Inactivation of SLIT2-ROBO1/2 pathway in premalignant lesions of uterine cervix: clinical and prognostic significances

Transcriptomic Immune Profiles Can Represent the Tumor Immune Microenvironment Related to the Tumor Budding Histology in Uterine Cervical Cancer

Tumor budding (TB) histology has become a critical biomarker for several solid cancers. Despite the accumulating evidence for the association of TB histology with poor prognosis, the biological characteristics of TB are little known about in the context related to the tumor immune microenvironment (TIME) in uterine cervical cancer (CC). Therefore, this study aimed to identify the transcriptomic immune profiles related to TB status and further provide robust medical evidence for clinical application. In our study, total RNA was extracted and sequenced from 21 CC tissue specimens. As such, 1494 differentially expressed genes (DEGs) between the high- and low-TB groups were identified by DESeq2. After intersecting the list of DEGs and public immune genes, we selected 106 immune-related DEGs. Then, hub genes were obtained using Least Absolute Shrinkage and Selection Operator regression. Finally, the correlation between the hub genes and immune cell types was analyzed and four candidate genes were identified (one upregulated (FCGR3B) and three downregulated (ROBO2, OPRL1, and NR4A2) genes). These gene expression levels were highly accurate in predicting TB status (area under the curve >80%). Interestingly, FCGR3B is a hub gene of several innate immune pathways; its expression significantly differed in the overall survival analysis (p = 0.0016). In conclusion, FCGR3B, ROBO2, OPRL1, and NR4A2 expression can strongly interfere with TB growth and replace TB to stratify CC patients.

SLIT2 promoter hypermethylation-mediated SLIT2-IT1/miR-218 repression drives leukemogenesis and predicts adverse prognosis in myelodysplastic neoplasm

Epigenetic modifications have been found to play crucial roles in myelodysplastic neoplasm (MDS) progression. Previously, we investigated genome-wide DNA methylation alterations during MDS evolution to acute myeloid leukemia (AML) by next-generation sequencing (NGS). Herein, we further determined the role and clinical implications of an evident methylation change in CpG islands at the SLIT2 promoter identified by NGS. First, increased SLIT2 promoter methylation was validated in 11 paired MDS/AML patients during disease evolution. Additionally, SLIT2 promoter methylation was markedly increased in MDS/AML patients compared with controls and was correlated with poor clinical phenotype and outcome. Interestingly, SLIT2 expression was particularly upregulated in AML patients and was not correlated with SLIT2 promoter methylation. However, the SLIT2-embedded genes SLIT2-IT1 and miR-218 were downregulated in AML patients, which was negatively associated with SLIT2 promoter methylation and further validated by demethylation studies. Functionally, SLIT2-IT1/miR-218 overexpression exhibited antileukemic effects by affecting cell proliferation, apoptosis and colony formation in vitro and in vivo. Mechanistically, SLIT2-IT1 may function as a competing endogenous RNA by sponging miR-3156-3p to regulate BMF expression, whereas miR-218 may directly target HOXA1 in MDS progression. In summary, our findings demonstrate that SLIT2 promoter hypermethylation is associated with disease evolution in MDS and predicts poor prognoses in both MDS and AML. Epigenetic inactivation of SLIT2-IT1/miR-218 by SLIT2 promoter hypermethylation could be a promising therapeutic target in MDS.

Slit2/Robo1 signaling inhibits small-cell lung cancer by targeting β-catenin signaling in tumor cells and macrophages

Small-cell lung cancer (SCLC) is an aggressive neuroendocrine subtype of lung cancer with poor patient prognosis. However, the mechanisms that regulate SCLC progression and metastasis remain undefined. Here, we show that the expression of the slit guidance ligand 2 (SLIT2) tumor suppressor gene is reduced in SCLC tumors relative to adjacent normal tissue. In addition, the expression of the SLIT2 receptor, roundabout guidance receptor 1 (ROBO1), is upregulated. We find a positive association between SLIT2 expression and the Yes1 associated transcriptional regulator (YAP1)-expressing SCLC subtype (SCLC-Y), which shows a better prognosis. Using genetically engineered SCLC cells, adenovirus gene therapy, and preclinical xenograft models, we show that SLIT2 overexpression or the deletion of ROBO1 restricts tumor growth in vitro and in vivo. Mechanistic studies revealed significant inhibition of myeloid-derived suppressor cells (MDSCs) and M2-like tumor-associated macrophages (TAMs) in the SCLC tumors. In addition, SLIT2 enhances M1-like and phagocytic macrophages. Molecular analysis showed that ROBO1 knockout or SLIT2 overexpression suppresses the transforming growth factor beta 1 (TGF-β1)/β-catenin signaling pathway in both tumor cells and macrophages. Overall, we find that SLIT2 and ROBO1 have contrasting effects on SCLC tumors. SLIT2 suppresses, whereas ROBO1 promotes, SCLC growth by regulating the Tgf-β1/glycogen synthase kinase-3 beta (GSK3)/β-catenin signaling pathway in tumor cells and TAMs. These studies indicate that SLIT2 could be used as a novel therapeutic agent against aggressive SCLC.

ROBO1 protein expression is independently associated with biochemical recurrence in prostate cancer patients who underwent radical prostatectomy in Asian patients

Background

The purpose of this study is to investigate the correlation between ROBO1 expression and prostate cancer aggressiveness.

Methods

ROBO1 expression was evaluated in normal prostate epithelial cells (PrEC) and different prostate cancer cell lines by Western blot analysis. The migration and invasion of native and ROBO1 knockdown cells were evaluated using migration chambers and a Matrigel-coated membrane, respectively. Samples from 145 patients who underwent radical prostatectomy between June 2000 and June 2008, were retrieved from the paraffin files for tissue microarray (TMA) with immunohistochemical analysis. Biochemical recurrence (BCR)-free survival curves were estimated using the Kaplan-Meier and Cox regression methods in two groups of patients classified according to the degree of ROBO1 expression (low or high expression).

Results

ROBO1 is highly expressed in the prostate cancer cell lines. All ROBO1 knockdown cells (PC3, 22Rv1 and DU 145) showed markedly decreased migration and invasiveness compared to native cells. In 145 patients with radical prostatectomy, the Kaplan-Meier curves and log-rank test for BCR-free survival stratified by ROBO1 expression in organ-confined (pT2) or not (pT3), showed significant differences in 10-year survival between the ROBO1 high and low expression groups (87.2% versus 52.6% in pT2; P=0.047, 51.0% versus 36.9% in pT3; P=0.033). The multivariable-adjusted model showed a markedly increased hazard ratio (HR) in patients with high ROBO1 expression compared to the patients with low ROBO1expression in every model.

Conclusions

ROBO1 may play an important role in the migration and invasion of prostate cancer cells, and was independently associated with BCR.

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.

Markers of Angiogenesis, Lymphangiogenesis, and Epithelial-Mesenchymal Transition (Plasticity) in CIN and Early Invasive Carcinoma of the Cervix: Exploring Putative Molecular Mechanisms Involved in Early Tumor Invasion

The establishment of a proangiogenic phenotype and epithelial-to-mesenchymal transition (EMT) are considered as critical events that promote the induction of invasive growth in epithelial tumors, and stimulation of lymphangiogenesis is believed to confer the capacity for early dissemination to cancer cells. Recent research has revealed substantial interdependence between these processes at the molecular level as they rely on common signaling networks. Of great interest are the molecular mechanisms of (lymph-)angiogenesis and EMT associated with the earliest stages of transition from intraepithelial development to invasive growth, as they could provide the source of potentially valuable tools for targeting tumor metastasis. However, in the case of early-stage cervical cancer, the players of (lymph-)angiogenesis and EMT processes still remain substantially uncharacterized. In this study, we used RNA sequencing to compare transcriptomes of HPV(+) preinvasive neoplastic lesions and early-stage invasive carcinoma of the cervix and to identify (lymph-)angiogenesis- and EMT-related genes and pathways that may underlie early acquisition of invasive phenotype and metastatic properties by cervical cancer cells. Second, we applied flow cytometric analysis to evaluate the expression of three key lymphangiogenesis/EMT markers (VEGFR3, MET, and SLUG) in epithelial cells derived from enzymatically treated tissue specimens. Overall, among 201 differentially expressed genes, a considerable number of (lymph-)angiogenesis and EMT regulatory factors were identified, including genes encoding cytokines, growth factor receptors, transcription factors, and adhesion molecules. Pathway analysis confirmed enrichment for angiogenesis, epithelial differentiation, and cell guidance pathways at transition from intraepithelial neoplasia to invasive carcinoma and suggested immune-regulatory/inflammatory pathways to be implicated in initiation of invasive growth of cervical cancer. Flow cytometry showed cell phenotype-specific expression pattern for VEGFR3, MET, and SLUG and revealed correlation with the amount of tumor-infiltrating lymphocytes at the early stages of cervical cancer progression. Taken together, these results extend our understanding of driving forces of angiogenesis and metastasis in HPV-associated cervical cancer and may be useful for developing new treatments.

Circular PVT1: an oncogenic non-coding RNA with emerging clinical importance

The importance of circular RNAs (circRNAs) in pathological processes like cancer is evident. Among the circRNAs, recent studies have brought circPVT1 under focus as the most potent oncogenic non-coding RNA. Recent studies on various aspects of circPVT1, including its biogenesis, molecular alteration and its probable role in oncogenesis, have been conducted for research and clinical interest. In this review, a first attempt has been made to summarise the available data on circPVT1 from PubMed and other relevant databases with special emphasis on its role in development, progression and prognosis of various malignant conditions. CircPVT1 is derived from the same genetic locus encoding for long non-coding RNA lncPVT1; however, existing literature suggested circPVT1 and lncPVT1 are transcripted independently by different promoters. The interaction between circRNA and microRNA has been highlighted in majority of the few malignancies in which circPVT1 was studied. Besides its importance in diagnostic and prognostic procedures, circPVT1 seemed to have huge therapeutic potential as evident from differential drug response of cancer cell line as well as primary tumors depending on expression level of the candidate. circPVT1 in cancer therapeutics might be promising as a biomarker to make the existing treatment protocol more effective and also as potential target for designing novel therapeutic intervention.

The Expression of the SLIT-ROBO Family in Adult Patients with Acute Myeloid Leukemia

INTRODUCTION

SLIT-ROBO is a ligand-receptor family of neuronal guidance cues that has been involved in pathological and physiological angiogenesis. SLIT-ROBO expression is altered in many tumours. However, no data exist about the role of the whole family in acute myelogenous myeloid leukemia (AML).

PURPOSE

Herein, we assessed the expression of all SLIT-ROBO family in bone marrow (BM) biopsy of AML patients and control group on both protein and RNA levels.

METHODS

The paraffin-embedded tissue blocks were subjected to immunohistochemistry for SLIT1, SLIT2, SLIT3, ROBO1, ROBO2, ROBO3, and ROBO4. Microvessel density (MVD) was evaluated by CD34 immunohistochemistry. An in silico analysis using The Cancer Genome Atlas data repository was conducted for assessment of RNA level.

RESULTS

Acute myeloid leukemia patients were generally high expressers of ROBO1 and ROBO2 compared to the controls (p < 0.0001, p < 0.001, respectively). In contrast, low expression of SLIT1, SLIT2, and SLIT3 ligands has been noted more commonly in AML than in control BM samples (p < 0.0001, p = 0.003, and p = 0.001, respectively). ROBO4 expression correlated with MVD. The in silico analysis showed a poor prognostic value of high ROBO3 and low SLIT2 RNA levels (p = 0.0003 and p = 0.0008, respectively), as well as high ROBO3 and ROBO4 RNA levels in cytogenetic poor risk groups of patients (p = 0.0029 and p = 0.0003, respectively).

CONCLUSIONS

These data indicate that SLIT-ROBO family members play a role in the biology of AML. Low expression of SLIT in BM of AML patients may suggest its expression alterations in AML. Increased expression of ROBO1 and ROBO2 in AML patients suggests their participation in AML pathogenesis.

The role of Slit2 as a tumor suppressor in thyroid cancer

Slits, representative axon guidance molecules, and their Roundabout (Robo) transmembrane receptors play roles in the progression of many cancers. We investigated the effects of Slit2 on the proliferation, migration, and invasion of thyroid cancer cells, and on the prognosis of papillary thyroid cancer (PTC). Slit2 overexpression inhibited the proliferation, migration and invasion of thyroid cancer cells by inhibiting transcriptional activity of beta-catenin and regulating Rho GTPase activity. Slit2 knockdown activated the migration and invasion of thyroid cancer cells and transcriptional activity of beta-catenin. Fragment Slit2 treatment inhibited thyroid cancer cell proliferation in a dose dependent manner, and also inhibited migration and invasion. When we evaluated the protein expression of Slit2 in PTCs, 24 of 160 PTCs (15%) were negative for Slit2 protein expression and these patients had significantly increased risk of cervical lymph node metastasis (P < 0.001), distant metastasis (P < 0.001) and recurrence of PTC (P < 0.001). Our findings suggest a role for Slit2 as a tumor suppressor, and also as a novel prognostic and potential therapeutic target for thyroid cancer.

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.

Integrative genomic and network analysis identified novel genes associated with the development of advanced cervical squamous cell carcinoma

BACKGROUND

CSCC is one of the most common cancer affecting women globally. Though it is caused by the infection of hrHPV but long latency period for malignant outcome in only a subset of hrHPV infected women indicates involvement of additional alterations, primarily CNVs. Here, we showed how CNVs played a crucial role in development of advanced tumors (stage III/IV) in Indian patients.

METHODS

Initially, high-resolution CGH-SNP microarray analysis pointed out frequent CNVs followed by significantly altered genes. After comparison with TCGA dataset, expressions of the genes were checked in three CSCC datasets to identify key genes followed by Ingenuity® Pathway analysis. Then node effect property analysis was applied on the constructed PPI network to rank the key proteins. Finally, validations in independent samples were performed.

RESULTS

For the first time, frequent chromosomal amplifications at 3q13.13-3q29, 1p36.11-1p31.1, 1q21.1-1q44 and 5p15.33-5p12 followed by common deletions at 11q14.1-11q25, 2q34-2q37.3, 4p16.3-4p12 and 13q13.3-13q14.3 were identified in Indian CSCC patients. Integrative analysis found 78 key genes including several novel ones, which were mostly associated with 'Cancer' and may regulate DNA repair and metabolic pathways. Analysis showed PARP1 and ATR were among the top ranking protein interactors.

CONCLUSIONS

Frequent amplification and over-expression of ATR and PARP1 were further confirmed in cervical lesions, indicating their association with poor prognosis of advanced CSCC patients.

GENERAL SIGNIFICANCE

Our novel approach identified precise CNVs along with several novel genes within these loci and showed that PARP1 and ATR, having biologically significant interactions, may be involved in development of advanced CSCC.

Frequent alterations of SLIT2-ROBO1-CDC42 signalling pathway in breast cancer: clinicopathological correlation

The aim of the study was to understand the role of SLIT2-ROBO1/2-CDC42 signalling pathways in development of breast cancer (BC). Primary BC samples (n = 150), comprising of almost equal proportion of four subtypes were tested for molecular alterations of SLIT2, ROBO1, ROBO2 and CDC42, the key regulator genes of this pathway. Deletion and methylation frequencies of the candidate genes were seen in the following order: deletion, SLIT2 (38.6%) > ROBO1 (30%) > ROBO2 (7.3%); methylation, SLIT2 (63.3%) > ROBO1 (26.6%) >ROBO2 (9.3%). Majority (80%, 120/150) of the tumours showed alterations (deletion/methylation) in at least one of the candidate genes. Overall, alterations of the candidate genes were as follows: SLIT2, 75.3% (101/150); ROBO1, 45.3% (68/150); ROBO2, 15.3% (23/150). Significantly, higher alteration of SLIT2 locus was observed in triple negative breast cancer (TNBC) over HER2 subtype (P = 0.0014). Similar trend is also seen in overall alterations of SLIT2 and/or ROBO1, in TNBC than HER2 subtype (P = 0.0012); of SLIT2 and/or ROBO2 in TNBC than luminal A (P = 0.014) and HER2 subtype (P = 0.048). Immunohistochemical analysis of SLIT2, ROBO1/2 showed reduced expression, concordant with their molecular alterations. Also, high expression of total CDC42 (49/52; 94.2%) and reduced expression of phospho Serine-71 CDC42 (41/52; 78.8%) was observed. Coalterations of SLIT2 and/or ROBO1, SLIT2 and/or ROBO2 had significant association with reduced expression of phospho Serine-71 CDC42 (P = 0.0012-0.0038). Alterations of SLIT2 and/or ROBO1, reduced expression of phospho Serine-71 CDC42 predicted poor survival of BC patients. Results indicate the importance of SLIT2-ROBO1-CDC42 signalling pathway in predicting tumour progression.

Loss of miR-203 regulates cell shape and matrix adhesion through ROBO1/Rac/FAK in response to stiffness

Breast tumor progression is accompanied by changes in the surrounding extracellular matrix (ECM) that increase stiffness of the microenvironment. Mammary epithelial cells engage regulatory pathways that permit dynamic responses to mechanical cues from the ECM. Here, we identify a SLIT2/ROBO1 signaling circuit as a key regulatory mechanism by which cells sense and respond to ECM stiffness to preserve tensional homeostasis. We observed that Robo1 ablation in the developing mammary gland compromised actin stress fiber assembly and inhibited cell contractility to perturb tissue morphogenesis, whereas SLIT2 treatment stimulated Rac and increased focal adhesion kinase activity to enhance cell tension by maintaining cell shape and matrix adhesion. Further investigation revealed that a stiff ECM increased Robo1 levels by down-regulating miR-203. Consistently, patients whose tumor expressed a low miR-203/high Robo1 expression pattern exhibited a better overall survival prognosis. These studies show that cells subjected to stiffened environments up-regulate Robo1 as a protective mechanism that maintains cell shape and facilitates ECM adherence.

The emerging role of Slit-Robo pathway in gastric and other gastro intestinal cancers

Gastric cancer remains one of the most common cancers worldwide and one of the leading cause for cancer-related deaths. Due to the high frequency of metastasis, it is still one of the most lethal malignancies in which kinds of signaling pathways are involved in. The Roundabout (ROBO) receptors and their secreted SLIT glycoprotein ligands, which were originally identified as important axon guidance molecules, have implication in the regulation of neurons and glia, leukocytes, and endothelial cells migration. Recent researches also put high emphasis on the important roles of the Slit-Robo pathway in tumorigenesis, cancer progression and metastasis. Herein we provide a comprehensive review on the role of these molecules and their associated signaling pathway in gastric and other gastrointestinal cancers. Improved knowledge of the Slit-Robo signaling pathway in gastric carcinoma will be useful for deep understanding the mechanisms of tumor development and identifying ideal targets of anticancer therapy in gastric carcinoma.

Deregulation of SLIT2-mediated Cdc42 activity is associated with esophageal cancer metastasis and poor prognosis

INTRODUCTION

SLIT2, a secreted protein, has been found to inactivate Cdc42 GTPase to modulate neural cell migration. However, alteration of SLIT2-mediated Cdc42 in terms of migration regulation remains undefined in esophageal squamous cell carcinoma (ESCC).

METHODS

We report here in ESCC cell, animal, and clinical models that SLIT2 acts as a migration suppressor and serves as a prognostic biomarker.

RESULTS

The immunohistochemistry data indicated that 31.8% (49 of 154) of tumors from ESCC patients showed low expression of SLIT2 protein which correlated with poor overall survival and disease-free survival. DNA methylation analysis suggested that promoter hypermethylation is responsible for low expression of SLIT2 in ESCC. Knockdown of SLIT2 increased ESCC cell migration, while SLIT2 stable overexpression reduced cell migration. ESCC cells treated with conditioned media from cells overexpressing SLIT2 also suppressed cell migration. Importantly, silencing of SLIT2 decreased the complex formation, and thus induced Cdc42 activity and promoted membrane localization of focal adhesion kinase and Paxillin. Anti-metastatic effect of SLIT2 was confirmed in an experimental metastasis model of SLIT2 knockdown ESCC cells.

CONCLUSION

Our results provide novel evidence that low expression of SLIT2 correlates with poor prognosis and promotes metastasis in ESCC, which may be regulated by the Cdc42-mediated pathways.

Overexpression of Roundabout4 predicts poor prognosis of primary glioma patients via correlating with microvessel density

Roundabout4 (Robo4), a new member of Robo proteins family, is specifically expressed in endothelial cells. Recent studies have indicated that Robo4 could regulate tumor angiogenesis and vascular permeability. However, the role and function of Robo4 are not well understood. This study was performed to investigate the expression of Robo4 in primary glioma patients, and thus to determine the association of Robo4 expression with microvessel density and survival of glioma patients. In this study, real-time PCR and immunohistochemistry were performed to examine the mRNA level and protein expression of Robo4 in both 43 cases of glioma samples and 10 cases of normal brain tissue samples. The results demonstrated that Robo4 was significantly up-regulated in glioma tissues compared with normal brain tissues. In addition, double immunofluorescent staining revealed that Robo4 expression co-localized with CD34 expression in the vessel of glioma tissues. The expression of Robo4 positively correlated with patients' age (P = 0.0139) and glioma grade (P < 0.0001). A linear correlation was observed between the relative mRNA expression of Robo4 values and corresponding microvessel density values (r = 0.9735, P < 0.0001). Kaplan-Meier analysis and log-rank test result showed that the overall survival of patients with Robo4 high expression was significantly shorter than that of patients with Robo4 low expression (P < 0.001). The results of present study verify that overexpression of Robo4 is related to poor prognosis of primary gliomas patients through correlating with microvessel density.

Quantitative DNA methylation analysis of candidate genes in cervical cancer

Aberrant DNA methylation has been observed in cervical cancer; however, most studies have used non-quantitative approaches to measure DNA methylation. The objective of this study was to quantify methylation within a select panel of genes previously identified as targets for epigenetic silencing in cervical cancer and to identify genes with elevated methylation that can distinguish cancer from normal cervical tissues. We identified 49 women with invasive squamous cell cancer of the cervix and 22 women with normal cytology specimens. Bisulfite-modified genomic DNA was amplified and quantitative pyrosequencing completed for 10 genes (APC, CCNA, CDH1, CDH13, WIF1, TIMP3, DAPK1, RARB, FHIT, and SLIT2). A Methylation Index was calculated as the mean percent methylation across all CpG sites analyzed per gene (~4-9 CpG site) per sequence. A binary cut-point was defined at >15% methylation. Sensitivity, specificity and area under ROC curve (AUC) of methylation in individual genes or a panel was examined. The median methylation index was significantly higher in cases compared to controls in 8 genes, whereas there was no difference in median methylation for 2 genes. Compared to HPV and age, the combination of DNA methylation level of DAPK1, SLIT2, WIF1 and RARB with HPV and age significantly improved the AUC from 0.79 to 0.99 (95% CI: 0.97–1.00, p-value = 0.003). Pyrosequencing analysis confirmed that several genes are common targets for aberrant methylation in cervical cancer and DNA methylation level of four genes appears to increase specificity to identify cancer compared to HPV detection alone. Alterations in DNA methylation of specific genes in cervical cancers, such as DAPK1, RARB, WIF1, and SLIT2, may also occur early in cervical carcinogenesis and should be evaluated.

Frequent inactivation of SLIT2 and ROBO1 signaling in head and neck lesions: clinical and prognostic implications

OBJECTIVE

The protein SLIT2 and its receptor ROBO1 regulate different cellular processes, such as proliferation, apoptosis, and migration. In this study our aim is to understand the alterations of these genes during development of head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

First, molecular alterations of the genes were analyzed in 30 dysplastic lesions, 128 primary HNSCC samples, and 1 HNSCC cell line. Then alterations were correlated with mRNA expression (n = 22) and protein expression (n = 29). Finally, the alterations were correlated with different clinicopathologic parameters and clinical outcomes of the patients.

RESULTS

ROBO1 had a comparatively high frequency of deletion (28.5%-54.2%) from dysplastic lesions and subsequent clinical stages than did SLIT2 (16.6-27%). On the contrary, SLIT2 had a high frequency (56.6%-81.2%) of promoter methylation from dysplastic lesions onward compared with ROBO1 (20%-32.8%). Interestingly, alterations of SLIT2 and ROBO1 were high in dysplastic lesions (80%), followed by comparable frequencies (92.5%-95.3%) in subsequent stages of tumor. Alterations of these genes showed concordance with their mRNA/protein expression and significant association with poor patient outcome.

CONCLUSIONS

Our data suggest that inactivation of SLIT2 and/or ROBO1 is one of the early events in development of dysplastic lesions of head and neck and has prognostic importance.

Down-regulation of ROBO2 expression in prostate cancers

Several lines of evidence exist that axon guidance genes are involved in cancer pathogenesis. Axon guidance genes ROBO1 and ROBO2 are candidate tumor suppressor genes (TSG). The aim of our study was to address whether ROBO1 and ROBO2 expressions are altered in prostate cancers (PCA). In this study, we analyzed ROBO1 and ROBO2 expressions in 107 PCAs. In the immunohistochemistry, loss of ROBO2 expression was identified in 66 % of PCAs and was significantly higher than that in normal cells (p < 0.001). By contrast, there was no significant difference of ROBO1 expression between normal and PCAs. Our results indicate that axon guidance protein ROBO2 is frequently lost in PCA and that ROBO2 might be involved in PCA pathogenesis as a candidate TSG.

An association between genetic variation in the roundabout, axon guidance receptor, homolog 2 gene and immunity traits in chickens

The roundabout, axon guidance receptor, homolog 2 (ROBO2) gene is one member of the roundabout (ROBO) family, which belongs to the immunoglobulin superfamily. The ROBO molecules are known to function in axon guidance and cell migration and are involved in SLIT/ROBO signaling. In this study, we obtained the full-length cDNA sequence of the chicken ROBO2 gene. Sequence analysis indicated that 3 SNP (1418G > A, 1421C > A and 2462T > C) exist in exons 5 and 12 of the ROBO2 gene. Genotyping results revealed that the allele frequency of SNP 1421C > A was similar in all tested breeds, but the allele frequencies of the other 2 SNP were different between White Leghorn and Chinese indigenous chickens. Allele G of 1418G > A and allele T of 2462T > C predominated in the Chinese indigenous breed, whereas alleles A and C predominated in the White Leghorn breed. Association analyses revealed that birds with the GG genotype of SNP 1418G > A or the TT genotype of SNP 2462T > C had significantly higher antibody responses to Newcastle disease virus (NDV_S/P; P < 0.01) than carriers of the A allele (GA and AA) or the C allele (TC), respectively. Real-time PCR further revealed that ROBO2 expression in the spleens of the birds with higher antibody responses (GG and TT genotypes at SNP 1418 and 2462, respectively) was significantly higher than in the spleens of birds with the AA and AG genotypes at SNP 1418 or the TC genotype at SNP 2462 (P < 0.01). The results demonstrated that genetic variation at the ROBO2 gene plays a key role in the immune response to Newcastle disease virus, and SNP 1418G > A and 2462T > C can be used as genetic markers for the selection of chickens with stronger immune responses to Newcastle disease virus.

Frameshift mutations of axon guidance genes ROBO1 and ROBO2 in gastric and colorectal cancers with microsatellite instability

AIMS

Several lines of evidence indicate that axon guidance genes are involved not only in neural development but also in cancer development. ROBO1 and ROBO2, crucial regulators of axon guidance, are considered potential tumour suppressor genes. The aim of this study was to explore whether ROBO1 and ROBO2 genes are somatically mutated and expressionally altered in gastric (GC) and colorectal cancers (CRC).

METHODS

In a public database, we observed that both ROBO1 and ROBO2 had mononucleotide repeats in their coding exons that could be mutation targets in cancers with microsatellite instability (MSI). We analysed mutations of these repeats in 77 GC and 88 CRC either with high MSI (MSI-H) or low MSI/microsatellite stability (MSI-L/MSS) by single-strand conformation polymorphism (SSCP) and DNA sequencing. We analysed ROBO1 and ROBO2 expressions in GC and CRC by immunohistochemistry as well.

RESULTS

Overall, we found five ROBO1 and five ROBO2 frameshift mutations in the repeats. They were detected exclusively in the cancers with MSI-H (10/70, 14.2%), but not in MSI-L/MSS (0/95, 0%) (p=0.018). In the immunohistochemistry, loss of ROBO2 expression was identified in 22 (29%) and 17 (19%) of GC and CRC, respectively, while increased expression of ROBO2 was found in 15 (20%) and 22 (25%) of GC and CRC, respectively. There were co-occurrences of mutation and loss of expression in both ROBO1 (4/5, 80% mutated cases, p<0.001) and ROBO2 (5/5, 100% mutated cases, p<0.05) genes.

CONCLUSION

This is the first report of ROBO1 and ROBO2 frameshift mutations in GC and CRC. Frameshift mutations of ROBO1 and ROBO2 genes and alteration of ROBO2 expression in GC and CRC suggest that both genes might play roles in the pathogenesis of GC and CRC.

Slit2 expression and its correlation with subcellular localization of β-catenin in gastric cancer

Gastric cancer is the fourth most common cancer worldwide. Several signaling pathways are involved in gastric cancer development and progression. Slit2 was recently found to be involved in cancer; however, its expression pattern in gastric cancer has not been discovered yet. In the present study, we investigated the expression of Slit2 in human gastric cancer and its correlation with the expression and subcellular localization of β-catenin. Immunohistochemistry (IHC) staining revealed that Slit2 was highly expressed in human gastric cancer tissues, while it was low or weakly expressed in normal gastric tissues. The differences in clinicopathological features between different groups were determined using Pearson's χ2 test. Slit2 levels were significantly associated with differentiation, Lauren's classification, lymph node metastasis and TNM staging. Slit2 levels were positively correlated with β-catenin level in gastric cancer tissues and cell lines. High levels of Slit2 were correlated with the membrane localization of β-catenin, and low levels of Slit2 were correlated with nuclear translocation of β-catenin in both gastric cancer tissues and cell lines assayed by IHC and immunofluorescence staining, respectively. Our data suggest that Slit2 was highly expressed in gastric cancer patients with less advanced clinicopathological features. Slit2 levels were correlated with β-catenin level and subcellular localization.