Functional loss of E-cadherin and cadherin-11 alleles on chromosome 16q22 in colonic cancer

Interleukin enhancer-binding factor 3 and HOXC8 co-activate cadherin 11 transcription to promote breast cancer cells proliferation and migration

Cadherin 11 (CDH11) expression is detected only in invasive breast cancer cells and aggressive breast cancer specimens. However, little is known about the molecular mechanisms of CDH11 transcriptional regulation. Here, we report that interleukin enhancer binding factor 3 (ILF3) interacts with Homeobox C8 (HOXC8) to activate CDH11 transcription in breast cancer cells. Using co-immunoprecipitation and mass spectrometry analyses, ILF3 is shown to interact with HOXC8 in breast cancer cells. We demonstrate that ILF3 binds to the CDH11 promoter on nucleotides –2982 ~ –2978 and –2602 ~ 2598 and interacts with HOXC8 to co-activate CDH11 transcription. We further show that ILF3 promotes proliferation and migration, at least partially, by facilitating CDH11 expression in breast cancer cells. Moreover, immunohistochemistry (IHC) shows that expression of CDH11, ILF3 and HOXC8 are all upregulated in breast cancer specimens compared to normal breast tissues. Importantly, the expression levels of CDH11, ILF3 and HOXC8 are elevated in the advanced stages of breast cancer, and high expression of CDH11, ILF3 and HOXC8 is associated with poor distant metastasis-free survival (DMFS) for breast cancer patients.

Reduced E-cadherin facilitates renal cell carcinoma progression by WNT/β-catenin signaling activation

Reduced expression of E-cadherin was observed in renal cell carcinoma (RCC). However, its potential clinical value and correlation with WNT/β-catenin signaling in RCC progression was still unclear. Immunohistochemical staining was performed in RCC tissue microarray to examine the expression status and prognosis value of E-cadherin and β-catenin. The potential role of E-cadherin in β-catenin translocation was analyzed with immunobloting assays. A significant negative correlation was observed between E-cadherin and β-catenin expression in RCC tissues. E-cadherin inhibits β-catenin translocation from membrane to cytoplasm in RCC tissues, which was an important step for WNT/β-catenin signaling. Reduced E-cadherin expression was associated with poor prognosis. More importantly, E-cadherin-/β-catenin+ was an independent detrimental factor for survival estimation of RCC patients. Reduced E-cadherin expression in RCC promoted cancer progression via WNT/β-catenin signaling pathway activation. E-cadherin/β-catenin provides a valuable prognosis marker for RCC, which may be an effective target for RCC therapy.

Allelic loss of chromosomes 8 and 19 in MENX-associated rat pheochromocytoma

Pheochromocytomas are neoplasias of neural crest origin that arise from the chromaffin cells of the adrenal medulla. Pheochromocytomas arise with complete penetrance in rats homozygous for a germ-line frameshift mutation of Cdkn1b, encoding the cell cycle inhibitor p27KIP1 (MENX syndrome). We performed a genome-wide scan for allelic imbalance comparing 20 rat pheochromocytoma DNAs with normal rat DNA to better understand the pathobiology of the tumors and to correlate the findings with human pheochromocytoma. We identified allelic imbalance (AI) at candidate regions on rat chromosomes 8 and 19. Interestingly, the regions often lost in rat tumors are syntenic to regions involved in human pheochromocytomas. Fluorescence in situ hybridization analysis further validated the AI data. Sdhd and Rassf1a were analyzed in detail as they map to regions of AI on chromosome 8 and their homologues are implicated in human pheochromocytoma: we found no genetic mutations nor decreased expression. We also analyzed additional candidate genes, that is, rat homologues of genes predisposing to human pheochromocytoma and known tumor-suppressor genes, but we found no AI. In contrast, we observed frequent overexpression of Cdkn2a and Cdkn2c, encoding the cell cycle inhibitors p16INK4a and p18INK4c, respectively. The relative small number of allelic changes we found in rat pheochromocytoma might be related to their nonmalignant status and losses at chromosomes 8 and 19 are events that precede malignancy. Because of the high concordance of affected loci between rat and human tumors, studies of the MENX-associated pheochromocytomas should facilitate the identification of novel candidate genes implicated in their human counterpart.

E-cadherin-160 C/A promoter polymorphism and risk of pancreatic carcinoma in Chinese population

Recent studies have implicated E-cadherin-160C/A single-nucleotide polymorphism (SNP) in susceptibility to and early onset of some cancers. We investigated the role of E-cadherin-160 C/A SNP in Chinese pancreatic carcinoma patients without dominant family history by genotyping 254 patients and 101 controls. The risk of cancer for CC genotype individuals was less than half that of AA individuals [odds ratio (OR) = 0.41; 95%confidence interval (95%CI) = 0.18-0.96]. Furthermore, patients with the CC and CA genotypes whose tumors were stages III (T(4)N(x)M(0)) and IV (T(x)N(x)M(1)) (OR = 0.38; 95%CI = 0.17-0.83), poorly differentiated (OR = 0.28; 95%CI = 0.09-0.84), and left-sided (OR = 0.45; 95%CI 0.21-0.98) were associated with significantly lower risk than AA patients. Young (60 years old or younger) AA patients had a 5-year lower mean age at onset than CC/CA patients (P = 0.02). Young male AA patients had worse disease-specific survival than CC/CA patients (P = 0.002). Thus, contrary to Canadians and Portuguese, the AA (rather than CC) genotype is associated with increased susceptibility and advanced pancreatic carcinoma in Chinese patients, suggesting a more complex relationship between the SNP and pancreatic carcinoma risk, possibly modulated by population differences.

One hit, two hits, three hits, more? Genomic changes in the development of retinoblastoma

The childhood eye cancer retinoblastoma is initiated by the loss of both alleles of the prototypic tumor suppressor gene, RB1. However, a large number of cytogenetic and comparative genomic hybridization (CGH) studies have shown that these M1 and M2 mutational events--although necessary for initiation--are not the only genomic changes in retinoblastoma. Some of these subsequent changes, which we have termed M3 to Mn, are likely crucial for tumor progression not only in retinoblastoma but also in other cancers. Moreover, genes showing genomic change in cancer are more stable markers and, therefore, possible therapeutic targets than genes simply differentially expressed. In this review, we provide the first comprehensive summary of the genomic evidence implicating gain of 1q, 2p, 6p, and 13q, and loss of 16q in retinoblastoma oncogenesis, including karyotype, CGH, and microarray CGH data. We discuss the search for candidate oncogenes and tumor suppressor genes within these regions, including the candidates (KIF14, MDM4, MYCN, E2F3, DEK, CDH11, and others), plus associations between genomic changes and clinical parameters. We also review studies of other regions of the retinoblastoma genome, the epigenetic changes of aberrant methylation of MGMT, RASSF1A, CASP8, and MLH1, and the roles microRNAs might play in this cancer. Although many candidate genes have yet to be functionally validated in retinoblastoma, work in this field lays out a molecular cytogenetic pathway of retinoblastoma development. Candidate cancer genes carry diagnostic, prognostic, and therapeutic implications beyond retinoblastoma.

Characterization of ZNF23, a KRAB-containing protein that is downregulated in human cancers and inhibits cell cycle progression

The Krupple-associated box-containing zinc-finger proteins (KRAB-ZFPs) make up one of the largest family of transcription factors. Several members of the KRAB-ZFPs modulate cell growth, survival and are implicated in malignant disorders. However, most members are not well characterized and their functions are largely unknown. Here we report that ZNF23, a member of KRAB-ZFPs, inhibits cell cycle progression. ZNF23 protein localized to the nucleus and was ubiquitously expressed in all tested normal tissues. However, the expression levels of ZNF23 protein were lost or greatly reduced in human cancer. Ectopic expression of ZNF23 led to enhancement of p27(kip-1) expression, growth inhibition and cell cycle arrest in G(1) phase. Downregulation of p27(kip-1) by siRNA against p27(kip-1) reversed growth inhibition induced by ZNF23. Furthermore, the growth-inhibitory effect of ZNF23 was p53-independent. Deletion analysis revealed that the effect of ZNF23 did not rely on its KRAB domain, but on the C-terminal zinc fingers. Thus, we have identified a new member of KRAB-ZNF superfamily with growth-inhibitory ability and its downregulation may contribute to carcinogenesis.

Chromosome 16 tumor-suppressor genes in breast cancer

Loss of heterozygosity on the long arm of chromosome 16 is one of the most frequent genetic events in breast cancer, suggesting the presence of one or more classic tumor-suppressor genes (TSGs). It has been shown that E-cadherin is the TSG on 16q in lobular tumors. In a search for the target genes in more frequently occurring low-grade nonlobular tumors, the smallest region of overlap (SRO) in this area of the genome has been exhaustively searched for. However, the results have demonstrated remarkable complexity, and so a clear consensus on identification of the SRO boundaries has not been reached. Several genes in the vicinity of these SROs have been scrutinized as putative TSGs in breast cancer, but so far, none has fulfilled the criteria for target genes. This review discusses the complexity of the 16q region and the different approaches that have been, are being, and will be used to detect the target genes in this area.

Frequent silencing of the candidate tumor suppressor PCDH20 by epigenetic mechanism in non-small-cell lung cancers

Protocadherins are a major subfamily of the cadherin superfamily, but little is known about their functions and intracellular signal transduction. We identified a homozygous loss of protocadherin 20 (PCDH20, 13q21.2) in the course of a program to screen a panel of non-small-cell lung cancer (NSCLC) cell lines (1 of 20 lines) for genomic copy number aberrations using an in-house array-based comparative genomic hybridization. PCDH20 mRNA was expressed in normal lung tissue but was not expressed in the majority of NSCLC cell lines without a homozygous deletion of this gene (10 of 19 lines, 52.6%). Expression of PCDH20 mRNA was restored in gene-silenced NSCLC cells after treatment with 5-aza 2'-deoxycytidine. The DNA methylation status of the PCDH20 CpG-rich region correlated inversely with the expression of the gene and a putative target region for methylation showed clear promoter activity in vitro. Methylation of this PCDH20 promoter was frequently observed in primary NSCLC tissues (32 of 59 tumors, 54.2%). Among our primary NSCLC cases, the methylated PCDH20 seemed to be associated with a shorter overall survival (P = 0.0140 and 0.0211 in all and stage I tumors, respectively; log-rank test), and a multivariate analysis showed that the PCDH20 methylation status was an independent prognosticator. Moreover, restoration of PCDH20 expression in NSCLC cells reduced cell numbers in colony formation and anchorage-independent assays. These results suggest that epigenetic silencing by hypermethylation of the CpG-rich promoter region of PCDH20 leads to loss of PCDH20 function, which may be a factor in the carcinogenesis of NSCLC.

Epigenetic silencing of the protocadherin family member PCDH-gamma-A11 in astrocytomas

In a microarray-based methylation analysis of astrocytomas [World Health Organization (WHO) grade II], we identified a CpG island within the first exon of the protocadherin-gamma subfamily A11 (PCDH-gamma-A11) gene that showed hypermethylation compared to normal brain tissue. Bisulfite sequencing and combined bisulfite restriction analysis (COBRA) was performed to screen low- and high-grade astrocytomas for the methylation status of this CpG island. Hypermethylation was detected in 30 of 34 (88%) astrocytomas (WHO grades II and III), 20 of 23 (87%) glioblastomas (WHO grade IV), and 8 of 8 (100%) glioma cell lines. There was a highly significant correlation (P = .00028) between PCDH-gamma-A11 hypermethylation and decreased transcription as determined by competitive reverse transcription polymerase chain reaction in WHO grades II and III astrocytomas. After treatment of glioma cell lines with a demethylating agent, transcription of PCDH-gamma-A11 was restored. In summary, we have identified PCDH-gamma-A11 as a new target silenced epigenetically in astrocytic gliomas. The inactivation of this cell-cell contact molecule might be involved in the invasive growth of astrocytoma cells into normal brain parenchyma.

Characterization of DNA polymorphisms in the E-cadherin gene (CDH1) promoter region

E-cadherin is a tumor suppressor involved in epithelial cell-cell interactions. Some of the nucleotide variation in the 5'-promoter region of the gene influences transcriptional efficiency. We investigated single nucleotide polymorphisms (SNPs) in the promoter-exon 1 region of the E-cadherin gene (CDH1) using fluorescence-based PCR-single-strand conformation polymorphism (PCR-SSCP) analysis. We detected four kinds of polymorphisms between nucleotides -516 and +12, numbering from the translation initiation site. SNPs were localized at -472G-->GA, -288T-->deltaT, -285C-->A, and -54G-->C. Variants -472GA and -285A were frequently found in controls, but the -288deltaT and -54C are rare variants. We examined the effects of these variants on transcription. The activity of promoters containing the variants -288deltaT, -285A, or -54C was lower than the activity of promoters with the major variants, as assayed by a luciferase reporter gene. Variants -472G and -472GA displayed the same promoter activity. The decreased transcriptional activity from variant promoters affects the expression of E-cadherin.

Mapping the chromosome 16 cadherin gene cluster to a minimal deleted region in ductal breast cancer

The cadherin family of cell adhesion molecules has been implicated in tumor metastasis and progression. Eight family members have been mapped to the long arm of chromosome 16. Using radiation hybrid mapping, we have located six of these genes within a cluster at 16q21-q22.1. In invasive lobular carcinoma of the breast frequent LOH and accompanying mutation affect the CDH1 gene, which is a member of this chromosome 16 gene cluster. CDH1 LOH also occurs in invasive ductal carcinoma, but in the absence of gene mutation. The proximity of other cadherin genes to 16q22.1 suggests that they may be affected by LOH in invasive ductal carcinomas. Using the mapping data, microsatellite markers were selected which span regions of chromosome 16 containing the cadherin genes. In breast cancer tissues, a high rate of allelic loss was found over the gene cluster region, with CDH1 being the most frequently lost marker. In invasive ductal carcinoma a minimal deleted region was identified within part of the chromosome 16 cadherin gene cluster. This provides strong evidence for the existence of a second 16q22 suppressor gene locus within the cadherin cluster.

Identification of cadherin-11 down-regulation as a common response of astrocytoma cells to transforming growth factor-alpha

Transforming growth factor-alpha (TGF-alpha) and its receptor are frequently co-expressed in high-grade astrocytomas, suggesting a role for TGF-alpha autocrine/paracrine loops in the malignant progression of astrocytomas. To identify genes that may be critical in mediating TGF-alpha impact on the malignant progression of astrocytomas, we have used cDNA arrays to investigate TGF-alpha effects on the gene expression profile of U-373 MG glioblastoma cells. We found that in these cells approximately 50% of the TGF-alpha regulated genes code for cell motility/invasion-related proteins. TGF-alpha action on the expression of four of these proteins, alpha-catenin, IQGAP1, RhoA, and cadherin-11, was further investigated by immunoblotting in four astrocytoma cell lines and in normal astrocytes. The results demonstrate that the effects of TGF-alpha on IQGAP1, alpha-catenin, and RhoA expression are cell-line dependent. On the other hand, under TGF-alpha treatment, cadherin-11 expression is consistently decreased in all astrocytoma cell lines tested but is increased in normal astrocytes. In addition, we found that cadherin-11 is consistently down-regulated in astrocytomas versus normal brain tissues. Altogether, these results suggest that the down-regulation of cadherin-11 is a frequent molecular event in the neoplastic transformation of astrocytes and that this down-regulation may be initiated and/or amplified by TGF-alpha autocrine/paracrine loops during tumor progression.

E-cadherin and adenomatous polyposis coli mutations are synergistic in intestinal tumor initiation in mice

BACKGROUND & AIMS

Inactivation of the adenomatous polyposis coli (APC) gene is observed at early stages of intestinal tumor formation, whereas loss of E-cadherin is usually associated with tumor progression. Because both proteins compete for the binding to beta-catenin, an essential component of the Wnt signaling pathway, reduction of E-cadherin levels in an Apc mouse model could influence both tumor initiation and progression. In addition, loss or haploinsufficiency of E-cadherin may affect tumorigenesis by altering its cell-adhesive and associated functions.

METHODS

Apc1638N mice were bred with animals carrying a targeted E-cadherin knockout mutation.

RESULTS

Double heterozygous animals showed a significant 9-fold and 5-fold increase of intestinal and gastric tumor numbers, respectively, compared with Apc1638N animals. The intestinal tumors of both groups showed no significant differences in grading and staging. Loss of heterozygosity analysis at the Apc and E-cadherin loci in both intestinal and gastric Apc(+/1638N)/E-cad(+/-) tumors revealed loss of the wild-type Apc allele in most cases, whereas the wild-type E-cadherin allele was always retained. This was supported by a positive, although reduced, staining for E-cadherin of intestinal tumor sections.

CONCLUSIONS

Introduction of the E-cadherin mutation in Apc1638N animals enhances Apc-driven tumor initiation without clearly affecting tumor progression.

Molecular analysis of E-cadherin and cadherin-11 in Wilms' tumours

Different studies of Wilms' tumours have demonstrated a loss of heterozygosity (LOH) of chromosome 16q ranging from 17 to 25%. In order to search for a potential tumour suppressor gene on 16q, we chose the calcium-dependent cell adhesion molecules E-cadherin and cadherin-11 as candidate genes, which are both located on the long arm of chromosome 16. E-cadherin is known to be expressed in epithelial structures, whereas cadherin-11 is supposed to be expressed in mesenchymal structures and developing epithelium, including renal tubules. For the present study, fresh frozen tissue from 30 Wilms' tumours and corresponding non-tumour tissues were analysed. Single nucleotide polymorphisms of the E-cadherin and cadherin-11 genes were chosen and analysed for allelic inactivation by polymerase chain reaction (PCR) amplification and sequence analysis. Loss of expression of one E-cadherin allele was seen in 10% (2/20) of the informative cases. Two out of 11 informative cases (18%) showed loss of expression of one cadherin-11 allele. No length alterations of either the E-cadherin or the cadherin-11 messenger RNAs were identified using reverse transcription PCR and agarose gel electrophoresis in tumour tissue. Sequencing of the entire E-cadherin coding region in seven cases showed the wild-type sequence. These data imply that E-cadherin and cadherin-11 are not likely to play typical tumour suppressor roles in Wilms' tumour. Interestingly, the E-cadherin immunohistochemistry showed a deviation from the normal reaction pattern in 50% of the cases, with 27% (8/30) showing an apical or cytoplasmic reaction and 23% (7/30) being completely negative. Northern blot analysis revealed that the overall expression of cadherin-11 is much stronger than that of E-cadherin. In several cases, the expression levels of the two genes were inversely correlated, suggesting the existence of a regulatory mechanism. Analysis of differential expression of the various cadherins and their subsequent signal transduction pathways might contribute to a better understanding of the complexity of Wilms' tumour formation.