Deleted In Colorectal Cancer Gene Research Articles

Axon guidance pathway genes are associated with schizophrenia risk.

In the present study, we analyzed schizophrenia (SCZ)-related genome-wide association studies (GWAS) to identify genes and pathways associated with SCZ. We identified 1,098 common genes (1,098/9,468) and 20 shared KEGG pathways (both P<0.01) by integrating candidate genes from the European and American SCZ-related GWAS. The pathways related to axon guidance, long term potentiation and arrhythmogenic right ventricular cardiomyopathy (ARVC) were highly significant (P<10−3). Moreover, 15 axon guidance pathway-related genes were associated with SCZ. The association between axon guidance pathway genes and SCZ was validated by a two-stage case-control study on Shandong migrants in northeastern China. Moreover, individuals with the rs9944880 TT polymorphism in the deleted in colorectal cancer (DCC) gene were associated with SCZ. These findings indicate that the axon guidance pathway genes and the rs9944880 SNP in DCC gene are associated with SCZ pathogenesis.

Deleted in Colorectal Cancer (DCC) gene polymorphism is associated with H. pylori infection among susceptible Malays from the north-eastern region of Peninsular Malaysia.

Using genome-wide case-control association approach, the current study aimed to determine whether genetic polymorphism(s) is/are associated with H. pylori infection among ethnic Malays from the north-eastern region of Peninsular Malaysia, a region with an exceptionally low prevalence for H. pylori infection and gastric cancer. Twenty-three Malay subjects positive for H. pylori confirmed with urease test and histology were enrolled as "cases" and 37 subjects negative for H. pylori were "controls". Both groups were matched for age and environmental risks. Extracted DNA samples (QIAGEN, Germany) from the venous blood of study subjects were genotyped using the Human Mapping 50k xbal array (Affymetrix, USA). High throughput downstream analyses were then used to determine the significant SNP(s) associated with H. pylori infection. Out of 20,361 SNPs filtered using the genotype association test, the top 1% (203) significant SNPs were selected for functional enrichment analysis. Of the 15 "enriched" SNPs, the rs10502974 which was located within the intronic region of Deleted in Colorectal Cancer (DCC) gene was the SNP most significantly associated with H. pylori infection (p=0.00549). Ethnic Malays is genetically susceptible to H. pylori infection and is possibly mediated through a genetic variation in the DCC gene.

Trophic factors differentiate dopamine neurons vulnerable to Parkinson's disease

Recent studies suggest a variety of factors characterize substantia nigra neurons vulnerable to Parkinson's disease, including the transcription factors pituitary homeobox 3 (Pitx3) and orthodenticle homeobox 2 (Otx2) and the trophic factor receptor deleted in colorectal cancer (DCC), but there is limited information on their expression and localization in adult humans. Pitx3, Otx2, and DCC were immunohistochemically localized in the upper brainstem of adult humans and mice and protein expression assessed using relative intensity measures and online microarray data. Pitx3 was present and highly expressed in most dopamine neurons. Surprisingly, in our elderly subjects no Otx2 immunoreactivity was detected in dopamine neurons, although Otx2 gene expression was found in younger cases. Enhanced DCC gene expression occurred in the substantia nigra, and higher amounts of DCC protein characterized vulnerable ventral nigral dopamine neurons. Our data show that, at the age when Parkinson's disease typically occurs, there are no significant differences in the expression of transcription factors in brainstem dopamine neurons, but those most vulnerable to Parkinson's disease rely more on the trophic factor receptor DCC than other brainstem dopamine neurons.

Association between schizophrenia and genetic variation in DCC: A case–control study

Schizophrenia is a highly heritable neurodevelopmental disorder associated with alterations in synaptic connectivity. Deleted in colorectal cancer (DCC), a receptor for the guidance cue netrin-1, plays a pivotal role in organizing neuronal circuitry by guiding growing axons and dendrites to their correct targets and by influencing synaptic connectivity. Results from experiments we previously conducted in dcc-heterozygous mice show that DCC plays a critical role in the developmental organization of the mesocorticolimbic dopamine (DA) circuitry. Furthermore we have shown that reduced expression of DCC during development and/or throughout life confers resilience to the development of schizophrenia-like DA and behavioural abnormalities. Importantly, this “protective” phenotype only emerges after puberty. Here we assess whether DCC may contribute to the risk of schizophrenia. We examined single nucleotide polymorphisms (SNPs) located in the DCC gene for association with schizophrenia using a case–control sample consisting of 556 unrelated schizophrenic patients and 208 healthy controls. We found one SNP, rs2270954, to be nominally associated with schizophrenia; patients were less likely to be heterozygous at this locus and more likely to be homozygous for the minor allele (χ2=9.84, df=2, nominal p=0.0071). Intriguingly, this SNP is located within the 3′ untranslated region, an area known to contain a number of regulatory sequences that determine the stability and translation efficacy of mRNA. These results, together with our previous findings from studies in rodents, point at DCC as a promising novel candidate gene that may contribute to the genetic basis behind individual differences in susceptibility to schizophrenia.

The Dependence Receptor UNC5H2/B Triggers Apoptosis via PP2A-Mediated Dephosphorylation of DAP Kinase

The UNC5H dependence receptors promote apoptosis in the absence of their ligand, netrin-1, and this is important for neuronal and vascular development and for limitation of cancer progression. UNC5H2 (also called UNC5B) triggers cell death through the activation of the serine-threonine protein kinase DAPk. While performing a siRNA screen to identify genes implicated in UNC5H-induced apoptosis, we identified the structural subunit PR65β of the holoenzyme protein phosphatase 2A (PP2A). We show that UNC5H2/B recruits a protein complex that includes PR65β and DAPk and retains PP2A activity. PP2A activity is required for UNC5H2/B-induced apoptosis, since it activates DAPk by triggering its dephosphorylation. Moreover, netrin-1 binding to UNC5H2/B prevents this effect through interaction of the PP2A inhibitor CIP2A to UNC5H2/B. Thus we show here that, in the absence of netrin-1, recruitment of PP2A to UNC5H2/B allows the activation of DAPk via a PP2A-mediated dephosphorylation and that this mechanism is involved in angiogenesis regulation.

Alterations of DCC Gene in B-Cell Malignancies.

Abstract 4428Many genetic alterations have been detected in various tumors to date, and these are concerned with oncogenesis closely. Oligonucleotide array analysis has contributed to detect genomic gains and losses implicated in the development of human malignant tumors, identifying either oncogenes or tumor suppressor genes. In our recent data, oligonucleotide array analysis showed recurrent genomic copy number variations at 18q21-22 in malignant lymphoma and multiple myeloma cell lines. There are a lot of genes related to oncogenesis at 18q21-22, such as SMAD4, DCC, MBD2, TCF4, TXNL1, WDR7, FECH, NARS, MALT1, and BCL2. We studied expression of these genes by reverse-transcriptase polymerase chain reaction (RT-PCR). Although most genes examined expressed in almost all cell lines examined, DCC (deleted in colorectal cancer) could be detected in a small number of malignant lymphoma cell lines.DCC, which encodes a receptor for netrin-1, would control apoptosis and be concerned in oncogenesis. Loss of one DCC allele or decreased DCC expression occur in many solid tumors, suggesting that DCC inactivation constitutes a critical event in the development of these tumors. Similarly, the inactivation of DCC can have a role in the development of hematologic malignancies, including leukemia and malignant lymphoma. We analyzed DCC expression in 15 multiple myeloma and 9 malignant lymphoma cell lines, by RT-PCR using various primer pairs. However, no products could be detected using any primer pairs containing DCC exon 1 primer in three multiple myeloma cell lines, although other primer pairs could amplify products, suggesting the DCC transcripts lacking exon 1 in these cell lines. This result made us predict the abnormal form of DCC. Therefore, we tried to clone the DCC transcripts fused to unknown sequences instead of exon 1, using bubble PCR method for cDNA in these three cell lines. Some products were obtained and sequenceanalysis revealed that the bubble PCR products contained exon 2 of DCC fused to unknown sequences. BLAST search revealed that these unknown sequences were part of intron 1 of DCC, resulting in the lack of start codon in exon 1. Putative abnormal DCC protein lacks a part of N-terminus, suggesting that structural abnormalities of DCC play some roles in oncogenesis of hematologic malignancies. Although the previous studies described the abnormalities of DCC derived from allelic loss or decreased expression, structural abnormalities of DCC we found in this study might be another critical mechanism for DCC abnormalities even if the normal expression could be detected by RT-PCR which could amplify only limited portion of the gene. Disclosures:No relevant conflicts of interest to declare.

Netrin-1 Overexpression Protects Kidney from Ischemia Reperfusion Injury by Suppressing Apoptosis

Netrin-1, a diffusible laminin-related protein, is highly expressed in the kidney. However, the pathophysiological roles of netrin-1 in the kidney are unknown. To address this question directly, we used transgenic mice that overexpress chicken netrin-1 in the kidney. Netrin-1 overexpression was confirmed by real-time RT-PCR and Western blot analysis. Eight-week-old wild-type and transgenic mice were subjected to 26 minutes of renal ischemia followed by reperfusion for 72 hours. Wild-type mice developed more severe renal dysfunction by 24 hours than netrin-1 transgenic mice. Functional improvement was associated with better preservation of morphology, reduced cytokine expression, and reduced oxidative stress in the kidney of transgenic mice as compared with wild-type mice. In addition, both basal and reperfusion-induced cell proliferation were dramatically increased in transgenic kidneys as determined by Ki-67 staining. Interestingly, ischemia reperfusion induced a large increase in apoptosis in wild-type mice but not in netrin-1 transgenic mice that was associated with reduced caspase-3 activation in the transgenic kidney. These results suggest that netrin-1 protects renal tubular epithelial cells against ischemia reperfusion-induced injury by increasing proliferation and suppressing apoptosis.

Inactivation of the UNC5C Netrin-1 Receptor Is Associated With Tumor Progression in Colorectal Malignancies

The UNC5H netrin-1 receptors (UNC5H1-3 also called UNC5A-C) belong to the functional dependence receptors family, which share the ability to induce apoptosis in the absence of their ligands. Such a trait has been hypothesized to confer a tumor-suppressor activity. Indeed, cells harboring these receptors are thought to be dependent on ligand availability for their survival, thereby inhibiting uncontrolled tumor cell proliferation. We investigate here whether UNC5C acts as a tumor suppressor in colorectal malignancies. The level of UNC5C was analyzed in a panel of 86 primary sporadic colorectal carcinomas. Loss of heterozygosity in the UNC5C locus and epigenetic alterations in the UNC5C promoter were also analyzed. Intestinal tumor progression was monitored in mice bearing both UNC5C and APC1638N mutations, and apoptosis was measured in intestinal tumors developed in UNC5C/APC1638N mutant mice. We show here that UNC5C expression is down-regulated in a large fraction of human colorectal cancers, mainly through promoter methylation. Moreover, in mice, inactivation of UNC5C is associated with increased intestinal tumor progression and a decrease in tumor cell apoptosis. The loss of UNC5C expression observed in human colorectal cancer is a selective advantage for tumor progression, in agreement with the dependence receptor hypothesis. Thus, the UNC5C dependence receptor is a tumor suppressor that regulates sporadic colorectal cancer.

DCC is a potential methylation marker in human cancers

15054 Background: DCC (deleted in colorectal cancer) is a tumor suppressor gene, and known to be inactivated by mutation in human cancers. In this study, we revealed DCC gene promoter methylation in primary human esophageal and breast cancers and refer to its excellence as a cancer-prone marker. Methods: Quantititative TaqMan real time polymerase chain reaction; 20 esophageal squamous cell carcinoma (ESCC) and the corresponding non-cancerous esophageal mucosal tissues, 58 breast cancer tissues, and ESCC cell lines. Results: (1) In ESCC tissues, DCC hypermethylation is detected in 18/20 cases (sensitivity=90%), while it is detected in only 2/20 normal cases (specificity=90%). (2) In breast cancer tissues, DCC hypermethylation is detected in 29/58 cases (50%), and patients with higher methylation of DCC showed size larger than 6 cm (100%) as compared with those less than 6 cm (45.3%)(p&lt;0.025). (3) DCC is silenced in cancer cell lines, and found to be reactivated by demethylating agent in several cell lines, while still silenced in other cell lines. Conclusions: In ESCC, DCC hypermethylation could be an excellent potential marker. DCC inactivation is partially explained by methylation, however other mechanism could be involved like p53. The accurate mechanism of DCC requires further elucidation, but its potential as a tumor marker in SCC is considered excellent to apply for cancer detection using human body fluid. No significant financial relationships to disclose.

Netrin-1: when a neuronal guidance cue turns out to be a regulator of tumorigenesis

Netrin-1 has been shown to play a crucial role in neuronal navigation during nervous system development mainly through its interaction with its receptors DCC and UNC5H. However, initially the DCC (deleted in colorectal cancer) gene was proposed as a putative tumor suppressor gene. It was then difficult to reconcile the two activities of DCC until the observation that DCC belongs to an emerging family of receptors named dependence receptors. Such receptors share the property of inducing apoptosis in the absence of ligand, hence creating a cellular state of dependence on the ligand. Thus, netrin-1 may not only be a chemotropic factor for neurons but also a survival factor. We will review here the identification of netrin-1 and its receptors, the signaling pathways initiated in the presence or absence of netrin-1. We will suggest some possible roles of netrin-1 in nervous system development, neovascularisation, adhesion and tumorigenesis.

Role of the dependence receptor DCC in colorectal cancer pathogenesis.

More than a decade ago, the DCC (deleted in colorectal cancer) gene was proposed as a putative tumor suppressor gene. Data supporting this proposal included observations that one DCC allele was deleted in roughly 70% of colorectal cancers, some cancers had somatic mutations of the DCC gene, and DCC expression was often reduced or absent in colorectal cancer tissues and cell lines. Despite subsequent studies which have supported DCC's potential role as a tumor suppressor gene, the rarity of point mutations identified in DCC coding sequences, the lack of a tumor predisposition phenotype in mice heterozygous for DCC inactivating mutations, and the presence of other known and candidate tumor suppressor genes on chromosome 18q have raised questions about DCC's candidacy. Following its initial characterization, the DCC protein was identified as a transmembrane receptor for netrins, key factors in axon guidance in the developing nervous system. At first glance, the established role of DCC and netrin-1 during organization of the spinal cord could be viewed as a further challenge to the position that DCC inactivation might play a significant role in tumorigenesis. However, recent observations on DCC's functions in intracellular signaling have renewed interest in the potential contribution of DCC inactivation to cancer. In particular, data indicate that, when engaged by netrin ligands, DCC may activate downstream signaling pathways. Moreover, in settings where netrin is absent or at low levels, DCC can promote apoptosis. Here, we review DCC's candidacy as a tumor suppressor gene, with an emphasis on how recent molecular analyses of DCC have offered support for the notion that DCC may function as a tumor suppressor gene.

Microsatellite analysis of the DCC gene in nephroblastomas: pathologic correlations and prognostic implications

Microsatellite instability has been reported in a wide variety of cancer types. Inactivation or loss of tumour suppressor genes has been shown to result in cell cycle deregulation and neoplastic growth. We conducted a microsatellite study using fluorescent-based DNA technology to determine whether mutations in the microsatellite sequences of the deleted in colorectal cancer (DCC) gene, a tumour suppressor at 18q21.1, have any pathologic correlation or prognostic significance in nephroblastomas. Normal and tumour DNA was isolated from 106 cases of nephroblastoma using the standard proteinase K digestion and phenol–chloroform extraction method from paraffin wax-embedded tissue. Polymerase chain reaction using three microsatellite markers; D18S21, D18S34 and D18S58, for the DCC gene were performed. The polymerase chain reaction products were analysed on the ALF Express Automated DNA sequencer. The results were correlated with age at diagnosis, preoperative chemotherapy, clinicopathological stage, histological classification and patient outcome using χ2 test. Allelic imbalance/loss of heterozygosity appeared to be a more frequent genetic aberration than microsatellite instability with 20% of cases showing allelic imbalance/loss of heterozygosity and only 9% of cases showing microsatellite instability. Genetic aberrations were more frequent in unfavourable histology tumours compared to favourable histology tumours (P=0.012). All patients with genetic aberrations for more than one DCC marker died independent of histological classification and stage (P=0.016). There was no statistically significant difference when DCC aberrations were compared with age at diagnosis, preoperative chemotherapy and clinicopathological stage. In conclusion, this study has found that multiple aberrations involving the DCC locus may play a role in the progression of nephroblastomas, and hence confer a poorer prognosis

Microsatellite analysis of the DCC gene in nephroblastomas: pathologic correlations and prognostic implications

Microsatellite instability has been reported in a wide variety of cancer types. Inactivation or loss of tumour suppressor genes has been shown to result in cell cycle deregulation and neoplastic growth. We conducted a microsatellite study using fluorescent-based DNA technology to determine whether mutations in the microsatellite sequences of the deleted in colorectal cancer (DCC) gene, a tumour suppressor at 18q21.1, have any pathologic correlation or prognostic significance in nephroblastomas. Normal and tumour DNA was isolated from 106 cases of nephroblastoma using the standard proteinase K digestion and phenol–chloroform extraction method from paraffin wax-embedded tissue. Polymerase chain reaction using three microsatellite markers; D18S21, D18S34 and D18S58, for the DCC gene were performed. The polymerase chain reaction products were analysed on the ALF Express Automated DNA sequencer. The results were correlated with age at diagnosis, preoperative chemotherapy, clinicopathological stage, histological classification and patient outcome using χ2 test. Allelic imbalance/loss of heterozygosity appeared to be a more frequent genetic aberration than microsatellite instability with 20% of cases showing allelic imbalance/loss of heterozygosity and only 9% of cases showing microsatellite instability. Genetic aberrations were more frequent in unfavourable histology tumours compared to favourable histology tumours (P=0.012). All patients with genetic aberrations for more than one DCC marker died independent of histological classification and stage (P=0.016). There was no statistically significant difference when DCC aberrations were compared with age at diagnosis, preoperative chemotherapy and clinicopathological stage. In conclusion, this study has found that multiple aberrations involving the DCC locus may play a role in the progression of nephroblastomas, and hence confer a poorer prognosis

Tumor suppressor function of Betaig-H3 gene in radiation carcinogenesis

Interaction between cell and extracellular matrix (ECM) plays a crucial role in tumor invasiveness and metastasis. Using an immortalized human bronchial epithelial (BEP2D) cell model, we showed previously that expression of a list of genes including Betaig-h3 (induced by transforming growth factor-β) DCC (deleted in colorectal cancer), p21 cip1, c-fos , Heat shock protein (HSP27) and cytokeratin 14 were differentially expressed in several independently generated, radiation-induced tumor cell lines (TL1-TL5) relative to parental BEP2D cells. Our previous data further demonstrated that loss of tumor suppressor gene(s) as a likely mechanism of radiation carcinogenesis. In the present study, we chose Betaig-h3 and DCC that were downregulated in tumorigenic cells for further study. Restored expression of Betaig-h3 gene, not DCC gene, by transfecting cDNA into tumor cells resulted in a significant reduction in tumor growth. While integrin receptor α5β1 was overexpressed in tumor cells, its expression was corrected to the level found in control BEP2D cells after Betaig-h3 transfection. These data suggest that Betaig-h3 gene is involved in tumor progression by regulating integrin α5β1 receptor. Furthermore, exogenous TGF-β1 induced expression of Betaig-h3 gene and inhibited the growth of both control and tumorigenic BEP2D cells. Therefore, downregulation of Betaig-h3 gene may results from the decreased expression of upstream mediators such as TGF-β. The findings provide strong evidence that the Betaig-h3 gene has tumor suppressor function in radiation-induced tumorigenic human bronchial epithelial cells and suggest a potential target for interventional therapy.

Folic acid mediated attenuation of loss of heterozygosity of DCC tumor suppressor gene in the colonic mucosa of patients with colorectal adenomas

Loss of heterozygosity (LOH) and/or inactivation of tumor suppressor genes are implicated in the initiation and progression of many malignancies, including colorectal cancer. Although accumulating evidence suggests a chemopreventive role for folate in colorectal cancer, regulatory mechanisms are poorly understood. The primary objective of the current investigation was to determine whether folic acid would prevent LOH of the three tumor suppressor genes, deleted in colorectal cancer ( DCC), adenomatous polyposis coli ( APC) and p53 in macroscopically normal appearing rectal mucosa of patients with adenomatous polyps. In addition, the effect of folic acid on rectal mucosal proliferation was determined. Twenty patients were randomized in a double-blind study to receive either folic acid 5 mg once daily or identical placebo tablets for 1 year. Genomic DNA and total protein were extracted from the rectal mucosa at baseline and after 1 year of treatment and analyzed for LOH and protein levels of APC, DCC and p53 genes. In addition, paraffin-embedded mucosal specimens were analyzed for proliferating cell nuclear antigen (PCNA) immunoreactivity, as a measure of cellular proliferative activity. Folate supplementation prevented LOH of DCC gene in five out of five (100%) patients who demonstrated baseline heterozygosity, whereas two out of four (50%) placebo-treated patients with baseline heterozygosity demonstrated allelic loss. Mucosal protein levels of DCC were also reduced in 7 of 10 (70%) placebo-treated patients compared to only 2 of 10 (20%) of patients treated with folate. Levels increased, however, in eight and three patients in the folic acid and placebo groups, respectively ( P<0.02). Folic acid caused no change in allelic status of either APC or p53 gene. Folate supplementation caused a small, but not statistically significant, 16% reduction in mucosal proliferation, whereas placebo treatment resulted in a 88% ( P<0.05) increase in this parameter, when compared with the corresponding baseline values. Our results indicate that folic acid prevents an increase in proliferation and arrests LOH of DCC gene and also stabilizes its protein in normal appearing rectal mucosa of patients with colorectal adenomas. Taken together, our data suggest that one of the ways folate may exert its chemopreventive effect is by stabilizing certain tumor suppressor gene(s) and preventing further increases in proliferation.

Prognostic Significance of the Deleted in Colorectal Cancer Gene Protein Expression in High-Risk Resected Gastric Carcinoma

The deleted in colorectal cancer (DCC) gene is a candidate tumor suppressor gene that may be associated with differentiation and proliferation of normal cells. Loss of heterozygosity (LOH) of 18q, where the gene is located, and absence of DCC protein expression have been associated with worse prognosis in certain subgroups of patients with colorectal adenocarcinoma. We studied the prognostic significance of loss-of-protein expression in 66 patients with resected gastric cancer with a high probability of relapse (T3, T4, N+). The DCC protein was detected with immunohistochemistry using an anti-DCC monoclonal antibody on paraffin-embedded sections. The DCC protein expression was present in 51 cases (77.3%) and absent in 15 cases (22.7%). Poorly differentiated and signet ring carcinomas had significantly lower expression than more differentiated tumors(p<0.05) as did diffuse-type tumors compared to intestinal and mixed(p<0.01). There was no correlation with proliferation rate, estimated immunohistochemically using an anti-proliferating cell nuclear antigen (PCNA) monoclonal antibody. Absence of DCC protein was an independent favorable prognostic factor (median survival 57 months vs. 18 months,p=0.0176). The DCC protein expression was correlated with relapse site: all patients with distant metastases were positive for DCC staining, while one-third of patients with local/peritoneal relapse were negative(p<0.01). In conclusion, DCC protein expression seems to be a significant prognostic factor in high-risk resected gastric cancer. Our results support previous data associating the DCC gene with differentiation and indicate that this gene may play a role in the metastatic potential of these tumors. These findings need to be confirmed by future larger studies.

Cell Adhesion Proteins As Tumor Suppressors

We summarize recent progress on the role of cell adhesion molecules in biology and discuss the potential application of cell adhesion molecules for managing urological cancer. We comprehensively reviewed the literature from 1982 to 2001, including peer reviewed publications and recent abstracts from national meetings, relevant to cell adhesion molecules in urological cancer. A growing body of evidence suggests that alterations in the adhesion properties of neoplastic cells have a pivotal role in the development and progression of cancer. Loss of intercellular adhesion and desquamation of cells from the underlying lamina propria allows malignant cells to escape from their site of origin, degrade the extracellular matrix, acquire a more motile and invasion phenotype, and invade and metastasize. In addition to participating in tumor invasiveness and metastasis, adhesion molecules regulate or significantly contribute to various functions, including signal transduction, cell growth, differentiation, site specific gene expression, morphogenesis, immunological function, cell motility, wound healing and inflammation. To date a diverse system of transmembrane glycoproteins has been identified that mediates cell-cell and cell-extracellular matrix adhesion. The main families of adhesion molecules include members of the Ig superfamily, cadherins, integrins and selectins. Multiple and diverse cell adhesion molecules participate in intercellular and cell-extracellular matrix interactions of cancer. Cancer progression is a multistep process, in which some adhesion molecules have a pivotal role in the development of recurrent, invasive and distant metastasis. Recent data implicate some of these molecules in cell signaling and tumor suppression, which has important consequences for tumor growth.

Netrin-1 acts as a survival factor via its receptors UNC5H and DCC.

The membrane receptors DCC and UNC5H have been shown to be crucial for axon guidance and neuronal migration by acting as receptors for netrin-1. DCC has also been proposed as a dependence receptor inducing apoptosis in cells that are beyond netrin-1 availability. Here we show that the netrin-1 receptors UNC5H (UNC5H1, UNC5H2, UNC5H3) also act as dependence receptors. UNC5H receptors induce apoptosis, but this effect is blocked in the presence of netrin-1. Moreover, we demonstrate that UNC5H receptors are cleaved in vitro by caspase in their intracellular domains. This cleavage may lead to the exposure of a fragment encompassing a death domain required for cell death induction in vivo. Finally, we present evidence that during development of the nervous system, the presence of netrin-1 is crucial to maintain survival of UNC5H- and DCC-expressing neurons, especially in the ventricular zone of the brainstem. Altogether, these results argue for a role of netrin-1 during the development of the nervous system, not only as a guidance cue but as a survival factor via its receptors DCC and UNC5H.

Reduced expression of APC and DCC gene protein in breast cancer.

To investigate if the adenomatous polyposis coli (APC) protein and the deleted in colorectal cancer (DCC) protein expression can be demonstrated by an immuno-histochemical method and to study the role of APC and DCC gene inactivation in the development and progression of breast cancer using colorectal cancer as a control model. The reduced or loss of protein expression of the APC and DCC genes was studied in 27 surgical specimens of primary breast cancer using an immunohistochemical method. Reduced or lost expression was identified in 11 out of 27 samples (40.7%) for the APC gene and 15 out of 27 samples (55.6%) for the DCC gene. No statistically significant difference was observed between the reduced or lost protein expression and the histological grading of breast tumour for both the APC and the DCC gene. Both gene proteins can be demonstrated by the immunohistochemical method. Reduced or loss of APC and DCC gene product were observed in 40.7% and 55.6% cases of primary breast cancer respectively. Further work is required to investigate the significance of the finding.

The dependence receptor DCC defines a new mechanism for caspase activation

The DCC (Deleted in Colorectal Cancer) gene has been found to be deleted in more than 50% of primary colorectal cancers and in numerous other carcinomas, although the role of DCC as a tumor suppressor remains controversial. DCC is also a receptor for netrin-1, a lamininrelated molecule involved in axon guidance. Recently, we reported that DCC is actually a dependence receptor; such receptors create cellular states of dependence on their respective ligands by inducing apoptosis when unoccupied by ligand, but inhibiting apoptosis in the presence of ligand. Here, we show that DCC drives apoptosis through a mechanism requiring caspase-9 activation. Unexpectedly, if DCC kills through caspase-9, it does not go through the classic ‘mitochondria pathway’ since Bcl-2 and an inhibitor of cytochrome c release, cyclosporin A, are unable to block CCC-induced ceil death. Of interest, DCC intera& with both caspase3 and caspase-9 suggesting that DCC could play the role of an initiator complex for caspase activation. Moreover, in vitro translated DCC drives the activation of caspase-3 through caspase-9 without a requirement for cytochrome c. Hence, DCC defines the first pathway for cytochrome c-independent-and thus mitochondria-independentactivation of caspase-9.