Accumulation Of Chromosomal Aberrations Research Articles

PrimPol Variant V102A with Altered Primase and Polymerase Activities

PrimPol is a human DNA primase-polymerase which restarts DNA synthesis beyond DNA lesions and non-B DNA structures blocking replication. Disfunction of PrimPol in cells leads to slowing of DNA replication rates in mitochondria and nucleus, accumulation of chromosome aberrations, cell cycle delay, and elevated sensitivity to DNA-damaging agents. A defective PrimPol has been suggested to be associated with the development of ophthalmic diseases, elevated mitochondrial toxicity of antiviral drugs and increased cell resistance to chemotherapy. Here, we describe a rare missense PrimPol variant V102A with altered biochemical properties identified in patients suffering from ovarian and cervical cancer. The Val102 to Ala substitution dramatically reduced both the primase and DNA polymerase activities of PrimPol as well as specifically decreased its ability to incorporate ribonucleotides. Structural analysis indicates that the V102A substitution can destabilize the hydrophobic pocket adjacent to the active site, affecting dNTP binding and catalysis.

Abstract 2209: Characterization of underlying genomic features among African ancestry populations diagnosed with chronic lymphocytic leukemia

Abstract Chronic lymphocytic leukemia (CLL) is a neoplastic disease of mature B-cells with a highly heterogeneous clinical course. While European ancestry (EA) populations present an increased incidence of CLL, African ancestry (AA) populations have a younger median age of onset, higher frequency of adverse prognostic factors, and inferior clinical outcomes. Despite the considerable effort to characterize the genetic landscape of CLL, AA are overwhelmingly underrepresented. Our hypothesis is that the clinical differences observed between AA and EA populations are, in part, explained by underlying genetic features. To address this imbalance, we identified 90 AA patients diagnosed with CLL, 64% of which were untreated at sample collection. RNA and DNA were extracted from CD5+/CD19+ clonal B-cells. We performed mRNA-seq and targeted sequencing in 59 recurrently mutated somatic CLL driver genes. Differentially expressed genes were identified using edgeR. Data was compared to our previously analyzed EA CLL cohort (N=445). The median age at diagnosis was 59 years for AA and 66 for EA and 74% of AA and 50% of EA had unmutated IGHV (u-IGHV) status. When evaluating the entire AA and EA cohorts, there was a significant increased frequency of mutations in TP53, SF3B1, and NFKBIE, identified in 29%, 24%, and 20% of AA CLLs, compared to 5%, 9%, and 9%, respectively, in EA CLLs (p<0.01). When exclusively evaluating the untreated and u-IGHV cases, AA CLLs showed greater proportion of TP53 (30% vs 12%; p=0.0145), NFKBIE (30% vs 15%; p=0.0492), BIRC3 (21% vs 10%; p=0.0697), and KRAS (15% vs 7%; p=0.1683). Furthermore, there was an increase in mutations targeting relevant molecular pathways, such as NF-κB (42% vs 15%) and MAPK (18% vs 8%). Upregulation MAPK pathway was also confirmed by mRNA-seq analysis in the AA u-IGHV CLLs. Because of the high prevalence of TP53 mutations in the AA cohort, we further evaluated differential gene expression in the DNA Damage/Telomere Stress-Induced Senescence pathway. AA CLLs presented a significant downregulation of multiple genes associated with genome stability and cellular DNA damage response - DDR (including TP53 and ATM), double strand break repair (H2AFX and RAD50), telomere maintenance (POT1 and ACD), and cell cycle regulation (RB1, CCNA1, and CCNE2) (FDR<0.05). DDR is responsible for DNA repair or induction of apoptosis, with its deficiency resulting in the accumulation of chromosomal aberrations, negatively impacting clinical outcome in CLL. Disparities in cancer are influenced by numerous factors that affect disease risk, screening and diagnosis, access to treatment, and survival. We identified an increased number of genomic alterations in the AA CLL cohort, primarily inducing activation of NF-κB and MAPK pathways and DDR impairment, with the increased frequency of mutations, notably in TP53 and BIRC3, expected to negatively impact prognosis. Citation Format: Cecilia Bonolo de Campos, Daniel R. O'Brien, Chantal E. McCabe, Huihuang Yan, Geffen Kleinstern, Zhiquan Wang, Laura A. Bruins, Cristine Allmer, Nicholas J. Boddicker, Charla R. Secreto, Aaron D. Norman, Shulan Tian, Kari G. Rabe, Timothy G. Call, Sameer A. Parikh, Jose F. Leis, Wei Ding, Richard Furman, J Brice Weinberg, James R. Cerhan, Celine M. Vachon, Neil E. Kay, Susan L. Slager, Esteban Braggio. Characterization of underlying genomic features among African ancestry populations diagnosed with chronic lymphocytic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2209.

Chromosomal damage and telomere length in peripheral blood lymphocytes of cancer patients.

Accumulation of non‑specific structural chromosomal aberrations (CAs) and telomere shortening contribute to genome instability, which constitutes as one of the hallmarks of cancer. CAs arise due to direct DNA damage or telomere shortening. CAs in peripheral blood lymphocytes (PBL), which are considered to be markers of exposure, have been previously reported to serve a role in the pathophysiology and progression of cancer through mechanisms that are poorly understood. In addition, the prognostic relevance of telomere length (TL) in patients with cancer remains to be elucidated. In the present study, CAs and TL in PBL isolated from patients with newly diagnosed cancer (151 breast, 96 colorectal, 90 lung) and 335 cancer‑free control individuals were investigated. These results were then correlated with clinicopathological factors and follow‑up data. The accumulation of CAs in PBL was observed with increased susceptibility to breast and lung cancer (P<0.0001), while individuals with longer TL were found to be at a higher risk of breast cancer (P<0.0001). Increased chromatid‑type aberrations were also revealed to be associated with lower overall survival of patients with breast and colorectal cancers using a multivariate model. Compared with control individuals, no association was observed between TL and CAs or age in patients with cancer. In conclusion, the present study demonstrates the association between CAs/TL in PBL and the susceptibility, prognosis and survival of patients with breast, colorectal and lung cancer.

Chromosomal Instability and Karyotype Correction in Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (iPSCs) are a promising source of cells for regenerative medicine, study of the pathogenesis of various diseases, screening of pharmacological drugs, and other clinical and basic research. However, the maintenance of the genetic stability of the cells during reprogramming, long-term culture, and directed differentiation is necessary for the use of iPSCs. Large chromosomal aberrations affect the quality of iPSCs most adversely, so the review focuses on the analysis of chromosomal abnormalities, including the recurrent aneuploidy; the sources of its origin, the effect of reprogramming, and long-term culture on the accumulation of chromosome aberrations are discussed. Cases of spontaneous correction of the iPSCs karyotype and the possibility of induced correction of the large chromosomal abnormalities by removing or silencing the extra homologue are considered.

Effects of COJEC induction on neuroblastoma patient-derived xenografts (PDX).

e21503 Background: Neuroblastoma (NB) is a solid pediatric tumor that causes 15% of childhood cancer deaths. High-risk patients have 50 to 70% mortality after 5 years. Currently, the standard way to treat high risk patients is COJEC induction followed by surgery, chemotherapy with stem cell transplants, irradiation and immunotherapy. This intense treatment has significantly increased overall survival, but mortality is still high, survivors are prone to relapse and treatment resistance is a major clinical problem. COJEC induction consists in the cycled administration of the chemotherapeutics Cisplatin, Vincristine, Etoposide, Cyclophosphamide and Carboplatin. These drugs have been long used in the clinic, but a comprehensive preclinical study combining all of them had not been done. The aim of this project was to establish a PDX model for chemotherapy induction in high-risk NB and investigate tumor characteristics and response upon treatment. Methods: NB cells from previously developed high-risk PDX models were injected subcutaneously in nude mice. When tumors reached an appropriate size, they were treated with either a COJEC-like protocol or single agent induction with high dose cisplatin. After treatment, tumors were analyzed by immunohistochemistry, chromosomal copy number analysis and RNA sequencing. Results: Most mice responded well to COJEC induction and 8/10 tumors were reduced. Within the reduced tumors, 4 were subjected to total resection and relapsed after several weeks, mimicking the clinical situation. Cisplatin treatment alone led to no significant tumor reduction and 6/10 tumors were highly resistant. Thus, as for humans, multidrug induction is more successful in reducing tumor size but presents an uneven response with high relapse rate. The responsive tumors show a higher degree of cellular differentiation when compared to resistant tumors. Cisplatin treated tumors have accumulation of chromosomal aberrations when compared to controls, and subclonal dynamics are enhanced in resistant tumors. Conclusions: We established a PDX model for chemotherapy induction in high-risk NB. The results mimic clinical findings seen in high-risk NB patients. The model is useful to understand the mechanisms of treatment resistance and for the testing of novel therapies against high-risk NB.

Repair of UV-Induced DNA Damage Independent of Nucleotide Excision Repair Is Masked by MUTYH

DNA lesions caused by UV damage are thought to berepaired solely by the nucleotide excision repair (NER) pathway in human cells. Patients carrying mutations within genes functioning in this pathwaydisplay a range of pathologies, including an increased susceptibility to cancer, premature aging, and neurological defects. There are currently no curative therapies available. Here we performed a high-throughput chemical screen for agents that could alleviate the cellular sensitivity of NER-deficient cells to UV-induced DNA damage. This led tothe identification of the clinically approved anti-diabeticdrug acetohexamide, which promoted clearance of UV-induced DNA damage without the accumulation of chromosomal aberrations, hence promoting cellular survival. Acetohexamide exerted this protective function by antagonizing expressionof the DNA glycosylase, MUTYH. Together, our data reveal the existence of an NER-independent mechanism to remove UV-induced DNA damage and prevent cell death.

Shortage of dNTPs underlies altered replication dynamics and DNA breakage in the absence of the APC/C cofactor Cdh1.

The APC/C-Cdh1 ubiquitin-ligase complex targets cell cycle regulators for proteosomal degradation and helps prevent tumor development and accumulation of chromosomal aberrations. Replication stress has been proposed to be the main driver of genomic instability in the absence of Cdh1, but the real contribution of APC/C-Cdh1 to efficient replication, especially in normal cells, remains unclear. Here we show that, in primary MEFs, acute depletion or permanent ablation of Cdh1 slowed down replication fork movement and increased origin activity. Partial inhibition of origin firing does not accelerate replication forks, suggesting that fork progression is intrinsically limited in the absence of Cdh1. Moreover, exogenous supply of nucleotide precursors, or ectopic overexpression of RRM2, the regulatory subunit of Ribonucleotide Reductase, restore replication efficiency, indicating that dNTP availability could be impaired upon Cdh1 loss. Indeed, we found reduced dNTP levels in Cdh1-deficient MEFs. Importantly, DNA breakage is also significantly alleviated by increasing intracellular dNTP pools, strongly suggesting that genomic instability is the result of aberrant replication. These observations highlight the relevance of APC/C-Cdh1 activity during G1 to ensure an adequate supply of dNTPs to the replisome, prevent replication stress and the resulting chromosomal breaks and, ultimately, suppress tumorigenesis.

TOPBP1Dpb11 plays a conserved role in homologous recombination DNA repair through the coordinated recruitment of 53BP1Rad9

Genome maintenance and cancer suppression require homologous recombination (HR) DNA repair. In yeast and mammals, the scaffold protein TOPBP1Dpb11 has been implicated in HR, although its precise function and mechanism of action remain elusive. In this study, we show that yeast Dpb11 plays an antagonistic role in recombination control through regulated protein interactions. Dpb11 mediates opposing roles in DNA end resection by coordinating both the stabilization and exclusion of Rad9 from DNA lesions. The Mec1 kinase promotes the pro-resection function of Dpb11 by mediating its interaction with the Slx4 scaffold. Human TOPBP1Dpb11 engages in interactions with the anti-resection factor 53BP1 and the pro-resection factor BRCA1, suggesting that TOPBP1 also mediates opposing functions in HR control. Hyperstabilization of the 53BP1-TOPBP1 interaction enhances the recruitment of 53BP1 to nuclear foci in the S phase, resulting in impaired HR and the accumulation of chromosomal aberrations. Our results support a model in which TOPBP1Dpb11 plays a conserved role in mediating a phosphoregulated circuitry for the control of recombinational DNA repair.

CHORNOBYL CATASTROPHE: CYTOGENETIC EFFECTS OF LOW DOSE IONIZING RADIATION AND THEIR MODIFICATION

Among the long-term effects of the Chornobyl disaster the greatest concern of international medical and scientific community is given to the established fact of excess of the spontaneous level of cancer incidence in the exposed population. According to mo-dern concepts, the accumulation of chromosome aberrations, especially in radiosensitive cells, could be potentially oncogenic, and low doses of ionizing radiation could be promoters of the radiation-induced carcinogenesis. The results of our studies have shown that such substances as thymalin, inosine, ascorbic acid, caffeine could modify radiation-induced cytogenetic effects in peripheral blood lymphocytes of healthy individuals and exert protective or sensitizing action dependent on their concentrations, cell radiosensitivity, dose of irradiation, and relative biologic effectiveness of ionizing radiation. This article is part of a Special Issue entitled "The Chornobyl Nuclear Accident: Thirty Years After".

Influence of storage durations on seed germination and the accumulation of chromosomal aberrations in two rice varieties (Oryza sativa L.)

Influence of storage durations on seed germination and the accumulation of chromosomal aberrations in two rice varieties (Oryza sativa L.)

Single nucleotide polymorphism array profiling identifies distinct chromosomal aberration patterns across colorectal adenomas and carcinomas.

The progression of benign colorectal adenomas into cancer is associated with the accumulation of chromosomal aberrations. Even though patterns and frequencies of chromosomal aberrations have been well established in colorectal carcinomas, corresponding patterns of aberrations in adenomas are less well documented. The aim of this study was to profile chromosomal aberrations across colorectal adenomas and carcinomas to provide a better insight into key changes during tumor initiation and progression. Single nucleotide polymorphism array analysis was performed on 216 colorectal tumor/normal matched pairs, comprising 60 adenomas and 156 carcinomas. While many chromosomal aberrations were specific to carcinomas, those with the highest frequency in carcinomas (amplification of chromosome 7, 13q, and 20q; deletion of 17p and chromosome 18; LOH of 1p, chromosome 4, 5q, 8p, 17p, chromosome 18, and 20p) were also identified in adenomas. Hierarchical clustering using chromosomal aberrations revealed three distinct subtypes. Interestingly, these subtypes were only partially dependent on tumor staging. A cluster of colorectal cancer patients with frequent chromosomal deletions had the least favorable prognosis, and a number of adenomas (n = 9) were also present in the cluster suggesting that, at least in some tumors, the chromosomal aberration pattern is determined at a very early stage of tumor formation. Finally, analysis of LOH events revealed that copy-neutral/gain LOH (CN/G-LOH) is frequent (>10%) in carcinomas at 5q, 11q, 15q, 17p, chromosome 18, 20p, and 22q. Deletion of the corresponding region is sometimes present in adenomas, suggesting that LOH at these loci may play an important role in tumor initiation.

Rac2-MRC-cIII–generated ROS cause genomic instability in chronic myeloid leukemia stem cells and primitive progenitors

AbstractChronic myeloid leukemia in chronic phase (CML-CP) is induced by BCR-ABL1 oncogenic tyrosine kinase. Tyrosine kinase inhibitors eliminate the bulk of CML-CP cells, but fail to eradicate leukemia stem cells (LSCs) and leukemia progenitor cells (LPCs) displaying innate and acquired resistance, respectively. These cells may accumulate genomic instability, leading to disease relapse and/or malignant progression to a fatal blast phase. In the present study, we show that Rac2 GTPase alters mitochondrial membrane potential and electron flow through the mitochondrial respiratory chain complex III (MRC-cIII), thereby generating high levels of reactive oxygen species (ROS) in CML-CP LSCs and primitive LPCs. MRC-cIII–generated ROS promote oxidative DNA damage to trigger genomic instability, resulting in an accumulation of chromosomal aberrations and tyrosine kinase inhibitor–resistant BCR-ABL1 mutants. JAK2(V617F) and FLT3(ITD)–positive polycythemia vera cells and acute myeloid leukemia cells also produce ROS via MRC-cIII. In the present study, inhibition of Rac2 by genetic deletion or a small-molecule inhibitor and down-regulation of mitochondrial ROS by disruption of MRC-cIII, expression of mitochondria-targeted catalase, or addition of ROS-scavenging mitochondria-targeted peptide aptamer reduced genomic instability. We postulate that the Rac2-MRC-cIII pathway triggers ROS-mediated genomic instability in LSCs and primitive LPCs, which could be targeted to prevent the relapse and malignant progression of CML.

DNA polymerase zeta is required for proliferation of normal mammalian cells

Unique among translesion synthesis (TLS) DNA polymerases, pol ζ is essential during embryogenesis. To determine whether pol ζ is necessary for proliferation of normal cells, primary mouse fibroblasts were established in which Rev3L could be conditionally inactivated by Cre recombinase. Cells were grown in 2% O2 to prevent oxidative stress-induced senescence. Cells rapidly became senescent or apoptotic and ceased growth within 3–4 population doublings. Within one population doubling following Rev3L deletion, DNA double-strand breaks and chromatid aberrations were found in 30–50% of cells. These breaks were replication dependent, and found in G1 and G2 phase cells. Double-strand breaks were reduced when cells were treated with the reactive oxygen species scavenger N-acetyl-cysteine, but this did not rescue the cell proliferation defect, indicating that several classes of endogenously formed DNA lesions require Rev3L for tolerance or repair. T-antigen immortalization of cells allowed cell growth. In summary, even in the absence of external challenges to DNA, pol ζ is essential for preventing replication-dependent DNA breaks in every division of normal mammalian cells. Loss of pol ζ in slowly proliferating mouse cells in vivo may allow accumulation of chromosomal aberrations that could lead to tumorigenesis. Pol ζ is unique amongst TLS polymerases for its essential role in cell proliferation.

Genomic Instability Originates From Leukemia Stem Cells in a Mouse Model of CML-CP

Abstract 445For decades, chronic myeloid leukemia (CML) has served not only as a paradigm for understanding the evolution and multi-step process of carcinogenesis but also for studying cancer stem and progenitor cells responsible for the initiation and/or maintenance of the disease. CML is initiated by BCR-ABL1 tyrosine kinase transformation of hematopoietic stem cells into leukemia stem cells (LSCs) to induce CML-chronic phase (CML-CP). The deregulated growth of LSC-derived leukemia progenitor cells (LPCs) leads to manifestation of the disease. It is unclear if LSCs and/or LPCs are able to acquire additional genetic changes that confer resistance to tyrosine kinase inhibitors (TKIs) and induce more aggressive CML blast phase (CML-BP). In addition, the mechanisms and consequences of genomic instability may differ substantially among these cells. For example, the effects of genetic aberrations acquired in quiescent LSCs may be dormant, but if the aberrations induce proliferation or appear in LSCs that are already cycling, they may generate TKI-resistant and/or more malignant clones. Alternatively, genomic instability in LPCs must be accompanied by the acquisition of LSC-like properties to prevent mutations from disappearing before they undergo terminal maturation.Previously, we reported that BCR-ABL1–transformed cell lines accumulate reactive oxygen species (ROS)-induced oxidative DNA damage [8-oxoguanine (8oxoG), double strand breaks (DSBs)] resulting in genomic instability in vitro, which was responsible for acquired imatinib-resistance and accumulation of chromosomal aberrations (Nowicki et al., Blood, 2005; Koptyra et al., Blood, 2006; Koptyra et al., Leukemia, 2008). To determine which populations of CML-CP cells, LSCs and/or LPCs, accumulate genomic instability we employed the SCLtTA/BCR-ABL1 tetracycline-inducible (tet-off) transgenic mouse model of CML-CP with targeted expression of p210BCR-ABL1 in hematopoietic stem and progenitor cells (Koschmieder et al., Blood, 2005). Mice exhibiting CML-CP-like disease resulting from BCR-ABL1 induction demonstrated splenomegaly and Gr1+/CD11b+ myeloid expansion in bone marrow, spleen and peripheral blood. BCR-ABL1 mRNA expression was higher in the Lin−c-Kit+Sca1+ murine leukemia stem cell–enriched population (muLSCs) than in the Lin−c-Kit+Sca1− murine leukemia progenitor cell–enriched population (muLPCs), thus reminiscent of human CML-CP (Lin−CD34+CD38− LSCs > Lin−CD34+CD38+ LPCs). BCR-ABL1 induction increased levels of ROS (hydrogen peroxide, hydroxyl radical) and oxidative DNA damage (8-oxoG, DSBs) in muLSCs, but not in muLPCs. In addition, CFSEmax/eFluor670max quiescent muLSCs displayed more ROS (superoxide, hydrogen peroxide) and oxidative DNA damage (8oxoG, DSBs) than non-induced counterparts. Currently, we are examining genomic instability in the most primitive long-term muLSCs (Lin−c-Kit+Sca1+CD34−Flt3−). Lastly, single nucleotide polymorphism (SNP) arrays detected a variety of genetic aberrations (addition, deletions) in BCR-ABL1–induced Lin− BM cells. Individual mice displayed a great degree of diversity in the intensity of genetic instability accumulating between 31 to 826 aberrations, which recapitulate heterogeneity of sporadic aberrations detected in CML-CP patients. These aberrations include deletions in Trp53 and Ikzf1, and additions in Zfp423 and Idh1 genes, which have been linked to progression from CML-CP to CML-BP.In summary, by using the SCLtTA/BCR-ABL1 inducible transgenic mouse model of CML-CP we showed that muLSCs, but not muLPCs, displayed elevated levels of ROS-induced oxidative DNA damage likely resulting in the accumulation of extensive genetic aberrations. This observation supports the hypothesis that genomic instability in CML-CP originates in LSCs. Current analysis of microarrays may shed some light on the mechanisms leading to enhanced ROS production and accumulation of oxidative DNA damage in muLSCs. Disclosures:Koschmieder:Novartis, Bristol-Myers Squibb: Consultancy.

CML-CP Mouse Model of Genomic Instability.

AbstractAbstract 1210 Background:BCR-ABL1 transforms hematopoietic stem cells to induce chronic myeloid leukemia in chronic phase (CML-CP). Although CML is stem cell-derived, it is a progenitor cell-driven disease. In CML-CP, leukemia stem cells (LSCs) are characterized by elevated BCR-ABL1 expression in comparison to leukemia progenitor cells (LPCs). Increased expression of BCR-ABL1 kinase is also associated with progression from CML-CP to CML-blast phase. Previously we showed that BCR-ABL1 kinase stimulates reactive oxygen species (ROS)-dependent DNA damage resulting in genomic instability in vitro, which was responsible for acquired imatinib-resistance and accumulation of chromosomal aberrations (Nowicki et al., Blood, 2005; Koptyra et al., Blood, 2006; Koptyra et al., Leukemia, 2008). Result:To examine the effects of BCR-ABL1 expression on genomic instability during in vivo leukemogenesis we employed an inducible transgenic mouse model of CML-CP with targeted expression of p210BCR-ABL1 in hematopoietic stem and progenitor cells (Koschmieder et al., Blood, 2005). Mice exhibiting CML-CP-like disease resulting from BCR-ABL1 induction demonstrated splenomegaly, leukocytosis, and Gr1+/CD11b+ myeloid expansion in bone marrow, spleen and peripheral blood, as detected by FACS analysis. BCR-ABL1 mRNA expression was higher in Lin-c-Kit+Sca1+ stem-enriched cells than in Lin-c-Kit+Sca1- progenitor-enriched cells, thus reminiscent of CML-CP (LSCs>LPCs). BCR-ABL1 increased levels of ROS (hydrogen peroxide, hydroxyl radical) and oxidative DNA lesions (8-oxoG) in LSC-enriched Lin-c-Kit+Sca1+ cells. Preliminary data also suggested that quiescent (CFSEmax) Lin-c-Kit+Sca1+ cells from BCR-ABL1-induced mice exhibited greater ROS (superoxide) production than non-induced counter parts. Moreover, higher levels of ROS were detected in BCR-ABL1-positive Lin-c-Kit+Sca1+ stem-enriched population in comparison to BCR-ABL1-positive Lin-c-Kit+Sca1- progenitor population, suggesting a dosage-dependent effect of BCR-ABL1. To confirm that BCR-ABL1 exerts a dosage-dependent effect on ROS-induced oxidative DNA damage, we showed that the levels of ROS, 8-oxoG and DNA double-strand breaks were proportional to BCR-ABL1 kinase expression in murine 32Dc13 and human CD34+ cells. Conclusion:In summary, this mouse model recapitulates the BCR-ABL1 expression profile attributed to stem and progenitor populations in human CML-CP. It also shows that the BCR-ABL1-positive, stem cell-enriched Lin-c-Kit+Sca1+ population displays elevated levels of ROS and oxidative DNA damage in comparison to normal counterparts, which makes it suitable to study the mechanisms of genomic instability in LSCs. Single nucleotide polymorphism (SNP) arrays will shed more light on the genomic instability of this BCR-ABL1-induced transgenic model of CML-CP. Disclosures:Koschmieder:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees.

Radiation-induced DNA damage in patients exposed to X-rays during cerebral angiography

Population exposure to diagnostic and therapeutic ionising radiation is likely to increase worldwide, and this has raised concerns about the stochastic effects of low doses of radiation exposure. The present study was aimed to study the incidence of Chromosomal Aberrations (CAs) in patients exposed to low doses of X-rays during diagnostic interventional radiological procedures. Peripheral blood samples were obtained from 11 individuals who had received low doses of X-rays during cerebral angiography, and DNA damage was measured by the formation of micronuclei (MN), CAs and comet assay. The results show that the frequency of DNA damage, scored as tail length in comets, MN and CAs, increased significantly (P < 0.01) in the samples collected after exposure (2 h and 24 h) when compared with those prior to exposure. However, the observed DNA damage was reduced at 24 h post exposure when compared with those at 2 h. This suggests that the CAs may be eliminated upon cell division, and it is only in rare cases that the accumulation of CAs may pose a risk for stochastic effects. Furthermore, the induced aberration frequency showed an inter-individual variation and repair ability when the cell cycle progressed.

Human cytomegalovirus UL76 induces chromosome aberrations

BackgroundHuman cytomegalovirus (HCMV) is known to induce chromosome aberrations in infected cells, which can lead to congenital abnormalities in infected fetuses. HCMV UL76 belongs to a conserved protein family from herpesviruses. Some reported roles among UL76 family members include involvement in virulence determination, lytic replication, reactivation of latent virus, modulation of gene expression, induction of apoptosis, and perturbation of cell cycle progression, as well as potential nuclease activity. Previously, we have shown that stable expression of UL76 inhibits HCMV replication in glioblastoma cells.MethodsTo examine chromosomal integrity and the DNA damage signal γ-H2AX in cells constitutively expressing UL76, immunofluorescent cell staining and Western blotting were performed. The comet assay was employed to assess DNA breaks in cells transiently expressing UL76.ResultsWe report that stably transfected cells expressing UL76 developed chromosome aberrations including micronuclei and misaligned chromosomes, lagging and bridging. In mitotic cells expressing UL76, aberrant spindles were increased compared to control cells. However, cells with supernumerary centrosomes were marginally increased in UL76-expressing cells relative to control cells. We further demonstrated that UL76-expressing cells activated the DNA damage signal γ-H2AX and caused foci formation in nuclei. In addition, the number of cells with DNA breaks increased in proportion to UL76 protein levels.ConclusionOur findings suggest that the virus-associated protein UL76 induces DNA damage and the accumulation of chromosome aberrations.

Persistent Exposure to Mycoplasma Induces Malignant Transformation of Human Prostate Cells

Recent epidemiologic, genetic, and molecular studies suggest infection and inflammation initiate certain cancers, including those of the prostate. The American Cancer Society, estimates that approximately 20% of all worldwide cancers are caused by infection. Mycoplasma, a genus of bacteria that lack a cell wall, are among the few prokaryotes that can grow in close relationship with mammalian cells, often without any apparent pathology, for extended periods of time. In this study, the capacity of Mycoplasma genitalium, a prevalent sexually transmitted infection, and Mycoplasma hyorhinis, a mycoplasma found at unusually high frequency among patients with AIDS, to induce a malignant phenotype in benign human prostate cells (BPH-1) was evaluated using a series of in vitro and in vivo assays. After 19 weeks of culture, infected BPH-1 cells achieved anchorage-independent growth and increased migration and invasion. Malignant transformation of infected BPH-1 cells was confirmed by the formation of xenograft tumors in athymic mice. Associated with these changes was an increase in karyotypic entropy, evident by the accumulation of chromosomal aberrations and polysomy. This is the first report describing the capacity of M. genitalium or M. hyorhinis infection to lead to the malignant transformation of benign human epithelial cells and may serve as a model to further study the relationship between prostatitis and prostatic carcinogenesis.

An integrative approach for analyzing the interplay of genetic and epigenetic changes in tumors

Abstract The accumulation of chromosomal aberrations is a characteristic feature of tumor development. However, an understanding of tumorigenesis that assumes that changes in DNA copy number always cause equivalent changes in the corresponding RNA and protein levels is an oversimplification and completely ignores the individual genetic and epigenetic context in which an aberration has to be evaluated. We present a brief introduction to various techniques dedicated to the genome-wide analysis of genetic and epigenetic changes, and illustrate how complementary information derived from these various DNA array-based technologies can lead to a better understanding of the consequences of chromosomal aberrations.

An Integrative Approach for Analyzing the Interplay of Genetic and Epigenetic Changes in Tumors

The accumulation of chromosomal aberrations is a characteristic feature of tumor development. However, an understanding of tumorigenesis that assumes that changes in DNA copy number always cause equivalent changes in the corresponding RNA and protein levels is an oversimplification and completely ignores the individual genetic and epigenetic context in which an aberration has to be evaluated. We present a brief introduction to various techniques dedicated to the genome-wide analysis of genetic and epigenetic changes, and illustrate how complementary information derived from these various DNA array-based technologies can lead to a better understanding of the consequences of chromosomal aberrations.