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PubMed1998

Pathogenesis of adenocarcinoma in Peutz-Jeghers syndrome.

Peutz-Jeghers syndrome (PJS) is an autosomal dominant condition characterized by intestinal hamartomatous polyps, mucocutaneous melanin deposition, and increased risk of cancer. Families with PJS from the Johns Hopkins Polyposis Registry were studied to identify the molecular basis of this syndrome and to characterize the pathogenesis of gastrointestinal hamartomas and adenocarcinomas in PJS patients. Linkage analysis in the family originally described by Jeghers in 1949 and five other families confirmed linkage to 19p13.3 near a recently identified gene responsible for PJS. Germ-line mutations in this gene, STK11, were identified in all six families by sequencing genomic DNA. Analysis of hamartomas and adenocarcinomas from patients with PJS identified loss of heterozygosity (LOH) of 19p markers near STK11 in 70% of tumors. Haplotype analysis indicated that the retained allele carried a germ-line mutation, confirming that STK11 is a tumor suppressor gene. LOH of 17p and 18q was identified in an adenocarcinoma but not in hamartomas, implying that allelic loss of these two regions corresponds to late molecular events in the pathogenesis of cancer in PJS. The adenocarcinomas showing 17p LOH also demonstrated altered p53 by immunohistochemistry. None of the 18 PJS tumors showed microsatellite instability, LOH on 5q near APC, or mutations in codons 12 or 13 of the K-ras proto-oncogene. These data provide evidence that STK11 is a tumor suppressor gene that acts as an early gatekeeper regulating the development of hamartomas in PJS and suggest that hamartomas may be pathogenetic precursors of adenocarcinoma. Additional somatic mutational events underlie the progression of hamartomas to adenocarcinomas, and some of these somatic mutations are common to the later stages of tumor progression seen in the majority of colorectal carcinomas.

Adenocarcinoma↗

PubMed2026

Prognostic significance of DNA damage response-related markers in esophageal squamous cell carcinoma using machine learning approaches.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) lacks reliable prognostic biomarkers. Homologous recombination deficiency (HRD) has been implicated in genomic instability across multiple cancers, but its prognostic significance in ESCC remains unexplored. This study aimed to evaluate HRD score as a prognostic biomarker and develop a machine learning-based predictive model for ESCC. METHODS: Transcriptomic and clinical data from 78 ESCC patients were obtained from The Cancer Genome Atlas (TCGA) and randomly split into training (70%) and test (30%) cohorts. Prognostic models were constructed using 112 machine learning algorithm combinations based on DNA damage response (DDR)-related genes. Gene set enrichment analysis (GSEA), somatic mutation profiling, and immune cell infiltration estimation via CIBERSORT were performed to characterize HRD-associated molecular features. RESULTS: High HRD scores were significantly associated with poorer overall survival (P<0.05). Among 112 algorithm combinations, the survival support vector machine (Survival-SVM) model demonstrated optimal performance [training concordance index (C-index): 0.741; test C-index: 0.708], identifying six hub genes: PARP1, MBD4, TELO2, NSMCE3, SMUG1, and BABAM1. A nomogram incorporating risk score (RS) and clinical variables achieved strong predictive accuracy for 1- to 3-year survival [area under the curve (AUC) >0.7]. High-HRD tumors exhibited distinct mutational patterns (TP53 and TTN) and enriched glutathione metabolism and cytochrome P450 pathways. Immune infiltration analysis revealed significant differences in plasma cell and neutrophil infiltration between risk groups (P<0.05), suggesting HRD-associated immune microenvironment remodeling. CONCLUSIONS: We developed a novel HRD-based prognostic model incorporating six DDR-related genes that demonstrates robust predictive performance in ESCC. HRD score is identified as an independent prognostic factor associated with genomic instability, immune microenvironment alterations, and clinical outcomes. These findings provide a theoretical basis for personalized treatment strategies, including potential applications of PARP inhibitors and immunotherapy in ESCC.

Esophageal squamous cell carcinoma (ESCC)↗

PubMed2006

Somatic mutations and activation-induced cytidine deaminase (AID) expression in established rheumatoid factor-producing lymphoblastoid cell line.

Epstein-Barr virus (EBV) transforms human peripheral B cells into lymphoblastoid cell lines (LCLs), allowing the production of specific antibody-secreting cell lines. We and others have previously found that in contrast to peripheral blood B cells, EBV-transformed lymphoblastoid cell lines express the activation-induced cytidine deaminase (AID) gene. The opposite is true for the germinal center-specific BCL6 gene: it is expressed in adult peripheral blood B cells and is no longer expressed in LCLs. The present work extends our findings and shows that whereas AID expression is rapidly induced following EBV infection, BCL6 expression is gradually down-regulated and is fully extinguished in already established LCLs. The question of whether AID activation induces the process of somatic hypermutation (SHM) was investigated in adult-derived LCLs. It was found that the VH gene from the rheumatoid factor-producing RF LCL (derived from a rheumatoid arthritis patient), accumulated somatic point mutations in culture. Overall, nine unique mutations have accumulated in the rearranged VH gene since the generation of the RF cell line. Four additional intraclonal mutations were found among 10 cellular clones of the RF cells. One out of the four was in CDR1 and could be correlated with loss of antigen-binding activity in three out of the 10 clones. Altogether, these 13 mutations were preferentially targeted to the DGYW motifs and showed preference for CG nucleotides, indicating that they were AID-mediated. By contrast, mutations were not detected among 3700-4000 nucleotides each of the Vlambda, Cmu and GAPDH genes derived from the same RF cell cultures and the cellular clones. Our results thus show that AID may generate point mutations in the rearranged Ig VH during in vitro cell culture of adult-LCLs and that these mutations may be responsible, at least in part, for the known instability and occasional loss of antigen-binding activity of antibody-secreting LCLs.

Amino Acid Sequence↗

PubMed2026

Selective Inhibition of DNA Polymerase Proofreading: A Metabolic-Fidelity Mechanism Explains Agent Orange-Associated Myelodysplasia.

We performed a focused review to better understand the pathogenesis of Agent Orange (AO)-associated myelodysplastic syndrome (MDS). We first examined the mechanisms underlying conventional (de novo) MDS, a clonal hematopoietic neoplasm that typically develops in later life, and integrated these findings with our recent analysis of obesity-associated carcinogenesis. Accordingly, we propose that genomic instability in de novo MDS results from selective inhibition of the DNA polymerase proofreading exonuclease. In obesity-associated carcinogenesis, impaired AMP-activated protein kinase (AMPK) activity disrupts mitochondrial ATP production, increasing intracellular AMP concentrations. Elevated AMP selectively inhibits the proofreading exonuclease while preserving polymerase activity, allowing replication errors to escape correction and become fixed as somatic mutations. Molecular studies demonstrate that AO-associated MDS exhibits essentially the same mutational profile as de novo disease despite arising after 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure in young, otherwise healthy military personnel. Because TCDD is highly lipophilic, it accumulates in adipose tissue and is released slowly over decades, producing sustained mitochondrial dysfunction, reduced ATP synthesis, and chronic elevation of intracellular AMP. We propose that this metabolic disturbance converges on the same endpoint-selective inhibition of the proofreading exonuclease-thereby promoting mutagenesis and clonal evolution. Recent studies further strengthen the central role of proofreading by demonstrating that many mutations, including many found in MDS, previously attributed to spontaneous cytosine deamination, instead arise from DNA polymerase misincorporation of thymidine opposite cytosine, particularly at CpG dinucleotides, emphasizing the critical importance of fully active proofreading in preventing such misincorporations from accumulating as mutations in the genome of the cell.

AMP↗

PubMed2000

Detection of somatic DNA alterations in azoxymethane-induced F344 rat colon tumors by random amplified polymorphic DNA analysis.

Colon carcinogenesis induced in rats by azoxymethane (AOM) is a useful experimental model as it mimics the human adenoma-carcinoma sequence and allows the study of dietary variation and of the effects of chemopreventive substances. Alterations of specific oncogenes and tumor suppressor genes (APC and K-ras) play roles at different stages of this carcinogenesis process. Recently, it has been suggested that genomic instability is the necessary step for the generation of multiple mutations underlying the occurrence of cancer. We studied the frequency of K-ras and microsatellite instability (MSI) in 30 colorectal tumors induced by AOM (30 mg/kg) in F344 rats. We also used the random amplified polymorphic DNA (RAPD) method to identify genomic alterations in chemically induced aberrant crypt foci (ACF), adenomas and adenocarcinomas. K-ras mutations were identified in 16.7% of the cases (5/30; 9% in adenomas and 37.5% in adenocarcinomas) and MSI in 20% (6/30) of the tumors (only one sample exhibited instability at more than one locus). Of 21 primers used for the RAPD assay, six were very informative. All the analyzed tumors (16/16) showed at least one RAPD profile with lost or additional bands compared with the normal mucosa. A lower level of genomic alteration was present in the ACF analyzed (7/10). In conclusion, K-ras and MSI are not often involved in the AOM carcinogenesis in the rat, whereas extensive genomic instability is always present and can be detected using the RAPD analysis.

Adenocarcinoma↗

PubMed2000

Ontogeny of telomerase in chicken: impact of downregulation on pre- and postnatal telomere length in vivo.

Telomeres are the termini of linear chromosomes composed of tandem repeats of a conserved DNA sequence. Telomerase provides a mechanism for proliferating cells to offset telomeric sequence erosion by synthesizing new repeats onto the end of each parental DNA strand. Reduced or absent telomerase activity can lead to telomere shortening and genome instability. Telomeres and telomerase have not previously been characterized during ontogeny of any avian species. In the present study, telomerase activity in the chicken model was examined from early differentiation embryos through to adulthood. Telomerase activity was detected in all early embryos (preblastula through neurula) and in tissues throughout organogenesis. Subsequently, telomerase was downregulated in the majority of somatic tissues, either pre- or postnatally. A subset of tissues, such as intestine, immune and reproductive organs, exhibited constitutive activity. The impact of telomerase downregulation on telomere length was investigated and a telomere reduction of 3.2 kb in somatic tissues compared with germ line was observed in 5-year-old adults. The present results suggest that the telomere clock function is a conserved feature of avians as well as mammals. Knowledge regarding the relationships among telomerase regulation, proliferation/senescence profiles and differentiation status will be useful for numerous applications of chicken cells.

Animals↗

PubMedDate not supplied

Oncogenic pathway of sporadic colorectal cancer with novel germline missense mutations in the hMSH2 gene.

The deficiency of the DNA mismatch repair (MMR) system is involved in tumorigenesis of either familial or sporadic colorectal cancers showing microsatellite instability (MSI). To investigate the involvement of the mutated hMSH2 gene in carcinogenesis, we searched for alteration of the gene in 15 MSI tumors of Japanese patients with sporadic colorectal cancer by a polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) and DNA sequencing analyses. We found 20 alterations including 7 novel mutations, 6 germline and one somatic. To assume an oncogenic pathway of tumor of two patients carrying germline missense mutations, G40S located in an evolutionarily conserved amino-terminal motif and Y619C in a domain interacting with either hMSH3 or hMSH6, somatic mutations in 9 target genes of the MMR defect and in the p53 and K-ras genes and loss of heterozygosity (LOH) at the hMLH1 and p53 gene loci were then studied. In the tumor carrying G40S, other somatic hMSH2 mutations, G203R and 687delA in the (A)(7) repeat, and 5 one-bp deletions in the target genes were found, while no mutation in the p53 and K-ras genes. These results indicate that G40S may affect the hMSH2 function and the tumor may be developed by a typical MSI pathway. In another tumor with Y619C, LOH at the hMLH1 gene locus, no mutation in MMR target genes, and two-hit inactivation of the p53 gene were detected. This MSI tumor seems to be developed by another than MSI pathway. These results indicate that there are different oncogenic pathways in the MSI sporadic colorectal cancers with germline missense mutations in the hMSH2 gene. We conclude that familial colorectal cancer-suspected cases exist in a small population of sporadic colorectal cancers.

Amino Acid Sequence↗

PubMed2001

Genetic predisposition and somatic diversification in tumor development and progression.

Studies on human cancer predisposition syndromes have contributed significantly to our understanding on tumor initiation and progression. Work performed on hereditary colon cancer has been particularly fruitful. Much of the molecular background of the various intestinal polyposis syndromes, such as familial adenomatous polyposis (FAP), juvenile polyposis, and Peutz-Jeghers syndrome, has been revealed, pinpointing several key cancer-associated genes. Studies on hereditary nonpolyposis colorectal cancer (HNPCC) have revealed a novel mechanism of tumorigenesis; genomic instability caused by defective DNA mismatch repair (MMR). Understanding the molecular background of these diseases helps us to understand tumor initiation in the affected individuals. Relatively little is known about the details of tumor progression in hereditary and sporadic neoplasia. Certain additional gene mutations can be associated with advancing stages of the disease, but the pace and tempo of the process have remained obscure. A high mutation rate in MMR-deficient tumors has provided a new approach in the analysis of human tumor dynamics. Microsatellite (MS) sequences are frequently mutated in MMR deficient tumors. The high mutation rate allows the use of microsatellite mutations as a tool for analyzing the past patterns of tumor progression. This approach is similar to the use of MS mutations in studying human evolution and migrations. Such tumor studies have revealed progression pathways that differ from the classic adenoma-cancer sequence. The reasons why and how molecular clocks may reveal something new about a well-studied problem are discussed.

Animals↗

PubMed2006

High-resolution analysis of chromosomal breakpoints and genomic instability identifies PTPRD as a candidate tumor suppressor gene in neuroblastoma.

Although neuroblastoma is characterized by numerous recurrent, large-scale chromosomal imbalances, the genes targeted by such imbalances have remained elusive. We have applied whole-genome oligonucleotide array comparative genomic hybridization (median probe spacing 6 kb) to 56 neuroblastoma tumors and cell lines to identify genes involved with disease pathogenesis. This set of tumors was selected for having either 11q loss or MYCN amplification, abnormalities that define the two most common genetic subtypes of metastatic neuroblastoma. Our analyses have permitted us to map large-scale chromosomal imbalances and high-level amplifications at exon-level resolution and to identify novel microdeletions and duplications. Chromosomal breakpoints (n = 467) generating imbalances >2 Mb were mapped to intervals ranging between 6 and 50 kb in size, providing substantial information on each abnormality. For example, breakpoints leading to large-scale hemizygous loss of chromosome 11q were highly clustered and preferentially associated with segmental duplications. High-level amplifications of MYCN were extremely complex, often resulting in a series of discontinuous regions of amplification. Imbalances (n = 540) <2 Mb long were also detected. Although the majority (78%) of these imbalances mapped to segmentally duplicated regions and primarily reflect constitutional copy number polymorphisms, many subtle imbalances were detected that are likely somatically acquired alterations and include genes involved with tumorigenesis, apoptosis, or neural cell differentiation. The most frequent microdeletion involved the PTPRD locus, indicating a possible tumor suppressor function for this gene.

Cell Line, Tumor↗

PubMed2002

Variability of X chromosome inactivation: effect on levels of TIMP1 RNA and role of DNA methylation.

X chromosome inactivation results in dosage equivalency for X-linked gene expression between males and females. However, some X-linked genes show variable X inactivation, being expressed from the inactive X in some females but subject to inactivation in other women. The human tissue inhibitor of metalloproteinases-1 ( TIMP1) gene falls into this category. As TIMP1 and its target metalloproteinases are involved in many biological processes, women with elevated TIMP1 expression may exhibit different disease susceptibilities. To address the potential impact of variable X inactivation, we analyzed TIMP1 expression levels by using an RNase protection assay. The substantial variation of TIMP1 expression observed in cells with monoallelic TIMP1 expression precluded analysis of the contribution of the inactive X to total TIMP1 RNA levels in females, so we examined expression in rodent/human somatic cell hybrids. TIMP1 expression levels varied more widely in hybrids retaining an inactive X than in those with an active X chromosome, suggesting variable retention of the epigenetic silencing mechanisms associated with X inactivation. Therefore, we investigated the contribution of methylation at the promoter to expression level variation and found that methylation of the TIMP1 promoter correlated with instability and low level expression, whereas stable TIMP1expression from the inactive X equivalent to that seen from the active X chromosome was observed when the promoter was unmethylated. Since all female cell lines examined showed methylation of the TIMP1 promoter, the contribution of expression from the inactive X appears minimal. However, as women age, they may accumulate cells stably expressing TIMP1 from the inactive X, with a resulting increase of TIMP1, which may explain some sex differences in various late-onset disorders.

Aging↗

PubMed2004

[Analysis of the frequency of spontaneous aneuploidy in human somatic cells using interphase cytogenetic technology].

The frequency of spontaneous aneuploidy of the four autosomes and sex chromosomes in the interphase nuclei of cultivated and uncultured lymphocytes from clinically healthy men was examined by use of two-color fluorescent in situ hybridization (FISH). It was shown that in uncultured cells from the individuals examined autosomal nullosomies were practically not detected (the frequency 0 to 0.01%). At the same time, the frequency of such cells with either Y, or X nullosomy was at least an order of magnitude higher (about 0.15%). This frequency was comparable with the level of Y- or X-disomic cells, and also with autosomal monosomies, precluding from considering the X-nullosomic cells as hybridization artifacts. During lymphocyte cultivation, a statistically significant increase in the total frequency of Y- or X-nullosomic cells was observed already after the first cell division cycle. Thus, interphase FISH analysis is a sufficiently sensitive method enabling detection of higher, compared to the autosomes, loss of sex chromosomes in the process of cell division, a phenomenon observed during replicative cell aging, as well as during natural aging of the organism. Male cells with the de novo lost singular X chromosome, probably, switch to apoptosis and do not survive during further life of a cell population. The frequency of total aneuploidy in human somatic cells with the correction for the resolution capacity of the interphase FISH analysis constituted 5.62 and 6.90% for uncultured and cultivated cells, respectively. This aneuploidy level is close to that in spermatozoa. The data obtained can serve as the basis for the examination of the aneugenic (aneuploidy-inducing) genotoxic effects and for the analysis of interindividual genetic instability.

Aneuploidy↗

PubMed1995

Histological conversion of follicular lymphoma with structural alterations of t(14;18) and immunoglobin genes.

About half of the patients with follicular lymphoma will develop an aggressive B cell lymphoma with morphological changes in growth pattern and cellular morphology. Changes of the immunophenotype, especially of the expression of immunoglobulin (Ig) have been documented less frequently. Multiple tumor samples of two patients with follicular lymphoma who developed tumor progression, were studied by Southern blot analysis for rearrangements of the Ig genes and the oncogenes BCL2 and MYC. In both patients, the general pattern of Ig gene rearrangements, especially of the Ig light-chain genes, and the structure of the t(14;18) breakpoint as assessed by the polymerase chain reaction (PRC) and fine restriction mapping, remained unaltered with time. However, both within the functional Ig heavy-chain allele and around the t(14;18) breakpoint, extensive secondary alterations took place. This indicates clonal evolution rather than the appearance of an independent lymphoma. In the first case with progression from follicular lymphoma to Burkitt's lymphoma 3 years after diagnosis, alterations were especially present 3' of the t(14;18) breakpoint. In the second patient with a change from follicular to diffuse centroblastic lymphoma 4 years after diagnosis, subsequent class switches from IgM to IgG and to defective IgH expression were accompanied by deletion of C mu sequences and a rearrangement of the MYC gene, respectively. Additionally, in both patients alterations in individual restriction sites occurred, which most likely were due to somatic mutations within both the functional IgH and translocated allele. Our data indicate that complex alterations of both the functional and non-functional IgH allele may accompany tumor progression and may erroneously suggest the appearance of independent clones by Southern blot analysis. It remains to be established whether these alterations are causative events or the consequence of genetic instability and clonal evolution.

Adult↗

PubMedDate not supplied

DNA organization in human spermatozoa.

Previous studies from this laboratory on hamster spermatozoa have demonstrated that rodent sperm DNA is packaged into the sperm nucleus in a specific manner by nuclear structures. The entire genome is organized into DNA loop domains attached at their bases to a sperm nuclear matrix, the skeletal structure of the nucleus. When nuclei are completely decondensed, the nuclear matrix dissipates, and the entire genome remains anchored to a single structure located at the base of the tail, termed the nuclear annulus. Here, we have extended these studies to human sperm nuclei, which were found to be similar to hamster. Human sperm DNA was found to be organized into loop domains attached at their bases to a nuclear matrix. The average size of the human sperm halo of DNA surrounding the extracted sperm nucleus (made up of DNA loop domains) was about 50% smaller than those that have been reported for somatic cells (this corresponds to an approximate loop domain size of 26.8 +/- 2.1 kb). Human sperm DNA also remained anchored to the base of the tail when completely decondensed, indicating the existence of a nuclear annulus-like structure in human spermatozoa; but, unlike the hamster nuclear annulus, the human annulus could not be isolated because of its structural instability when separated from the tail. Using human centromere repeats as a probe for in situ hybridization, we examined the packaging of individual DNA sequences within the sperm nucleus. These studies demonstrate that human sperm DNA is highly organized by nuclear structures.

Adult↗

PubMed1985

Evidence for chromosome instability in vivo in Bloom syndrome: increased numbers of micronuclei in exfoliated cells.

The incidence of exfoliated epithelial cells containing micronuclei was determined in two small human populations, one homozygous and the other heterozygous for the Bloom syndrome gene (bl). The objectives of the study were two: to learn whether the chromosome instability featured so prominently by Bloom syndrome (BS) cells proliferating in vitro also occurs in vivo, and as part of a broad survey of various cancer-prone populations, to determine whether estimating micronucleus frequencies in exfoliated cell samples might be useful for identifying individuals with genetically determined chromosome instability. Eight individuals homozygous (bl/bl) for the BS gene, i.e., persons with the clinical syndrome, were examined, along with 11 obligate heterozygotes (bl/+), parents of affected persons. Exfoliated cells were obtained from two sites, the oral cavity and the urinary tract. Striking and statistically highly significant elevations in the frequencies of cells with micronuclei were observed in cells from both sites in bl/bl individuals compared to that in bl/+ (P less than 0.001) and in a control population, indicating that chromosome instability occurs in vivo in BS. In contrast, micronucleus frequencies at either site did not differ significantly between bl/+ individuals and the control population. This survey, in combination with similar earlier ones of populations predisposed to cancer not on a genetic basis but because of exposure to some environmental carcinogen, suggests that the exfoliated cell micronucleus test identifies individuals whose somatic genetic material has, for either genetic or environmental reasons, been damaged in a way that produces chromosome breakage and rearrangement.

Adult↗

PubMed2002

Understanding the hypercarcinogenic state in chronic hepatitis: a clue to the prevention of human hepatocellular carcinoma.

Human hepatocellular carcinomas (HCCs) are preceded by chronic hepatitis and cirrhosis. Despite a clear viral etiology (hepatitis B virus [HBV] and hepatitis C virus [HCV] of human hepatocarcinogenesis, the mechanism is complex and the distinct molecular pathway or molecules that explain this phenomenon are not yet known. Viral hepatitis, "inflammation-mediated" hepatocarcinogenesis, greatly influences the incidence of somatic genetic events in hepatocytes, by increasing the number of target cells or the proliferation of once-hit hepatocytes, eventually leading to HCC. We propose that hepatitis virus can cause HCC by a combination of two mechanisms; (i) cell killing and stimulation of mitosis, leading to an accumulation of events necessary for transformation; and (ii) an increase in chromosomal instability mediated by induced recombinogeneic protein(s) during chronic hepatitis. These conditions may be designated as the "hypercarcinogenic state". Our goal is to change the "hypercarcinogenic state" to the "normo- or hypocarcinogenic" state and to prevent HCC development.

Carcinoma, Hepatocellular↗

PubMed2001

Microsatellite instability, PTEN and p53 germline mutations in glioma families.

Rare inherited syndromes that to some extent explain familial glioma include Turcot's syndrome, Li-Fraumeni syndrome and neurofibromatosis types I and II. The majority of families with glioma do not meet the clinical criteria for any of these syndromes. In order to study the genetic origin of familial glioma, tumour DNA (n = 35) or blood samples (n = 8) were collected from 25 families. The glioma tumours were tested for microsatellite instability (MSI) with two markers, BAT25 and BAT26, since glioma is associated with hereditary non-polyposis colon cancer (HNPCC) in Turcot's syndrome. Furthermore, p53 was screened from blood DNA (exons 2-11) with temporal temperature gradient electrophoresis (TTGE) since germline mutations in p53 are seen in Li-Fraumeni syndrome. In gliomas, there is a wide variety of somatic mutations, such as, for instance, in p53, the epidermal growth factor receptor (EGFR) and p16. The tumour suppressor gene PTEN is also often somatically mutated in glioma, therefore it is attractive as a candidate gene for germline mutations in familial glioma. Blood DNA was directly sequenced for mutations in PTEN exons 1-9. The analysis showed that no mutations were found in either of the studied tumour suppressor genes, and no MSI-positive tumours were found. A common polymorphism in p53 at codon 72 (arginine/proline) was found in 6/8 of the patients. Apparently, mutation in the tested tumour suppressor genes or DNA mismatch repair genes does not explain the familial glioma observed in these families.

Brain Neoplasms↗

PubMed2006

The mutation rate in PIG-A is normal in patients with paroxysmal nocturnal hemoglobinuria (PNH).

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the presence in the patient's hematopoietic system of a large cell population with a mutation in the X-linked PIG-A gene. Although this abnormal cell population is often found to be monoclonal, it is not unusual that 2 or even several PIG-A mutant clones coexist in the same patient. Therefore, it has been suggested that the PIG-A gene may be hypermutable in PNH. By a method we have recently developed for measuring the intrinsic rate of somatic mutations (mu) in humans, in which PIG-A itself is used as a sentinel gene, we have found that in 5 patients with PNH, mu ranged from 1.24 x 10(-7) to 11.2 x 10(-7), against a normal range of 2.4 x 10(-7) to 29.6 x 10(-7) mutations per cell division. We conclude that genetic instability of the PIG-A gene is not a factor in the pathogenesis of PNH.

Adult↗

PubMed2025

PUMA-induced apoptosis drives bone marrow failure and genomic instability in telomerase-deficient mice.

Bone marrow failure is a severe complication of human telomere biology disorders and predisposes individuals to secondary leukemia. A deeper understanding of this process could offer significant clinical benefits. Using a preclinical mouse model deficient in the RNA component of the telomerase (mTerc), we demonstrate that bone marrow failure results from excessive apoptosis, predominantly mediated by the pro-apoptotic p53 target PUMA. Genetic ablation of Puma alleviates hematological phenotypes and reduces the risk of lethal bone marrow failure while preserving genomic stability. Mechanistically, PUMA deficiency decreases the sensitivity of hematopoietic cells to lethal stressors, including critically short telomeres. As a consequence, reduced compensatory turnover of hematopoietic progenitors slows down telomere shortening at the population level, delays stem cell exhaustion, and diminishes the acquisition of somatic mutations - ultimately preventing neoplastic transformation. Elevated expression of both p53 and PUMA is also observed in the bone marrow from patients with telomere biology disorders. While apoptosis resistance is traditionally associated with malignant transformation, our findings provide evidence that selective inhibition of PUMA-mediated apoptosis may represent a viable therapeutic strategy to prevent or delay leukemic transformation in this patient population.

Animals↗