Replication status as a marker for predisposition for lymphoma in patients with chronic hepatitis C with and without cryoglobulinemia

Asynchronous DNA Replication of Biallelically Expressed Genes in Human Peripheral Blood Lymphocytes as a Prognostic Sign of Cancer

The aim of the study was to identify and quantify lymphocytes with asynchronous replication of the AURKA and TP53 genes in cancer patients versus controls and to assess the diagnostic capabilities of this approach.

Impact of DAA-Based Regimens on HCV-Related Extra-Hepatic Damage: A Narrative Review

Two-third of patients with chronic hepatitis C show extrahepatic manifestations due to HCV infection of B lymphocytes, such as mixed cryoglobulinemia and non-Hodgkin B-cell lymphoma, or develop a chronic inflammatory status that may favor the development of adverse cardiovascular events, kidney diseases or metabolic abnormalities.DAAs treatments induce HCV eradication in 95% of treated patients, which also improves the clinical course of extrahepatic manifestations, but with some limitations. After HCV eradication a good compensation of T2DM has been observed, but doubts persist about the possibility of obtaining a stable reduction in fasting glucose and HbA1c levels.Chronic HCV infection is associated with low total and LDL cholesterol serum levels, which however increase significantly after HCV elimination, possibly due to the disruption of HCV/lipid metabolism interaction. Despite this adverse effect, HCV eradication exerts a favorable action on cardiovascular system, possibly by eliminating numerous other harmful effects exerted by HCV on this system.DAA treatment is also indicated for the treatment of patients with mixed cryoglobulinemia syndrome, since HCV eradication results in symptom reduction and, in particular, is effective in cryoglobulinemic vasculitis. Furthermore, HCV eradication exerts a favorable action on HCV-related lymphoproliferative disorders, with frequent remission or reduction of clinical manifestations.There is also evidence that HCV clearance may improve impaired renal functions, but same conflicting data persist on the effect of some DAAs on eGFR.

Aneuploidy and asynchronous replication in non-alcholic fatty liver disease and cryptogenic cirrhosis

BACKGROUND/AIMS

Non-alcoholic fatty liver disease (NAFLD) and cryptogenic cirrhosis (CC), which is largely a late sequela of NAFLD, are considered pre-neoplastic conditions that might progress to hepatocellular carcinoma. Aneuploidy, telomere aggregates and synchronization of replication were evaluated as markers of genetic instability in these patients.

METHODOLOGY

Peripheral blood lymphocytes from 22 patients with NAFLD, 20 patients with CC and 20 age-matched healthy controls were analyzed. To determine random aneuploidy, we used the fluorescence in situ hybridization (FISH) with probes for chromosomes 9 and 18. The rate of aneuploidy was inferred from the fraction of cells revealing one, three or more hybridization signals per cell. Aggregate size was divided into three fusion groups of 2-5, 6-10 and 11-15 telomeres, relative to the size of a single telomere. The replication pattern was determined by FISH in two pairs of alleles, 15qter and 13qter. Asynchrony was determined by the presence of one single and one set of double dots in the same cell.

RESULTS

Significantly higher random aneuploidy rate was found in the CC patients than in the control group, and to a lesser degree in NAFLD patients. Telomere aggregates were insignificantly higher in both groups. Only patients with CC showed significantly higher rate of asynchronous replication with proportionately more cells with two single dots among the normal cells (p<0.001).

CONCLUSIONS

These results likely reflect changes in gene replication and cell cycle progression in these conditions, possibly correlating with their malignant potential.

Asynchronous Replication in Lymphocytes from Patients with Inflammatory Bowel Disease and Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) are associated chronic inflammatory diseases with malignant potential. Loss of replication synchrony during the S-phase of the cell cycle has been shown to be linked to several malignant and premalignant states. This study evaluated temporal differences in replication timing between these diseases. The replication pattern of peripheral blood lymphocytes obtained from patients with PSC and IBD and healthy individuals was analyzed by fluorescence in situ hybridization (FISH) in 2 pairs of alleles, in 15qter and 13qter. Asynchrony was determined by the presence of 1 single and 1 set of double dots in the same cell. Samples from subjects with PSC showed significantly greater temporal differences in replication timing, in contrast to the high level of synchrony observed in samples from healthy individuals (p = 0.045). Samples from IBD patients exhibited a nonsignificant increase in replication asynchrony. We believe that these results reflect impairment in the replication control of structural homologous loci in PSC, and that this phenomenon may be correlated with the inflammation-induced malignant potential of this condition.

Asynchronous DNA replication and aneuploidy in lymphocytes of hepatocellular carcinoma patients

Using fluorescence in situ hybridization (FISH) analysis, we examined the replication mode of the centromere region (homologous counterpart) and the aneuploidy level of chromosome 17 in the interphase nuclei of phytohaemagglutinin (PHA)-stimulated peripheral blood lymphocytes from (1) patients with hepatocellular carcinoma (HCC); (2) patients with liver cirrhosis (LC) due to hepatitis C viral infection who are individuals at a higher increased risk for HCC; and (3) healthy control participants. We also compared the allelic-replication asynchrony and aneuploidy frequencies with serum alpha-fetoprotein (AFP) levels. We found a significant increase in centromeric replication asynchrony accompanied by a high frequency of aneuploidy in lymphocytes of HCC patients compared with those of LC patients and healthy control participants. These changes are similar to those previously observed in other types of malignancy (hematological, ovarian, prostate, and breast cancer). The cytogenetic alterations of aneuploidy and strong asynchronous replication displayed in the lymphocytes of HCC patients arose from malignancy, as they were associated neither with an increased risk for cancer nor with an infection. The cytogenetic cancer-associated markers observed in patients' lymphocytes appeared to be superior to serum AFP, the marker currently used for HCC. Thus, the cytogenetic cancer-associated markers may be potentially useful in noninvasive cancer detection.

Epigenetic analyses in blood cells of men suspected of prostate cancer predict the outcome of biopsy better than serum PSA levels

Lymphocytes from the peripheral blood of patients with prostate cancer-the most frequent (noncutaneous) tumor in men-display epigenetic aberrations (altered modes of allelic replication) characteristic of the malignant phenotype. The present study aims to determine whether replication aberrations add certainty to the suspicion of prostate cancer provided by the prostate-specific antigen (PSA) blood test. The allelic replication mode (whether synchronous or asynchronous) was exemplified for RB1 and AML1. These two genes normally exhibit a synchronous mode of allelic replication. Fluorescence in situ hybridization (FISH) replication assay was used for replication analyses. The FISH assays were applied to PHA-stimulated lymphocytes, established from peripheral blood samples of 35 men referred to biopsy due to suspected prostate cancer. Following biopsy 13 out of these 35 men were found positive for prostate malignancy. The FISH assay-showing asynchronous or synchronous RB1 and AML1 replication-was able to predict, respectively, the results of all biopsy-positive men and in 18 out of the 22 biopsy-negative ones. These measurements, distinguishing biopsy-positive from biopsy-negative men, were highly significant (P < 10(-8); 100% sensitivity and 81.8% specificity). Yet, distinguishing between the two groups of men based on the PSA measurements was nonsignificant (P > 0.70). The FISH replication assay applied to peripheral blood lymphocytes of 35 men referred for biopsy significantly predicted the outcome of the pathological examination, more precisely than the serum PSA test. As such, the epigenetic alteration offers a potential noninvasive blood marker, complementary to the PSA, for a preliminary prostate cancer diagnosis.

Telomere aggregates in hepatitis C patients

Telomeres of tumor nuclei tend to form aggregates (TA). The aim of this study was to estimate the TA formation in leukocytes of patients with chronic hepatitis C (HCV) which is considered to be premalignant disease, in patients of HCV who eradicated the virus. PNA Telomere kit (Dako) was used to evaluate the TA formation with the utilization of 2D fluorescence microscopy. A higher rate of TA was found in both HCV groups as compared to controls. Our results indicate that HCV patients have some of the components that create the cascade of events leading to malignancies.

Telomere length in Hepatitis C

Telomeres are nucleoprotein structures located at the termini of chromosomes that protect the chromosomes from fusion and degradation. Hepatocyte cell-cycle turnover may be a primary mechanism of telomere shortening in hepatitis C virus (HCV) infection, inducing fibrosis and cellular senescence. HCV infection has been recognized as potential cause of B-cell lymphoma and hepatocellular carcinoma. The present study sought to assess relative telomere length in leukocytes from patients with chronic HCV infection, patients after eradication of HCV infection (in remission), and healthy controls. A novel method of manual evaluation was applied. Leukocytes derived from 22 patients with chronic HCV infection and age- and sex-matched patients in remission and healthy control subjects were subjected to a fluorescence-in-situ protocol (DAKO) to determine telomere fluorescence intensity and number. The relative, manual, analysis of telomere length was validated against findings on applied spectral imaging (ASI) in a random sample of study and control subjects. Leukocytes from patients with chronic HCV infection had shorter telomeres than leukocytes from patients in remission and healthy controls. On statistical analysis, more cells with low signal intensity on telomere FISH had shorter telomeres whereas more cells with high signal intensity had longer telomeres. The findings were corroborated by the ASI telomere software. Telomere shortening in leukocytes from patients with active HCV infection is probably due to the lower overall telomere level rather than higher cell cycle turnover. Manual evaluation is an accurate and valid method of assessing relative telomere length between patients with chronic HCV infection and healthy subjects.

Cryoglobulinemia in chronic hepatitis C: clinical aspects and response to treatment with interferon alpha and ribavirin

INTRODUCTION: The main extra-hepatic manifestation of hepatitis C is mixed cryoglobulinemia (MC). The aim of this study was to evaluate its prevalence among patients with chronic hepatitis C (CHC), to correlate its presence to host and virological variables and to the response to combined therapy with interferon-alpha and ribavirin. CASUISTIC AND METHODS: 202 CHC naive patients (136 with chronic hepatitis and 66 with cirrhosis) were consecutively evaluated for the presence of cryoglobulins. Cryoprecipitates were characterized by immunoelectrophoresis and classified according to the Brouet's criteria. RESULTS: The prevalence of MC was 27% (54/202), and 24% of them (13/54) showed major clinical manifestation of the disease. Even though type III MC was more frequent (78%), symptomatic MC was more common in type II MC. The presence of cirrhosis (RR = 2.073; IC95% = 1.029 - 4.179; p = 0.041), and age of the patients (RR = 1.035; IC95% = 1.008 - 1.062; p = 0.01) were independently associated with the presence of cryoglobulins. No relationship was found with viral load and genotype. 102 patients were treated with interferon alpha and ribavirin. Among these, 31 had MC. Sustained virological response (around 30%) was similar in patients with and without MC (p = 0.971). CONCLUSION: MC represents a prevalent complication in patients with CHC, specially older and cirrhotic patients. Only 24% of these patients show clinical manifestation of the disease, specially those with type II MC. The presence of MC did not affect the response to therapy.

The influence of different chromosomal aberrations on molecular cytogenetic parameters in chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia of adults in Western countries. The most frequent recurring chromosomal aberrations identified in B-CLL patients are trisomy 12 and deletions of 13q, 17p, and 11q. Cases with deletions of 11q and 17p have a poor prognosis, whereas cases with deletions in 13q have a favorable prognosis. It was previously shown that CLL patients with trisomy 12 and del(13)(q14) have a higher rate of asynchronous replication of normal structural genes when compared to those with normal karyotypes. We studied the replication pattern of the structural locus 21q22 and the imprinted gene SNRPN and its telomere (15qter) and the random aneuploidy of chromosomes 9 and 18 in CLL patients with trisomy 12 and deletions of 11q and 17p, and compared the results to those of CLL patients without these aberrations and to healthy controls. Random aneuploidy rate was higher in the group of patients with trisomy 12 as compared to all other groups. The replication pattern with higher asynchronous pattern was found in both aberration groups compared to the CLL patients without the aberrations and to the control group with involvement of 21q22 and 15qter, whereas the highest synchronous group was found in the 2 aberrations CLL patient groups compared to the other groups with the imprinted locus SNRPN. The existence and significance of chromosomal aberrations in CLL have a deleterious effect on the processes of cell cycle and gene replication and may have biological and prognostic implications.

Systematic review: regression of lymphoproliferative disorders after treatment for hepatitis C infection

AIM

To systematically review the experience of therapeutic studies where alpha-interferon with or without ribavirin was administered to patients with lymphoproliferative disorders, in order to evaluate whether eradication of hepatitis C virus may induce regression of lymphoproliferative disorders.

METHODS

We used bibliographical searches in electronic databases and in the Cochrane Library to determine our results.

RESULTS

Sixteen studies where an anti-viral regimen was administered to 65 hepatitis C virus-infected patients with lymphoproliferative disorders were identified. Complete remission of the lymphoproliferative disorder was achieved in 75% of the cases. In contrast, hepatitis C virus-negative subjects did not respond to interferon, indicating that the response in the hepatitis C virus-infected patients is not merely due to the antiproliferative effect of interferon. Remission after HCV eradication was maintained, provided that infection did not reappear. In hepatitis C virus-infected patients with non-Hodgkin's lymphoma treated with corticosteroids/chemotherapy liver function tests deterioration did not occur. The addition of interferon to standard chemotherapy may decrease hepatic side-effects of chemotherapy.

CONCLUSIONS

Although it is evident that larger therapeutical trials of anti-viral therapy are needed to determine the role of this strategy in hepatitis C virus-infected patients with lymphoproliferative disorders, encouraging data emerge from recent studies showing that interferon (plus ribavirin) is an attractive therapeutic option for some hepatitis C virus-related low-grade lymphomas.

Molecular cytogenetic parameters in fibroblasts of ataxia telangiectasia carrier

Ataxia telangiectasia (AT) is a pleiotropic and rare (1:40,000 to 1:100,000) recessive disease. Laboratory investigations have failed to detect any consistent anomaly in cells from AT heterozygotes. To estimate random aneuploidy, we applied a fluorescence in situ hybridization technique with alpha-satellite probes for chromosomes 8 and 9 and replication pattern for RB-1, HER-2/neu, and the imprinted SNRPN loci on primary AT carrier fibroblasts. Higher random aneuploidy was not found in the carrier fibroblasts compared to control amniocytic cells. The asynchrony pattern was higher in the AT carrier cells with the RB-1 locus (P=0.057) and significantly higher with the HER-2/neu locus (P < 0.001) compared to control cells. As for the imprinted locus SNRPN, there was a significantly lower asynchrony rate in the AT carriers (P < 10(-5)) compared to the control group. Molecular cytogenetic parameters of random aneuploidy and replication pattern may reflect predisposition for the development of cancer. It is possible that in some AT carriers the genetic instability phenomena associated with the abnormal replication pattern may represent their potential for developing malignancies.

Altered mode of allelic replication accompanied by aneuploidy in peripheral blood lymphocytes of prostate cancer patients

Replication timing of the genetic material is a highly programmed process correlated with expression, stability and methylation capacity. An important aspect of that timing is the temporal order of allelic replication: a synchronous mode for biallelically expressed genes and an asynchronous for monoallelically expressed genes. Previous studies showed that malignancy is associated with changes in the inherent mode of allelic replication, and even normal cells of cancer patients display alterations in the replication of various genes. Using fluorescence in situ hybridization (FISH), we checked whether allelic-replication mode differentiates cancer patients from healthy individuals. We focused on prostate cancer (CAP), the most common diagnosed cancer and the second leading cause of cancer death in men over 50 years old. Five nonrelated genes and a nontranscribed DNA sequence associated with chromosomal segregation were used in our study. All 6 tested loci displayed in peripheral blood lymphocytes stimulated with phytohemagglutinin (PHA) of CAP patients loss of their inherent temporal order of allelic replication, coupled with aneuploidy, the outcome of chromosome malsegregation. The replication-timing modification is a reversible epigenetic alteration, evidenced by our ability to resurrect the normal pattern in all 6 tested loci by introducing an inhibitor of methyl transferase. On the other hand, the methylation-blocking agent failed to obliterate aneuploidy. The replication alteration accompanied by aneuploidy, detected in peripheral blood cells, distinguishes between CAP patients and individuals with benign prostate hyperplasia (BPH; a common disorder in elderly men) better than the routinely used blood marker, the prostate-specific antigen (PSA).

Molecular cytogenetic parameters in fibroblasts from patients and carriers of xeroderma pigmentosum

Xeroderma pigmentosum (XP) is a rare autosomal recessive syndrome. Laboratory investigations have failed to detect any consistent anomaly in cells from XP heterozygotic subjects, although examples of behavior intermediate between normal and XP cells have been reported. To estimate random aneuploidy we applied fluorescence in situ hybridization (FISH) with alpha-satellite probes for chromosomes 8 and 9 and replication pattern for TP53 (p53), ERBB2 (HER-2/neu), and MYCN (N-MYC) loci and for the imprinted SNRPN locus. A significantly higher rate of aneuploidy rate was observed in XP patients and carriers than in controls. The asynchrony pattern was significantly higher in XP carriers and patients with all three coding loci analyzed and significantly lower in XP patients and carriers with the imprinted locus SNRPN than in the control group. Molecular cytogenetic parameters such as random aneuploidy and replication pattern, which are known to reflect chromosomal instability, may be part of the tumorigenesis process. In XP patients and carriers, this genetic instability may represent a potential for developing malignancies.

Granulocyte colony-stimulating factor generates epigenetic and genetic alterations in lymphocytes of normal volunteer donors of stem cells

OBJECTIVE

Because the effect of granulocyte colony-stimulating factor (G-CSF), which is widely used for allogeneic stem cell transplantation, on DNA function and stability has not yet been unequivocally elucidated, the aim of this study was to determine whether G-CSF leads to epigenetic and/or genetic modifications.

MATERIALS AND METHODS

Molecular cytogenetic techniques based on fluorescence in situ hybridization technology were used.

RESULTS

Lymphocytes of G-CSF mobilized donors displayed epigenetic (altered replication timing of alleles) and genetic (aneuploidy) alterations similar to those observed in lymphocytes of cancer patients. Specifically, in the donors' lymphocytes, biallelically expressed genes (TP53 and AML1) and a repetitive noncoding DNA sequence associated with chromosome segregation (CEN17) showed loss of synchrony in allelic replication timing (allele-specific replication). Each displayed a highly asynchronous pattern of allelic replication similar to that characterizing monoallelic expressed genes. This non-locus-specific epigenetic phenomenon, which also affects DNA sequences associated with chromosome segregation, was accompanied by aneuploidy. Although the loss of replication synchrony in the lymphocytes of G-CSF mobilized donors was a transient epigenetic modification, aneuploidy remained unchanged. The G-CSF effect also was observed after G-CSF administration in vitro. 5-Azacytidine, a DNA methylation blocking agent, inhibited G-CSF in vitro induction of allele-specific replication.

CONCLUSION

G-CSF, probably via changes in DNA methylation capacity, leads to cancer-characteristic DNA modifications in lymphocytes of normal mobilized donors.

Modified allelic replication in lymphocytes of patients with neurofibromatosis type 1

Transcription activity of genes is related to their replication timing, accordingly gene activation is coupled with a shift from late replication to early replication and vice versa. The relationship between replication timing and gene expression is best manifested by monoallelically expressed genes which show an asynchronous pattern of allelic replication, with the active allele replicating earlier than the inactive counterpart. Biallelically expressed genes, which normally replicate highly synchronously, when present in lymphocytes derived from patients with various types of malignancies or premalignancies, replicate highly asynchronously, similar to monoallelically expressed genes. Since neurofibromatosis-type 1 (NF1) patients are at an increased risk to develop malignancies, we used the fluorescence in situ hybridization (FISH) replication assay and evaluated the level of replication synchrony of three cancer-implicated genes (RB1, AML1, and CMYC) in lymphocytes derived from patients with NF1 without malignancy. Each gene, which normally displayed synchrony in allelic replication, in the patients' cells displayed loss of synchrony. The loss of replication synchrony, of each gene, in the patients' cells was achieved by an advanced replication of a single allele, which replicated remarkably earlier than its normal scheduled timing. In addition, the second allele showed slightly earlier replication timing than that normal for the gene. Thus, it is assumed that the NF1 condition is associated with activation of cancer-implicated genes that may be the cause for increased risk of patients to develop malignancies. As loss of synchrony in allelic replication timing differentiates well between NF1 patients and control subjects, this marker may have a potential use for identification of presymptomatic carriers of NF1 disorders.

The effect of chlorambucil treatment on cytogenetic parameters in chronic lymphocytic leukemia patients

The most common treatment of chronic lymphocytic leukemia (CLL) is the alkylating agent chlorambucil (CLB), with or without prednisone. In the present study, our aim was to evaluate whether treatment with CLB for more than one year induced genetic changes manifested by comparative genomic hybridization (CGH) as new chromosomal aberrations. We also studied whether CLB affected the pattern of replication by using fluorescence in situ hybridization (FISH). We found a similar rate of asynchronous pattern of replication in both treated and untreated patients with CLL. Most of the aberrations found with CGH were previously reported in CLL. More prognostically unfavorable aberrations and more cases with genetic changes were found in the treated group. The changes found were not typical of the secondary genetic aberrations associated with alkylating agents. Thus, we conclude that treatment of CLL with CLB for at least a year does not affect the parameters analyzed in this study. Longer studies are needed to further explore the effects of alkylating agents on normal and malignant cells.

Hepatitis C virus infection and B-cell non-Hodgkin's lymphomas: more than a simple association

Several studies have reported that the prevalence of the hepatitis C virus (HCV) infection is significantly overrepresented in patients affected by non-Hodgkin's lymphoma (NHL), thus suggesting that besides the well-established link with essential mixed cryoglobulinemia, a possible role for HCV is determining the development of at least some types of B-cell NHL. Such an association, however, seems to be limited to geographic areas where the presence of HCV is more relevant or endemic. According to a multistep pathogenetic model based on a large series of clinical, immunological, histological, and molecular evidences, an HCV antigen-driven polyclonal B-cell lymphoproliferation could be the initial phase of a process leading, in a variable time, into a true clonal disease. Particular genetic and environmental backgrounds could play a role in the development of a malignant phenotype, while specific HCV genotypes do not seem to be relevant in this setting. Hepatitis C virus correlated with NHL often shows some distinctive clinicopathological features, such as older age, liver damage, presence of monoclonal gammopathy (often with no clinically relevant cryoglobulinemic and/or rheumatoid activity), increased rate of autoimmune disorders, extranodal localizations, and restricted histological subtypes. Overall, the clinical outcome of HCV-positive NHL does not seem to be different from that of NHL patients without HCV infection. However, the evidence of a significant hepatic injury may predict a worse prognosis in these subjects.

Allele-specific replication associated with aneuploidy in blood cells of patients with hematologic malignancies

We hypothesize that coordination between the two DNA parental sets in somatic cells is essential for the stability of the diploid genome, and that its disruption is associated with the many alterations observed in the various cancerous phenotypes. As coordination between two allelic counterparts is well exemplified by synchrony in replication timing, we examined, in blood cells of patients suffering from various hematologic malignancies, replication patterns of five loci. These loci were three cancer-implicated genes (TP53, AML1, and RB1) and two nontranscribed sequences engaged in chromosome segregation. All five loci normally display synchrony in allelic replication timing. In addition, in order to exemplify an asynchronous mode of allelic replication, we followed the replication of allelic counterparts of an imprinted gene (SNRPN), which is distinguished by its asynchronous mode of allelic replication (allele-specific replication). Allelic replication patterns were studied by fluorescence in situ hybridization (FISH), which has been shown to distinguish between nonreplicated and replicated regions of the genome in interphase cells, based on the structure of the specific hybridization signals that are being detected. Using the FISH replication assay we observed, for all loci which normally exhibit synchrony in allelic replication, loss of synchrony when present in blood cells of patients with hematologic malignancies. The loss of synchrony in allelic replication in patients' cells was accompanied by aneuploidy (chromosome losses and gains), the hallmark of cancer. We were able to reinstate the normal pattern of replication in the patients' cells by introducing an inhibitor of DNA methylation. It thus appears loss of allelic coordination is an epigenetic alteration characterizing cancer, which is easily identified by simple cytogenetic means and has a potential use in both cancer investigation and detection.

Combing the genome for genomic instability

Genomic instability is one of the major features of cancer cells. The clinical phenotypes associated with several human diseases have been linked to recurrent DNA rearrangements and dysfunction of DNA replication processes that involve unstable genomic regions. Analysis of these rearrangements, which are frequently submicroscopic and can lead to loss or gain of dosage-sensitive genes or gene disruption, requires the development of sensitive, high-resolution techniques. This will lead to a better understanding of the mechanisms underlying genome instability and a greater awareness of the role of chromosomal rearrangements in disease. A new technology that involves molecular combing, a method that permits straightening and aligning molecules of genomic DNA, should make possible a detailed analysis of genomic events at the level of single DNA molecules. Such a single molecule approach could help to elucidate important properties that are masked in bulk studies.

Replication status in leukocytes of treated and untreated patients with polycythemia vera and essential thrombocytosis

The replication status of malignant cells is usually asynchronous. However, to date the pattern of replication has not been studied in myeloproliferative disorders nor has the effect of chemotherapy been systematically evaluated. Therefore, we used fluorescence in situ hybridization to interphase nuclei in PHA-stimulated peripheral blood lymphocytes to examine replication timing of three alleles associated with the malignant process. The study group comprised hydroxyurea treated and untreated patients with essential thrombocytosis (ET) or polycythemia vera (PV). A significantly higher rate of the asynchronous pattern of replication in both treated and untreated patients was found as compared to healthy controls. The highest rate of asynchronous replication was observed in untreated patients. Also, the frequency of the two doublets pattern was significantly higher in the untreated group compared to the treated patients and to the control groups. In conclusion, patients with PV and ET have a higher rate of asynchronous pattern of replication. A possible correlation between disease activity and the pattern of replication is suggested. The effect of hydroxyurea on the pattern of replication is variable.

Modified order of allelic replication in lymphoma patients at different disease stages

Asynchronous replication of homologous loci was reported in lymphocytes of patients with lymphoma, ovarian and renal cancer as well as in lymphocytes of patients with premalignant conditions, for example, essential mixed cryoglobulinemia associated with hepatitis C virus and in monoclonal gammopathy of unknown significance. In the present study we evaluated the replication pattern in lymphocytes of four groups of patients with intermediate grade of non-Hodgkin lymphoma at various stages of their disease: 1) at diagnosis; 2) during cytotoxic treatment; 3) in remission; and 4) in relapse. A significantly higher proportion of the asynchronous pattern of replication at diagnosis, during cytotoxic treatment, and in relapse was noted as compared to healthy controls and to patients who achieved remission of their lymphoma. Also, the frequency of the two doublets (DD) pattern in every group studied was significantly lower than in the controls. If our findings can be confirmed in larger, long-term prospective studies, it may allow the use of a simple and inexpensive tool to closely observe patients with lymphoma who are at high risk for relapse.

The influence of cytogenetic aberrations on gene replication in chronic lymphocytic leukemia patients

Chronic lymphocytic leukemia (CLL) is the most common leukemia in humans, with the major cytogenetic aberrations of trisomy 12 and deletion of 13q14. This study examined the influence of these aberrations on general gene replication. The study group included three subgroups: (1) 15 CLL patients, (2) 4 CLL patients with trisomy 12, (3) 3 CLL patients with deletions in 13q14. Five healthy individuals served as a control group. Monocolor fluorescence in situ hybridization (FISH) with probes for c-myc, HER-2/neu, and p53 was applied to lymphocyte nuclei for the evaluation of replication timing. Asynchronous replication (SD) rate was significantly higher in all CLL patients (P < 0.01) when compared to the control group and was even higher in the group of CLL patients with trisomy 12 and 13q14 deletion (P < 0.01). The asynchrony rate was significantly higher in cells with trisomy 12 for all three probes analyzed, compared to "healthy" cells in the same patients (P < 0.001). To conclude, in CLL patients with a chromosomal aberration such as trisomy 12 and 13q14 deletion we were able to demonstrate a high rate of asynchrony of replication. The high correlation between cells with trisomy 12 and SD pattern could reflect direct influence of the aberration on gene replication and cell cycle control.