srGAP1 mediates the migration inhibition effect of Slit2-Robo1 in colorectal cancer

In silico whole-transcriptome analysis reveals a potential hsa_circ_0000375-miR-424-5p-TPM2/SRPX/SRGAP1 regulatory network related to liver metastasis of colorectal cancer

Liver metastasis is the main lethal cause of colorectal cancer (CRC). The knowledge of role and mechanism of circular RNA (circRNA) in liver metastasis of CRC is still inadequate. In this study, whole-transcriptome analysis was performed using three datasets (GSE147597, GSE147602 and GSE147603). A total of 14 potential circRNAs were identified, after which their structural patterns and binding miRNAs were obtained. Next, 45 differentially expressed miRNAs (DEmiRNAs) between CRC without and with liver metastasis were acquired, consisting 38 upregulated and 7 downregulated miRNAs. After conducting intersection analysis, expression validation and correlation analysis, miR-761 and miR-424-5p were selected as the most potential miRNAs linked to liver metastasis of CRC. Subsequently, the target genes of miR-761 or miR-424-5p were predicted and differentially expressed genes (DEGs) between CRC without and with liver metastasis were obtained. 257 genes that were commonly appeared in predicted genes and DEGs were significantly enriched in "epithelial-to-mesenchymal transition" and "signaling by Robo receptor". Among these enriched genes, only TPM2, SRPX and SRGAP1 were significantly negatively correlated with miR-424-5p and were positively linked to hsa_circ_0000375 in CRC without or with liver metastasis. Collectively, the current findings elucidated a potential hsa_circ_0000375-miR-424-5p-TPM2/SRPX/SRGAP1 network contributing to liver metastasis of CRC.

Nanoparticles Mediated circROBO1 Silencing to Inhibit Hepatocellular Carcinoma Progression by Modulating miR-130a-5p/CCNT2 Axis

Background

Circular RNAs (circRNAs) are becoming vital biomarkers and therapeutic targets for malignant tumors due to their high stability and specificity in tissues. However, biological functions of circRNAs in hepatocellular carcinoma (HCC) are still not well studied.

Methods

Gene Expression Omnibus (GEO) database and qRT-PCR were used to evaluate expression of circROBO1 (hsa_circ_0066568) in HCC tissues and cell lines. CCK-8, colony formation, EdU staining, flow cytometry for cell cycle analysis, and xenograft model assays were performed to detect the circROBO1 function in vitro and in vivo. RNA pull-down, RNA immunoprecipitation (RIP), and Luciferase reporter assays were used to investigate the relationship among circROBO1, miR-130a-5p, and CCNT2. More importantly, we developed nanoparticles made from poly lactic-co-glycolic acid (PLGA) and polyethylene glycol (PEG) chains as the delivery system of si-circROBO1 and then applied them to HCC in vitro and in mice.

Results

circROBO1 was obviously upregulated in HCC tissues and cell lines, and elevated circROBO1 was closely correlated with worse prognosis for HCC patients. Functionally, knocking down circROBO1 significantly suppressed HCC cells growth in vitro and in mice. Mechanistically, circROBO1 acted as a competing endogenous RNA to downregulate miR-130a-5p, leading to CCNT2 expression upregulation. Furthermore, miR-130a-5p mimic or CCNT2 knockdown reversed the role of circROBO1 overexpression on HCC cells, which demonstrated that circROBO1 promoted HCC development via miR-130a-5p/CCNT2 axis. In addition, we developed nanoparticles loaded with si-circROBO1, named as PLGA-PEG (si-circROBO1) NPs, which significantly prevented the proliferation of HCC cells, and did not exhibit apparent toxicity to major organs in vivo.

Conclusion

Our findings firstly demonstrate that circROBO1 overexpression promotes HCC progression by regulating miR-130a-5p/CCNT2 axis, which may serve as an effective nanotherapeutic target for HCC treatment.

Artificial Intelligence Predictive Models of Response to Cytotoxic Chemotherapy Alone or Combined to Targeted Therapy for Metastatic Colorectal Cancer Patients: A Systematic Review and Meta-Analysis

Tailored treatments for metastatic colorectal cancer (mCRC) have not yet completely evolved due to the variety in response to drugs. Therefore, artificial intelligence has been recently used to develop prognostic and predictive models of treatment response (either activity/efficacy or toxicity) to aid in clinical decision making. In this systematic review, we have examined the ability of learning methods to predict response to chemotherapy alone or combined with targeted therapy in mCRC patients by targeting specific narrative publications in Medline up to April 2022 to identify appropriate original scientific articles. After the literature search, 26 original articles met inclusion and exclusion criteria and were included in the study. Our results show that all investigations conducted on this field have provided generally promising results in predicting the response to therapy or toxic side-effects. By a meta-analytic approach we found that the overall weighted means of the area under the receiver operating characteristic (ROC) curve (AUC) were 0.90, 95% C.I. 0.80-0.95 and 0.83, 95% C.I. 0.74-0.89 in training and validation sets, respectively, indicating a good classification performance in discriminating response vs. non-response. The calculation of overall HR indicates that learning models have strong ability to predict improved survival. Lastly, the delta-radiomics and the 74 gene signatures were able to discriminate response vs. non-response by correctly identifying up to 99% of mCRC patients who were responders and up to 100% of patients who were non-responders. Specifically, when we evaluated the predictive models with tests reaching 80% sensitivity (SE) and 90% specificity (SP), the delta radiomics showed an SE of 99% and an SP of 94% in the training set and an SE of 85% and SP of 92 in the test set, whereas for the 74 gene signatures the SE was 97.6% and the SP 100% in the training set.

miR-152-3p impedes the malignant phenotypes of hepatocellular carcinoma by repressing roundabout guidance receptor 1

BACKGROUND

miR-152-3p functions as a tumour suppressor in the progression of hepatic tumorigenesis. Herein, we further discussed the prognostic significance and immune infiltration of miR-152-3p and its potential gene target in hepatocellular carcinoma (HCC).

METHODS

The Cancer Genome Atlas (TCGA), Integrative Molecular Database of Hepatocellular Carcinoma (HCCDB), Human Protein Atlas (HPA) and Kaplan-Meier Plotter databases were used to evaluate miR-152-3p and roundabout guidance receptor 1 (ROBO1) expression, prognosis and immune infiltration. In vitro cell experiments, including cell proliferation and apoptosis, were evaluated using Cell Counting Kit 8 (CCK8) and terminal-deoxynucleotidyl transferase-mediated nick end labelling (TUNEL) assays.

RESULTS

Up-regulation of ROBO1 functioned as an oncogene associated with poor prognosis, immune cell enrichment and cell proliferation in HCC. ROBO1 was significantly positively correlated with the enrichment of multiple immune cells and their biomarkers. Enrichment of type-2 T-helper (Th2) cells is an unfavourable biomarker of HCC prognosis. GSEA revealed that ROBO1 correlated with apoptosis, mitosis and carcinogenic signalling pathways. Suppression of cell proliferation and the enhancement of cell apoptosis by miR-152-3p mimics were counteracted by overexpression of ROBO1 in HCC cells.

CONCLUSION

ROBO1 expression is positively correlated with multiple immune checkpoint molecules, suggesting that ROBO1 may be a potential drug target to enhance the potency of immunotherapy. The miR-152-3p/ROBO1 signalling axis contributes to malignant progression and provides a prospective immunotherapeutic target for HCC.

Susceptibility Genes and Chromosomal Regions Associated With Non-Syndromic Familial Non-Medullary Thyroid Carcinoma: Some Pathogenetic and Diagnostic Keys

Thyroid cancer is the malignant tumor that is increasing most rapidly in the world, mainly at the expense of sporadic papillary thyroid carcinoma. The somatic alterations involved in the pathogenesis of sporadic follicular cell derived tumors are well recognized, while the predisposing alterations implicated in hereditary follicular tumors are less well known. Since the genetic background of syndromic familial non-medullary carcinoma has been well established, here we review the pathogenesis of non-syndromic familial non-medullary carcinoma emphasizing those aspects that may be useful in clinical and pathological diagnosis. Non-syndromic familial non-medullary carcinoma has a complex and heterogeneous genetic basis involving several genes and loci with a monogenic or polygenic inheritance model. Most cases are papillary thyroid carcinoma (classic and follicular variant), usually accompanied by benign thyroid nodules (follicular thyroid adenoma and/or multinodular goiter). The possible diagnostic and prognostic usefulness of the changes in the expression and/or translocation of various proteins secondary to several mutations reported in this setting requires further confirmation. Given that non-syndromic familial non-medullary carcinoma and sporadic non-medullary thyroid carcinoma share the same morphology and somatic mutations, the same targeted therapies could be used at present, if necessary, until more specific targeted treatments become available.

The emerging roles of srGAPs in cancer

GTPase activating proteins (GAPs) were initially considered as the inhibitors of cell signaling pathways because of their nature to activate the intrinsic GTPase activity of the RhoGTPases. But recent studies of dysregulated GAPs in many cancers such as glioblastoma, colorectal cancer, breast cancer, and renal cancer have elucidated the important roles of GAPs in carcinogenesis and GAPs have been shown to perform multiple nonconventional functions in different contexts. We have discussed the recent developments in the roles played by different types of srGAPs (SLIT-ROBO Rho GTPase-activating proteins) in cancer.

Associations between pancreatic expression quantitative traits and risk of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal cancers. Its poor prognosis is predominantly due to the fact that most patients remain asymptomatic until the disease reaches an advanced stage, alongside the lack of early markers and screening strategies. A better understanding of PDAC risk factors is essential for the identification of groups at high risk in the population. Genome-wide association studies (GWAS) have been a powerful tool for detecting genetic variants associated with complex traits, including pancreatic cancer. By exploiting functional and GWAS data, we investigated the associations between polymorphisms affecting gene function in the pancreas (expression quantitative trait loci, eQTLs) and PDAC risk. In a two-phase approach, we analysed 13 713 PDAC cases and 43 784 controls and identified a genome-wide significant association between the A allele of the rs2035875 polymorphism and increased PDAC risk (P = 7.14 × 10-10). This allele is known to be associated with increased expression in the pancreas of the keratin genes KRT8 and KRT18, whose increased levels have been reported to correlate with various tumour cell characteristics. Additionally, the A allele of the rs789744 variant was associated with decreased risk of developing PDAC (P = 3.56 × 10-6). This single nucleotide polymorphism is situated in the SRGAP1 gene and the A allele is associated with higher expression of the gene, which in turn inactivates the cyclin-dependent protein 42 (CDC42) gene expression, thus decreasing the risk of PDAC. In conclusion, we present here a functional-based novel PDAC risk locus and an additional strong candidate supported by significant associations and plausible biological mechanisms.

Identification of SRGAP2 as a potential oncogene and a prognostic biomarker in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the common malignancies worldwide. Slit-Robo GTPase-activating proteins (SRGAPs) have been shown to regulate the occurrence and development of various tumors. However, their specific roles in HCC remain elusive.

METHODS

The expression pattern, genetic alteration and prognostic value of SRGAPs in HCC are analyzed by bioinformatics tools. The biological functions of SRGAP2 in HCC cells are demonstrated by in vitro experiments. The high-throughput RNA sequencing is conducted to explore the underlying molecular mechanisms of SRGAP2 in HCC cells.

RESULTS

The expression levels of SRGAP1 and SRGAP2 are significantly elevated in HCC tissues compared to the normal both in Oncomine and TCGA datasets, and SRGAP2 are dramatically upregulated both in mRNA and protein levels. Moreover, higher SRGAP2 is significantly related to the clinical stages of HCC. Meanwhile, SRGAP2 might be an independent prognostic indicator, as it correlates negatively with the clinical outcomes of HCC patients. Further SRGAP2-silencing experiments imply that SRGAP2 might remarkably promote the migration and invasion of HCC cells in an EMT-independent pattern. Based on the high-throughput RNA sequencing of SRGAP2-knockdown HCC cells, enrichment and network analyses demonstrate that SRGAP2 is closely associated with cellular metabolic signaling.

CONCLUSIONS

Our study firstly illustrates the crucial role of SRGAP2 in the metastasis of HCC and explores its underlying molecular mechanisms. We identify SRGAP2 as a promising prognostic biomarker and a novel therapeutic target for HCC patients.

System-Level Analysis of Alzheimer's Disease Prioritizes Candidate Genes for Neurodegeneration

Alzheimer’s disease (AD) is a debilitating neurodegenerative disorder. Since the advent of the genome-wide association study (GWAS) we have come to understand much about the genes involved in AD heritability and pathophysiology. Large case-control meta-GWAS studies have increased our ability to prioritize weaker effect alleles, while the recent development of network-based functional prediction has provided a mechanism by which we can use machine learning to reprioritize GWAS hits in the functional context of relevant brain tissues like the hippocampus and amygdala. In parallel with these developments, groups like the Alzheimer’s Disease Neuroimaging Initiative (ADNI) have compiled rich compendia of AD patient data including genotype and biomarker information, including derived volume measures for relevant structures like the hippocampus and the amygdala. In this study we wanted to identify genes involved in AD-related atrophy of these two structures, which are often critically impaired over the course of the disease. To do this we developed a combined score prioritization method which uses the cumulative distribution function of a gene’s functional and positional score, to prioritize top genes that not only segregate with disease status, but also with hippocampal and amygdalar atrophy. Our method identified a mix of genes that had previously been identified in AD GWAS including APOE, TOMM40, and NECTIN2(PVRL2) and several others that have not been identified in AD genetic studies, but play integral roles in AD-effected functional pathways including IQSEC1, PFN1, and PAK2. Our findings support the viability of our novel combined score as a method for prioritizing region- and even cell-specific AD risk genes.

Raddeanin A inhibits proliferation, invasion, migration and promotes apoptosis of cervical cancer cells via regulating miR-224-3p/Slit2/Robo1 signaling pathway

Raddeanin A (RA), an active triterpenoid saponin extracted from the Anemone raddeana regel, plays an essential role in the suppression of many malignancies. We aimed to investigate the effects and potential mechanisms of RA on cervical cancer (CC). RA was used to treat CC cell lines (Hela and c-33A) for 24 h and 48 h. Then, the invasion, migration and cell cycle distribution of these two cell lines with RA treatment were respectively detected by transwell, wound healing and flow cytometry. Results revealed that RA significantly inhibited the invasion, migration, promoted the cell cycle arrest and apoptosis of Hela and c-33A cells. Moreover, RA was confirmed to activate the Slit2/Robo1 signaling, and bioinformatics analysis and luciferase reporter assay verified that miR-224-3p could target Slit2. Additionally, miR-224-3p overexpression reversed the inhibitory effect of RA on invasion and migration of CC cells, and it also restored the promoting effects of RA on cell cycle arrest and apoptosis. Lastly, miR-224-3p-upregulation inactivated the expression of Slit2 and Robo1 in RA-treated Hela and c-33A cells. These findings demonstrated that RA inhibits proliferation, invasion, migration and promotes apoptosis of CC cells through miR-224-3p/Slit2/Robo1 signaling pathway, which might guide the future studies or treatment of this disease.

Structural insights and evaluation of the potential impact of missense variants on the interactions of SLIT2 with ROBO1/4 in cancer progression

The cognate interaction of ROBO1/4 with its ligand SLIT2 is known to be involved in lung cancer progression. However, the precise role of genetic variants, disrupting the molecular interactions is less understood. All cancer-associated missense variants of ROBO1/4 and SLIT2 from COSMIC were screened for their pathogenicity. Homology modelling was done in Modeller 9.17, followed by molecular simulation in GROMACS. Rigid docking was performed for the cognate partners in PatchDock with refinement in HADDOCK server. Post-docking alterations in conformational, stoichiometric, as well as structural parameters, were assessed. The disruptive variants were ranked using a weighted scoring scheme. In silico prioritisation of 825 variants revealed 379 to be potentially pathogenic out of which, about 12% of the variants, i.e. ROBO1 (14), ROBO4 (8), and SLIT2 (23) altered the cognate docking. Six variants of ROBO1 and 5 variants of ROBO4 were identified as "high disruptors" of interactions with SLIT2 wild type. Likewise, 17 and 13 variants of SLIT2 were found to be "high disruptors" of its interaction with ROBO1 and ROBO4, respectively. Our study is the first report on the impact of cancer-associated missense variants on ROBO1/4 and SLIT2 interactions that might be the drivers of lung cancer progression.

Circular RNA 0001073 Attenuates Malignant Biological Behaviours in Breast Cancer Cell and Is Delivered by Nanoparticles to Inhibit Mice Tumour Growth

Background

Circular RNAs (circRNAs) are a special class of noncoding RNAs that are involved in gene regulation and compete with mRNA for miRNA binding sites. The roles of circRNAs in cancer, especially breast cancer (BC), are poorly understood.

Materials and Methods

The expression levels of circRNA 0001073 (circ-1073) in BC cells (BCCs) and tissues and peritumoural tissues were detected by real-time quantitative reverse transcription-polymerase chain reaction. Kaplan–Meier analysis and receiver operating characteristic curves were used to evaluate relapse-free survival (RFS) and the diagnostic value of circ-1073 for BC, respectively. The biological functions of circ-1073 were determined by cell counting kit-8 assays, colony formation assays, flow cytometry, wound-healing assays, transwell assays, and xenograft model studies. RNA immunoprecipitation assays were conducted to identify the connection between circ-1073 and human antigen R (HuR).

Results

Low circ-1073 expression was discovered in BCCs and BC tissues compared with normal mammary epithelial cells and peritumoural tissues, respectively. Circ-1073 downregulation was significantly associated with an unfavourable prognosis, including a shorter RFS, in BC patients. Circ-1073 is a valuable diagnostic biomarker for BC. Circ-1073 overexpression significantly inhibited BCC proliferation and induced apoptosis by increasing Cleaved Caspase-3/9 levels. Moreover, circ-1073 upregulation significantly suppressed cell mobility and epithelial–mesenchymal transition. Notably, xenograft tumour growth was inhibited by the intratumoural injection of nanoparticles containing the circ-1073 plasmid or by circ-1073 overexpression, and this inhibition was accompanied by HuR upregulation.

Conclusion

Circ-1073 functions as a tumour suppressor in BC, suggesting its potential as a novel therapeutic target in BC.

Slit/Robo Signaling Pathway in Cancer; a New Stand Point for Cancer Treatment

Angiogenesis and metastasis are two critical steps for cancer cells survival and migration. The microenvironment of tumor sphere induces new blood vessels formation for enhancing tumor mass. Preexisting capillaries and postcapillary venules in tumors bring about new blood vessels. ROBO1-ROBO4 are transmembrane receptors family which act as guidance molecules of the nervous system. The SLITs family is secreted glycoproteins that bind to these receptors. SLIT-ROBO signaling pathway plays an important role in neurogenesis and immune response. Linkage between ROBOs and their ligands (SLITs) induce chemorepllent signal for regulation of axon guidance and leukocyte cell migration, recent finding shows that it is also involved in endothelial cell migration and angiogenesis in various type of cancers. In this article we review recent finding of SLIT-ROBO pathway in angiogenesis and metastasis.

Targeting the SLIT/ROBO pathway in tumor progression: molecular mechanisms and therapeutic perspectives

The SLITs (SLIT1, SLIT2, and SLIT3) are a family of secreted proteins that mediate positional interactions between cells and their environment during development by signaling through ROBO receptors (ROBO1, ROBO2, ROBO3, and ROBO4). The SLIT/ROBO signaling pathway has been shown to participate in axonal repulsion, axon guidance, and neuronal migration in the nervous system and the formation of the vascular system. However, the role of the SLIT/ROBO pathway has not been thoroughly clarified in tumor development. The SLIT/ROBO pathway can produce both beneficial and detrimental effects in the growth of malignant cells. It has been confirmed that SLIT/ROBO play contradictory roles in tumorigenesis. Here, we discuss the tumor promotion and tumor suppression roles of the SLIT/ROBO pathway in tumor growth, angiogenesis, migration, and the tumor microenvironment. Understanding these roles will help us develop more effective cancer therapies.

The Role of the Slit/Robo Signaling Pathway

The Slit family is a family of secreted proteins that play important roles in various physiologic and pathologic activities via interacting with Robo receptors. Slit/Robo signaling was first identified in the nervous system, where it functions in neuronal axon guidance; nevertheless, an increasing number of studies have shown that Slit/Robo signaling even regulates other activities, such as angiogenesis, inflammatory cell chemotaxis, tumor cell migration and metastasis. Although the precise role of the ligand-receptor in organisms has been obscure and the conclusions drawn are sometimes paradoxical, tremendous advances in understanding the Slit/Robo signaling pathway have been made. As such, our review summarizes the characteristics of the Slit/Robo signaling pathway and its role in various cell types.

DRUM: Inference of Disease-Associated m6A RNA Methylation Sites From a Multi-Layer Heterogeneous Network

Recent studies have revealed that the RNA N 6-methyladenosine (m6A) modification plays a critical role in a variety of biological processes and associated with multiple diseases including cancers. Till this day, transcriptome-wide m6A RNA methylation sites have been identified by high-throughput sequencing technique combined with computational methods, and the information is publicly available in a few bioinformatics databases; however, the association between individual m6A sites and various diseases are still largely unknown. There are yet computational approaches developed for investigating potential association between individual m6A sites and diseases, which represents a major challenge in the epitranscriptome analysis. Thus, to infer the disease-related m6A sites, we implemented a novel multi-layer heterogeneous network-based approach, which incorporates the associations among diseases, genes and m6A RNA methylation sites from gene expression, RNA methylation and disease similarities data with the Random Walk with Restart (RWR) algorithm. To evaluate the performance of the proposed approach, a ten-fold cross validation is performed, in which our approach achieved a reasonable good performance (overall AUC: 0.827, average AUC 0.867), higher than a hypergeometric test-based approach (overall AUC: 0.7333 and average AUC: 0.723) and a random predictor (overall AUC: 0.550 and average AUC: 0.486). Additionally, we show that a number of predicted cancer-associated m6A sites are supported by existing literatures, suggesting that the proposed approach can effectively uncover the underlying epitranscriptome circuits of disease mechanisms. An online database DRUM, which stands for disease-associated ribonucleic acid methylation, was built to support the query of disease-associated RNA m6A methylation sites, and is freely available at: www.xjtlu.edu.cn/biologicalsciences/drum.

SLIT2/ROBO1 axis contributes to the Warburg effect in osteosarcoma through activation of SRC/ERK/c-MYC/PFKFB2 pathway

Cellular metabolic reprogramming is the main characteristic of cancer cells and identification of targets using this metabolic pattern is extremely important to treat cancers, such as osteosarcoma (OS). In this study, SLIT2 and ROBO1 were upregulated in OS, and higher expression of ROBO1 was associated with worse overall survival rate. Furthermore, in vitro and in vivo experiments demonstrated that the SLIT2/ROBO1 axis promotes proliferation, inhibits apoptosis, and contributes to the Warburg effect in OS cells. Mechanistically, the SLIT2/ROBO1 axis exerted cancer-promoting effects on OS via activation of the SRC/ERK/c-MYC/PFKFB2 pathway. Taken together, the findings reveal a previously unappreciated function of SLIT2/ROBO1 signaling in OS, which is intertwined with metabolic alterations that promote cancer progression. Targeting the SLIT2/ROBO1 axis may be a potential therapeutic approach for patients with OS.

SUV39H2 promotes colorectal cancer proliferation and metastasis via tri-methylation of the SLIT1 promoter

Suppressor of variegation 3-9 homolog 2 (SUV39H2) is a member of the SUV39H subfamily of lysine methyltransferases. Its role in colorectal cancer (CRC) proliferation and metastasis has remained unexplored. Here, we determined that SUV39H2 was upregulated in CRC tissues compared with that in adjacent non-neoplastic tissues. Further statistical analysis revealed that high SUV39H2 expression was strongly associated with distant metastasis (P = 0.016) and TNM stage (P = 0.038) and predicted a shorter overall survival (OS; P = 0.018) and progression-free survival (PFS; P = 0.018) time for CRC patients. Both in vitro and in vivo assays demonstrated that ectopically expressed SUV39H2 enhanced CRC proliferation and metastasis, while SUV39H2 knockdown inhibited CRC proliferation and metastasis. A molecular screen of SUV39H2 targets found that SUV39H2 negatively regulated the expression of SLIT guidance ligand 1 (SLIT1). Moreover, rescue assays suggested that SLIT1 could antagonize the function of SUV39H2 in CRC. Mechanistic studies indicated that SUV39H2 can directly bind to the SLIT1 promoter, suppressing SLIT1 transcription by catalyzing histone H3 lysine 9 (H3K9) tri-methylation. In summary, we propose that SUV39H2 can predict CRC patient prognosis and stimulate CRC malignant phenotypes via SLIT1 promoter tri-methylation.

Identification of direct negative cross-talk between the SLIT2 and bone morphogenetic protein-Gremlin signaling pathways

Slit guidance ligand 2 (SLIT2) is a large, secreted protein that binds roundabout (ROBO) receptors on multiple cell types, including neurons and kidney podocytes. SLIT2-ROBO-mediated signaling regulates neuronal migration and ureteric bud (UB) outgrowth during kidney development as well as glomerular filtration in adult kidneys. Additionally, SLIT2 binds Gremlin, an antagonist of bone morphogenetic proteins (BMPs), and BMP-Gremlin signaling also regulates UB formation. However, direct cross-talk between the ROBO2-SLIT2 and BMP-Gremlin signaling pathways has not been established. Here, we report the discovery of negative feedback between the SLIT2 and BMP-Gremlin signaling pathways. We found that the SLIT2-Gremlin interaction inhibited both SLIT2-ROBO2 signaling in neurons and Gremlin antagonism of BMP activity in myoblasts and fibroblasts. Furthermore, BMP2 down-regulated SLIT2 expression and promoter activity through canonical BMP signaling. Gremlin treatment, BMP receptor inhibition, and SMAD family member 4 (SMAD4) knockdown rescued BMP-mediated repression of SLIT2. BMP2 treatment of nephron progenitor cells derived from human embryonic stem cells decreased SLIT2 expression, further suggesting an interaction between the BMP2-Gremlin and SLIT2 pathways in human kidney cells. In conclusion, our study has revealed direct negative cross-talk between two pathways, previously thought to be unassociated, that may regulate both kidney development and adult tissue maintenance.

Comparative Proteomics Analysis Identifies Cdc42-Cdc42BPA Signaling as Prognostic Biomarker and Therapeutic Target for Colon Cancer Invasion

Metastasis is one of the major causes of treatment failure in the patients with colon cancer. The aim of our study is to find key proteins and pathways that drive invasion and metastasis in colon cancer. Eight rounds of selection of cancer cells invading through matrigel-coated chamber were performed to obtain highly invasive colon cancer sublines HCT116-I8 and RKO-I8. Stable Isotope Labeling by Amino Acids in Cell Culture technology was used to identify the differently expressed proteins, and the proteomics data were analyzed by ingenuity pathway analysis. PAK1-PBD immunoprecipitation combined with Western blot were carried out to determine Cdc42 activity, and qRT-PCR and Western blot were used to determine gene expression. The functional role of Cdc42BPA and Cdc42 pathway in colon cancer invasion was studied by loss-of-function experiments including pharmacological blockade, siRNA knockdown, chamber invasion, and WST-1 assays. Human colon cancer tissue microarray was analyzed by immunohistochemistry for overexpression of Cdc42BPA and its correlation with clinicopathological parameters and patient survival outcomes. HCT116-I8 and RKO-I8 cells showed significantly stronger invasive potential as well as decreased E-cadherin and increased vimentin expressions compared with parental cells. The differently expressed proteins in I8 cells compared with parental cells were identified. Bioinformatics analysis of proteomics data suggested that Cdc42BPA protein and Cdc42 signaling pathway are important for colon cancer invasion, which was confirmed by experimental data showing upregulation of Cdc42BPA and higher expression of active GTP-bound form of Cdc42 in HCT116-I8 and RKO-I8 cells. Functionally, pharmacological and genetic blockade of Cdc42BPA and Cdc42 signaling markedly suppressed colon cancer cell invasion and reversed epithelial mesenchymal transition process. Furthermore, compared with adjacent normal tissues, Cdc42BPA expression was significantly higher in colon cancer tissues and further upregulated in metastatic tumors in lymph nodes. More importantly, Cdc42BPA expression was correlated with metastasis and poor survival of the patients with colon cancer. This study provides the first evidence that Cdc42BPA and Cdc42 signaling are important for colon cancer invasion, and Cdc42BPA has potential implications for colon cancer prognosis and treatment.

Overexpression of CCDC34 in colorectal cancer and its involvement in tumor growth, apoptosis and invasion

It has been previously reported that increased expression of coiled-coil domain containing 34 (CCDC34), a member of the CCDCs family, may promote the proliferation and invasion of bladder cancer cells. However, its role in colorectal cancer (CRC) remains unclear. The present study investigated CCDC34 expression in CRC tissues and determined the association between CCDC34 expression and biological characteristics in patients with CRC. Additionally, the variation of cell activity, apoptosis, invasion and associated mechanisms were evaluated following CCDC34 inhibition in SW620 cells with small interfering RNA (siRNA). The role of CCDC34 in CRC growth, apoptosis and invasion was investigated. In the current study, immunohistochemistry revealed an overexpression of CCDC34 in CRC tissues compared with paracancerous tissue (χ²=29.810; P<0.001). Furthermore, CCDC34 expression was revealed to be associated with tumor invasion depth and lymphatic metastasis (χ²=4.343, P=0.037; χ²=7.915, P=0.005). Additionally, the inhibition of CCDC34 expression in SW620 cells led to reduced tumor cell activity, increased apoptosis rate and reduced invasion ability, and expression of apoptosis and invasion-associated genes varied simultaneously which demonstrated that B cell leukemia/lymphoma 2, survivin, N-cadherin, and MMP-9 were decreased, whereas E-cadherin increased significantly in cells of CCDC34-siRNA group compared with the control group (P<0.05). Therefore, CCDC34 may contribute to CRC development by inhibiting apoptosis of cancer cells and promoting invasion.

The role of Slit-Robo signaling in the regulation of tissue barriers

The role of Slit/Robo signaling has extended from initial axon repulsion in the developing nervous system to organ morphogenesis, cancer development and angiogenesis. Slit/Robo signaling regulates similar pathways within these processes. Slit/Robo ensures the homeostasis of the dynamic interaction between cell-cell and cell-matrix interactions. The dysregulation of Slit/Robo signaling damages the tissue barrier, resulting in developmental abnormalities or disease. Here, we summarize how Slit/Robo controls kidney morphogenesis and describe the dual roles of Slit/Robo signaling in the regulation of tumorigenesis and angiogenesis.