Telomere Length-Associated Genetic Variants and the Risk of Thyroid Cancer in Survivors of Childhood Cancer: A Report from the Childhood Cancer Survivor Study (CCSS)

Genetic Risk of Second Malignant Neoplasm after Childhood Cancer Treatment: A Systematic Review

Second malignant neoplasm (SMN) is one of the most severe long-term risks for childhood cancer survivors (CCS), significantly impacting long-term patient survival. While radiotherapy and chemotherapy are known risk factors, the observed inter-individual variability suggests a genetic component contributing to the risk of SMN. This article aims to conduct a systematic review of genetic factors implicated in the SMN risk among CCS. Searches were performed in PubMed, Scopus, and Web of Sciences. Eighteen studies were included (eleven candidate gene studies, three genome-wide association studies, and four whole exome/genome sequencing studies). The included studies were based on different types of first cancers, investigated any or specific types of SMN, and focused mainly on genes involved in drug metabolism and DNA repair pathways. These differences in study design and methods used to characterize genetic variants limit the scope of the results and highlight the need for further extensive and standardized investigations. However, this review provides a valuable compilation of SMN risk-associated variants and genes, facilitating efficient replication and advancing our understanding of the genetic basis for this major risk for CCS.

Exploring the Susceptibility to Multiple Primary Tumors in Patients with Differentiated Thyroid Cancer

PURPOSE

It was demonstrated that differentiated thyroid cancer (DTC) patients may develop multiple primary tumors (MPT) during follow-up. Many studies showed an association between reduced telomere length and cancer phenotype; in particular, the short telomeres were associated with the development of a primary tumor. However, the role of altered telomere length in MPT development has not yet been demonstrated. The aim of this study was to evaluate the possible correlation between a short telomere length in blood leukocytes and the risk of developing MPT in DTC patients.

PATIENTS AND METHODS

We retrospectively evaluated 167 DTC patients followed up for a median of 13.6 years. Our control group was represented by 105 healthy subjects without any thyroid disease or present or past history of tumors. Our study groups, age-matched, were evaluated for the relative telomere length measured in leukocytes of peripheral venous blood.

RESULTS

The relative telomere length (RTL) was significantly different in healthy subjects compared to the total group of differentiated thyroid cancer patients [p < 0.0001]. Shorter telomeres length was observed in DTC patients with (n = 32) and without (n = 135) MPT compared to healthy subjects (p < 0.0001 and p = 0.0002, respectively). At multivariate analysis, the parameters independently associated with the presence of MPT were RTL [OR: 0.466 (0.226-0.817), p = 0.018] and the familial DTC [OR: 2.949 (1.142-8.466), p = 0.032].

CONCLUSIONS

The results of this study suggest a role of the relative telomere length in predicting MPT development in DTC patients. Our results contribute to increasing the knowledge of the genetic mechanisms underlying MPT development in DTC patients, considering relative telomere length as a possible prognostic marker.

Burden of Morbidity and Mortality in Adolescent and Young Adult Cancer Survivors

There are an estimated 650,00 survivors of adolescent and young adult (AYA) cancers in the United States, a number that is expected to markedly increase in the coming decades. The recognition of the potential for some cancer treatments to affect the health of patients for many years after the initial diagnosis has prompted investigators to examine the evolving burden of late morbidity and mortality in AYAs with cancer after treatment completion. Studies in large international cohorts of AYA cancer survivors have now shown that the burden of late effects in survivors treated during the past four decades is substantial, affecting the health and well-being of the survivor, health systems' preparedness to meet their health care needs in the future, and societal economic costs that are largely affected by loss of productivity. We highlight the unique considerations for AYA cancer survivors, identify gaps in knowledge for future research, and provide an overview of emerging efforts to mitigate late effects in these survivors. Ongoing multidisciplinary bench-to-bedside collaborations are critical to understanding the biology of late effects in AYA cancer survivors and to developing personalized interventions to mitigate them. The growing population of AYA cancer survivors makes it imperative that these efforts extend across the cancer care continuum, which will allow survivors to ultimately live to their fullest potential.

Role of telomere length in human carcinogenesis (Review)

Cancer is considered the most important clinical, social and economic issue regarding cause‑specific disability‑adjusted life years among all human pathologies. Exogenous, endogenous and individual factors, including genetic predisposition, participate in cancer triggering. Telomeres are specific DNA structures positioned at the end of chromosomes and consist of repetitive nucleotide sequences, which, together with shelterin proteins, facilitate the maintenance of chromosome stability, while protecting them from genomic erosion. Even though the connection between telomere status and carcinogenesis has been identified, the absence of a universal or even a cancer‑specific trend renders consent even more complex. It is indicative that both short and long telomere lengths have been associated with a high risk of cancer incidence. When evaluating risk associations between cancer and telomere length, a disparity appears to emerge. Even though shorter telomeres have been adopted as a marker of poorer health status and an older biological age, longer telomeres due to increased cell growth potential are associated with the acquirement of cancer‑initiating somatic mutations. Therefore, the present review aimed to comprehensively present the multifaceted pattern of telomere length and cancer incidence association.

Short NK and naïve T-cell telomere length is associated with thyroid cancer in childhood cancer survivors: A report from the Childhood Cancer Survivor Study

BACKGROUND

Survivors of childhood cancer are at risk for therapy-related subsequent malignant neoplasms (SMN), including thyroid SMN. Telomere length (TL) is associated with cancer risk, but the relationship between TL and SMN risk among survivors is less clear.

METHODS

We conducted a nested, matched case-control study of radiation-exposed 15-year+ adult survivors of childhood cancer with thyroid SMN (cases) and without SMN (controls). 46 cases were matched to 46 controls by primary diagnosis, chemotherapy (yes/no), radiation field, and follow-up duration. Lymphocyte TL (LTL) was measured by telomere flow-FISH cytometry using blood samples banked at a mean of 38.9 years (cases), 39.2 years (controls). Genetic variation in telomere genes was assessed by whole genome sequencing. Point estimates for LTL <10th percentile were determined for cases and controls.

RESULTS

Cases had shorter median LTL than controls in three out of four leukocyte subsets. Cases were more likely to have NK cell LTL <10th percentile (p=0.01), and 2.8-fold more likely to have naïve T-cell LTL <10th percentile than controls (CI 1.07, 8.78). Five out of 15 cases with a rare indel or missense variant had naïve T-cell LTL <10th percentile, compared with one out of 8 controls.

CONCLUSIONS

Long-term survivors have shorter than expected LTL, a finding that is more pronounced among survivors with thyroid SMN.

IMPACT

The long-term impact of childhood cancer treatment on immune function is poorly understood. Our findings support immune function studies in larger survivor cohorts to assess long-term deficits in adaptive and innate immunity that may underlie SMN risk.

Prognostic value of leukocyte telomere length in renal cell carcinoma patients

Telomeres play important roles in cancer initiation and progression. Leukocyte telomere length (LTL) can modulate cancer risk and outcome. We hypothesize that genetically predicted short LTL is associated with worse prognosis in renal cell carcinoma (RCC). A total of 1,086 histologically confirmed RCC patients were included in this study. A weighted genetic risk score (GRS) predictive of LTL was constructed using 10 confirmed LTL-associated single nucleotide polymorphisms (SNPs). The associations of individual SNPs and GRS with recurrence and survival were determined by multivariate Cox proportional hazards analysis. In individual SNP analysis, long LTL-associated allele of rs7675998 in NAF1 gene at chromosome 4 was significantly associated with a reduced risk of recurrence (HR=0.85, 95% CI, 0.73-0.99, P=0.043), while the long LTL-associated allele of rs10936599 in TERC at chromosome 3 conferred a reduced risk of death (HR=0.85, 95% CI, 0.73-1.00, P=0.047). More importantly, genetically predicted LTL was associated with both recurrence and survival. Dichotomized at the median value of GRS, patients with low GRS (indicating short LTL) exhibited significantly increased risks of recurrence (HR=1.26, 95% CI, 1.03-1.54, P=0.025) and death (HR=1.23, 95% CI, 1.00-1.50, P=0.045). Hence, we concluded that genetically predicted short LTL is associated with worse prognosis in RCC patients.

Genetic variation in POT1 and risk of thyroid subsequent malignant neoplasm: A report from the Childhood Cancer Survivor Study

BACKGROUND

Telomere length is associated with risk for thyroid subsequent malignant neoplasm in survivors of childhood cancer. Here, we investigated associations between thyroid subsequent malignant neoplasm and inherited variation in telomere maintenance genes.

METHODS

We used RegulomeDB to annotate the functional impact of variants mapping to 14 telomere maintenance genes among 5,066 five-or-more year survivors who participate in the Childhood Cancer Survivor Study (CCSS) and who are longitudinally followed for incidence of subsequent cancers. Hazard ratios for thyroid subsequent malignant neoplasm were calculated for 60 putatively functional variants with minor allele frequency ≥1% in or near telomere maintenance genes. Functional impact was further assessed by measuring telomere length in leukocyte subsets.

RESULTS

The minor allele at Protection of Telomeres-1 (POT1) rs58722976 was associated with increased risk for thyroid subsequent malignant neoplasm (adjusted HR = 6.1, 95% CI: 2.4, 15.5, P = 0.0001; Fisher's exact P = 0.001). This imputed SNP was present in three out of 110 survivors who developed thyroid cancer vs. 14 out of 4,956 survivors who did not develop thyroid cancer. In a subset of 83 survivors with leukocyte telomere length data available, this variant was associated with longer telomeres in B lymphocytes (P = 0.004).

CONCLUSIONS

Using a functional variant approach, we identified and confirmed an association between a low frequency intronic regulatory POT1 variant and thyroid subsequent malignant neoplasm in survivors of childhood cancer. These results suggest that intronic variation in POT1 may affect key protein binding interactions that impact telomere maintenance and genomic integrity.

Shortened Leukocyte Telomere Length Associates with an Increased Prevalence of Chronic Health Conditions among Survivors of Childhood Cancer: A Report from the St. Jude Lifetime Cohort

PURPOSE

We aimed to analyze and compare leukocyte telomere length (LTL) and age-dependent LTL attrition between childhood cancer survivors and noncancer controls, and to evaluate the associations of LTL with treatment exposures, chronic health conditions (CHC), and health behaviors among survivors.

EXPERIMENTAL DESIGN

We included 2,427 survivors and 293 noncancer controls of European ancestry, drawn from the participants in St. Jude Lifetime Cohort Study (SJLIFE), a retrospective hospital-based study with prospective follow-up (2007-2016). Common nonneoplastic CHCs (59 types) and subsequent malignant neoplasms (5 types) were clinically assessed. LTL was measured with whole-genome sequencing data.

RESULTS

After adjusting for age at DNA sampling, gender, genetic risk score based on 9 SNPs known to be associated with telomere length, and eigenvectors, LTL among survivors was significantly shorter both overall [adjusted mean (AM) = 6.20 kb; SE = 0.03 kb] and across diagnoses than controls (AM = 6.69 kb; SE = 0.07 kb). Among survivors, specific treatment exposures associated with shorter LTL included chest or abdominal irradiation, glucocorticoid, and vincristine chemotherapies. Significant negative associations of LTL with 14 different CHCs, and a positive association with subsequent thyroid cancer occurring out of irradiation field were identified. Health behaviors were significantly associated with LTL among survivors aged 18 to 35 years (P _trend = 0.03).

CONCLUSIONS

LTL is significantly shorter among childhood cancer survivors than noncancer controls, and is associated with CHCs and health behaviors, suggesting LTL as an aging biomarker may be a potential mechanistic target for future intervention studies designed to prevent or delay onset of CHCs in childhood cancer survivors.See related commentary by Walsh, p. 2281.