Identification of XAF1-MT2A mutual antagonism as a molecular switch in cell-fate decisions under stressful conditions

Near-infrared light responsive gold nanoparticles coating endows polyetheretherketone with enhanced osseointegration and antibacterial properties

Polyetheretherketone (PEEK) is considered as a promising dental implant material owing to its excellent physicochemical and mechanical properties. However, its wide range of applications is limited by its biologically inert nature. In this study, a near-infrared (NIR) light responsive bioactive coating with gold nanoparticles (AuNPs) and metronidazole adhered to the PEEK surface via dopamine polymerization. Compared to pure PEEK, the hydrophilicity of the treated PEEK surface was significantly improved. In addition, under NIR light, the surface coating exhibited photothermal conversion effect, and gold nanoparticles and the antibiotic can be released from the coating. This improved the antibacterial properties of PEEK materials. Moreover, the coating was more conducive to the early adhesion of bone mesenchymal stem cells. The results of in vitro and in vivo osteogenic activity studies showed that the developed coating promoted osseointegration of PEEK implants, and NIR light irradiation further improved the antibacterial ability and osteogenic activity of PEEK implants. Through RNA sequencing, the potential underlying mechanism of promoting bone formation of the AuNPs coating combined metronidazole was interpreted. In summary, the developed coating is a potential surface treatment strategy that endows PEEK with enhanced osseointegration and antibacterial properties.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

The biological significance of cuproptosis-key gene MTF1 in pan-cancer and its inhibitory effects on ROS-mediated cell death of liver hepatocellular carcinoma

Metal regulatory transcription factor 1 (MTF1) has been reported to be correlated with several human diseases, especially like cancers. Exploring the underlying mechanisms and biological functions of MTF1 could provide novel strategies for clinical diagnosis and therapy of cancers. In this study, we conducted the comprehensive analysis to evaluate the profiles of MTF1 in pan-cancer. For example, TIMER2.0, TNMplot and GEPIA2.0 were employed to analyze the expression values of MTF1 in pan-cancer. The methylation levels of MTF1 were evaluated via UALCAN and DiseaseMeth version 2.0 databases. The mutation profiles of MTF1 in pan-cancers were analyzed using cBioPortal. GEPIA2.0, Kaplan-Meier plotter and cBioPortal were also used to explore the roles of MTF1 in cancer prognosis. We found that high MTF1 expression was related to poor prognosis of liver hepatocellular carcinoma (LIHC) and brain lower grade glioma (LGG). Also, high expression level of MTF1 was associated with good prognosis of kidney renal clear cell carcinoma (KIRC), lung cancer, ovarian cancer and breast cancer. We investigated the genetic alteration and methylation levels of MTF1 between the primary tumor and normal tissues. The relationship between MTF1 expression and several immune cells was analyzed, including T cell CD8 + and dendritic cells (DC). Mechanically, MTF1-interacted molecules might participate in the regulation of metabolism-related pathways, such as peptidyl-serine phosphorylation, negative regulation of cellular amide metabolic process and peptidyl-threonine phosphorylation. Single cell sequencing indicated that MTF1 was associated with angiogenesis, DNA repair and cell invasion. In addition, in vitro experiment indicated knockdown of MTF1 resulted in the suppressed cell proliferation, increased reactive oxygen species (ROS) and promoted cell death in LIHC cells HepG2 and Huh7. Taken together, this pan-cancer analysis of MTF1 has implicated that MTF1 could play an essential role in the progression of various human cancers.

Metallothionein-2: An emerging target in inflammatory diseases and cancers

Metallothionein-2 (MT-2) was originally discovered as a mediator of zinc homeostasis and cadmium detoxification. However, MT-2 has recently received increased attention because altered expression of MT-2 is closely related to various diseases such as asthma and cancers. Several pharmacological strategies have been developed to inhibit or modify MT-2, revealing its potential as drug target in diseases. Therefore, a better understanding of the mechanisms of MT-2 action is warranted to improve drug development for potential clinical applications. In this review, we highlight recent advances in determining the protein structure, regulation, binding partners, and new functions of MT-2 in inflammatory diseases and cancers.

Esterase D interacts with metallothionein 2A and inhibits the migration of A549 lung cancer cells in vitro

Esterase D (ESD) is a nonspecific esterase widely distributed in various organisms. ESD plays an important role in regulating cholesterol efflux, inhibiting viral replication and lung cancer growth. MT2A (metallothionein 2A) is the most important isoform of metallothionein (MTs) in human and high expression of MT2A in tumors represents poor prognosis and metastatic behavior. However, there are no reports about the molecular mechanism of ESD in the regulation of tumor metastasis. In this study, we found for the first time that activation ESD promoted its interaction with MT2A and decreased the protein level of MT2A, which resulting in the concentration of free zinc ions up-regulated, and inhibited the migration of A549 lung cancer cells in vitro.

Metallothionein-2A Protects Cardiomyocytes from Hypoxia/reper-Fusion through Inhibiting p38

The reperfusion of coronary artery blood supply is often accompanied by myocardial hypoxia/reperfusion (H/R) injury, and induced cardiomyocytes apoptosis. The activation of p38 can induce apoptosis, thereby aggravating the myocardial H/R injury. Metallothionein-2A (MT2A) has the functions of anti-apoptosis and protective effect through p38. However, it is not clear that MT2A may protect cardiomyocytes from H/R injury through p38 signaling pathway. Here, we constructed an H/R model for H9c2 cardiomyocytes to explore the protective effect of MT2A on cardiomyocytes apoptosis during the process of H/R through p38 signal pathway. The results revealed that both endogenously overexpressed MT2A and exogenously added MT2A can inhibit the active expression of p-p38 and cleaved caspase-3 under H/R. Based on our results, H/R induced cardiomyocytes apoptosis and activation of p38. And, MT2A can inhibit the active expression of caspase-3 and p38. We found that MT2A can protect cardiomyocytes apoptosis from H/R injury through p38 signaling pathway.

Single cell sequencing revealed the mechanism of PD-1 resistance affected by the expression profile of peripheral blood immune cells in ESCC

BACKGROUND

Esophageal squamous carcinoma (ESCC) is a highly lethal malignancy with poor prognosis. The effect of transcriptome characteristics of patient immune microenvironment (TME) on the efficacy of immunosuppressive agents is still poorly understood.

METHODS

Here we extracted and isolated immune cells from peripheral blood of patients with PD-1 monoclonal antibody sensitivity and resistance, and conducted deep single-cell RNA sequencing to describe the baseline landscape of the composition, lineage, and functional status of infiltrating immune cells in peripheral blood of patients with esophageal cancer.

RESULTS

The transcriptome characteristics of immune cells were comprehensively analyzed, and the dynamic changes of cell percentage, heterogeneity of cell subtypes and interactions between cells were explained. Co-expression and pedigree tracking based on T-cell antigen receptors revealed a significant proportion of highly migratory intertissue-effector T cells. GO and KEGG enrichment pathway Analysis of CD8+ effect-T cells ESCC_S group and ESCC_D1,2 group, found that in the up-regulated enrichment pathway, ESCC_S group enriched more PD-L1 and PD-1 checkpoint pathways expressed in tumors (JUN/NFKBIA/FOS/KRAS/IFNG), which also exist in T cell receptor signaling pathways. MT2A, MT1X and MT1E were differentially expressed in ESCC patients with PD-1 monoclonal antibody resistance, which may be related to the resistance of PD-1 mMAB.

CONCLUSIONS

This study has an in-depth understanding of the influence of peripheral immune cell infiltration on the sensitivity of monoclonal antibody PD-1 in patients with esophageal cancer, which is helpful to promote the immunotherapy of patients with esophageal cancer.

Blood RNA Sequencing Indicates Upregulated BATF2 and LY6E and Downregulated ISG15 and MT2A Expression in Children with Autism Spectrum Disorder

Mutations in over 100 genes are implicated in autism spectrum disorder (ASD). DNA SNPs, CNVs, and epigenomic modifications also contribute to ASD. Transcriptomics analysis of blood samples may offer clues for pathways dysregulated in ASD. To expand and validate published findings of RNA-sequencing (RNA-seq) studies, we performed RNA-seq of whole blood samples from an Israeli discovery cohort of eight children with ASD compared with nine age- and sex-matched neurotypical children. This revealed 10 genes with differential expression. Using quantitative real-time PCR, we compared RNAs from whole blood samples of 73 Israeli and American children with ASD and 26 matched neurotypical children for the 10 dysregulated genes detected by RNA-seq. This revealed higher expression levels of the pro-inflammatory transcripts BATF2 and LY6E and lower expression levels of the anti-inflammatory transcripts ISG15 and MT2A in the ASD compared to neurotypical children. BATF2 was recently reported as upregulated in blood samples of Japanese adults with ASD. Our findings support an involvement of these genes in ASD phenotypes, independent of age and ethnicity. Upregulation of BATF2 and downregulation of ISG15 and MT2A were reported to reduce cancer risk. Implications of the dysregulated genes for pro-inflammatory phenotypes, immunity, and cancer risk in ASD are discussed.

XAF1 drives apoptotic switch of endoplasmic reticulum stress response through destabilization of GRP78 and CHIP

X-linked inhibitor of apoptosis-associated factor-1 (XAF1) is a stress-inducible tumor suppressor that is commonly inactivated in many human cancers. Despite accumulating evidence for the pro-apoptotic role for XAF1 under various stressful conditions, its involvement in endoplasmic reticulum (ER) stress response remains undefined. Here, we report that XAF1 increases cell sensitivity to ER stress and acts as a molecular switch in unfolded protein response (UPR)-mediated cell-fate decisions favoring apoptosis over adaptive autophagy. Mechanistically, XAF1 interacts with and destabilizes ER stress sensor GRP78 through the assembly of zinc finger protein 313 (ZNF313)-mediated destruction complex. Moreover, XAF1 expression is activated through PERK-Nrf2 signaling and destabilizes C-terminus of Hsc70-interacting protein (CHIP) ubiquitin E3 ligase, thereby blocking CHIP-mediated K63-linked ubiquitination and subsequent phosphorylation of inositol-required enzyme-1α (IRE1α) that is involved in in the adaptive ER stress response. In tumor xenograft assays, XAF1^-/- tumors display substantially lower regression compared to XAF1^+/+ tumors in response to cytotoxic dose of ER stress inducer. XAF1 and GRP78 expression show an inverse correlation in human cancer cell lines and primary breast carcinomas. Collectively this study uncovers an important role for XAF1 as a linchpin to govern the sensitivity to ER stress and the outcomes of UPR signaling, illuminating the mechanistic consequence of XAF1 inactivation in tumorigenesis.

Construction of miRNA-lncRNA-mRNA co-expression network affecting EMT-mediated cisplatin resistance in ovarian cancer

Platinum resistance is one of the major concerns in ovarian cancer treatment. Recent evidence shows the critical role of epithelial-mesenchymal transition (EMT) in this resistance. Epithelial-like ovarian cancer cells show decreased sensitivity to cisplatin after cisplatin treatment. Our study prospected the association between epithelial phenotype and response to cisplatin in ovarian cancer. Microarray dataset GSE47856 was acquired from the GEO database. After identifying differentially expressed genes (DEGs) between epithelial-like and mesenchymal-like cells, the module identification analysis was performed using weighted gene co-expression network analysis (WGCNA). The gene ontology (GO) and pathway analyses of the most considerable modules were performed. The protein-protein interaction network was also constructed. The hub genes were specified using Cytoscape plugins MCODE and cytoHubba, followed by the survival analysis and data validation. Finally, the co-expression of miRNA-lncRNA-TF with the hub genes was reconstructed. The co-expression network analysis suggests 20 modules relating to the Epithelial phenotype. The antiquewhite4, brown and darkmagenta modules are the most significant non-preserved modules in the Epithelial phenotype and contain the most differentially expressed genes. GO, and KEGG pathway enrichment analyses on these modules divulge that these genes were primarily enriched in the focal adhesion, DNA replication pathways and stress response processes. ROC curve and overall survival rate analysis show that the co-expression pattern of the brown module's hub genes could be a potential prognostic biomarker for ovarian cancer cisplatin resistance.

Cytosolic microRNA-inducible nuclear translocation of Cas9 protein for disease-specific genome modification

MicroRNA-dependent mRNA decay plays an important role in gene silencing by facilitating posttranscriptional and translational repression. Inspired by this intrinsic nature of microRNA-mediated mRNA cleavage, here, we describe a microRNA-targeting mRNA as a switch platform called mRNA bridge mimetics to regulate the translocation of proteins. We applied the mRNA bridge mimetics platform to Cas9 protein to confer it the ability to translocate into the nucleus via cleavage of the nuclear export signal. This system performed programmed gene editing in vitro and in vivo. Combinatorial treatment with cisplatin and miR-21-EZH2 axis-targeting CRISPR Self Check-In improved sensitivity to chemotherapeutic drugs in vivo. Using the endogenous microRNA-mediated mRNA decay mechanism, our platform is able to remodel a cell's natural biology to allow the entry of precise drugs into the nucleus, devoid of non-specific translocation. The mRNA bridge mimetics strategy is promising for applications in which the reaction must be controlled via intracellular stimuli and modulates Cas9 proteins to ensure safe genome modification in diseased conditions.

Zinc ions negatively regulate proapoptotic signaling in cells expressing oncogenic mutant Ras

Mutational activation of the Ras family of proto-oncogenes promotes cell survival and proliferation. Studies using cells cultured in vitro have shown that ectopic expression of constitutively active Ras suppresses apoptosis induced by serum deprivation. However, in some cellular contexts, constitutively active Ras exerts the opposite effects, including apoptosis of serum-starved embryonic fibroblasts. Such observations first came over two decades ago, but the molecular mechanisms by which mutant Ras increases the susceptibility of cells to serum deprivation leading to apoptosis are still not fully understood. To revisit this issue, I investigate the effects of serum depletion and mutant Ras expression on intracellular signaling and transcriptome of cells carrying an inducible allele of constitutively active mutant Hras (Hras^G12V). I identify zinc ions (Zn²⁺) as a serum factor that suppresses proapoptotic signaling in cells expressing Hras^G12V. Mechanistically, Hras^G12V expression along with Zn²⁺ deficiency activates c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), which are required for caspase-3 activation involved in the induction of cell death. Transcriptome analyses suggest that Hras^G12V induces the unfolded protein response (UPR). Further analyses of intracellular signaling biomolecules related to the UPR indicate that Hras^G12V activates inositol-requiring protein 1 (IRE1), which synergizes with Zn²⁺ deficiency to activate JNK and p38 MAPK signaling. These results provide insights into a role of Zn²⁺ that counteracts proapoptotic signaling activated by mutationally activated Ras.

XAF1 directs glioma response to temozolomide through apoptotic transition of autophagy by activation of ROS-ATM-AMPK signaling

Background

X-linked inhibitor of apoptosis-associated factor 1 (XAF1) is a tumor suppressor that is commonly inactivated in multiple human cancers. However, its role in the pathogenesis and therapeutic response of glioma is poorly characterized.

Methods

XAF1 activation by temozolomide (TMZ) and its effect on TMZ cytotoxicity were defined using luciferase reporter, flow cytometry, and immunofluorescence assays. Signaling mechanism was analyzed using genetic and pharmacologic experiments. In vivo studies were performed in mice to validate the role of XAF1 in TMZ therapy.

Results

Epigenetic alteration of XAF1 is frequent in cell lines and primary tumors and contributes to cancer cell growth. XAF1 transcription is activated by TMZ via JNK-IRF-1 signaling to promote apoptosis while it is impaired by promoter hypermethylation. In tumor cells expressing high O 6methylguanineDNA methyltransferase (MGMT), XAF1 response to TMZ is debilitated. XAF1 facilitates TMZ-mediated autophagic flux to direct an apoptotic transition of protective autophagy. Mechanistically, XAF1 is translocated into the mitochondria to stimulate reactive oxygen species (ROS) production and ataxia telangiectasia mutated (ATM)-AMPactivated protein kinase (AMPK) signaling. A mutant XAF1 lacking the zinc finger 6 domain fails to localize in the mitochondria and activate ROS-ATMAMPK signaling and autophagy-mediated apoptosis. XAF1restored xenograft tumors display a reduced growth rate and enhanced therapeutic response to TMZ, which is accompanied with activation of ATMAMPK signaling. XAF1 expression is associated with overall survival of TMZ treatment patients, particularly with low MGMT cancer.

Conclusions

This study uncovers an important role for the XAF1ATMAMPK axis as a linchpin to govern glioma response to TMZ therapy.

Functional Analysis of the Promoter Regions of Two Apoptosis-Related Genes (Bcl-2 and Cycs) and Their Regulation by Zn in Yellow Catfish

B-cell lymphoma 2 (Bcl-2) and cytochrome c (Cycs) are two important proteins relevant to cellular apoptosis. In this study, we characterized the functions of the promoter regions of two apoptosis-related genes, Bcl-2 and Cycs, in yellow catfish Pelteobagrus fulvidraco. We obtained a 1989 bp Bcl-2 promoter and an 1830 bp Cycs promoter and predicted several key transcription factor binding sites (TFBSs) on the promoters, such as Kruppel-like factor 4 (KLF4), signal transducer and activator of transcription factor 3 (STAT3), forkhead box O (FOXO), metal-responsive element (MRE) and hepatocyte nuclear factor 1α (HNF-1α). Zinc (Zn) increased the activities of the Bcl-2 promoter but decreased the activities of the Cycs promoter. Metal-responsive transcription factor 1 (MTF-1) and HNF-1α directly bound with Bcl-2 and Cycs promoters, and they positively regulated the activity of the Bcl-2 promoter but negatively regulated the activity of the Cycs promoter. Zn promoted the binding ability of HNF-1α to the Bcl-2 promoter but decreased its binding ability to the Cycs promoter. However, Zn had no significant effect on the binding capability of MTF-1 to the regions of Bcl-2 and Cycs promoters. Zn upregulated the mRNA and total protein expression of Bcl-2 but downregulated the mRNA and total protein expression of Cycs. At the same time, Annexin V-FITC/PI staining showed that Zn significantly reduced the apoptosis of primary hepatocytes. For the first time, our study provides evidence for the MRE and HNF-1α response elements on the Bcl-2 and Cycs promoters, offering new insight into the mechanism by which Zn affects apoptosis in vertebrates.

Integrative Analysis of Metallothioneins Identifies MT1H as Candidate Prognostic Biomarker in Hepatocellular Carcinoma

Background: Metallothioneins (MTs) play crucial roles in the modulation of zinc/copper homeostasis, regulation of neoplastic growth and proliferation, and protection against apoptosis. The present study attempted to visualize the prognostic landscape of MT functional isoforms and identify potential prognostic biomarkers in hepatocellular carcinoma (HCC). Methods: The transcriptional expression, comprehensive prognostic performances, and gene-gene interaction network of MT isoforms in HCC were evaluated via Oncomine, GEPIA, Kaplan-Meier plotter, and GeneMANIA databases. Characterized by good prognostic value in three external cohorts, MT1H was specifically selected as a potential prognostic biomarker in HCC with various clinicopathological features. Functional and pathway enrichment analyses of MT1H status were performed using cBioPortal, the Database for Annotation, Visualization, and Integrated Discovery (DAVID), and ssGSVA method. Results: MT1E/1F/1G/1H/1M/1X/2A was greatly downregulated in HCC. Prognostic analyses elucidated the essential correlations between MT1A/1B/1H/1X/2A/4 attenuation and poor overall survival, between MT1B/1H/4 downregulation and worse relapse-free survival, and between MT1A/1B/1E/1H/1M/2A/4 downregulation and diminished progression-free survival in HCC. Taken together, these results indicated the powerful prognostic value of MT1H among MTs in HCC. In-depth analyses suggested that MT1H may be more applicable to alcohol-derived HCC and involved in the downregulation of the inflammatory pathway, Jak-STAT pathway, TNF pathway, and Wnt signaling pathway. Conclusion: MT-specific isoforms displayed aberrant expression and varying prognostic value in HCC. MT1H repression in HCC was multi-dimensionally detrimental to patient outcomes. Therefore, MT1H was possibly associated with carcinogenesis and exploited as a novel prognostic biomarker and candidate therapeutic target for HCC.

Cadmium-stimulated invasion of rat liver cells during malignant transformation: Evidence of the involvement of oxidative stress/TET1-sensitive machinery

Cadmium (Cd) is recognized as a highly toxic heavy metal for humans in part because it is a multi-organ carcinogen. To clarify the mechanism of Cd carcinogenicity, we have established an experimental system using rat liver TRL1215 cells exposed to 2.5 μM Cd for 10 weeks and then cultured in Cd-free medium for an additional 4 weeks (total 14 weeks). Recently, we demonstrated, by using this experimental system, that 1) Cd stimulates cell invasion by suppression of apolipoprotein E (ApoE) expression, and 2) Cd induces DNA hypermethylation of the regulatory region of the ApoE gene. However, the underlying mechanism(s) as well as other potential genetic participants in the Cd-stimulated invasion are undefined. In the present work, we found that concurrent with enhanced invasion, Cd induced oxidative stress, coupled with the production of oxidative stress-sensitive metallothionein 2A (MT2A), which lead to down-modulation of ten-eleven translocation methylcytosine dioxygenase 1 (TET1: DNA demethylation) in addition to ApoE, without impacting DNA methyltransferases (DNMTs: DNA methylation) levels. Furthermore, the expression of tissue inhibitor of metalloproteinase 2 and 3 (TIMP2 and TIMP3) that are positively regulated by TET1, were decreased by Cd. The genes (ApoE/TET1/TIMP2/TIMP3) suppressed by Cd were further suppressed by hydroquinone (HQ; a reactive oxygen species [ROS] producer), whereas N-acetyl-l-cysteine (NAC; a ROS scavenger) prevented the suppression of their expression by HQ. In addition, NAC reversed their expression suppressed by Cd. Cd-stimulated cell invasion was clearly dampened by NAC in a concentration-dependent manner. Overall these findings suggest that 1) altered TET1 expression and activity together with ApoE are likely involved in the enhanced invasiveness due to Cd exposure, and 2) Cd down-regulation of TET1 likely evokes a reduction in ApoE expression (possible by DNA hypermethylation), and 3) anti-oxidants are effective in abrogation of the enhanced invasiveness that occurs concurrently with Cd-induced malignant transformation.

XAF1 as a modifier of p53 function and cancer susceptibility

Cancer risk is highly variable in carriers of the common TP53-R337H founder allele, possibly due to the influence of modifier genes. Whole-genome sequencing identified a variant in the tumor suppressor XAF1 (E134*/Glu134Ter/rs146752602) in a subset of R337H carriers. Haplotype-defining variants were verified in 203 patients with cancer, 582 relatives, and 42,438 newborns. The compound mutant haplotype was enriched in patients with cancer, conferring risk for sarcoma (P = 0.003) and subsequent malignancies (P = 0.006). Functional analyses demonstrated that wild-type XAF1 enhances transactivation of wild-type and hypomorphic TP53 variants, whereas XAF1-E134* is markedly attenuated in this activity. We propose that cosegregation of XAF1-E134* and TP53-R337H mutations leads to a more aggressive cancer phenotype than TP53-R337H alone, with implications for genetic counseling and clinical management of hypomorphic TP53 mutant carriers.

Subendothelial stiffness alters endothelial cell traction force generation while exerting a minimal effect on the transcriptome

Endothelial cells respond to changes in subendothelial stiffness by altering their migration and mechanics, but whether those responses are due to transcriptional reprogramming remains largely unknown. We measured traction force generation and also performed gene expression profiling for two endothelial cell types grown in monolayers on soft or stiff matrices: primary human umbilical vein endothelial cells (HUVEC) and immortalized human microvascular endothelial cells (HMEC-1). Both cell types respond to changes in subendothelial stiffness by increasing the traction stresses they exert on stiffer as compared to softer matrices, and exhibit a range of altered protein phosphorylation or protein conformational changes previously implicated in mechanotransduction. However, the transcriptome has only a minimal role in this conserved biomechanical response. Only few genes were differentially expressed in each cell type in a stiffness-dependent manner, and none were shared between them. In contrast, thousands of genes were differentially regulated in HUVEC as compared to HMEC-1. HUVEC (but not HMEC-1) upregulate expression of TGF-β2 on stiffer matrices, and also respond to application of exogenous TGF-β2 by enhancing their endogenous TGF-β2 expression and their cell-matrix traction stresses. Altogether, these findings provide insights into the relationship between subendothelial stiffness, endothelial mechanics and variation of the endothelial cell transcriptome, and reveal that subendothelial stiffness, while critically altering endothelial cells’ mechanical behavior, minimally affects their transcriptome.

YY1 negatively regulates the XAF1 gene expression in prostate cancer

XAF1 is a tumor suppressor gene with low or absent expression in cancer. Since transcriptional reactivation or ectopic-mediated expression of XAF1 inhibits tumor growth, it is of great interest to elucidate the molecular mechanisms leading to XAF1 silencing. YY1 is a transcription factor that acts as a repressor or an activator to modulate several cancer-associated cellular processes. Both YY1 and XAF1 have key roles in prostate cancer (PCa) progression and are associated with worse clinical outcomes. To assess whether YY1 regulates the transcriptional activation of the XAF1 gene, we performed gene-reporter assays coupled with site-directed mutagenesis, which showed that YY1 is able to mediate XAF1 silencing. Concordantly, ChIP-qPCR assays showed that YY1 interacts with the XAF1 promoter in PC3 cells that lacks XAF1 expression. This association was lost after exposure to epigenetic modulators that induce XAF1 expression. Further supporting the YY1's repressive role, we found transcriptional reactivation of the XAF1 gene by YY1 downregulation. As expected by previous reports showing that HDAC1 is needed for YY1-mediated repressive actions, we observed XAF1 re-expression after either inhibition or downregulation of the HDAC1 gene. Finally, expression data retrieved from the TCGA consortium showed that PCa samples presented lower XAF1 and higher HDAC expression levels than normal tissues. Thus, our results support a model in which YY1 is able to silence tumor suppressor genes such as XAF1 through HDAC1 in PCa.

XAF1 forms a positive feedback loop with IRF-1 to drive apoptotic stress response and suppress tumorigenesis

X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1) is a proapoptotic tumor suppressor that is frequently inactivated in multiple human cancers. However, the molecular basis for the XAF1-mediated growth inhibition remains largely undefined. Here, we report that XAF1 forms a positive feedback loop with interferon regulatory factor-1 (IRF-1) and functions as a transcriptional coactivator of IRF-1 to suppress tumorigenesis. Under various stressful conditions, XAF1 transcription is activated by IRF-1, and elevated XAF1 stabilizes and activates IRF-1. Mechanistically, XAF1 binds to the multifunctional domain 2 of IRF-1 via the zinc finger domain 6, thereby hindering C-terminus of Hsc70-interacting protein (CHIP) interaction with and ubiquitination of IRF-1. Activation of the IRF-1−XAF1 loop greatly increases stress-induced apoptosis and decreases the invasive capability of tumor cells. Oncogenic Ras and growth factors interfere with the IRF-1−XAF1 interplay via Erk-mediated repression of XAF1 transcription. Furthermore, XAF1 enhances IRF-1-mediated transcription of proapoptotic genes via the XAF1-IRF-1 complex formation on these target promoters. Meanwhile, XAF1 inhibits NF-κB-mediated tumor cell malignancy by reinforcing IRF-1 binding to a subset of coregulated promoters. Expression levels of IRF-1 and XAF1 correlate tightly in both cancer cell lines and primary tumors, and XAF1-induced tumor regression is markedly attenuated in IRF-1-depleted tumors. Collectively, this study identifies a novel mechanism of XAF1-mediated tumor suppression, uncovering XAF1 as a feedback coactivator of IRF-1 under stressful conditions.

An insight into the complex roles of metallothioneins in malignant diseases with emphasis on (sub)isoforms/isoforms and epigenetics phenomena

Metallothioneins (MTs) belong to a group of small cysteine-rich proteins that are ubiquitous throughout all kingdoms. The main function of MTs is scavenging of free radicals and detoxification and homeostating of heavy metals. In humans, 16 genes localized on chromosome 16 have been identified to encode four MT isoforms labelled by numbers (MT-1-MT-4). MT-2, MT-3 and MT-4 proteins are encoded by a single gene. MT-1 comprises many (sub)isoforms. The known active MT-1 genes are MT-1A, -1B, -1E, -1F, -1G, -1H, -1M and -1X. The rest of the MT-1 genes (MT-1C, -1D, -1I, -1J and -1L) are pseudogenes. The expression and localization of individual MT (sub)isoforms and pseudogenes vary at intra-cellular level and in individual tissues. Changes in MT expression are associated with the process of carcinogenesis of various types of human malignancies, or with a more aggressive phenotype and therapeutic resistance. Hence, MT (sub)isoform profiling status could be utilized for diagnostics and therapy of tumour diseases. This review aims on a comprehensive summary of methods for analysis of MTs at (sub)isoforms levels, their expression in single tumour diseases and strategies how this knowledge can be utilized in anticancer therapy.