Chromosome breakage syndromes and cancer

Epstein-Barr virus-associated leiomyosarcoma of the larynx in an adult patient with human immunodeficiency virus infection: Case report and review of the literature

We investigated the clinical features, treatment, and prognosis of laryngeal leiomyosarcoma (LLMS) and Epstein-Barr virus-associated (EBV-associated) LMS. We report a case of EBV-associated LLMS in an adult patient with HIV infection. We also conducted a review of the English-language literature on LLMS and EBV-associated leiomyosarcoma. To the best of our knowledge, 62 cases of LLMS and EBV-associated leiomyosarcoma have been reported to date. Of patients with LLS, 18.9% had distant metastases and 17.0% had local recurrence. The overall 5-year survival rate was 64.0%. Distant metastases affected the survival of patients with LLMS (p = 0.04). EBV-positive patients had a low survival rate (p = 0.01). Among patients with EBV-associated LMS, 8.2% had distant metastases and recurrence and the overall 5-year survival rate was 50.0%. EBV-associated LLMS is rare. The EBV infection might be a poor prognostic factor of LLMS.

Quantitative Correlations between Radiosensitivity Biomarkers Show That the ATM Protein Kinase Is Strongly Involved in the Radiotoxicities Observed after Radiotherapy

Tissue overreactions (OR), whether called adverse effects, radiotoxicity, or radiosensitivity reactions, may occur during or after anti-cancer radiotherapy (RT). They represent a medical, economic, and societal issue and raise the question of individual response to radiation. To predict and prevent them are among the major tasks of radiobiologists. To this aim, radiobiologists have developed a number of predictive assays involving different cellular models and endpoints. To date, while no consensus has been reached to consider one assay as the best predictor of the OR occurrence and severity, radiation oncologists have proposed consensual scales to quantify OR in six different grades of severity, whatever the organ/tissue concerned and their early/late features. This is notably the case with the Common Terminology Criteria for Adverse Events (CTCAE). Few radiobiological studies have used the CTCAE scale as a clinical endpoint to evaluate the statistical robustness of the molecular and cellular predictive assays in the largest range of human radiosensitivity. Here, by using 200 untransformed skin fibroblast cell lines derived from RT-treated cancer patients eliciting OR in the six CTCAE grades range, correlations between CTCAE grades and the major molecular and cellular endpoints proposed to predict OR (namely, cell survival at 2 Gy (SF2), yields of micronuclei, recognized and unrepaired DSBs assessed by immunofluorescence with γH2AX and pATM markers) were examined. To our knowledge, this was the first time that the major radiosensitivity endpoints were compared together with the same cohort and irradiation conditions. Both SF2 and the maximal number of pATM foci reached after 2 Gy appear to be the best predictors of the OR, whatever the CTCAE grades range. All these major radiosensitivity endpoints are mathematically linked in a single mechanistic model of individual response to radiation in which the ATM kinase plays a major role.

BRUCE preserves genomic stability in the male germline of mice

BRUCE is a DNA damage response protein that promotes the activation of ATM and ATR for homologous recombination (HR) repair in somatic cells, making BRUCE a key protector of genomic stability. Preservation of genomic stability in the germline is essential for the maintenance of species. Here, we show that BRUCE is required for the preservation of genomic stability in the male germline of mice, specifically in spermatogonia and spermatocytes. Conditional knockout of Bruce in the male germline leads to profound defects in spermatogenesis, including impaired maintenance of spermatogonia and increased chromosomal anomalies during meiosis. Bruce-deficient pachytene spermatocytes frequently displayed persistent DNA breaks. Homologous synapsis was impaired, and nonhomologous associations and rearrangements were apparent in up to 10% of Bruce-deficient spermatocytes. Genomic instability was apparent in the form of chromosomal fragmentation, translocations, and synapsed quadrivalents and hexavalents. In addition, unsynapsed regions of rearranged autosomes were devoid of ATM and ATR signaling, suggesting an impairment in the ATM- and ATR-dependent DNA damage response of meiotic HR. Taken together, our study unveils crucial functions for BRUCE in the maintenance of spermatogonia and in the regulation of meiotic HR-functions that preserve the genomic stability of the male germline.

Functional Assays for Individual Radiosensitivity: A Critical Review

A complete understanding of the mechanisms of the response to radiation would help in a better evaluation of the radiation-induced risks. To this aim, individual radiosensitivity, that is, the proneness to radiation-induced tissue reactions attributable to cell death, has been documented since the beginning of the 20th century. For several decades, developing informative predictive assays has been one of the most important challenges of radiobiologists. This article is a critical review devoted to the major functional assays to predict radiosensitivity and their strengths and weaknesses, notably those based on the quantification of clonogenic cell survival, micronuclei, p21 expression, apoptosis, chromosome and DNA repair, and signaling. Genomic approaches of radiosensitivity are reviewed in another article of this issue.

Frontline treatment of acute myeloid leukemia in adults

Recent years have highlighted significant progress in understanding the underlying genetic and epigenetic signatures of acute myeloid leukemia(AML). Most importantly, novel chemotherapy and targeted strategies have led to improved outcomes in selected genetic subsets. AML is a remarkably heterogeneous disease, and individualized therapies for disease-specific characteristics (considering patients' age, cytogenetics, and mutations) could yield better outcomes. Compared with the historical 5-to 10-year survival rate of 10%, the survival of patients who undergo modern treatment approaches reaches up to 40-50%, and for specific subsets, the improvements are even more dramatic; for example, in acute promyelocytic leukemia, the use of all-trans retinoic acid and arsenic trioxide improved survival from 30 to 40% up to 80 to 90%. Similar progress has been documented in core-binding-factor-AML, with an increase in survival from 30% to 80% upon the use of high-dose cytarabine/fludarabine/granulocyte colony-stimulating factor combination regimens. AML treatment was also recently influenced by the discovery of the superiority of regimens with higher dose Ara-C and nucleoside analogues compared with the "7+3"regimen, with about a 20% improvement in overall survival. Despite these significant differences, most centers continue to use the "7+3" regimen, and greater awareness will improve the outcome. The discovery of targetable molecular abnormalities and recent studies of targeted therapies (gemtuzumab ozagomycin, FLT3 inhibitors, isocitrate dehydrogenase inhibitors, and epigenetic therapies), future use of checkpoint inhibitors and other immune therapies such as chimeric antigen receptor T-cells, and maintenance strategies based on the minimal residual disease evaluation represent novel, exciting clinical leads aimed to improve AML outcomes in the near future.

Individual response to ionizing radiation

The human response to ionizing radiation (IR) varies among individuals. The first evidence of the individual response to IR was reported in the beginning of the 20th century. Considering nearly one century of observations, we here propose three aspects of individual IR response: radiosensitivity for early or late adverse tissue events after radiotherapy on normal tissues (non-cancer effects attributable to cell death); radiosusceptibility for IR-induced cancers; and radiodegeneration for non-cancer effects that are often attributable to mechanisms other than cell death (e.g., cataracts and circulatory disease). All the molecular and cellular mechanisms behind IR-induced individual effects are not fully elucidated. However, some specific assays may help their quantification according to the dose and to the genetic status. Accumulated data on individual factors have suggested that the individual IR response cannot be ignored and raises some clinical and societal issues. The individual IR response therefore needs to be taken into account to better evaluate the risks related to IR exposure.

Targeting homologous recombination, new pre-clinical and clinical therapeutic combinations inhibiting RAD51

The DNA damage response (DDR) is essential for maintaining genomic stability and cell survival. However, when tumour cells with deficiencies in HR are faced with radio- and chemotherapies they are forced to rely on error-prone, alternative repair pathways or aberrant HR for survival; threatening genome integrity and driving further mutation. Accurate therapeutic targeting of the key drivers of DNA repair can circumvent survival pathways and avoid aggressive therapy resistant mutants. Several studies have identified that stabilization of the cancer genome in HR deficient cells can be achieved by overexpression of the recombinase RAD51. Radio- and chemotherapeutic resistance is associated with overactive HR repair mechanisms. However no clinical trials have directly targeted RAD51, despite RAD51 displaying synergy in several drug screens against multiple cancer types. Currently synthetic lethality targeting the DDR pathways and HR deficiency has had clinical success with BRCA1 functional loss and PARP inhibition. In this review we suggest that clinical outcomes could be improved by additionally targeting RAD51. We examine the latest developments in directly and indirectly targeting RAD51. We scrutinize the potential treatment efficacy and future clinical applications of RAD51 inhibitors as single agents and in combination with other therapies and consider the best therapeutic options.

Pulmonary function in children and young adults with ataxia telangiectasia

BACKGROUND

Pulmonary disease contributes to significant morbidity and mortality in people with ataxia telangiectasia (A-T). To determine the association between age and lung function in children and young adults with A-T and to identify factors associated with decreased lung function, pulmonary function tests were performed in 100 consecutive people with A-T.

METHODS

Children and adults ranging from 6 to 29 years of age and with the diagnosis of A-T were recruited, and underwent pulmonary function tests.

RESULTS

The mean forced vital capacity % predicted (FVC %) in the population was 56.6 ± 20.0. Males and females between 6 and 10 years of age had similar pulmonary function. Older females were found to have significantly lower FVCs % than both older males (P < 0.02) and younger females (P < 0.001). The use of supplemental gamma globulin was associated with significantly lower FVC %. A modest correlation was found between higher radiation-induced chromosomal breakage and lower FVC % in males. No significant change in FVC % was found in a subset of subjects (n = 25) who underwent pulmonary function testing on two or more occasions over an average of 2 years.

CONCLUSION

In children and young adults with A-T, older females and people who required supplemental gamma globulin had significantly lower lung function by cross-sectional analysis. Stable lung function is possible over a 2-year period. Recognition of groups who are at higher risk for lower pulmonary function may help direct care and improve clinical outcomes in people with A-T.

Intratumour diversity of chromosome copy numbers in neuroblastoma mediated by on-going chromosome loss from a polyploid state

Neuroblastomas (NBs) are tumours of the sympathetic nervous system accounting for 8–10% of paediatric cancers. NBs exhibit extensive intertumour genetic heterogeneity, but their extent of intratumour genetic diversity has remained unexplored. We aimed to assess intratumour genetic variation in NBs with a focus on whole chromosome changes and their underlying mechanism. Allelic ratios obtained by SNP-array data from 30 aneuploid primary NBs and NB cell lines were used to quantify the size of clones harbouring specific genomic imbalances. In 13 cases, this was supplemented by fluorescence in situ hybridisation to assess copy number diversity in detail. Computer simulations of different mitotic segregation errors, single cell cloning, analysis of mitotic figures, and time lapse imaging of dividing NB cells were used to infer the most likely mechanism behind intratumour variation in chromosome number. Combined SNP array and FISH analyses showed that all cases exhibited higher inter-cellular copy number variation than non-neoplastic control tissue, with up to 75% of tumour cells showing non-modal chromosome copy numbers. Comparisons of copy number profiles, resulting from simulations of different segregation errors to genomic profiles of 120 NBs indicated that loss of chromosomes from a tetraploid state was more likely than other mechanisms to explain numerical aberrations in NB. This was supported by a high frequency of lagging chromosomes at anaphase and polyploidisation events in growing NB cells. The dynamic nature of numerical aberrations was corroborated further by detecting substantial copy number diversity in cell populations grown from single NB cells. We conclude that aneuploid NBs typically show extensive intratumour chromosome copy number diversity, and that this phenomenon is most likely explained by continuous loss of chromosomes from a polyploid state.

Evidence for exposure-induced DNA repair abnormality is indicative of health and genetic risk

A recent focus has been targeted toward the development of functional biomarkers that can be used to predict disease more reliably. One such biomarker is the challenge assay for DNA repair deficiency. Briefly, the assay involves challenging lymphocytes in culture to a DNA damaging agent in vitro and determining the repair outcome in chromosome aberrations and/or DNA strand breaks. The aim is to show that individuals who have chronic exposure to toxic substances will develop exposure-induced DNA repair deficiencies. Many studies around the world have shown that the assay detects DNA repair deficiency in environmentally/occupationally exposed populations and with significant exposure dose-response relationship. The prediction of health risk was also validated. In addition, exposure-induced repair deficiency which was apparently passed through the germ cells had caused genetic consequences in a 3-generation population. The assay is simple to conduct and is more sensitive than some traditional biomarker assays. Together with the functional significance of the assay, the challenge assay can be used with confidence in population studies for health risk assessment.

Chromosomal aberrations in peripheral blood lymphocytes in patients with newly diagnosed celiac and Crohn's disease

OBJECTIVES

The aims of this research were to determine the number of chromosomal aberrations in peripheral blood lymphocytes and to evaluate the number of circulating lymphocytes with CD103, integrin expressed on intraepithelial lymphocytes and preserved in enteropathy-associated T-cell lymphoma, in patients with newly diagnosed Crohn's disease, celiac disease, and healthy controls.

METHODS

During the period of 30 months, we included 44 patients. Chromosome aberrations were analyzed in peripheral blood lymphocytes by a single cytogeneticist. Multicolor flow cytometric was used for immunophenotyping of peripheral blood lymphocytes.

RESULTS

We found a significantly higher number of chromosomal aberrations/100 metaphases in the celiac and Crohn's disease group compared with the controls (P=0.01) and they also had a significantly higher number of aberrant cells compared with the controls (P<0.001). There was no statistically significant difference between the groups with respect to the percentage of CD103+ and CD8+CD103+ cells between groups (P=0.16 and 0.41, respectively) and no correlation between the total number of chromosomal aberrations and the percentage of CD103+ and CD8+CD103+ cells (P=0.06 and 0.06, respectively).

CONCLUSION

Patients with active celiac and newly diagnosed Crohn's disease, before treatment initiation, have a significantly increased number of chromosomal aberrations in peripheral blood lymphocytes. No dissemination of intraepithelial cells in the blood and correlation to the chromosomal aberration was found.

Genetic instability: tipping the balance

Tumor cells typically contain a genome that is highly divergent from the genome of normal, non-transformed cells. This genetic divergence is caused by a number of distinct changes that the tumor cell acquires during its transformation from a normal cell into a tumorigenic counterpart. Changes to the genome include mutations, deletions, insertions, and also gross chromosomal aberrations, such as chromosome translocations and whole chromosome gains or losses. This genetic disorder of the tumor cell has complicated the identification of crucial driver mutations that cause cancer. Moreover, the large genetic divergence between different tumors causes them to behave very differently, and makes it difficult to predict response to therapy. In addition, tumor cells are genetically unstable and frequently acquire new mutations and/or gross chromosomal aberrations as they divide. This is beneficial for the overall capacity of a tumor to adapt to changes in its environment, but newly acquired genetic alterations can also compromise the genetic dominance of the tumor cell and thus affect tumor cell viability. Here, we review the mechanisms that can cause gross chromosomal aberrations, and discuss how these affect tumor cell viability.

From yeast to mammals: recent advances in genetic control of homologous recombination

Misregulation of DNA repair is associated with genetic instability and tumorigenesis. To preserve the integrity of the genome, eukaryotic cells have evolved extremely intricate mechanisms for repairing DNA damage. One type of DNA lesion is a double-strand break (DSB), which is highly toxic when unrepaired. Repair of DSBs can occur through multiple mechanisms. Aside from religating the DNA ends, a homologous template can be used for repair in a process called homologous recombination (HR). One key step in committing to HR is the formation of Rad51 filaments, which perform the homology search and strand invasion steps. In S. cerevisiae, Srs2 is a key regulator of Rad51 filament formation and disassembly. In this review, we highlight potential candidates of Srs2 orthologues in human cells, and we discuss recent advances in understanding how Srs2's so-called "anti-recombinase" activity is regulated.

Biological complexities in radiation carcinogenesis and cancer radiotherapy: impact of new biological paradigms

Although radiation carcinogenesis has been shown both experimentally and epidemiologically, the use of ionizing radiation is also one of the major modalities in cancer treatment. Various known cellular and molecular events are involved in carcinogenesis. Apart from the known phenomena, there could be implications for carcinogenesis and cancer prevention due to other biological processes such as the bystander effect, the abscopal effect, intrinsic radiosensitivity and radioadaptation. Bystander effects have consequences for mutation initiated cancer paradigms of radiation carcinogenesis, which provide the mechanistic justification for low-dose risk estimates. The abscopal effect is potentially important for tumor control and is mediated through cytokines and/or the immune system (mainly cell-mediated immunity). It results from loss of growth and stimulatory and/or immunosuppressive factors from the tumor. Intrinsic radiosensitivity is a feature of some cancer prone chromosomal breakage syndromes such as ataxia telangectiasia. Radiosensitivity is manifested as higher chromosomal aberrations and DNA repair impairment is now known as a good biomarker for breast cancer screening and prediction of prognosis. However, it is not yet known whether this effect is good or bad for those receiving radiation or radiomimetic agents for treatment. Radiation hormesis is another major concern for carcinogenesis. This process which protects cells from higher doses of radiation or radio mimic chemicals, may lead to the escape of cells from mitotic death or apoptosis and put cells with a lower amount of damage into the process of cancer induction. Therefore, any of these biological phenomena could have impact on another process giving rise to genome instability of cells which are not in the field of radiation but still receiving a lower amount of radiation. For prevention of radiation induced carcinogenesis or risk assessment as well as for successful radiation therapy, all these phenomena should be taken into account.

Genomic instability in breast and ovarian cancers: translation into clinical predictive biomarkers

Breast and ovarian cancer are among the most common malignancies diagnosed in women worldwide. Together, they account for the majority of cancer-related deaths in women. These cancer types share a number of features, including their association with hereditary cancer syndromes caused by heterozygous germline mutations in BRCA1 or BRCA2. BRCA-associated breast and ovarian cancers are hallmarked by genomic instability and high sensitivity to DNA double-strand break (DSB) inducing agents due to loss of error-free DSB repair via homologous recombination (HR). Recently, poly(ADP-ribose) polymerase inhibitors, a new class of drugs that selectively target HR-deficient tumor cells, have been shown to be highly active in BRCA-associated breast and ovarian cancers. This finding has renewed interest in hallmarks of HR deficiency and the use of other DSB-inducing agents, such as platinum salts or bifunctional alkylators, in breast and ovarian cancer patients. In this review we discuss the similarities between breast and ovarian cancer, the hallmarks of genomic instability in BRCA-mutated and BRCA-like breast and ovarian cancers, and the efforts to search for predictive markers of HR deficiency in order to individualize therapy in breast and ovarian cancer.

Chromosomes and cancer cells

Two prominent features of cancer cells are abnormal numbers of chromosomes (aneuploidy) and large-scale structural rearrangements of chromosomes. These chromosome aberrations are caused by genomic instabilities inherent to most cancers. Aneuploidy arises through chromosomal instability (CIN) by the persistent loss and gain of whole chromosomes. Chromosomal rearrangements occur through chromosome structure instability (CSI) as a consequence of improper repair of DNA damage. The mechanisms that cause CIN and CSI differ, but the phenotypic consequences of aneuploidy and chromosomal rearrangements may overlap considerably. Both CIN and CSI are associated with advanced stage tumors with increased invasiveness and resistance to chemotherapy, indicating that targeted inhibition of these instabilities might slow tumor growth. Here, we review recent efforts that define the mechanisms and consequences of CIN and CSI.

High prevalence of primary ovarian insufficiency in girls and young women with Nijmegen breakage syndrome: evidence from a longitudinal study

CONTEXT

Nijmegen breakage syndrome (NBS) is a severe chromosomal instability disorder characterized by microcephaly, growth retardation, immune deficiency, and predisposition for malignancy. It is caused by hypomorphic mutations in the NBN gene, which product belongs to the protein complex critical for processing DNA double-strand breaks during mitotic and meiotic recombination. Data on gonadal function in patients with NBS are limited.

OBJECTIVE

Growth and sexual development, along with hormonal assays, were evaluated in girls and young women with NBS homozygous for c.657_661del5 mutation.

STUDY DESIGN AND PATIENTS

The group comprised 37 girls and young women with NBS (ages, 0.17-24.25 yr), followed between 1993 and 2008. Patients were divided into three age groups: 1) 1-3 yr; 2) 4-9 yr; and 3) 10 yr and older. Growth, puberty, concentrations of gonadotropins and 17-beta-estradiol, bone age, and pelvic ultrasound were assessed.

RESULTS

None of the patients presented a typical growth spurt; the adult height ranged between the 3rd and 25th centiles. Median bone age was delayed by 4.05 yr. Pubarche reached stadium P2 in eight patients and P3 in two patients. In all but one girl, thelarche did not exceed Th2, with low 17beta-estradiol levels. Gonadotropin levels showed a biphasic pattern, with median FSH values of 55.0, 10.9, and 81.9 IU/liter, and LH of 3.2, 0.8, and 21.0 IU/liter in consecutive age groups. Ultrasound visualized small ovaries or solid streaks and the hypoplastic uterus.

CONCLUSIONS

Primary ovarian insufficiency and the associated hypergonadotropic hypogonadism are hallmark manifestations in girls and young women with NBS. Our findings emphasize the need for long-term endocrinological and interdisciplinary supervision of these patients.

Nuclear stress bodies

Nuclear stress bodies (nSBs) are unique subnuclear organelles which form in response to heat shock. They are initiated through a direct interaction between heat shock transcription factor 1 (HSF1) and pericentric tandem repeats of satellite III sequences and correspond to active transcription sites for noncoding satellite III transcripts. Given their unusual features, nSBs are distinct from other known transcription sites. In stressed cells, they are thought to participate in rapid, transient, and global reprogramming of gene expression through different types of mechanisms including chromatin remodeling and trapping of transcription and splicing factors. The analysis of these atypical and intriguing structures uncovers new facets of the relationship between nuclear organization and nuclear function.

Genomic instability and the selection of treatments for cancer

A critical link exists between DNA mutation and chromosomal rearrangements (genomic instability) and cancer development. This genomic instability can manifest itself as small changes at the nucleotide level or as gross chromosomal alterations. Mutations in the genes that encode DNA damage response proteins are responsible for a variety of genomic instability syndromes including hereditary non-polyposis colorectal carcinoma, Bloom's syndrome, ataxia-telangiectasia, BRCA-associated breast and ovarian cancers and Fanconi anaemia. Similarly, epigenetic silencing of genes associated with the maintenance of genomic stability have also been implicated in the pathogenesis of cancer. Here, we discuss how different tumours may be classified not only by tumour site but also by the type of underlying genetic instability. This type of classification may assist in the optimization of existing treatment regimens as well as informing the development of new therapeutic approaches.

Functional DNA repair system analysis in haematopoietic progenitor cells using host cell reactivation

Deficiencies in individual DNA repair systems are involved in both de novo and therapy-related acute myeloid leukaemia (t-AML), as indicated by genetic markers involving nucleotide excision repair (NER gene polymorphisms), double-strand-break (DSB) or mismatch repair (microsatellite instability (MSI)). We modified a host cell reactivation (HCR) assay for functional DNA repair system analysis of living primary haematopoietic cells; 2 x 10(5) normal peripheral blood lymphocytes (PBLs) and cord blood CD34+ progenitor cells were cryopreserved, thawed and transfected with 75-250 ng luciferase reporter plasmid (pCMVLuc) using DEAE-dextran (0.1 mg/mL) in a transfection volume of 250 microL. We obtained luciferase activities of approximately 300-fold above background in CD34+ progenitor cells and approximately 2000-fold in PBLs, thus rendering these cells applicable for DNA repair analysis. We then evaluated the NER (UV-irradiated pCMVLuc) and DSB repair capacity (linearized pCMVLuc) of normal lymphocytes and several leukaemic cell lineages. Kasumi-1 and HL-60 AML cells exhibited a reduced NER capacity compared to normal GM03715 lymphocytes, PBLs and CD34+ progenitor cells (6.2 +/- 0.9%, 6.5 +/- 0.9% vs. 12.3 +/- 1.8%, 13.5 +/- 0.7% and 13.5 +/- 2.0%, respectively). Kasumi-1 AML tells exhibited a reduced DSB repair capacity compared to AG10107 and GM03715 normal lymphocytes as well as CEM acute T-cell lymphoblastic leukaemia cells (6.4 +/- 0.8% vs. 10.8 +/- 0.7%, 27.3 +/- 1.1% and 20.5 +/- 1.6%, respectively). The modified HCR assay can be used for functional DNA repair analysis in living cells of patients with pre- and post-leukaemic conditions as well as in leukaemic blasts to elucidate the role of DNA repair in de novo and t-AML leukaemogenesis and to determine the individual susceptibility to t-AML prior to chemotherapy.

Non-B DNA conformations as determinants of mutagenesis and human disease

Repetitive DNA motifs may fold into non-B DNA structures, including cruciforms/hairpins, triplexes, slipped conformations, quadruplexes, and left-handed Z-DNA, thereby representing chromosomal targets for DNA repair, recombination, and aberrant DNA synthesis leading to repeat expansion or genomic rearrangements associated with neurodegenerative and genomic disorders. Hairpins and quadruplexes also determined the relative abundances of simple sequence repeats (SSR) in vertebrate genomes, whereas strong base stacking has permitted the expansion of purine.pyrimidine-rich SSR during evolutionary time. SSR are enriched in regulatory and cancer-related gene classes, where they have been actively recruited to participate in both gene and protein functions. SSR polymorphic alleles in the population are associated with cancer susceptibility, including within genes that appear to share regulatory circuits involving reactive oxygen species.

Risk of other cancers in individuals with a family history of pancreas cancer

BACKGROUND

Inherited predisposition to pancreas cancer accounts for approximately 10% of cases. Familial aggregation may be influenced by shared environmental factors and shared genes. We evaluate whether a family history of pancreas cancer is a risk factor for ten specified cancers in first-degree relatives: bladder, breast, colon, head and neck, lung, lymphoma, melanoma, ovary, pancreas, and prostate.

METHODS

Risk factor data and cancer family history were obtained for 1,816 first-degree relatives of pancreas cancer case probands (n = 247) and 3,157 first-degree relatives of control probands (n = 420). Unconditional logistic regression models using generalized estimating equations were used to estimate odds ratios (ORs), and 95% confidence intervals of having a first-degree relative a specified cancer.

RESULTS

A family history of pancreas cancer was associated with a doubled risk of lymphoma (OR = 2.83, 95% CI = 1.02-7.86) and ovarian cancer (OR = 2.25, 95% CI = 0.77-6.60) among relatives after adjustment. Relatives with a family history of early-onset pancreas cancer in a proband had a sevenfold increased risk of lymphoma (OR = 7.31, 95% CI = 1.45 to 36.7). Relatives who ever smoked and had a family history of pancreas cancer had a fivefold increased risk of ovarian cancer (OR = 4.89, 95% CI = 1.16-20.6).

CONCLUSION

Family history assessment of cancer risk should include all cancers. Assessment of other known and suspected risk factors in relatives will improve risk evaluation. As screening and surveillance methods are developed, identifying those at highest risk is crucial for a successful screening program.

Non-Hodgkin lymphoma (NHL) in children with Nijmegen Breakage syndrome (NBS)

BACKGROUND

Due to small number of patients with Nijmegen Breakage Syndrome (NBS) and Non-Hodgkin lymphoma (NHL) experience in their treatment is limited.

PROCEDURE

Since 1996, 17 patients with a median age of 9.5 years who had NBS, were treated for NHL. NHL type, stage, chemotherapy, dose modifications, chemotherapy delays, response to chemotherapy, toxicity, outcome and correlation of drug reduction with response to treatment and outcome were analyzed.

RESULTS

Nine patients had TNHL, eight BNHL. TNHL patients received BFM and BNHL LMB type protocols. Doses of cytostatics were reduced in the first chemotherapy courses. Further modifications depended on severity of complications. None of the patients complied with timing of chemotherapy. Complete remissions after induction were achieved in 8 of 9 TNHL and 3 out 8 of BNHL patients. All patients experienced grade 4 toxicities. Two patients died from complications. Six of 17 patients are alive. All received more than 80% of recommended doses of chemotherapy. No differences in the type, number of responses or grade 3 and 4 toxicities between patients receiving less or more than 80% of drug doses were observed. Treatment related deaths concerned patients who received less than 80% of drug doses.

CONCLUSIONS

Patients with NBS develop both T and B cell lymphomas. Treatment outcome is poor and might be improved by administering over 80% of drug doses. Although toxicity often depends upon drug doses, our patients experienced equal grade 3 and 4 toxicities whether they received more or less than 80% of the chemotherapeutic agents.

Is there an association with constitutional structural chromosomal abnormalities and hematologic neoplastic process? A short review

The occasional observation of constitutional chromosomal abnormalities in patients with a malignant disease has led to a number of studies on their potential role in cancer development. Investigations of families with hereditary cancers and constitutional chromosomal abnormalities have been key observations leading to the molecular identification of specific genes implicated in tumorigenesis. Large studies have been reported on the incidence of constitutional chromosomal aberrations in patients with hematologic malignancies, but they could not confirm an increased risk for hematologic malignancy among carriers of structural chromosomal changes. However, it is of particular interest that constitutional structural aberrations with breakpoints similar to leukemia-associated specific breakpoints have been reported in patients with hematologic malignancies. Because of insufficient data, it remains still unclear if these aberrations represent random events or are associated with malignancy. There has been a substantial discussion about mechanisms involved in constitutional structural chromosomal changes in the literature. The documentation of more patients with constitutional structural chromosomal changes could be of major importance. Most importantly, the molecular investigation of chromosomal regions involved in rearrangements could give useful information on the genetic events underlying constitutional anomalies, contributing to isolation of genes important in the development of the neoplastic process. Regarding constitutional anomalies in patients with hematologic disorders, a survey of the cytogenetic data of our cytogenetics unit is herein also presented.

Chromosome instability and risk of squamous cell carcinomas of head and neck

In 895 subjects with squamous cell carcinoma of the head and neck (SCCHN) and 898 cancer-free controls matched by age, sex, and ethnicity, we validated our previous finding that mutagen sensitivity as measured by the frequency of chromatid breaks in vitro induced by benzo[a]pyrene diol epoxide (BPDE) is an independent risk factor for SCCHN. Using a previously established concentration of 4 micromol/L BPDE to treat short-term cultured primary lymphocytes for 5 hours, we evaluated chromatid breaks in 50 well-spread metaphases for each blood sample. The mean frequency of BPDE-induced chromatid breaks was significantly higher in cases than in controls in non-Hispanic Whites (P = 0.0003) but not in other ethnic groups (P = 0.549 for Hispanic Americans and 0.257 for African Americans). The odds ratio associated with risk of SCCHN for the frequency of chromatid breaks greater than median value of controls was 1.56 (95% confidence interval, 1.27-1.91) in non-Hispanic Whites (767 cases and 763 controls) after adjustment for age, sex, smoking status, and drinking status. When the quartiles of the controls were used as the cutoff values, there was a dose response between the degree of mutagen sensitivity and risk of SCCHN in non-Hispanic Whites (P(trend) = 0.0001). However, none of these associations in non-Hispanic Whites was identified in Hispanic Americans (69 cases and 70 controls) or African Americans (59 cases and 65 controls), possibly because of the small samples of these ethnic groups or ethnic difference in genetic variation, which needs to be confirmed in future studies.

Different patterns of in vivo pro-oxidant states in a set of cancer- or aging-related genetic diseases

A comparative evaluation is reported of pro-oxidant states in 82 patients with ataxia telangectasia (AT), Bloom syndrome (BS), Down syndrome (DS), Fanconi anemia (FA), Werner syndrome (WS), and xeroderma pigmentosum (XP) vs 98 control donors. These disorders display cancer proneness, and/or early aging, and/or other clinical features. The measured analytes were: (a) leukocyte and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), (b) blood glutathione (GSSG and GSH), (c) plasma glyoxal (Glx) and methylglyoxal (MGlx), and (d) some plasma antioxidants [uric acid (UA) and ascorbic acid (AA)]. Leukocyte 8-OHdG levels ranked as follows: WS>BS approximately FA approximately XP>DS approximately AT approximately controls. Urinary 8-OHdG levels were significantly increased in a total of 22 patients with BS, FA, or XP vs 47 controls. The GSSG:GSH ratio was significantly increased in patients with WS and in young (< or =15 years) patients with DS or with FA and decreased in older patients with DS or FA and in AT, BS, and XP patients. The plasma levels of Glx and/or MGlx were significantly increased in patients with WS, FA, and DS. The UA and AA levels were significantly increased in WS and DS patients, but not in AT, FA, BS, nor XP patients. Rationale for chemoprevention trials is discussed.

Lessons learned from DNA repair defective syndromes

Genomic instability is the driving force behind cancer development. Human syndromes with DNA repair deficiencies comprise unique opportunities to study the clinical consequences of faulty genome maintenance leading to premature aging and premature cancer development. These syndromes include chromosomal breakage syndromes with defects in DNA damage signal transduction and double-strand break repair, mismatch repair defective syndromes as well as nucleotide excision repair defective syndromes. The same genes that are severely affected in these model diseases may harbour more subtle variations in the 'healthy' normal population leading to genomic instability, cancer development, and accelerated aging at later stages of life. Thus, studying those syndromes and the molecular mechanisms behind can significantly contribute to our understanding of (skin) cancerogenesis as well as to the development of novel individualized preventive and therapeutic anticancer strategies. The establishment of centers of excellence for studying rare genetic model diseases may be helpful in this direction.

Untangling the relationships between DNA repair pathways by silencing more than 20 DNA repair genes in human stable clones

Much effort has long been devoted to unraveling the coordinated cellular response to genotoxic insults. In view of the difficulty of obtaining human biological samples of homogeneous origin, I have established a set of stable human clones where one DNA repair gene has been stably silenced by means of RNA interference. I used pEBVsiRNA plasmids that greatly enhance long-term gene silencing in human cells. My older clones reached >500 days in culture. Knock-down HeLa clones maintained a gene silencing phenotype for an extended period in culture, demonstrating that I was able to mimic cells from cancer-prone syndromes. I have silenced >20 genes acting as sensors/transducers (ATM, ATR, Rad50, NBS1, MRE11, PARG and KIN17), or of different DNA repair pathways. In HeLa cells, I have switched off the expression of genes involved in nucleotide excision repair (XPA, XPC, hHR23A, hHR23B, CSA and CSB), nonhomologous end-joining (DNA-PKcs, XRCC4 and Ligase IV), homologous recombination repair (Rad51 and Rad54), or base excision repair (Ogg1 and Ligase III). These cells displayed the expected DNA repair phenotype. We could envisage untangling the complex network between the different DNA repair pathways. In this study, no viral vehicles, with their attendant ethical and safety concerns, were used.

Schimke immuno-osseous dysplasia: a cell autonomous disorder?

SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like protein 1) encodes a SWI/SNF ATP-dependent chromatin remodeling protein. Mutations in SMARCAL1 cause the autosomal-recessive multisystem disorder Schimke immuno-osseous dysplasia (SIOD); this suggests that the SMARCAL1 protein is involved in the development or maintenance of multiple organs. Disease within these many tissues could arise by a cell autonomous or a cell non-autonomous mechanism. Consistent with a cell autonomous mechanism, we did not find any disease recurrence in transplanted organs or protection of other tissues by the organ grafts. In order to better understand the role of SMARCAL1 during normal development and in the pathogenesis of SIOD, we characterized the spatial and temporal expression of the murine homolog (Smarcal1). The Smarcal1 mRNA and protein were expressed throughout development and in all tissues affected in patients with SIOD including the bone, kidney, thymus, thyroid, tooth, bone marrow, hair, eye, and blood vessels. Significantly, the expression profile of Smarcal1 in the mouse has led us to reexamine and identify novel pathology in our patient population resulting in changes in the clinical management of SIOD. The expression of Smarcal1 in affected tissues and the non-recurrence of disease in grafted organs lead us to hypothesize a cell autonomous function for SMARCAL1 and to propose tissue-specific mechanisms for the pathophysiology of SIOD.

DNA damage responses and their many interactions with the replication fork

The cellular response to DNA damage is composed of cell cycle checkpoint and DNA repair mechanisms that serve to ensure proper replication of the genome prior to cell division. The function of the DNA damage response during DNA replication in S-phase is critical to this process. Recent evidence has suggested a number of interrelationships of DNA replication and cellular DNA damage responses. These include S-phase checkpoints which suppress replication initiation or elongation in response to DNA damage. Also, many components of the DNA damage response are required either for the stabilization of, or for restarting, stalled replication forks. Further, translesion synthesis permits DNA replication to proceed in the presence of DNA damage and can be coordinated with subsequent repair by homologous recombination (HR). Finally, cohesion of sister chromatids is established coincident with DNA replication and is required for subsequent DNA repair by homologous recombination. Here we review these processes, all of which occur at, or are related to, the advancing replication fork. We speculate that these multiple interdependencies of DNA replication and DNA damage responses integrate the many steps necessary to ensure accurate duplication of the genome.

Transcription-coupled repair and premature ageing

During the past decades, several cellular pathways have been discovered to be connected with the ageing process. These pathways, which either suppress or enhance the ageing process, include regulation of the insulin/growth hormone axis, pathways involved with caloric restriction, ROS metabolism and DNA repair. In this review, we will provide a comprehensive overview of cancer and/or accelerated ageing pathologies associated with defects in the multi-step nucleotide excision repair pathway. Moreover, we will discuss evidence suggesting that there is a causative link between transcription-coupled repair and ageing.

Specific chromosome aberrations in peripheral blood lymphocytes are associated with risk of bladder cancer

Specific chromosome aberrations in peripheral blood lymphocytes (PBLs) in chromosomes 9 and 11 may be associated with bladder cancer. To investigate this hypothesis, in this study, we used a whole-chromosome painting technique to detect chromosomal aberrations in PBLs from 100 patients with bladder cancer and 100 matched controls. We also used a locus-specific fluorescence in situ hybridization technique to study 9p21 and cyclin D1 gene (CCND1) aberrations in PBLs of 10 patients and 10 controls and in tumor tissues of 38 additional cases. The chromosome-painting analysis showed that there were more aberrations of chromosomes 9 and 11 in bladder cancer patients than in controls. When categorized by type, the number of deletions of 9p and of translocations of chromosome 11 was significantly higher in patients than in controls (P < 0.05). Stratified analysis showed a larger odds ratio (OR) for bladder cancer in individuals with either a 9p deletion or a chromosome 11 translocation/amplification and an even larger OR in individuals with both aberrations. Using locus-specific analysis, we found that 9p21 aberrations occurred more frequently in bladder cancer patients (12.1 per 1,000 interphase cells) than in controls (6.4 per 1,000 interphase cells, P < 0.05); CCND1 translocation and amplification were observed only in bladder cancer patients. Tumor tissue analysis showed that aberrations of 9p21 (40.0 per 100 interphase cells) and CCND1 (43.8 per 100 interphase cells) were very common. Thus, we concluded that 9p deletions and translocations of chromosome 11, especially at 9p21 and CCND1, are associated with bladder cancer.

Phosphorylation states of cell cycle and DNA repair proteins can be altered by the nsSNPs

Background

Phosphorylation is a reversible post-translational modification that affects the intrinsic properties of proteins, such as structure and function. Non-synonymous single nucleotide polymorphisms (nsSNPs) result in the substitution of the encoded amino acids and thus are likely to alter the phosphorylation motifs in the proteins.

Methods

In this study, we used the web-based NetPhos tool to predict candidate nsSNPs that either introduce or remove putative phosphorylation sites in proteins that act in DNA repair and cell cycle pathways.

Results

Our results demonstrated that a total of 15 nsSNPs (16.9%) were likely to alter the putative phosphorylation patterns of 14 proteins. Three of these SNPs (CDKN1A-S31R, OGG1-S326C, and XRCC3-T241M) have already found to be associated with altered cancer risk. We believe that this set of nsSNPs constitutes an excellent resource for further molecular and genetic analyses.

Conclusion

The novel systematic approach used in this study will accelerate the understanding of how naturally occurring human SNPs may alter protein function through the modification of phosphorylation mechanisms and contribute to disease susceptibility.

Cancer and aging: symposium of the 27th annual meeting of the Japanese society for biomedical gerontology, Tokyo

Although many hypotheses have been proposed to explain the strong link between aging and cancer, the exact mechanisms responsible for the increased frequency of occurrence of cancer with advancing age have not been fully defined. Recent evidence indicates that malregulation of the apoptotic process may be involved in some aging process as well as in the development of cancer. Although it is still under debate how apoptosis is expressed during aging in vivo, this phenomenon is an important factor in unwinding the complicated mechanisms that link cancer and aging. In this review, we report on the discussion at the symposium of the 27th annual meeting of the Japanese society for biomedical gerontology, regarding recent findings from aging and carcinogenesis studies using animal models, the characteristics of cancer in patients with Werner's syndrome, the epigenetic changes in human cancers and aging, and the characteristics of human cancers in the elderly. It was concluded that apoptosis plays a role in the aging process and carcinogenesis in vivo, likely as an inherent protective mechanism against various kinds of damages to genes/chromosomes.

Repression of DNA repair mechanisms in IRF-4-expressing and HTLV-I-infected T lymphocytes

Human T cell leukemia virus (HTLV) is the causative agent of adult T cell leukemia (ATL), an aggressive and fatal leukemia of CD4+ T lymphocytes in which interferon regulatory factor-4 (IRF-4) becomes constitutively expressed, concomitant with major alterations in host gene expression. When constitutively expressed in uninfected T lymphocytes, IRF-4 caused reduced expression of critical DNA repair genes, including Rad51, XRCC1, Ung1, RPA, and proliferative cell nuclear antigen (PCNA), a transcriptional phenotype with striking similarities to the profile observed in HTLV-infected T lymphocytes. Concomitant with the inhibition of gene expression and defects in the DNA repair pathways, increased sensitivity of T lymphocytes to various genotoxic stresses that challenged all major DNA repair pathways were detected. Together, these results support a role for IRF- 4 in the repression of DNA repair activity and an increase in the risk of mutations. IRF-4 may thus represent a previously unidentified endogenous transcriptional repressor of DNA repair mechanisms.

The Arg280His polymorphism in X-ray repair cross-complementing gene 1 impairs DNA repair ability

The contribution of three single nucleotide polymorphisms (SNPs) that substitute amino acids in the X-ray repair cross-complementing gene 1 (XRCC1) protein, Arg194Trp (R194W), Arg280His (R280H), and Arg399Gln (R399Q), to the risk of various types of cancers has been extensively investigated by epidemiological researches. To investigate whether two of these polymorphisms directly influence their repair ability, we established Chinese hamster ovary (CHO) EM9 cell lines transfected with XRCC1(WT), XRCC1(R194W), or XRCC1(R280H) genes and analyzed the DNA repair ability of these cells. The EM9 cells that lack functional XRCC1 proteins exhibit severe sensitivity to methyl methanesulfonate (MMS). Introduction of the human XRCC1(WT) and XRCC1(R194W) gene to EM9 cells restored the MMS sensitivity to the same level as the AA8 cells, a parental cell line. However, introduction of the XRCC1(R280H) gene partially restored the MMS sensitivity, resulting in a 1.7- to 1.9-fold higher sensitivity to MMS compared with XRCC1(WT) and XRCC1(R194W) cells at the LD(50) value. The alkaline comet assay determined diminished base excision repair/single strand break repair (BER/SSBR) efficiency in XRCC1(R280H) cells as observed in EM9 cells. In addition, the amount of intracellular NAD(P)H decreased in XRCC1(R280H) cells after MMS treatment. Indirect immunofluorescence staining of the XRCC1 protein showed an intense increase in the signals and clear foci of XRCC1 in the nuclei of the XRCC1(WT) cells, but a faint increase in the XRCC1(R280H) cells, after MMS exposure. These results suggest that the XRCC1(R280H) variant protein is defective in its efficient localization to a damaged site in the chromosome, thereby reducing the cellular BER/SSBR efficiency.

Pathways of DNA double-strand break repair and their impact on the prevention and formation of chromosomal aberrations

DNA double-strand breaks (DSB) are considered the critical primary lesion in the formation of chromosomal aberrations (CA). DSB occur spontaneously during the cell cycle and are induced by a variety of exogenous agents such as ionising radiation. To combat this potentially lethal damage, two related repair pathways, namely homologous recombination (HR) and non-homologous DNA end joining (NHEJ), have evolved, both of which are well conserved from bacteria to humans. Depending on the pathway used, the underlying mechanisms are capable of eliminating DSB without alterations to the original genomic sequence (error-free) but also may induce small scale mutations (base pair substitutions, deletions and/or insertions) and gross CA (error-prone). In this paper, we review the major pathways of DSB-repair, the proteins involved therein and their impact on the prevention of CA formation and carcinogenesis.

Increased rates of spontaneous sister chromatid exchange in lymphocytes of BRCA2+/- carriers of familial breast cancer clusters

Heterozygous carriers of germ-line mutations of the BRCA2 breast cancer susceptibility gene are predisposed to breast, ovarian, pancreatic and other cancers. The BRCA2 protein is implicated in the maintenance of chromosome stability through its essential function in double-strand DNA repair and recombination. Our previous studies had revealed multiple intrachromosomal rearrangements, duplications, inversions and deletions on 9p23-24 in lymphocytes and fibroblasts of BRCA2+/- members from independently ascertained familial breast cancer clusters. In pursuit of evaluating if there is a subtle genomic instability in BRCA2+/- individuals, we have determined frequencies of spontaneous sister chromatid exchanges (SCEs) in BRCA2 wild-types and BRCA2 mutation carriers of two familial breast cancer clusters. Here, we demonstrate an average increase of 65% of spontaneous SCEs in BRCA2+/- versus BRCA2+/+ family members. In one cluster, the number of metaphases with multiple SCEs was 5-times higher in BRCA2+/- compared to wild-type members, while in the second cluster BRCA2+/- members had 8.9% of metaphases with multiple SCEs compared to a level below detection in BRCA2 wild types. To investigate the correlation between SCE and genomic instability in 9p, we performed fluorescence detection of SCEs and FISH analysis with 9p probes. The frequency of SCE in 9p of BRCA2 mutation carriers was 3-4 fold (P = 0.005) higher compared to BRCA2 wild-types. Collectively, the increased rates of SCE in BRCA2 heterozygous mutation carriers indicate a BRCA2 haploinsufficiency, which might be an important factor for the accumulation of structural chromosomal alterations with the consequence of damage in as yet unidentified genes.

Second malignancy following high-dose therapy and autologous stem cell transplantation: incidence and risk factor analysis

To establish incidence and risk factors for development of second malignant neoplasms after high-dose chemo/radiotherapy (HDT) and autologous hematopoietic stem cell transplantation (AHSCT), the case files of 800 consecutive patients who underwent AHSCT at our institution between June 1982 and December 2000 were reviewed. In all, 26 patients developed 29 second malignancies (nine myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML), 16 solid tumors and four lymphoproliferative disorders (LPDs)) for a 15-year cumulative incidence of 11% (95% confidence interval (CI), 5-18%). These second tumors occurred at a median of 68 (range 1.5-177) months following AHSCT. The relative risk (RR) compared to the general population of developing a second malignancy following AHSCT was 3.3 (CI 2.2-4.7) P<0.001. The RR of developing MDS/AML, LPD and a solid tumor was 47.2 (CI 21.5-89.5) P<0.001, 8.1 (2.2-20.7) P=0.002 and 1.98 (1.1-3.2) P=0.009, respectively. In multivariate analysis, age >or=35 years at the time of AHSCT (P=0.001) and an interval from diagnosis to AHSCT >or=36 months (P=0.03) were associated with a greater risk of developing a second malignancy. Patients who have undergone HDT and AHSCT are at significant risk for developing a second malignancy and should receive indefinite follow-up.

Gluten-free diet has a beneficial effect on chromosome instability in lymphocytes of children with coeliac disease

OBJECTIVES

Children with coeliac disease (CD) have an increased number of chromosome aberrations in peripheral blood lymphocytes. Whether genetically determined or a secondary phenomenon in CD, chromosome abnormalities may be involved in the predisposition to cancer in CD patients. The aim of the study was to follow a group of children with CD in whom the initial frequency of chromosome aberrations at diagnosis was known and to measure the same variable after a minimum of 2 years on a gluten-free diet.

METHODS

Chromosome aberrations in peripheral blood lymphocytes were determined in 17 patients with CD, before and after at least 24 months of a gluten free diet (mean, 33 months), and in 15 healthy children. The differences in the frequency of aberrations were analyzed by Mann-Whitney U test and Wilcoxon matched-pairs signed-ranks test.

RESULTS

Twelve patients adhered to the diet and had a significantly lower frequency of chromosome aberrations than did 5 patients not following the diet (0.16% v 1.2%; P = 0.03), whereas at presentation there had been no difference (1.54% v 1.2%; P = 0.09). The frequency of aberrations at follow-up in patients who were diet adherent was significantly lower than at presentation (1.54% v 0.16%; P = 0.02) and remained unchanged in patients who were not diet adherent (1.2% v 1.2%; P = 1). After at least 24 months of a gluten-free diet, children with CD did not differ from healthy control subjects (0.16% v 0.27%; P = 0.54), whereas children not following the diet had an increased frequency of aberrations (1.2% v 0.27%; P = 0.05).

CONCLUSIONS

The frequency of chromosome aberrations in peripheral blood lymphocytes of patients with CD decreased significantly on a gluten-free diet. We conclude that genomic instability is a secondary phenomenon, possibly caused by chronic intestinal inflammation.

Clinical manifestations of genetic instability overlap one another

Cancer syndromes are characteristic associations of specific malignancies with various congenital anomalies. In addition to such diseases, an increased prevalence in general of chromosomal instability, malformations, immunodeficiencies, altered growth and development, and reproductive loss has been observed in both childhood leukemias and solid tumors. The overlap among these congenital disorders suggests their common prenatal, possibly genetic origin and thus the existence of a nonspecific genetic instability leading to various clinical manifestations of disturbances in cell division. Seeking for related features in family members of a patient with malignancy may be of clinical value in detecting predisposition to cancer.

Update on primary immunodeficiency: defects of lymphocytes

The recent identification of the genes involved in many primary immunodeficiency disorders has led to a significant increase in our understanding of the pathogenesis of these defects. Many of these disorders share a clinical phenotype with common features such as recurrent infections, chronic inflammation, and autoimmunity. Although some of these immune defects have mild presentations and better outcomes, others result in severe infections and significant morbidity and mortality. For these, early diagnosis and treatment are critical. This review provides an overview of the genetic defects and clinical features of primary immune deficiencies due to defects in lymphocytes.

Radiation-induced genomic instability and its implications for radiation carcinogenesis

Radiation-induced genomic instability is characterized by an increased rate of genetic alterations including cytogenetic rearrangements, mutations, gene amplifications, transformation and cell death in the progeny of irradiated cells multiple generations after the initial insult. Chromosomal rearrangements are the best-characterized end point of radiation-induced genomic instability, and many of the rearrangements described are similar to those found in human cancers. Chromosome breakage syndromes are defined by chromosome instability, and individuals with these diseases are cancer prone. Consequently, chromosomal instability as a phenotype may underlie some fraction of those changes leading to cancer. Here we attempt to relate current knowledge regarding radiation-induced chromosome instability with the emerging molecular information on the chromosome breakage syndromes. The goal is to understand how genetic and epigenetic factors might influence the onset of chromosome instability and the role of chromosomal instability in carcinogenesis.

The TP53 dependence of radiation-induced chromosome instability in human lymphoblastoid cells

The dose and TP53 dependence for the induction of chromosome instability were examined in cells of three human lymphoblastoid cell lines derived from WIL2 cells: TK6, a TP53-normal cell line, NH32, a TP53-knockout created from TK6, and WTK1, a WIL2-derived cell line that spontaneously developed a TP53 mutation. Cells of each cell line were exposed to (137)Cs gamma rays, and then surviving clones were isolated and expanded in culture for approximately 35 generations before the frequency and characteristics of the instability were analyzed. The presence of dicentric chromosomes, formed by end-to-end fusions, served as a marker of chromosomal instability. Unexposed TK6 cells had low levels of chromosomal instability (0.002 +/- 0.001 dicentrics/cell). Exposure of TK6 cells to doses as low as 5 cGy gamma rays increased chromosome instability levels nearly 10-fold to 0.019 +/- 0.008 dicentrics/cell. There was no further increase in instability levels beyond 5 cGy. In contrast to TK6 cells, unexposed cultures of WTK1 and NH32 cells had much higher levels of chromosome instability of 0.034 +/- 0.007 and 0.041 +/- 0.009, respectively, but showed little if any effect of radiation on levels of chromosome instability. The results suggest that radiation exposure alters the normal TP53-dependent cell cycle checkpoint controls that recognize alterations in telomere structure and activate apoptosis.