Mirror Hand Movements Caused by a Deletion of the DCC Gene

This case report describes the evaluation of 16-year-old twins with chromosomal microarray and mirror movements.

Identification of specific codon 201 mutation of the DCC Gene in the colonoscopic specimen of colorectal cancer

Objective

To identify the mutation in codon 201 of the deleted in colorectal cancer gene in colorectal cancer, and to correlate that mutation to the histopathological grading of colorectal cancer.

METHODS

The cross-sectional study was conducted from February 2019 to February 2021 after approval from the ethics review board of the Dow University of Health Sciences, Karachi, and comprised biopsy-proven colorectal cancer patients regardless of age and gender. After histopathological reporting, formalin-fixed paraffin-embedded tissue blocks of colorectal cancer were used for deoxyribonucleic acid extraction, followed by polymerase chain reaction optimisation and deoxyribonucleic acid Sanger sequencing for mutational analysis. Data was analysed using SPSS 25.

RESULTS

Of the 100 biopsy specimens assessed, 45(45%) were selected. Of them, 13(29%) samples failed to show any band on gel electrophoresis. The remaining 32(71%) samples were used for Sanger sequencing. Of these, 1(3%) sample did not sequence, while 31(97%) showed sequencing. All the sequenced samples identified a mutation in codon 201 of exon 3 in the deleted in colorectal cancer gene; 30(97%) showed homozygosity, and 1(3%) showed heterozygosity. No significant association of point mutation was noted with various demographic and clinicopathological parameters (p>0.05).

Conclusion

The deleted in colorectal cancer gene's missense mutation in codon 201 was frequently observed in colorectal cancer patients.

Genetic Events Responsible for Colorectal Tumorigenesis: Achievements and Challenges

Colorectal carcinogenesis is a multistep process that is accompanied by accumulation of changes in proto-oncogenes and tumor-suppressor genes. APC/MCC, RAS, DCC, p53 mutations and/or allelic losses, hyperexpression of c-MYC and RB genes, as well as other genomic alterations appear at characteristic stages of tumor development and are observed in most neoplasms. However, consideration of each of these abnormalities leaves many unanswered questions. The striking data on recurrent amplification of the RB tumor-suppressor gene as well as suppressive activities of protein kinase C and activated RAS genes, at least in some colon carcinoma cell lines, suggest the unusual effects of some signalling pathways in colonic epithelial cells. The results obtained to date indicate that distinct sets of genetic changes may underlie the development of colorectal tumors.

Using an Inbred Horse Breed in a High Density Genome-Wide Scan for Genetic Risk Factors of Insect Bite Hypersensitivity (IBH)

While susceptibility to hypersensitive reactions is a common problem amongst humans and animals alike, the population structure of certain animal species and breeds provides a more advantageous route to better understanding the biology underpinning these conditions. The current study uses Exmoor ponies, a highly inbred breed of horse known to frequently suffer from insect bite hypersensitivity, to identify genomic regions associated with a type I and type IV hypersensitive reaction. A total of 110 cases and 170 controls were genotyped on the 670K Axiom Equine Genotyping Array. Quality control resulted in 452,457 SNPs and 268 individuals being tested for association. Genome-wide association analyses were performed using the GenABEL package in R and resulted in the identification of two regions of interest on Chromosome 8. The first region contained the most significant SNP identified, which was located in an intron of the DCC netrin 1 receptor gene. The second region identified contained multiple top SNPs and encompassed the PIGN, KIAA1468, TNFRSF11A, ZCCHC2, and PHLPP1 genes. Although additional studies will be needed to validate the importance of these regions in horses and the relevance of these regions in other species, the knowledge gained from the current study has the potential to be a step forward in unraveling the complex nature of hypersensitive reactions.

Comparison of promoter hypermethylation pattern in salivary rinses collected with and without an exfoliating brush from patients with HNSCC

BACKGROUND

Salivary rinses have been recently proposed as a valuable resource for the development of epigenetic biomarkers for detection and monitoring of head and neck squamous cell carcinoma (HNSCC). Both salivary rinses collected with and without an exfoliating brush from patients with HNSCC are used in detection of promoter hypermethylation, yet their correlation of promoter hypermethylation has not been evaluated. This study was to evaluate the concordance of promoter hypermethylation between salivary rinses collected with and without an exfoliating brush from patients with HNSCC. METHODOLGY: 57 paired salivary rinses collected with or without an exfoliating brush from identical HNSCC patients were evaluated for promoter hypermethylation status using Quantitative Methylation-Specific PCR. Target tumor suppressor gene promoter regions were selected based on our previous studies describing a panel for HNSCC screening and surveillance, including P16, CCNA1, DCC, TIMP3, MGMT, DAPK and MINT31.

PRINCIPAL FINDINGS

In salivary rinses collected with and without brush, frequent methylation was detected in P16 (8.8% vs. 5.2%), CCNA1 (26.3% vs. 22.8%), DCC (33.3% vs. 29.8%), TIMP3 (31.6% vs. 36.8%), MGMT (29.8% vs. 38.6%), DAPK (14.0% vs. 19.2%), and MINT31 (10.5% vs. 8.8%). Spearman's rank correlation coefficient showed a positive correlation between salivary rinses collected with and without brush for P16 (ρ = 0.79), CCNA1 (ρ = 0.61), DCC (ρ = 0.58), TIMP3 (ρ = 0.10), MGMT (ρ = 0.70), DAPK (ρ = 0.51) and MINT31 (ρ = 0.72) (P<0.01). The percent agreement of promoter methylation between salivary rinses with brush and without brush were 96.5% for P16, 82.5% for CCNA1, 78.9% for DCC, 59.7% for TIMP3, 84.2% for MGMT, 84.2% for DAPK, and 94.7% for MINT31.

CONCLUSIONS

Our study demonstrated strong correlations of gene promoter hypermethylation between salivary rinses collected with and without an exfoliating brush. Salivary rinse collection without using an exfoliating brush may offer a cost effective, rapid, non-invasive, and reliable means for development of epigenetic salivary rinse biomarkers.

Detection of TIMP3 promoter hypermethylation in salivary rinse as an independent predictor of local recurrence-free survival in head and neck cancer

PURPOSE

To validate a panel of methylation-based salivary rinse biomarkers (P16, CCNA1, DCC, TIMP3, MGMT, DAPK, and MINT31) previously shown to be independently associated with poor overall survival and local recurrence in a larger, separate cohort of patients with head and neck squamous cell carcinoma (HNSCC).

EXPERIMENTAL DESIGN

One hundred ninety-seven patients were included. All pretreatment saliva DNA samples were evaluated for the methylation status of the gene promoters by quantitative methylation-specific PCR. The main outcome measures were overall survival, local recurrence-free survival, and disease-free survival.

RESULTS

In univariate analyses, the detection of hypermethylation of CCNA1, MGMT, and MINT31 was significantly associated with poor overall survival; the detection of hypermethylation of TIMP3 was significantly associated with local recurrence-free survival; and the detection of hypermethylation of MINT31 was significantly associated with poor disease-free survival. In multivariate analyses, detection of hypermethylation at any single marker was not predictive of overall survival in patients with HNSCC; detection of hypermethylation of TIMP3 in salivary rinse had an independent, significant association with local recurrence-free survival (HR = 2.51; 95% CI: 1.10-5.68); and none of the studied markers was significantly associated with disease-free survival.

CONCLUSION

The detection of promoter hypermethylation of the seven genes in salivary rinse as an independent prognostic indicator of overall survival in patients with HNSCC was not validated. Detection of promoter hypermethylation of TIMP3 in pretreatment salivary rinse is independently associated with local recurrence-free survival in patients with HNSCC and may be a valuable salivary rinse biomarker for HNSCC recurrence.

Methylation of the DCC gene is lost in advanced gastric cancer

BACKGROUND

Deleted in colorectal carcinoma (DCC), one of the Netrin-1 receptors, belongs to the functional dependence receptor family, members of which share the ability to induce apoptosis in the absence of their ligands. Recently, we examined the methylation status of the DCC gene in colorectal carcinomas and found that aberrant methylation of the DCC gene was detected in 28 out of the 50 (56%) primary colon carcinomas. This result prompted us to examine the methylation status of the DCC gene in gastric carcinoma.

MATERIALS AND METHODS

The methylation status of the DCC gene was examined in primary carcinomas and the corresponding normal tissues derived from 36 patients with gastric cancer using quantitative methylation-specific polymerase chain reaction (qMSP) and the correlation between the methylation status and the clinicopathological findings was evaluated.

RESULTS

Aberrant methylation of the DCC gene was detected in 16 out of the 36 (44%) primary gastric carcinomas. A significant difference was observed in regard to the TNM stage (p=0.0093).

CONCLUSION

DCC methylation was observed in the course of gastric carcinogenesis and disappeared in advanced gastric carcinoma.

Deleted in colorectal cancer is a putative conditional tumor-suppressor gene inactivated by promoter hypermethylation in head and neck squamous cell carcinoma

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.

[Netrin-1 and axonal guidance: signaling and asymmetrical translation]

More than 10 years after its initial discovery, netrin-1 - the first described chimioattractive molecule controlling the guidance of the commissural axons - has recently known a unsuspected wave of interest because of its implication in the development of the nervous system but also, more recently, fot its role in angiogenesis and tumorigenesis. Because, of a series of recent publications on netrin-1 signaling, we propose here to describe the recent insight in netrin-1 signaling via its main receptor DCC (deleted in colorectal cancer), and the recent discovery that netrin controls the assymetric distribution of beta-actin in the growth cone. Thus, it seems that netrin-1, but also the neurotrophic factor BDNF, controls acute growth cone responses such as collapse and turning by the regulation of localized protein translation, such as beta-actin. This process involves both transport of beta-actin mRNA, bound to Vg1RBP, to specific locations, and mRNA translation upon stimulation by local activation of the translation initiation regulator eIF-4E-binding protein 1. Indeed, Netrin-1 induces the movement of Vg1RBP granules into filopodia, and triggers a polarized increase in beta-actin translation on the near side of the growth cone before growth cone turning. The binding of BDNF to its receptor Trk has a similar effect for growth cone attraction, althought it is differentially regulated. Thus, this asymetrically synthesized beta-actin may direct actin polymerization and consequently the migration of the growth cone toward the cue.

Automated quantitative analysis of DCC tumor suppressor protein in ovarian cancer tissue microarray shows association with β-catenin levels and outcome in patients with epithelial ovarian cancer

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.

[Biomolecular prognostic factors in colorectal cancer]

There is general agreement that staging of colorectal neoplasms based on classic anatomopathological parameters does not allow accurate selection of patients at higher risk of an adverse outcome. For this reason, identification of new prognostic factors is desirable. Such factors should be easily determined and expressed at an early stage of carcinogenesis. Moreover, it would be useful to identify factors predictive of response to radiotherapy and chemotherapy. Various molecules are involved in the carcinogenetic pathway and metastasis formation. The aim of this review is to analyse whether any of them are currently useful in clinical practice and which of them warrant further study. At present, apart from CEA, whose prognostic value has been known for some time, we do not have sufficient data to definitively incorporate any of the other biomarkers in clinical practice. The most promising factors would appear to be loss of heterozigosity of chromosome 18q21 (DCC) and microsatellite instability. However, other molecules warrant further in-depth study. In particular, growth factor receptors may play a role not only as prognostic factors but also in view of their therapeutic potential.

Adequacy of Colonoscopic Biopsy Specimens for Molecular Analysis: A Comparative Study With Colectomy Tissue

Molecular analyses of tumors are increasingly useful for prognosis and for guiding therapy. Colonoscopic biopsy provides the first source of tissue for most cases of colorectal carcinoma and therefore might become an important source for molecular analyses. We have addressed the question whether molecular analyses of colonoscopic biopsy yield results similar to the findings from the surgical specimen. Further, we analyzed 2 separate areas of the colectomy specimen to assess tumor heterogeneity. We evaluated 3 samples from each of 67 patients for point mutations in the KRAS gene, loss of heterozygosity (LOH) at the Adenomatous Polyposis Coli (APC) and Deleted in Colon Cancer (DCC) genes and for microsatellite instability (MSI) using polymerase chain reaction based techniques. The average time interval between biopsy and surgery was 2.2+/-0.15 weeks. Lesions were from all colon segments and all surgical stages. The degree of agreement between the biopsy and surgical sites was high for APC LOH, MSI, and KRAS mutations (kappa=0.85, 1.00, and 0.93, respectively) but less so for DCC LOH (kappa=0.62). Colonoscopic biopsies are an acceptable source of neoplastic DNA for studies of KRAS, APC LOH, and MSI, but less so for DCC LOH, primarily resulting from technical considerations.

Targeting determinants of dosage compensation in Drosophila

The dosage compensation complex (DCC) in Drosophila melanogaster is responsible for up-regulating transcription from the single male X chromosome to equal the transcription from the two X chromosomes in females. Visualization of the DCC, a large ribonucleoprotein complex, on male larval polytene chromosomes reveals that the complex binds selectively to many interbands on the X chromosome. The targeting of the DCC is thought to be in part determined by DNA sequences that are enriched on the X. So far, lack of knowledge about DCC binding sites has prevented the identification of sequence determinants. Only three binding sites have been identified to date, but analysis of their DNA sequence did not allow the prediction of further binding sites. We have used chromatin immunoprecipitation to identify a number of new DCC binding fragments and characterized them in vivo by visualizing DCC binding to autosomal insertions of these fragments, and we have demonstrated that they possess a wide range of potential to recruit the DCC. By varying the in vivo concentration of the DCC, we provide evidence that this range of recruitment potential is due to differences in affinity of the complex to these sites. We were also able to establish that DCC binding to ectopic high-affinity sites can allow nearby low-affinity sites to recruit the complex. Using the sequences of the newly identified and previously characterized binding fragments, we have uncovered a number of short sequence motifs, which in combination may contribute to DCC recruitment. Our findings suggest that the DCC is recruited to the X via a number of binding sites of decreasing affinities, and that the presence of high- and moderate-affinity sites on the X may ensure that lower-affinity sites are occupied in a context-dependent manner. Our bioinformatics analysis suggests that DCC binding sites may be composed of variable combinations of degenerate motifs.

Deletion mapping of 18q in conventional renal cell carcinoma

Loss of heterozygosity (LOH) is frequently associated with the inactivation of tumor suppressor genes. 18q LOH has been frequently reported in colorectal cancer and lung cancer; however, allelic loss on 18q has not been investigated in renal cell carcinoma (RCC). We evaluated LOH on 18q using nine microsatellite markers in 126 with conventional RCC (cRCC). LOH was observed in more than one 18q microsatellite locus in 24 cRCC (19%). We found the highest frequency of LOH (13.5%) at 18q21.3, where the DCC gene is located. We also assessed the relationship between LOH frequency and patient clinical parameters. Patients with a family history of cancer had a significantly higher frequency of 18q LOH than those without such a history (P=0.0017). No associations were found with other parameters, including gender, tumor grade, tumor stage, smoking status, and body mass index. The results suggest that inactivation of tumor suppressor genes at 18q21.3, including DCC and SMAD4 as candidates, may be involved in the tumorigenesis of some conventional RCCs.

Presenilin attenuates receptor-mediated signaling and synaptic function

Presenilin (PS) plays an essential role in intramembranous gamma-secretase processing of amyloid precursor protein (APP) and several membrane-bound proteins. Here we report that selective accumulation of a membrane-tethered deleted in colorectal cancer (DCC) derivative (DCC-alpha) correlates with extensive neurite outgrowth in transfected neuroblastoma cells and axodendritic connectivity associated with increased spine density in cortical neurons derived from PS1(-/-) embryos, as well as wild-type neurons treated with gamma-secretase inhibitors. cAMP-dependent signaling was also increased in both the neuroblastoma and cortical neuron systems. As a physiological consequence of increases in axodendritic connectivity and in the magnitude of cAMP-dependent signaling, short- and long-term glutamatergic synaptic transmission was enhanced in PS-deficient neurons. Together, these results demonstrate for the first time that PS-mediated gamma-secretase activity attenuates receptor-mediated intracellular signaling pathways that are critical in regulating glutamatergic synaptic transmission and memory processes.

Role of netrin-1 and netrin-1 dependence receptors in colorectal cancers

Although cancer is a multifaceted disease, all cancer types share identical molecular and cellular mechanisms. These mechanisms involve a collection of alterations critical to the normal physiological functioning of cells, such as alterations of growth factor signalling pathways, angiogenesis, cell adhesion signals, DNA replication and apoptotic cell death. Many genes involved in the processes enumerated above are functionally inactive in tumour cells, designating them as putative ‘tumour suppressor genes’. Back in the early 1990s, Vogelstein and colleagues suggested that a gene called DCC (for Deleted in Colorectal Cancer) could be a tumour suppressor gene because it was found to be deleted in more than 70% of colorectal cancers, as well as in many other cancers. During the last 15 years, controversial data have failed to firmly establish whether DCC is indeed a tumour suppressor gene. However, the recent observations that DCC triggers cell death and is a receptor for netrin-1, a molecule recently implicated in colorectal tumorigenesis, have prompted a renewal of interest in the role of DCC in tumorigenesis and suggest that the netrin-1/receptor pairs act as novel negative regulators of tumour development.

Mapping netrin receptor binding reveals domains of Unc5 regulating its tyrosine phosphorylation

Netrin and its receptors Unc5 and deleted in colorectal carcinoma (DCC) regulate axon guidance and cell migration. We defined domains involved in the interactions between netrin-1, DCC, and Unc5c. We show that Unc5 requires both Ig domains to interact with netrin. DCC binds through the fourth fibronectin type III domain, whereas netrin binds through multiple domains to both receptors. We examined the functional consequences of removing the netrin binding and nonbinding domains from Unc5 in vitro and in vivo. In human embryonic kidney 293 cells, removal of the netrin binding second Ig domain causes an increase in basal tyrosine phosphorylation, whereas removal of the netrin nonbinding thrombospondin domains decreases tyrosine phosphorylation. Moreover, experiments in Caenorhabditis elegans indicate that both netrin binding and nonbinding domains are necessary for phenotypic rescue of an unc-5 loss of function mutation.

Molecular staging for survival prediction of colorectal cancer patients

PURPOSE

The Dukes' staging system is the gold standard for predicting colorectal cancer prognosis; however, accurate classification of intermediate-stage cases is problematic. We hypothesized that molecular fingerprints could provide more accurate staging and potentially assist in directing adjuvant therapy.

METHODS

A 32,000 cDNA microarray was used to evaluate 78 human colon cancer specimens, and these results were correlated with survival. Molecular classifiers were produced to predict outcome.

RESULTS

Molecular staging, based on 43 core genes, was 90% accurate (93% sensitivity, 84% specificity) in predicting 36-month overall survival in 78 patients. This result was significantly better than Dukes' staging (P = .03878), discriminated patients into significantly different groups by survival time (P < .001, log-rank test), and was significantly different from chance (P < .001, 1,000 permutations). Furthermore, the classifier was able to discriminate a survival difference in an independent test set from Denmark. Molecular staging identifies patient prognosis (as represented by 36-month survival) more accurately than the traditional clinical staging, particularly for intermediate Dukes' stage B and C patients. The classifier was based on a core set of 43 genes, including osteopontin and neuregulin, which have biologic significance for this disease.

CONCLUSION

These data support further evaluation of molecular staging to discriminate good from poor prognosis patients, with the potential to direct adjuvant therapy.

Application of cycling gradient capillary electrophoresis to detection of APC, K-ras, and DCC point mutations in patients with sporadic colorectal tumors

A previously introduced technique of cycling gradient capillary electrophoresis (CGCE) was applied to monitoring of molecular changes during adenoma-carcinoma transition in progression of sporadic colorectal cancer. The purpose of this work was optimization of separation parameters for selected mutation regions in tumor suppressor genes involved in the early stages of colorectal carcinogenesis, followed by scanning for these mutations in clinical tissue samples from patients with adenomatous polyps and early carcinomas. A total of 47 colorectal tumors in various stages of progression were examined. Main emphasis was given to evaluation of mutation detection sensitivity and specificity required for effective early disease detection. A total of 7 different somatic mutations was identified among 32 K-ras mutant samples, 1 inherited mutation and 5 somatic mutations were identified among 15 adenomatous polyposis coli (APC) mutated samples. None of the two previously reported "deleted in colorectal carcinomas" (DCC) mutations was found in any of the clinical samples. In addition to simple optimization of running conditions, CGCE has demonstrated sensitivity and selectivity allowing detecting small mutant fractions as well as combination of multiple mutants within a single target sequence.

[Study on loss of heterozygosity and microsatellite instability in hepatocellular carcinoma]

OBJECTIVE

To investigate the role of loss of heterozygosity (LOH) in tumor suppressor genes (TSG) and microsatellite instability (MSI) in hepatocarcinogenesis, as well as their correlation with clinicopathologic features.

METHODS

LOH in 6 TSG (APC, DCC, MCC, OGG1, p53 and RB1) was detected in 36 informative cases of hepatocellular carcinoma (HCC), among 92 surgically resected HCC. Thirteen polymorphic microsatellite markers were also studied in 15 of these cases by microdissection-based PCR amplification and direct DNA sequencing. The correlation between genetic alterations and clinicopathologic features was analyzed.

RESULTS

The overall incidence of LOH in HCC was 41.7% (15/36). There was no LOH in MCC gene. 46.2% (6/13) microsatellites showed LOH in 9 of the 15 cases of HCC (60%). Certain clinicopathologic differences were observed between cases (number = 7) with LOH in APC, OGG1 and DCC ("type I") and cases (number = 8) with LOH in p53 and RB1 ("type II"). The mean tumor size of these two types was 2.9 (+/- 1.7) cm and 7.2 (+/- 3.4) cm, respectively (P < 0.01); and the mean survival was 72.0 (+/- 38.6) months, and 51.0 (+/- 30.4) months, respectively (P < 0.05).

CONCLUSIONS

Compared with MSI pathway, LOH pathway plays a more important role in the development of HCC. A multistep hepatocarcinogenesis is likely, with LOH in APC, OGG1 and DCC ("type I") being an early event and LOH in p53 and RB1 ("type II") being a late event. On the other hand, MCC gene seems to play no role in the whole process.

Les récepteurs à dépendance DCC et UNC5H : rôle de l'apoptose dans le contrôle de la tumorigenèse

Recent studies have led a different view about membrane receptors. While a receptor used to be considered as inactive until bound by its ligand, it has been proposed that some receptors may also be active in the absence of their ligand. These so-called dependence receptors induce a specific death signal when the ligand is absent from the cell. Therefore, the expression of one of these receptors drives the cell to become dependent on the presence of the ligand for its survival. We have hypothesized that this mechanism allows inhibition of tumor growth, by inducing apoptosis of "abnormal" cells that would usually grow when ligand are unavailable--i.e., during local growth of tumor cells or growth beyond primary tumor site -. Along this line, back in the early 90s, Vogelstein and colleagues suggested that a gene called DCC (for "deleted in colorectal cancer") could be a tumor suppressor gene because it was found to be deleted in more than 70 % of colorectal cancers, as well as in many other cancers. During the last fifteen years, controversial data have failed to firmly establish whether DCC is indeed a tumor suppressor gene. However, our observation that DCC behaves as a dependence receptor that induces cell death unless its ligand netrin-1 is present, together with the fact that mice engineered to block DCC-induced cell death by overexpressing netrin-1 are predisposed to develop colorectal tumors, strengthen the role of dependence receptors as tumor suppressors. In this review, we will describe the implication of the netrin-1/receptor pairs as novel negative regulators of tumor development.

Two colons-two cancers: paradigm shift and clinical implications

Embryological and physiological data suggest that proximal (in relation to the splenic flexure) and distal parts of the colon represent distinct anatomical and functional entities. Since 1990, molecular biologists have identified two distinct pathways, microsatellite instability (MSI) and chromosomal instability (CIN), which are involved in the pathogenesis of colon cancer (CC). Thus, a new paradigm has emerged with the discovery that CC is a heterogeneous disease; furthermore recent data have demonstrated that these two distinct pathways in colorectal carcinogenesis are characterized by a different clinical outcome. The implications for the clinicians are twofold; (1) tumors originating from the proximal colon have a better prognosis due to a high percentage of MSI-positive lesions; and (2) location of the neoplasm in reference to the splenic flexure should be documented before group stratification in ongoing trials of adjuvant chemotherapy for CC. In the future, clinical decision-making regarding adjuvant chemotherapy might be stratified according to the MSI status of cancers located proximally to the splenic flexure.

Netrin-1 and its receptors in tumorigenesis

Netrin-1 and its receptors DCC (deleted in colorectal cancer) and the UNC5 orthologues (human UNC5A-D and rodent UNC5H1-4) define a new mechanism for both the positive (induction) and negative (suppression) regulation of apoptosis. Accumulating evidence implies that for human cancers, this positive signalling pathway is frequently inactivated. Surprisingly, binding of netrin-1 to its receptors inhibits tumour suppressor p53-dependent apoptosis, and p53 is directly involved in transcriptional regulation of netrin-1 and its receptors. So, the netrin-1 receptor pathways probably play an important part in tumorigenesis.

Genetic predisposition to colorectal cancer

High-penetrance mutations in several genes have been identified that contribute to hereditary colorectal cancer. The role of these mutations in cancer pathogenesis is well understood and their detection is successfully used in clinical diagnosis. In stark contrast, our understanding of the influence of low-penetrance mutations that account for most of the remaining familial cases of colorectal cancer, as well as an unknown proportion of sporadic cases, is far less advanced. Extensive ongoing research into low-penetrance, multifactorial predisposition to colorectal cancer is now beginning to bear fruit, with important implications for understanding disease aetiology and developing new diagnostic, preventive and therapeutic strategies.

Ki-ras gene mutations, LOH of the APC and DCC genes, and microsatellite instability in primary colorectal carcinoma are not associated with micrometastases in pericolonic lymph nodes or with patients' survival

AIMS

The primary aim of this study was to look for possible correlations between molecular genetic changes in primary colorectal cancer and the presence or absence of micrometastases in the accompanying pericolonic lymph nodes. The secondary aim was to correlate the data on these molecular genetic changes and micrometastases with survival.

METHODS

One hundred and twenty five Dukes's stage B colorectal cancers from 1989 to 1992 were analysed. The primary tumours were evaluated for Ki-ras mutation, adenomatous polyposis coli (APC) loss of heterozygosity (LOH), deleted in colon cancer (DCC) LOH, and microsatellite instability using standard molecular techniques. All available lymph nodes were immunohistochemically stained for micrometastases.

RESULTS

Micrometastases were present in 41% of patients. There were significantly more lymph nodes removed in the patients with micrometastases. Micrometastases were not associated with Ki-ras mutation, APC LOH, DCC LOH, or microsatellite instability, even when controlling for the number of lymph nodes removed. None of the molecular variables considered had a significant impact on either overall survival or on death with disease.

CONCLUSIONS

There are insufficient data to justify using molecular genetic changes in primary colorectal carcinomas as prognostic markers. Micrometastases do not provide prognostic information on survival. There is value in increasing the numbers of lymph nodes removed and analysed along with the primary tumour.

P53 and Rb tumor suppressor gene alterations in gastric cancer

Inactivation of tumor suppressor genes has been frequently observed in gastric carcinogenesis. Our purpose was to study the involvement of p53, APC, DCC, and Rb genes in gastric carcinoma.

METHOD

Loss of heterozygosity of the p53, APC, DCC and Rb genes was studied in 22 gastric cancer tissues using polymerase chain reaction; single-strand conformation polymorphism of the p53 gene exons 5-6 and exons 7-8 was studied using 35S-dATP, and p53 expression was detected using a histological immunoperoxidase method with an anti-p53 clone.

RESULTS AND DISCUSSION

No loss of heterozygosity was observed in any of these tumor suppressor genes; homozygous deletion was detected in the Rb gene in 23% (3/13) of the cases of intestinal-type gastric carcinoma. Eighteen (81.8%) cases showed band mobility shifts in exons 5-6 and/or 7-8 of the p53 gene. The presence of the p53 protein was positive in gastric cancer cells in 14 cases (63.6%). Normal gastric mucosa showed negative staining for p53; thus, the immunoreactivity was likely to represent mutant forms. The correlation of band mobility shift and the immunoreactivity to anti-p53 was not significant (P =.90). There was no correlation of gene alterations with the disease severity.

CONCLUSIONS

The inactivation of Rb and p53 genes is involved in gastric carcinogenesis in our environment. Loss of the Rb gene observed only in the intestinal-type gastric cancer should be further evaluated in association with Helicobacter pylori infection. The p53 gene was affected in both intestinal and diffuse histological types of gastric cancer.

The deleted in colorectal carcinoma (DCC) gene 201 R → G polymorphism: no evidence for genetic association with autoimmune disease

The product of the deleted in colorectal carcinoma (DCC) gene has a role in apoptosis and is a positional candidate for IDDM6, the putative chromosome 18q12-q23 autoimmune disease locus. We hypothesised that a nonconservative substitution (DCC 201 R --> G; nucleotide (nt) 601 C --> G), located in an extracellular immunoglobulin-like domain of DCC, is an aetiological determinant of autoimmunity. We tested this hypothesis by genetically testing the nt 601 C --> G polymorphism for association with three autoimmune phenotypes in a large population-based case-control study. There was no evidence for association of DCC nt 601 C --> G with autoimmune disease in cohorts comprising 2253 subjects with rheumatoid arthritis, type I diabetes and Graves' disease, and 2225 control subjects, from New Zealand and the United Kingdom. Furthermore, using the transmission disequilibrium test, there was no significant evidence for biased transmission of the nt 601 C --> G polymorphism to probands within a 382 family type I diabetes affected sibpair cohort from the United Kingdom. Thus, the DCC 201 R --> G polymorphism does not appreciably influence risk of developing the autoimmune diseases tested.

Intratumoral heterogeneity of genetic changes in primary colorectal carcinomas with metastasis

PURPOSE

To elucidate the intratumoral distribution of genetic changes, surgically resected colorectal carcinomas were investigated regarding their loss of heterozygosity in the regions of tumor suppressor genes and the mutation of ras genes.

METHODS

Full-thickness fresh tumor slices from 23 colorectal carcinomas were removed and divided into multiple specimens, which were then submitted separately for DNA and histopathological analyses. The loss of heterozygosity was analyzed in 23 primary carcinomas and 9 metastasized carcinomas by the use of restriction fragment-length polymorphism markers on chromosome 1p, 5q, 17p, 18q, and 22q.

RESULTS

Intratumoral heterogeneity was identified in 11 of 23 primary carcinomas (47.8%) and we could successfully map the regional genetic variation. In both stages I and II, 1 of 5 cases (20%); in stage III, 3 of 6 cases (50%); and in stage IV, 6 of 7 cases (85.7%) were heterogeneous. With respect to venous invasion positive primary carcinomas, hepatic metastasis occurred in 75% (6/8) of the heterogeneous carcinomas, whereas hepatic metastasis occurred in only 12.5% (1/8) of homogeneous carcinomas.

CONCLUSION

The present results suggest that the existence of intratumoral heterogeneity, which may reflect genetic instability, may thus play a role in the enhancement of aggressive progression and the metastasis of colorectal carcimomas.

Genetic alterations in ovarian carcinoma: with specific reference to histological subtypes

Multiple genetic changes including activation of proto-oncogenes and inactivation of tumor suppressor gene are involved in the development of human ovarian cancer. We describe such genetic alterations with specific reference to histological subtypes. K-ras activation is specific for mucinous tumors including adenomas. Borderline tumors and carcinomas, suggesting that K-ras activation may be associated with the mucinous differentiation rather than malignant transformation. Inactivation of p53 is detected in 30-40% of ovarian carcinoma. Mutations are more frequently observed in serous carcinomas, but not found in adenomas or rarely found in borderline tumors, suggesting that p53 mutations may be directly involved in malignant transformation. TGFbeta-2 mutations are found in 50% of endometrioid carcinoma, but rarely in other type. Loss of DCC mRNA expression is found in 50% of serous carcinomas but less frequently in other type. Loss of DCC expression is rare in borderline tumors and adenomas, suggesting that inactivation of DCC may be directly involved in malignant transformation. Microsatellite instability (MI) is found in 17% of ovarian carcinomas, and is frequently found in endometrioid carcinomas. Although inactivation of p16 by point mutation or deletion is rare, p16 inactivation by loss of expression is relatively common.

[Study on the expression of the gene deleted in colorectal carcinoma in ovarian carcinoma]

OBJECTIVE

The purpose of this study was to explore the relationship between the loss of the gene deleted in colorectal carcinoma (DCC) gene expression in ovarian carcinoma and the transformation, progression of the tumor and its clinicopathological factors.

METHODS

DCC gene mRNA expression were examined by reverse transcription polymerase chain reaction (RT-PCR) in 34 malignant, 10 benign and 10 normal ovarian samples. To clarify the expression of DCC gene by the DNA cloning and the DNA sequencing analysis in normal ovarian sample.

RESULTS

The expression of DCC gene was lost in no normal ovarian tissues, in 2 (2/10) benign lesions, while the loss of DCC gene expression was found in 19 (19/34, 56%) carcinomas (P < 0.05). Similar findings were also noted when subdivision was into serous (14/18) and mucinous (4/11) categories (P < 0.05). The percentage of the loss of DCC gene expression in stage III - IV was 68%, in stage I - II was 22%, as well as 42% in grade I - II and 90% in grade III. 61% of the carcinoma with metastasis presented the loss of DCC gene expression, then there was 33% in which without metastasis.

CONCLUSIONS

In ovarian carcinomas, loss of DCC gene expression was significantly related to the serous phenotype, a high histological grade and a more advanced stage. The results indicated that loss of DCC gene expression may play an important role in ovarian carcinomas and its progression.

[From molecular biology to new treatment approaches to colorectal cancer: basic research, experimental trials and surgical implications]

The Authors review the natural history of colorectal cancer from the point of view of molecular biology and genetics from aberrant crypts foci and familiar adenomatous polyposis to hereditary non polyposis colon cancer and sporadic colorectal cancer. They carry out international literature about basis knowledges, experimental trials and personal studies. Up to day traditional colorectal cancer surgical treatments and adjuvant or neoadjuvant pharmacological therapy cannot be modified, nevertheless "new drugs generation" known as signal transduction inhibitor could, in the future, prove to be an effective cancer treatment. The Authors highlight recent experimental clinical trials probably able to prevent sporadic colorectal cancer spreading and precursor evolution.

[Clinical, pathological and molecular prognostic factors in colorectal carcinomas]

Various aspects of the progression and prognosis of colorectal carcinoma have been investigated in numerous publications during recent years. An exact macroscopic and microscopic examination is still of basic importance but different factors of the molecular pathogenesis of colorectal carcinoma could be described by immunohistochemistry and molecular biology. Furthermore, they have been evaluated regarding their importance for the course of disease and prognosis and in particular, the different pathways of carcinogenesis and microsatellite instability were included. The detection of micrometastasis was investigated applying mostly molecular genetic methods. Numerous oncogenes, tumor suppressor genes and regulators of the cell cycle, markers of proliferation and apoptosis, cell adhesion antigens and angiogenetic factors were characterized with regard to their prognostic potential. In the future, so-called response predictors will presumably gain a certain relevance in the context of neoadjuvant (radiotherapy) chemotherapy. The present review summarizes these results and discusses the future clinical relevance.

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-beta), DCC (deleted in colorectal cancer), p21(cipl), 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 alpha 5 beta 1 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 alpha 5 beta 1 receptor. Furthermore, exogenous TGF- beta 1 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-beta. 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.

Genetic alterations in adenoma-carcinoma sequencing of intraductal papillary-mucinous neoplasm of the pancreas

We investigated the adenoma-carcinoma sequence in intraductal papillary-mucinous neoplasm from the aspect of genetic changes. The formalin-fixed paraffin-embedded tumors and surrounding normal pancreatic tissues from patients with 16 intraductal papillary-mucinous adenoma of the pancreas (IPMA) and 10 intraductal papillary-mucinous carcinoma of the pancreas (IPMC) were provided for DNA extraction after microdissection. SSCP-DNA sequencing analysis demonstrated K-ras mutations at codon 12 in 75% of IPMA and 70% of IPMC, while those at codon 13 were observed neither in IPMA nor IPMC. There were no characteristic K-ras mutation types in IPMA and IPMC and no significant differences in incidence of K-ras mutations between the two categories. The frequencies of p53 mutations analyzed by SSCP-DNA sequencing were not high in IPMA (18.8%) and IPMC (30%), showing no significant difference between them. LOHs of APC in IPMA and IPMC were infrequent (6.3 and 20%, respectively) and showed no significant difference in incidence between the two categories. The LOH frequencies of DCC in IPMA and IPMC were 31.3 and 40%, respectively, and were not statistically different from each other. Taken together, genetic changes such as K-ras, p53, APC and DCC mutations may not be associated with adenoma-carcinoma sequence in intraductal papillary-mucinous neoplasm of pancreas.

Mediation of the DCC apoptotic signal by DIP13 alpha

DCC (deleted in colorectal cancer) is a candidate tumor suppressor gene. However the function of DCC remains elusive. Previously, we demonstrated that forced expression of DCC induces apoptosis or cell cycle arrest (Chen, Y. Q., Hsieh, J. T., Yao, F., Fang, B., Pong, R. C., Cipriano, S. C. & Krepulat, F. (1999) Oncogene 18, 2747-2754). To delineate the DCC-induced apoptotic pathway, we have identified a protein, DIP13 alpha, which interacts with DCC. The DIP13 alpha protein has a pleckstrin homology domain and a phosphotyrosine binding domain. It interacts with a region on the DCC cytoplasmic domain that is required for the induction of apoptosis. Although ectopic expression of DIP13 alpha alone causes only a slight increase in apoptosis, co-expression of DCC and DIP13 alpha results in an approximately 5-fold increase in apoptosis. Removal of the DCC-interacting domain on DIP13 alpha abolishes its ability to enhance DCC-induced apoptosis. Inhibition of endogenous DIP13 alpha expression by small interfering RNA blocks DCC-induced apoptosis. Our data suggest that DIP13 alpha is a mediator of the DCC apoptotic pathway.

High resolution analysis of chromosome 18 alterations in ulcerative colitis-related colorectal cancer

We previously have demonstrated by comparative genomic hybridization that 80% of ulcerative colitis-related cancers show loss of all or part of chromosome 18, the site of at least three candidate tumor suppressor genes: DCC, SMAD2, and SMAD4. To determine whether these genes are targeted in colitis-related carcinogenesis, we performed a high-resolution analysis of chromosome 18 alteractions in 32 colitis-related colorectal cancers by assessing allelic imbalance at 11 microsatellite markers distributed along the chromosome, and by the quantitative polymerase chain reaction (PCR) method (TaqMan). TaqMan analysis was used to determine the relative copy number of five test genes on chromosome 18 (PACAP on 18p and DCC, SMAD2, SMAD4, and GALNR on 18q). We found allelic imbalance, as assessed by loss of heterozygosity, in at least one marker on chromosome 18 in 25 of the 29 tumors (86%) successfully tested. In 14 tumors, allelic imbalance was detected at all informative markers on 18q, while the other 11 tumors showed only partial loss. Allelic imbalance was most commonly detected at D18S363 (78% of informative cases). This marker is in closest proximity to SMAD4. By quantitative PCR analysis, a relative loss of copy number of SMAD2, SMAD4, and DCC were detected in 40%, 57%, and 53%, respectively, of the colitis-related cancers. SMAD2 was retained in four tumors having loss of SMAD4 and DCC. Loss of SMAD4 alone was seen in one tumor. The present data indicate that the loss of SMAD4 and DCC occurs in the majority of colitis-related cancers.

[Molecular alterations in esophageal cancer]

The clinicopathological characteristics of esophageal cancer have gradually been clarified using molecular biologic methods developed over the past 20 years. For example, amplification of the c-erb B gene is a prognostic factor and predictive of lymph node involvement, while the amplification of the cyclin D1 gene is also a prognostic factor and predictive of distant organ metastasis. Alteration of the p16 gene is also a prognostic factor and predicts lymph node involvement. As telomerase activity is almost a unique phenomenon of cancer cells, highly sensitive detection of esophageal cancer cells in the peripheral blood can be performed. Recently, such new methods as comparative genomic hybridization analysis and cDNA microarray analysis have been used to determine meaningful genetic changes. For therapeutic purposes, although tailor-made therapy has been proposed for several years, the validity of these approaches should be confirmed in a well-designed clinical trial. As molecular targeted therapies, tyrosine kinase inhibitors of epidermal growth factor receptor (EGFR) and monoclonal antibodies against EGFR are being studied in clinical trials in Western countries. A clinical trial of p53 gene therapy against esophageal cancer is also promising.

Characterization of novel cell lines established from three human oral squamous cell carcinomas

Human oral squamous cell carcinoma cell lines (KOSCC-11, -25A, -25B, -25C, -25D, -25E, -33A, and -33B) were established by explantation culture from these oral squamous cell carcinomas. The histopathology of the primary tumors, in vitro growth characteristics, epithelial origin, in vitro anchorage-independency, in vivo tumorigenicity, the frequency of human papillomavirus (HPV) infections, and the status of proto-oncogenes, tumor suppressor genes, DNA mismatch repair genes, and microsatellite instability were investigated in the cell lines. KOSCC-11 is a well-differentiated oral squamous cell carcinoma (OSCC) derived from mandibular gingiva. KOSCC-25A, -25B, -25C, -25D, and -25E cell lines were derived from the same OSCC. KOSCC-33A and -33B were established from the same tumor that originated from the maxillary sinus. All tumor lines studied grew as monolayers and showed: i) epithelial origin by the presence of desmosome and keratin; ii) in vitro anchorage-independent growth ability; and iii) tumorigenic potential in nude mice. The cancer cell lines did not contain HPV DNA and did not express viral genes. Northern blot analysis revealed: i) overexpression of EGFR in four cell lines, ii) overexpression of c-H-ras in four cell lines, iii) overexpression of c-myc in three cell lines, iv) decreased expression of TGF-alpha in seven cell lines, and v) decreased expression of c-jun in five cancer cell lines compared with normal human oral keratinocytes. In all KOSCC cell lines and their corresponding tumor tissues, mutations were identified in highly-conserved functional regions of the p53 gene. The KOSCC-11 cell line contained a frameshift mutation and the other cell lines harbored an identical p53 mutation at codon 175 from CGC (Arg) to CTC (Leu). In five cell lines, a significant reduction of p21WAF1/Cip1 protein was evident. Cancer cell lines expressed higher level of Rb protein than normal human oral keratinocytes. DCC, a tumor suppressor gene, was not detected in KOSCC-25C. The KOSCC-33A cell line displayed microsatellite instability and showed a loss of hMSH2 expression. These well-characterized human OSCC cell lines should serve as useful tools for understanding the biological characteristics of oral cancer.

Chromosome 2p, 3p, 5q and 18q status in sporadic gastric cancer

AIM

The genetic make-up of gastric cancers in low-risk population groups from South Africa is largely unknown. The purpose of this study was to ascertain the incidence of microsatellite instability and loss of heterozygosity in this population.

METHODS

Thirty-seven gastrectomy specimens for sporadic gastric cancer were analysed for the following clinicopathological parameters: age, gender, race, histopathological type, size of tumour, lymph node status and the presence/absence of Helicobacter pylori. DNA was then extracted from paraffin-embedded tissue and seven microsatellite markers in 2p, 3p, 5q and 18q loci were examined using automated DNA fluorescent technology.

RESULTS

Only eight cases showed microsatellite instability (MSI) for one marker and were thus categorised as MSI-low. In the 3p region, loss of heterozygosity (LOH) was detected in 21.7-38.3% of informative cases, whilst in the 18q region CLOH ranged from 25 to 38.4%. LOH was not seen in the 2p locus and only one case showed LOH in the 5q region. When the molecular changes were compared with clinicopathological parameters, a statistically significant relationship did not emerge with any single parameter.

CONCLUSIONS

This study shows that sporadic gastric cancer from a low-risk population in South Africa is MSI-low or MSI-stable, and that LOH in the 3p and 18q regions is similar to that seen in other low-risk populations from different geographical regions.

Comparison of clinicopathologic characteristics and genetic alterations between microsatellite instability-positive and microsatellite instability-negative sporadic colorectal carcinomas in patients younger than 40 years old

PURPOSE

Many studies have demonstrated that sporadic microsatellite instability-positive colorectal cancers share several clinicopathologic features with hereditary nonpolyposis colorectal cancers, including right-sided location, young age of onset, characteristic histomorphologic features, and a good prognosis. The aim of this study was to define distinct clinicopathologic features of sporadic microsatellite instability-positive colorectal cancers and to compare genotypic characteristics between microsatellite instability-positive and microsatellite instability-negative colorectal cancers in a young group.

METHODS

We analyzed 61 cases of young patients (<40 years old) with colorectal cancers for microsatellite instability at five mononucleotide and three dinucleotide repeats, loss of heterozygosity at APC and DCC, and K-ras and p53 mutations. Microsatellite instability status was correlated with molecular genetic factors and clinicopathologic parameters.

RESULTS

Microsatellite instability positivity was detected in 19 (31.1 percent) of 61 cases. Allelic alterations in TGFbetaRII, BAX, and IGFIIR were observed exclusively in microsatellite instability-positive tumors (63.1, 26.3, and 26.3 percent, respectively). Microsatellite instability-positive tumors exhibited a lower frequency of the p53 mutation (10.5 percent) than microsatellite instability-negative tumors (47.6 percent; P < 0.05). However, microsatellite instability status was not associated with APC or DCC allelic deletion or with the K-ras mutation. Microsatellite instability-positive colorectal cancers exhibited a proclivity toward proximal location, expansive growth pattern, and large tumor size (P < 0.05). Microsatellite instability-positive colorectal cancers had lower preoperative serum carcinoembryonic antigen levels (P < 0.05), a less advanced stage at presentation (P < 0.05), and a tendency toward better prognosis (P = 0.051) than microsatellite instability-negative colorectal cancers. However, there was no difference between microsatellite instability-positive and microsatellite instability-negative colorectal cancers regarding gross features, tumor grade, and extracellular mucin production.

CONCLUSION

These results suggest that sporadic microsatellite instability-positive colorectal cancers in young patients have different histomorphologic features from microsatellite instability-negative colorectal cancers and hereditary nonpolyposis colorectal cancers, some overlap of genetic alterations on multistep carcinogenesis with microsatellite instability-negative colorectal cancers, and a tendency for better prognosis.

Loss of DCC expression in astrocytomas: relation to p53 abnormalities, cell kinetics, and survival

AIMS

Although frequent reduction or loss of DCC (deleted in colorectal carcinomas) has been demonstrated in gliomas, the association with cell kinetics and survival is still unclear.

METHODS

A total of 119 astrocytomas, comprising 39 grade IV, 36 grade III, and 44 low grade tumours, were immunohistochemically investigated, along with 26 normal adult brain samples and two fetal brains. The results were compared with p53 abnormalities, Ki-67 labelling index (LI), mitotic index (MI), apoptotic index (AI), and survival.

RESULTS

In normal adult and fetal brain tissues, DCC expression was detected in mature and terminally differentiated neuronal cells but not glial elements. In astrocytomas, whereas DCC expression was still clearly shown with low grade malignancy, DCC scores were significantly decreased in high histological grade malignancy, along with an increase in cell kinetics determined by AI, MI, and Ki-67 LI values. In addition, p53 LI values were significantly increased, although a direct link between DCC scores and p53 LI values was not evident. Univariate analysis revealed that high DCC scores and low p53 LI values were closely related to a favourable outcome for astrocytoma, although only the AI was an independent prognostic factor.

CONCLUSIONS

The loss of DCC expression may be closely related to changes in cell kinetics and tumour phenotype in astrocytomas, independent of p53 abnormalities.

SMAD4 mutations in colorectal cancer probably occur before chromosomal instability, but after divergence of the microsatellite instability pathway

Loss of chromosome 18q21 is well documented in colorectal cancer, and it has been suggested that this loss targets the DCC, DPC4/SMAD4, and SMAD2 genes. Recently, the importance of SMAD4, a downstream regulator in the TGF-beta signaling pathway, in colorectal cancer has been highlighted, although the frequency of SMAD4 mutations appears much lower than that of 18q21 loss. We set out to investigate allele loss, mutations, protein expression, and cytogenetics of chromosome 18 copy number in a collection of 44 colorectal cancer cell lines of known status with respect to microsatellite instability (MSI). Fourteen of thirty-two MSI(-) lines showed loss of SMAD4 protein expression; usually, one allele was lost and the other was mutated in one of a number of ways, including deletions of various sizes, splice site changes, and missense and nonsense point mutations (although no frameshifts). Of the 18 MSI(-) cancers with retained SMAD4 expression, four harbored missense mutations in the 3' part of the gene and showed allele loss. The remaining 14 MSI(-) lines had no detectable SMAD4 mutation, but all showed allele loss at SMAD4 and/or DCC. SMAD4 mutations can therefore account for about 50-60% of the 18q21 allele loss in colorectal cancer. No MSI(+) cancer showed loss of SMAD4 protein or SMAD4 mutation, and very few had allelic loss at SMAD4 or DCC, although many of these MSI(+) lines did carry TGFBIIR changes. Although SMAD4 mutations have been associated with late-stage or metastatic disease, our combined molecular and cytogenetic data best fit a model in which SMAD4 mutations occur before colorectal cancers become aneuploid/polyploid, but after the MSI(+) and MSI(-) pathways diverge. Thus, MSI(+) cancers may diverge first, followed by CIN(+) (chromosomal instability) cancers, leaving other cancers to follow a CIN(-)MSI(-) pathway.

What we could do now: molecular pathology of colorectal cancer

The contribution of molecular genetics to colorectal cancer has been largely restricted to relatively rare inherited tumours and to the detection of germ line mutations predisposing to these cancers. However, much is now known about the somatic events leading to colorectal cancer in general. Several studies have examined the relation between genetic features and prognosis. The purpose of this article is to review these studies and summarise the current state of this subject. Although many of the published studies are small and inconclusive, it is clear that several different pathways exist for the development of this cancer, and some molecular characteristics seem to correlate with clinicopathological features. At present, studies are confined to evaluating a small number of molecular markers; however, with the advent of methods for the rapid genetic profiling of large numbers of colorectal cancers, it will be possible to evaluate fully the clinical usefulness of a range of colorectal cancer genotypes.

Expression patterns of the netrin receptor UNC5H1 among developing motor neurons in the embryonic rat hindbrain

The axon guidance molecule netrin-1 has been implicated in the midline repulsion of developing cranial motor axons. We have examined expression patterns of the netrin receptors UNC5H1 and DCC in embryonic rat hindbrains, in combination with labelling of developing motor neurons. We found that UNC5H1 expression colocalised with a number of cranial motor neuron subpopulations from embryonic day 11 (E11) to E14, while DCC was expressed by motor neurons at E12.

Frequent loss of expression without sequence mutations of the DCC gene in primary gastric cancer

Loss of heterozygosity (LOH) on chromosome 18q21 is frequently found in various human cancers, suggesting the presence of tumour suppressor gene(s) in this chromosomal region. DCC is the most likely target of LOH because loss or reduction of DCC expression has been found in many types of cancers. However, few reports have focused on sequence mutations of this gene. We investigated sequence mutations and expression of DCC in primary gastric cancers. We studied mutations in 25 of the 29 DCC exons by PCR-SSCP in 17 primary gastric cancers exhibiting LOH on 18q21. No mutations of DCC were found in any of the tumours, although 78% (47/60) of the primary tumours showed apparent loss or reduction of DCC expression by immunohistochemistry. Analysis of methylation status of DCC revealed that methylation frequently occurred in both primary tumours (75%; 45/60) and corresponding non-cancerous gastric mucosae (72%; 43/60). Methylated status of DCC was significantly correlated with the loss of DCC expression in primary tumours (P< 0.01). These results indicate that DCC is frequently silenced, probably by epigenetic mechanisms instead of sequence mutations in gastric cancer.

[Telomere length and DCC gene mRNA expression of human large intestine cancers]

OBJECTIVE

To evaluate the role of telomere and DCC in tumor transformation and progression.

METHODS

Telomere length and DCC gene mRNA expression were examined by southern blot hybridization and RT-PCR analysis in 46 adenomas of large intestine, 62 cancers of large intestine and corresponding normal mucosa.

RESULTS

Shortening of the telomere was present in the tissues of 41.3% of the adenomas and 53.2% of the cancers, and their average TRF lengths were significantly shorter than those of corresponding normal mucosa(P<0.05, P<0.01), whereas the telomere elongation was only detected in 4.4% and 6.5% of the adenomas and cancers respectively. In addition, the average telomere length in colon carcinomas was also shorter than that in rectal carcinomas. Moreover, the average telomere lengths of the colorectal cancer mucosa became shorter with age. The rates of DCC mRNA expression deletion were 34.8% and 62.9% in the tissues of adenomas and cancers respectively. The DCC mRNA expression deletion occurred more frequently in poorly differentiated and Dukes C, D carcinomas than in well-differentiated and Dukes A, B carcinomas (P<0.05, P<0.01). However, no significant correlation was found between the length of telomere and the deletion of DCC mRNA expression in the cancers of large intestine.

CONCLUSION

The telomere shortening and DCC mRNA deletion may represent the biologic behavior of transformation and development of the large intestine cancers.

[Relationship between genetic alterations and clinicopathological features in intrahepatic cholangiocarcinoma]

OBJECTIVE

To evaluate the pedigree of genetic alterations during the tumorigenesis of intrahepatic cholangiocarcinoma (ICC) and their correlation with clinicopathological features by analysis of loss of heterozygosity (LOH) in 6 tumor suppressor genes (APC, MCC, DCC, OGG1, p53 and RB1) and point mutations in Ki-ras-2 oncogene.

METHODS

Genomic DNA was isolated from paraffin-embedded slides of 22 surgically resected ICC cases by microdissection-based PCR amplification and agarose gel electrophoresis. Genetic alterations were analyzed by direct DNA sequencing.

RESULTS

The total frequency of alterations in 7 genes studied was 86.4% (19/22). Based on the pattern of altered genes and their correlation with clinicopathological parameters, the genetic alterations were classified into two groups: Group I (9/19, 47.4%): alterations in APC, MCC, DCC and Ki-ras-2,); Group II (10/19, 52.6%): alterations in p53, OGG1 and RB1. The average age of patients in Group I (mean age, 57.2 years) was significantly younger than those in Group II (mean age, 69.1 years) (P < 0.05).

CONCLUSIONS

The occurrence and development of ICC was closely related with the accumulation and cooperation of multiple genetic alterations. The genetic alterations of APC, MCC, DCC and Ki-ras-2 may play crucial roles in the early stage of development of ICC, and the genetic alterations of p53, OGG1 and RB1 may play important roles in accelerating advanced progression of ICC. The detection of the pedigree of genetic alterations in ICC may provide useful information for evaluating the state of tumor progression and clinic prognosis.