Random aneuploidy and telomere capture in chronic lymphocytic leukemia and chronic myeloid leukemia patients

Sub-fertile sperm cells exemplify telomere dysfunction

PURPOSE

The purpose of this study was to evaluate telomere homeostasis in sub-fertile compared to fertile human sperm.

METHODS

This observational, comparative study included 16 sub-fertile men who required intracytoplasmic sperm injection and 10 fertile men. At least 100 sperm cells from each participant were assessed. Main outcome measures were telomere length and telomere aggregates. Telomerase RNA component (TERC) copy number and telomere capture were assessed using fluorescence in situ hybridization technique and human telomerase reverse transcriptase (hTERT) using immunohistochemistry.

RESULTS

Clinical backgrounds were similar. The percentage of sperm cells with shorter telomeres was higher among the sub-fertile compared to the fertile participants (3.3 ± 3.1 vs. 0.6 ± 1.2%, respectively; P < 0.005). The percentage of cells with telomere aggregates was significantly higher in the sub-fertile group (15.12 ± 3.73 vs. 4.73 ± 3.73%; P < 0.005). TERC gene copy number was similar between groups. The percentage of cells that were positive for hTERT was lower in the sub-fertile group (3.81 ± 1.27 vs. 8.42 ± 1.80%; P < 0.005). Telomere capture rates were higher among the sub-fertile sperm cells (P < 0.005).

CONCLUSIONS

Sub-fertile sperm cells have short telomeres that are elongated by the alternative pathway of telomere capture. Dysfunctional telomeres may affect sperm fertilizability.

Telomere homeostasis in trophoblasts and in cord blood cells from pregnancies complicated with preeclampsia

BACKGROUND

Telomeres are nucleoprotein structures, essential for chromosome stability and cell survival. Telomeres are progressively shortened with each cell division and by environmental factors. Telomere loss has been linked to age and stress-induced premature senescence. Dysfunctional telomeres tend to form aggregates, which consist of the end-to-end fusion of telomeres. Telomere elongation is carried out by telomerase, which is a specific reverse transcriptase capable of adding telomeric repeats to chromosome termini. The TERC gene encodes the RNA template of the telomerase. Another compensatory mechanism that is enhanced in response to telomere shortening and senescence is the telomere capture (TC). Telomere shortening and elevated aggregate formation have been observed in trophoblasts from pregnancies complicated with preeclampsia (PE).

OBJECTIVE

We opted to study mechanisms of telomere shortening in trophoblasts from pregnancies complicated with PE and to assess telomere length and homeostasis in fetal cord blood cells from PE pregnancies.

STUDY DESIGN

Placental specimens and cord blood samples from uncomplicated pregnancies and from pregnancies complicated with PE were collected. Staining with 4',6-diamidino-2-phenylindole was used to assess nuclear fragmentation: senescence-associated heterochromatin foci (SAHF). Fluorescence in situ hybridization was used to evaluate TERC gene copy number and TC. Telomere length and aggregate formation were assessed in cord blood using quantitative fluorescence in situ hybridization. Nonparametric Kruskal-Wallis and Mann-Whitney U tests were applied to test the differences between the study groups.

RESULTS

Nine samples from pregnant patients with PE without intrauterine growth restriction and 14 samples from uncomplicated pregnancies that served as controls were collected. In cord blood cells, no differences were observed in telomere length, aggregate formation, TERC copy number, TC, or SAHF between PE and controls. In PE trophoblasts the percentage of cells with SAHF was higher in PE trophoblasts compared to controls (56.8 SD = 10.5% vs 35.2 SD = 10.7%, P = .028). The percentage of cells with abnormal TERC copy number was increased in PE trophoblasts compared to controls (31 ± 3.6% vs 12.97 SD = 5%, P = .004) as well as the percentage of cells with TC (27.4 SD = 9.4% vs 16 SD = 4.67%, P = .028).

CONCLUSION

We suggest that telomere shortening in PE trophoblasts is linked to cellular increased senescence. Alterations in telomere homeostasis mechanisms are present in such cases. These findings support the role of telomeres in the pathogenesis of trophoblastic dysfunction in PE. The lack of telomere shortening, modified telomere homeostasis mechanisms, and increased senescence in cord blood from pregnancies complicated with PE suggests that these processes are probably restricted primarily to the placenta.

Telomere dysfunction in peripheral blood lymphocytes from patients with primary sclerosing cholangitis and inflammatory bowel disease

BACKGROUND AND AIMS

Primary sclerosing cholangitis and inflammatory bowel disease are two associated, chronic inflammatory, pre-malignant conditions. We hypothesized that patients with these disorders may harbour telomere dysfunction as a marker of chromosomal instability. The aim of our study was to compare parameters of the telomere-telomerase system in these cohorts.

METHODS

In this prospective study, peripheral blood was withdrawn from patients with primary sclerosing cholangitis (N=20), inflammatory bowel disease (N=20) and healthy controls (N=20), and lymphocytes were isolated. Telomere length was quantified as a function of the signal intensity and telomere number. Random aneuploidy and telomere capture were determined by fluorescence in situ hybridization technique with specific probes.

RESULTS

Patients with inflammatory bowel disease had higher measures of intestinal disease activity than patients with primary sclerosing cholangitis. Despite this, shorter telomere length and telomere aggregates, especially the fusion of 2-5 telomeres, were observed at significantly higher rate in patients with primary sclerosing cholangitis relative to inflammatory bowel disease or healthy controls. Rates of aneuploidy and telomere capture were higher in the two probes in both diseases compared to controls (p<0.001).

CONCLUSION

Dysfunction of telomeres was demonstrated in primary sclerosing cholangitis patients more than inflammatory bowel disease and healthy controls patients, which attests to genetic instability and immunosenescence.

TRIAL REGISTRATION NUMBER

NCT02247622.

Significance of telomere capture in myelodysplastic syndromes

Addition of telomeres to the ends of broken chromosomes has been observed in many malignant cells through the capture of the ends of other chromosomes as a result of nonreciprocal translocations. In this study, we aimed to evaluate the percentage of nuclei with telomere capture (TC%) as a prognostic marker in myelodysplastic syndromes (MDS) patients. This study included 45 newly diagnosed MDS patients, 36 cases with denovo MDS and 9 cases with therapy-related MDS, and another 35 apparently healthy volunteers as a control group. Telomere capture percentage was investigated with fluorescent in situ hybridization technique using a probe for 15qter. We found that median TC% rate was significantly increased in those with bad cytogenetic abnormalities, patients with blast cells>10% in BM, and patients categorized as high risk according to WHO and IPSS classification; also, there was a significant negative correlation with progression-free survival. Telomere capture serves as a useful marker for the assessment of MDS patient's risk, and also it had a clinical importance for the early detection of disease progression.

Telomere shortening in intra uterine growth restriction placentas

INTRODUCTION

Placentas from pregnancies complicated with IUGR (intrauterine growth restriction) express altered telomere homeostasis. In the current study, we examined mechanisms of telomere shortening in these placentas.

METHODS

Placental biopsies from 15 IUGR and 15 healthy control pregnancies were examined. The percentage of trophoblasts with fragmented nuclei: senescence-associated heterochromatin foci (SAHF), was calculated using DAPI staining. The amount of human telomerase reverse transcriptase (hTERT) mRNA was evaluated using RtPCR levels of telomere capture using FISH in those samples were estimated.

RESULTS

The percentage of trophoblasts with SAHF was higher in IUGR compared to control samples, (25±13.4% vs. 1.6±1.6%, P<0.0001), hTERT mRNA was decreased (0.5±0.2 vs. 0.9±0.1, P<0.0001) and telomere capture was increased (13.2±9.7% vs.1.3±2.5%, P<0.001).

CONCLUSIONS

We suggest that IUGR placentas express increased signs of senescence as part of the impaired telomere homeostasis. One factor that mediates telomere shortening in these placentas is decreased hTERT mRNA, leading to decreased protein expression and therefore, reduced telomere elongation. Telomere capture, which is a healing process, is increased in IUGR trophoblasts as a compensatory mechanism.

Deficient spindle assembly checkpoint in multiple myeloma

Multiple myeloma (MM) is a hematological disease characterized by an abnormal accumulation of plasma cells in the bone marrow. These cells have frequent cytogenetic abnormalities including translocations of the immunoglobulin heavy chain gene and chromosomal gains and losses. In fact, a singular characteristic differentiating MM from other hematological malignancies is the presence of a high degree of aneuploidies. As chromosomal abnormalities can be generated by alterations in the spindle assembly checkpoint (SAC), the functionality of such checkpoint was tested in MM. When SAC components were analyzed in MM cell lines, the RNA levels of most of them were conserved. Nevertheless, the protein content of some key constituents was very low in several cell lines, as was the case of MAD2 or CDC20 in RPMI-8226 or RPMI-LR5 cells. The recovery of their cellular content did not substantially affect cell growth, but improved their ability to segregate chromosomes. Finally, SAC functionality was tested by challenging cells with agents disrupting microtubule dynamics. Most of the cell lines analyzed exhibited functional defects in this checkpoint. Based on the data obtained, alterations both in SAC components and their functionality have been detected in MM, pointing to this pathway as a potential target in MM treatment.

Telomere aggregates in trisomy 21 amniocytes

Trisomy 21 is the most common chromosomal abnormality among persons with intellectual disability, with a live birth rate of 1 in 800-1,000. As such, this abnormality may serve as a model for human disorders that result from supernumerary copies of a genomic region. Down syndrome carries an increased risk of developing acute leukemia and other malignancies. Telomeres of tumor cells nuclei tend to form aggregates (TA). This study evaluated TA formation in amniocytes from trisomy 21 pregnancies, compared with amniocytes from normal euploid pregnancies. A commercially available peptide nucleic acid telomere kit was used to evaluate TA formation, using two-dimensional fluorescence microscopy. Significantly higher frequencies of TA were found in trisomy 21 amniocytes than in amniocytes from normal pregnancies. The TAs found in trisomy 21 amniocytes apparently represent an additional parameter that reflects the high genetic instability of this syndrome and its recognized predisposition to develop leukemia and other malignancies.

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.

Telomere aggregates in non-Hodgkin lymphoma patients at different disease stages

Telomeres of tumor nuclei tend to form aggregates (TA). The same phenomenon was also observed in premalignant states. The aim of this study was to estimate TA formation in leukocytes of patients with non-Hodgkin lymphoma (NHL) at different disease stages (diagnosis, treatment, relapse, and remission). The peptide nucleic acid Telomere Kit was used to evaluate TA formation, using two-dimensional fluorescence microscopy. A higher rate of TA was found in all the NHL stages (including remission) than in the control group. Significantly higher TA formation was also observed in the relapse group, compared to the diagnosis group. It may be possible that patients with higher TA numbers are prone to relapse. From our previous results involving replication pattern, random aneuploidy rate, and (recently) TA formation, it can be concluded that the patients in remission are at higher risk of developing relapse than the normal population throughout their life span. The genetic instability parameters remain in the cells of these patients, who must continue to be monitored throughout their life.

Random aneuploidy in chronic hepatitis C patients

Hepatitis C virus (HCV) has been recently recognized as a potential cause of B-cell lymphoma. Both chronic hepatitis B and C with or without cirrhosis represent major preneoplastic conditions, and the majority of hepatocellular carcinomas arise in these pathological settings. According to the aneuploidy-cancer theory, carcinogenesis is initiated by random aneuploidy, which is either induced by carcinogens or arises spontaneously. The aim of this study was to evaluate random aneuploidy rate in HCV patients during chronic infection and remission (past infection eradicated), compared with non-Hodgkin lymphoma (NHL) patients and healthy controls. To determine random aneuploidy, we applied the FISH technique with probes for chromosomes 9 and 18. Significantly higher random aneuploidy rate was found in the HCV-infected and lymphoma patients than in the control group; the past HCV group in remission had intermediate rates, between those of the control group and the chronically infected patients. Patients who have eradicated HCV infection may nonetheless carry higher risk for future malignancy and therefore need long-term follow-up.

Changes in the expression of telomere maintenance genes suggest global telomere dysfunction in B-chronic lymphocytic leukemia

In this study, we explored the telomeric changes that occur in B-chronic lymphocytic leukemia (B-CLL), in which telomere length has recently been demonstrated to be a powerful prognostic marker. We carried out a transcriptomic analysis of telomerase components (hTERT and DYSKERIN), shelterin proteins (TRF1, TRF2, hRAP1, TIN2, POT1, and TPP1), and a set of multifunctional proteins involved in telomere maintenance (hEST1A, MRE11, RAD50, Ku80, and RPA1) in peripheral B cells from 42 B-CLL patients and 20 healthy donors. We found that, in B-CLL cells, the expressions of hTERT, DYSKERIN, TRF1, hRAP1, POT1, hEST1A, MRE11, RAD50, and KU80 were more than 2-fold reduced (P < .001), contrasting with the higher expression of TPP1 and RPA1 (P < .001). This differential expression pattern suggests that both telomerase down-regulation and changes in telomeric proteins composition are involved in the pathogenesis of B-CLL.

Random aneuploidy in CML patients at diagnosis and under imatinib treatment

Chronic myeloid leukemia (CML) is characterized by the presence of a BCR-ABL fusion gene, which is the result of a reciprocal translocation between chromosomes 9 and 22, and is cytogenetically visible as a shortened chromosome 22 (Philadelphia). Research during the past two decades has established that BCR-ABL is probably the pathogenetic pathway leading to CML, and that constitutive tyrosine kinase activity is central to BCR-ABL capacity to transform hematopoietic cells in vitro and in vivo. The tyrosine kinase inhibitor imatinib mesylate was introduced into the treatment regimen for CML in 1998. During the last few years, reports on chromosomal changes during imatinib treatment have been described. In this study, we evaluated the random aneuploidy rate with chromosomes 9 and 18 in bone marrow from treated and untreated patients. We found higher aneuploidy rates in both treated and untreated patients compared to the control group. In three patients who were treated with imatinib mesylate for more than 1.5 years, triploidy also appeared in some nuclei. To our knowledge, this is the first report on new chromosomal changes such as random aneuploidy and triploidy under imatinib treatment, but more studies are needed to investigate the long-term effect of the imatinib treatment on genetic instability.

Molecular cytogenetic characteristics of Down syndrome newborns

Down syndrome (DS) is a multifactorial disorder with a high predisposition to leukemia and other malignancies. A change in the replication pattern from synchronous in normal genes to asynchronous in DS amniocytes has previously been reported. The objective of this study was to evaluate additional molecular cytogenetic factors which could re-emphasize the high correlation between DS cells and genetic instability. We found a higher rate of random aneuploidy in chromosomes 9 and 18 and a higher rate of asynchronous replication in the subtelomeric region or DS leukocytes than in cells from normal newborns. In addition, the telomere capture phenomenon was observed in the DS leukocytes but not in normal controls. The molecular cytogenetic factors observed in the DS individuals are known to correlate with genomic instability and with predisposition to cancer.

Telomeres, interstitial telomeric repeat sequences, and chromosomal aberrations

Telomeres are specialized nucleoproteic complexes localized at the physical ends of linear eukaryotic chromosomes that maintain their stability and integrity. The DNA component of telomeres is characterized by being a G-rich double stranded DNA composed by short fragments tandemly repeated with different sequences depending on the species considered. At the chromosome level, telomeres or, more properly, telomeric repeats--the DNA component of telomeres--can be detected either by using the fluorescence in situ hybridization (FISH) technique with a DNA or a peptide nucleic acid (PNA) (pan)telomeric probe, i.e., which identifies simultaneously all of the telomeres in a metaphase cell, or by the primed in situ labeling (PRINS) reaction using an oligonucleotide primer complementary to the telomeric DNA repeated sequence. Using these techniques, incomplete chromosome elements, acentric fragments, amplification and translocation of telomeric repeat sequences, telomeric associations and telomeric fusions can be identified. In addition, chromosome orientation (CO)-FISH allows to discriminate between the different types of telomeric fusions, namely telomere-telomere and telomere-DNA double strand break fusions and to detect recombination events at the telomere, i.e., telomeric sister-chromatid exchanges (T-SCE). In this review, we summarize our current knowledge of chromosomal aberrations involving telomeres and interstitial telomeric repeat sequences and their induction by physical and chemical mutagens. Since all of the studies on the induction of these types of aberrations were conducted in mammalian cells, the review will be focused on the chromosomal aberrations involving the TTAGGG sequence, i.e., the telomeric repeat sequence that "caps" the chromosomes of all vertebrate species.