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Biomedical subjects

Magnus von Knebel Doeberitz

Publications and source records attributed to Magnus von Knebel Doeberitz.

At least 19 recordsLinked to original sources
PubMed2007

Triage of women with ASCUS and LSIL cytology: use of qualitative assessment of p16INK4a positive cells to identify patients with high-grade cervical intraepithelial neoplasia.

BACKGROUND: The identification of a small percentage of high-grade cervical intraepithelial neoplasias (HGCIN) among patients with minor cytological abnormalities (atypical squamous cells of undetermined significance [ASCUS] and/or low-grade squamous intraepithelial lesions [LSIL] group) is a major problem in cytology-based cervical cancer screening. The authors investigated the efficacy of p16INK4a as a biomarker to identify samples of patients with HGCIN among those with an ASCUS or LSIL result in Papanicolaou cytology. METHODS: Consecutive liquid-based cytology specimens of 137 ASCUS and 88 LSIL results were selected from gynecologists who adopted a triage regimen with biopsy under colposcopy 2 months later, independent of the p16INK4a result. p16INK4a stained slides were prepared and independently read by 2 observers, who used a recently described score to categorize p16INK4a stained squamous cells. The endpoint of the study was detection of a biopsy-confirmed HGCIN. RESULTS: The overall sensitivity and specificity of p16INK4a positive cells with a nuclear score >2 for diagnosis of HGCIN in ASCUS and LSIL cases combined was 96% and 83%, respectively. The sensitivity and specificity in the ASCUS group was 95% and 84%, and 100% and 81% in the LSIL group, respectively. Two observers had a high concordance in assessing p16INK4a stained cells (kappa value of 0.841). CONCLUSIONS: These data suggested that the use of p16INK4a as a biomarker combined with nuclear scoring of p16INK4a positive cells in cervical cytology to triage ASCUS and/or LSIL cases allows identification of HGCIN with good sensitivity and specificity.

Adolescent↗
PubMed2007

The additive effect of p53 Arg72Pro and RNASEL Arg462Gln genotypes on age of disease onset in Lynch syndrome patients with pathogenic germline mutations in MSH2 or MLH1.

p53 and the prostate-cancer-susceptibility gene RNASEL are tumour suppressor genes involved in apoptosis. We have previously reported that the common, functionally different variants Arg72Pro in p53 and Arg462Gln in RNASEL are associated with the age of disease onset of colorectal cancer in Lynch syndrome patients. To assess the combined effect of both variants, we screened 246 unrelated Lynch syndrome patients with a pathogenic germline mutation either in MSH2 (n=138) or in MLH1 (n=108) and colorectal cancer as first tumour, and 245 healthy controls. The global log rank test revealed significant differences in the age of disease onset for the genotypes of each variant (p=0.0176 for p53 and p=0.0358 for RNASEL) and for the combined genotypes of both variants (p=0.0174). The highest difference in median age of disease onset was seen between homozygotes for the wild-types in both genes (42years [range 22-75]) and homozygotes for the variant alleles in both genes (30years [range 26-47]). A multivariate Cox regression model indicated that only the p53 and RNASEL genotypes had a significant influence on age of disease onset (p=0.016 for p53 and p=0.014 for RNASEL) in an additive mode of inheritance, and that the effects of both variants are purely additive, which supports the notion that the p53 and RNaseL pathways do not interact. These findings may be relevant for preventive strategies in Lynch syndrome.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Identification of high-grade cervical dysplasia by the detection of p16INK4a in cell lysates obtained from cervical samples.

BACKGROUND: Current cervical cancer screening approaches are based on cytology supplemented by human papillomavirus (HPV) testing in some settings. Whereas cytology is laborious and depends on the cytologists' experience, HPV testing has limited specificity when it is used to detect high-grade lesions. A dichotomous test to identify high-grade lesions with greater specificity may be a useful tool for cervical cancer screening. p16(INK4a) is a cell-cycle regulator that has demonstrated strong overexpression in cervical precancer cells and cervical cancer induced by the deregulated expression of HPV oncogenes. METHODS: The authors used a sandwich enzyme-linked immunosorbent assay (ELISA) to quantify the amount of solubilized p16(INK4a) protein in lysates that were prepared from cervical samples to detect high-grade cervical lesions. In total, 187 specimens that were obtained after sampling for conventional cytology in women who attended a cervical colposcopy clinic were analyzed. Seventy-six women underwent a biopsy, and 45 of those women showed histologically confirmed, high-grade cervical intraepithelial neoplasia. RESULTS: For 76 women with biopsy-proven diagnoses, receiver operating characteristic (ROC) analysis of different cutoff values showed an area under the ROC curve of 0.89 for the detection of high-grade cervical dysplasia. At a cutoff value of 8 U/mL, the sensitivity of the p16(INK4a) ELISA for detecting high-grade dysplastic cervical lesions was 96%. CONCLUSIONS: The data obtained in this study suggested that ELISA-based quantification of solubilized p16(INK4a) protein may have high sensitivity for detecting cervical precancer. Further population-based studies will be necessary to analyze the specificity and predictive values of p16(INK4a) protein quantification in cervical samples.

Adolescent↗
PubMed2006

Prognostic impact of hematogenous tumor cell dissemination in patients with stage II colorectal cancer.

Adjuvant chemotherapy is not routinely recommended in patients with colorectal cancer stage UICC II. Some of these patients, however, develop recurrent disease. Therefore, valid prognostic criteria are needed to identify high-risk patients who might benefit from adjuvant therapy. Disseminated tumor cells, detected in blood and bone marrow, may prove to be a valid marker, however, the prognostic relevance of these cells remains debated. In our study, we examined the prognostic significance of disseminated tumor cells in blood and bone marrow of patients with stage II colorectal cancer. Ninety patients with potentially curative (R0) resection of colorectal cancer stage II were prospectively enrolled into the study. Bone marrow and blood samples were examined for disseminated tumor cells by CK 20 RT-PCR. Patient, tumor and treatment factors were analyzed as prognostic factors. Multivariate analysis confirmed tumor cell detection in blood (hazard ratio 2.1, p = 0.03) and T-category (hazard ratio 2.2, p = 0.02) to be independent prognostic factors for relapse-free survival. Tumor cell detection in postoperative blood samples (hazard ratio 7.7, p < 0.001) and number of removed lymph nodes (hazard ratio 6.4, p < 0.001) were independent prognostic factors for disease-specific survival. Detection of circulating tumor cells in blood samples of patients with stage II colorectal cancer identifies patients with poor outcome. This finding should be confirmed by further studies and could then be used as a basis for conducting a randomized trial evaluating the effect of adjuvant chemotherapy in stage II patients.

Aged↗
PubMed2006

Increased detection rate and potential prognostic impact of disseminated tumor cells in patients undergoing endorectal ultrasound for rectal cancer.

BACKGROUND: Hematogenous tumor-cell dissemination during diagnostic and therapeutic procedures in patients with colorectal cancer has been demonstrated. OBJECTIVE: The aim of this study was to investigate the extent of disseminated tumor cells in blood samples of rectal cancer patients after endorectal ultrasound and to determine its prognostic relevance. MATERIALS AND METHODS: Peripheral venous blood samples from 45 patients with rectal cancer were taken before and after endorectal ultrasound. Blood samples were examined using a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to amplify cytokeratin 20 transcripts. Overall survival of the patients was calculated by the Kaplan-Meier method. RESULTS: Disseminated tumor cells were detected in peripheral blood samples of 17 of 45 (38%) patients before and after endorectal ultrasound. Circulating tumor cells were found in 11 of 45 (24%) patients only after endorectal ultrasound (p=0.006). There was a clear trend toward a worse prognosis in patients with tumor cells in blood samples after endorectal ultrasound, but this difference was not statistically significant. CONCLUSION: This study demonstrates significantly increased hematogenous tumor-cell dissemination after endorectal ultrasound in rectal cancer patients. Patients with tumor cells in blood samples after endorectal ultrasound tend to have a worse prognosis. The potential prognostic impact of this finding is presently unclear and has to be further validated in larger clinical trials.

Endoscopy, Gastrointestinal↗
PubMed2006

Absence of association between cyclin D1 (CCND1) G870A polymorphism and age of onset in hereditary nonpolyposis colorectal cancer.

CCND1 encodes cyclin D1, which plays an important role in the G1 to S phase transition of the cell cycle. A common polymorphism (c.G870A) increases alternate splicing. Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by mutations in mismatch repair (MMR) genes, mainly MSH2 and MLH1, and shows a wide range in the age of its onset (AO), suggesting the existence of other modifying genetic factors. To date, two studies have investigated the association between CCND1 G/A variation and AO in HNPCC with contradictory results in 86 and 146 MMR mutation carriers, respectively. To clarify the role of the CCND1 G/A variation in HNPCC, we performed a study in 406 individuals carrying exclusively clear cut pathogenic mutations in MSH2 or MLH1. We did not observe a significant difference in genotype frequencies of affected and unaffected mutation carriers and healthy controls. A significant association between CCND1 genotypes and AO was found neither in the global comparison (log-rank, P = 0.2981; Wilcoxon, P = 0.2567) nor in a multivariate Cox regression analysis (hazard ratios 1.111, 95%CI 0.950-1.299, P = 0.188 and 1.090, 95%CI 0.868-1.369, P = 0.459 for the additive and dominant effect, respectively). We conclude, that the CCND1 G870A sequence variation is not a genetic modifier of the phenotype of HNPCC.

Adolescent↗
PubMed2006

Tetranucleotide repeats in coding regions: no evidence for involvement in EMAST carcinogenesis.

Genetic instability is a hallmark of malignancy. In the majority of malignant tumors, chromosomal instability leads to major numerical and structural chromosomal aberrations. In contrast, some tumors have a deficient DNA mismatch repair system and accumulate mutations particularly in repetitive mono- and dinucleotide sequences, a phenomenon referred to as microsatellite instability (MSI). Recently, a novel phenotype of tumors presenting with elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) has been reported. To date, not much is known about the molecular mechanisms of EMAST tumorigenesis. In MSI tumors, instability at specific mono- and dinucleotide repeats leads to alteration of genes carrying these repeats and thus may contribute to MSI tumorigenesis. We hypothesized that, similarly to the MSI phenotype, development of EMAST cancers may be promoted by mutations affecting tetranucleotides located in coding regions of the genome. To test this hypothesis, we performed a genome-wide database search to identify tetranucleotides in gene-encoding regions. Only seven tetranucleotide repeats located in predicted gene-encoding regions were retrieved. Allele length analysis yielded three remaining candidates with a monomorphic pattern in healthy individuals. Mutation analysis revealed that none of these three candidates displayed mutations in EMAST-positive bladder cancers. These data suggest that mutational inactivation of tetranucleotide-containing genes is very unlikely to contribute to the progression of EMAST tumors.

Biomarkers, Tumor↗
PubMed2006

Compound heterozygosity for two MSH6 mutations in a patient with early onset of HNPCC-associated cancers, but without hematological malignancy and brain tumor.

Heterozygous germline mutations in the human mismatch repair (MMR) genes MLH1, PMS2, MSH2 and MSH6 predispose to the hereditary non-polyposis colorectal cancer (HNPCC) syndrome. Biallelic mutations in these genes have been reported for a limited number of cases resulting in hematological malignancies, brain tumors and gastrointestinal tumors early in childhood. These tumor phenotypes are frequently associated with café-au-lait spots (CALS), one of the clinical hallmarks of neurofibromatosis type 1 (NF1). We report the first case of compound heterozygosity for two MSH6 mutations resulting in a nonconservative amino-acid change of a conserved residue and in a premature stop codon in a patient who developed rectal and endometrial cancer at ages 19 and 24 years, respectively, and presented few CALS in a single body segment. Immunohistochemistry and Western blotting revealed only residual expression of the MSH6 protein in the normal cells. The disease history resembles the HNPCC phenotype rather than a phenotype associated with biallelic MMR gene mutations. Therefore, we assume that one or both mutations abolish protein function only partially, further supported by the parents, which are both carriers of one of the mutations each, and not affected by the disease at ages 57 and 58 years. Our data suggest considering biallelic mutations in MMR genes for patients who develop HNPCC-associated tumors at an unusually young age of onset, even without hematological or brain malignancies.

Adult↗
PubMed2006

Microsatellite instability in the development of DNA mismatch repair deficient tumors.

Microsatellites are highly abundant short repetitive sequences found in the genomes across different species. They have gained increasing interest in recent years because length alterations in several coding as well as non-coding microsatellites are associated with a variety of different disorders. Particularly, microsatellite mutations play an important role in tumorigenesis of DNA mismatch repair deficient tumors that account for up to a 15% of colorectal, endometrial, and various other cancers. The systematic analysis of the distribution and function of affected microsatellite sequences has facilitated to unravel important steps in the selection processes that drive tumorigenesis. Here, we review the role of microsatellite mutations in the development of cancers with DNA mismatch repair deficiency, outlining biostatistical approaches for the identification of MSI target genes with relevance to MSI associated carcinogenesis. Knowledge about the biological impact of microsatellite mutations in these genes will potentially help to develop modified clinical concepts for diagnosis, prevention, and treatment of microsatellite unstable human cancers.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed2005

Evaluation of a nuclear score for p16INK4a-stained cervical squamous cells in liquid-based cytology samples.

BACKGROUND: The p16INK4a gene product is overexpressed strongly in abnormal cervical epithelia and may serve as a valuable biomarker to identify abnormal cells in cervical smears or liquid-based cytology samples. METHODS: The authors performed p16INK4a immunocytochemistry to locate cells that expressed p16INK4a in liquid-based cytology samples and used a nuclear scoring system based on several morphologic criteria to interpret the degree of abnormality of these cells. RESULTS: Among 108 samples that were scored as normal in Papanicolaou-stained, parallel slides, any p16INK4a-positive cells were observed in 13 samples (12%), but only 1 of 108 samples (1%) was scored abnormal after applying nuclear scoring criteria. In the group of 52 low-grade squamous intraepithelial lesion (LSIL) samples, 19 samples (37%) were positive for any p16INK4a reactivity, but only 5 of those samples (10%) were scored abnormal after applying the nuclear score. Among the 50 high-grade squamous intraepithelial lesion (HSIL) samples, 49 samples (98%) were positive for p16INK4a and were scored as abnormal. Comparison of the scoring results of independent observers revealed good reproducibility of the nuclear score. CONCLUSIONS: The current results suggested that p16INK4a enables the location of potentially abnormal cells on liquid-based cytology samples. The nuclear score facilitated interpretation of the degree of abnormality of p16INK4a-stained cells. Thus, locating potentially abnormal cells by p16INK4a immunocytochemistry and their interpretation based on the nuclear score described here may help to identify patients with HSIL in cytologic screening programs and may represent a new approach for reducing the number of equivocal or misinterpreted cytologic specimens.

Adolescent↗
PubMed2005

Clonal history of papillomavirus-induced dysplasia in the female lower genital tract.

BACKGROUND: Dysplastic lesions of the vagina or the vulva often occur in women who have a previous history of cervical dysplasia. Most lesions in the female lower genital tract are induced by infections with high-risk oncogenic human papillomaviruses (HR-HPVs), including HPV16 and HPV18. HR-HPV genomes frequently integrate into host cell chromosomes at random sites. We analyzed viral integration sites in multiple metachronous lesions of the lower genital tract from women previously treated for HR-HPV-positive cervical dysplasia or cancer to determine whether the metachronous lesions emerged from a single common preexisting dysplastic cell clone or as consequence of independent HR-HPV infection events in the female lower genital tract. METHODS: From among 1500 patients with anogenital lesions, seven patients with high-grade vaginal or vulvar lesions and with a previous history of cervical disease (five with prior high-grade cervical dysplasia and two with a history of cervical cancer) were included in this study. Integration sites of HPV16 or HPV18 in vaginal or vulvar lesions were mapped by an adaptor ligation polymerase chain reaction (PCR) method. The sequence information was used to design an integrate-specific PCR assay that was applied to DNA extracted from archival paraffin-embedded material derived from biopsy samples of cervical lesions. RESULTS: Identical HPV DNA integration loci were found in vaginal or vulvar and cervical samples of all lesions available for four of the five patients with a prior history of high-grade cervical dysplasia and for both patients with a history of cervical cancer. CONCLUSIONS: These data indicate that high-grade dysplastic lesions in the female lower genital tract may emerge primarily as monoclonal lesions from a transformed cell population derived from the uterine cervix.

Adult↗
PubMed2005

N-acetyltransferase (NAT) 2 acetylator status and age of onset in patients with hereditary nonpolyposis colorectal cancer (HNPCC).

N-acetyltransferase (NAT) 2 is an essential polymorphic enzyme involved in the metabolism of various xenobiotics, including potential carcinogens. The individual differences in the NAT2 metabolic capacity are caused by allelic variants of the NAT2 gene which are determined by a pattern of single nucleotide polymorphisms (SNPs) resulting in slow (SA), intermediate (IA) or rapid acetylator (RA) phenotypes. Highly penetrant germline mutations in mismatch repair (MMR) genes are the cause of the disease in hereditary nonpolyposis colorectal cancer (HNPCC). There is no strict correlation between the type of germline mutation in MMR genes and the HNPCC phenotype, but age of tumor onset (AO) in HNPCC has been associated at least in part with different variants in apoptosis-related genes. To clarify the potential modifying role of the NAT2 acetylator status in HNPCC, we performed a multicenter study in 226 individuals with colorectal cancer carrying exclusively pathogenic germline mutations in MSH2 or MLH1. We did not observe any significant difference in the NAT2 acetylator status frequency between HNPCC patients and 107 healthy controls (P=0.156), and between MLH1 and MSH2 mutation carriers (P=0.198). Multivariate Cox regression analysis revealed that male patients had a significantly increased risk to develop CRC compared to females during any interval (P=0.043), while the NAT2 acetylator status (P=0.447) and the mutated gene (MLH1 or MSH2) (P=0.236) were not risk factors for AO. The median AO in HNPCC patients was 39 years in patients with RA as well as with SA status (P=0.347). In MLH1 mutation carriers, the median AO was 38 years in RA and 36 years in SA status patients (P=0.901), whereas in MSH2 mutation carriers, the median AO was 39 years in RA and 42 years in SA status patients (P=0.163). Log-rank test revealed a significantly lower age of CRC onset in male compared to female HNPCC patients (P=0.0442). These data do not support the hypothesis that the NAT2 acetylatorship acts as a modifying factor on AO in HNPCC-associated CRC.

Acetylation↗
PubMed2005

T25 repeat in the 3' untranslated region of the CASP2 gene: a sensitive and specific marker for microsatellite instability in colorectal cancer.

DNA mismatch repair deficiency is observed in about 10% to 15% of all colorectal carcinomas and in up to 90% of hereditary nonpolyposis colorectal cancer (HNPCC) patients. Tumors with mismatch repair defects acquire mutations in short repetitive DNA sequences, a phenomenon termed high-level microsatellite instability (MSI-H). The diagnosis of MSI-H in colon cancer is of increasing relevance, because MSI-H is an independent prognostic factor in colorectal cancer, seems to influence the efficacy of adjuvant chemotherapy, and is the most important molecular screening tool to identify HNPCC patients. To make MSI typing feasible for the routine pathology laboratory, highly reproducible and cost effective laboratory tests are required. Here, we describe a novel T25 mononucleotide marker in the 3'untranslated region of the CASP2 gene (CAT25) that displayed a quasimonomorphic repeat pattern in normal tissue of 200 unrelated individuals of Caucasian origin. In addition, CAT25 was monomorphic also in all tested donors of African and Asian origin (n = 102 and n = 79, respectively) and thus differs from the most commonly used markers BAT25 and BAT26. Without the analysis of corresponding normal tissue, CAT25 correctly detected 56 of 57 colorectal cancer specimens classified as MSI-H by using the standard National Cancer Institute/International Collaborative Group-HNPCC marker panel. Combined with the standard markers BAT25 and BAT26 in a multiplex PCR, all MSI-H colorectal cancer samples were typed correctly. No false-positive results were obtained in 60 non-MSI-H control colorectal cancer specimens. These data suggest that CAT25 should be included into novel marker panels for microsatellite testing thus allowing for a significant reduction of the complexity and costs of MSI typing. Moreover, CAT25 represents a highly promising marker for early detection of colorectal cancer in HNPCC germ line mutation carriers.

3' Untranslated Regions↗
PubMed2005

Immunoselective pressure and human leukocyte antigen class I antigen machinery defects in microsatellite unstable colorectal cancers.

In colorectal cancer, the immune response is particularly pronounced against tumors displaying the high microsatellite instability (MSI-H) phenotype. MSI-H tumors accumulate mutations affecting microsatellites located within protein encoding regions (coding microsatellites, cMS), which lead to translational shifts of the respective reading frames. Consequently, novel tumor-specific frameshift-derived neopeptides (FSP) are generated and presented by MSI-H tumor cells, thus eliciting effective cytotoxic immune responses. To analyze whether the immunoselective pressure was reflected by the phenotype of MSI-H colorectal cancer cells, we compared here the expression of antigen processing machinery (APM) components and human leukocyte antigen (HLA) class I antigen subunits in 20 MSI-H and 20 microsatellite-stable (MSS) colorectal cancer using a panel of newly developed APM component-specific monoclonal antibodies. In addition, we did a systematic analysis of mutations at cMS located within APM genes and beta2-microglobulin (beta2m). Total HLA class I antigen loss was observed in 12 (60.0%) of the 20 MSI-H lesions compared with only 6 (30.0%) of the 20 MSS colorectal cancer lesions. Moreover, total loss of membraneous HLA-A staining was significantly more frequent in MSI-H colorectal cancer (P = 0.0024). Mutations at cMS of beta2m and genes encoding APM components (TAP1 and TAP2) were detected in at least 7 (35.0%) of 20 MSI-H colorectal cancers but in none of the MSS colorectal cancers (P = 0.0002). These data show that defects of HLA class I antigen processing and presentation seem to be significantly more frequent in MSI-H than in MSS colorectal cancer, suggesting that in MSI-H colorectal cancer the immunoselective pressure leads to the outgrowth of cells with defects of antigen presentation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Regulation of AKT1 expression by beta-catenin/Tcf/Lef signaling in colorectal cancer cells.

The serine/threonine kinase AKT plays a critical role in controlling the balance between cell survival and apoptosis. Several reports implicated AKT in the molecular pathogenesis of different human malignancies and overexpression of AKT was recently demonstrated to be an early event in colorectal carcinogenesis. We report here the identification of nine putative Tcf/Lef-binding elements (TBEs) upstream to the ATG initiation site of the AKT1 gene. Four of these TBEs are located upstream of the transcriptional start, whereas five TBEs are situated in Exon 1 of the AKT1 gene. Accordingly, we hypothesized that AKT1 expression might be regulated by Wnt/beta-catenin signaling. To elucidate the regulation of AKT expression in colon cancer cells, we generated reporter constructs containing the luciferase gene under the control of different regions derived from the AKT1 promoter/enhancer. Transient expression of the constructs in colorectal cancer (CRC) cell lines resulted in significant activation of the reporter gene. Luciferase was stimulated 20- to 50-fold in SW480, SW948 and HCT116 CRC cells. In contrast, the AKT1 promoter/enhancer constructs showed only a weak response in 293 embryonic kidney cells. Coexpression of a constitutively active beta-catenin mutant in colon cancer cells further enhanced reporter gene activation from the AKT1 promoter/enhancer, whereas it was downregulated by introduction of either wild-type APC or dnTcf-4. In addition, immunohistochemical staining of tumor sections derived from CRC patients showed elevated expression levels of AKT1, correlating with enhanced cytoplasmic/nuclear expression of beta-catenin. In summary our data suggest that beta-catenin/Tcf contributes to the transcriptional regulation of the AKT1 gene.

Apoptosis↗