Gene Summary

Gene:DLC1; DLC1 Rho GTPase activating protein
Aliases: HP, ARHGAP7, STARD12, p122-RhoGAP
Summary:This gene encodes a GTPase-activating protein (GAP) that is a member of the rhoGAP family of proteins which play a role in the regulation of small GTP-binding proteins. GAP family proteins participate in signaling pathways that regulate cell processes involved in cytoskeletal changes. This gene functions as a tumor suppressor gene in a number of common cancers, including prostate, lung, colorectal, and breast cancers. Multiple transcript variants due to alternative promoters and alternative splicing have been found for this gene.[provided by RefSeq, Apr 2010]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:rho GTPase-activating protein 7
Source:NCBIAccessed: 15 March, 2017


What does this gene/protein do?
Show (35)

Cancer Overview

DLC1 is a tumor suppressor gene which is underexpressed in a wide range of solid tumors. The gene was identified in a region freqiently deleted in hepatocellular carcinoma and other cancers. The gene is silenced in some cancers due to DNA methylation / hypermethylation of the promotor region for the gene (Yuan et al (2003)).

Research Indicators

Publications Per Year (1992-2017)
Graph generated 15 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 15 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: DLC1 (cancer-related)

Liu Y, Zhou J, Hu Y, et al.
Curcumin inhibits growth of human breast cancer cells through demethylation of DLC1 promoter.
Mol Cell Biochem. 2017; 425(1-2):47-58 [PubMed] Related Publications
The heterogeneity of breast cancer makes it a challenging solid tumor to diagnose and treat. A tumor suppressor Deleted in Liver Cancer 1 (DLC1) has been reported to be down-regulated or even silenced in several kinds of cancer including breast cancer. Curcumin has been reported to modulate the growth of tumor cells through regulation of multiple cell signaling pathways and modulate epigenetic changes by CpG demethylation of many tumor suppressor genes. This study was designed to investigate the effect of curcumin on the expression of Deleted in Liver Cancer 1 (DLC1) in human breast cancer cell line MDA-MB-361 and the underlying mechanism in vitro and in vivo. Curcumin induced DLC1 expression in a dose-dependent manner. In curcumin-treated cells, methylation of DLC1 promoter was reduced and active forms of RhoA and Cdc42 were also decreased. DLC1 expression was closely related to tumor cell growth, demonstrated by Ki67 staining. Curcumin inhibited DNA methyltransferase 1 expression through down-regulation of transcription factor Sp1. Consistent with the in vitro data, in vivo administration of curcumin inhibited the growth of implanted MDA-MB-361 cells and induced DLC1 expression in tumor tissue. In MDA-MB-361 cells, curcumin down-regulates the expression of Sp1 to inhibit the expression of DNA methyltransferase 1, thus subsequently reducing hypermethylation of DLC1 promoter to induce DLC1 expression.

Ding X, Gao S, Yang Q
rs621554 single nucleotide polymorphism of DLC1 is associated with breast cancer susceptibility and prognosis.
Mol Med Rep. 2016; 13(5):4095-100 [PubMed] Related Publications
Deleted in liver cancer 1 (DLC1) on chromosome 8p22, is an important tumor suppressor gene originally identified to be deleted in hepatocellular carcinoma. It can regulate the structure of the actin cytoskeleton and inhibit cell proliferation, motility and angiogenesis, which predominantly depends on its homology to rat RhoGAP. There are many genetic variants in DLC1, which may influence its antitumor efficacy. The rs621554 (IVS19+108C>T) polymorphism is a synonymous single nucleotide polymorphism (SNP) previously found to be associated with hepatocellular carcinoma. In the present study, 453 patients with breast cancer and 330 healthy females were analyzed using a cycling probe method. It was determined that the rs621554 polymorphism of DLC1 was associated with breast cancer susceptibility, with the CC and CT genotypes resulting in a higher risk of developing breast cancer. In regard to clinicopathological variables, it was demonstrated that the CT and CC genotype were associated with tumor size, lymph node metastasis and progesterone receptor status. Patients with the CT and CC genotype had shorter disease-free survival and overall survival rates compared with those with the TT genotype. Additionally, it was demonstrated that the rs621554 polymorphism was correlated with DLC1 expression at the mRNA level. These results suggested that the rs621554 polymorphism is associated with breast cancer susceptibility and prognosis, and may serve as a biomarker for breast cancer development and progression.

Zhu W, Ma L, Yang B, et al.
Flavone inhibits migration through DLC1/RhoA pathway by decreasing ROS generation in breast cancer cells.
In Vitro Cell Dev Biol Anim. 2016; 52(5):589-97 [PubMed] Related Publications
Tumor suppressor protein deleted in liver cancer 1 (DLC1) is a RhoGTPase-activating protein (RhoGAP) and inhibits cancer cell migration by inactivating downstream target protein RhoA. A few studies have reported the regulations of reactive oxygen species (ROS) on RhoGAP. In this study, we investigated flavone (the core structure of flavonoids)-induced regulation on ROS generation and DLC1/RhoA pathway in MCF-7 and MDA-MB-231 breast cancer cells and explored whether flavone-induced upregulation of DLC1 is mediated by ROS. Our results showed that flavone decreased ROS production and inhibited cell migration through DLC1/RhoA pathway. To further investigate the role of ROS in flavone-induced regulation on DLC1/RhoA pathway, hydrogen peroxide was added to restore the ROS levels. Flavone-induced upregulation of DLC1 expression, downregulation of RhoA activity, and inhibition of cell migration were all restrained by hydrogen peroxide. We also found that flavone increased DLC1 stability by inhibiting DLC1 protein degradation in breast cancer cells. In summary, our study demonstrated that flavone inhibited cell migration through DLC1/RhoA pathway by decreasing ROS generation and suppressed DLC1 degradation in MCF-7 and MDA-MB-231 breast cancer cells.

Song LJ, Liu Q, Meng XR, et al.
DLC-1 is an independent prognostic marker and potential therapeutic target in hepatocellular cancer.
Diagn Pathol. 2016; 11:19 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The 5-year survival rate of patients with hepatocellular cancer (HCC) was very low because of invasion and metastasis in the early stage. Biomarkers might help predict early occurrence of invasion and metastasis. Accumulating evidence has shown that deleted in liver cancer-1 (DLC1) may be considered as a metastasis suppressor gene in numerous solid and hematological cancers. However, its prognostic role and mechanisms that regulate and coordinate these activities remain poorly understood.
METHODS: With the method of immunohistochemistry, the expression of DLC-1 as well as Rho A, ROCK2, moesin had been characterized in 80 HCC tissues and adjacent noncancerous tissues. The correlation between their expression and their relationships with clinicopathological characteristics of HCC were also investigated. In addition, the prognostic value of DLC1 expression within the tumor tissues was assessed by Cox regression and Kaplan-Meier analysis.
RESULTS: DLC1 expression was significantly lower in HCC tissues than in adjacent noncancerous tissues, and DLC-1 expression was found to be negatively correlated with tumor differentiation, TNM stage and lymph node metastasis. Furthermore, DLC-1 expression was found to inversely correlate with Rho A, ROCK2 and moesin which were all highly expressed in HCC tissues. Kaplan-Meier analysis showed that significantly longer 5-year survival rate was seen in HCC patients with higher DLC1 expression, compared to those with lower expression of DLC1. Multivariate Cox proportional hazard analyses revealed that DLC1 was an independent factor affecting the overall survival probability.
CONCLUSION: DLC1 could be served as a tumor suppressor gene in the progression especially in the invasion and metastasis of HCC. DLC1 perhaps played its role by regulating the expression of Rho A, ROCK2 and moesin. Evaluation of the expression of DLC-1 might be a good prognostic marker for patients with HCC.

Jiang Y, Li JM, Luo HQ
Clinicopathological Significance of DLC-1 Expression in Cancer: a Meta-Analysis.
Asian Pac J Cancer Prev. 2015; 16(16):7255-60 [PubMed] Related Publications
BACKGROUND: Recent reports have shown that DLC-1 is widely expressed in normal tissues and is down- regulated in a wide range of human tumors, suggesting it may act as a tumor suppressor gene. We conducted a meta-analysis to determine the correlation between DLC-1 expression and clinicopathological characteristics in cancers.
MATERIALS AND METHODS: A detailed literature search was made for relevant publications from PubMed, EMBASE, Cochrane library databases, Web of Science, CNKI. The methodological quality of the studies was also evaluated. Analyses of pooled data were performed and odds ratios (ORs) were calculated and summarized.
RESULTS: Final analysis was performed of 1,815 cancer patients from 19 eligible studies. We observed that DLC- 1 expression was significantly lower in cancers than in normal tissues. DLC-1 expression was not found to be associated with tumor differentiation status. However, DLC-1 expression was obviously lower in advance stage than in early-stage cancers and was more down-regulated in metastatic than non-metastatic cancers.
CONCLUSIONS: The results of our meta-analysis suggested that DLC-1 expression is significantly lower in cancers than in normal tissues. Aberrant DLC-1 expression may play an important role in cancer genesis and metastasis.

Park H, Cho SY, Kim H, et al.
Genomic alterations in BCL2L1 and DLC1 contribute to drug sensitivity in gastric cancer.
Proc Natl Acad Sci U S A. 2015; 112(40):12492-7 [PubMed] Free Access to Full Article Related Publications
Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide. Recent high-throughput analyses of genomic alterations revealed several driver genes and altered pathways in GC. However, therapeutic applications from genomic data are limited, largely as a result of the lack of druggable molecular targets and preclinical models for drug selection. To identify new therapeutic targets for GC, we performed array comparative genomic hybridization (aCGH) of DNA from 103 patients with GC for copy number alteration (CNA) analysis, and whole-exome sequencing from 55 GCs from the same patients for mutation profiling. Pathway analysis showed recurrent alterations in the Wnt signaling [APC, CTNNB1, and DLC1 (deleted in liver cancer 1)], ErbB signaling (ERBB2, PIK3CA, and KRAS), and p53 signaling/apoptosis [TP53 and BCL2L1 (BCL2-like 1)] pathways. In 18.4% of GC cases (19/103), amplification of the antiapoptotic gene BCL2L1 was observed, and subsequently a BCL2L1 inhibitor was shown to markedly decrease cell viability in BCL2L1-amplified cell lines and in similarly altered patient-derived GC xenografts, especially when combined with other chemotherapeutic agents. In 10.9% of cases (6/55), mutations in DLC1 were found and were also shown to confer a growth advantage for these cells via activation of Rho-ROCK signaling, rendering these cells more susceptible to a ROCK inhibitor. Taken together, our study implicates BCL2L1 and DLC1 as potential druggable targets for specific subsets of GC cases.

Basak P, Dillon R, Leslie H, et al.
The Deleted in Liver Cancer 1 (Dlc1) tumor suppressor is haploinsufficient for mammary gland development and epithelial cell polarity.
BMC Cancer. 2015; 15:630 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Deleted in Liver Cancer 1 (Dlc1) is a tumor suppressor gene, which maps to human chromosome 8p21-22 and is found frequently deleted in many cancers including breast cancer. The promoter of the remaining allele is often found methylated. The Dlc1 gene encodes a RhoGAP protein that regulates cell proliferation, migration and inhibits cell growth and invasion when restored in Dlc1 deficient tumor cell lines. This study focuses on determining the role of Dlc1 in normal mammary gland development and epithelial cell polarity in a Dlc1 gene trapped (gt) mouse.
METHODS: Mammary gland whole mount preparations from 10-week virgin heterozygous Dlc1(gt/+) gene-trapped mice were compared with age-matched wild type (WT) controls. Hematoxylin-Eosin (H&E) and Masson's Trichrome staining of histological sections were carried out. Mammary glands from Dlc1(gt/+) mice and WT controls were enzymatically digested with collagenase and dispase and then cultured overnight to deplete hematopoietic and endothelial cells. The single cell suspensions were then cultured in Matrigel for 12 days. To knockdown Dlc1 expression, primary WT mammary epithelial cells were infected with short hairpin (sh) RNA expressing lentivirus or with a scrambled shRNA control.
RESULTS: Dlc1(gt/+) mice showed anomalies in the mammary gland that included increased ductal branching and deformities in terminal end buds and branch points. Compared to the WT controls, Masson's Trichrome staining showed a thickened stromal layer with increased collagen deposition in mammary glands from Dlc1(gt/+) mice. Dlc1(gt/+) primary mammary epithelial cells formed increased solid acinar spheres in contrast with WT and scrambled shRNA control cells, which mostly formed hollow acinar structures when plated in 3D Matrigel cultures. These solid acinar structures were similar to the acinar structures formed when Dlc1 gene expression was knocked down in WT mammary cells by shRNA lentiviral transduction. The solid acinar structures were not due to a defect in apoptosis as determined by a lack of detectible cleaved caspase 3 antibody staining. Primary mammary cells from Dlc1(gt/+) mice showed increased RhoA activity compared with WT cells.
CONCLUSIONS: The results illustrate that decreased Dlc1 expression can disrupt the normal cell polarization and mammary ductal branching. Altogether this study suggests that Dlc1 plays a role in maintaining normal mammary epithelial cell polarity and that Dlc1 is haploinsufficient.

Ibrahim FF, Jamal R, Syafruddin SE, et al.
MicroRNA-200c and microRNA-31 regulate proliferation, colony formation, migration and invasion in serous ovarian cancer.
J Ovarian Res. 2015; 8:56 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Serous epithelial ovarian cancer (SEOC) is a highly metastatic disease and its progression has been implicated with microRNAs. This study aimed to identify the differentially expressed microRNAs in Malaysian patients with SEOC and examine the microRNAs functional roles in SEOC cells.
METHODS: Twenty-two SEOC and twenty-two normal samples were subjected to miRNA expression profiling using the locked nucleic acid (LNA) quantitative real-time PCR (qPCR). The localization of miR-200c was determined via LNA in situ hybridization (ISH). Functional analysis of miR-200c and miR-31 on cell proliferation, migration and invasion and clonogenic cell survival were assessed in vitro. The putative target genes of the two miRNAs were predicted by miRWalk program and expression of the target genes in SEOC cell lines was validated.
RESULTS: The miRNA expression profiling revealed thirty-eight significantly dysregulated miRNAs in SEOC compared to normal ovarian tissues. Of these, eighteen were up-regulated whilst twenty miRNAs were down-regulated. We observed chromogenic miR-200c-ISH signal predominantly in the cytoplasmic compartment of both epithelial and inflammatory cancer cells. Re-expression of miR-200c significantly increased the cell proliferation and colony formation but reduced the migration and invasion of SEOC cells. In addition, miR-200c expression was inversely proportionate with the expression of deleted in liver cancer-1 (DLC-1) gene. Over-expression of miR-31 in SEOC cells resulted in decreased cell proliferation, clonogenic potential, cell migration and invasion. Meanwhile, miR-31 gain-of-function led to the down-regulation of AF4/FMR2 family member 1 (AFF1) gene.
CONCLUSIONS: These data suggested that miR-200c and miR-31 may play roles in the SEOC metastasis biology and could be considered as promising targets for therapeutic purposes.

Torabi K, Miró R, Fernández-Jiménez N, et al.
Patterns of somatic uniparental disomy identify novel tumor suppressor genes in colorectal cancer.
Carcinogenesis. 2015; 36(10):1103-10 [PubMed] Free Access to Full Article Related Publications
Colorectal cancer (CRC) is characterized by specific patterns of copy number alterations (CNAs), which helped with the identification of driver oncogenes and tumor suppressor genes (TSGs). More recently, the usage of single nucleotide polymorphism arrays provided information of copy number neutral loss of heterozygosity, thus suggesting the occurrence of somatic uniparental disomy (UPD) and uniparental polysomy (UPP) events. The aim of this study is to establish an integrative profiling of recurrent UPDs/UPPs and CNAs in sporadic CRC. Our results indicate that regions showing high frequencies of UPD/UPP mostly coincide with regions typically involved in genomic losses. Among them, chromosome arms 3p, 5q, 9q, 10q, 14q, 17p, 17q, 20p, 21q and 22q preferentially showed UPDs/UPPs over genomic losses suggesting that tumor cells must maintain the disomic state of certain genes to favor cellular fitness. A meta-analysis using over 300 samples from The Cancer Genome Atlas confirmed our findings. Several regions affected by recurrent UPDs/UPPs contain well-known TSGs, as well as novel candidates such as ARID1A, DLC1, TCF7L2 and DMBT1. In addition, VCAN, FLT4, SFRP1 and GAS7 were also frequently involved in regions of UPD/UPP and displayed high levels of methylation. Finally, sequencing and fluorescence in situ hybridization analysis of the gene APC underlined that a somatic UPD event might represent the second hit to achieve biallelic inactivation of this TSG in colorectal tumors. In summary, our data define a profile of somatic UPDs/UPPs in sporadic CRC and highlights the importance of these events as a mechanism to achieve the inactivation of TSGs.

Su Y, Lin L, Zhang J, et al.
Low expression of DLC1 is predictive of poor therapeutic efficiency of fluoropyrimidine and oxaliplatin as adjuvant chemotherapy in gastric cancer.
Mol Med Rep. 2015; 12(4):5771-9 [PubMed] Free Access to Full Article Related Publications
The Rho‑GTPase‑activating protein, deleted in liver cancer‑1 (DLC1), has been reported to be a tumor suppressor. However, the prognostic value of DLC1 in gastric cancer (GC) remains to be fully elucidated. Fluoropyrimidine‑oxaliplatin (FP‑LOHP) combination therapy has been widely used for the adjuvant chemotherapy of GC, however, no reliable marker has been identified to determine its efficiency. Thus, the present study performed a retrospective investigation involving 251 patients with stage IB‑III GC, who received adjuvant chemotherapy following radical resection and 37 patients with stage IV GC, who underwent palliative resection. The expression of DLC1 was found to be reduced in the majority of GC samples (212/288 pairs of samples), compared with normal mucosa, in immunohistochemical analyses. Lower expression levels of DLC1 indicated a more advanced tumor‑node‑metastasis stage, increased lymph node metastasis, deeper tumor invasion, increased tumor size and a higher rate of distant metastasis. By contrast, relatively increased expression levels of DLC1 indicated a longer time to recurrence (TTR) [hazard ratio (HR), 2.232; P=0.004] and overall survival (OS) rate (HR, 2.910; P=0.001). Patients receiving FP‑LOHP adjuvant chemotherapy were significantly less likely to suffer GC recurrence (P=0.001) and succumb to mortality (P=0.004), compared with those who received alternative chemotherapies. However, only the patients with DLC1‑positive GC receiving FP‑LOHP [DLC1 (+)/FP‑LOHP (+)] exhibited a more favorable TTR and OS, compared with the patients with DLC1 (+)/FP‑LOHP (‑) (TTR, P=0.001; OS, P=0.020). No significant improvement in clinical outcome was observed in GC patients with low DLC1 receiving FP‑LOHP treatment (TTR, P=0.270; OS, P=0.197). In conclusion, low expression of DLC1 correlated with GC progression and is predictive of higher rates of recurrence and mortality. Only patients with DLC1‑positive GC may have an improved treatment outcome from the use of FP‑LOHP as adjuvant chemotherapy.

Zhang GJ, Li JS, Zhou H, et al.
MicroRNA-106b promotes colorectal cancer cell migration and invasion by directly targeting DLC1.
J Exp Clin Cancer Res. 2015; 34:73 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Growing evidence suggests that microRNAs (miRNAs) play an important role in tumor development, progression and metastasis. Aberrant miR-106b expression has been reported in several cancers. However, the role and underlying mechanism of miR-106 in colorectal cancer (CRC) have not been addressed.
METHODS: Quantitative RT-PCR(qRT-PCR) was performed to evaluate miR-106b levels in CRC cell lines and patient specimens. Cell proliferation was detected using MTT assay, and cell migration and invasion ability were evaluated by wound healing assay and transwell assay. The target gene of miR-106b was determined by qRT-PCR, western blot and luciferase assays.
RESULTS: miR-106b was significantly up-regulated in metastatic CRC tissues and cell lines, and high miR-106b expression was associated with lymph node metastasis and advanced clinical stage. In addition, miR-106b overexpression enhances, whereas miR-106b depletion reduces CRC cell migration and invasion. Moreover, we identify DLC1 as a direct target of miR-106b, reveal its expression to be inversely correlated with miR-106b in CRC samples and show that its re-introduction reverses miR-106b-induced CRC cell migration and invasion. Furthermore, survival analyses showed the patients with high mi-106b/low DLC1 had shorter overall survival (OS) and disease-free survival (DFS) rates, and confirmed miR-106b may be an independent prognostic factor for OS and DFS in CRC patients.
CONCLUSIONS: Our findings indicate that miR-106b promotes CRC cell migration and invasion by targeting DLC1. This miRNA may serve as a potential prognostic biomarker and therapeutic target for CRC.

Robles AI, Arai E, Mathé EA, et al.
An Integrated Prognostic Classifier for Stage I Lung Adenocarcinoma Based on mRNA, microRNA, and DNA Methylation Biomarkers.
J Thorac Oncol. 2015; 10(7):1037-48 [PubMed] Free Access to Full Article Related Publications
INTRODUCTION: Up to 30% stage I lung cancer patients suffer recurrence within 5 years of curative surgery. We sought to improve existing protein-coding gene and microRNA expression prognostic classifiers by incorporating epigenetic biomarkers.
METHODS: Genome-wide screening of DNA methylation and pyrosequencing analysis of HOXA9 promoter methylation were performed in two independently collected cohorts of stage I lung adenocarcinoma. The prognostic value of HOXA9 promoter methylation alone and in combination with mRNA and miRNA biomarkers was assessed by Cox regression and Kaplan-Meier survival analysis in both cohorts.
RESULTS: Promoters of genes marked by polycomb in embryonic stem cells were methylated de novo in tumors and identified patients with poor prognosis. The HOXA9 locus was methylated de novo in stage I tumors (p < 0.0005). High HOXA9 promoter methylation was associated with worse cancer-specific survival (hazard ratio [HR], 2.6; p = 0.02) and recurrence-free survival (HR, 3.0; p = 0.01), and identified high-risk patients in stratified analysis of stages IA and IB. Four protein-coding gene (XPO1, BRCA1, HIF1α, and DLC1), miR-21 expression, and HOXA9 promoter methylation were each independently associated with outcome (HR, 2.8; p = 0.002; HR, 2.3; p = 0.01; and HR, 2.4; p = 0.005, respectively), and when combined, identified high-risk, therapy naive, stage I patients (HR, 10.2; p = 3 × 10). All associations were confirmed in two independently collected cohorts.
CONCLUSION: A prognostic classifier comprising three types of genomic and epigenomic data may help guide the postoperative management of stage I lung cancer patients at high risk of recurrence.

Xie CR, Sun HG, Sun Y, et al.
Significance of genetic variants in DLC1 and their association with hepatocellular carcinoma.
Mol Med Rep. 2015; 12(3):4203-9 [PubMed] Free Access to Full Article Related Publications
DLC1 has been shown to be downregulated or absent in hepatocellular carcinoma (HCC) and is associated with tumorigenesis and development. However, only a small number of studies have focused on genetic variations of DLC1. The present study performed exon sequencing for the DLC1 gene in HCC tissue samples from 105 patients to identify functional genetic variation of DLC1 and its association with HCC susceptibility, clinicopathological features and prognosis. A novel missense mutation and four non‑synonymous single nucleotide polymorphisms (SNPs; rs3816748, rs11203495, rs3816747 and rs532841) were identified. A significant correlation of rs3816747 polymorphisms with HCC susceptibility was identified. Compared to individuals with the GG genotype of rs3816747, those with the GA (odds ratio (OR)=0.486; P=0.037) or GA+AA genotype (OR=0.51; P=0.039) were associated with a significantly decreased HCC risk. Furthermore, patients with the GC+CC genotype of rs3816748, the TC+CC genotype of rs11203495 or the GA+AA genotype of rs3816747 had small‑sized tumors compared with those carrying the wild‑type genotype. No significant association of DLC1 SNPs with the patients' prognosis was found. These results indicated that genetic variations in the DLC1 gene may confer a risk for HCC.

Braun AC, Olayioye MA
Rho regulation: DLC proteins in space and time.
Cell Signal. 2015; 27(8):1643-51 [PubMed] Related Publications
Rho GTPases function as molecular switches that connect changes of the external environment to intracellular signaling pathways. They are active at various subcellular sites and require fast and tight regulation to fulfill their role as transducers of extracellular stimuli. New imaging technologies visualizing the active states of Rho proteins in living cells elucidated the necessity of precise spatiotemporal activation of the GTPases. The local regulation of Rho proteins is coordinated by the interaction with different guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) that turn on and off GTPase signaling to downstream effectors. GEFs and GAPs thus serve as critical signaling nodes that specify the amplitude and duration of a particular Rho signaling pathway. Despite their importance in Rho regulation, the molecular aspects underlying the spatiotemporal control of the regulators themselves are still largely elusive. In this review we will focus on the Deleted in Liver Cancer (DLC) family of RhoGAP proteins and summarize the evidence gathered over the past years revealing their different subcellular localizations that might account for isoform-specific functions. We will also highlight the importance of their tightly controlled expression in the context of neoplastic transformation.

Huang W, Liu J, Feng X, et al.
DLC-1 induces mitochondrial apoptosis and epithelial mesenchymal transition arrest in nasopharyngeal carcinoma by targeting EGFR/Akt/NF-κB pathway.
Med Oncol. 2015; 32(4):115 [PubMed] Related Publications
Loss of deleted in liver cancer-1 (DLC-1) can induce apoptosis and inhibit the mobility, migration and metastasis in several cancers. Previously, we revealed that ectopic expression of DLC-1 can suppress proliferation, mobility, migration and tumorigenesis in nasopharyngeal carcinoma (NPC). However, the molecular mechanisms accounting for the roles of DLC-1 in NPC are still obscure. In the present work, we attempted to study and uncover the mechanisms underlying the functions of DLC-1 in NPC. The apoptosis of 5-8F-DLC-1 cells, established previously, was analyzed by mitochondrial membrane potentials assay and flow cytometer analysis. And the antibodies involving pathways such as mitochondrial-associated apoptosis, epithelial mesenchymal transition and metastasis were applied to detect and compare the expression level of targeted proteins. The obvious apoptosis of 5-8F-DLC-1 cells was observed reflected by mitochondrial depolarization and lower ratio in cell viability. Subsequently, the activation of mitochondrial apoptosis was verified by the increased expressions of Bax, Apaf1, cleave-caspases and cleave-PARP, etc, and the decreased expressions of Bcl-2, Bcl-xL, Mcl-1, Survivin, etc, in 5-8F-DLC-1 cells. Then, the inhibited epithelial mesenchymal transition of 5-8F-DLC-1 cells was validated by upregulated expression of E-cadherin and downregulated expression of N-cadherin, Snail, Vimentin. Subsequently, downregulated expressions of proteins such as FAK, RhoA, ROCK1 and cdc25 related to cell adhesion and cytoskeleton organization were also observed. And expressions of MMPs were inhibited in 5-8F-DLC-1 cells. At last, the inhibited activity of EGFR/Akt/NF-κB axis was revealed by the decreased expressions of phosho-EGFR, phosho-Akt, phosho-p38MAPK, phosho-IKKα and phosho-p65. Here, we systematically explored the mechanisms underlying the negative roles of DLC-1 in NPC cells. For the first time, we confirmed that the ectopic expression DLC-1 can induce mitochondrial apoptosis, inhibit EMT and related processes by targeting the EGFR/Akt/NF-κB pathway, which, beyond all doubt, offered beneficial guidelines for other studies and laid a good foundation for its clinical applications ultimately.

Ma L, Zhu WZ, Liu TT, et al.
H2O2 inhibits proliferation and mediates suppression of migration via DLC1/RhoA signaling in cancer cells.
Asian Pac J Cancer Prev. 2015; 16(4):1637-42 [PubMed] Related Publications
BACKGROUND: RhoGTPase-activating proteins (RhoGAPs) regulate RhoGTPases in cells, but whether individual reactive oxygen species (ROS) regulate RhoGAPs is unknown. Our previous published papers have shown that deleted in liver cancer 1 (DLC1) inhibits cancer cell migration by its RhoGAP activity. The present study was designed to explore the role of H2O2 in regulation of DLC1.
MATERIALS AND METHODS: We treated cells with H2O2 for 24h and phenotypic changes were analyzed by MTT, RT-PCR, Western blotting, immunofluorescence staining and wound healing assays.
RESULTS: H2O2 downregulated cyclin D1 and cyclin E to inhibit proliferation, and upregulated BAX to induce apoptosis in MCF-7 cells. Compared with non-tumorigenic cells, H2O2 increased expression of DLC1 and reduced activity of RhoA in cancer cells. Stress fiber production and migration were also suppressed by H2O2 in MDA-MB-231 cells.
CONCLUSIONS: Our study suggests that H2O2 inhibits proliferation through modulation of cell cycle and apoptosis-related genes, and inhibits migration by decreasing stress fibers via DLC1/RhoA signaling.

He D, Zhang YW, Zhang NN, et al.
Aberrant gene promoter methylation of p16, FHIT, CRBP1, WWOX, and DLC-1 in Epstein-Barr virus-associated gastric carcinomas.
Med Oncol. 2015; 32(4):92 [PubMed] Related Publications
Alterations in global DNA methylation and specific regulatory gene methylation are frequently found in cancer, but the significance of these epigenetic changes in EBV-associated gastric carcinoma (EBVaGC) remains unclear. We evaluated global DNA methylation status in 49 EBVaGC and 45 EBV-negative gastric carcinoma (EBVnGC) tissue samples and cell lines by 5-methylcytosine immunohistochemical staining and methylation quantification. We determined promoter methylation status and protein expression for the p16, FHIT, CRBP1, WWOX, and DLC-1 genes in tissues and studied the correlation between CpG island methylator phenotype (CIMP) class and clinicopathological characteristics. Changes in gene methylation and mRNA expression in EBVaGC cell line SNU-719 and in EBVnGC cell lines SGC-7901, BGC-823, and AGS were assessed after treatment with 5-aza-2'-deoxycytidine (5-aza-dC), trichostatin A (TSA), or a combination of both, by methylation-specific PCR and quantitative real-time RT-PCR. Global genomic DNA hypomethylation was more pronounced in EBVnGC than in EBVaGC. Promoter methylation of all five genes was more frequent in EBVaGC than in EBVnGC (p < 0.05). p16 and FHIT methylation was reversely correlated with protein expression in EBVaGC. Most (41/49) EBVaGC exhibited CIMP-high (CIMP-H), and the prognosis of CIMP-H patients was significantly worse than that of CIMP-low (p = 0.027) and CIMP-none (p = 0.003) patients. Treatment with 5-aza-dC and/or TSA induced upregulation of RNA expression of all five genes in SNU-719; meanwhile, individual gene expression increased in EBVnGC cell lines. In summary, EBV-induced hypermethylation of p16, FHIT, CRBP1, WWOX, and DLC-1 may contribute to EBVaGC development. Demethylation therapy may represent a novel therapeutic strategy for EBVaGC.

Fu H, Shen J, Wu D
[Hypermethylation of CpG island of DLC-1 gene and arsenic trioxide-induced DLC-1 gene demethylation in multiple myeloma].
Zhonghua Yi Xue Za Zhi. 2014; 94(36):2816-21 [PubMed] Related Publications
OBJECTIVE: To explore the role of hypemethylation of DLC-1 gene in the pathogenesis of multiple myeloma (MM) and examine the effects of arsenic trioxide (As(2)O(3))-induced demethylation of DLC-1 gene in U266 cell line.
METHODS: The methylation status of DLC-1 gene was detected by methylation specific PCR (MSP) in MM patients from 2008 to 2012. And the expression of DLC-1 gene mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR). Methylation statuses of DLC-1 gene exposed to As(2)O(3) were detected by bisulfite sequencing PCR (BSP). And the mRNA expressions of DLC-1 and DNA methyltransferase (DNMT1, T3a and 3b) were determined by real-time fluorescence quantitative PCR (RTFQ-PCR).
RESULTS: Hypermethylation of CpG island of DLC-1 gene was observed in 37/52 (71.15%) MM patients. DLC-1 gene was not expressed after methylation. As(2)O(3) could induce DLC-1 gene demethylation. After 72-houe treatments of 0.5, 1.0 and 2.0 µmol/L As(2)O(3), the methylation rate of DLC-1 gene dropped from 95.38% to 63.07%, 30.00% and 7.69%. As compared with the untreated group, the expression of DLC-1 gene mRNA increased to (1.60 ± 0.09), (3.66 ± 0.17) and (5.29 ± 0.15) folds after exposures (all P < 0.05) . And As(2)O(3) could induce the expression of DNMT1, DNMT3a, DNMT3b gene mRNA (all P < 0.05).
CONCLUSIONS: Methylation of DLC-1 gene is essential in the pathogenesis of MM and may provide a new diagnostic technique and drug target for the treatment of MM. And As(2)O(3) may activate the expression of DLC-1 gene through demethylation.

Busso-Lopes AF, Marchi FA, Kuasne H, et al.
Genomic profiling of human penile carcinoma predicts worse prognosis and survival.
Cancer Prev Res (Phila). 2015; 8(2):149-56 [PubMed] Related Publications
The molecular mechanisms underlying penile carcinoma are still poorly understood, and the detection of genetic markers would be of great benefit for these patients. In this study, we assessed the genomic profile aiming at identifying potential prognostic biomarkers in penile carcinoma. Globally, 46 penile carcinoma samples were considered to evaluate DNA copy-number alterations via array comparative genomic hybridization (aCGH) combined with human papillomavirus (HPV) genotyping. Specific genes were investigated by using qPCR, FISH, and RT-qPCR. Genomic alterations mapped at 3p and 8p were related to worse prognostic features, including advanced T and clinical stage, recurrence and death from the disease. Losses of 3p21.1-p14.3 and gains of 3q25.31-q29 were associated with reduced cancer-specific and disease-free survival. Genomic alterations detected for chromosome 3 (LAMP3, PPARG, TNFSF10 genes) and 8 (DLC1) were evaluated by qPCR. DLC1 and PPARG losses were associated with poor prognosis characteristics. Losses of DLC1 were an independent risk factor for recurrence on multivariate analysis. The gene-expression analysis showed downexpression of DLC1 and PPARG and overexpression of LAMP3 and TNFSF10 genes. Chromosome Y losses and MYC gene (8q24) gains were confirmed by FISH. HPV infection was detected in 34.8% of the samples, and 19 differential genomic regions were obtained related to viral status. At first time, we described recurrent copy-number alterations and its potential prognostic value in penile carcinomas. We also showed a specific genomic profile according to HPV infection, supporting the hypothesis that penile tumors present distinct etiologies according to virus status.

Kaushik S, Ravi A, Hameed FM, Low BC
Concerted modulation of paxillin dynamics at focal adhesions by Deleted in Liver Cancer-1 and focal adhesion kinase during early cell spreading.
Cytoskeleton (Hoboken). 2014; 71(12):677-94 [PubMed] Related Publications
Deleted in Liver Cancer-1 (DLC1) is a RhoGTPase-activating protein (GAP) and a tumor suppressor often downregulated in cancers. It is localized to the focal adhesions (FAs) and its absence leads to enhanced cell migration, invasion, and metastasis. Although DLC1 interacts with focal adhesion kinase (FAK), talin, and tensin, its role in focal adhesions dynamics remains unclear. We examined the effect of DLC1 in Human Foreskin Fibroblasts and determined its localization, dynamics and impact on paxillin by Fluorescence Recovery After Photobleaching at both nascent and mature focal adhesions. During early cell spreading, DLC1 is preferentially localized at the inner/mature adhesions whereas phosphorylated paxillin occupies the outer/nascent FAs. In addition, DLC1 downregulates paxillin turnover in a process, that does not require its GAP activity. Instead, it requires the presence of FAK. Acting in concert, both DLC1 and FAK could provide a unique spatio-temporal mechanism to regulate paxillin function in tissue homeostasis.

Dai X, Li L, Liu X, et al.
Cooperation of DLC1 and CDK6 affects breast cancer clinical outcome.
G3 (Bethesda). 2014; 5(1):81-91 [PubMed] Free Access to Full Article Related Publications
Low DLC1 expression is found to frequently co-occur with aberrant expression of cell cycle genes including CDK6 in human lung and colon cancer. Here, we explore the influence of the synergistic effect of DLC1 and CDK6 on human breast cancer survival at the genetic, transcriptional, and translational levels. We found that high DLC1 and low CDK6 expression are associated with good prognosis. The DLC1 intronic SNP rs561681 is found to fit a recessive model, complying with the tumor suppressive role of DLC1. The heterozygote of the DLC1 SNP is found to increase the hazard when the CDK6 intronic SNP rs3731343 is rare homozygous, and it becomes protective when rs3731343 is common homozygous. We propose that DLC1 expression is the lowest in patients harboring the rare homozygote of rs561681 and functional DLC1 is the lowest when rs561681 is heterozygous and rs3731343 is rare homozygous. We are the first to report such synergistic effects of DLC1 and CDK6 on breast cancer survival at the transcriptional level, the overdominant model fitted by the SNP pair, and the dominant negative effect at the translational level. These findings link the germline genetic polymorphisms and synergistic effect of DLC1 and CDK6 with breast cancer progression, which provide the basis for experimentally elucidating the mechanisms driving differential tumor progression and avail in tailoring the clinical treatments for such patients based on their genetic susceptibility.

Fang QL, Yin YR, Xie CR, et al.
Mechanistic and biological significance of DNA methyltransferase 1 upregulated by growth factors in human hepatocellular carcinoma.
Int J Oncol. 2015; 46(2):782-90 [PubMed] Related Publications
Dysregulation of growth factor signaling plays a pivotal role in controlling the malignancy phenotype and progression of hepatocellular carcinoma (HCC). However, the precise oncogenic mechanisms underlying transcription regulation of certain tumor suppressor genes (TSGs) by growth factors are poorly understood. In the present study, we report a novel insulin-like growth factor 1 (IGF1) pathway that mediates de novo DNA methylation and TSG (such as DLC1 and CHD5) silencing by upregulation of the DNA methyltransferase 1 (DNMT1) via an AKT/β-transducin repeat-containing protein (βTrCP)-mediated ubiquitin-proteasome pathway in HCC. Analysis of DNA methylation in CpG islands of target genes revealed high co-localization of DNMT1 and DNMT3B on the promoters of TSGs associated with enhanced CpG hypermethylation. Our results point to a novel epigenetic mechanism for growth factor-mediated repression of TSG transcription that involves DNA methylation.

Zubor P, Hatok J, Moricova P, et al.
Gene expression profiling of histologically normal breast tissue in females with human epidermal growth factor receptor 2‑positive breast cancer.
Mol Med Rep. 2015; 11(2):1421-7 [PubMed] Related Publications
Gene expression profile‑based taxonomy of breast cancer (BC) has been described as a significant breakthrough in comprehending the differences in the origin and behavior of cancer to allow individually tailored therapeutic approaches. In line with this, we hypothesized that the gene expression profile of histologically normal epithelium (HNEpi) could harbor certain genetic abnormalities predisposing breast tissue cells to develop human epidermal growth factor receptor 2 (HER2)‑positive BC. Thus, the aim of the present study was to assess gene expression in normal and BC tissue (BCTis) from patients with BC in order to establish its value as a potential diagnostic marker for cancer development. An array study evaluating a panel of 84 pathway‑ and disease‑specific genes in HER2‑positive BC and tumor‑adjacent HNEpi was performed using quantitative polymerase chain reaction in 12 patients using microdissected samples from frozen tissue. Common prognostic and predictive parameters of BC were assessed by immunohistochemistry and in situ hybridization. In the BCTis and HNEpi samples of 12 HER2‑positive subjects with BC, the expression of 2,016 genes was assessed. A total of 39.3% of genes were deregulated at a minimal two‑fold deregulation rate and 10.7% at a five‑fold deregulation rate in samples of HNEpi or BCTis. Significant differences in gene expression between BCTis and HNEpi samples were revealed for BCL2L2, CD44, CTSD, EGFR, ERBB2, ITGA6, NGFB, RPL27, SCBG2A1 and SCGB1D2 genes (P<0.05), as well as GSN, KIT, KLK5, SERPINB5 and STC2 genes (P<0.01). Insignificant differences (P<0.07) were observed for CCNA1, CLU, DLC1, GABRP and IL6 genes. The ontological gene analyses revealed that the majority of the deregulated genes in the HNEpi samples were part of the functional gene group directly associated with BC origin and prognosis. Functional analysis showed that the most frequent gene deregulations occurred in genes associated with apoptosis and cell cycle regulation in BCTis samples, and with angiogenesis, regulation of the cell cycle and transcriptional activity in HNEpi samples. The molecular profiling of HNEpi breast tissue revealed gene expression abnormalities that may represent potential markers of increased risk for HER2‑positive malignant transformation of breast tissue, and may be able to be employed as predictors of prognosis.

Okayama H, Schetter AJ, Ishigame T, et al.
The expression of four genes as a prognostic classifier for stage I lung adenocarcinoma in 12 independent cohorts.
Cancer Epidemiol Biomarkers Prev. 2014; 23(12):2884-94 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: We previously developed a prognostic classifier using the expression levels of BRCA1, HIF1A, DLC1, and XPO1 that identified stage I lung adenocarcinoma patients with a high risk of relapse. That study evaluated patients in five independent cohorts from various regions of the world. In an attempt to further validate the classifier, we have used a meta-analysis-based approach to study 12 cohorts consisting of 1,069 tumor-node-metastasis stage I lung adenocarcinoma patients from every suitable, publically available dataset.
METHODS: Cohorts were obtained through a systematic search of public gene expression datasets. These data were used to calculate the risk score using the previously published 4-gene risk model. A fixed effect meta-analysis model was used to generate a pooled estimate for all cohorts.
RESULTS: The classifier was associated with prognosis in 10 of the 12 cohorts (P < 0.05). This association was highly consistent regardless of the ethnic diversity or microarray platform. The pooled estimate demonstrated that patients classified as high risk had worse overall survival for all stage I [HR, 2.66; 95% confidence interval (CI), 1.93-3.67; P < 0.0001] patients and in stratified analyses of stage IA (HR, 2.69; 95% CI, 1.66-4.35; P < 0.0001) and stage IB (HR, 2.69; 95% CI, 1.74-4.16; P < 0.0001) patients.
CONCLUSIONS: The 4-gene classifier provides independent prognostic stratification of stage IA and stage IB patients beyond conventional clinical factors.
IMPACT: Our results suggest that the 4-gene classifier may assist clinicians in decisions about the postoperative management of early-stage lung adenocarcinoma patients.

Guo J, Feng XQ, Nie SM, et al.
Effect of 5-aza-2'-deoxycytidine combined with trichostatin A on RPMI-8226 cell proliferation, apoptosis and DLC-1 gene expression.
Zhongguo Shi Yan Xue Ye Xue Za Zhi. 2014; 22(2):357-63 [PubMed] Related Publications
This study was aimed to investigate the effects of the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-Aza-CdR) and histone deacetylase inhibitor trichostatin A (TSA) on DLC-1 gene transcription regulation and molecular biological behaviours in the human multiple myeloma RPMI-8226 cells. The cells were treated respectively with 5-Aza-CdR and TSA alone, or the both combination; the cell proliferation and apoptosis, DLC-1 expression, the protein expression of Ras homolog family member A (RhoA) and Ras-related C3 botulinum toxin substrate 1 (Rac1) were examined by CCK-8 method, RT-PCR and ELISA, respectively. The results showed that the 5-Aza-CdR and TSA had cell growth inhibitory and apoptosis-inducing effects in dose-dependent manner (P < 0.05). Compared with a single drug (5-Aza-CdR or TSA alone), the effects were significantly enhanced after treatment with the combination of 5-Aza-CdR and TSA (P < 0.05). DLC-1 was weakly expressed in the control group; the treatment with 5-Aza-CdR alone enhanced its re-expression dose-dependently (P < 0.05). Compared with 5-Aza-CdR alone, 5-Aza-CdR plus TSA enhanced DLC-1 re-expression significantly.Compared with the control, 5-Aza-CdR and TSA significantly decreased RhoA and Rac1 protein expression (P < 0.05). It is concluded that 5-Aza-CdR and TSA can effectively reverse DLC-1 expression of RPMI-8226 cells; TSA has a synergistic effect on its re-expression. 5-Aza-CdR and TSA have significant cell growth inhibitory and apoptosis-inducing effects on RPMI-8226 cells. These effects may be related to the inhibition of Rho/Rho kinase signalling pathway.

Ali Hassan NZ, Mokhtar NM, Kok Sin T, et al.
Integrated analysis of copy number variation and genome-wide expression profiling in colorectal cancer tissues.
PLoS One. 2014; 9(4):e92553 [PubMed] Free Access to Full Article Related Publications
Integrative analyses of multiple genomic datasets for selected samples can provide better insight into the overall data and can enhance our knowledge of cancer. The objective of this study was to elucidate the association between copy number variation (CNV) and gene expression in colorectal cancer (CRC) samples and their corresponding non-cancerous tissues. Sixty-four paired CRC samples from the same patients were subjected to CNV profiling using the Illumina HumanOmni1-Quad assay, and validation was performed using multiplex ligation probe amplification method. Genome-wide expression profiling was performed on 15 paired samples from the same group of patients using the Affymetrix Human Gene 1.0 ST array. Significant genes obtained from both array results were then overlapped. To identify molecular pathways, the data were mapped to the KEGG database. Whole genome CNV analysis that compared primary tumor and non-cancerous epithelium revealed gains in 1638 genes and losses in 36 genes. Significant gains were mostly found in chromosome 20 at position 20q12 with a frequency of 45.31% in tumor samples. Examples of genes that were associated at this cytoband were PTPRT, EMILIN3 and CHD6. The highest number of losses was detected at chromosome 8, position 8p23.2 with 17.19% occurrence in all tumor samples. Among the genes found at this cytoband were CSMD1 and DLC1. Genome-wide expression profiling showed 709 genes to be up-regulated and 699 genes to be down-regulated in CRC compared to non-cancerous samples. Integration of these two datasets identified 56 overlapping genes, which were located in chromosomes 8, 20 and 22. MLPA confirmed that the CRC samples had the highest gains in chromosome 20 compared to the reference samples. Interpretation of the CNV data in the context of the transcriptome via integrative analyses may provide more in-depth knowledge of the genomic landscape of CRC.

Wang C, Wang J, Liu H, Fu Z
Tumor suppressor DLC-1 induces apoptosis and inhibits the growth and invasion of colon cancer cells through the Wnt/β-catenin signaling pathway.
Oncol Rep. 2014; 31(5):2270-8 [PubMed] Related Publications
The aim of the present study was to investigate the biological role and molecular mechanism of the deleted in liver cancer-1 (DLC-1) gene in human colon cancer growth and invasion. Recombinant lentiviral vectors encoding the DLC-1 gene were constructed for transfection into the human colon cancer cell line SW480. Real-time quantitative polymerase chain reaction (real-time qPCR) and western blot analysis were employed to evaluate the expression of DLC-1, β-catenin, GSK-3β and c-myc in DLC-1-transfected cells. Moreover, cell proliferation assay, cell colony formation assay, cell cycle analysis, apoptosis analysis and cell migration and invasion assays were performed in order to elucidate the role of DLC-1 in colorectal cancer development and progression. Both real-time qPCR and western blot analyses showed that the DLC-1 gene and protein were overexpressed in the DLC-1-transfected SW480 cells. In addition, the expression of β-catenin and GSK-3β was upregulated and the expression of the c-myc gene was downregulated in the DLC-1-transfected SW480 cells. Furthermore, DLC-1 overexpression inhibited cell proliferation, colony formation, migration and invasion, and induced cell cycle arrest at the G1 phase with subsequent apoptosis. DLC-1 inhibits cell growth and invasion in human colon cancer, functioning as a tumor-suppressor gene, possibly through the regulation of the Wnt/β-catenin signaling pathway.

Wang Y, Lei R, Zhuang X, et al.
DLC1-dependent parathyroid hormone-like hormone inhibition suppresses breast cancer bone metastasis.
J Clin Invest. 2014; 124(4):1646-59 [PubMed] Free Access to Full Article Related Publications
Bone metastasis is a frequent complication of breast cancer that is often accelerated by TGF-β signaling; however, little is known about how the TGF-β pathway is regulated during bone metastasis. Here we report that deleted in liver cancer 1 (DLC1) is an important regulator of TGF-β responses and osteolytic metastasis of breast cancer cells. In murine models, breast cancer cells lacking DLC1 expression exhibited enhanced capabilities of bone metastasis. Knockdown of DLC1 in cancer cells promoted bone metastasis, leading to manifested osteolysis and accelerated death in mice, while DLC1 overexpression suppressed bone metastasis. Activation of Rho-ROCK signaling in the absence of DLC1 mediated SMAD3 linker region phosphorylation and TGF-β-induced expression of parathyroid hormone-like hormone (PTHLH), leading to osteoclast maturation for osteolytic colonization. Furthermore, pharmacological inhibition of Rho-ROCK effectively reduced PTHLH production and breast cancer bone metastasis in vitro and in vivo. Evaluation of clinical breast tumor samples revealed that reduced DLC1 expression was linked to elevated PTHLH expression and organ-specific metastasis to bone. Overall, our findings define a stroma-dependent paradigm of Rho signaling in cancer and implicate Rho-TGF-β crosstalk in osteolytic bone metastasis.

García-Baquero R, Puerta P, Beltran M, et al.
Methylation of tumor suppressor genes in a novel panel predicts clinical outcome in paraffin-embedded bladder tumors.
Tumour Biol. 2014; 35(6):5777-86 [PubMed] Related Publications
DNA methylation of tumor suppressor genes (TSGs) represents a frequent and early epigenetic event with potential applications for cancer detection and disease evolution. Our aim was to examine the stratification and prognostic biomarker role of the methylation of a novel panel of TSGs in bladder cancer. The methylation status of 18 TSGs was evaluated in bladder cancer cells (n=14) and paraffin-embedded primary bladder tumors (n=61), using a methylation-specific multiplex ligation-dependent probe amplification assay (MS-MLPA). Recurrence, progression, and disease-specific survival were analyzed using univariate and multivariate Cox models. PRDM2, HLTF, ID4, DLC1, BNIP3, H2AFX, CACNA1G, TGIF, and CACNA1A were discovered methylated in bladder cancer. The methylation of RUNX3 (p=0.026), TWIST1 (p=0.009), SFRP4 (p=0.002), and CCND2 (p=0.027) correlated to tumor stage. Univariate analyses indicated prognostic associations for recurrence (DLC1, SFRP5, H2AFX, CACNA1G), progression (DLC1, SFRP5, CACNA1G), disease-specific (PRDM2, DLC1, SFRP5, CACNA1G, and TIMP3), and overall survival (SFRP5 and TIMP3). In multivariate analyses, several TSGs remained as independent prognosticators for recurrence (SFRP5, H2AFX), progression (CACNA1G), and disease-specific survival (SFRP5). Thus, a novel set of TSGs was identified, frequently methylated in bladder cancer cells and tumors. TSG methylation allowed histopathologic and outcome stratification using paraffin-embedded tumors. This is clinically relevant by offering a strategy for the management of patients affected with uroepithelial neoplasias in pathology routine laboratories.

Sjoestroem C, Khosravi S, Cheng Y, et al.
DLC1 expression is reduced in human cutaneous melanoma and correlates with patient survival.
Mod Pathol. 2014; 27(9):1203-11 [PubMed] Related Publications
Deleted in Liver Cancer-1 (DLC1) is a Rho-GTPase-activating protein known to be downregulated and function as a tumor suppressor in numerous solid and hematological cancers. Its expression status in melanoma is currently unknown however, prompting us to examine this. Using immunohistochemistry and tissue microarrays containing a large set of melanocytic lesions (n=539), we examined the expression profile of DLC1 in melanoma progression, as well as the association between DLC1 and patient survival. We detected both cytoplasmic and nuclear DLC1 expression, and found that whereas cytoplasmic DLC1 was significantly downregulated in metastatic melanoma compared with nevi and primary melanoma, nuclear DLC1 expression was significantly down in primary melanoma compared with nevi, and then further down in metastatic melanoma. Loss of cytoplasmic DLC1 was significantly associated with poorer overall and disease-specific 5-year survival rates of all melanoma (P<0.001 and P=0.001, respectively) and metastatic melanoma patients (P=0.020 and 0.008, respectively), and similar results were seen for nuclear DLC1 (P<0.001 for both overall and disease-specific survival for all melanoma patients, and P=0.004 for metastatic melanoma patients). Next, we examined the correlation between cytoplasmic and nuclear DLC1 and found that concomitant loss of both forms was associated with the worst outcome for metastatic melanoma patients (P=0.013 and P=0.008 for overall and disease-specific 5-year survival, respectively). Finally, multivariate Cox regression analysis determined that strong cytoplasmic and nuclear DLC1 expression was a favorable independent prognostic factor for all melanoma (HR, 0.61; 95% CI, 0.42-0.88; P=0.008) and metastatic melanoma patients (HR, 0.42; 95% CI, 0.23-0.77; P=0.005). Although more research still needs to be done on the topic, these preliminary results support the hypothesis that DLC1 is a tumor suppressor in melanoma.

Further References

Yuan BZ, Durkin ME, Popescu NC
Promoter hypermethylation of DLC-1, a candidate tumor suppressor gene, in several common human cancers.
Cancer Genet Cytogenet. 2003; 140(2):113-7 [PubMed] Related Publications
Aberrant methylation of CpG islands within the promoter regions of tumor suppressor or cancer-related genes is a common mechanism leading to the silencing of gene expression. To determine whether aberrant methylation is a contributing factor to transcriptional inactivation of DLC-1 (deleted in liver cancer-1), a candidate tumor suppressor gene, we examined its methylation status in twelve hepatocellular carcinoma. breast, colon, and prostate tumor cell lines with low or undetectable expression of DLC-1. By Southern blot analysis of DNA digested with the methylation sensitive enzyme HpaII, we found a different degree of promoter hypermethylation in all cell lines with aberrant DLC-1 expression. The hypermethylation status was reversed by the addition of 5-aza-2'-deoxycytidine, a demethylating agent, in one human hepatocellular carcinoma line. These observations suggest that hypermethylation is responsible for abrogating the function of the DLC-1 gene in a subset of liver, breast, colon, and prostate cancers.

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