1630

DCC

CRC18|CRCR1|IGDCC1|MRMV1|NTN1R1;DCC netrin 1 receptor;DCC;DCC netrin 1 receptor

colorectal cancer suppressor|colorectal tumor suppressor|deleted in colorectal cancer protein|deleted in colorectal carcinoma|immunoglobulin superfamily DCC subclass member 1|immunoglobulin superfamily, DCC subclass, member 1|netrin receptor DCC|tumor sup

18q21.3

protein-coding

expression of the DCC (deleted in colorectal cancer) protein is strongly induced during the neural differentiation of mouse P19 embryonal carcinoma (EC) cells that occurs when these cells are treated with retinoic acid (RA). Myc-associated zinc finger protein (MAZ) is a DNA-binding protein that is widely expressed and functions in human, mouse and hamster cells as an activator, an initiator or a terminator of transcription. However, the biological functions of MAZ remain elusive. We report here that MAZ associates with the cytoplasmic domain of the DCC protein in vivo and in vitro. Yeast two-hybrid assays confirmed this association. An immunofluorescence study demonstrated that DCC protein is expressed at elevated levels in neuron-like P19 EC cells, in particular in axons, in which the MAZ protein is also expressed. We found that MAZ was translocated from the nucleus to the cytoplasm during the RA-induced terminal differentiation of P19 EC cells with resultant loss of the ability of MAZ to bind to the ME1a1 site of the c-myc promoter. Taken together, our observations imply that the DCC protein might play a critical role as a signaling molecule in the regulation of the transcriptional activity of MAZ during the neural differentiation of P19 EC cells.

BACKGROUND: The deleted in colorectal cancer (DCC) protein, the product of DCC tumor suppressor gene, is frequently altered in cancer. Preclinical data demonstrate that DCC regulates beta-catenin levels. Here, we sought to determine the association of DCC with beta-catenin protein levels, clinicopathological parameters and patient outcome in ovarian cancer using a method of in situ compartmentalized protein analysis. METHODS: A tissue array composed of 150 advanced-stage ovarian cancers, treated with surgical debulking and platinum-paclitaxel (Taxol) combination chemotherapy, was constructed. For evaluation of protein expression, we used an immunofluorescence-based method of automated in situ quantitative measurement of protein analysis (AQUA). RESULTS: One hundred and twelve patients (74%) had sufficient tissue for AQUA. The median follow-up time for the entire cohort was 33 months. Patients with low nuclear DCC expression had a 3-year progression-free survival (PFS) rate of 0% compared with 33% of those with high DCC expression (P = 0.0067). In multivariate analysis, low nuclear DCC expression level retained its prognostic significance for PFS. Between DCC and beta-catenin, a significant relationship was found, where tumors with low DCC had low beta-catenin and vice versa (P = 0.003). CONCLUSIONS: Low nuclear DCC levels predict for poor patient outcome in epithelial ovarian cancer. DCC may exert its antitumor function, in part, through regulation of beta-catenin levels.

Deleted in colorectal cancer (DCC) is a candidate tumor-suppressor gene located at chromosome 18q21. However, DCC gene was found to have few somatic mutations and the heterozygous mice (DCC(+/-)) showed a similar frequency of tumor formation compared with the wild-type mice (DCC(+/+)). Recently, DCC came back to the spotlight as a better understating of its function and relationship with its ligand (netrin-1) had shown that DCC may act as a conditional tumor-suppressor gene. We evaluated hypermethylation as a mechanism for DCC inactivation in head and neck squamous cell carcinoma (HNSCC). DCC promoter region hypermethylation was found in 75% of primary HNSCC. There was a significant correlation between DCC promoter region hypermethylation and DCC expression (assessed by immunohistochemistry; P = 0.021). DCC nonexpressing HNSCC cell lines JHU-O12 and JHU-O19 with baseline hypermethylation of the DCC promoter were treated with 5-aza-2-deoxycytidine (a demethylating agent) and reexpression of DCC was noted. Transfection of DCC into DCC-negative HNSCC cell lines resulted in complete abrogation of growth in all cell lines, whereas additional cotransfection of netrin-1 resulted in rescue of DCC-mediated growth inhibition. These results suggest that DCC is a putative conditional tumor-suppressor gene that is epigenetically inactivated by promoter hypermethylation in a majority of HNSCC.

Netrins and their receptors deleted in colon cancer (DCC), neogenin, UNC5, and integrins are involved in axon guidance, epithelial morphogenesis, vascular pattering, cancer cell survival, invasion, tumor angiogenesis, and metastasis. Here, we considered the possible contribution of the p53-related apoptosis mediators p63 and p73 in the mechanisms underlying the antagonism between netrin-1 and DCC at the cell death control. We have showed that ectopic expression and external addition of netrin-1 in HeLa and HEK-293 cells with inactive p53 lead to impaired cell viability and induction of apoptosis. These responses were associated with up-regulation of the proapoptotic protein TAp73alpha, decreased Bcl-2/Bax ratio, and caspase-3 cleavage, with no change in protein levels of the antiapoptotic NH(2)-terminal-truncated DeltaNp73alpha isoform, p73 adapter Yap-1 and p73 E3 ubiquitin ligase Itch, and p63, as well as the transcripts encoding p63, TAp73alpha, and DeltaNp73alpha. However, the proteasome inhibitor MG132 potentiated, while DCC counteracted, netrin-1-induced TAp73alpha. Consistently, netrin-1 expression correlated with stabilization of the TAp73alpha protein and lower levels of TAp73alpha ubiquitination that was conversely enhanced by DCC, in a netrin-dependent manner. Our data indicate that netrin-1 selectively up-regulates TAp73alpha by preventing its ubiquitination and degradation. Targeted repression of p73alpha by shRNA reversed TAp73alpha and the apoptosis induced by netrin-1, and exacerbated the growth of HeLa tumor xenografts. Apoptosis induced by cisplatin was markedly enhanced in netrin-1 or DCC-expressing cells. Collectively, our data reveal that the transcriptionally active TAp73alpha tumor suppressor is implicated in the apoptosis induced by netrin-1 in a p53-independent and DCC/ubiquitin-proteasome dependent manner.

Since tumor suppressor gene DCC exhibits amino acid sequence homology to the neural cell adhesion molecule, there is a possibility that DCC might be related to tumor metastasis. In the present study, we examined 51 cases of primary esophageal carcinomas with regard to point mutations and loss of the DCC gene. We detected point mutations in two cases by screening using polymerase chain reaction-single strand conformation polymorphism analysis. When we determined the sequences, one case with lymph node metastasis showed an ATG (Met) to ACG (Thr) missense mutation in codon 168. Another case showed a CGA (Arg) to GGA (Gly) mutation in codon 201, which might be a polymorphic change, and two other mutations resulting in no amino acid change. We also examined loss of heterozygosity of the DCC gene. Forty-four of the 51 cases (86%) were informative, and among them 10 cases (23%) showed allelic deletion. The further away the lymph node metastasis was from the primary tumor, the higher the frequency of allelic deletions became. We also found allelic deletions in moderately and poorly differentiated squamous cell carcinomas but not in well differentiated ones. These results indicate that alterations of the DCC gene are related to the degree of lymph node metastasis and the degree of differentiation.