Zinc finger protein 280C contributes to colorectal tumorigenesis by maintaining epigenetic repression at H3K27me3-marked loci.

Dysregulated epigenetic and transcriptional programming due to abnormalities of transcription factors (TFs) contributes to and sustains the oncogenicity of cancer cells. Here, we unveiled the role of zinc finger protein 280C (ZNF280C), a known DNA damage response protein, as a tumorigenic TF in colorectal cancer (CRC), required for colitis-associated carcinogenesis and Apc deficiency­driven intestinal tumorigenesis in mice. Consistently, ZNF280C silencing in human CRC cells inhibited proliferation, clonogenicity, migration, xenograft growth, and liver metastasis. As a C2H2 (Cys2-His2) zinc finger-containing TF, ZNF280C occupied genomic intervals with both transcriptionally active and repressive states and coincided with CCCTC-binding factor (CTCF) and cohesin binding. Notably, ZNF280C was crucial for the repression program of trimethylation of histone H3 at lysine 27 (H3K27me3)-marked genes and the maintenance of both focal and broad H3K27me3 levels. Mechanistically, ZNF280C counteracted CTCF/cohesin activities and condensed the chromatin environment at the cis elements of certain tumor suppressor genes marked by H3K27me3, at least partially through recruiting the epigenetic repressor structural maintenance of chromosomes flexible hinge domain-containing 1 (SMCHD1). In clinical relevance, ZNF280C was highly expressed in primary CRCs and distant metastases, and a higher ZNF280C level independently predicted worse prognosis of CRC patients. Thus, our study uncovered a contributor with good prognostic value to CRC pathogenesis and also elucidated the essence of DNA-binding TFs in orchestrating the epigenetic programming of gene regulation.

BIX-01294 enhances the effect of chemotherapy on colorectal cancer by inhibiting the expression of stemness genes.

During the development of colorectal cancer, tumor cells will generate some cancer stem cells with self-renewal ability because they adapt to the environment. Therefore, in the treatment of colorectal cancer, it has certain potential clinical application value to effectively inhibit cancer stem cells. A small molecule EHMT-2 inhibitor, BIX-01294, was evaluated for its activity in inhibiting cancer stem cells in human colorectal cancer by in vitro and in vivo experiments. Transcriptome analysis was performed on BIX-01294 treated cells for holistic analysis to elucidate how BIX-01294 inhibits the expression of genes related to cancer stem cells. The results show that BIX-01294 significantly inhibited the proliferative phenotype of human colorectal cancer in vivo and in vitro, reduced the proportion of cancer stem cells, and inhibited some stemness-related gene. Morever, it is synergistic with 5-fluorouracil in inhibiting the proliferation of colorectal cancer. In summary, EHMT-2 is a novel target of anti-tumor drugs. The combination of BIX-01294 and 5-fluorouracil has a synergistic therapeutic effect on human colorectal cancer.

AQP1 suppression by ATF4 triggers trabecular meshwork tissue remodelling in ET-1-induced POAG.

Primary open-angle glaucoma (POAG) is the second leading cause of irreversible blindness worldwide. Increased endothelin-1 (ET-1) has been observed in aqueous humour (AH) of POAG patients, resulting in an increase in the out-flow resistance of the AH. However, the underlining mechanisms remain elusive. Using established in vivo and in vitro POAG models, we demonstrated that water channel Aquaporin 1 (AQP1) is down-regulated in trabecular meshwork (TM) cells upon ET-1 exposure, which causes a series of glaucomatous changes, including actin fibre reorganization, collagen production, extracellular matrix deposition and contractility alteration of TM cells. Ectopic expression of AQP1 can reverse ET-1-induced TM tissue remodelling, which requires the presence of ß-catenin. More importantly, we found that ET-1-induced AQP1 suppression is mediated by ATF4, a transcription factor of the unfolded protein response, which binds to the promoter of AQP1 and negatively regulates AQP1 transcription. Thus, we discovered a novel function of ATF4 in controlling the process of TM remodelling in ET-1-induced POAG through transcription suppression of AQP1. Our findings also detail a novel pathological mechanism and a potential therapeutic target for POAG.

The epigenetic modifier PBRM1 restricts the basal activity of the innate immune system by repressing retinoic acid-inducible gene-I-like receptor signalling and is a potential prognostic biomarker for colon cancer.

It has long been known that patients suffering from inflammatory bowel disease (IBD) have an increased risk of developing colorectal cancer (CRC). The innate immune system of host cells provides a first-line defence against pathogenic infection, whereas an uncontrolled inflammatory response under homeostatic conditions usually leads to pathological consequences, as exemplified by the chronic inflammation of IBD. The key molecules and pathways keeping innate immunity in check are still poorly defined. Here, we report that the chromatin remodeller polybromo-1 (PBRM1) is a repressor of innate immune signalling mediated by retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs). Knockdown of PBRM1 in colon cancer cells increased the expression of two receptor genes (RIG-I and MDA5) and upregulated interferon (IFN)-related and inflammation-related gene signatures. The innate immune signal stimulated by a double-stranded RNA viral mimic was exaggerated by PBRM1 suppression. PBRM1 cooperated with polycomb protein EZH2 to directly bind the cis-regulatory elements of RIG-I and MDA5, thereby suppressing their transcription. Moreover, upregulation of RIG-I and MDA5 is required for IFN response activation induced by PBRM1 silencing. TRIM25, a protein stimulated by the RLR pathway and IFN production, physically interacted with PBRM1 and induced PBRM1 protein destabilization by promoting its ubiquitination. These findings reveal a PBRM1-RLR regulatory circuit that can keep innate immune activity at a minimal level in resting cells, and also ensure a robust inflammatory response in the case of pathogen invasion. PBRM1 was found to be downregulated in primary tissues from patients with CRC or IBD, and its expression correlated negatively with that of RLR genes and interferon-stimulated genes in CRC samples. Lower PBRM1 expression was associated with advanced pathological grade and poorer survival of CRC patients, indicating that PBRM1 could serve as a potential prognostic biomarker for CRC. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

EBT: a statistic test identifying moderate size of significant features with balanced power and precision for genome-wide rate comparisons.

MOTIVATION: In genome-wide rate comparison studies, there is a big challenge for effective identification of an appropriate number of significant features objectively, since traditional statistical comparisons without multi-testing correction can generate a large number of false positives while multi-testing correction tremendously decreases the statistic power. RESULTS: In this study, we proposed a new exact test based on the translation of rate comparison to two binomial distributions. With modeling and real datasets, the exact binomial test (EBT) showed an advantage in balancing the statistical precision and power, by providing an appropriate size of significant features for further studies. Both correlation analysis and bootstrapping tests demonstrated that EBT is as robust as the typical rate-comparison methods, e.g. χ 2 test, Fisher's exact test and Binomial test. Performance comparison among machine learning models with features identified by different statistical tests further demonstrated the advantage of EBT. The new test was also applied to analyze the genome-wide somatic gene mutation rate difference between lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), two main lung cancer subtypes and a list of new markers were identified that could be lineage-specifically associated with carcinogenesis of LUAD and LUSC, respectively. Interestingly, three cilia genes were found selectively with high mutation rates in LUSC, possibly implying the importance of cilia dysfunction in the carcinogenesis. AVAILABILITY AND IMPLEMENTATION: An R package implementing EBT could be downloaded from the website freely: http://www.szu-bioinf.org/EBT . CONTACT: wangyj@szu.edu.cn. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

A global survey of bacterial type III secretion systems and their effectors.

The type III secretion system (T3SS) is an important genetic determinant that mediates interactions between Gram-negative bacteria and their eukaryotic hosts. Our understanding of the T3SS continues to expand, yet the availability of new bacterial genomes prompts questions about its diversity, distribution and evolution. Through a comprehensive survey of ∼20 000 bacterial genomes, we identified 174 non-redundant T3SSs from 109 genera and 5 phyla. Many of the bacteria are environmental strains that have not been reported to interact with eukaryotic hosts, while several species groups carry multiple T3SSs. Four ultra-conserved Microsynteny Blocks (MSBs) were defined within the T3SSs, facilitating comprehensive clustering of the T3SSs into 13 major categories, and establishing the largest diversity of T3SSs to date. We subsequently extended our search to identify type III effectors, resulting in 8740 candidate effectors. Lastly, an analysis of the key transcriptional regulators and circuits for the T3SS families revealed that low-level T3SS regulators were more conserved than higher-level regulators. This comprehensive analysis of the T3SSs and their protein effectors provides new insight into the diversity of systems used to facilitate host-bacterial interactions.

Epigenetic identification of receptor tyrosine kinase-like orphan receptor 2 as a functional tumor suppressor inhibiting ß-catenin and AKT signaling but frequently methylated in common carcinomas.

Through subtraction of tumor-specific CpG methylation, we identified receptor tyrosine kinase-like orphan receptor 2 (ROR2) as a candidate tumor suppressor gene (TSG). ROR2 is a specific receptor or co-receptor for WNT5A, involved in canonical and non-canonical WNT signaling, with its role in tumorigenesis controversial. We characterized its functions and related cell signaling in common carcinomas. ROR2 was frequently silenced by promoter CpG methylation in multiple carcinomas including nasopharyngeal, esophageal, gastric, colorectal, hepatocellular, lung, and breast cancers, while no direct correlation of ROR2 and WNT5A expression was observed. Ectopic expression of ROR2 resulted in tumor suppression independent of WNT5A status, through inhibiting tumor cell growth and inducing cell cycle arrest and apoptosis. ROR2 further suppressed epithelial-mesenchymal transition and tumor cell stemness through repressing ß-catenin and AKT signaling, leading to further inhibition of tumor cell migration/invasion and increased chemo-sensitivity. Thus ROR2, as an epigenetically inactivated TSG, antagonizes both ß-catenin and AKT signaling in multiple tumorigenesis. Its epigenetic silencing could be a potential tumor biomarker and therapeutic target for carcinomas.

Protocadherin 17 acts as a tumour suppressor inducing tumour cell apoptosis and autophagy, and is frequently methylated in gastric and colorectal cancers.

Gastric and colorectal cancers are among the most common cancers worldwide and cause serious cancer mortality. Both epigenetic and genetic disruptions of tumour suppressor genes (TSGs) are frequently involved in their pathogenesis. Here, we studied the epigenetic and genetic alterations of a novel TSG-PCDH17 and its functions in the pathogenesis of these tumours. We found that PCDH17 was frequently silenced and methylated in almost all gastric and colorectal tumour cell lines as well as in ∼95% of primary tumours, but not in normal gastric and colonic mucosa. Moreover, its deletion was detected in only 18% of gastric and 12% of colorectal cancer tissues, suggesting that epigenetic and genetic inactivation of PCDH17 are both involved in gastric and colorectal tumourigenesis. PCDH17 protein expression was significantly correlated with low tumour stage and less lymph node metastasis of gastric and colorectal cancer patients, indicating its potential as a tumour marker. Restoring PCDH17 expression inhibited tumour cell growth in vitro and in vivo through promoting apoptosis, as evidenced by increased TUNEL staining and caspase-3 activation. Furthermore, PCDH17-induced autophagy, along with increased numbers of autophagic vacuoles and up-regulated autophagic proteins Atg-5, Atg-12 and LC3B II. Thus, PCDH17 acts as a tumour suppressor, exerting its anti-proliferative activity through inducing apoptosis and autophagy, and is frequently silenced in gastric and colorectal cancers. PCDH17 methylation is a tumour-specific event that could serve as an epigenetic biomarker for these tumours.

Targeting the Epigenetic Reader ENL Inhibits Super-Enhancer-Driven Oncogenic Transcription and Synergizes with BET Inhibition to Suppress Tumor Progression.

Epigenetic alterations at cis-regulatory elements (CRE) fine-tune transcriptional output. Epigenetic readers interact with CREs and can cooperate with other chromatin regulators to drive oncogene transcription. Here, we found that the YEATS domain-containing histone acetylation reader ENL (eleven-nineteen leukemia) acts as a key regulator of super-enhancers (SE), which are highly active distal CREs, across cancer types. ENL occupied the majority of SEs with substantially higher preference over typical enhancers, and the enrichment of ENL at SEs depended on its ability to bind acetylated histones. Rapid depletion of ENL by auxin-inducible degron tagging severely repressed the transcription of SE-controlled oncogenes, such as MYC, by inducing the decommissioning of their SEs, and restoring ENL protein expression largely reversed these effects. Additionally, ENL was indispensable for the rapid activation of SE-regulated immediate early genes in response to growth factor stimulation. Furthermore, ENL interacted with the histone chaperone FACT complex and was required for the deposition of FACT over CREs, which mediates nucleosome reorganization required for transcription initiation and elongation. Proper control of transcription by ENL and ENL-associated FACT was regulated by the histone reader BRD4. ENL was overexpressed in colorectal cancer and functionally contributed to colorectal cancer growth and metastasis. ENL degradation or inhibition synergized with BET inhibitors that target BRD4 in restraining colorectal cancer progression. These findings establish the essential role of epigenetic reader ENL in governing SE-driven oncogenic transcription and uncover the potential of ENL intervention to increase sensitivity to BET inhibition. SIGNIFICANCE: ENL plays a key role in decoding epigenetic marks at highly active oncogenic super-enhancers and can be targeted in combination with BET inhibition as a promising synergistic strategy for optimizing cancer treatment.

FEZF2, a novel 3p14 tumor suppressor gene, represses oncogene EZH2 and MDM2 expression and is frequently methylated in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus-associated tumor prevalent in southern China and southeast Asia, with the 3p14-p12 locus reported as a critical tumor suppressor gene (TSG) region during its pathogenesis. We identified a novel 3p14.2 TSG, FEZF2 (FEZ family zinc finger 2), for NPC. FEZF2 is readily expressed in normal tissues including upper respiratory epithelium, testis, brain and ovary tissues, as well as in immortalized nasopharyngeal epithelial cell line NP69, but it is completely silenced in NPC cell lines due to CpG methylation of its promoter, although no homozygous deletion of FEZF2 was detected. 5-Aza-2'-deoxycytidine treatment restored FEZF2 expression in NPC cell lines along with its promoter demethylation. FEZF2 was frequently downregulated in NPC tumors, with promoter methylation detected in 75.5% of tumors, but only in 7.1% of normal nasopharyngeal tissues. Restored FEZF2 expression suppressed NPC cell clonogenicity through inducing G2/M cell cycle arrest and apoptosis and also inhibited NPC cell migration and stemness. FEZF2 acted as a histone deacetylase-associated repressor downregulating multiple oncogenes including EZH2 and MDM2, through direct binding to their promoters. Concomitantly, overexpression of EZH2 was frequently detected in NPC tumors. Thus, we have identified FEZF2 as a novel 3p14.2 TSG frequently inactivated by promoter methylation in NPC, which functions as a repressor downregulating multiple oncogene expression.

DACT1, an antagonist to Wnt/ß-catenin signaling, suppresses tumor cell growth and is frequently silenced in breast cancer.

INTRODUCTION: Aberrant activation of Wnt/ß-catenin signaling plays an important role in the pathogenesis of breast cancer. DACT1 (Dapper/Frodo) has been identified as involved in antagonizing Wnt/ß-catenin signaling through interacting with Dishevelled (Dvl), a central mediator of Wnt signaling, whereas its role in breast tumorigenesis remains unclear. METHODS: We examined DACT1 expression in breast cancer cell lines and primary tumors with semiquantitative or quantitative RT-PCR and immunochemistry, and further evaluated the promoter methylation of DACT1 with methylation-specific PCR (MSP). We also explored the tumor-suppressive functions of DACT1 in vivo and in vitro, and its related mechanism in breast cancer. RESULTS: We identified DACT1 as a methylated target in our breast cancer epigenome study. Here, we further investigated DACT1 expression in multiple breast cell lines and primary tumors, and further studied its function and molecular mechanisms. We found that DACT1 expression was silenced in eight (88.9%) of nine breast cancer cell lines, and its protein levels were obviously reduced in breast tumors compared with paired surgical-margin tissues. Promoter CpG methylation of DACT1 was detected in five (55.6%) of nine breast cancer cell lines and 40 (29.9%) of 134 primary tumors, but not in surgical-margin tissues and normal breast tissues. Demethylation treatment of breast cancer cell lines restored DACT1 expression along with promoter demethylation, suggesting that an epigenetic mechanism mediates DACT1 silencing in breast cancer. Functional assays showed that ectopic expression of DACT1 could inhibit breast tumor cell proliferation in vivo and in vitro through inducing apoptosis, and further suppress tumor cell migration through antagonizing the Wnt/ß-catenin signaling pathway. CONCLUSIONS: Our study demonstrates that DACT1 could function as a tumor suppressor but was frequently downregulated in breast cancer.

Targeting cancer metabolic vulnerabilities for advanced therapeutic efficacy.

Cancer metabolism is how cancer cells utilize nutrients and energy to support their growth and proliferation. Unlike normal cells, cancer cells have a unique metabolic profile that allows them to generate energy and the building blocks they need for rapid growth and division. This metabolic profile is marked by an increased reliance on glucose and glutamine as energy sources and changes in how cancer cells use and make key metabolic intermediates like ATP, NADH, and NADPH. This script analyzes a comprehensive overview of the latest advances in tumor metabolism, identifying the key unresolved issues, elaborates on how tumor cells differ from normal cells in their metabolism of nutrients, and explains how tumor cells conflate growth signals and nutrients to proliferate. The metabolic interaction of tumorigenesis and lipid metabolism within the tumor microenvironment and the role of ROS as an anti-tumor agent by mediating various signaling pathways for clinical cancer therapeutic targeting are outlined. Cancer metabolism is highly dynamic and heterogeneous; thus, advanced technologies to better investigate metabolism at the unicellular level without altering tumor tissue are necessary for better research and clinical transformation. The study of cancer metabolism is an area of active research, as scientists seek to understand the underlying metabolic changes that drive cancer growth and to identify potential therapeutic targets.

A distal super-enhancer activates oncogenic ETS2 via recruiting MECOM in inflammatory bowel disease and colorectal cancer.

Abnormal activities of distal cis-regulatory elements (CREs) contribute to the initiation and progression of cancer. Gain of super-enhancer (SE), a highly active distal CRE, is essential for the activation of key oncogenes in various cancers. However, the mechanism of action for most tumor-specific SEs still largely remains elusive. Here, we report that a candidate oncogene ETS2 was activated by a distal SE in inflammatory bowel disease (IBD) and colorectal cancer (CRC). The SE physically interacted with the ETS2 promoter and was required for the transcription activation of ETS2. Strikingly, the ETS2-SE activity was dramatically upregulated in both IBD and CRC tissues when compared to normal colon controls and was strongly correlated with the level of ETS2 expression. The tumor-specific activation of ETS2-SE was further validated by increased enhancer RNA transcription from this region in CRC. Intriguingly, a known IBD-risk SNP resides in the ETS2-SE and the genetic variant modulated the level of ETS2 expression through affecting the binding of an oncogenic transcription factor MECOM. Silencing of MECOM induced significant downregulation of ETS2 in CRC cells, and the level of MECOM and ETS2 correlated well with each other in CRC and IBD samples. Functionally, MECOM and ETS2 were both required for maintaining the colony-formation and sphere-formation capacities of CRC cells and MECOM was crucial for promoting migration. Taken together, we uncovered a novel disease-specific SE that distantly drives oncogenic ETS2 expression in IBD and CRC and delineated a mechanistic link between non-coding genetic variation and epigenetic regulation of gene transcription.

A novel tumor suppressor encoded by a 1p36.3 lncRNA functions as a phosphoinositide-binding protein repressing AKT phosphorylation/activation and promoting autophagy.

Peptides/small proteins, encoded by noncanonical open reading frames (ORF) of previously claimed non-coding RNAs, have recently been recognized possessing important biological functions, but largely uncharacterized. 1p36 is an important tumor suppressor gene (TSG) locus frequently deleted in multiple cancers, with critical TSGs like TP73, PRDM16, and CHD5 already validated. Our CpG methylome analysis identified a silenced 1p36.3 gene KIAA0495, previously thought coding long non-coding RNA. We found that the open reading frame 2 of KIAA0495 is actually protein-coding and translating, encoding a small protein SP0495. KIAA0495 transcript is broadly expressed in multiple normal tissues, but frequently silenced by promoter CpG methylation in multiple tumor cell lines and primary tumors including colorectal, esophageal and breast cancers. Its downregulation/methylation is associated with poor survival of cancer patients. SP0495 induces tumor cell apoptosis, cell cycle arrest, senescence and autophagy, and inhibits tumor cell growth in vitro and in vivo. Mechanistically, SP0495 binds to phosphoinositides (PtdIns(3)P, PtdIns(3,5)P2) as a lipid-binding protein, inhibits AKT phosphorylation and its downstream signaling, and further represses oncogenic AKT/mTOR, NF-κB, and Wnt/ß-catenin signaling. SP0495 also regulates the stability of autophagy regulators BECN1 and SQSTM1/p62 through modulating phosphoinositides turnover and autophagic/proteasomal degradation. Thus, we discovered and validated a 1p36.3 small protein SP0495, functioning as a novel tumor suppressor regulating AKT signaling activation and autophagy as a phosphoinositide-binding protein, being frequently inactivated by promoter methylation in multiple tumors as a potential biomarker.

Exclusive Enteral Nutrition Exerts Anti-Inflammatory Effects through Modulating Microbiota, Bile Acid Metabolism, and Immune Activities.

Exclusive enteral nutrition (EEN) can induce remission in patients with pediatric Crohn's disease (CD). This study aims to depict EEN's modification of bile acid (BA) metabolism in pediatric CD and explores the effect of the EEN-enriched BA in inhibiting the inflammatory response. The twelve enrolled pediatric CD patients showed BA dysmetabolism, represented by decreased levels of fecal secondary and unconjugated BAs as determined by UPLC-TQMS, which were accompanied by gut microbiota dysbiosis and reduced BA-metabolizing bacteria including Eubacterium and Ruminococcus genera, assessed by shotgun metagenomic sequencing. EEN treatment induced remission in these patients at eight weeks, and nine patients remained in stable remission for longer than 48 weeks. EEN improved BA dysmetabolism, with some enriched BAs, including hyocholic acid (HCA), α-muricholic acid (αMCA), strongly associated with decreased severity of CD symptoms. These BAs were significantly correlated with the increased abundance of certain bacteria, including Clostridium innocuum and Hungatella hathewayi, which express 3ß-hydroxysteroid dehydrogenase and 5ß-reductase. HCA could suppress TNF-α production by CD4+ T cells in the peripheral blood mononuclear cells (PBMCs) of CD patients. Moreover, intraperitoneal injection of HCA could attenuate dextran sulfate sodium (DSS)-induced mouse colitis. Our data suggests that BA modification may contribute to the EEN-induced remission of pediatric CD.

Epigenetic disruption of cell signaling in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is a malignancy with remarkable ethnic and geographic distribution in southern China and Southeast Asia. Alternative to genetic changes, aberrant epigenetic events disrupt multiple genes involved in cell signaling pathways through DNA methylation of promoter CpG islands and/or histone modifications. These epigenetic alterations grant cell growth advantage and contribute to the initiation and progression of NPC. In this review, we summarize the epigenetic deregulation of cell signaling in NPC tumorigenesis and highlight the importance of identifying epigenetic cell signaling regulators in NPC research. Developing pharmacologic strategies to reverse the epigenetic-silencing of cell signaling regulators might thus be useful to NPC prevention and therapy.

Targeted pharmacotherapy against neurodegeneration and neuroinflammation in early diabetic retinopathy.

Diabetic retinopathy (DR), the most frequent complication of diabetes, is one of the leading causes of irreversible blindness in working-age adults and has traditionally been regarded as a microvascular disease. However, increasing evidence has revealed that synaptic neurodegeneration of retinal ganglion cells (RGCs) and activation of glial cells may represent some of the earliest events in the pathogenesis of DR. Upon diabetes-induced metabolic stress, abnormal glycogen synthase kinase-3ß (GSK-3ß) activation drives tau hyperphosphorylation and ß-catenin downregulation, leading to mitochondrial impairment and synaptic neurodegeneration prior to RGC apoptosis. Moreover, glial cell activation triggers enhanced inflammation and oxidative stress, which may accelerate the deterioration of diabetic RGCs neurodegeneration. These findings have opened up opportunities for therapies, such as inhibition of GSK-3ß, glial cell activation, glutamate excitotoxicity and the use of neuroprotective drugs targeting early neurodegenerative processes in the retina and halting the progression of DR before the manifestation of microvascular abnormalities. Such interventions could potentially remedy early neurodegeneration and help prevent vision loss in people suffering from DR.

A Novel Strategy Conjugating PD-L1 Polypeptide With Doxorubicin Alleviates Chemotherapeutic Resistance and Enhances Immune Response in Colon Cancer.

BACKGROUND: Modifying the structure of anti-tumor chemotherapy drug is of significance to enhance the specificity and efficacy of drug-delivery. A novel proteolysis resistant PD-L1-targeted peptide (PPA1) has been reported to bind to PD-L1 and disrupt the PD-1/PD-L1 interaction, thus appearing as an outstanding tumor-targeting modification of synergistic drug conjugate for effective anti-tumor treatment. However, the combination regimen of coupling PD-L1 polypeptide with chemotherapeutic drug in tumoricidal treatment has not been reported thus far. METHODS: We developed a novel synergistic strategy by conjugating PPA1 to doxorubicin (DOX) with a pH sensitive linker that can trigger the release of DOX near acidic tumor tissues. The binding affinity of PPA1-DOX with PD-L1 and the acid-sensitive cleavage of PPA1-DOX were investigated. A mouse xenograft model of colon cancer was used to evaluate the biodistribution, cytotoxicity and anti-tumor activity of PPA1-DOX. RESULTS: PPA1-DOX construct showed high binding affinity with PD-L1 in vitro and specifically enriched within tumor when administered in vivo. PPA1-DOX exhibited a significantly lower toxicity and a remarkably higher antitumor activity in vivo, as compared with free PPA1, random polypeptide-DOX conjugate, DOX, or 5-FU, respectively. Moreover, increased infiltration of both CD4+ and CD8+ T cells was found in tumors from PPA1-DOX treated mice. CONCLUSIONS: We describe here for the first time that the dual-functional conjugate PPA1-DOX, which consist of the PD-L1-targeted polypeptide that renders both the tumor-specific drug delivery and inhibitory PD-1/PD-L1 immune checkpoint inhibition, and a cytotoxic agent that is released and kills tumor cells once reaching tumor tissues, thus representing a promising therapeutic option for colon cancer with improved efficacy and reduced toxicity.

Loss of ß-catenin via activated GSK3ß causes diabetic retinal neurodegeneration by instigating a vicious cycle of oxidative stress-driven mitochondrial impairment.

Synaptic neurodegeneration of retinal ganglion cells (RGCs) is the earliest event in the pathogenesis of diabetic retinopathy. Our previous study proposed that impairment of mitochondrial trafficking by hyperphosphorylated tau is a potential contributor to RGCs synapse degeneration. However, other molecular mechanisms underlying mitochondrial defect in diabetic retinal neurodegeneration remain to be elucidated. Here, using a high-fat diet (HFD)-induced diabetic mouse model, we showed for the first time that downregulation of active ß-catenin due to abnormal GSK3ß activation caused synaptic neurodegeneration of RGCs by inhibiting ROS scavenging enzymes, thus triggering oxidative stress-driven mitochondrial impairment in HFD-induced diabetes. Rescue of ß-catenin via ectopic expression of ß-catenin with a recombinant adenoviral vector, or via GSK3ß inhibition by a targeted si-GSK3ß, through intravitreal administration, abrogated the oxidative stress-derived mitochondrial defect and synaptic neurodegeneration in diabetic RGCs. By contrast, ablation of ß-catenin by si-ß-catenin abolished the protective effect of GSK3ß inhibition on diabetic RGCs by suppression of antioxidant scavengers and augmentation of oxidative stress-driven mitochondrial lesion. Thus, our data identify ß-catenin as a part of an endogenous protective system in diabetic RGCs and a promising target to develop intervention strategies that protect RGCs from neurodegeneration at early onset of diabetic retinopathy.