Shelterin Complex Genes Research Articles

Different phenotypes with different endings-Telomere biology disorders and cancer predisposition with long telomeres.

Rare germline pathogenic variants (GPVs) in genes essential in telomere length maintenance and function have been implicated in two broad classes of human disease. The telomere biology disorders (TBDs) are a spectrum of life-threatening conditions, including bone marrow failure, liver and lung disease, cancer and other complications caused by GPVs in telomere maintenance genes that result in short and/or dysfunctional telomeres and reduced cellular replicative capacity. In contrast, cancer predisposition with long telomeres (CPLT) is a disorder associated with elevated risk of a variety of cancers, primarily melanoma, thyroid cancer, sarcoma, glioma and lymphoproliferative neoplasms caused by GPVs in shelterin complex genes that lead to excessive telomere elongation and increased cellular replicative capacity. While telomeres are at the root of both disorders, the term TBD is used to convey the clinical phenotypes driven by critically short or otherwise dysfunctional telomeres and their biological consequences.

Telomere Status of Advanced Non-Small-Cell Lung Cancer Offers a Novel Promising Prognostic and Predictive Biomarker

Telomere length appears to correlate with survival in early non-small-cell lung cancer (NSCLC), but the prognostic impact of telomere status in advanced NSCLC remains undetermined. Our purpose was to evaluate telomere parameters as prognostic and predictive biomarkers in advanced NSCLC. In 79 biopsies obtained before treatment, we analyzed the telomere length and expression of TERT and shelterin complex genes (TRF1, TRF2, POT1, TPP1, RAP1, and TIN2), using quantitative PCR. Non-responders to first-line chemotherapy were characterized by shorter telomeres and low RAP1 expression (p = 0.0035 and p = 0.0069), and tended to show higher TERT levels (p = 0.058). In multivariate analysis, short telomeres were associated with reduced event-free (EFS, p = 0.0023) and overall survival (OS, p = 0.00041). TERT and TRF2 overexpression correlated with poor EFS (p = 0.0069 and p = 0.00041) and OS (p = 0.0051 and p = 0.007). Low RAP1 and TIN2 expression-levels were linked to reduced EFS (p = 0.00032 and p = 0.0069) and OS (p = 0.000051 and p = 0.02). Short telomeres were also associated with decreased survival after nivolumab therapy (p = 0.097). Evaluation of telomere status in advanced NSCLC emerges as a useful biomarker that allows for the selection of patient groups with different clinical evolutions, to establish personalized treatment.

Novel Germline POT1 Variant Predisposes to Childhood Acute Myeloid Leukemia

Introduction: Current studies indicate a contribution of germline predisposition in the development of approximately 8.5% of childhood cancers (Zhang J. et al., N Engl J Med, 2015), although their apparent rate is estimated to be much higher. Understanding tumor evolution based on a predisposed cell can open unknown doors for prevention and therapy of childhood cancer e.g., leukemia. Here we present a novel rare (MAF<0.1%) germline POT1 variant (Q199*) predisposing to acute myeloid leukemia (AML). POT1 as part of the telomeric shelterin complex is known to play an important role in DNA damage protection, telomere length maintenance and chromosomal stability (Calvete O. et al., Nat. Commun., 2015). POT1 variants are associated with a broad range of cancer, including myeloid and lymphoid neoplasms in adults (Lim T.L. et al., Leukemia, 2021), but not yet described for myeloid malignancies in childhood.Methods: Whole exome sequencing (WES) was implemented to identify germline variants. To assess the effect of POT1 p.Q199*, patient's fibroblast and stably transfected HEK293T cells were used as cell models. The variant's functional impact was experimentally tested performing yH2AX and 53BP1 immunofluorescence assays for DNA damage detection, qRT-PCR for telomere length measurement and telomere FISH to assess chromosomal instability.Results: Utilizing WES to detect variants within shelterin complex genes we analyzed genomic data of an unselected German parent-child cohort of children with cancer (n=60, TRIO-DD), as well as a recently published parent-child pediatric cancer cohort (n=158, TRIO-D) (Wagener R. et al., Eur. J. Hum. Genet, 2021). Here, we identified a novel germline POT1 variant in a boy affected with Myelodysplastic syndrome (MDS) and secondary AML (7q-). This novel germline variant constitutes a stop-gain mutation causing a substitution of the amino acid Glutamine by a stop codon (p.Q199*).QRT-PCR analysis within the patient's fibroblasts showed a significant (student's t-test p=0.0037) reduction of POT1 mRNA expression to ≈0.5 compared to POT1 wildtype. Western Blot analysis revealed reduced POT1 levels, confirming the loss of one POT1 allele mediated by p.Q199*. Thereupon, POT1 p.Q199* cloning and stable transfection into Hek293T cells was performed to test the variant's cooperative functionality in a controlled environment. Subsequently, POT1 p.Q199* lead to a drastically significant (student's t-test p=<0.001) increase of DNA double strand breaks in transfected Hek293T cells determined by yH2AX and 53BP1 immunofluorescence assays, which is in line with a deregulated DNA damage response and inappropriate repair by non-homologous end joining.In addition, we detected dysregulation of telomere length maintenance. Here, relative telomere length measurement by means of qRT-PCR indicated significant (student's t-test p=0.019) telomere elongation in POT1 p.Q199* fibroblast cells. Furthermore telomere FISH on metaphase chromosomes was performed to analyse chromosomal stability. In POT1 p.Q199* Hek293T cells we identified a significant (student's t-test p=0.002) increase in telomere fragility compared to POT1 WT cells.Conclusion: Taken together, we present the functional effects of POT1 p.Q199* leading to a significant increase of DNA damage, telomere length and chromosomal instability. Our results on functional dysregulation strengthen a potential genetic predisposition to childhood AML mediated by germline POT1 variants. DisclosuresNo relevant conflicts of interest to declare.

Dynamic of Telomeric Parameters in Relapsing or Refractory (R/R) Chronic Lymphocytic Leukemia (CLL), an Analysis of the Filo ICLL001 Bomp Trial

Dynamic of Telomeric Parameters in Relapsing or Refractory (R/R) Chronic Lymphocytic Leukemia (CLL), an Analysis of the Filo ICLL001 Bomp Trial

Low-power infrared laser modulates telomere length in heart tissue from an experimental model of acute lung injury

Acute lung injury and acute respiratory distress syndrome can occur as a result of sepsis. Cardiac dysfunction is a serious component of multi-organ failure caused by severe sepsis. Telomere shortening is related to several heart diseases. Telomeres are associated with the shelterin protein complex, which contributes to the maintenance of telomere length. Low-power infrared lasers modulate mRNA levels of shelterin complex genes. This study aimed to evaluate effects of a low-power infrared laser on mRNA relative levels of genes involved in telomere stabilization and telomere length in heart tissue of an experimental model of acute lung injury caused by sepsis. Animals were divided into six groups, treated with intraperitoneal saline solution, saline solution and exposed to a low-power infrared laser at 10 J cm−2 and 20 J cm−2, lipopolysaccharide (LPS), and LPS and, after 4 h, exposed to a low-power infrared laser at 10 J cm−2 and 20 J cm−2. The laser exposure was performed only once. Analysis of mRNA relative levels and telomere length by RT-qPCR was performed. Telomere shortening and reduction in mRNA relative levels of TRF1 mRNA in heart tissues of LPS-induced ALI animals were observed. In addition, laser exposure increased the telomere length at 10 J cm−2 and modulated the TRF1 mRNA relative levels of at 20 J cm−2 in healthy animals. Although the telomeres were shortened and mRNA levels of TRF1 gene were increased in nontreated controls, the low-power infrared laser irradiation increased the telomere length at 10 J cm−2 in cardiac tissue of animals affected by LPS-induced acute lung injury, which suggests that telomere maintenance is a part of the photobiomodulation effect induced by infrared radiation.

High-fat diet induced obesity and age influence the telomere shelterin complex and telomerase gene expression in mouse adipose tissue.

Obesity and aging are linked to inflammation and increased risk of chronic disease. Telomeres are the endcaps of chromosomes that are regulated by telomerase, the enzyme that elongates telomeres, as well as a protein complex known as shelterin. Telomere dysfunction is associated with inflammation, aging, and disease. However, the effect of high‐fat diet (HFD) induced obesity and advancing age on the shelterin complex and telomerase in adipose tissue is unknown. The present study investigated the effects of obesity and aging on C57BL/6J mice adipose tissue mRNA expression of shelterin complex genes. Young (YG) mice (3 mo) were randomly assigned to be fed either a high‐fat diet (YG + HFD; 60% kcal from fat) or a low‐fat diet (YG + LFD; 10% kcal from fat). A subset of mice were aged until 16 months. Body weight and epididymal white adipose tissue (EWAT) weight increased with age or a HFD. There was a trend for increased Terf2 expression, as expression was increased in HFD + YG by ~47% and aged mice by ~80%. Pot1b expression was increased in aged mice by ~35%–60% compared to YG, independent of diet. mTert, the gene that codes for the catalytic subunit of telomerase, was significantly elevated in aged mice. Changes in telomere associated gene expression was accompanied by changes in expression of inflammatory markers Mcp1 and Tnfα. These findings suggest obesity and age impact expression of shelterin complex and telomerase related genes in adipose, perhaps altering telomere function in adipose tissue thereby increasing inflammation and risk of chronic disease.

Initiation of Pulmonary Fibrosis after Silica Inhalation in Rats is linked with Dysfunctional Shelterin Complex and DNA Damage Response

Occupational exposure to silica has been observed to cause pulmonary fibrosis and lung cancer through complex mechanisms. Telomeres, the nucleoprotein structures with repetitive (TTAGGG) sequences at the end of chromosomes, are a molecular “clock of life”, and alterations are associated with chronic disease. The shelterin complex (POT1, TRF1, TRF2, Tin2, Rap1, and POT1 and TPP1) plays an important role in maintaining telomere length and integrity, and any alteration in telomeres may activate DNA damage response (DDR) machinery resulting in telomere attrition. The goal of this study was to assess the effect of silica exposure on the regulation of the shelterin complex in an animal model. Male Fisher 344 rats were exposed by inhalation to Min-U-Sil 5 silica for 3, 6, or 12 wk at a concentration of 15 mg/m3 for 6 hr/d for 5 consecutive d/wk. Expression of shelterin complex genes was assessed in the lungs at 16 hr after the end of each exposure. Also, the relationship between increased DNA damage protein (γH2AX) and expression of silica-induced fibrotic marker, αSMA, was evaluated. Our findings reveal new information about the dysregulation of shelterin complex after silica inhalation in rats, and how this pathway may lead to the initiation of silica-induced pulmonary fibrosis.

Abstract 1226: Rare germline variants segregating in chronic lymphocytic leukemia (CLL) families

Abstract CLL is a highly heritable cancer with first degree relatives of CLL cases having a 7.5-fold increased CLL risk. Genome-wide association studies (GWAS) and linkage studies have been performed to study inherited predisposition; however a larger proportion of heritability to CLL remains unexplained. Rare coding variants might account for the missing heritability information. Inherited loss of function variants in shelterin complex genes (POT1, ACD, TERF1, TINF2, TERF2, TERF2IP- involved in telomere regulation), CDK1 (critical for cell division) and ATM (tumor suppressor gene) have been found to co-segregate in CLL families and be enriched in CLL cases using exome-wide sequencing data. Our study evaluates rare germline variants from these suspect genes segregating in CLL families who are followed at the Mayo Clinic. Using whole exome sequencing (WES), we sequenced 93 CLL families with at least 2 reported CLL cases consisting of 443 individuals: 160 with CLL, 73 with monoclonal B-cell lymphocytosis (MBL), and 210 relatives. DNA was extracted from buccal cells, coding exons were selectively captured using Agilent 50Mb and SureSelect Human All Exon V4 capture kits; sequencing was performed using Illumina HiSeq 2000. Mayo Clinic's DNASeq pipeline uses Novoalign (initial read alignment), Picard (marking duplicate reads), and the Genome Analysis Toolkit (GATK) for local realignment, recalibration, and variant calling. The variant discovery step leverages GATK's HaplotypeCaller in per sample mode and all of the samples across the cohort are jointly genotyped together. All called variants are evaluated with GATK's Variant Quality Score Recalibration tool and annotated for biological relevance (BIOR). Quality control included removing variants that had &amp;lt;75% call rate across the two capture kits, &amp;lt;8x coverage, or phred score&amp;lt;10, resulting in 317,666 remaining variants. Of these, over 80% of the coding sequence had a median read depth of 23 reads. In our pedigrees, we searched for rare variants within the genes described above. We identified suspect variants with the following criteria: 1) enriched in CLL and MBL samples compared to unaffected samples; 2) multiple affected members with the variant within a family; 3) variants present in all sequenced affecteds within the family; 4) rarely seen in an in-house database of non-cancer controls or 1K Genomes; and 5) predicted to have a functional damaging effect (using SIFT). We identified three novel rare missense variants, defined as functionally deleterious, which each co-segregated within a CLL family. Specifically, these variants from shelterin complex genes; POT1 (rs116916706), TERF2IP (rs138458227), and TERF2 (rs749171225), met the criteria. This study further highlights telomere dysregulation as a key process in CLL development. Investigating rare variants within CLL pedigrees with WES can help identify germline variants impacting predisposition to familial CLL. Citation Format: Alyssa I. Clay-Gilmour, Daniel R. O'Brien, Sara J. Achenbach, Celine M. Vachon, Kari G. Chaffee, Timothy G. Call, Jose F. Leis, Aaron D. Norman, Brian F. Kabat, Sameer A. Parikh, Neil E. Kay, Esteban Braggio, James R. Cerhan, Susan L. Slager. Rare germline variants segregating in chronic lymphocytic leukemia (CLL) families [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1226.

Abstract 3687: Dot1l inhibition selectively impairs androgen receptor dependent prostate cancer growth through loss of telomere integrity

Abstract The histone methyltransferase DOT1L methylates lysine 79 (K79) on histone H3 and this histone mark is associated with activation of gene expression. DOT1L has a well-known role in MLL fusion leukemogenesis, however, its role in prostate cancer is yet to be elucidated. Here we show that DOT1L is overexpressed in many solid tumors including prostate cancer and is associated with a poor outcome. Genetic and chemical targeting of DOT1L showed a preferential loss in cell viability and colony formation in androgen receptor (AR)-signaling competent prostate cancer cells, including castration-resistant and enzalutamide-resistant cells. DOT1L inhibition reduced AR levels and upregulated enzymes involved in testosterone catabolism but only affected the expression of a subset of AR target genes. More importantly, loss of DOT1L selectively impaired telomere integrity by promoting telomere uncapping and shortening in AR-signaling competent cells. DOT1L inhibition also reduced the expression of telomerase and Shelterin complex genes including TRF2 and POT1. Recruitment of AR to telomeres and K79 methylation at sub-telomeric regions was also diminished. Consequently, loss of DOT1L leads to induction of Telomere dysfunction induced foci (TIF) and activates a cellular senescence program in these cells. Hence, these results provide compelling evidence for DOT1L inhibition as a novel therapeutic approach in advanced prostate cancers. Citation Format: Rajita Vatapalli, Yara Rodriguez, Changsheng Zhao, Vinay Sagar, Jonathan Anker, Sahithi Pamarthi, Kenji Unno, Benedito Carneiro, Debabrata Chakravarti, Sarki Abdulkadir. Dot1l inhibition selectively impairs androgen receptor dependent prostate cancer growth through loss of telomere integrity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3687.

Abstract 1243: Elucidating the molecular pathogenesis of familial glioma

Abstract INTRODUCTION: In recent years, the molecular characterization of sporadically arising diffuse gliomas has identified recurrent driving alterations and delineated molecularly and clinically distinct subclasses of disease. However, less is known about the molecular nature of gliomas that are familial in origin. To address this question, we integrated germline and somatic genomic data to characterize the molecular pathogenesis of 20 tumors arising in unrelated individuals with a family history of glioma collected through the Gliogene International Consortium. METHODS: FFPE tumor specimens were sectioned and reviewed to localize neoplastic tissue for DNA extraction. Library preparation, exome plus targeted capture, and paired-end sequencing on the Illumina HiSeq 2000 platform was performed at the Baylor College of Medicine Human Genome Sequencing Center. Single-nucleotide variants and indels were called with respect to germline DNA sequencing data for each case using MuTect2. Copy number profiling was performed on the Illumina HumanOmniExpress BeadChip and analyzed using GenomeStudio v2.0. Genotypes at known glioma risk polymorphisms were determined from germline DNA profiled on the Illumina Infinium OncoArray and rare, predicted deleterious germline mutations were identified from germline whole-exome sequencing data. RESULTS: Tumor exome sequencing was completed at an average read depth of 116X and we detected a median of 54 non-silent somatic mutations per tumor across the 20 tumors profiled. All three molecular subtypes of sporadic glioma were represented, including IDH-mutant, 1p/19q codeleted (n=3), IDH-mutant, 1p/19q intact (n=7), and IDH-wildtype tumors (n=10). Characteristic subtype-specific mutations and copy number alterations (e.g., TP53 and ATRX mutations among IDH-mutant, 1p/19q intact tumors) were observed, and the frequencies of recurrent alterations were comparable to sporadic glioma cases analyzed by The Cancer Genome Atlas. Notably, all 20 cases had alterations in genes regulating telomere length; 17 had acquired mutations in ATRX or the TERT promoter as typically seen in sporadic glioma, while three instead had germline mutations in telomere shelterin complex genes POT1 or TERF2. Frequencies of known common glioma risk alleles were similar to those among sporadic cases and correlations between risk alleles and specific somatic mutations were not observed. CONCLUSIONS: This study illustrates: 1) the complementarity of inherited and acquired alterations in driving gliomagenesis in some individuals with a familial predisposition to the disease; and 2) that the molecular characteristics of familial tumors profiled largely recapitulate what is known about sporadic glioma. In the majority of cases, the source of germline genetic susceptibility is not known but does not appear to be conferred by common risk polymorphisms. Citation Format: Daniel I. Jacobs, Kazutaka Fukumura, Matthew N. Bainbridge, Georgina N. Armstrong, Donna M. Muzny, Beatrice Melin, Jason T. Huse, Melissa L. Bondy. Elucidating the molecular pathogenesis of familial glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1243.

Telomere length variation and expression analysis of shelterin complex genes during gallbladder carcinogenesis.

Telomeres, which are bound with shelterin protein complex, play an important role in maintaining genomic stability and its dysfunction may lead to carcinogenesis. Here, we aimed to analyze whether shelterin complex gene expression and telomere length variation, play any role in gallbladder carcinogenesis. Telomere length analysis was carried out by monochrome multiplex qPCR, whereas expression analysis of shelterin genes was carried out using RT-qPCR. Statistical analysis was carried out using SigmaPlot 11 software. We found significantly reduced telomere length in tumor tissues, and this reduction was seen in both, tumors with or without gallstones in comparison to adjacent non tumor and gallstone (chronic calculous cholecystitis: Inflamed) tissues. Inflamed tissues showed increased telomere length as compared to both adjacent non tumor and tumor tissues. Expression analysis of five shelterin genes showed significant downregulation of TERF1, POT1, and TINF2 genes in inflamed tissues as compared to non tumor and tumor tissues. POT1 was also found to be significantly upregulated in tumor tissues and specifically in tumor tissues with gallstones compared to inflamed tissues. This study, thus, suggests that, gallstone does not affect telomere length and even after having increased telomere length, decreased expression of some shelterin genes in inflamed tissue might cause telomeres to cap improperly, possibly leading to telomere dysfunction and further, gallbladder carcinogenesis. Also, increased expression of POT1 in tumor tissues with gallstones could act as a diagnostic marker in patients with gallstones.

Germ line mutations in shelterin complex genes are associated with familial chronic lymphocytic leukemia

AbstractChronic lymphocytic leukemia (CLL) can be familial; however, thus far no rare germ line disruptive alleles for CLL have been identified. We performed whole-exome sequencing of 66 CLL families, identifying 4 families where loss-of-function mutations in protection of telomeres 1 (POT1) co-segregated with CLL. The p.Tyr36Cys mutation is predicted to disrupt the interaction between POT1 and the telomeric overhang. The c.1164-1G>A splice-site, p.Gln358SerfsTer13 frameshift, and p.Gln376Arg missense mutations are likely to impact the interaction between POT1 and adrenocortical dysplasia homolog (ACD), which is a part of the telomere-capping shelterin complex. We also identified mutations in ACD (c.752-2A>C) and another shelterin component, telomeric repeat binding factor 2, interacting protein (p.Ala104Pro and p.Arg133Gln), in 3 CLL families. In a complementary analysis of 1083 cases and 5854 controls, the POT1 p.Gln376Arg variant, which has a global minor allele frequency of 0.0005, conferred a 3.61-fold increased risk of CLL (P = .009). This study further highlights telomere dysregulation as a key process in CLL development.

Germline mutations in shelterin complex genes are associated with familial glioma.

Gliomas are the most common brain tumor, with several histological subtypes of various malignancy grade. The genetic contribution to familial glioma is not well understood. Using whole exome sequencing of 90 individuals from 55 families, we identified two families with mutations in POT1 (p.G95C, p.E450X), a member of the telomere shelterin complex, shared by both affected individuals in each family and predicted to impact DNA binding and TPP1 binding, respectively. Validation in a separate cohort of 264 individuals from 246 families identified an additional mutation in POT1 (p.D617Efs), also predicted to disrupt TPP1 binding. All families with POT1 mutations had affected members with oligodendroglioma, a specific subtype of glioma more sensitive to irradiation. These findings are important for understanding the origin of glioma and could have importance for the future diagnostics and treatment of glioma.

Abstract 550: Genomic instability and telomere characteristics as predictive biomarkers of therapeutic response in triple-negative breast cancer

Abstract Background. Triple negative breast cancers (TNBC) represent about 15 % of invasive breast carcinomas. These tumors are identified in clinical practice according to their “triple negative” immunophenotype (estrogen receptor, progesterone receptor and HER2 negative). TNBC show aggressive behavior and an unusual sarcoma-like pattern of metastasis. Identification of predictive biomarkers is critical to optimal therapeutic management of these tumors. TNBC are characterized by increased genomic instability. These tumors present complex pattern of numerous low-amplitude genomic gains and losses as well as shorter telomeres. Aim. Identification of predictive biomarkers of response to neoadjuvant chemotherapy in TNBC by evaluating telomeric parameters and genomic instability. Methods. We studied 38 TNBC patients treated with neoadjuvant chemotherapy according to the TVA protocol (FEC 100, docetaxel, panitumumab). DNA and RNA were extracted from snap-frozen tumor samples obtained before neoadjuvant therapy. The pathological response to treatment was evaluated according to Chevallier's and Sataloff's classifications and correlated with aCGH profiles (8x60K, Agilent) and telomere characteristics, including telomere length (qPCR) and expression (qRT-PCR) of telomerase (hTERT) and shelterin complex genes (TRF1, TRF2, POT1, TPP1, RAP1 and TIN2). Results. Telomere shortening and high hTERT expression were found in more aggressive tumors according to TNM classification (P&amp;lt; 0.04), and hTERT expression was also highly correlated with an increased tumor size (P= 0.0058). Short telomeres were strongly associated with incomplete histological response to neoadjuvant therapy according to Chevallier's (P= 0.0004) and Sataloff's classifications, (P= 0.0007). hTERT expression was significantly increased in cases with incomplete response (P&amp;lt; 0.04). Among shelterin complex genes, TRF2 and TPP1 overexpression was found in more aggressive TNBC (according to TNM classification and SBR grading, P&amp;lt; 0.05), but there was no correlation with pathological response. aCGH data indicated that genomic instability in non-responders was mainly represented by genomic gains. In particular, cases with incomplete therapeutic responses showed significantly larger size of gains than cases with complete responses. (P= 0.0089). Short telomeres were also associated with larger gains of genomic material (P= 0.0067). Of note, telomere shortening has been previously described as one of the mechanisms of genomic gains and amplifications. Conclusions. Telomere shortening and hTERT overexpression were observed in resistant TNBC. Genomic profile of non-responding tumors was characterized by larger genomic gains. Telomere length, hTERT expression and genomic instability profiles may represent predictive biomarkers of response to neoadjuvant chemotherapy in TNBC. Citation Format: Mathilde Gay-bellile, Nina Radosevic-Robin, Eleonore Eymard-Pierre, Fabrice Kwiatkowski, Marie-Mélanie Dauplat, Maud Privat, Catherine Abrial, Patricia Combes, Gwendoline Soler, Yves-Jean Bignon, Jean-Marc Nabholtz, Philippe Vago, Frédérique Penault-Llorca, Andreï Tchirkov. Genomic instability and telomere characteristics as predictive biomarkers of therapeutic response in triple-negative breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 550. doi:10.1158/1538-7445.AM2014-550

Telomere Length and Telomerase Complex Mutations in Pediatric Acute Myeloid Leukemia

AbstractAbstract 1482Inherited loss-of-function mutations in the telomerase complex gene TERT have recently been implicated as risk factors for acute myeloid leukemia (AML) in adults. The telomerase complex is expressed in highly proliferative cells, and is responsible for maintaining telomeres, which cap the ends of chromosomes and protect genomic DNA from eroding during cell division. Impaired telomerase function can result in extremely short telomeres, which limits the proliferative capacity of progenitor cells, and can also lead to chromosomal instability, thus predisposing to malignant transformation. In pediatric AML, the frequency of such mutations, and the association of telomere length with cytogenetic, molecular, and clinical characteristics and outcome, are unknown.In a cohort of 168 pediatric AML patients, we determined the frequency of telomerase complex gene mutations and leukemic cell telomere length, and correlated this with prognostic cytogenetic characteristics (inv(16), t(8;21), MLL rearrangements, normal karyotype, other aberrations), molecular aberrations (CEBPA double mutations, NPM1 mutations, FLT3/ITD, WT1 mutations), clinical characteristics, and outcome.No mutations were present in TERC. Three heterozygous variants in TERT, E327D, T726M, and A1062T, were identified in eight of 168 pediatric AML patients (carrier frequency 0.048). In three of six patients carrying A1062T, remission material was available, in which germ-line origin of the variant was confirmed. The variants E327D and T726M were absent, but A1062T was present in a cohort of 406 geographically matched controls (carrier frequency 0.049). Telomerase activity, as determined by TRAP assay in reconstitution experiments, of the novel E327D variant was unaffected, as was the previously published activity of T726M; the earlier reported activity of A1062T was reduced to 60%.Telomere length of leukemic cells was not associated with age, sex, prognostic cytogenetic subgroup, complex karyotype, or expression levels of telomerase and shelterin complex genes. However, patients carrying the high-risk molecular aberration FLT3/ITD had significantly shorter telomeres than did patients with favorable NPM1 mutation or CEBPA double mutations. Telomere length was not associated with overall survival, event-free survival, or cumulative incidence of relapse.We conclude that, in pediatric AML, telomerase complex mutations do not confer a risk for leukemia development, and although short telomeres correlate with the high-risk molecular aberration FLT3/ITD, telomere length of leukemic cells obtained at diagnosis does not correlate with adverse outcome in this pediatric AML cohort. Disclosures:No relevant conflicts of interest to declare.