognosis and constructing molecular subtypes in osteosarcoma

Background: Ubiquitination is medicated by three classes of enzymes and has been proven to involve in multiple cancer biological processes. Moreover, dysregulation of ubiquitination has received a growing body of attention in osteosarcoma (OS) tumorigenesis and treatment. Therefore, our study aimed to identify a ubiquitin-related gene signature for predicting prognosis and immune landscape and constructing OS molecular subtypes.

Methods: Therapeutically Applicable Research to Generate Effective Treatments (TARGET) was regarded as the training set through univariate Cox regression, Lasso Cox regression, and multivariate Cox regression. The GSE21257 and GSE39055 served as the validation set to verify the predictive value of the signature. CIBERSORT was performed to show immune infiltration and the immune microenvironment. The NMF algorithm was used to construct OS molecular subtypes.

Results: In this study, we developed a ubiquitin-related gene signature including seven genes (UBE2L3, CORO6, DCAF8, DNAI1, FBXL5, UHRF2, and WDR53), and the gene signature had a good performance in predicting prognosis for OS patients (AUC values at 1/3/5 years were 0.957, 0.890, and 0.919). Multivariate Cox regression indicated that the risk score model and prognosis stage were also independent prognostic prediction factors. Moreover, analyses of immune cells and immune-related functions showed a significant difference in different risk score groups and the three clusters. The drug sensitivity suggested that IC50 of proteasome inhibitor (MG-132) showed a notable significance between the risk score groups (p < 0.05). Through the NMF algorithm, we obtained the three clusters, and cluster 3 showed better survival outcomes. The expression of ubiquitin-related genes (CORO6, UBE2L3, FBXL5, DNAI1, and DCAF8) showed an obvious significance in normal and osteosarcoma tissues.

Conclusion: We developed a novel ubiquitin-related gene signature which showed better predictive prognostic ability for OS and provided additional information on chemotherapy and immunotherapy. The OS molecular subtypes would also give a useful guide for individualized therapy.

Prognostic value of p16, p53, and pcna in sarcoma and an evaluation of immune infiltration

Background

p16, p53, and proliferating cell nuclear antigen (pcna) genes play significant roles in many chromatin modifications and have been found to be highly expressed in a variety of tumor tissues. Therefore, they have been used as target genes for some tumor therapies. However, the differential expressions of the p16, p53, and pcna genes in human sarcomas and their effects on prognosis have not been widely reported.

Methods

The Oncomine dataset was used to analyze the transcription levels of p16, p53, and pcna genes, and the gene expression profile interactive analysis (GEPIA) dataset was used to analyze the differential expressions of p16, p53, and pcna. The expression levels of p16, p53, and pcna were further analyzed by Western Blotting. GEPIA and Kaplan–Meier analyses were used to analyze the prognostic value of p16, p53, and pcna. Furthermore, p16, p53, and pcna gene mutations and their association with overall survival (OS) and disease-free survival (DFS) were analyzed using cBioPortal datasets. In addition, genes co-expressed with p16, p53, and pcna were analyzed using Oncomine. The DAVID dataset was used to analyze the functional enrichment of p16, p53, pcna, and their co-expressed genes by Gene Ontology (GO) and Metascape were used to construct a network map. Finally, the immune cell infiltration of p16, p53, and pcna in patients with sarcoma was reported by Tumor Immune Estimation Resource (TIMER).

Results

p16, p53, and pcna were up-regulated in human sarcoma tissues and almost all sarcoma cell lines. Western Blotting showed that the expression of p16, p53, and pcna was elevated in osteosarcoma cell lines. The expression of pcna was correlated with OS, the expression of p16, p53, and pcna was correlated with relapse-free survival, and the genetic mutation of p16 was negatively correlated with OS and DFS. We also found that p16, p53, and pcna genes were positively/negatively correlated with immune cell infiltration in sarcoma.

Conclusions

The results of this study showed that p16, p53, and pcna can significantly affect the survival and immune status of sarcoma patients. Therefore, p16, p53, and pcna could be used as potential biomarkers of prognosis and immune infiltration in human sarcoma and provide a possible therapeutic target for sarcoma.

Ube2N is present and functions within listeria Actin-rich structures and lamellipodia: A localization and pharmacological inhibition study

The actin cytoskeleton forms much of the structure needed for the intracellular motility of an assortment of microbes as well as entire cells. The co-factor to the ubiquitin conjugating enzyme Ube2N (Ube2V1) has been implicated in both cancer cell metastasis and lysine-63 ubiquitylation of β actin. As this protein complexes with Ube2N, we sought to investigate whether Ube2N itself was involved in actin-based events occurring during the Listeria monocytogenes infections as well as within motile whole cells. Through examination of L. monocytogenes actin clouds, comet tails and membrane protrusions as well as lamellipodia in migrating cells, we show that Ube2N is recruited to actin-rich structures. When pharmacologically inhibited we demonstrate that Ube2N is crucial for the function of actin-rich structures when associated with the plasma membrane.

Ubiquitin-conjugating enzyme V variant 1 enables cellular responses toward fibroblast growth factor signaling in endothelium

Ubiquitination has been shown to provide an essential regulatory role in modulating the duration and amplitude of the signaling activity in angiogenesis. While successive enzymatic reactions mediated by three distinct types of enzymes commonly known as E1, E2, and E3 are required for ubiquitination, the role of E3s which govern the final step of ubiquitination has been extensively analyzed in angiogenesis. In contrast, the role of E2s, which determine the context and functional consequences of ubiquitination, remains largely unknown with respect to angiogenesis. To better elucidate the role of E2s in modulating endothelial behaviors during angiogenesis, we first systematically analyze the expression pattern of E2s in endothelial cells (ECs) using previously published scRNA-seq data and identify ubiquitin-conjugating enzyme variant 1 (UBE2V1), an unconventional E2 without innate catalytic activity, as one of the most abundantly expressed E2s in ECs. While ubiquitously expressed in diverse cell types, abrogation of UBE2V1 significantly impairs proliferation and viability of human umbilical vein endothelial cells (HUVECs) without affecting other cell types, suggesting that UBE2V1 is likely to possess nonredundant functions in ECs. Consistent with this idea, UBE2V1 appears to be critical for morphogenesis and migration of ECs during angiogenesis. Interestingly, we find that UBE2V1 is essential for fibroblast growth factor 2 (FGF2)-induced angiogenesis, but appears to have minor effects on vascular endothelial growth factor-A-induced angiogenesis in vitro as well as in vivo. Therefore, it seems that UBE2V1 could enable ECs to distinguish two related yet distinct angiogenic cues. Mechanistically, we show that UBE2V1 promotes ubiquitination of MEK kinase 1, a key mediator of FGF2 signaling, to enhance phosphorylation of extracellular signal-regulated kinase 1/2 in HUVECs. Taken together, our results illustrate the unique role of UBE2V1 as a key modulator for angiogenic behaviors in ECs.

WNT11, a new gene associated with early-onset osteoporosis, is required for osteoblastogenesis

Monogenic early-onset osteoporosis (EOOP) is a rare disease defined by low bone mineral density (BMD) that results in increased risk of fracture in children and young adults. Although several causative genes have been identified, some of the EOOP causation remains unresolved. Whole-exome sequencing revealed a de novo heterozygous loss-of-function mutation in WNT11 (NM_004626.2:c.677_678dup p.Leu227Glyfs*22) in a 4-year-old boy with low BMD and fractures. We identified two heterozygous WNT11 missense variants (NM_004626.2:c.217G > A p.Ala73Thr) and (NM_004626.2:c.865G > A p.Val289Met) in a 51-year-old woman and in a 61-year-old woman respectively, both with bone fragility. U2OS cells with heterozygous WNT11 mutation (NM_004626.2:c.690_721delfs*40) generated by CRISPR-Cas9 showed reduced cell proliferation (30%) and osteoblast differentiation (80%) as compared with wild-type U2OS cells. The expression of genes in the Wnt canonical and non-canonical pathways was inhibited in these mutant cells, but recombinant WNT11 treatment rescued the expression of Wnt pathway target genes. Furthermore, the expression of RSPO2, a WNT11 target involved in bone cell differentiation, and its receptor LGR5, was decreased in WNT11 mutant cells. Treatment with WNT5A and WNT11 recombinant proteins reversed LGR5 expression, but WNT3A recombinant protein treatment had no effect on LGR5 expression in mutant cells. Moreover, treatment with recombinant RSPO2 but not WNT11 or WNT3A activated the canonical pathway in mutant cells. In conclusion, we have identified WNT11 as a new gene responsible for EOOP, with loss-of-function variant inhibiting bone formation via Wnt canonical and non-canonical pathways. WNT11 may activate Wnt signaling by inducing the RSPO2-LGR5 complex via the non-canonical Wnt pathway.

Pharmacological Modulation of Ubiquitin-Proteasome Pathways in Oncogenic Signaling

The ubiquitin-proteasome pathway (UPP) is involved in regulating several biological functions, including cell cycle control, apoptosis, DNA damage response, and apoptosis. It is widely known for its role in degrading abnormal protein substrates and maintaining physiological body functions via ubiquitinating enzymes (E1, E2, E3) and the proteasome. Therefore, aberrant expression in these enzymes results in an altered biological process, including transduction signaling for cell death and survival, resulting in cancer. In this review, an overview of profuse enzymes involved as a pro-oncogenic or progressive growth factor in tumors with their downstream signaling pathways has been discussed. A systematic literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on modulation of ubiquitin-proteasome pathways in oncogenic signaling. Various in vitro, in vivo studies demonstrating the involvement of ubiquitin-proteasome systems in varied types of cancers and the downstream signaling pathways involved are also discussed in the current review. Several inhibitors of E1, E2, E3, deubiquitinase enzymes and proteasome have been applied for treating cancer. Some of these drugs have exhibited successful outcomes in in vivo studies on different cancer types, so clinical trials are going on for these inhibitors. This review mainly focuses on certain ubiquitin-proteasome enzymes involved in developing cancers and certain enzymes that can be targeted to treat cancer.

Uev1A promotes breast cancer cell migration by up-regulating CT45A expression via the AKT pathway

Background

UEV1A encodes a ubiquitin-E2 variant closely associated with tumorigenesis and metastasis, but its underlying mechanism in promoting metastasis remains to be investigated.

Methods

In this study, we experimentally manipulated UEV1A and CT45A gene expression and monitored their effects on cancer-related gene expression, cell migration and the signal transduction cascade.

Results

It was found that UEV1A overexpression induces CT45A family gene expression in breast cancer cells. Indeed, ectopic expression of UEV1A was sufficient to induce CT45A and its downstream genes involved in tumorigenesis, epithelial-mesenchymal transition (EMT), stemness and metastasis, and to promote cell migration and EMT signaling. Consistently, depletion of CT45A abolished the above effects, indicating that CT45A is a critical downstream effector of Uev1A. The Uev1A-induced cell migration and EMT signaling was dependent on AKT but independent of NF-κB, indicating that CT45A acts downstream of the AKT pathway.

Conclusions

Based on previous reports and observations in this study, we propose that the Ubc13-Uev1A complex activates AKT through K63-linked polyubiquitination, which leads to enhanced CT45A expression, stimulated cell migration and EMT signaling in breast cells. Since similar effects were also observed in a colorectal cancer cell line, the Ubc13/Uev1A-AKT-CT45A axis may also promote tumorigenesis and metastasis in other tissues.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08750-3.

The Molecular Basis of Ubiquitin-Conjugating Enzymes (E2s) as a Potential Target for Cancer Therapy

Ubiquitin-conjugating enzymes (E2s) are one of the three enzymes required by the ubiquitin-proteasome pathway to connect activated ubiquitin to target proteins via ubiquitin ligases. E2s determine the connection type of the ubiquitin chains, and different types of ubiquitin chains regulate the stability and activity of substrate proteins. Thus, E2s participate in the regulation of a variety of biological processes. In recent years, the importance of E2s in human health and diseases has been particularly emphasized. Studies have shown that E2s are dysregulated in variety of cancers, thus it might be a potential therapeutic target. However, the molecular basis of E2s as a therapeutic target has not been described systematically. We reviewed this issue from the perspective of the special position and role of E2s in the ubiquitin-proteasome pathway, the structure of E2s and biological processes they are involved in. In addition, the inhibitors and microRNAs targeting E2s are also summarized. This article not only provides a direction for the development of effective drugs but also lays a foundation for further study on this enzyme in the future.

Leishmania differentiation requires ubiquitin conjugation mediated by a UBC2-UEV1 E2 complex

Post-translational modifications such as ubiquitination are important for orchestrating the cellular transformations that occur as the Leishmania parasite differentiates between its main morphological forms, the promastigote and amastigote. 2 E1 ubiquitin-activating (E1), 13 E2 ubiquitin-conjugating (E2), 79 E3 ubiquitin ligase (E3) and 20 deubiquitinating cysteine peptidase (DUB) genes can be identified in the Leishmania mexicana genome but, currently, little is known about the role of E1, E2 and E3 enzymes in this parasite. Bar-seq analysis of 23 E1, E2 and HECT/RBR E3 null mutants generated in promastigotes using CRISPR-Cas9 revealed numerous loss-of-fitness phenotypes in promastigote to amastigote differentiation and mammalian infection. The E2s UBC1/CDC34, UBC2 and UEV1 and the HECT E3 ligase HECT2 are required for the successful transformation from promastigote to amastigote and UBA1b, UBC9, UBC14, HECT7 and HECT11 are required for normal proliferation during mouse infection. Of all ubiquitination enzyme null mutants examined in the screen, Δubc2 and Δuev1 exhibited the most extreme loss-of-fitness during differentiation. Null mutants could not be generated for the E1 UBA1a or the E2s UBC3, UBC7, UBC12 and UBC13, suggesting these genes are essential in promastigotes. X-ray crystal structure analysis of UBC2 and UEV1, orthologues of human UBE2N and UBE2V1/UBE2V2 respectively, reveal a heterodimer with a highly conserved structure and interface. Furthermore, recombinant L. mexicana UBA1a can load ubiquitin onto UBC2, allowing UBC2-UEV1 to form K63-linked di-ubiquitin chains in vitro. Notably, UBC2 can cooperate in vitro with human E3s RNF8 and BIRC2 to form non-K63-linked polyubiquitin chains, showing that UBC2 can facilitate ubiquitination independent of UEV1, but association of UBC2 with UEV1 inhibits this ability. Our study demonstrates the dual essentiality of UBC2 and UEV1 in the differentiation and intracellular survival of L. mexicana and shows that the interaction between these two proteins is crucial for regulation of their ubiquitination activity and function.

The post-translational modification of proteins is key for allowing Leishmania parasites to transition between the different life cycle stages that exist in its insect vector and mammalian host. In particular, components of the ubiquitin system are important for the transformation of Leishmania from its insect (promastigote) to mammalian (amastigote) stage and normal infection in mice. However, little is known about the role of the enzymes that generate ubiquitin modifications in Leishmania. Here we characterise 28 enzymes of the ubiquitination pathway and show that many are required for life cycle progression or mouse infection by this parasite. Two proteins, UBC2 and UEV1, were selected for further study based on their importance in the promastigote to amastigote transition. We demonstrate that UBC2 and UEV1 form a heterodimer capable of carrying out ubiquitination and that the structural basis for this activity is conserved between Leishmania, Saccharomyces cerevisiae and humans. We also show that the interaction of UBC2 with UEV1 alters the nature of the ubiquitination activity performed by UBC2. Overall, we demonstrate the important role that ubiquitination enzymes play in the life cycle and infection process of Leishmania and explore the biochemistry underlying UBC2 and UEV1 function.

Drosophila Uev1a is dually required for Ben-dependent DNA-damage response and fly mobility

K63-linked polyubiquitination requires the ubiquitin-conjugating enzyme Ubc13 and a Ubc/E2 variant Uev. Lower eukaryotic organisms contain one UEV gene required for DNA-damage tolerance, while vertebrates and higher plants contain multiple UEV genes with distinct functions. In contrast, Drosophila contains only one UEV gene designated dUev1a. Here we report that dUev1a forms a stable heterodimer with Ben, the Drosophila Ubc13 ortholog, that dUev1a-F15E completely abolishes the interaction, and that a conserved dUev1a-F15Y substitution severely reduces its interaction with Ben. dUev1a functionally rescues the corresponding yeast mms2 null mutant from killing by various DNA-damaging agents in a Ben-dependent manner, and the heterozygous dUev1a mutant flies are more sensitive to DNA-damaging agent, indicating that the function of UEV in DNA-damage response is conserved throughout eukaryotes. Meanwhile, dUev1a^+/- mutant flies displayed reduced mobility characteristic of defects in the central nervous system and reminiscent of the bendless phenotypes, suggesting that dUev1a acts together with Ben in this process. Our observations collectively imply that dUev1a is dually required for DNA-damage response and neurological signaling in Drosophila, and that these processes are mediated by the Ben-dUev1a complex that promotes K63-linked polyubiquitination.

Identification of the Novel Target Genes for Osteosarcoma Therapy Based on Comprehensive Bioinformatic Analysis

Osteosarcoma is one of the most common primary malignant tumors of the bone and tends to develop in teenage years. Although multitreatments for the diagnosis and therapy of osteosarcoma have been developed, there are still needs of new methods to prevent and treat the osteosarcoma. Here, we performed bioinformatic analysis to screen for the key genes, molecules, and pathways involved in osteosarcoma survival. Four microarray data sets (GSE99671, GSE87624, GSE65071, and GSE28423), which include data from human bone and osteosarcoma samples, were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed mRNAs and miRNAs were identified. Kyoto Encyclopedia of Genes and Genomes enriched pathways, miRNA-mRNA target, gene/disease relationship, and overall survival was elucidated using related websites and software according to bioinformatic analysis protocols. We found three critical genes miR-29c, blood vessel epicardial substance (BVES), and proteasome 20S subunit beta 2 (PSMB2) through the GEO database and predicting miRNA-mRNA target. Among these genes, BVES and PSMB2 presented a high expression level in osteosarcoma based on GSE99671 and GSE87624 data sets, while miR-29c showed a low expression level in osteosarcoma based on GSE65071 and GSE28423 data sets. Furthermore, we found that the high expression level of miR-29c and BVES associated with better prognosis, while highly expressed PSMB2 associated with poor prognosis. The abnormally expressed mRNAs and miRNAs, which were identified by integrated bioinformatic analysis, provided insights into the molecular mechanisms of osteosarcoma. Notably, we found three critical genes that could be used as novel therapeutic targets for preventing or diagnosing osteosarcoma. Finally, PSMB2 may be the target of miR-29c.

Exosomal miR-125a-5p derived from silica-exposed macrophages induces fibroblast transdifferentiation

Silica particles can cause a systemic disease in workers termed lung silicosis, characterized by diffuse fibrosis. The development of lung silicosis involves various signaling pathway networks comprising numerous cell types and cytokines. As an important medium for communication between cells, exosomes have emerged as a hot research topic; however, the role of exosomal microRNAs (miRNAs) in silicosis remains unclear. In this study, we conducted high-throughput sequencing to generate exosomal miRNAs profiles from macrophages that were either exposed to silica or not. A total of 298 miRNAs were differentially expressed, with 155 up-regulated and 143 down-regulated. Highly conserved differentially expressed miRNAs were functionally annotated and analyzed to predict target genes. Among target interactions associated with the TGF-β signaling pathway, miR-125a-5p and its putative target gene, Smurf1, were subjected to further research. As expected, levels of miR-125a-5p were upregulated in human serous exosomes and vitro, and inhibit the exosomal miR-125a-5p suppressed the expression of the fibrosis hallmarks. Besides, high levels of the miRNA led to upregulation of smooth muscle actin alpha and repression of Smurf1 in NIH-3T3 and MRC-5 cells. ID1 and SMAD1, downstream of TGF-β signaling, were upregulated, indicating potential activation of this signaling pathway. These results contribute to understanding of the intercellular communication mediated by exosomal miRNAs and its critical role in fibroblast to myofibroblast transition and silicosis.

Advances in differentiation therapy for osteosarcoma

Differentiation therapy involves the use of agents that can induce differentiation in cancer cells, with the irreversible loss of tumour phenotype. The application of differentiation therapy in osteosarcoma has made progress because of a better understanding of the potential links between differentiation defects and tumorigenesis. Here, we review recent studies on differentiation therapy for osteosarcoma, describing a variety of differentiation inducers. By highlighting these examples of drug-induced osteosarcoma cell differentiation, we can acquire unique insights into not only osteosarcoma treatment, but also novel approaches to transform differentiating drugs into more effective therapies for other solid tumours.

The Role of Ubiquitination in Regulating Embryonic Stem Cell Maintenance and Cancer Development

Ubiquitination regulates nearly every aspect of cellular events in eukaryotes. It modifies intracellular proteins with 76-amino acid polypeptide ubiquitin (Ub) and destines them for proteolysis or activity alteration. Ubiquitination is generally achieved by a tri-enzyme machinery involving ubiquitin activating enzymes (E1), ubiquitin conjugating enzymes (E2) and ubiquitin ligases (E3). E1 activates Ub and transfers it to the active cysteine site of E2 via a transesterification reaction. E3 coordinates with E2 to mediate isopeptide bond formation between Ub and substrate protein. The E1-E2-E3 cascade can create diverse types of Ub modifications, hence effecting distinct outcomes on the substrate proteins. Dysregulation of ubiquitination results in severe consequences and human diseases. There include cancers, developmental defects and immune disorders. In this review, we provide an overview of the ubiquitination machinery and discuss the recent progresses in the ubiquitination-mediated regulation of embryonic stem cell maintenance and cancer biology.

Uev1A-Ubc13 promotes colorectal cancer metastasis through regulating CXCL1 expression via NF-кB activation

Colorectal cancer is the second most common cause of cancer-related death worldwide. Uncontrolled growth and distant metastasis are hallmarks of colorectal cancer. However, the precise etiological factors and the mechanisms are diverse and still largely unclear. The potential proto-oncogene UEV1A encodes a ubiquitin conjugating enzyme variant, which is required for Ubc13-catalyzed K63-linked poly-ubiquitination of target proteins and the activation of NF-кB, a transcription factor known to be involved in innate immunity, anti-apoptosis, inflammation and cancer. In order to understand the roles of Uev1A in colon cancer progression, we experimentally manipulated the Uev1A level in HCT116 colon cancer cells and found that UEV1A overexpression alone is sufficient to promote invasion in vitro and metastasis in vivo. This process is mediated by NF-κB activation and depends on its physical interaction with Ubc13. No expression of Uev1A was detected in histologically normal human colonic mucosa, but its expression was detected in human colorectal adenocarcinoma, which was closely correlated with nuclear p65 levels, an indicator of NF-κB activation. Uev1A protein was detected in 46% of primary tumors and 79% of metastatic tumors examined. Our experimental data establish that among NF-κB target genes, Uev1A-regulated CXCL1 expression plays a critical role in colon cell invasion and metastasis, a notion supported by the colon adenocarcinoma survey. Furthermore, experimental depletion of Uev1 in HCT116 cells reduces CXCL1 expression, and prevents cell invasion and tumor growth in a xenograft mouse model. These results identify Uev1A as a potential therapeutic target in the treatment of metastatic colorectal cancers.