Short telomeres are frequent in hereditary breast tumors and are associated with high tumor grade

Genetic and epigenetic alterations in night shift nurses with breast cancer: a narrative review

This narrative review explores the link between breast cancer and night shift work in nurses, focusing on genetic and epigenetic factors. Breast cancer disproportionately affects women globally, and night shift work is increasingly recognized as a potential risk factor. Nurses who work consecutive overnight shifts face elevated risks due to disruptions in their circadian rhythms. Studies suggest that working six or more successive night shifts, particularly over five years or more, may increase breast cancer risk. This review hypothesizes that disruptions in the sleep-wake cycle, such as changes in melatonin production and telomere length, could contribute to breast cancer susceptibility. Currently, there is limited genetic evidence to support this hypothesis. However, it is plausible that genetic and epigenetic alterations, including changes in genes like ER and HER2, may heighten the risk for night shift nurses. These alterations may involve variations in telomere length, DNA methylation, and disruptions in critical breast cancer-related genes. We highlight various genetic and epigenetic changes that may influence this increased susceptibility. Further research is needed to explore the underlying mechanisms and contributing factors in this association.

The dynamics of telomere length in primary and metastatic colorectal cancer lesions

Telomeric sequences, the structures comprised of hexanucleotide repeats and associated proteins, play a pivotal role in chromosome end protection and preservation of genomic stability. Herein we address telomere length (TL) dynamics in primary colorectal cancer (CRC) tumour tissues and corresponding liver metastases. TL was measured by multiplex monochrome real-time qPCR in paired samples of primary tumours and liver metastases along with non-cancerous reference tissues obtained from 51 patients diagnosed with metastatic CRC. Telomere shortening was observed in the majority of primary tumour tissues compared to non-cancerous mucosa (84.1%, p < 0.0001). Tumours located within the proximal colon had shorter TL than those in the rectum (p < 0.05). TL in liver metastases was not significantly different from that in primary tumours (p = 0.41). TL in metastatic tissue was shorter in the patients diagnosed with metachronous liver metastases than in those diagnosed with synchronous liver metastases (p = 0.03). The metastatic liver lesions size correlated with the TL in metastases (p < 0.05). Following the neoadjuvant treatment, the patients with rectal cancer had shortened telomeres in tumour tissue than prior to the therapy (p = 0.01). Patients with a TL ratio between tumour tissue and the adjacent non-cancerous mucosa of ≥ 0.387 were associated with increased overall survival (p = 0.01). This study provides insights into TL dynamics during progression of the disease. The results show TL differences in metastatic lesions and may help in clinical practice to predict the patient's prognosis.

Impact of DAXX and ATRX expression on telomere length and prognosis of breast cancer patients

BACKGROUND

Telomere stability is one of the hallmarks of cancer that promotes cellular longevity, the accumulation of genetic alterations, and tumorigenesis. The loss of death domain-associated protein (DAXX) and α-thalassemia/mental retardation X-linked protein (ATRX) plays a role in telomere lengthening and stability. This study aims to evaluate the prognostic significance of telomere length (TL) and its association with DAXX and ATRX proteins in breast cancer (BC). Our study used the FISH technique to detect peptide nucleic acid (PNA) in the peripheral blood cells of a cohort of BC patients (n = 220) and a control group of apparently healthy individuals (n = 100). Expression of DAXX and ATRX proteins was evaluated using immunohistochemistry (IHC) in all BC tissues.

RESULTS

Patients with a shorter TL had worse disease-free survival (DFS) and overall survival (OS). There were significant associations between shorter TL and advanced disease stages, lymph node metastasis, and positive HER2/neu expression. DAXX protein expression was significantly correlated with TL. Lower DAXX expression was significantly with shorter DFS.

CONCLUSION

Assessing TL can be used as a worthy prognostic indicator in BC patients. Specifically, short TL had a poor impact on the prognosis of BC patients. Low DAXX expression is associated with poor outcomes in BC. Further mechanistic studies are warranted to reveal the underlying mechanisms of these associations.

Next-Generation Sequencing Identifies BRCA1 and/or BRCA2 Mutations in Women at High Hereditary Risk for Breast Cancer with Shorter Telomere Length

Telomeres, and telomere length in particular, have broad significance for genome biology and thus are prime research targets for complex diseases such as cancers. In this context, BRCA1 and BRCA2 gene mutations have been implicated in relationship to telomere length, and breast cancer susceptibility. Yet, the linkages among human genetic variation and telomere length in persons with high hereditary cancer risk are inadequately mapped. We report here original findings in 113 unrelated women at high hereditary risk for breast cancer, who were characterized for the BRCA1 and BRCA2 mutations using next-generation sequencing. Thirty-one BRCA2 and 21 BRCA1 mutations were identified in 47 subjects (41.6%). The women with a mutation in BRCA1 and/or BRCA2 genes had, on average, 12% shorter telomere compared to women with no BRCA1 or BRCA2 mutation (p = 0.0139). Moreover, the association between telomere length and BRCA mutation status held up upon stratified analysis in those with or without a breast cancer diagnosis. We also indentified two rare mutations, c.536_537insT and c.10078A>G, and a novel mutation c.8680C>G in BRCA2 that was studied further by homology modeling of the DNA binding tower domain of BRCA2 and the structure of the protein. These data collectively lend evidence to the idea that BRCA1 and BRCA2 mutations play a role in telomere length in women at high hereditary risk for breast cancer. Further clinical and diagnostics discovery research on BRCA1 and BRCA2 variation, telomere length, and breast cancer mechanistic linkages are called for in larger study samples.

Night Shift Work, DNA Methylation and Telomere Length: An Investigation on Hospital Female Nurses

Increased breast cancer risk has been reported in some night shift (NS) workers but underlying biological mechanisms are still unclear. We assessed the association between NS work and DNA methylation of tumor suppressor (TP53, CDKN2A, BRCA1, BRCA2) and estrogen receptor (ESR1, ESR2) genes, methylation of repetitive elements (LINE-1, Alu), and telomere length (TL). Forty six female nurses employed in NS for at least two years were matched by age (30–45 years) and length of service (≥1 year) with 51 female colleagues not working in NS. Each subject underwent a semi-structured interview and gave a blood sample. We applied linear regression and spline models adjusted for age, BMI, smoking habit, oral contraceptive use, parity and marital status/age at marriage. Currently working in NS was associated with ESR1 hypomethylation (β: −1.85 (95%CI: −3.03; −0.67), p = 0.003). In current and former NS workers we observed TP53 (−0.93 (−1.73; −0.12), p = 0.03) and BRCA1 (−1.14 (−1.71; −0.58), p <0.001) hypomethylation. We found an increase between TL and number of years in NS in subjects employed in NS <12 years (0.06 (0.03; 0.09), p <0.001), while a decrease if employed in NS ≥12 years (−0.07 −0.10; −0.04), p <0.001). Our findings show NS-associated markers potentially involved in cellular aging, genomic instability, and cancer development.

Genetic analyses of aplastic anemia and idiopathic pulmonary fibrosis patients with short telomeres, possible implication of DNA-repair genes

Background

Telomeres are nucleoprotein structures present at the terminal region of the chromosomes. Mutations in genes coding for proteins involved in telomere maintenance are causative of a number of disorders known as telomeropathies. The genetic origin of these diseases is heterogeneous and has not been determined for a significant proportion of patients.

Methods

This article describes the genetic characterization of a cohort of patients. Telomere length was determined by Southern blot and quantitative PCR. Nucleotide variants were analyzed either by high-resolution melting analysis and Sanger sequencing of selected exons or by massive sequencing of a panel of genes.

Results

Forty-seven patients with telomere length below the 10% of normal population, affected with three telomeropathies: dyskeratosis congenita (4), aplastic anemia (22) or pulmonary fibrosis (21) were analyzed. Eighteen of these patients presented known pathogenic or novel possibly pathogenic variants in the telomere-related genes TERT, TERC, RTEL1, CTC1 and ACD. In addition, the analyses of a panel of 188 genes related to haematological disorders indicated that a relevant proportion of the patients (up to 35%) presented rare variants in genes related to DNA repair or in genes coding for proteins involved in the resolution of complex DNA structures, that participate in telomere replication. Mutations in some of these genes are causative of several syndromes previously associated to telomere shortening.

Conclusion

Novel variants in telomere, DNA repair and replication genes are described that might indicate the contribution of variants in these genes to the development of telomeropathies. Patients carrying variants in telomere-related genes presented worse evolution after diagnosis than the rest of patients analyzed.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1046-0) contains supplementary material, which is available to authorized users.

Leucocytes telomere length and breast cancer risk/ susceptibility: A case-control study

BACKGROUND

Telomere length in peripheral blood leukocytes (PBL-TL) was proposed as a biomarker of cancer risk. Recent scientific evidence suggested PBL-TL plays a diverse role in different cancers. Inconsistent results were obtained on PBL-TL in relation to breast cancer risk and specifically to the presence of BRCA1 and BRCA2 mutations. The aim of the present case-control study was to analyse the correlation between family history of breast cancer or presence of a BRCA mutation and PBL-TL in the hypothesis that TL is a modifier of cancer risk.

METHODS

PBL-TL was measured using the real-time quantitative PCR method in DNA for 142 cases and 239 controls. All the women enrolled were characterized for cancer family history. A subgroup of 48 women were classified for the presence of a BRCA mutation. PBL-TL were summarized as means and standard deviations, and compared by standard analysis of variance. A multivariable Generalised Linear Model was fitted to the data with PBL-TL as the dependent variable, case/control status and presence of a BRCA/VUS mutation as factors, and age in 4 strata as a covariate.

RESULTS

Age was significantly associated with decreasing PBL-TL in controls (p = 0.01), but not in BC cases. The telomere length is shorter in cases than in controls after adjusting for age. No effect on PBL-TL of BMI, smoke nor of the most common risk factors for breast cancer was observed. No association between PBL-TL and family history was detected both in BC cases and controls. In the multivariate model, no association was observed between BRCA mutation and decreased PBL-TL. A statistically significant interaction (p = 0.031) between case-control status and a BRCA-mutation/VUS was observed, but no effect was detected for the interaction of cancer status and BRCA or VUS.

CONCLUSION

Our study fails to provide support to the hypothesis that PBL-TL is associated with the risk of hereditary BC, or that is a marker of inherited mutations in BRCA genes.

The childhood maltreatment influences on breast cancer patients: A second wave hit model hypothesis for distinct biological and behavioral response

Stress and cancer are two complex situations involving different biological and psychological mechanisms. Their relationship have long been studied, and there is evidence of the impact stress has on both, development and disease progression. Furthermore, early stress has been studied as an important factor associated to this relationship, since its impacts on the immune, endocrine and cognitive development throughout life is already known. Therefore, understanding early stress as a first wave of stress in life is necessary in order to explore a possible second wave hit model. From this perspective, we believe that breast cancer can be understood as a second wave of stress during development and that, in addition to the first wave, can cause important impacts on the response to cancer treatment, such as increased chances of disease progression and distinct behavioral responses. In this article we propose a second wave hit hypothesis applied to breast cancer and its implications on the immune, endocrine and cognitive systems, through mechanisms that involve the HPA axis and subsequent activations of stress responses.

Mechanisms of breast cancer risk in shift workers: association of telomere shortening with the duration and intensity of night work

Occupational factors such as shiftwork and especially night work that involves disruption of the circadian rhythm may contribute to increased breast cancer risk. Circadian disruption may also affect telomere length (TL). While short TL generally is associated with increased cancer risk, its association with breast cancer risk is inconclusive. We suggest that working schedules might be an important factor in assessment of effects of TL on breast cancer risk. Moreover, telomere shortening might be a potential mechanism for night work‐related breast cancer. In this study, effects of shift work on TL and its association with breast cancer risk were investigated in a nested breast cancer case–control study of Norwegian nurses. TL was assessed by qPCR in DNA from 563 breast cancer patients and 619 controls. Here, we demonstrate that TL is affected by intensive night work schedules, as work with six consecutive night for a period of more than 5 years was associated with decreased telomere lengths (−3.18, 95% CI: −6.46 to −0.58, P = 0.016). Furthermore, telomere shortening is associated with increased breast cancer risk in workers with long periods of consecutive night shifts. Thus, nurses with longer telomere lengths had a lower risk for breast cancer if they had worked more than four (OR: 0.37, 95% CI: 0.16–0.79, P = 0.014) or five (OR: 0.31, 95% CI: 0.10–0.83, P = 0.029) consecutive night shifts for a period of 5 years or more. These data suggest that telomere shortening is associated with the duration and intensity of night work and may be a contributing factor for breast cancer risk among female shift workers.

Comparison of telomere length and insulin-like growth factor-binding protein 7 promoter methylation between breast cancer tissues and adjacent normal tissues in Turkish women

BACKGROUND

Both insulin-like growth factor-binding protein 7 (IGFBP7) and telomere length (TL) are associated with proliferation and senescence of human breast cancer. This study assessed the clinical significance of both TL and IGFBP7 methylation status in breast cancer tissues compared with adjacent normal tissues. We also investigated whether IGFBP7 methylation status could be affecting TL.

METHODS

Telomere length was measured by quantitative PCR to compare tumors with their adjacent normal tissues. The IGFBP7 promoter methylation status was evaluated by methylation-specific PCR and its expression levels were determined by western blotting.

RESULTS

Telomeres were shorter in tumor tissues compared to controls (P<.0001). The mean TL was higher in breast cancer with invasive ductal carcinoma (IDC; n=72; P=.014) compared with other histological type (n=29), and TL in IDC with HER2 negative (n=53; P=.017) was higher than TL in IDC with HER2 positive (n=19). However, telomeres were shortened in advanced stages and growing tumors. IGFBP7 methylation was observed in 90% of tumor tissues and 59% of controls (P=.0002). Its frequency was significantly higher in IDC compared with invasive mixed carcinoma (IMC; P=.002) and it was not correlated either with protein expression or the other clinicopathological parameters.

CONCLUSION

These results suggest that IGFBP7 promoter methylation and shorter TL in tumor compared with adjacent tissues may be predictive biomarkers for breast cancer. Telomere maintenance may be indicative of IDC and IDC with HER2 (-) of breast cancer. Further studies with larger number of cases are necessary to verify this association.

Telomere Length and Breast Cancer Prognosis: A Systematic Review

Telomeres ensure genome integrity during replication. Loss of telomeric function leads to cell immortalization and accumulation of genetic alterations. The association of telomere length (TL) with breast cancer prognosis is examined through a systematic review. Electronic databases (MEDLINE, EMBASE, CENTRAL), from inception to December 2015, and relevant reviews were searched. Studies that evaluated TL (blood and/or tumor) in association with breast cancer survival or prognostic factor were included. Thirty-six studies met inclusion criteria. Overall risk of bias was critical. Eight studies reported survival outcomes. Overall, there was a trend toward an association of longer telomeres with better outcomes (tumor, not blood). Of the 33 studies reporting associations with prognostic factors, nine adjusted for potential confounders. Among the latter, shorter telomeres were associated with older age (blood, not tumor), higher local recurrence rates (normal tissue), higher tumor grade (tumor), and lower physical activity (blood), which were reported in one study each. TL was not associated with molecular subtype (blood, one study), family history (tumor, one study), chemotherapy (blood, three of four studies), and stress reduction interventions (blood, two of two studies). Although major methodologic differences preclude from drawing conclusive results, TL could be a valuable breast cancer prognostic marker. Cancer Epidemiol Biomarkers Prev; 26(1); 3-10. ©2016 AACR.

ERCC1 and telomere status in breast tumours treated with neoadjuvant chemotherapy and their association with patient prognosis

Dysfunctional telomeres and DNA damage repair (DDR) play important roles in cancer progression. Studies have reported correlations between these factors and tumour aggressiveness and clinical outcome in breast cancer. We studied the characteristics of telomeres and expression of ERCC1, a protein involved in a number of DNA repair pathways and in telomere homeostasis, to assess their prognostic value, alone or in combination, in 90 residual breast tumours after treatment with neoadjuvant chemotherapy (NCT). ERCC1 status was investigated at different molecular levels (protein and gene expression and gene copy‐number variations) by immunohistochemistry, qRT‐PCR and quantitative multiplex fluorescent‐PCR (QMF‐PCR). A comprehensive analysis of telomere characteristics was performed using qPCR for telomere length and qRT‐PCR for telomerase (hTERT), tankyrase 1 (TNKS) and shelterin complex (TRF1, TRF2, POT1, TPP1, RAP1 and TIN2) gene expression. Short telomeres, high hTERT and TNKS expression and low ERCC1 protein expression were independently associated with worse survival outcome. Interestingly, ERCC1 gains and losses correlated with worse disease‐free (p = 0.026) and overall (p = 0.043) survival as compared to survival of patients with normal gene copy‐numbers. Unsupervised hierarchical clustering of all ERCC1 and telomere parameters identified four subgroups with distinct prognosis. In particular, a cluster combining low ERCC1, ERCC1 gene alterations, dysfunctional telomeres and high hTERT and a cluster with high TNKS and shelterin expression correlated with poor disease‐free (HR= 5.41, p= 0.0044) and overall survival (HR= 6.01, p= 0.0023) irrespective of tumour stage and grade. This comprehensive study demonstrates that telomere dysfunction and DDR can contribute synergistically to tumour progression and chemoresistance. These parameters are predictors of clinical outcome in breast cancer patients treated with NCT and could be useful clinically as prognostic biomarkers to tailor adjuvant chemotherapy post‐NCT.

Prenatal stress and newborn telomere length

BACKGROUND

The developmental origin of the health and disease hypothesis is based on the premise that many chronic diseases have their roots in fetal development. Specifically, maternal stress during pregnancy is associated with altered fetal development and many adverse long-term health outcomes. Although the mechanisms underlying this effect are currently unclear, at the cellular level 1 possible mediator is the regulation of telomere length. Telomere dynamics appear to play a role in disease progression, and an adverse intrauterine environment may contribute in the establishment of short telomeres in newborns. In accordance with this, it was recently reported that prenatal stress is significantly associated with shorter mean newborn telomere length. However, this finding has yet to be replicated, and currently we know nothing about whether different size classes of telomeres within the telomere length distribution are differentially affected by prenatal stress. Examining telomere length frequency distributions is important, because the shortest telomeres in the distribution appear to be the most indicative of telomere dysfunction and thus the best predictors of mortality and morbidity in humans.

OBJECTIVE

We investigated the effects of intrauterine exposure to maternal stress over the whole course of gestation on newborn mean telomere length and telomere length frequency distributions.

STUDY DESIGN

We conducted a prospective cohort study of 24 mother-newborn dyads at an urban teaching hospital. Pregnant women with nonanomalous, uncomplicated pregnancies were recruited and assessed in the third trimester of gestation. Maternal psychosocial stress was quantified using the Holmes and Rahe Stress Scale and categorized as high stress (≥300 points) or low stress (≤299 points) exposure. Newborn telomere length was measured from cord blood at delivery using the Telomere Restriction Fragment assay.

RESULTS

We found a significant negative association between maternal stress and newborn telomere length (β = -0.463, P = 0.04). Newborns whose mothers experienced a high level of stress during pregnancy had significantly shorter telomere length (6.98 ± 0.41 kb) compared to newborns of mothers with low stress (8.74 ± 0.24 kb; t = -3.99, P = .003). Moreover, the difference in newborn telomere length between high-stress and low-stress mothers was due to a shift in the telomere length distribution, with the high-stress group showing an underrepresentation of longer telomeres and an over-representation of shorter telomeres.

CONCLUSION

Our findings replicate those of other recent studies and also show, for the first time, that the prenatal stress-associated difference in newborn mean telomere length is due to a shift in the overall telomere distribution.

Generation of mice with longer and better preserved telomeres in the absence of genetic manipulations

Although telomere length is genetically determined, mouse embryonic stem (ES) cells with telomeres of twice the normal size have been generated. Here, we use such ES cells with ‘hyper-long' telomeres, which also express green fluorescent protein (GFP), to generate chimaeric mice containing cells with both hyper-long and normal telomeres. We show that chimaeric mice contain GFP-positive cells in all mouse tissues, display normal tissue histology and normal survival. Both hyper-long and normal telomeres shorten with age, but GFP-positive cells retain longer telomeres as mice age. Chimaeric mice with hyper-long telomeres also accumulate fewer cells with short telomeres and less DNA damage with age, and express lower levels of p53. In highly renewing compartments, such as the blood, cells with hyper-long telomeres are longitudinally maintained or enriched with age. We further show that wound-healing rates in the skin are increased in chimaeric mice. Our work demonstrates that mice with functional, longer and better preserved telomeres can be generated without the need for genetic manipulations, such as TERT overexpression.

Telomere shortening has been linked to some aspects of organismal ageing. Here the authors create chimaeric mice that contain a mix of cells with normal or unnaturally long telomeres, and show chimaeric mice are protected from some forms of ageing-associated cellular damage and have accelerated wound-healing.

Association between telomere length and survival in cancer patients: a meta-analysis and review of literature

The relationship between telomere length and cancer survival has been widely studied. To gain a deeper insight, we reviewed the published studies. A total of 29 studies evaluated telomere length in the peripheral blood; 22 studies evaluated telomere length in the tumor tissue. First, in the peripheral blood studies, for solid tumor patients with shortened telomere length, the combined hazard ratios (HRs) for mortality and tumor progression were 1.21 (95%CI, 1.10-1.32) and 1.71 (95%CI, 1.37-2.13), respectively. Meanwhile, in hematology malignancy, the combined HRs for mortality and tumor progression were 2.83 (95%CI, 2.14-3.74) and 2.65 (95%CI, 2.18-3.22), respectively. Second, in the studies that use tumor tissue, for patients with shortened telomeres, the combined HRs for mortality and tumor progression were 1.26 (95%CI, 0.95-1.66) and 1.65 (95%CI, 1.26-2.15), respectively. In the studies that calculate the telomere length ratios of tumor tissue to adjacent normal mucosa, for patients with lower telomere length ratios, the combined HRs were 0.66 (95%CI, 0.53-0.83) and 0.74 (95%CI, 0.41-1.32) for mortality and tumor progression, respectively. In conclusion, shortened telomere in peripheral blood and tumor tissue might indicate poor survival for cancer patients. However, by calculating the telomere length ratios of tumor tissue to adjacent normal mucosa, the lower ratio might indicate better survival.

Shorter telomeres and high telomerase activity correlate with a highly aggressive phenotype in breast cancer cell lines

Maintenance of telomere length is one function of human telomerase that is crucial for the survival of cancer cells and cancer progression. Both telomeres and telomerase have been proposed as possible biomarkers of cancer risk and cancer invasiveness; however, their clinical relevance is still under discussion. In order to improve our understanding of the relationship between telomere length and telomerase activity with cancer invasiveness, we studied telomere length as well as telomerase levels, activity, and intracellular localization in breast cancer cell lines with diverse invasive phenotypes. We found an apparently paradoxical coincidence of short telomeres and enhanced telomerase activity in the most invasive breast cancer cell lines. We also observed that hTERT intracellular localization could be correlated with its level of activity. There was no association between human telomerase reverse transcriptase (hTERT) protein expression levels and invasiveness. We propose that simultaneous evaluation of these two biomarkers-telomere length and telomerase activity-could be useful for the assessment of the invasive capacity and aggressiveness of tumor cells from breast cancer patients.

BRCA1/2 mutations perturb telomere biology: characterization of structural and functional abnormalities in vitro and in vivo

BRCA1 mutation is associated with carcinogenesis, especially of breast tissue. Telomere maintenance is crucial for malignant transformation. Being a part of the DNA repair machinery, BRCA1 may be implicated in telomere biology. We explored the role of BRCA1 in telomere maintenance in lymphocytes of BRCA1/2 mutation carriers and in in vitro system by knocking down its expression in non-malignant breast epithelial cells.The results in both systems were similar. BRCA1/2 mutation caused perturbation of telomere homeostasis, shortening of the single stranded telomere overhang and increased the intercellular telomere length variability as well as the number of telomere free chromosomal ends and telomeric circles. These changes resulted in an increased DNA damage status. Telomerase activity, inducibility and expression remained unchanged. BRCA1 mutation resulted also in changes in the binding of shelterin proteins to telomeres. DNMT-1 levels were markedly reduced both in the carriers and in in vitro system. The methylation pattern of the sub-telomeric regions in carriers suggested hypomethylation in chromosome 10. The expression of a distinct set of genes was also changed, some of which may relate to pre-disposition to malignancy.These results show that BRCA gene products have a role in telomere length homeostasis. It is plausible that these perturbations contribute to malignant transformation in BRCA mutants.

Poor prognosis of constitutive γ-H2AX expressing triple-negative breast cancers is associated with telomere length

AIM

Here, we set out to establish whether endogenous γ-H2AX is a biomarker in triple-negative breast cancer.

METHODS

We explored the association of γ-H2AX with mutation status and sensitivity to 139 different anticancer drugs in up to 41 breast cancer cell lines. Further, we correlated γ-H2AX expression in breast cancer tumor tissues with telomere length.

RESULTS

γ-H2AX positive breast cancer cells exhibit more mutations, and - when p53 mutated - have shorter telomeres. In breast cancer patients γ-H2AX is also related to shorter telomeres, which was in turn associated with poorer prognosis of triple-negative breast cancer patients.

CONCLUSION

Thus, endogenous γ-H2AX is associated with short telomeres, which might offer a specific target for therapy for triple-negative breast cancer patients.

Telomere fusion threshold identifies a poor prognostic subset of breast cancer patients

Telomere dysfunction and fusion can drive genomic instability and clonal evolution in human tumours, including breast cancer. Telomere length is a critical determinant of telomere function and has been evaluated as a prognostic marker in several tumour types, but it has yet to be used in the clinical setting. Here we show that high‐resolution telomere length analysis, together with a specific telomere fusion threshold, is highly prognostic for overall survival in a cohort of patients diagnosed with invasive ductal carcinoma of the breast (n = 120). The telomere fusion threshold defined a small subset of patients with an extremely poor clinical outcome, with a median survival of less than 12 months (HR = 21.4 (7.9–57.6), P < 0.0001). Furthermore, this telomere length threshold was independent of ER, PGR, HER2 status, NPI, or grade and was the dominant variable in multivariate analysis. We conclude that the fusogenic telomere length threshold provides a powerful, independent prognostic marker with clinical utility in breast cancer. Larger prospective studies are now required to determine the optimal way to incorporate high‐resolution telomere length analysis into multivariate prognostic algorithms for patients diagnosed with breast cancer.

High‐resolution telomere length analysis is highly prognostic for overall survival.

Independent of ER, PGR, HER2 status, NPI and grade.

Dominant variable in multivariate analysis.

The presence of telomere fusion in sporadic colon cancer independently of disease stage, TP53/KRAS mutation status, mean telomere length, and telomerase activity

Defects in telomere maintenance can result in telomere fusions that likely play a causative role in carcinogenesis by promoting genomic instability. However, this proposition remains to be fully understood in human colon carcinogenesis. In the present study, the temporal sequence of telomere dysfunction dynamics was delineated by analyzing telomere fusion, telomere length, telomerase activity, hotspot mutations in KRAS or BRAF, and TP53 of tissue samples obtained from 18 colon cancer patients. Our results revealed that both the deficiency of p53 and the shortening of mean telomere length were not necessary for producing telomere fusions in colon tissue. In five cases, telomere fusion was observed even in tissue adjacent to cancerous lesions, suggesting that genomic instability is initiated in pathologically non-cancerous lesions. The extent of mean telomere attrition increased with lymph node invasiveness of tumors, implying that mean telomere shortening correlates with colon cancer progression. Telomerase activity was relatively higher in most cancer tissues containing mutation(s) in KRAS or BRAF and/or TP53 compared to those without these hotspot mutations, suggesting that telomerase could become fully active at the late stage of colon cancer development. Interestingly, the majority of telomere fusion junctions in colon cancer appeared to be a chromatid-type containing chromosome 7q or 12q. In sum, this meticulous correlative study not only highlights the concept that telomere fusion is present in the early stages of cancer regardless of TP53/KRAS mutation status, mean telomere length, and telomerase activity, but also provides additional insights targeting key telomere fusion junctions which may have significant implications for colon cancer diagnoses.