Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations in APC, CTNNB1, AXIN1 or AXIN2 cause impairment in the beta-catenin degradation pathway and result in accumulation of beta-catenin in a wide range of human cancers. Accumulated beta-catenin then associates with Tcf/LEF transcription factors and transactivates their target genes. To uncover in detail the role of accumulated beta-catenin in colorectal carcinogenesis, we searched for genes involved in the beta-catenin/Tcf signaling pathway by cDNA microarray. We identified and characterized a human gene, SP5, that was down-regulated after depletion of beta-catenin by transduction of wild-type APC into SW480 cells. SP5 is a member of the Sp transcription factor family, which binds to the GC box or closely related sequences in promoters of many genes and control their expression. Reporter assays and an electromobility-shift assay revealed a DNA fragment between -285 and -279 in the 5' flanking region of this gene to be a target of the beta-catenin/Tcf4 complex. Our results indicate that SP5 is a novel direct down-stream target in the Wnt signaling pathway.
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PMID:Identification of SP5 as a downstream gene of the beta-catenin/Tcf pathway and its enhanced expression in human colon cancer. 1627 2

Colorectal carcinogenesis is initiated mainly by aberrant activation of the Wnt signaling pathway, caused by mutation of either APC or beta-catenin (CTNNB1) gene. Poly(ADP-ribose) polymerase-1 (PARP-1) is a highly conserved nuclear enzyme, which binds tightly to DNA and plays a role in DNA repair, recombination, proliferation and genomic stability. It has recently been shown that PARP-1 is a novel co-activator of TCF-4/beta-catenin-evoked gene transactivation and may play a role in colorectal carcinogenesis. The aim of this study was to examine the PARP-1 expression and determine whether it is correlated with the expression of beta-catenin and its target genes such as c-myc, cyclin D1 and matrix metalloproteinase (MMP)-7 in the early stage of sporadic colorectal carcinogenesis. Using the semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), 91 colorectal tumours, including 65 adenomas and 26 submucosal (pT1) cancers, were analysed for the expression of PARP-1, beta-catenin, c-myc, cyclin D1 and MMP-7. Immunohistochemical analysis of PARP-1 and beta-catenin was also performed. PARP-1 mRNA overexpression was detected in 64 (70.3%) of the 91 tumours. PARP-1 overexpression was significantly correlated with tumour size and histopathology. Overexpression of beta-catenin, c-myc, cyclin D1 and MMP-7 mRNA expression was observed in 39.6%, 78.0%, 83.5% and 72.5% of the 91 tumours, respectively. PARP-1 overexpression was correlated significantly with overexpression of beta-catenin, c-myc, cyclin D1 and MMP-7. Correlation of PARP-1 expression with beta-catenin overexpression was also demonstrated by immunohistochemistry. The results suggest that PARP-1, in conjunction with beta-catenin, c-myc, cyclin D1 and MMP-7, plays an important role in the early stage of colorectal carcinogenesis.
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PMID:Overexpression of poly(ADP-ribose) polymerase-1 (PARP-1) in the early stage of colorectal carcinogenesis. 1680 31

We evaluated alterations in p53, PIK3CA, PTEN, CTNNB1 (beta-catenin), MLH1, and BRAF among common histological subsets of epithelial ovarian tumors to characterize patterns of alterations of different molecular pathways. There were 12 clear cell, 26 endometrioid, and 51 serous carcinomas evaluated by direct DNA sequencing for mutations in p53, PIK3CA, PTEN, BRAF, and CTNNB1. Methylation-specific polymerase chain reaction (PCR) assessed MLH1 promoter methylation status. Quantitative PCR identified PIK3CA amplification in 22 EC/CC and 94 SC. p53 mutations were identified in 25 (49%) of 51 SC, 11 (42%) of 26 EC, and 1 (8.3%) of 12 CC neoplasms and were more common in grade 3 EC (P = .045) and advanced-stage EC/CC (P = .007). PIK3CA mutations were identified in 3 (25%) of 12 CC, 3 (12%) of 26 EC, and 0 of 51 SC. PTEN mutations were significantly more common in EC (8/26, 31%) compared with CC (0/12; P = .04) and SC (2/51, 4%; P = .002). CTNNB1 mutations were identified, 6 (23%) EC and no CC or SC (P = .008). Both PTEN and CTNNB1 mutations were more common in low-grade EC/CC, whereas PIK3CA mutations occurred only in grade 3 cancers. PTEN and PIK3CA mutations were more common in p53 wild-type tumors (P = .003). PIK3CA amplification occurred in fewer EC/CC (0/22) versus SC (19/94, 20%; P = 0.02) and were slightly more common in p53 wild-type compared with p53 mutant SC (P = .08). Of 26 EC, 22 (85%) had a mutation in one of the genes studied compared with 4 33% of 12 CC (P = .003). Women with EC/CC had significantly better overall survival (P = .0008), and this remained significant after accounting for stage (P=.04). Mutations in p53 or in PTEN/PIK3CA are alternative pathways in ovarian carcinogenesis. Activation of PIK3CA occurs by gene amplification in SC but via somatic mutation of PIK3CA or PTEN in EC and CC. PIK3CA mutations are associated with high-grade tumors, whereas PTEN and CTNNB1 mutations are associated with low-grade tumors. Mutations in p53, PIK3CA, PTEN, and CTNNB1 account for most EC tumors; most CC remain unexplained. EC/CC histology is a favorable prognostic factor.
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PMID:Alternate molecular genetic pathways in ovarian carcinomas of common histological types. 1725 89

In the Western world, endometrial carcinoma is the most common malignant tumour of the female genital tract and the fourth most common cancer in women after carcinomas of breast, colorectum, and lung. The annual incidence has been estimated at 10-20 per 100 000 women. In the United States, endometrial carcinoma accounts for approximately 6000 deaths per year. Two different clinicopathological subtypes are recognised: the oestrogen-related (type I, endometrioid) and the non-oestrogen related (type II, non-endometrioid). The clinicopathological differences are parallelled by specific genetic alterations, with type I showing microsatellite instability and mutations in PTEN, PIK3CA, K-Ras, and CTNNB1 (beta-catenin), and type II exhibiting p53 mutations and chromosomal instability. This article reviews the genetic changes of endometrial carcinogenesis in the light of morphological features of the tumours and their precursors.
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PMID:Endometrial carcinoma: pathology and genetics. 1736 24

Activation of Wnt signaling has been implicated in tumorigenesis, and epigenetic silencing of Wnt antagonist genes has been detected in various cancers. In the present study, we examined the expression and methylation of DICKKOPF (DKK) family genes in gastrointestinal cancer cell lines. We found that all known DKK genes were frequently silenced in colorectal cancer (CRC) cells (DKK1, 3/9, 33%; DKK2, 8/9, 89%; DKK3, 5/9, 56% and DKK4, 5/9, 56%), but not in normal colon mucosa. DKK1, -2 and -3 have 5' CpG islands, and show an inverse relation between expression and methylation. DKK methylation also was frequently observed in gastric cancer (GC) cell lines (DKK1, 6/16, 38%; DKK2, 15/16, 94% and DKK3, 10/16, 63%), but was seen less frequently in hepatocellular carcinoma and pancreatic cancer cell lines. DKKs also were frequently methylated in primary CRCs (DKK1, 7/58, 12%; DKK2, 45/58, 78% and DKK3, 12/58, 21%) and GCs (DKK1, 15/31, 48%; DKK2, 26/31, 84% and DKK3, 12/31, 39%). Against a background of CTNNB1 or APC mutations, Dickkopfs (Dkks) were less effective inhibitors of Wnt signaling than secreted frizzled-related proteins, though over-expression of Dkks suppressed colony formation of CRC cells with such mutations. Our results demonstrate that DKKs are frequent targets of epigenetic silencing in gastrointestinal tumors, and that loss of DKKs may facilitate tumorigenesis through beta-catenin/T-cell factor-independent mechanisms.
Carcinogenesis 2007 Dec
PMID:Frequent epigenetic inactivation of DICKKOPF family genes in human gastrointestinal tumors. 1767 36

We previously described striking molecular features including high frequency of membranous beta-catenin in subsets of familial colon cancers with as yet unknown predisposition. We hypothesized that such tumors might carry mutations in Wnt/beta-catenin target genes. Fibroblast growth factor 9 (FGF9) was an attractive target, as it maps to a common area of loss of heterozygosity (LOH) in colorectal carcinomas on 13q12.11. Here, we report, for the first time, the occurrence of FGF9 mutations in human cancers. We found a total of six distinct FGF9 mutations including one frameshift, four missense, and one nonsense, in 10 (six colorectal and four endometrial) out of 203 tumors and cell lines. The frameshift mutation was detected in five different tumors. Mapping of these mutations onto the crystal structure of FGF9 predicted that they should all lead to loss of function albeit through variable mechanisms. The p.R173K mutation should diminish ligand affinity for heparin/heparan sulfate, the p.V192M, p.D203G, and p.L188YfsX18 (FGF9(Delta205-208)) mutations should negatively impact ligand's interaction with receptor, while p.G84E and p.E142X (FGF9(Delta142-208)) mutations should interfere with ligand folding. Consistent with these structural predictions, the p.V192M, p.D203G, and p.L188YfsX18 (FGF9(Delta205-208)) mutations impaired the ability of ligand to activate mitogen-activated protein kinase (MAPK) cascade in cultured cells expressing FGF receptors. LOH was observed in seven out of nine FGF9 mutant tumors, supporting the predicted loss of function. Interestingly, eight out of 10 (80%) of the FGF9 mutant tumors showed normal membranous beta-catenin expression and the absence of mutation in the beta-catenin gene (CTNNB1). These data suggest that FGF9 plays a role in colorectal and endometrial carcinogenesis.
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PMID:Somatic FGF9 mutations in colorectal and endometrial carcinomas associated with membranous beta-catenin. 1816 46

Although mutation of APC or CTNNB1 (beta-catenin) is rare in breast cancer, activation of Wnt signalling is nonetheless thought to play an important role in breast tumorigenesis, and epigenetic silencing of Wnt antagonist genes, including the secreted frizzled-related protein (SFRP) and Dickkopf (DKK) families, has been observed in various tumours. In breast cancer, frequent methylation and silencing of SFRP1 was recently documented; however, altered expression of other Wnt antagonist genes is largely unknown. In the present study, we found frequent methylation of SFRP family genes in breast cancer cell lines (SFRP1, 7 out of 11, 64%; SFRP2, 11 out of 11, 100%; SFRP5, 10 out of 11, 91%) and primary breast tumours (SFRP1, 31 out of 78, 40%; SFRP2, 60 out of 78, 77%; SFRP5, 55 out of 78, 71%). We also observed methylation of DKK1, although less frequently, in cell lines (3 out of 11, 27%) and primary tumours (15 out of 78, 19%). Breast cancer cell lines express various Wnt ligands, and overexpression of SFRPs inhibited cancer cell growth. In addition, overexpression of a beta-catenin mutant and depletion of SFRP1 using small interfering RNA synergistically upregulated transcriptional activity of T-cell factor/lymphocyte enhancer factor. Our results confirm the frequent methylation and silencing of Wnt antagonist genes in breast cancer, and suggest that their loss of function contributes to activation of Wnt signalling in breast carcinogenesis.
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PMID:Frequent epigenetic inactivation of Wnt antagonist genes in breast cancer. 1828 16

The Wnt pathway is involved in carcinogenesis and three regulatory genes of the Wnt pathway, APC (adenomatous polyposis coli), beta-catenin and Axin are frequently mutated in some primary human cancers. This study was conducted to clarify the relation of beta-catenin accumulation and the mutation of the CTNNB1 (beta-catenin) gene with the mutation of APC gene in the process of development of odontogenic tumors including ameloblastoma and odontogenic carcinoma (OC). beta-Catenin accumulation was examined by immunohistochemistry in formalin-fixed, paraffin-embedded samples of six ameloblastomas and eight OCs. We also performed a mutation analysis of CTNNB1 and APC to examine the cause of beta-catenin accumulation. All ameloblastoma cases and six out of eight (75%) OC cases exhibited beta-catenin accumulation in the nucleus. CTNNB1 mutation was only found in one OC case, whereas three of six (50%) ameloblastoma cases and two out of eight (25%) OC cases had APC mutations within the mutational cluster region. Our findings suggest that aberrant beta-catenin expression and APC missense mutation may play an important role for the pathogenesis of epithelial odontogenic tumors.
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PMID:Aberrant beta-catenin expression and adenomatous polyposis coli gene mutation in ameloblastoma and odontogenic carcinoma. 1848 30

Small intestinal adenocarcinoma is rare and its molecular pathogenesis is incompletely understood. Stabilization of beta-catenin, a mediator of wnt/wingless signalling, can be detected in 50% of sporadic carcinomas but, in contrast to colorectal cancer, this finding can not be explained by the inactivation of adenomatous polyposis coli (APC). In order to elucidate the molecular background of beta-catenin stabilization in small intestinal adenocarcinoma, we investigated 20 non-familial adenomatous polyposis coli (FAP)-associated tumours, including five microsatellite-unstable carcinomas for beta-catenin alterations, by immunohistochemistry, western blot analysis and sequence analysis on the RNA and DNA levels. Nuclear accumulation of beta-catenin was found in 50% of carcinomas. In 30%, nuclear stabilization was restricted to tumour cells at the invasion front, while 20% of tumours displayed intense homogeneous nuclear stabilization throughout all areas. Large deletions and insertions in the beta-catenin gene (CTNNB1) resulting in a partial or complete in-frame loss of exons 3 and 4 on the RNA-transcript level were found in the latter, exclusively microsatellite-stable carcinomas. The mutations resulted in the stabilization of aberrant beta-catenin lacking large parts of N-terminal protein domains. No point mutations in CTNNB1 were observed. Our data show that large intragenic CTNNB1 mutations stabilize beta-catenin in small intestinal adenocarcinomas and influence the subcellular distribution of the protein. In contrast to colon carcinomas, neither APC nor CTNNB1 point mutations seem to play a significant role in carcinogenesis, indicating divergent mechanisms of wnt/wingless control in the small and the large intestine.
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PMID:Large-scale N-terminal deletions but not point mutations stabilize beta-catenin in small bowel carcinomas, suggesting divergent molecular pathways of small and large intestinal carcinogenesis. 1849 52

Although mutations of APC, CTNNB1 (beta-catenin) and AXIN1 are rare in oral squamous cell carcinoma (OSCC), activation of the Wnt signaling pathway is thought to play an important role in oral carcinogenesis. In the present study, we examined the relationship between Wnt signaling and epigenetic alteration of the secreted frizzled-related protein (SFRP) genes in OSCC. We frequently detected loss of membrane localization of beta-catenin and its cytoplasmic or nuclear accumulation in OSCC cell lines, although these cell lines showed no APC or CTNNB1 (beta-catenin) mutations and no methylation of CDH1 (E-cadherin). By contrast, we frequently detected methylation of SFRP1 (7/17, 41%) SFRP2 (16/17, 94%) and SFRP5 (14/17, 82%) in a panel of OSCC cell lines, as well as in specimens of primary tumors collected from 44 OSCC patients (SFRP1, 10/42, 24%; SFRP2, 16/44, 36%; SFRP5, 7/43, 16%). We also observed that OSCC cell lines express various Wnt ligands, and that ectopic expression of SFRPs inhibited cancer cell proliferation. Our results confirm the frequent methylation and silencing of SFRP genes in OSCC, and suggest that their loss of function contributes to activation of Wnt signaling that leads to cell proliferation during oral carcinogenesis.
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PMID:Epigenetic inactivation of SFRP genes in oral squamous cell carcinoma. 1849 87


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