Differential expression of hDAB2IPA and hDAB2IPB in normal tissues and promoter methylation of hDAB2IPA in hepatocellular carcinoma

circSLCO1B7 suppresses the malignant progression of hepatocellular carcinoma via the miR-556-3p/DAB2IP axis

Circular RNAs (circRNAs) are noncoding RNAs with a circular colsed structure that play an important role in the occurrence and development of cancers. The functional mechanism of circRNAs as ceRNAs in hepatocellular carcinoma (HCC) and its effect on the invasion and metastasis of HCC need to be further studied. Five pairs of HCC tissues were selected for high-throughput sequencing, and 19 circRNAs with differential expression were obtained. The expression of circSLCO1B7 was obviously downregulated in 50 pairs of tumor tissues and plasma of HCC patients, which was closely related to the TNM stage, lymph node metastasis and tumor size. Cell functional experiments showed that circSLCO1B7 could inhibit cell growth, migration, invasion and promote cell apoptosis. In the regulatory mechanism, circSLCO1B7 sponged miR-556-3p to regulate the expression of the downstream target gene DAB2IP and induced the Epithelial-mesenchymal transition (EMT) progression. Our results indicated that circSLCO1B7 significantly inhibits the metastasis of HCC via the miR-556-3p/DAB2IP axis. Thus, circSLCO1B7 is a good candidate as a therapeutic target.

DNA Methylation Biomarkers in Cancer: Current Clinical Utility and Future Perspectives

Epigenetic alterations are related to inherited but reversible changes in modifications that regulate gene activity beyond the DNA sequence. DNA methylation is the best characterized epigenetic modification, controlling DNA stability, DNA structure, transcription, and regulation, contributing to normal development and differentiation. In this section, we first discuss the cellular functions of DNA methylation and focus on how this fundamental biological process is impaired in cancer. Changes in DNA methylation status in cancer have been heralded as promising targets for the development of diagnostic, prognostic, and predictive biomarkers due to their noninvasive accessibility in bodily fluids (such as blood, urine, stool), reversibility, stability, and frequency. The absence of markers for definitive diagnosis of most types of cancer and, in some cases, DNA methylation biomarkers being more specific and sensitive than commonly used protein biomarkers indicate a strong need for continued research to expand DNA methylation markers. Although the information on changes in DNA methylation status in cancer and research on its clinical relevance is rapidly increasing, the number of DNA methylation biomarkers currently available as commercial tests is very small. Here, we focus on the importance of DNA methylation location and target genes likely to be developed in the future for the development of biomarkers in addition to existing commercial tests. Following a detailed study of possible target genes, we summarize the current clinical application status of the most studied and validated DNA methylation biomarkers, including SEPT9, SDC2, BMP3, NDRG4, SFRP2, TFPI2, VIM and MGMT.

DAB2IP predicts treatment response and prognosis of ESCC patients and modulates its radiosensitivity through enhancing IR-induced activation of the ASK1-JNK pathway

Background

Disabled homolog 2 interacting protein (DAB2IP) plays a tumor-suppressive role in several types of human cancers. However, the molecular status and function of the DAB2IP gene in esophageal squamous cell carcinoma (ESCC) patients who received definitive chemoradiotherapy is rarely reported.

Methods

We examined the expression dynamics of DAB2IP by immunohistochemistry (IHC) in 140 ESCC patients treated with definitive chemoradiotherapy. A series of in vivo and in vitro experiments were performed to elucidate the effect of DAB2IP on the chemoradiotherapy (CRT) response and its underlying mechanisms in ESCC.

Results

Decreased expression of DAB2IP in ESCCs correlated positively with ESCC resistance to CRT and was a strong and independent predictor for short disease-specific survival (DSS) of ESCC patients. Furthermore, the therapeutic sensitivity of CRT was substantially increased by ectopic overexpression of DAB2IP in ESCC cells. In addition, knockdown of DAB2IP dramatically enhanced resistance to CRT in ESCC. Finally, we demonstrated that DAB2IP regulates ESCC cell radiosensitivity through enhancing ionizing radiation (IR)-induced activation of the ASK1-JNK signaling pathway.

Conclusions

Our data highlight the molecular etiology and clinical significance of DAB2IP in ESCC, which may represent a new therapeutic strategy to improve therapy and survival for ESCC patients.

DAB2IP suppresses tumor malignancy by inhibiting GRP75-driven p53 ubiquitination in colon cancer

Increasing evidence has shown that DAB2IP acts as a tumor suppressor and plays an inhibitory role in many signals associated with tumorigenesis. However, the underlying mechanism of this function remains unclear. Our study shows that DAB2IP was positively associated with a good prognosis in patients with colorectal cancer and wild-type p53 expression. An in vitro assay showed that DAB2IP elicited potent tumor-suppressive effects by inhibiting cell invasiveness and colony formation and promoting cell apoptosis in wild-type p53 colon cancer cells. In addition, DAB2IP improved the stability of wild-type p53 by inhibiting its degradation in a ubiquitin-proteasome-dependent manner. Using mass spectrometry profiling, we revealed that DAB2IP and p53 interacted with the ubiquitin ligase-related protein GRP75. Mechanistically, DAB2IP is competitively bound to GRP75, thus reducing GRP75-driven p53 ubiquitination and degradation. Moreover, the Ras-GAP domain was required for the DAB2IP-GRP75 interaction and DAB2IP-mediated p53 ubiquitination. Finally, animal experiments revealed that DAB2IP inhibited tumor progression in vivo. In conclusion, our study presents a novel function of DAB2IP in GRP75-driven wild-type p53 degradation, providing new insight into DAB2IP-induced tumor suppression and a novel molecular interpretation of the p53 pathway.

A Novel Gene Prognostic Signature Based on Differential DNA Methylation in Breast Cancer

Background: DNA methylation played essential roles in regulating gene expression. The impact of DNA methylation status on the occurrence and development of cancers has been well demonstrated. However, little is known about its prognostic role in breast cancer (BC).

Materials: The Illumina Human Methylation450 array (450k array) data of BC was downloaded from the UCSC xena database. Transcriptomic data of BC was downloaded from the Cancer Genome Atlas (TCGA) database. Firstly, we used univariate and multivariate Cox regression analysis to screen out independent prognostic CpGs, and then we identified methylation-associated prognosis subgroups by consensus clustering. Next, a methylation prognostic model was developed using multivariate Cox analysis and was validated with the Illumina Human Methylation27 array (27k array) dataset of BC. We then screened out differentially expressed genes (DEGs) between methylation high-risk and low-risk groups and constructed a methylation-based gene prognostic signature. Further, we validated the gene signature with three subgroups of the TCGA-BRCA dataset and an external dataset GSE146558 from the Gene Expression Omnibus (GEO) database.

Results: We established a methylation prognostic signature and a methylation-based gene prognostic signature, and there was a close positive correlation between them. The gene prognostic signature involved six genes: IRF2, KCNJ11, ZDHHC9, LRP11, PCMT1, and TMEM70. We verified their expression in mRNA and protein levels in BC. Both methylation and methylation-based gene prognostic signatures showed good prognostic stratification ability. The AUC values of 3-years, 5-years overall survival (OS) were 0.737, 0.744 in the methylation signature and 0.725, 0.715 in the gene signature, respectively. In the validation groups, high-risk patients were confirmed to have poorer OS. The AUC values of 3 years were 0.757, 0.735, 0.733 in the three subgroups of TCGA dataset and 0.635 in GSE146558 dataset.

Conclusion: This study revealed the DNA methylation landscape and established promising methylation and methylation-based gene prognostic signatures that could serve as potential prognostic biomarkers and therapeutic targets.

MAPK/ERK Signaling Pathway in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a major health concern worldwide, and its incidence is increasing steadily. Recently, the MAPK/ERK signaling pathway in HCC has gained renewed attention from basic and clinical researchers. The MAPK/ERK signaling pathway is activated in more than 50% of human HCC cases; however, activating mutations in RAS and RAF genes are rarely found in HCC, which are major genetic events leading to the activation of the MAPK/ERK signaling pathway in other cancers. This suggests that there is an alternative mechanism behind the activation of the signaling pathway in HCC. Here, we will review recent advances in understanding the cellular and molecular mechanisms involved in the activation of the MAPK/ERK signaling pathway and discuss potential therapeutic strategies targeting the signaling pathway in the context of HCC.

DAB2IP Plays Important Clinical Significance and Correlates With Immune Infiltration in Renal Cell Carcinoma

Background:

Disabled homolog 2-interacting protein is a new member of the Ras GTPase superfamily involved in the regulation of cell proliferation, apoptosis, and metastasis. However, the expression of disabled homolog 2-interacting protein in renal cell carcinoma, its correlation with cancer prognosis, and tumor infiltrating lymphocytes remains unclear.

Methods:

The expression of disabled homolog 2-interacting protein was analyzed by UALCAN database, GEPIA database and the evaluation of disabled homolog 2-interacting protein effects on clinical prognosis. Prognostic factor analysis was used to identify the correlations between disabled homolog 2-interacting protein and cancer immune infiltration via the TIMER database. In addition, COXPRESdb database was used to analyze the enrichment of disabled homolog 2-interacting protein co-expression genes.

Results:

Compared to the normal tissues, the messenger RNA expression levels of DAB2IP are higher in 8 while lower in 15 types of tumor tissues. Furthermore, disabled homolog 2-interacting protein has high expression in kidney chromophobe and low expression in both kidney renal clear cell carcinoma and kidney renal papillary cell carcinoma. The messenger RNA expression levels of disabled homolog 2-interacting protein decrease gradually due to the increasing tumor staging which positively correlates with disease-free survival and overall survival in both kidney renal clear cell carcinoma and kidney renal papillary cell carcinoma. The expression levels of disabled homolog 2-interacting protein also positively correlate with the tumor purity of kidney chromophobe, kidney renal clear cell carcinoma, and kidney renal papillary cell carcinoma samples. Besides, the expression of disabled homolog 2-interacting protein in renal cell carcinoma has negative correlation with the immune infiltration, and the immune infiltration of B cells and CD8+ T cells affects the prognosis of kidney renal papillary cell carcinoma. Enrichment analysis of disabled homolog 2-interacting protein co-expressed genes suggested that its biological role was mainly in regulating GTPase activity.

Conclusions:

These findings suggest that disabled homolog 2-interacting protein functions as a tumor suppressor in the progression of renal cell carcinoma, and the expression of disabled homolog 2-interacting protein is related to the immune infiltrating cells and affects the survival of renal cell carcinoma. Disabled homolog 2-interacting protein can be a novel clinical biomarker for patients with renal cell carcinoma, which also provides new insights for the future treatments of renal cell carcinoma.

CircRNA-5692 inhibits the progression of hepatocellular carcinoma by sponging miR-328-5p to enhance DAB2IP expression

Circular RNAs (circRNAs), one kind of noncoding RNAs, can interact with miRNA and transcription factors to regulate gene expression. However, little is known on which circRNA is crucial for the pathogenesis of hepatocellular carcinoma (HCC). CircRNA expression profile was analyzed by a microarray. Regulatory gene targets were predicted by bioinformatics analysis and validated by luciferase assay. Their expression was determined by qRT-PCR and Western blotting. DNA methylation was determined by methylation-specific PCR. Gene knockdown and overexpression were mediated by lentivirus-mediated shRNA and transfection with plasmids for cDNA expression, respectively. MTT assay, wound-healing assay, transwell invasion assay, and flow cytometry were used to determine malignant behaviors of HCC cells. HCC xenograft mouse model was used to determine the in vivo effects of circRNA-5692. CircRNA-5692 expression was downregulated in HCC tissues, and circRNA-5692 overexpression attenuated the malignant behaviors of HCC cells. Bioinformatics predicted that circRNA-5692 interacted with miR-328-5p, which targeted the DAB2IP mRNA. Actually, miR-328-5p promoted the malignant behaviors of HCC cells, while DAB2IP had opposite effects. Moreover, circRNA-5692 overexpression inhibited the growth of xenograft HCC tumors in vivo by decreasing miR-328-5p expression to enhance DAB2IP expression. In conclusion, the circRNA-5692–miR-328-5p–DAB2IP regulatory pathway inhibits the progression of HCC. Our findings may provide potential new targets for the diagnosis and therapy of HCC.

miR-1307-3p promotes tumor growth and metastasis of hepatocellular carcinoma by repressing DAB2 interacting protein

Increasing studies provide evidence to support that microRNAs (miRNAs) play important roles in regulating hepatocellular carcinoma (HCC) initiation and progression. However, whether miR-1307-3p is aberrantly expressed in HCC and affects malignant behaviors of cancer cells remain unknown. In this study, we found that miR-1307-3p expression was obviously up-regulated in HCC compared to adjacent nontumor tissues. Moreover, miR-1307-3p expression was prominently higher in HCC cells compared with the normal hepatic cell line LO2. Patients with venous infiltration, tumor size ≥5 cm and advanced tumor stages (III + IV) had significant higher levels of miR-1307-3p in HCC tissues. Notably, the high level of miR-1307-3p predicted poor clinical outcomes of HCC patients. Functionally, miR-1307-3p knockdown inhibited the proliferation, migration and invasion of MHCC97H and HCCLM3 cells, and suppressed the in vivo growth and metastasis of HCCLM3 cells. Conversely, overexpression of miR-1307-3p facilitated Hep3B cell proliferation, migration and invasion. Mechanistically, DAB2 interacting protein (DAB2IP) was screened as a direct target of miR-1307-3p. The expression of DAB2IP mRNA was down-regulated and inversely correlated with miR-1307-3p level in HCC tissues. miR-1307-3p knockdown increased the level of DAB2IP in HCC cells. Luciferase reporter assay confirmed the direct interaction between miR-1307-3p and 3'UTR of DAB2IP. Importantly, DAB2IP overexpression significantly suppressed the proliferation, migration and invasion of HCCLM3 cells. DAB2IP knockdown rescued miR-1307-3p silencing-attenuated HCC cell proliferation, migration and invasion. Taken together, our findings suggest that miR-1307-3p plays a driving role in HCC progression by targeting DAB2IP. Our study may provide new therapeutic targets for HCC treatment.

DAB2IP Expression in Abdominal Aortic Aneurysm: EZH2 and mir-363-3p as Potential Mediators

BACKGROUND/AIM

Nine genetic loci have been associated with abdominal aortic aneurysm (AAA) susceptibility, including DAB2IP. This gene is playing a role in apoptosis, cell proliferation and epithelial-to-mesenchymal transition in cancers. This study aimed to elucidate the differential expression levels of DAB2IP in AAA tissues and investigate whether mir-363-3p and EZH2 can be considered as potential mediators of its expression.

MATERIALS AND METHODS

18 AAA samples and 15 non-aneurysmatic controls were collected. Relative mRNA expression levels of DAB2IP, EZH2 and mir-363-3p were measured using qPCR.

RESULTS

DAB2IP was significant up-regulated (~2.29 fold) in AAA tissues, while EZH2 and mir-363-3p were down-regulated (3.28 and 3.62-fold, respectively). A limited negative correlation was found between the DAB2IP and EZH2 expression and between DAB2IP and the mir-363-3p.

CONCLUSION

An increased expression of DAB2IP in AAA tissues was shown. We suggest 2 potential mediators of DAB2IP expression in abdominal aortic aneurysm, EZH2 and mir-363-3p.

A potential clinical significance of DAB2IP and SPRY2 transcript variants in prostate cancer

Deregulation of key signaling pathways is one of the primary phenomena in carcinogenesis. DAB2IP and SPRY2 are regulatory elements, which act as feedback inhibitors of receptor tyrosine kinases signaling in mitogen-activated protein kinase pathway. These elements have also been implicated in the pathophysiology of cancer. Therefore, this study is aimed to investigate the expression of all known splice variants of DAB2IP and SPRY2 in prostate tissue. Fresh Prostate tissue samples (50 prostate cancer/ matched normal tissue and 30 BPH) were collected and total RNA was extracted followed by cDNA synthesis. The expression of DAB2IP and SPRY2 transcript variants were evaluated using RT-PCR and quantitative Real-time PCR. The results indicated significant down-regulation of DAB2IP transcript variant 1 in cancerous tissues compared to paired normal tissues (P = 0.001) as well as SPRY2 transcript variant 2 in cancerous tissues in comparison with the normal counterparts and BPH (P = 0.008 and P = 0.025, respectively). In addition, there was a significant negative correlation between DAB2IP.1 and SPRY2.2 expression with PSA levels in prostate cancer (P = 0.039 ρ =-0.24 and P = 0.045 ρ =-0.3, respectively). Interestingly, the down-regulation of DAB2IP.1 mRNA and SPRY2.2 mRNA was positively correlated in tumor samples (P = 0.002 ρ = 0.434). For the first time, this experiment highlights the deregulation of DAB2IP and SPRY2 transcript variants in human prostate cancer. The present study confirms and extends the previous reports through indicating transcript-specific down-regulation and significant association of DAB2IP and SPRY2 in prostate tumorigenesis.

Disabled homolog 2 interactive protein functions as a tumor suppressor in osteosarcoma cells

The disabled homolog 2 interactive protein (DAB2IP) gene is a member of the family of Ras GTPases and functions as a tumor suppressor in many types of carcinoma; however, its function in osteosarcoma remains unclear. The aim of the present study was to determine the function of DAB2IP in osteosarcoma and normal bone cells in vitro. The expression of DAB2IP protein was assessed in osteoblast and osteosarcoma cell lines by western blot analysis. The effects of DAB2IP expression on cell proliferation, colony formation, apoptosis, cell cycle, and cell migration and invasion were evaluated by in vitro studies. DAB2IP expression was lower in osteosarcoma cell lines than in normal osteoblast cell lines. DAB2IP expression affected cell proliferation, apoptosis and cell cycle distribution. In addition, DAB2IP inhibited the migration and invasion of osteosarcoma and normal osteoblast cells. Therefore, DAB2IP may function as a tumor suppressor in osteosarcoma cell lines by inhibiting cell proliferation and invasion.

Down-regulation of DAB2IP promotes colorectal cancer invasion and metastasis by translocating hnRNPK into nucleus to enhance the transcription of MMP2

DOC-2/DAB2 interacting protein (DAB2IP) is a RasGAP protein that shows a suppressive effect on cancer progression. Our previous study showed the involvement of transcription regulation of DAB2IP in metastasis of colorectal cancer (CRC). However, the molecular mechanisms of DAB2IP in regulating the progression of CRC need to be further explored. Here, we identified heterogeneous nuclear ribonucleoprotein K (hnRNPK) and matrix metalloproteinase 2 (MMP2) as vital downstream targets of DAB2IP in CRC cells by two-dimensional fluorescence difference gel electrophoresis and cDNA microassay, respectively. Mechanistically, down-regulation of DAB2IP increased the level of hnRNPK through MAPK/ERK signaling pathway. Subsequently, translocation of hnRNPK into nucleus enhanced the transcription activity of MMP2, and therefore promoted invasion and metastasis of CRC. Down-regulation of DAB2IP correlated negatively with hnRNPK and MMP2 expressions in CRC tissues. In conclusion, our study elucidates a novel mechanism of the DAB2IP/hnRNPK/MMP2 axis in the regulation of CRC invasion and metastasis, which may be a potential therapeutic target.

Block one, unleash a hundred. Mechanisms of DAB2IP inactivation in cancer

One of the most defining features of cancer is aberrant cell communication; therefore, a molecular understanding of the intricate network established among tumor cells and their microenvironment could significantly improve comprehension and clinical management of cancer. The tumor suppressor DAB2IP (Disabled homolog 2 interacting protein), also known as AIP1 (ASK1 interacting protein), has an important role in this context, as it modulates signal transduction by multiple inflammatory cytokines and growth factors. DAB2IP is a Ras-GAP, and negatively controls Ras-dependent mitogenic signals. In addition, acting as a signaling adaptor, DAB2IP modulates other key oncogenic pathways, including TNFα/NF-κB, WNT/β-catenin, PI3K/AKT, and androgen receptors. Therefore, DAB2IP inactivation can provide a selective advantage to tumors initiated by a variety of driver mutations. In line with this role, DAB2IP expression is frequently impaired by methylation in cancer. Interestingly, recent studies reveal that tumor cells can employ other sophisticated mechanisms to disable DAB2IP at the post-transcriptional level. We review the mechanisms and consequences of DAB2IP inactivation in cancer, with the purpose to support and improve research aimed to counteract such mechanisms. We suggest that DAB2IP reactivation in cancer cells could be a strategy to coordinately dampen multiple oncogenic pathways, potentially limiting progression of a wide spectrum of tumors.

DAB2IP in cancer

DOC-2/DAB2 is a member of the disable gene family that features tumor-inhibiting activity. The DOC-2/DAB2 interactive protein, DAB2IP, is a new member of the Ras GTPase-activating protein family. It interacts directly with DAB2 and has distinct cellular functions such as modulating different signal cascades associated with cell proliferation, survival, apoptosis and metastasis. Recently, DAB2IP has been found significantly down regulated in multiple types of cancer. The aberrant alteration of DAB2IP in cancer is caused by a variety of mechanisms, including the aberrant promoter methylation, histone deacetylation, and others. Reduced expression of DAB2IP in neoplasm may indicate a poor prognosis of many malignant cancers. Moreover, DAB2IP stands for a promising direction for developing targeted therapies due to its capacity to inhibit tumor cell growth in vitro and in vivo. Here, we summarize the present understanding of the tumor suppressive role of DAB2IP in cancer progression; the mechanisms underlying the dysregulation of DAB2IP; the gene functional mechanism and the prospects of DAB2IP in the future cancer research.

The positive feedback between Snail and DAB2IP regulates EMT, invasion and metastasis in colorectal cancer

DAB2IP has been identified as a tumor suppressor in several cancers but its oncogenic role and transcriptionally regulatory mechanisms in the progression of colorectal carcinoma (CRC) remain unknown. In this study, DAB2IP was down-regulated in CRC tissues and a valuable prognostic marker for survival of CRC patients, especially in the late stage. Moreover, DAB2IP was sufficient to suppress proliferation, epithelial-mesenchymal transition (EMT), invasion and metastasis in CRC. Mechanically, the linear complex of EZH2/HDAC1/Snail contributed to DAB2IP silencing in CRC cells. The study further proved that the positive feedback loop between Snail and DAB2IP existed in CRC cells and DAB2IP was required for Snail-induced aggressive cell behaviors. Finally, DAB2IP correlated negatively with Snail and EZH2 expressions in CRC tissues. Our findings reveal the suppressive role and a novel regulatory mechanism of DAB2IP expression in the progression of CRC. DAB2IP may be a potential, novel therapeutic and prognostic target for clinical CRC patients.

Absence of DAB2IP promotes cancer stem cell like signatures and indicates poor survival outcome in colorectal cancer

Metastasis is a critical factor for the high mortality of colorectal cancer (CRC), but its mechanism is not completely understood. Epithelial-mesenchymal transition (EMT) is thought to play a key role in metastasis and also increases the cancer stem cell (CSC) feature that facilitates metastatic colonization. In this study, we investigated the biological roles of DAB2IP regulating EMT and stem cell-like features in human CRC. We demonstrate that DAB2IP suppresses NF-κB-mediated EMT and CSC features in CRC cells. In DAB2IP knockout mice, we discovered the hyperplasia in colonic epithelium which aberrantly represents the mesenchymal feature and NF-κB pathway activation. In clinic CRC tissue, we also reveal that reduced DAB2IP can enrich the CD133(+) subpopulation. DAB2IP expression was inversely correlated with tumor differentiation and metastasis, and patients with lower DAB2IP expression had shorter overall survival time. Taken together, our study demonstrates that DAB2IP inhibits NF-κB-inducing EMT and CSC to suppress the CRC progression, and also suggests that DAB2IP is a beneficial prediction factor for CRC patient prognosis.

Apoptosis in liver carcinogenesis and chemotherapy

Hepatocellular carcinoma (HCC) is a major health problem. In human hepatocarcinogenesis, the balance between cell death and proliferation is deregulated, tipping the scales for a situation where antiapoptotic signals are overpowering the death-triggering stimuli. HCC cells harbor a wide variety of mutations that alter the regulation of apoptosis and hence the response to chemotherapeutical drugs, making them resistant to the proapoptotic signals. Considering all these modifications found in HCC cells, therapeutic approaches need to be carefully studied in order to specifically target the antiapoptotic signals. This review deals with the recent relevant contributions reporting molecular alterations for HCC that lead to a deregulation of apoptosis, as well as the challenge of death-inducing chemotherapeutics in current HCC treatment.

Pretreatment biopsy analysis of DAB2IP identifies subpopulation of high-risk prostate cancer patients with worse survival following radiation therapy

Decreased expression of tumor suppressor DAB2IP is linked to aggressive cancer and radiation resistance in several malignancies, but clinical survival data is largely unknown. We hypothesized that pretreatment DAB2IP reduction would predict worse prostate cancer‐specific survival (PCSS). Immunohistochemistry of pretreatment biopsies was scored by an expert genitourinary pathologist. Other endpoints analyzed include freedom from biochemical failure (FFBF), castration resistance‐free survival (CRFS), and distant metastasis‐free survival (DMFS). Seventy‐nine patients with NCCN‐defined high‐risk prostate cancer treated with radiotherapy from 2005 to 2012 at our institution were evaluated. Twenty‐eight percent (22/79) of pretreatment biopsies revealed DAB2IP‐reduction. The median follow up times were 4.8 years and 5.3 years for patients in the DAB2IP‐reduced group and DAB2IP‐retained group, respectively. Patients with reduced DAB2IP demonstrated worse outcome compared to patients retaining DAB2IP, including FFBF (4‐year: 34 vs. 92%; P < 0.0001), CRFS (4‐year: 58 vs. 96%; P = 0.0039), DMFS (4‐year: 58 vs. 100%; P = 0.0006), and PCSS (5‐year: 83 vs. 100%; P = 0.0102). Univariate analysis showed T stage, N stage, and Gleason score were statistically significant variables. Pretreatment tumor DAB2IP status remained significant in multivariable analyses. This study suggests that about one‐fourth of men with high‐risk prostate cancer have decreased tumor expression of DAB2IP. This subpopulation with reduced DAB2IP has a suboptimal response and worse malignancy‐specific survival following radiation therapy and androgen deprivation. DAB2IP loss may be a genetic explanation for the observed differences in aggressive tumor characteristics and radiation resistance. Further study into improving treatment response and survival in this subpopulation is warranted.

A Novel Monoclonal Antibody Against Human DAB2IP

DAB2 interactive protein (DAB2IP), also known as ASK1-interacting protein-1 (AIP1), a novel member of the RasGTPase-activating protein family, plays a key role in tumor suppression during cancer progression and is highly expressed in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). To further explore its function as a cancer suppressor, in this study, we immunized BALB/c mice with synthesized human DAB2IP polypeptide and obtained a novel monoclonal antibody (MAb) against human DAB2IP. A stable strain of hybridoma was screened and successfully established by the hybridoma technique. The immunohistochemistry, immunocytochemistry, and Western blot analysis revealed that the MAb was directed against human DAB2IP with high specificity. Therefore, this MAb may be a useful tool and facilitate studies on tumorigenesis associated with DAB2IP.

The Ras/MAPK pathway and hepatocarcinoma: pathogenesis and therapeutic implications

BACKGROUND

Hepatocellular carcinoma (HCC) is still a major health problem, often diagnosed at an advanced stage. The multikinase inhibitor sorafenib is to date the sole approved systemic therapy. Several signalling pathways are implicated in tumour development and progression. Among these pathways, the Ras/MAPK pathway is activated in 50-100% of human HCCs and is correlated with a poor prognosis. The aim of this work was to review the main intracellular mechanisms leading to aberrant Ras pathway activation in HCC and the potential therapeutic implications.

MATERIALS AND METHODS

This review is based on the material found on PubMed up to December 2014. 'Ras signaling, Ras dysregulation, Ras inhibition, MAPK pathway, cancer, hepatocarcinoma and liver cancer' alone or in combination were the main terms used for online research.

RESULTS

Multiple mechanisms lead to the deregulation of the Ras pathway in liver cancer. Ras and Raf gene mutations are rare events in human hepatocarcinogenesis in contrast to experimental models in rodents. Downregulation of several Ras/MAPK pathway inhibitors such as GAPs, RASSF proteins, DUSP1, Sprouty and Spred proteins is largely implicated in the aberrant activation of this pathway in the context of wild-type Ras and Raf genes. Epigenetic or post-transcriptional mechanisms lead to the downregulation of these tumour suppressor genes.

CONCLUSION

Ras/MAPK pathway effectors may be considered as potential therapeutic targets in the field of HCC. In particular after the arrival of sorafenib, more Ras/MAPK inhibitors have emerged and are still in preclinical or clinical investigation for HCC therapy.

Expression of mouse Dab2ip transcript variants and gene methylation during brain development

Dab2ip (DOC-2/DAB2 interacting protein) is a RasGAP protein which shows a growth-inhibitory effect in human prostate cancer cell lines. Recent studies have shown that Dab2ip also plays an important role in regulating dendrite development and neuronal migration during brain development. In this study, we provide a more complete description of the mouse Dab2ip (mDab2ip) gene locus and examined DNA methylation and expression of Dab2ip during cerebellar development. Analysis of cDNA sequences in public databases revealed a total of 20 possible exons for mDab2ip gene, spanning over 172kb. Using Cap Analysis of Gene Expression (CAGE) data available through FANTOM5 project, we deduced five different transcription start sites for mDab2ip. Here, we characterized three different mDab2ip transcript variants beginning with exon 1. These transcripts varied by the presence or absence of exons 3 and 5, which encode a putative nuclear localization signal and the N-terminal region of a PH-domain, respectively. The 5' region of the mDab2ip gene contains three putative CpG islands (CpG131, CpG54, and CpG85). Interestingly, CpG54 and CpG85 are localized on exons 3 and 5. Bisulfate DNA sequencing showed that methylation level of CpG54 remained constant whereas methylation of CpG85 increased during cerebellar development. Real-time PCR analysis showed that the proportion of PH-domain containing mDab2ip transcripts increased during cerebellar development, in correlation with the increase in CpG85 methylation. These data suggest that site-specific methylation of mDab2ip gene during cerebellar development may play a role in inclusion of exon 5, resulting in a Dab2ip transcript variant that encodes a full pleckstrin homology (PH) domain.

The ATM inhibitor KU55933 sensitizes radioresistant bladder cancer cells with DAB2IP gene defect

PURPOSE

Our preliminary results showed that differentially expressed in ovarian cancer-2/disabled homolog 2 (DOC-2/DAB2) interactive protein (DAB2IP), a putative tumor suppressor gene, is down-regulated in bladder cancer (BCa) with aggressive phenotypes. In this study, we investigated how DAB2IP knockdown influenced BCa cell response to ionizing radiation (IR) and discussed possible ways to enhance cell radiosensitivity.

METHODS AND MATERIALS

The small interfering RNA (siRNA) system was implemented to inhibit endogenous DAB2IP expression in two human BCa cell lines, T24 and 5637. Cell sensitivity to IR alone or combined treatment was measured by a colony formation assay (CFA). Western blot was used to determine the phosphorylation levels of ataxia-telangiectasia mutated (ATM), catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) and related DNA damage repair (DDR) proteins. Immunofluorescence as well as a flow cytometry assay were employed to detect DNA double-strand break (DSB) repair and cell cycle distribution, respectively.

RESULTS

DAB2IP-knockdown of BCa cells (i.e., siDAB2IP) exhibit increased clonogenic survival in response to IR compared with control cells (i.e., siCON) expressing an endogenous level of DAB2IP. The mechanism in siDAB2IP cells could be explained by elevated ATM expression and activation, increased S phase cell distribution as well as faster DSB repair kinetics. 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one (KU55933) significantly sensitized siDAB2IP cells to IR due to inhibition of the phosphorylation of ATM and its downstream targets following IR and slower DSB repair kinetics.

CONCLUSIONS

Loss of DAB2IP expression in BCa cells signifies their radioresistance. KU55933, which suppresses ATM phosphorylation upon irradiation, could be applied in the radiotherapy of BCa patients with a DAB2IP gene defect.

Mutant p53 reprograms TNF signaling in cancer cells through interaction with the tumor suppressor DAB2IP

Inflammation is a significant factor in cancer development, and a molecular understanding of the parameters dictating the impact of inflammation on cancers could significantly improve treatment. The tumor suppressor p53 is frequently mutated in cancer, and p53 missense mutants (mutp53) can acquire oncogenic properties. We report that cancer cells with mutp53 respond to inflammatory cytokines increasing their invasive behavior. Notably, this action is coupled to expression of chemokines that can expose the tumor to host immunity, potentially affecting response to therapy. Mechanistically, mutp53 fuels NF-κB activation while it dampens activation of ASK1/JNK by TNFα, and this action depends on mutp53 binding and inhibiting the tumor suppressor DAB2IP in the cytoplasm. Interfering with such interaction reduced aggressiveness of cancer cells in xenografts. This interaction is an unexplored mechanism by which mutant p53 can influence tumor evolution, with implications for our understanding of the complex role of inflammation in cancer.

The role of homeostatic regulation between tumor suppressor DAB2IP and oncogenic Skp2 in prostate cancer growth

Altered DAB2IP gene expression often detected in prostate cancer (PCa) is due to epigenetic silencing. In this study, we unveil a new mechanism leading to the loss of DAB2IP protein; an oncogenic S-phase kinase-associated protein-2 (Skp2) as E3 ubiquitin ligase plays a key regulator in DAB2IP degradation. In order to unveil the role of Skp2 in the turnover of DAB2IP protein, both prostate cell lines and prostate cancer specimens with a variety of molecular and cell biologic techniques were employed. We demonstrated that DAB2IP is regulated by Skp2-mediated proteasome degradation in the prostate cell lines. Further analyses identified the N-terminal DAB2IP containing the ubiquitination site. Immunohistochemical study exhibited an inverse correlation between DAB2IP and Skp2 protein expression in the prostate cancer tissue microarray. In contrast, DAB2IP can suppressSkp2 protein expression is mediated through Akt signaling. The reciprocal regulation between DAB2IP and Skp2 can impact on the growth of PCa cells. This reciprocal regulation between DAB2IP and Skp2 protein represents a unique homeostatic balance between tumor suppressor and oncoprotein in normal prostate epithelia, which is apparently altered in cancer cells. The outcome of this study has identified new potential targets for developing new therapeutic strategy for PCa.

The mechanism of DAB2IP in chemoresistance of prostate cancer cells

PURPOSE

The docetaxel-based chemotherapy is the standard of care for castration-resistant prostate cancer (CRPC), inevitably, patients develop resistance and decease. Until now, the mechanism and predictive marker for chemoresistance are poorly understood.

EXPERIMENTAL DESIGN

Immortalized normal prostate and cancer cell lines stably manipulated with different DAB2IP expression levels were used and treated with chemotherapeutic drugs commonly used in prostate cancer therapy. Cell proliferation was measured using MTT assay; Western blot, quantitative PCR, and luciferase reporter assays were used to analyze Clusterin gene regulation by DAB2IP. Immunohistochemical analysis was conducted for evaluating DAB2IP, Clusterin and Egr-1 expression in human prostate cancer tissue.

RESULTS

DAB2IP Knockdown (KD) cells exhibited resistance to several chemotherapeutic drugs, whereas increased DAB2IP in C4-2 cells restored the drug sensitivity. Parallel, DAB2IP KD cells exhibited higher expression of Clusterin, an antiapoptotic factor, whereas elevated DAB2IP in C4-2 cells decreased Clusterin expression. Functionally, knocking down Clusterin by short-hairpin RNA or antisense oligonucleotide OGX-011 decreased drug resistance, whereas overexpressing Clusterin in C4-2 D2 enhanced drug resistance. Mechanistically, DAB2IP blocked the cross-talk between Wnt/β-catenin and IGF-I signaling, leading to the suppression of Egr-1 that is responsible for Clusterin expression. A similar result was observed in the prostate of DAB2IP knockout animals. In addition, we observed a significantly inverse correlation between DAB2IP and Egr-1 or Clusterin expression from clinical tissue microarray.

CONCLUSIONS

This study unveils a new regulation of the Egr-1/Clusterin signaling network by DAB2IP. Loss of DAB2IP expression in CRPC cells signifies their chemoresistance. Clusterin is a key target for developing more effective CRPC therapy.

The role of DAB2IP in androgen receptor activation during prostate cancer progression

Altered androgen-receptor (AR) expression and/or constitutively active AR are commonly associated with prostate cancer (PCa) progression. Targeting AR remains a focal point for designing new strategy of PCa therapy. Here, we have shown that DAB2IP, a novel tumor suppressor in PCa, can inhibit AR-mediated cell growth and gene activation in PCa cells via distinct mechanisms. DAB2IP inhibits the genomic pathway by preventing AR nuclear translocation or phosphorylation and suppresses the non-genomic pathway via its unique functional domain to inactivate c-Src. Also, DAB2IP is capable of suppressing AR activation in an androgen-independent manner. In addition, DAB2IP can inhibit several AR splice variants showing constitutive activity in PCa cells. In DAB2IP(-/-) mice, the prostate gland exhibits hyperplastic epithelia, in which AR becomes more active. Consistently, DAB2IP expression inversely correlates with AR activation status particularly in recurrent or metastatic PCa patients. Taken together, DAB2IP is a unique intrinsic AR modulator in normal cells, and likely can be further developed into a therapeutic agent for PCa.

Decreased expression of DAB2IP in pancreatic cancer with wild-type KRAS

BACKGROUND

KRAS mutation plays an important role in the pathogenesis of pancreatic cancer. However, the role of wild-type KRAS in the progression of pancreatic cancer remains unknown. The present study was to investigate the expression of the Ras GTPase activating protein (DAB2IP) in pancreatic cancer and its clinical significance.

METHODS

The expression of DAB2IP in pancreatic cancer cell lines and normal human pancreatic ductal epithelial cells was analyzed by Western blotting and real-time quantitative reverse transcription-PCR (qRT-PCR). The KRAS mutational types of pancreatic cancer tissues obtained from pancreatic cancer patients (n=20) were also analyzed. Subsequently, DAB2IP expression was detected in pancreatic cancer tissues, adjacent and normal pancreatic tissues (n=2) by immunohistochemistry, and the relationship between DAB2IP expression and the clinical characteristics of patients was evaluated.

RESULTS

Western blotting and qRT-PCR results showed that DAB2IP expression in pancreatic cancer cells with wild-type KRAS was lower than that in those with mutation-type KRAS and normal human pancreatic ductal epithelial cells (P<0.05). Immunohistochemistry showed that DAB2IP expression was lower in pancreatic cancer tissues than that in adjacent and normal pancreatic tissues (Z=-4.000, P=0.000). DAB2IP expression was lower in pancreatic cancer patients with the wild-type KRAS gene than that in those with KRAS mutations (WilcoxonW=35.000, P=0.042). Furthermore, DAB2IP expression in patients with perineurial invasion was lower than that in those without invasion (WilcoxonW=71.500, P=0.028). DAB2IP expression was lower in patients with more advanced stage than that in those with early clinical stage (WilcoxonW=54.000, P=0.002).

CONCLUSIONS

DAB2IP expression was reduced in patients with pancreatic cancer compared with those with no cancer. DAB2IP expression was correlated with the KRAS gene, perineurial invasion and clinical stage of the disease. Our data indicated that DAP2IP expression can be used as a potential prognostic indicator and a promising molecular target for therapeutic intervention in patients with pancreatic cancer.

Dab2ip regulates neuronal migration and neurite outgrowth in the developing neocortex

Dab2ip (DOC-2/DAB2 interacting protein) is a member of the Ras GTPase-activating protein (GAP) family that has been previously shown to function as a tumor suppressor in several systems. Dab2ip is also highly expressed in the brain where it interacts with Dab1, a key mediator of the Reelin pathway that controls several aspects of brain development and function. We found that Dab2ip is highly expressed in the developing cerebral cortex, but that mutations in the Reelin signaling pathway do not affect its expression. To determine whether Dab2ip plays a role in brain development, we knocked down or over expressed it in neuronal progenitor cells of the embryonic mouse neocortex using in utero electroporation. Dab2ip down-regulation severely disrupts neuronal migration, affecting preferentially late-born principal cortical neurons. Dab2ip overexpression also leads to migration defects. Structure-function experiments in vivo further show that both PH and GRD domains of Dab2ip are important for neuronal migration. A detailed analysis of transfected neurons reveals that Dab2ip down- or up-regulation disrupts the transition from a multipolar to a bipolar neuronal morphology in the intermediate zone. Knock down of Dab2ip in neurons ex-vivo indicates that this protein is necessary for proper neurite development and for the expression of several major neuronal microtubule associated proteins (MAPs), which are important for neurite growth and stabilization. Thus, our study identifies, for the first time, a critical role for Dab2ip in mammalian cortical development and begins to reveal molecular mechanisms that underlie this function.

New acquisition techniques: fields of application

Conventional MR imaging of the liver has a central role in the assessment of liver diseases. Diffusion-weighted MR imaging, MR elastography, and time-resolved dynamic contrast-enhanced MR imaging improve the anatomical information provided by conventional MR imaging and add quantitative functional information in diffuse and focal liver diseases. Particularly, accurate detection and characterization of liver fibrosis are feasible with quantitative MR elastography, detection of liver tumors is increased with diffusion-weighted MR imaging and time-resolved dynamic contrast-enhanced MR imaging, characterization of tumors can be improved with quantitative diffusion-weighted MR imaging and MR elastography. These methods also have the potential to provide adequate biomarkers for assessing the response to treatment. Currently, the main limitations of quantitative MR imaging are related to reproducibility, standardization, and/or limited clinical data. It is important to improve and standardize the quantitative MR methods and validate their role in large multicenter trials.

Low expression of DAB2IP contributes to malignant development and poor prognosis in hepatocellular carcinoma

BACKGROUND AND AIM

DOC-2/DAB2 interactive protein gene (DAB2IP) is a novel member of the Ras GTPase-activating protein family and plays a tumor suppressive role in cancer progression, but its function in hepatocellular carcinoma (HCC) remains unclear. This aims of this study were to analyze the clinicopathological features of DAB2IP expression in HCC, and to determine the effect of DAB2IP on HCC cell behaviors in vitro.

METHODS

The expression of DAB2IP was detected in hepatocyte cell line and HCC cell lines by real-time reverse transcription-polymerase chain reaction and western blot. DAB2IP expression was then examined in 120 cases of clinical paraffin-embedded HCC tissue by immunohistochemistry (IHC). 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT) method and in vitro invasive assay were finally performed to evaluate the effect of DAB2IP depletion on cell proliferation or invasion of HCC cells.

RESULTS

DAB2IP expression was lower in HCC cell lines or tissues than in hepatocyte cell lines, adjacent cirrhotic livers or normal livers (P < 0.05). Its expression was positively correlated with tumor size (P = 0.01). Patients with lower DAB2IP expression had shorter overall survival time (P = 0.013). DAB2IP suppresses proliferation and invasion of HCC cells in vitro.

CONCLUSION

DAB2IP is a valuable marker for progression of HCC patients. Downregulation of DAB2IP is associated with poor prognosis in HCC patients. DAB2IP silence alone is sufficient to promote HCC cell proliferation and invasion in vitro.

miRNA signatures associate with pathogenesis and progression of osteosarcoma

Osteosarcoma remains a leading cause of cancer death in adolescents. Treatment paradigms and survival rates have not improved in two decades. Driving the lack of therapeutic inroads, the molecular etiology of osteosarcoma remains elusive. MicroRNAs (miRNAs) have demonstrated far-reaching effects on the cellular biology of development and cancer. Their role in osteosarcomagenesis remains largely unexplored. Here we identify for the first time an miRNA signature reflecting the pathogenesis of osteosarcoma from surgically procured samples from human patients. The signature includes high expression of miR-181a,miR-181b, and miR-181c as well as reduced expression of miR-16, miR-29b, and miR-142-5p. We also demonstrate that miR-181b and miR-29b exhibit restricted expression to distinct cell populations in the tumor tissue. Further, higher expression of miR-27a and miR-181c* in pre-treatment biopsy samples characterized patients who developed clinical metastatic disease. In addition, higher expression of miR-451 and miR-15b in pre-treatment samples correlated with subsequent positive response to chemotherapy. In vitro and in vivo functional validation in osteosarcoma cell lines confirmed the tumor suppressive role of miR-16 and the pro-metastatic role of miR-27a. Furthermore, predicted target genes for miR-16 and miR-27a were confirmed as down-regulated by real-time PCR. Affymetrix array profiling of cDNAs from the osteosarcoma specimens and controls were interrogated according to predicted targets of miR-16, miR142-5p, miR-29b, miR-181a/b, and miR-27a. This analysis revealed positive and negative correlations highlighting pathways of known importance to osteosarcoma, as well as novel genes. Thus, our findings establish a miRNA signature associated with pathogenesis of osteosarcoma as well as critical pre-treatment biomarkers of metastasis and responsiveness to therapy.

Differential Regulation of RasGAPs in Cancer

Ever since their discovery as cellular counterparts of viral oncogenes more than 25 years ago, much progress has been made in understanding the complex networks of signal transduction pathways activated by oncogenic Ras mutations in human cancers. The activity of Ras is regulated by nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), and much emphasis has been put into the biochemical and structural analysis of the Ras/GAP complex. The mechanisms by which GAPs catalyze Ras-GTP hydrolysis have been clarified and revealed that oncogenic Ras mutations confer resistance to GAPs and remain constitutively active. However, it is yet unclear how cells coordinate the large and divergent GAP protein family to promote Ras inactivation and ensure a certain biological response. Different domain arrangements in GAPs to create differential protein-protein and protein-lipid interactions are probably key factors determining the inactivation of the 3 Ras isoforms H-, K-, and N-Ras and their effector pathways. In recent years, in vitro as well as cell- and animal-based studies examining GAP activity, localization, interaction partners, and expression profiles have provided further insights into Ras inactivation and revealed characteristics of several GAPs to exert specific and distinct functions. This review aims to summarize knowledge on the cell biology of RasGAP proteins that potentially contributes to differential regulation of spatiotemporal Ras signaling.

Recognition and suppression of transfected plasmids by protein ZNF511-PRAP1, a potential molecular barrier to transgene expression

Nonviral vectors present considerable advantages over viral counterparts in gene transfer. However, the poor expression efficiency of the transfected genes poses a challenge for their use in gene therapy, primarily due to the inability of these vectors to overcome various barriers, including the biological barriers. Here, we report that ZNF511-PRAP1 may be involved in the recognition and inactivation of transfected plasmids. ZNF511-PRAP1 is induced by transfection of plasmid DNA and suppresses the transcription of transfected plasmids. It binds directly to the p21 promoter in transfected plasmids but not the endogenous counterpart. Similarly, ZNF511-PRAP1 suppresses the expression of the green fluorescent protein reporter gene on transiently transfected plasmids but not an integrated red fluorescence reporter gene with the same cytomegalovirus (CMV) promoter. Therefore, ZNF511-PRAP1 is able to differentiate between exogenous/nonintegrated and endogenous/integrated DNA. The suppression by ZNF511-PRAP1 is independent of DNA methylation and can be abolished by trichostatin A (TSA) treatment and knockdown of HDAC2 and/or ZNF511-PRAP1. Furthermore, ZNF511-PRAP1 interacts directly with HDAC2. Our results revealed that transfected plasmids are recognized by ZNF511-PRAP1 and suppressed by a repressor complex comprising ZNF511-PRAP1 and HDAC2 and suggest that ZNF511-PRAP1 could play a role as a potential molecular barrier in nonviral transgene expression.

Inactivation of Ras GTPase-activating proteins promotes unrestrained activity of wild-type Ras in human liver cancer

BACKGROUND & AIMS

Aberrant activation of the RAS pathway is ubiquitous in human hepatocarcinogenesis, but the molecular mechanisms leading to RAS induction in the absence of RAS mutations remain under-investigated. We defined the role of Ras GTPase activating proteins (GAPs) in the constitutive activity of Ras signaling during human hepatocarcinogenesis.

METHODS

The mutation status of RAS genes and RAS effectors was assessed in a collection of human hepatocellular carcinomas (HCC). Levels of RAS GAPs (RASA1-4, RASAL1, nGAP, SYNGAP1, DAB2IP, and NF1) and the RASAL1 upstream inducer PITX1 were determined by real-time RT-PCR and immunoblotting. The promoter and genomic status of RASAL1, DAB2IP, NF1, and PITX1 were assessed by methylation assays and microsatellite analysis. Effects of RASAL1, DAB2IP, and PITX1 on HCC growth were evaluated by transfection and siRNA analyses of HCC cell lines.

RESULTS

In the absence of Ras mutations, downregulation of at least one RAS GAP (RASAL1, DAB2IP, or NF1) was found in all HCC samples. Low levels of DAB2IP and PITX1 were detected mostly in a HCC subclass from patients with poor survival, indicating that these proteins control tumor aggressiveness. In HCC cells, reactivation of RASAL1, DAB2IP, and PITX1 inhibited proliferation and induced apoptosis, whereas their silencing increased proliferation and resistance to apoptosis.

CONCLUSIONS

Selective suppression of RASAL1, DAB2IP, or NF1 RAS GAPs results in unrestrained activation of Ras signaling in the presence of wild-type RAS in HCC.

Identifying genes progressively silenced in preneoplastic and neoplastic liver tissues

High-throughput genomic technologies are increasingly being used to identify therapeutic targets and risk factors for specific diseases. Using 116 independent liver samples, we identified 793 probe sets that demonstrated a significant association in the frequency of absent calls as tissues progressed from normal to pre-neoplastic to neoplastic, followed by a bioinformatic approach which identified that 78.9% of the significant probe sets contained at least one CpG island in the gene promoter region compared with 58.9% of the remaining genes examined. Our results indicate that further high-throughput methylation studies to more fully characterize molecular events involved in hepatocarcinogenesis are warranted.

Genome-wide association study identifies a sequence variant within the DAB2IP gene conferring susceptibility to abdominal aortic aneurysm

We performed a genome-wide association study on 1,292 individuals with abdominal aortic aneurysms (AAAs) and 30,503 controls from Iceland and The Netherlands, with a follow-up of top markers in up to 3,267 individuals with AAAs and 7,451 controls. The A allele of rs7025486 on 9q33 was found to associate with AAA, with an odds ratio (OR) of 1.21 and P = 4.6 x 10(-10). In tests for association with other vascular diseases, we found that rs7025486[A] is associated with early onset myocardial infarction (OR = 1.18, P = 3.1 x 10(-5)), peripheral arterial disease (OR = 1.14, P = 3.9 x 10(-5)) and pulmonary embolism (OR = 1.20, P = 0.00030), but not with intracranial aneurysm or ischemic stroke. No association was observed between rs7025486[A] and common risk factors for arterial and venous diseases-that is, smoking, lipid levels, obesity, type 2 diabetes and hypertension. Rs7025486 is located within DAB2IP, which encodes an inhibitor of cell growth and survival.

C/EBPalpha is up-regulated in a subset of hepatocellular carcinomas and plays a role in cell growth and proliferation

BACKGROUND & AIMS

C/EBPalpha (cebpa) is a putative tumor suppressor. However, initial results indicated that cebpa was up-regulated in a subset of human hepatocellular carcinomas (HCCs). The regulation and function of C/EBPalpha was investigated in HCC cell lines to clarify its role in liver carcinogenesis.

METHODS

The regulation of C/EBPalpha expression was studied by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), Western blotting, immunohistochemistry, methylation-specific PCR, and chromatin immunoprecipitation assays. C/EBPalpha expression was knocked-down by small interfering RNA or short hairpin RNA. Functional assays included colony formation, methylthiotetrazole, bromodeoxyuridine incorporation, and luciferase-reporter assays.

RESULTS

Cebpa was up-regulated at least 2-fold in a subset (approximately 55%) of human HCCs compared with adjacent nontumor tissues. None of the up-regulated samples were positive for hepatitis C infection. The HCC cell lines Hep3B and Huh7 expressed high, PLC/PRF/5 intermediate, HepG2 and HCC-M low levels of C/EBPalpha, recapitulating the pattern of expression observed in HCCs. No mutations were detected in the CEBPA gene in HCCs and cell lines. C/EBPalpha was localized to the nucleus and functional in Hep3B and Huh7 cells; knocking-down its expression reduced target-gene expression, colony formation, and cell growth, associated with a decrease in cyclin A and CDK4 concentrations and E2F transcriptional activity. Epigenetic mechanisms including DNA methylation, and the binding of acetylated histone H3 to the CEBPA promoter-regulated cebpa expression in the HCC cells.

CONCLUSIONS

C/EBPalpha is up-regulated in a subset of HCCs and has growth-promoting activities in HCC cells. Novel oncogenic mechanisms involving C/EBPalpha may be amenable to epigenetic regulation to improve treatment outcomes.

High-throughput assessment of CpG site methylation for distinguishing between HCV-cirrhosis and HCV-associated hepatocellular carcinoma

Methylation of promoter CpG islands has been associated with gene silencing and demonstrated to lead to chromosomal instability. Therefore, some postulate that aberrantly methylated CpG regions may be important biomarkers indicative of cancer development. In this study we used the Illumina GoldenGate Methylation BeadArray Cancer Panel I for simultaneously profiling methylation of 1,505 CpG sites in order to identify methylation differences in 76 liver tissues ranging from normal to pre-neoplastic and neoplastic states. CpG sites for ESR1, GSTM2, and MME were significantly differentially methylated when comparing the pre-neoplastic tissues from patients with concomitant hepatocellular carcinoma (HCC) to the pre-neoplastic tissues from patients without HCC. When comparing paired HCC tissues to their corresponding pre-neoplastic non-tumorous tissues, eight CpG sites, including one CpG site that was hypermethylated (APC) and seven (NOTCH4, EMR3, HDAC9, DCL1, HLA-DOA, HLA-DPA1, and ERN1) that were hypomethylated in HCC, were identified. Our study demonstrates that high-throughput methylation technologies may be used to identify differentially methylated CpG sites that may prove to be important molecular events involved in carcinogenesis.

Role of DAB2IP in modulating epithelial-to-mesenchymal transition and prostate cancer metastasis

A single nucleotide polymorphism in the DAB2IP gene is associated with risk of aggressive prostate cancer (PCa), and loss of DAB2IP expression is frequently detected in metastatic PCa. However, the functional role of DAB2IP in PCa remains unknown. Here, we show that the loss of DAB2IP expression initiates epithelial-to-mesenchymal transition (EMT), which is visualized by repression of E-cadherin and up-regulation of vimentin in both human normal prostate epithelial and prostate carcinoma cells as well as in clinical prostate-cancer specimens. Conversely, restoring DAB2IP in metastatic PCa cells reversed EMT. In DAB2IP knockout mice, prostate epithelial cells exhibited elevated mesenchymal markers, which is characteristic of EMT. Using a human prostate xenograft-mouse model, we observed that knocking down endogenous DAB2IP in human carcinoma cells led to the development of multiple lymph node and distant organ metastases. Moreover, we showed that DAB2IP functions as a scaffold protein in regulating EMT by modulating nuclear beta-catenin/T-cell factor activity. These results show the mechanism of DAB2IP in EMT and suggest that assessment of DAB2IP may provide a prognostic biomarker and potential therapeutic target for PCa metastasis.

DAB2IP coordinates both PI3K-Akt and ASK1 pathways for cell survival and apoptosis

In metastatic prostate cancer (PCa) cells, imbalance between cell survival and death signals such as constitutive activation of phosphatidylinositol 3-kinase (PI3K)-Akt and inactivation of apoptosis-stimulated kinase (ASK1)-JNK pathways is often detected. Here, we show that DAB2IP protein, often down-regulated in PCa, is a potent growth inhibitor by inducing G(0)/G(1) cell cycle arrest and is proapoptotic in response to stress. Gain of function study showed that DAB2IP can suppress the PI3K-Akt pathway and enhance ASK1 activation leading to cell apoptosis, whereas loss of DAB2IP expression resulted in PI3K-Akt activation and ASK1-JNK inactivation leading to accelerated PCa growth in vivo. Moreover, glandular epithelia from DAB2IP(-/-) animal exhibited hyperplasia and apoptotic defect. Structural functional analyses of DAB2IP protein indicate that both proline-rich (PR) and PERIOD-like (PER) domains, in addition to the critical role of C2 domain in ASK1 activity, are important for modulating PI3K-Akt activity. Thus, DAB2IP is a scaffold protein capable of bridging both survival and death signal molecules, which implies its role in maintaining cell homeostasis.

Down-regulation of Rap1GAP via promoter hypermethylation promotes melanoma cell proliferation, survival, and migration

Melanoma is the most serious, highly aggressive form of skin cancer with recent dramatic increases in incidence. Current therapies are relatively ineffective, highlighting the need for a better understanding of the molecular mechanisms contributing to the disease. We have previously shown that activation of Rap1 promotes melanoma cell proliferation and migration through the mitogen-activated protein kinase pathway and integrin activation. In the present study, we show that expression of Rap1GAP, a specific negative regulator of Rap1, is decreased in human melanoma tumors and cell lines. Overexpression of Rap1GAP in melanoma cells blocks Rap1 activation and extracellular signal-regulated kinase (ERK) phosphorylation and inhibits melanoma cell proliferation and survival. In addition, overexpression of Rap1GAP also inhibits focal adhesion formation and decreases melanoma cell migration. Rap1GAP down-regulation is due to its promoter methylation, a mechanism of gene silencing in tumors. Furthermore, treatment of melanoma cells with the demethylating agent 5-aza-2'-deoxycytidine reinduces Rap1GAP expression, followed by decreased Rap1 activity, ERK phosphorylation, and cell proliferation and survival-changes that are significantly blunted in cells transfected by small interfering RNA-mediated Rap1GAP knockdown. Taken together, our findings indicate that down-regulation of Rap1GAP via promoter hypermethylation promotes melanoma cell proliferation, survival, and migration.

The tumor suppressor gene DLEC1 is frequently silenced by DNA methylation in hepatocellular carcinoma and induces G1 arrest in cell cycle

BACKGROUND/AIMS

The chromosome locus 3p21.3 is a "hot-spot" for chromosomal aberrations and loss of heterozygosity in cancers. The 35 genes mapped to the AP20 subregion of this locus were screened for their expression to identify candidate tumor suppressor genes. DLEC1 was selected for further characterization in primary hepatocellular carcinomas and cell lines.

METHODS

RT-PCR and methylation-specific PCR were performed to examine the expression and methylation. Stable clones with DLEC1 overexpression were established to analyze cell proliferation and cell cycle.

RESULTS

DLEC1 was silenced and hypermethylated in 9 of 11 cell lines examined. Treatment with 5-aza-2'-deoxycytidine reversed the methylation and restored DLEC1 expression. The correlation between hypermethylation and expression was also demonstrated in 10 pairs of hepatocellular carcinoma and adjacent normal tissues (t-test, p<0.05). Hypermethylation of DLEC1 was detected in 70.6% of tumors, compared to 10.3% in normal tissues (n=68, p<0.001, chi(2)). Of interest, DLEC1 methylation was associated with the AJCC staging of the tumors (p=0.036, chi(2)). DLEC1 over-expression in cell lines decreased colony formation, cell growth and cell size, and induced a G1 arrest in cell cycle.

CONCLUSIONS

Our data indicate that DLEC1 is a candidate tumor suppressor gene that plays an important role in the development and progression of hepatocellular carcinoma.

Telbivudine in the treatment of chronic hepatitis B

Treatment of chronic hepatitis B with oral nucleos(t)ide analogs is evolving rapidly with newer compounds gaining approval. Recently, the US FDA and European Medicines Agency (EMEA) have approved telbivudine, a potent anti-hepatitis B virus (HBV)-specific agent with a hitherto excellent safety profile. This review focuses on the efficacy of this agent in chronic hepatitis B compared with lamivudine, evaluated clinically in Phase II and a large Phase III study. Monitoring of the virologic response under treatment with sensitive HBV-DNA assays has been applied, aiming at increasing efficacy and reducing HBV resistance. The results are critically presented and the evolving concept of effective long-term telbivudine and other nucleos(t)ide analog therapy, predicted by the extent of suppression of HBV replication at week 24, are analyzed and discussed.