Molecular nature of chromosome 5q loss in colorectal tumors and desmoids from patients with familial adenomatous polyposis

MIR143HG promotes methylation of transcription factor HOXB7 promoter by recruiting methyltransferase DNMT1 to prevent the progression of colon cancer

In recent years, accumulating evidence has demonstrated the role of long noncoding RNAs (lncRNAs) in colon cancer. We aim to investigate the role of MIR143HG, also known as CARMN (Cardiac mesoderm enhancer-associated noncoding RNA) in colon cancer and explore the related mechanisms. An RNAseq data analysis was performed to screen differentially expressed lncRNAs associated with colon cancer. Next, MIR143HG expression was quantified in colon cancer cells. Moreover, the contributory roles of MIR143HG in the progression of colon cancer with the involvement of DNMT1 and HOXB7 (Homeobox B7) were evaluated after restored MIR143HG or depleted HOXB7. Finally, the effects of MIR143HG were investigated in vivo by measuring tumor formation in nude mice. High-throughput transcriptome sequencing was employed to validate the specific mechanisms by which MIR143HG and HOXB7 affect tumor growth in vivo. MIR143HG was found to be poorly expressed, while HOXB7 was highly expressed in colon cancer. MIR143HG could promote HOXB7 methylation by recruiting DNMT1 to reduce HOXB7 expression. Upregulation of MIR143HG or downregulation of HOXB7 inhibited cell proliferation, invasion and migration and facilitated apoptosis in colon cancer cells so as to delay the progression of colon cancer. The same trend was identified in vivo. Our study provides evidence that restoration of MIR143HG suppressed the progression of colon cancer via downregulation of HOXB7 through DNMT1-mediated HOXB7 promoter methylation. Thus, MIR143HG may be a potential candidate for the treatment of colon cancer.

Advances in colorectal cancer genomics and transcriptomics drive early detection and prevention

Colorectal carcinoma (CRC) is a high incidence cancer and leading cause of cancer mortality worldwide. The advances in genomics and transcriptomics in the past decades have improved the detection and prevention of CRC in familial CRC syndromes. Nevertheless, the ultimate goal of personalized medicine for sporadic CRC is still not within reach due no less to the difficulty in integrating population disparity and clinical data to combat what essentially is a very heterogenous disease. This minireview highlights the achievement of the past decades and present possible direction in the hope of early detection and metastasis prevention for reducing CRC-associated morbidity and mortality.

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.

Inducible Nitric Oxide Synthase in the Carcinogenesis of Gastrointestinal Cancers

SIGNIFICANCE

Gastrointestinal (GI) cancer taken together constitutes one of the most common cancers worldwide with a broad range of etiological mechanisms. In this review, we have examined the impact of nitric oxide (NO) on the etiology of colon, colorectal, gastric, esophageal, and liver cancers. Recent Advances: Despite differences in etiology, initiation, and progression, chronic inflammation has been shown to be a common element within these cancers showing interactions of numerous pathways. NO generated at the inflammatory site contributes to the initiation and progression of disease. The amount of NO generated, time, and site vary and are an important determinant of the biological effects initiated. Among the nitric oxide synthase enzymes, the inducible isoform has the most diverse range, participating in numerous carcinogenic processes. There is emerging evidence showing that inducible nitric oxide synthase (NOS2) plays a central role in the process of tumor initiation and/or development.

CRITICAL ISSUES

Redox inflammation through NOS2 and cyclooxygenase-2 participates in driving the mechanisms of initiation and progression in GI cancers.

FUTURE DIRECTIONS

Understanding the underlying mechanism involved in NOS2 activation can provide new insights into important prevention and treatment strategies. Antioxid. Redox Signal. 26, 1059-1077.

Molecular genetics of supernumerary tooth formation

Despite advances in the knowledge of tooth morphogenesis and differentiation, relatively little is known about the aetiology and molecular mechanisms underlying supernumerary tooth formation. A small number of supernumerary teeth may be a common developmental dental anomaly, while multiple supernumerary teeth usually have a genetic component and they are sometimes thought to represent a partial third dentition in humans. Mice, which are commonly used for studying tooth development, only exhibit one dentition, with very few mouse models exhibiting supernumerary teeth similar to those in humans. Inactivation of Apc or forced activation of Wnt/β(catenin signalling results in multiple supernumerary tooth formation in both humans and in mice, but the key genes in these pathways are not very clear. Analysis of other model systems with continuous tooth replacement or secondary tooth formation, such as fish, snake, lizard, and ferret, is providing insights into the molecular and cellular mechanisms underlying succesional tooth development, and will assist in the studies on supernumerary tooth formation in humans. This information, together with the advances in stem cell biology and tissue engineering, will pave ways for the tooth regeneration and tooth bioengineering.

Wnt signaling and colon carcinogenesis: beyond APC

Activation of the Wnt signaling pathway via mutation of the adenomatous polyposis coli gene (APC) is a critical event in the development of colon cancer. For colon carcinogenesis, however, constitutive signaling through the canonical Wnt pathway is not a singular event. Here we review how canonical Wnt signaling is modulated by intracellular LEF/TCF composition and location, the action of different Wnt ligands, and the secretion of Wnt inhibitory molecules. We also review the contributions of non-canonical Wnt signaling and other distinct pathways in the tumor micro environment that cross-talk to the canonical Wnt pathway and thereby influence colon cancer progression. These ‘non-APC’ aspects of Wnt signaling are considered in relation to the development of potential agents for the treatment of patients with colon cancer. Regulatory pathways that influence Wnt signaling highlight how it might be possible to design therapies that target a network of signals beyond that of APC and β-catenin.

Expression profiling of micro-RNAs in human esophageal squamous cell carcinoma using RT-PCR

To develop novel therapeutic and diagnostic methods for esophageal cancer, it is important to understand the precise biological mechanism. Micro-RNAs (miRNAs) seem to be crucial factors in diverse regulation pathways. In this study, we analyzed the expression of mature miRNAs in esophageal squamous cell carcinoma (ESCC). The expression of 73 miRNAs was quantified by qRT-PCR in 30 primary ESCC specimens. We examined the correlation between miRNA expressions and the clinicopathological factors and prognosis of ESCC. The Kaplan-Meier survival curves showed that the high expression levels of 6 of the 72 miRNAs correlated with significantly lower patient survival rates. The overexpression of miR-129 was identified as a significant and independent prognostic factor (P = 0.031) in surgically treated ESCC patients. The hazard ratio for the prediction of early death was 18.11 for high versus low expression levels of miR-129. Similar results were obtained from an analysis performed on an additional 19 patients (test cohort) (P = 0.0057, for training cohort; P = 0.011, for test cohort; log-rank test). This experiment supports the notion that the high miR-129 expression levels, as observed in this study, might play a important role in the development of esophageal cancer.

Oral and maxillofacial manifestations of Gardner's syndrome associated with growth hormone deficiency: case report and literature review

Gardner's syndrome (GS) is a hereditary disorder inherited as autosomal dominant with complete penetrance and variable expression. GS is a variant of familial adenomatous polyposis characterized by extracolonic manifestations including osteomas, dental anomalies, and epidermoid cysts. The association between GS and endocrine abnormalities has been well documented but a direct pituitary involvement has never been reported. We present a case of oral and maxillofacial manifestations in an adult patient affected by GS associated with growth hormone deficiency, a hitherto unreported association. The possible pathogenic mechanisms are discussed.

Identification of a novel tumor suppressor gene p34 on human chromosome 6q25.1

In this study, we observed loss of heterozygosity (LOH) in human chromosomal fragment 6q25.1 in sporadic lung cancer patients. LOH was observed in 65% of the 26 lung tumors examined and was narrowed down to a 2.2-Mb region. Single-nucleotide polymorphism (SNP) analysis of genes located within this region identified a candidate gene, termed p34. This gene, also designated as ZC3H12D, C6orf95, FLJ46041, or dJ281H8.1, carries an A/G nonsynonymous SNP at codon 106, which alters the amino acid from lysine to arginine. Nearly 73% of heterozygous lung cancer tissues with LOH and the A/G SNP also exhibited loss of the A allele. In vitro clonogenic and in vivo nude mouse studies showed that overexpression of the A allele exerts tumor suppressor function compared with the G allele. p34 is located within a recently mapped human lung cancer susceptibility locus, and association of the p34 A/G SNP was tested among these families. No significant association between the less frequent G allele and lung cancer susceptibility was found. Our results suggest that p34 may be a novel tumor suppressor gene involved in sporadic lung cancer but it seems not to be the candidate familial lung cancer susceptibility gene linked to chromosomal region 6q23-25.

Spontaneous isolated mesenteric fibromatosis: sonographic and computed tomographic findings with pathologic correlation

Eight cases of spontaneous isolated mesenteric fibromatosis (SIMF) were retrospectively reviewed. Clinical presentations included palpable abdominal mass (n = 6), abdominal pain (n = 4), gastrointestinal bleeding (n = 2) and acute abdomen (n = 1). On sonography and computed tomography (CT), eight SIMFs (size range 3 to 24 cm, mean 14.8 cm) were categorized into four morphologic patterns: well-defined inhomogeneous, well-defined homogeneous, well-defined cystic or infiltrative mesenteric mass patterns. Well-defined inhomogeneous SIMF (n = 3) was correlated with the histopathologic finding of bundles of fibroblasts with unevenly intermingled hyaline and/or myxoid degeneration areas, whereas well-defined homogeneous SIMF (n = 2) showed scarce degenerative changes. Well-defined cystic SIMF (n = 2) were ascribed to the presence of large areas of myxoid and cystic degenerations. One SIMF presented as an infiltrative mesenteric mass and the patient died 10 months after diagnosis. Both cases of cystic SIMFs showed tumor recurrences and one patient died after 84 months. The other five patients were cured by radical tumor resection. In summary, sonography, similar to CT, is also useful for evaluating SIMF with protean morphologic features, ascribing to the underlying histopathologic changes with varied degrees of hyaline, myxoid or cystic degenerations.

Canonical Wnt signaling in differentiated osteoblasts controls osteoclast differentiation

Inactivation of beta-catenin in mesenchymal progenitors prevents osteoblast differentiation; inactivation of Lrp5, a gene encoding a likely Wnt coreceptor, results in low bone mass (osteopenia) by decreasing bone formation. These observations indicate that Wnt signaling controls osteoblast differentiation and suggest that it may regulate bone formation in differentiated osteoblasts. Here, we study later events and find that stabilization of beta-catenin in differentiated osteoblasts results in high bone mass, while its deletion from differentiated osteoblasts leads to osteopenia. Surprisingly, histological analysis showed that these mutations primarily affect bone resorption rather than bone formation. Cellular and molecular studies showed that beta-catenin together with TCF proteins regulates osteoblast expression of Osteoprotegerin, a major inhibitor of osteoclast differentiation. These findings demonstrate that beta-catenin, and presumably Wnt signaling, promote the ability of differentiated osteoblasts to inhibit osteoclast differentiation; thus, they broaden our knowledge of the functions Wnt proteins have at various stages of skeletogenesis.

Refinement of heterozygosity loss on chromosome 5p15 in sporadic colorectal cancer

AIM: To refine the loss of heterozygosity on chromosome 5p15 and to identify the new tumor suppressor gene (s) in colorectal tumorigenesis.

METHODS: Sixteen polymorphic microsatellite markers were analyzed on chromosome 5 and another 6 markers were applied on chromosome 5p15 in 83 cases of colorectal and normal DNA by PCR. PCR products were electrophoresed on an ABI 377 DNA sequencer. Genescan 3.1 and Genotype 2.1 software were used for LOH scanning and analysis.

RESULTS: We observed 2 distinct regions of frequent allelic deletions on Chromosome 5, at D5S416 on 5p15 and D5S428-D5S410 on 5q. Another 6 polymorphric microsatellite markers were applied to 5p15 and the minimal region of frequent loss of heterozygosity was established on 5p15 spanning the D5S416 locus.

CONCLUSION: Through our detailed deletion mapping studies, we have found a critical and precise location of 5p deletions, 5p15.2-5p15.3, which must contain one or more unknown tumor suppressor gene (s) of colorectal cancer.

Spectrum of molecular changes during hepatocarcinogenesis induced by DEN and other chemicals in Fisher 344 male rats [Mechanisms of Ageing and Development 123 (2002) 1665-1680]

Unlike other tissues such as breast, colon and renal cell carcinoma, it is not an easy task to single out any representative oncogene or tumor suppressor genes in the development of hepatocellular carcinoma (HCC), which play a pivotal role. To investigate putatively altered main pathways in HCC, F344 male rats were treated with a single injection of N-nitrosodiethylamine (DEN), followed by either twice/week injections of nodularin for 10 weeks or thioacetamide (TAA) in drinking water for 39 weeks. p53 expression was dramatic in both hepatocytes and mesenchymal cells after a single injection of DEN, however, PCR-SSCP assay could not detect any p53 mutation during the development of hepatocellular adenoma (HCA). The data indicate that wtp53 response was mostly for removal of damaged cells during the initiation of carcinogenesis. When treated with DEN-TAA, induction of gankyrin expression during hepatic fibrosis preceded the loss of pRB protein, accompanied with significant expressions of G1phase cyclins and CDKs. Moreover, p16(INK4A) exon 1 was hypermethylated during the development of poorly differentiated HCCs. These changes would result in complete inactivation of the pRB regulatory pathway during hepatocarcinogenesis. Induction of TGF-beta1 expression with loss of its receptor expression occurred rapidly in the altered hepatocytes by DEN-nodularin treatment.

CONCLUSION

Therefore, escape from TGF-beta1 induced apoptosis and severe degradation of pRB protein during the early stage of carcinogenesis can perform a symphony to proliferate and to transform the altered hepatocytes to tumor cells. Inactivation of p16(INK4A) and p53 genes at the later stage of carcinogenesis would endow HCC with malignancy, which is highly resistant to any therapeutic trials.

Spectrum of molecular changes during hepatocarcinogenesis induced by DEN and other chemicals in Fischer 344 male rats

Unlike other tissues such as breast, colon and renal cell carcinoma, it is not an easy task to single out any representative oncogene or tumor suppressor genes in the development of hepatocellular carcinoma (HCC), which play a pivotal role. To investigate putatively altered main pathways in HCC, F344 male rats were treated with a single injection of N-nitrosodiethylamine (DEN), followed by either twice/week injections of nodularin for 10 weeks or thioacetamide (TAA) in drinking water for 39 weeks. p53 expression was dramatic in both hepatocytes and mesenchymal cells after a single injection of DEN, however, PCR-SSCP assay could not detect any p53 mutation during the development of hepatocellular adenoma. The data indicate that wtp53 response was mostly for removal of damaged cells during the initiation of carcinogenesis. When treated with DEN-TAA, induction of gankyrin expression during hepatic fibrosis preceded the loss of pRB protein, accompanied with significant expressions of G1 phase cyclins and CDKs. Moreover, p16(INK4A) exon 1 was hypermethylated during the development of poorly differentiated HCCs. These changes would result in complete inactivation of the pRB regulatory pathway during hepatocarcinogenesis. Induction of TGF-beta1 expression with loss of its receptor expression occurred rapidly in the altered hepatocytes by DEN-nodularin treatment.

CONCLUSION

Therefore, escape from TGF-beta1 induced apoptosis and severe degradation of pRB protein during the early stage of carcinogenesis can perform a symphony to proliferate and to transform the altered hepatocytes to tumor cells. Inactivation of p16(INK4A) and p53 genes at the later stage of carcinogenesis would endow HCC with malignancy, which is highly resistant to any therapeutic trials.

Nuchal-type fibroma in two related patients with Gardner's syndrome

Nuchal-type fibroma is a distinct subcutaneous and dermal fibrous tissue proliferation that has been previously definitely identified in one patient with Gardner's syndrome and has been possibly present in two others. Gardner's syndrome is an autosomal-dominant condition with variable expressivity that comprises epidermoid cysts, fibrous tumors, osteomas, intestinal polyposis, as well as other findings. We report two cases of nuchal-type fibroma presenting in a 13-year-old boy in the right upper back and in his 60-year-old grandfather in the upper chest at the posterior axillary line. Both individuals carried a diagnosis of Gardner's syndrome and neither of them had diabetes. Although the boy has as of now only presented with cutaneous manifestations of Gardner's syndrome, his grandfather has exhibited both cutaneous and intestinal evidence of this syndrome. In addition, the boy's mother and her sister have documented Gardner's syndrome. Light microscopic findings of nuchal-type fibroma from both patients include paucicellular, haphazardly arranged collagen bundles with entrapped adipose tissue. A marked diminution of elastic fibers was noted with Van-Gieson stains. The lesions were diffusely positive for CD34 and contained a few factor XIIIa-positive cells. Electron microscopic analysis revealed no differences between the collagen comprising the nuchal-type fibroma as compared with control dermal collagen obtained from skin away from the tumor. These cases strengthen the view that there is an association between nuchal-type fibroma and Gardner's syndrome.

Chromosomal imbalances in small cell carcinomas of the urinary bladder

Small cell carcinomas (SCCs) represent a rare histological subtype of urinary bladder cancer. Little is known abut the genetic alterations in these tumours. To identify chromosomal aberrations that are typically present in SCC of the urinary bladder, ten tumours were analysed by comparative genomic hybridization (CGH). CGH allows screening for all relative DNA copy number gains and losses present in a tumour. SCCs of the bladder were characterized by a high number of genomic alterations (mean: 11.3 per tumour). Deletions were most frequent at 10q (7 of 10 tumours deleted), 4q, 5q (5/10 each), and 13q (4/10). These regions may carry tumour suppressor genes with relevance for this particular tumour type. Gains of DNA sequences were most prevalent at 8q (5/10), 5p, 6p, and 20q (4/10 each). High level amplifications were found at 1p22-32, 3q26.3, 8q24, and 12q14-21. These loci may pinpoint the localization of oncogenes with relevance for small cell bladder cancer. The analysis of one tumour having areas of both SCC and transitional cell carcinoma strongly suggests that SCC can develop from TCC through the acquisition of additional genetic alterations.

Identification and progression of a desmoid precursor lesion in patients with familial adenomatous polyposis

BACKGROUND

Desmoid tumours occur in about 10 per cent of patients with familial adenomatous polyposis (FAP), and are an important cause of morbidity and death. The natural history of desmoids was investigated by documenting prospectively the prevalence and progression of possible precursor lesions.

METHODS

A group of patients with FAP and controls were examined at laparotomy. Another group, with FAP and no clinical evidence of desmoid, and a group of controls, underwent abdominopelvic computed tomography.

RESULTS

At laparotomy 13 of 42 patients with FAP had fibromatous mesenteric plaques; seven of these had not had surgery. Seven had more extensive mesenteric fibromatosis and had undergone significantly more laparotomies than the rest. Of 103 patients scanned, two had desmoid tumours and 22 (21 per cent) had mesenteric fibromatosis. On follow-up both desmoid tumours grew rapidly; mesenteric fibromatosis was unchanged in eight and resolved in four of the 12 patients rescanned.

CONCLUSION

A model of desmoid tumour development is suggested, analogous to the adenoma-carcinoma sequence, in which a less benign phenotype emerges as molecular genetic abnormalities accumulate: mesenteric plaque-like desmoid precursor lesions arise in many patients with FAP before surgery as a result of abnormal fibroblast function; some, perhaps stimulated by surgery, progress to mesenteric fibromatosis; these in turn can give rise to desmoid tumours.

Adrenocortical tumor in a patient with familial adenomatous polyposis: a case associated with a complete inactivating mutation of the APC gene and unusual histological features

Familial adenomatous polyposis (FAP) is an autosomal dominant hereditary disorder caused by a germline inactivating mutation of the adenomatous polyposis coli (APC) gene. Patients with FAP sometimes develop various extracolonic manifestations including adrenocortical neoplasms. We present a 14-year-old boy with FAP who had an adrenocortical tumor with atypical histopathologic features, ie, sex-cord-like differentiation. Immunohistochemical studies of adrenal 4 binding protein (Ad4BP) and steroidogenic enzymes showed the capacity of these tumor cells to produce steroids. Genetic analysis of the tumor disclosed a two-hit mutation in APC: a germline 5-base pair deletion accompanied by a loss of the normal allele. Because there were no reports of genetic alterations in adrenocortical tumors developed in FAP patients, we examined 10 sporadic adrenal tumors (four carcinomas and six adenomas) for mutations in APC. However, no mutations were found in these 10 sporadic adrenal tumors. These results suggest that mutation of APC is also responsible for some fraction of the adrenocortical tumors: the tumor in this case is included.

Desmoid tumor is a clonal cellular proliferation: PCR amplification of HUMARA for analysis of patterns of X-chromosome inactivation

Desmoid tumor is a locally aggressive, nonmetastasizing soft tissue tumor. Whether desmoid tumor is a truly neoplastic cellular proliferative process or, alternatively, an unchecked reactive process has been a subject of debate. In order to determine whether desmoid tumor is composed of a clonal cell population as opposed to being a polyclonal reactive process, analysis of patterns of X-chromosome inactivation was performed. Hematoxylin and eosin stained sections of paraffin-embedded, formalin-fixed tissues were microdissected to obtain both lesional and normal control samples, and the genomic DNAs were extracted by proteinase K digestion. Following treatment with methylation sensitive restriction endonuclease (Hha I or Hpa II), the genomic DNAs were amplified by polymerase chain reaction (PCR), using nested primers targeted to a highly polymorphic short tandem repeat (STR) of the human androgen receptor (HUMARA). In eight of 12 cases, PCR amplification of the genomic DNAs was successful, and all eight of the amplified cases were heterozygous in the size of the HUMARA target. The remaining cases could not be studied because of failure to amplify DNA. Following digestion with HhaI or Hpa II, uniform patterns of X-chromosome inactivation were found in all eight desmoid tumors, whereas normal control tissue remained heterozygous. These results confirm a clonal composition of the tumors. The demonstration of clonality in the tumors in all eight informative cases indicates that desmoid tumor is a true neoplastic process, not an unchecked polyclonal reactive process.

Desmoids in familial adenomatous polyposis

Clinical desmoid disease affect approximately 10 per cent of patients with familial adenomatous polyposis (FAP); the subclinical rate is unknown. Desmoids are probably neoplastic rather than regenerative in origin and may arise in association with germline or somatic mutations at or beyond codon 1444 of the APC gene. Intra-abdominal desmoids behave unpredictably but are an important cause of death in those with FAP. Signal intensity on magnetic resonance imaging reflects tumour cellularity, which in part determines progression, and this may help management. Surgical treatment of advanced desmoids is hazardous, but medical treatments have limited success. Chemotherapy with doxorubicin and dacarbazine is currently under evaluation.

Tumour suppressor genes and colorectal neoplasia

Two distinct gene classes have been implicated in colorectal carcinogenesis. Tumour promoter genes (oncogenes, dominant oncogenes) produce an excessive positive stimulus to cell proliferation. The ras family of oncogenes are an example. Acquired mutations of the c-k-ras gene are commonly found in colonic adenomas and carcinomas. Tumour suppressor genes (anti-oncogenes, recessive oncogenes) normally constrain or regulate cell proliferation. Loss of this function through gene deletion or mutation is oncogenic. Inherited tumour suppressor gene mutations have now been identified in several of the familial cancer syndromes. Acquired tumour suppressor gene mutations are found in both sporadic and hereditary cancers. Together with the tumour promoter genes they provide the genetic basis for the cellular changes occurring during carcinogenesis. The retinoblastoma gene was the first human tumour suppressor gene to be characterized and exemplifies the class. More recently, linkage studies in the hereditary cancer syndromes and the detection of specific deletions in sporadic tumours have helped to identify several new tumour suppressor genes. At least four of these (MCC, APC, p53 and DCC) apparently contribute to sporadic colorectal carcinogenesis. Germ line APC mutations produce the inherited colorectal cancer syndrome familial adenomatous polyposis (FAP). Detection of these mutations using linked markers has already found clinical application in the screening of families with this disease. In the future, genetic diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) and the recognition of those genetically susceptible to sporadic colorectal cancer may become possible. At the same time, as our understanding of the genes involved improves, new avenues for treatment and prevention of colorectal cancer may emerge.

Colon cancer genetics

The terms "hereditary," "sporadic," and "familial" colorectal cancer (CRC) suggest a knowledge of causation; however, current understanding of CRC does not permit categorization of differing CRC risks in accord with their cause per se. Despite these serious shortcomings, these terms are defined operationally on the basis of a family history of cancer, and when available, additional phenotypic information. The sporadic type occurs in the absence of a family history of CRC in a first-degree relative. The familial type occurs when at least one first-degree relative has CRC. Both these categories require the exclusion of hereditary CRC. In the case of hereditary CRC, this type is defined as a family history of CRC occurring in a pattern that indicates autosomal-dominant inheritance, which also may involve certain phenotypic signs (depending on the specific disorder, i.e., florid adenomatous polyps, benign and malignant extracolonic lesions, cancer of unusually early onset, and multiple primary cancer, particularly synchronous and metachronous CRC). Although this operational classification does not produce etiologically homogeneous groups, it is believed to have pragmatic utility with respect to planning targeted surveillance and management strategies. Because of the distinctive natural history of CRC in hereditary syndromes, it is of paramount clinical importance to identify hereditary CRC when it does occur. Even in patients with no evidence of hereditary CRC syndrome, their family history may be second only to age in determining the best CRC screening program for those who are asymptomatic. In an attempt to provide a perspective on the clinical evaluation of CRC risk, research was reviewed on pathologic features and biomarkers that may be related to CRC causes, especially the genetic basis of CRC susceptibility. The long-term objective of studies on the genetic epidemiology of CRC is primary and secondary prevention through development of targeted management and surveillance recommendations (based on an understanding of CRC causation) that is relevant to hereditary, familial, and sporadic CRC.

Loss of normal allele of the APC gene in an adrenocortical carcinoma from a patient with familial adenomatous polyposis

Endocrine neoplasms have been reported occasionally in patients with familial adenomatous polyposis (FAP). An adrenocorotical carcinoma was studied in a patient with a family history of FAP. Loss of heterozygosity (LOH) in the region close to the adenomatous polyposis coli (APC) gene was detected in this carcinoma, and evidence was obtained that there was a loss of the normal allele of the APC gene. This is the first demonstration of LOH at the APC locus in adrenocortical tumors. The present results and our previous data on LOH in a recurring desmoid tumor suggest that the heterozygous mutant/wild-type condition of the APC gene may give rise to benign tumors, and that functional loss of this gene leads to development of tumors not only in the colon but also in other various parts of the body in FAP patients.

Clonal chromosomal abnormalities in desmoid tumors. Implications for histopathogenesis

Desmoid tumors (aggressive fibromatosis) are regarded as lesions of uncertain histopathogenesis. Cytogenetic analyses of 26 desmoid tumor specimens from abdominal or extraabdominal sites of 22 patients with or without Gardner's syndrome (GS) showed clonal karyotypic abnormalities in 7 cases, random abnormalities in 14 cases, and striking telomeric fusion in 5 cases. Loss of chromosome Y, a reported feature of fibromatosis in penile and palmar locations, was detected as a clonal aberration in two patients. Additionally, involvement of 5q was observed in six patients, two of whom had GS. Clonal interstitial deletions of 5q were observed in three patients, one with and two without GS. These findings confirm a clonal and probable neoplastic origin for desmoid tumor and suggest that abnormalities of the Y chromosome and 5q may be important in the genesis of this neoplasm.

Chromosome changes in desmoid tumors developed in patients with familial adenomatous polyposis

Chromosome analyses were performed on benign desmoid tumors obtained from two female patients with familial adenomatous polyposis (FAP), one of whom was diagnosed as having Gardner syndrome (GS). The modal chromosome number was 46 in both specimens, and detailed Q-banding analysis in Case 1 (GS) revealed a clonal abnormality of an interstitial deletion of the long arm of chromosome 5, del(5)(q21q31). The deleted region included an assigned locus for an FAP major gene (5q21-q22). All of the metaphases analyzed in this case showed an extra segment of bright fluorescence on the short arm of chromosome 15, but this unusual chromosome (15p+) was observed in both peripheral lymphocyte and skin fibroblast cultures from the patient, indicating that the 15p+ was constitutional in nature. In Case 2, no clonal rearrangements were identified and most cells had a normal karyotype. However, two cells showed rearrangements involving a 17q with non-identical breakpoints, one of which was observed as a solitary chromosome change. Based on the present findings in Case 1 and those reported so far, the chromosomal defect on 5q might be one of the causal genetic events primarily associated with the development of both benign desmoid tumors and colorectal adenomas and carcinomas in FAP patients.