RESUMEN
BACKGROUND: Familial Colorectal Cancer Type X (FCCTX) is defined as individuals with colorectal cancer (CRC) who families meet Amsterdam Criteria-1 (AC1), but whose tumours are DNA-mismatch-repair-proficient, unlike Lynch syndrome (LS). FCCTX does not have an increased risk of extra-colonic cancers. This analysis compares epidemiologic and clinicopathologic features among FCCTX, LS, and 'non-familial' (non-AC1) CRC cases. METHODS: From the Colon Cancer Family Registry, FCCTX (n=173), LS (n=303), and non-AC1 (n=9603) CRC cases were identified. Questionnaire-based epidemiologic information and CRC pathologic features were compared across case groups using polytomous logistic regression. RESULTS: Compared with LS, FCCTX cases were less likely to be current (vs never) smokers; have a proximal subsite (vs rectal) tumour; or have mucinous histology, poor differentiation, or tumour-infiltrating lymphocytes. There were no observed differences in co-morbidities or medication usage. CONCLUSIONS: FCCTX were less likely to be current tobacco users; other exposures were similar between these groups. Histopathologic differences highly suggestive of LS CRCs do not appear to be shared by FCCTX.
Asunto(s)
Neoplasias Colorrectales Hereditarias sin Poliposis/epidemiología , Neoplasias Quísticas, Mucinosas y Serosas/epidemiología , Anciano , Neoplasias Colorrectales Hereditarias sin Poliposis/patología , Comorbilidad , Femenino , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Neoplasias Quísticas, Mucinosas y Serosas/patología , Oportunidad Relativa , Sistema de Registros , Encuestas y CuestionariosRESUMEN
Array comparative genomic hybridization (aCGH) technology is commonly used to estimate genome-wide copy-number variation and to evaluate associations between copy number and disease. Although aCGH technology is well developed and there are numerous algorithms available for estimating copy number, little attention has been paid to the important issue of the statistical experimental design. Herein, we review classical statistical experimental designs and discuss their relevance to aCGH technology as well as their importance for downstream statistical analyses. Furthermore, we provide experimental design guidance for various study objectives.
Asunto(s)
Hibridación Genómica Comparativa/métodos , Variaciones en el Número de Copia de ADN , Genética de Población/métodos , Unión Competitiva , Cromosomas Humanos/genética , Sondas de ADN/genética , Estudios de Asociación Genética , Enfermedades Genéticas Congénitas/diagnóstico , Enfermedades Genéticas Congénitas/genética , Genoma Humano , Humanos , Análisis de Secuencia por Matrices de Oligonucleótidos , Estándares de Referencia , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Analysis of 84 human X chromosomes for the presence of interrupting AGG trinucleotides within the CGG repeat tract of the FMR1 gene revealed that most alleles possess two interspersed AGGs and that the longest tract of uninterrupted CGG repeats is usually found at the 3' end. Variation in the length of the repeat appears polar. Alleles containing between 34 and 55 repeats, with documented unstable transmissions, were shown to have lost one or both AGG interruptions. These comparisons define an instability threshold of 34-38 uninterrupted CGG repeats. Analysis of premutation alleles in Fragile X syndrome carriers reveals that 70% of these alleles contain a single AGG interruption. These data suggest that the loss of an AGG is an important mutational event in the generation of unstable alleles predisposed to the Fragile X syndrome.
Asunto(s)
Proteínas del Tejido Nervioso/genética , Proteínas de Unión al ARN , Cromosoma X , Secuencia de Bases , ADN , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil , Humanos , Masculino , Modelos Genéticos , Datos de Secuencia Molecular , Mutación , Secuencias Repetitivas de Ácidos NucleicosRESUMEN
BACKGROUND: Carriers of germline mutations in DNA mismatch repair (MMR) genes have a high risk of colorectal cancer (CRC), but the modifiers of this risk are not well established. We estimated an association between body mass index (BMI) in early adulthood and subsequent risk of CRC for carriers and, as a comparison, estimated the association for non-carriers. METHODS: A weighted Cox regression was used to analyse height and weight at 20 years reported by 1324 carriers of MMR gene mutations (500 MLH1, 648 MSH2, 117 MSH6 and 59 PMS2) and 1219 non-carriers from the Colon Cancer Family Registry. RESULTS: During 122,304 person-years of observation, we observed diagnoses of CRC for 659 carriers (50%) and 36 non-carriers (3%). For carriers, the risk of CRC increased by 30% for each 5 kg m(-2) increment in BMI in early adulthood (hazard ratio, HR: 1.30; 95% confidence interval, CI: 1.08-1.58; P=0.01), and increased by 64% for non-carriers (HR: 1.64; 95% CI: 1.02-2.64; P=0.04) after adjusting for sex, country, cigarette smoking and alcohol drinking (and the MMR gene that was mutated in carriers). The difference in HRs for carriers and non-carriers was not statistically significant (P=0.50). For MLH1 and PMS2 (MutLα heterodimer) mutation carriers combined, the corresponding increase was 36% (HR: 1.36; 95% CI: 1.05-1.76; P=0.02). For MSH2 and MSH6 (MutSα heterodimer) mutation carriers combined, the HR was 1.26 (95% CI: 0.96-1.65; P=0.09). There was no significant difference between the HRs for MutLα and MutSα heterodimer carriers (P=0.56). CONCLUSION: Body mass index in early adulthood is positively associated with risk of CRC for MMR gene mutation carriers and non-carriers.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/genética , Adenosina Trifosfatasas/genética , Índice de Masa Corporal , Neoplasias Colorrectales/genética , Enzimas Reparadoras del ADN/genética , Proteínas de Unión al ADN/genética , Mutación de Línea Germinal/genética , Proteína 2 Homóloga a MutS/genética , Proteínas Nucleares/genética , Adulto , Reparación de la Incompatibilidad de ADN , Femenino , Estudios de Seguimiento , Heterocigoto , Humanos , Masculino , Persona de Mediana Edad , Endonucleasa PMS2 de Reparación del Emparejamiento Incorrecto , Homólogo 1 de la Proteína MutL , Pronóstico , Factores de Riesgo , Adulto JovenRESUMEN
Founder mutations are an important cause of Lynch syndrome and facilitate genetic testing in specific ethnic populations. Two putative founder mutations in MSH6 were analyzed in 2685 colorectal cancer (CRC) cases, 337 endometrial cancer (EnCa) cases and 3310 healthy controls of Ashkenazi Jewish (AJ) descent from population-based and hospital-based casecontrol studies in Israel, Canada and the United States. The carriers were haplotyped and the age of the mutations was estimated. MSH6*c.3984_3987dupGTCA was found in 8/2685 CRC cases, 2/337 EnCa cases, and 1/3310 controls, consistent with a high risk of CRC (odds ratio (OR) = 9.9, 95% confidence interval (CI) = 1.278.9, p = 0.0079) and a very high risk of EnCa (OR = 19.6, 95% CI = 1.8217.2, p = 0.0006). MSH6*c.3959_3962delCAAG was identified in 3/2685 CRC cases, 2/337 EnCa cases and no controls. Each mutation was observed on separate conserved haplotypes. MSH6*c.3984_3987dupGTCA and MSH6*c.3959_3962delCAAG probably arose around 585 CE and 685 CE, respectively. No carriers were identified in Sephardi Jews (450 cases and 490 controls). Truncating mutations MSH6*c.3984_3987dupGTCA and MSH6*c.3959_3962delCAAG cause Lynch syndrome and are founder mutations in Ashkenazi Jews. Together with other AJ founder mutations, they contribute substantially to the incidence of CRC and EnCa and are important tools for the early diagnosis and appropriate management of AJ Lynch syndrome patients.
Asunto(s)
Neoplasias Colorrectales Hereditarias sin Poliposis/genética , Proteínas de Unión al ADN/genética , Efecto Fundador , Mutación INDEL , Judíos , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Neoplasias Colorrectales Hereditarias sin Poliposis/etnología , Neoplasias Endometriales/etnología , Neoplasias Endometriales/genética , Femenino , Estudios de Asociación Genética , Marcadores Genéticos , Predisposición Genética a la Enfermedad , Haplotipos , Humanos , Masculino , Persona de Mediana Edad , Oportunidad Relativa , Polimorfismo de Nucleótido Simple , Análisis de Secuencia de ADN , Adulto JovenRESUMEN
BACKGROUND AND AIMS: Colorectal cancer (CRC) is the second most frequent cancer in developed countries. Newfoundland has the highest incidence of CRC in Canada and the highest rate of familial CRC yet reported in the world. To determine the impact of mutations in known CRC susceptibility genes and the contribution of the known pathways to the development of hereditary CRC, an incident cohort of 750 patients with CRC (708 different families) from the Newfoundland population was studied. METHODS: Microsatellite instability (MSI) testing was performed on tumours, together with immunohistochemistry analysis for mismatch repair (MMR) genes. Where indicated, DNA sequencing and multiplex ligation-dependent probe amplifications of MMR genes and APC was undertaken. DNA from all patients was screened for MUTYH mutations. The presence of the BRAF variant, p.V600E, and of MLH1 promoter methylation was also tested in tumours. RESULTS: 4.6% of patients fulfilled the Amsterdam criteria (AC), and an additional 44.6% fulfilled the revised Bethesda criteria. MSI-high (MSI-H) was observed in 10.7% (n=78) of 732 tumours. In 3.6% (n=27) of patients, CRC was attributed to 12 different inherited mutations in six known CRC-related genes associated with chromosomal instability or MSI pathways. Seven patients (0.9%) carried a mutation in APC or biallelic mutations in MUTYH. Of 20 patients (2.7%) with mutations in MMR genes, 14 (70%) had one of two MSH2 founder mutations. 17 of 28 (61%) AC families did not have a genetic cause identified, of which 15 kindreds fulfilled the criteria for familial CRC type X (FCCTX). CONCLUSIONS: Founder mutations accounted for only 2.1% of cases and this was insufficient to explain the high rate of familial CRC. Many of the families classified as FCCTX may have highly penetrant mutations segregating in a Mendelian-like manner. These families will be important for identifying additional CRC susceptibility loci.
Asunto(s)
Neoplasias Colorrectales/genética , Proteínas Adaptadoras Transductoras de Señales/genética , Adulto , Distribución por Edad , Anciano , Neoplasias Colorrectales/epidemiología , Metilación de ADN , Reparación de la Incompatibilidad de ADN/genética , ADN de Neoplasias/genética , Femenino , Efecto Fundador , Predisposición Genética a la Enfermedad , Humanos , Masculino , Inestabilidad de Microsatélites , Persona de Mediana Edad , Homólogo 1 de la Proteína MutL , Mutación , Proteínas de Neoplasias/genética , Terranova y Labrador/epidemiología , Proteínas Nucleares/genética , Regiones Promotoras Genéticas , Proteínas Proto-Oncogénicas B-raf/genética , Sistema de RegistrosRESUMEN
Colorectal tumor DNA was examined for somatic instability at (CA)n repeats on human chromosomes 5q, 15q, 17p, and 18q. Differences between tumor and normal DNA were detected in 25 of the 90 (28 percent) tumors examined. This instability appeared as either a substantial change in repeat length (often heterogeneous in nature) or a minor change (typically two base pairs). Microsatellite instability was significantly correlated with the tumor's location in the proximal colon (P = 0.003), with increased patient survival (P = 0.02), and, inversely, with loss of heterozygosity for chromosomes 5q, 17p, and 18q. These data suggest that some colorectal cancers may arise through a mechanism that does not necessarily involve loss of heterozygosity.
Asunto(s)
Neoplasias del Colon/genética , Neoplasias Colorrectales/genética , ADN de Neoplasias/genética , ADN Satélite/genética , Mutación , Adulto , Anciano , Anciano de 80 o más Años , Cromosomas Humanos Par 15 , Cromosomas Humanos Par 17 , Cromosomas Humanos Par 18 , Cromosomas Humanos Par 5 , Femenino , Heterocigoto , Humanos , Masculino , Persona de Mediana Edad , Reacción en Cadena de la Polimerasa , Secuencias Repetitivas de Ácidos NucleicosRESUMEN
To test the hypothesis that actin dysfunction leads to heart failure, patients with hereditary idiopathic dilated cardiomyopathy (IDC) were examined for mutations in the cardiac actin gene (ACTC). Missense mutations in ACTC that cosegregate with IDC were identified in two unrelated families. Both mutations affect universally conserved amino acids in domains of actin that attach to Z bands and intercalated discs. Coupled with previous data showing that dystrophin mutations also cause dilated cardiomyopathy, these results raise the possibility that defective transmission of force in cardiac myocytes is a mechanism underlying heart failure.
Asunto(s)
Actinas/genética , Cardiomiopatía Dilatada/genética , Mutación , Actinas/química , Actinas/fisiología , Adolescente , Adulto , Cardiomiopatía Dilatada/metabolismo , Cardiomiopatía Dilatada/patología , Niño , Preescolar , Cromosomas Humanos Par 15 , Exones , Femenino , Corazón/fisiopatología , Humanos , Masculino , Miocardio/química , Miocardio/patología , Linaje , Fenotipo , Polimorfismo Conformacional Retorcido-Simple , Conformación Proteica , Sarcómeros/fisiologíaAsunto(s)
Proteínas Adaptadoras Transductoras de Señales/genética , Adenosina Trifosfatasas/genética , Neoplasias Colorrectales/genética , Enzimas Reparadoras del ADN/genética , Proteínas de Unión al ADN/genética , Mutación , Proteínas Nucleares/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Adenosina Trifosfatasas/metabolismo , Cromatografía Líquida de Alta Presión/métodos , Estudios de Cohortes , Neoplasias Colorrectales/metabolismo , Análisis Mutacional de ADN/métodos , Enzimas Reparadoras del ADN/metabolismo , Proteínas de Unión al ADN/metabolismo , Humanos , Inmunohistoquímica , Endonucleasa PMS2 de Reparación del Emparejamiento Incorrecto , Homólogo 1 de la Proteína MutL , Proteínas Nucleares/metabolismo , Polimorfismo Genético , Sistema de RegistrosAsunto(s)
Disparidad de Par Base/genética , Neoplasias Colorrectales/genética , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/fisiología , Reparación del ADN/genética , Mutación , Transactivadores , Factores de Transcripción/fisiología , Proteína Axina , Línea Celular , Proteínas del Citoesqueleto/biosíntesis , Análisis Mutacional de ADN , Genes Reporteros , Humanos , Transducción de Señal , Factores de Transcripción TCF , Proteína 2 Similar al Factor de Transcripción 7 , Transfección , beta CateninaRESUMEN
Loss of heterozygosity (LOH) at specific loci may help localize tumor suppressor genes involved in the formation of various familial and sporadic tumors. In addition, the genetic loci for a number of familial tumor syndromes have been mapped by linkage analysis. To explore the possible role of tumor suppressor genes in endocrine tumors, we tested 41 pheochromocytomas (34 sporadic and 7 familial) and 11 medullary thyroid cancers (MTC) (10 sporadic and 1 familial) for LOH near a variety of potentially important genetic loci: (a) the multiple endocrine neoplasia type 2A (MEN 2A) locus on chromosome 10; (b) the von Hippel-Lindau locus on 3p; and (c) the p53 and neurofibromatosis 1 loci on 17. We also examined chromosomes 1p and 22q because previous studies in a small number of pheochromocytomas and MTCs suggested LOH in these regions. Background rates for LOH were assessed using several "random" probes. Finally, we examined a number of clinical and histologic characteristics of these tumors for possible correlations with specific genetic alterations. LOH in the region of the MEN 2A locus was uncommon (0% for MTCs, 5% for pheochromocytomas). However, we found significant allelic losses in pheochromocytomas on chromosomes 1p (42%), 3p (16%), 17p (24%), and 22q (31%). We also noted a correlation between LOH on 1p and urinary excretion of metanephrine by these patients (P = 0.02). LOH on 1p, 3p, and 17p also appeared to be associated with increased tumor volume. Analysis of the smaller number of MTCs demonstrated allelic losses on chromosomes 1p and 22q. Our results suggest that tumor formation and/or progression in pheochromocytomas and MTCs involves multiple genes, analogous with the model proposed for colon carcinoma.
Asunto(s)
Neoplasias de las Glándulas Suprarrenales/genética , Carcinoma/genética , Deleción Cromosómica , Heterocigoto , Feocromocitoma/genética , Neoplasias de la Tiroides/genética , Adolescente , Adulto , Anciano , Alelos , Niño , Cromosomas Humanos Par 10 , Cromosomas Humanos Par 17 , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
BACKGROUND: Microsatellite instability (MSI) and allelic imbalance involving chromosome arms 5q, 8p, 17p, and 18q are genetic alterations commonly found in colorectal cancer. We investigated whether the presence or absence of these genetic alterations would allow stratification of patients with Astler-Coller stage B2 or C colorectal cancer into favorable and unfavorable prognostic groups. METHODS: Tumors from 508 patients were evaluated for MSI and allelic imbalance by use of 11 microsatellite markers located on chromosome arms 5q, 8p, 15q, 17p, and 18q. Genetic alterations involving each of these markers were examined for associations with survival and disease recurrence. All P values are two-sided. RESULTS: In univariate analyses, high MSI (MSI-H), i.e., MSI at 30% or more of the loci examined, was associated with improved survival (P =.02) and time to recurrence (P =.01). The group of patients whose tumors exhibited allelic imbalance at chromosome 8p had decreased survival (P =.02) and time to recurrence (P =.004). No statistically significant associations with survival or time to recurrence were observed for markers on chromosome arms 5q, 15q, 17p, or 18q. In multivariate analyses, MSI-H was an independent predictor of improved survival (hazard ratio [HR] = 0.51; 95% confidence interval [CI] = 0.31-0.82; P =.006) and time to recurrence (HR = 0.42; 95% CI = 0.24-0.74; P =.003), and 8p allelic imbalance was an independent predictor of decreased survival (HR = 1.89; 95% CI = 1.25-2.83; P =. 002) and time to recurrence (HR = 2.07; 95% CI = 1.32-3.25; P =.002). CONCLUSIONS: Patients whose tumors exhibited MSI-H had a favorable prognosis, whereas those with 8p allelic imbalance had a poor prognosis; both alterations served as independent prognostic factors. To our knowledge, this is the first report of an association between 8p allelic imbalance and survival in patients with colorectal cancer.
Asunto(s)
Alelos , Cromosomas Humanos Par 8/genética , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Repeticiones de Microsatélite/genética , Adulto , Anciano , Análisis de Varianza , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Quimioterapia Adyuvante , Neoplasias Colorrectales/tratamiento farmacológico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Valor Predictivo de las Pruebas , Pronóstico , Estudios Retrospectivos , Riesgo , Análisis de SupervivenciaRESUMEN
The human tumor necrosis factor (TNF) locus is located on chromosome 6p21.3 and contains at least five polymorphic microsatellites. In this study, we compared the allelic frequencies derived from 50 normal controls to 64 patients with colorectal cancer at one of these loci, TNF alpha. No differences in allelic frequencies were observed between these two groups (P = 0.47). However, sequencing of the TNF alpha PCR product revealed two populations of TNF alpha alleles; alleles with the expected DNA sequence (i.e., the expected number of AC/GT repeats) and alleles that contained 8-bp deletions adjacent to the microsatellite repeat. In addition, we also examined paired normal and tumor DNA from the colorectal cancer group for microsatellite alterations at the TNF alpha locus, including allelic loss of heterozygosity and microsatellite instability. Of the 64 tumors examined, 13 (20%) demonstrated microsatellite instability, and 14 (42%) of 33 informative cases demonstrated allelic imbalance. Analysis of 10 additional chromosome 6 loci for allelic loss showed that 23 (47%) of 49 informative cases exhibited allelic imbalance with at least one chromosome 6p marker, 23 (47%) of 49 with at least one 6q marker, and 29 (59%) of 49 with at least one marker on chromosome 6. Examination of tumors for the minimal region of deletion overlap suggests the presence of tumor suppressor genes on both 6p and 6q.
Asunto(s)
Cromosomas Humanos Par 6 , Neoplasias Colorrectales/genética , Factor de Necrosis Tumoral alfa/genética , Alelos , Neoplasias Colorrectales/metabolismo , Eliminación de Gen , Frecuencia de los Genes , HumanosRESUMEN
Muir-Torre syndrome (MTS) is characterized by the presence of at least one sebaceous tumor and at least one visceral malignancy. Although a wide range of internal malignancies have been reported, the most frequently observed internal neoplasm is colorectal carcinoma. MTS and hereditary nonpolyposis colorectal carcinoma (HNPCC) share many clinical and pathological characteristics and thus may share similar genetic mechanisms of tumorigenesis. Recently, microsatellite instability (MIN) has been reported in tumor tissue from patients with HNPCC. In order to determine if tumors from MTS patients might also show MIN, we examined DNA extracted from paraffin-embedded tissues for the presence of MIN at (CA)n repeats on chromosomes 5q, 15q, 17p, and 18q. Data was obtained on 13 patients, 9 of which had at least one colorectal tumor. Of these, six demonstrated widespread MIN in all sebaceous and colorectal tumors examined, as well as in a transitional cell carcinoma of the renal pelvis, a prostatic adenocarcinoma and a keratoacanthoma. Overall, patients with MIN differed from patients without MIN in several respects, the most important of which include: (a) uniform presence and early onset of colorectal cancer (average age, 40 versus 70 years); (b) prolonged survival following diagnosis of visceral malignancy (median survival, 32 versus 11 years); and (c) a greater number of visceral and skin tumors. These data suggests that patients with MTS may be composed of at least two subgroups, each demonstrating different genetic, pathological and clinical features. Furthermore, the subgroup demonstrating MIN may share similar genetic mechanisms of tumorigenesis with patients having HNPCC, supporting the notion that these syndromes are allelic.
Asunto(s)
Neoplasias Colorrectales Hereditarias sin Poliposis/genética , Neoplasias Primarias Múltiples/genética , Neoplasias de las Glándulas Sebáceas/genética , Adulto , Anciano , Anciano de 80 o más Años , Alelos , Secuencia de Bases , Neoplasias Colorrectales Hereditarias sin Poliposis/patología , ADN de Neoplasias/genética , Femenino , Variación Genética , Humanos , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Neoplasias Primarias Múltiples/patología , Adhesión en Parafina , Neoplasias de las Glándulas Sebáceas/patología , Neoplasias Cutáneas/patologíaRESUMEN
Epidemiological studies have suggested that the breast cancer susceptibility genes, BRCA1 and BRCA2, may be involved in the development of prostate cancer. Several studies have screened prostate cancer populations for the presence of BRCA1 and BRCA2 mutations, with few mutations identified. In this study, 22 high-risk prostate cancer families (at least three cases of prostate cancer) were screened by conformation-sensitive gel electrophoresis (CSGE) for mutations in BRCA1 and BRCA2. To maximize the chance of finding mutations in these two genes, families were also selected for the presence of at least two cases of breast and/or ovarian cancer. We identified one previously reported BRCA2 missense mutation and two previously unreported BRCA2 intron polymorphisms. No BRCA1 or BRCA2 truncating mutations were detected. Thus, BRCA1 and BRCA2 appear to have a limited role in familial prostate cancer, and families with both prostate and breast cancer may result from mutations in other predisposition genes.
Asunto(s)
Proteína BRCA1/genética , Predisposición Genética a la Enfermedad , Proteínas de Neoplasias/genética , Neoplasias de la Próstata/genética , Factores de Transcripción/genética , Anciano , Proteína BRCA2 , Transformación Celular Neoplásica/genética , Regulación Neoplásica de la Expresión Génica , Humanos , Masculino , Persona de Mediana Edad , Mutación , Polimorfismo Genético , Neoplasias de la Próstata/epidemiologíaRESUMEN
Mutations in the p53 gene are the most common genetic changes in cancer thus far. Many p53 mutations result in a protein product having a prolonged half-life compared to wild-type p53. The mutant protein is frequently detectable immunohistochemically, whereas the wild-type p53 present in normal cells is not. We examined 90 colorectal carcinomas for increased expression of p53 using 3 p53 specific monoclonal antibodies, PAb1801, PAb421, and PAb240. Overall, 70% of the colorectal carcinomas stained for p53. Each tumor's DNA was also assessed for loss of heterozygosity on chromosome 17p, the location of the p53 gene. Of those tumors that reacted with the anti-p53 antibodies, 76% showed loss on chromosome 17p. Tumors with loss of heterozygosity on 17p generally stained with all 3 antibodies, whereas those without loss tended to stain with just one antibody, typically PAb240. Fifteen tumors were examined for the presence of specific p53 mutations. A total of 10 mutations were found, 6 were missense and 2 were deletions, and all but one of the tumors with missense mutations stained for p53.
Asunto(s)
Cromosomas Humanos Par 17 , Neoplasias Colorrectales/genética , Genes p53 , Mutación , Proteína p53 Supresora de Tumor/análisis , Alelos , Secuencia de Aminoácidos , Anticuerpos Monoclonales , Secuencia de Bases , Neoplasias Colorrectales/patología , ADN de Neoplasias/genética , ADN de Neoplasias/aislamiento & purificación , Expresión Génica , Humanos , Inmunohistoquímica , Mucosa Intestinal/patología , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos , Reacción en Cadena de la Polimerasa , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Cytogenetic analyses have demonstrated that chromosome region 7q22-32 is commonly altered in prostate adenocarcinomas. In addition, in recent fluorescence in situ hybridization studies, we have observed that aneusomy of chromosome 7 is frequent in prostate cancer and is associated with higher tumor grade, advanced pathological stage, and early prostate cancer death. These findings suggest that genetic alterations of chromosome 7 play a significant role in the development of prostate cancer. To better define the chromosome 7 alterations, PCR analysis of 21 microsatellite loci was performed on 54 paired prostate cancer and control DNAs. Overall, chromosome 7 allelic imbalance was identified in 16 of 54 cases (30%). Allelic imbalances of loci mapped to 7q were observed in 15 of the 16 cases. The allelic imbalances were classified as losses in 15 tumors (28%) and as gains in 1 (2%) by comparative multiplex PCR analysis. The most common site of allelic loss included loci D7S523 and D7S486 at 7q31.1. A comparison with clinicopathological features of the tested tumors revealed that the allelic loss of 7q31.1 correlated with higher tumor grade (P = 0.012) and lymph node metastasis (P = 0.017). These results indicate that 7q31 may be the site of a putative suppressor gene(s) important for the pathogenesis of prostate carcinoma, and that the genetic alterations at 7q31.1 may participate in tumor progression and metastasis.
Asunto(s)
Deleción Cromosómica , Cromosomas Humanos Par 7 , Neoplasias de la Próstata/genética , Alelos , Mapeo Cromosómico , Humanos , Masculino , Reacción en Cadena de la Polimerasa , Neoplasias de la Próstata/patologíaRESUMEN
Recent studies have demonstrated the presence of microsatellite instability (MSI) in tumors from patients with hereditary nonpolyposis colon cancer and in a subset of patients with sporadic colorectal cancer (CRC). In sporadic CRC, three tumor phenotypes have been defined: microsatellite stable (MSS), low-frequency MSI, and high-frequency MSI (MSI-H). Although defective mismatch repair, consisting primarily of alterations in hMSH2 and hMLH1, is believed to be responsible for the MSI phenotype in the majority of patients with hereditary nonpolyposis colon cancer, the genetic defect responsible for this phenotype in sporadic CRC has yet to be clearly delineated. Somatic or germ-line alterations in these two genes have been identified in only a minority of these cases. Analysis of the protein expression patterns of hMSH2 and hMLH1 in unselected CRC, however, suggests that alterations in hMLH1 may account for a majority of the MSI-H cases. In an effort to explore the underlying molecular basis for these findings, we have examined the methylation status of the presumptive hMLHI promoter region in 31 tumors that vary in regard to their MSI status (MSI-H or MSS), their hMLH1 protein expression (MLH- or MLH+), and their gene mutation (Mut+ or Mut-) status. Hypermethylation of the hMLH1 promoter occurred in all 13 MSI-H/ MLH- tumors that did not have a detectable mutation within the hMLH1 gene. Of those MSI-H tumors containing germ-line or somatic alterations in hMLH1 (n = 7, including 3 frameshift, 1 nonsense, 2 missense mutations, and 1 tumor containing multiple mutations: missense, splice-site alteration, and a frameshift), four had a normal methylation pattern, whereas three others demonstrated hypermethylation of the hMLH1 promoter region. Two of these cases had a missense alteration, the other a frameshift alteration. The single MSI-H/Mut+ tumor that had normal hMLH1 and hMSH2 expression, as well as 9 of the 10 MSS cases, lacked methylation of the hMLH1 promoter. Hypermethylation of the hMSH2 promoter was not observed for any of the cases. These results suggest that hypermethylation of the hMLH1 promoter may be the principal mechanism of gene inactivation in sporadic CRC characterized by widespread MSI.
Asunto(s)
Neoplasias del Colon/genética , Metilación de ADN , Proteínas de Unión al ADN , Repeticiones de Microsatélite , Proteínas de Neoplasias/genética , Regiones Promotoras Genéticas/fisiología , Proteínas Adaptadoras Transductoras de Señales , Proteínas Portadoras , Neoplasias del Colon/metabolismo , ADN de Neoplasias/genética , ADN de Neoplasias/metabolismo , Mutación de Línea Germinal , Humanos , Homólogo 1 de la Proteína MutL , Proteína 2 Homóloga a MutS , Proteínas Nucleares , Reacción en Cadena de la Polimerasa , Proteínas Proto-Oncogénicas/genéticaRESUMEN
Most colorectal adenomas and carcinomas arise in the setting of chromosomal instability characterized by progressive loss of heterozygosity. In contrast, approximately 15-20% of colorectal neoplasms arise through a distinct genetic pathway characterized by microsatellite instability (MSI) associated with frequent loss of expression of one of the DNA mismatch repair enzymes, most often hMLH1 or hMSH2. These distinct genetic pathways are reflected by differences in tumor histopathology, distribution in the colon, prognosis, and dwell time required for progression from adenoma to carcinoma. To determine whether these two groups of tumors differ in their expression of cyclooxygenase-2 (COX-2), a putative chemopreventative target, immunostaining for this protein was performed in colorectal cancers categorized by the presence (n = 41) and absence (n = 66) of defective mismatch repair. Defective mismatch repair was defined by the presence of tumor microsatellite instability (MSI-H, > or =40% of markers demonstrating instability) and by the absence of protein expression for either hMLH1 or hMSH2. Overall, our results showed that low or absent COX-2 staining was significantly more common among tumors with defective mismatch repair (P = 0.001). Other features predictive of low COX-2 staining included marked tumor infiltrating lymphocytosis, and solid/cribiform or signet ring histological patterns. These observations indicate that colorectal cancers with molecular and phenotypic characteristics of defective DNA mismatch repair express lower levels of COX-2. The clinical implications of this biological distinction remain unknown but should be considered when assessing the efficacy of COX-2 inhibitors for chemoprevention in patients whose tumors may arise in the setting of defective DNA mismatch repair.
Asunto(s)
Neoplasias Colorrectales/enzimología , Reparación del ADN , Proteínas de Unión al ADN , Isoenzimas/biosíntesis , Prostaglandina-Endoperóxido Sintasas/biosíntesis , Proteínas Adaptadoras Transductoras de Señales , Adulto , Anciano , Anciano de 80 o más Años , Proteínas Portadoras , Neoplasias Colorrectales/genética , Ciclooxigenasa 2 , Femenino , Humanos , Inmunohistoquímica , Masculino , Proteínas de la Membrana , Repeticiones de Microsatélite , Persona de Mediana Edad , Homólogo 1 de la Proteína MutL , Proteína 2 Homóloga a MutS , Proteínas de Neoplasias/biosíntesis , Proteínas Nucleares , Estudios Prospectivos , Proteínas Proto-Oncogénicas/biosíntesisRESUMEN
Recent studies have demonstrated the presence of microsatellite instability (MSI) in tumors from patients with hereditary nonpolyposis colorectal cancer and in a large number of sporadic tumors. To further characterize the type of alterations at these loci and their frequency of involvement in colon cancer, we studied DNA extracted from paraffin-embedded tissue from 508 patients using 11 microsatellites localized to chromosomes 5, 8, 15, 17, and 18. Overall, MSI at each locus varied in character and frequency and was observed with at least one marker in 191 cases (37.6%). Based on the number of markers displaying instability per tumor, three groups of patients were defined: those with <30% of the markers showing instability (MSI-L,, n = 109, 21.5%); those with > or = 30% (MSI-H, n = 82, 16.1%); and those showing no instability (MSS, n = 317, 62.4%). These groups were tested for correlations with a number of clinical and pathological parameters, including age, sex, stage, ploidy status, and site of tumor. Comparing across the three groups and verified by pair-wise comparisons, the MSI-H group was associated with tumor site (proximal colon, P = 0.001), sex (females, P = 0.005), stage (Dukes' B, P = 0.01), and ploidy status (diploid, P = 0.03). No significant differences were noted between the MSI-L and MSS group for any of the parameters tested. An additional 188 consecutive surgical colorectal cancer cases were examined for the presence of MSI and for the immunohistochemical expression of hMLH1 and hMSH2 proteins. Of this group, 129 (68.6%) were classified as MSS, 17 (9.0%) as MSI-L, and 42 (22.3%) as MSI-H. None of the MSS and none of the MSI-L tumors had altered expression of either hMLH1 or hMSH2. However, the majority of MSI-H (40 of 42, 95%) cases demonstrated absence of staining for these proteins. The most frequently altered protein was hMLH1, occurring in 95% of the tumors with altered expression. Cumulatively, these data suggest that the tumor phenotype MSI-H is distinct from tumor phenotypes MSI-L and MSS, with no apparent differences between MSI-L and MSS. Furthermore, altered hMLH1 protein expression appears to be responsible for the mutator phenotype in the vast majority of MSI-H tumors.