U-shaped association between telomere length and esophageal squamous cell carcinoma risk: a case-control study in Chinese population

Overview of Risk Factors for Esophageal Squamous Cell Carcinoma in China

(1) Background: China has the highest esophageal squamous cell carcinoma (ESCC) incidence areas in the world, with some areas of incidence over 100 per 100,000. Despite extensive public health efforts, its etiology is still poorly understood. This study aims to review and summarize past research into potential etiologic factors for ESCC in China. (2) Methods: Relevant observational and intervention studies were systematically extracted from four databases using key terms, reviewed using Rayyan software, and summarized into Excel tables. (3) Results: Among the 207 studies included in this review, 129 studies were focused on genetic etiologic factors, followed by 22 studies focused on dietary-related factors, 19 studies focused on HPV-related factors, and 37 studies focused on other factors. (4) Conclusions: ESCC in China involves a variety of factors including genetic variations, gene-environment interactions, dietary factors like alcohol, tobacco use, pickled vegetables, and salted meat, dietary behavior such as hot food/drink consumption, infections like HPV, poor oral health, gastric atrophy, and socioeconomic factors. Public health measures should prioritize genetic screening for relevant polymorphisms, conduct comprehensive investigations into environmental, dietary, and HPV influences, enhance oral health education, and consider socioeconomic factors overall as integral strategies to reduce ESCC in high-risk areas of China.

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.

Identification of Leukocyte telomere length-related genetic variants contributing to predisposition of Esophageal Squamous Cell Carcinoma

Background: Cancers may arise from cells with dysregulated telomeric functions due to shorten telomere length. We and others previously found that short leukocyte telomere length was associated with markedly evaluated risk of esophageal squamous cell carcinoma (ESCC). Hence, we hypothesized that single nucleotide polymorphisms (SNPs) associated with shorter telomere length may contribute to ESCC predisposition.

Methods: We systematically evaluated association between seven candidate seven SNPs (CXCR4 rs6430612, TERT rs13172201, TERT rs10069690, TERT rs2853676, TERT rs451360, OBFC1 rs4387287, and VPS34 rs2162440) and ESCC risk in two case-control sets consisting of 1588 ESCC cases and 1600 controls. Logistic regression models were utilized to estimate associations between SNPs and ESCC susceptibility and odds ratios (ORs) and their 95% confidence intervals (95% CIs) were computed.

Results: We firstly identified three SNPs (rs6430612, rs13172201 and rs4387287) which are significantly associated with telomere length in Chinese populations (all P<0.05). Importantly, CXCR4 rs6430612 and OBFC1 rs4387287 polymorphisms significantly confer reduced risk of ESCC (P=1.7×10^-7 and P=3.9×10^-5). On the contrary, we observed an evidently increased risk for ESCC development associated with TERT rs13172201 genetic variant (P=2.2×10^-4).

Conclusions: In summary, rs6430612, rs13172201 and rs4387287 might be key genetic components in complicated regulation of telomere length and contributing to ESCC predisposition. Our results elucidate the prevalent involvement of genetic variants in telomere biology and further provide pathogenic insights into the role of telomeres in cancer development.

Leukocyte Telomere Length and Risk of Papillary Thyroid Carcinoma

CONTEXT

Telomere length may contribute to predisposition to papillary thyroid cancer (PTC).

OBJECTIVE

To test this hypothesis, we examined the association between leukocyte telomere length and PTC risk.

DESIGN/SETTING

Case-control study in a Chinese Han population.

PARTICIPANTS/INTERVENTION

A total of 1200 PTC cases and 1201 age- and sex-matched healthy controls were included in the study. ORs and 95% CIs were calculated by logistic regression.

RESULTS

Short relative telomere length (RTL) was significantly associated with elevated risk of PTC (OR = 1.61, 95% CI = 1.35 to 1.92; P = 1.30 × 10-7). Interestingly, when individuals were categorized into four groups on the basis of quartile distribution of relative telomere length (RTL) in controls, we observed a reverse U-shaped association between telomere length and PTC risk. Compared with those in the first (the longest) quartile as the reference group, ORs (95% CIs) were 5.61 (4.04 to 7.78) (P = 6.10 × 10-25), 9.33 (6.78 to 12.83) (P = 6.99 × 10-43), and 1.23 (0.83 to 1.81) (P = 0.300) for individuals in the second, third, and fourth (the shortest) quartiles, respectively. This reverse U-shaped relationship was more apparent in younger individuals.

CONCLUSIONS

Our findings suggest that RTL is significantly associated with susceptibility to PTC. There is an obvious reverse U-shaped association between telomere length and PTC risk. Telomere length may be a potential pronouncing biomarker to identify individuals with a high risk of developing PTC.

Leukocyte telomere length associates with nasopharyngeal carcinoma risk and survival in Hong Kong Chinese

Telomere shortening occurs as an early event in tumorigenesis. The TERT-CLPTM1L locus associates with nasopharyngeal carcinoma (NPC) risk. It remains unknown if leukocyte telomere length (LTL) associates with NPC risk and survival. The relative LTL (rLTL) was measured by quantitative-PCR in 2,996 individuals comprised of 1,284 NPC cases and 1712 matched controls. The odds ratio (OR) and 95% confidence intervals (CI) were calculated by logistic regression. The hazard ratio (HR) and 95% CI were calculated by Cox regression for survival analysis with rLTL and other clinical parameters in 1,243 NPC with a minimum follow-up period of 25 months. NPC patients had significantly shorter telomere length than controls. Shorter rLTL significantly associated with increased NPC risk, when the individuals were dichotomized into long and short telomeres based on median-split rLTL in the control group (OR = 2.317; 95% CI = 1.989-2.700, p = 4.10 × 10^-27 ). We observed a significant dose-response association (p_trend  = 3.26 × 10^-34 ) between rLTL and NPC risk with OR being 3.555 (95% CI = 2.853-4.429) for the individuals in the first quartile (shortest) compared with normal individuals in the fourth quartile (longest). A multivariate Cox regression analysis adjusted by age demonstrated an independent effect of rLTL on NPC survival for late-stage NPC patients, when the individuals were categorized into suboptimal rLTL versus the medium rLTL based on a threshold set from normal (HR = 1.471, 95% CI = 1.056-2.048, p = 0.022). Shorter blood telomeres may be markers for higher susceptibility for NPC risk. Suboptimal rLTL may be a poor prognostic factor for advanced NPC patients, as it associates independently with poor survival.

Telomere Length Dynamics and the Evolution of Cancer Genome Architecture

Telomeres are progressively eroded during repeated rounds of cell division due to the end replication problem but also undergo additional more substantial stochastic shortening events. In most cases, shortened telomeres induce a cell-cycle arrest or trigger apoptosis, although for those cells that bypass such signals during tumour progression, a critical length threshold is reached at which telomere dysfunction may ensue. Dysfunction of the telomere nucleoprotein complex can expose free chromosome ends to the DNA double-strand break (DSB) repair machinery, leading to telomere fusion with both telomeric and non-telomeric loci. The consequences of telomere fusions in promoting genome instability have long been appreciated through the breakage-fusion-bridge (BFB) cycle mechanism, although recent studies using high-throughput sequencing technologies have uncovered evidence of involvement in a wider spectrum of genomic rearrangements including chromothripsis. A critical step in cancer progression is the transition of a clone to immortality, through the stabilisation of the telomere repeat array. This can be achieved via the reactivation of telomerase, or the induction of the alternative lengthening of telomeres (ALT) pathway. Whilst telomere dysfunction may promote genome instability and tumour progression, by limiting the replicative potential of a cell and enforcing senescence, telomere shortening can act as a tumour suppressor mechanism. However, the burden of senescent cells has also been implicated as a driver of ageing and age-related pathology, and in the promotion of cancer through inflammatory signalling. Considering the critical role of telomere length in governing cancer biology, we review questions related to the prognostic value of studying the dynamics of telomere shortening and fusion, and discuss mechanisms and consequences of telomere-induced genome rearrangements.

Telomeres in cancer

Telomere shortening as a consequence of cell divisions during aging and chronic diseases associates with an increased cancer risk. Experimental data revealed that telomere shortening results in telomere dysfunction, which in turn affects tumorigenesis in two ways. First, telomere dysfunction suppresses tumor progression by the activation of DNA damage checkpoints, which induce cell cycle arrest (senescence) or apoptosis, as well as by inducing metabolic compromise and activation of immune responses directed against senescent cells. Second, telomere dysfunction promotes tumorigenesis by inducing chromosomal instability in tumor initiating cells, by inhibiting proliferative competition of non-transformed cells, and possibly, also by influencing tumor cell plasticity. The tumor promoting effects of telomere dysfunction are context dependent and require the loss of p53-dependent DNA damage checkpoints or other genetic modifiers that attenuate DNA damage responses possibly involving complex interactions of different genes. The activation of telomere stabilizing mechanisms appears as a subsequent step, which is required to enable immortal grotwh of emerging cancer cells. Here, we conceptually discuss our current knowledge and new, unpublished experimental data on telomere dependent influences on tumor initiation and progression.

Leukocyte telomere length-related genetic variants in ACYP2 contribute to the risk of esophageal carcinoma in Chinese Han population

BACKGROUND

Short leukocyte telomere length has been associated with significantly increased risk of esophageal carcinoma. A previous genome-wide association study demonstrated that ACYP2 was associated with leukocyte telomere length. However, the role of ACYP2 genetic variants on esophageal carcinoma susceptibility is still unknown. Therefore, we investigated whether ACYP2 polymorphisms have impact on the risk of esophageal carcinoma in Chinese.

MATERIALS AND METHODS

We conducted a case-control study among 386 cases and 495 healthy controls from northwest China. 14 SNPs in ACYP2 were selected and genotyped using Sequenom MassARRAY technology. Odds ratios (OR) and 95% confidence intervals (CIs) were calculated by unconditional logistic regression adjusting for age and gender.

RESULTS

We found that 1.34-fold increased risk of esophageal carcinoma is associated with the rs11125529 A allele compared with the rs11125529 C allele (OR=1.29, 95%CI: 1.02-1.62, p=0.030) under the additive model, after adjusted by age and gender. We also found rs11896604 and rs17045754 loci increased the esophageal carcinoma risk under the additive model (rs11896604: OR=1.34, 95%CI: 1.03-1.76, p=0.032; rs17045754: OR=1.36, 95%CI: 1.03-1.80, p=0.028). One main linkage block was observed across the locus. This block was comprised of seven closely linked SNPs: rs1682111, rs843752, rs10439478, rs843645, rs11125529, rs843711 and rs11896604. The haplotype analysis detected that haplotype "TTCTATG" increased the risk of esophageal carcinoma (OR=1.38, 95%CI: 1.04-1.82, p=0.025).

CONCLUSION

In conclusion, ACYP2 gene may be associated with an increased risk of esophageal carcinoma in Chinese Han populations. Future studies to address the biological function of this polymorphism in the development of esophageal carcinoma are warranted.

Long telomere length predicts poor clinical outcome in esophageal cancer patients

BACKGROUND

Abnormal telomere length is widely reported in various human cancers, and it is considered to be an important hallmark of cancer. However, there is remarkably little consensus on the value of telomere length in the prognostic evaluation of esophageal cancers. Here, we attempted to determine the association of variable telomere length with clinical outcome of esophageal cancer patients.

MATERIALS AND METHODS

Using real-time quantitative PCR, we examined relative telomere lengths (RTL) in a cohort of esophageal cancer and normal esophageal tissues, and statistically investigated the association between RTL and clinical outcomes of esophageal cancer patients.

RESULTS

The majority of esophageal cancers in this study had longer RTLs as compared to adjacent non-tumor tissues. Enhanced tumor RTL was associated with smoking habit, poor differentiation, advanced tumor stage, lymph node metastasis and cancer related death. In particular, a close relationship between longer RTL and poor survival was fully demonstrated by using cox regression and Kaplan-Maier survival curves.

CONCLUSIONS

We found frequent telomere elongation in esophageal cancer tissues, and demonstrated longer RTL may be an independent poor prognostic factor for esophageal cancer patients.

Skin phenotypes can offer some insight about the association between telomere length and cancer susceptibility

The role of telomere biology in cancer has been studied for a wide variety of different cancers but the association with telomere length has been controversial. This is because some cancers have been found to be associated with longer telomeres in circulating white cells whilst other cancer types are more common in individuals with shorter telomeres. Hence, there has been some skepticism as to whether telomere length may be helpful in estimating cancer risk. For melanoma, however, results have been fairly consistent showing that longer telomeres are associated with an increased risk. This link was first discovered because of a link between longer telomeres and a high number of naevi. In contrast, for cutaneous squamous cell carcinomas, the relationship is reversed with higher risk in individuals with shorter telomeres. Differences in skin phenotypes with the presence of high number of naevi versus photoageing with solar elastosis and solar keratoses have already been valuable for dermatologists as the former phenotype is associated with melanoma whilst the latter is more common in patients with squamous cell carcinoma of the skin. The hypothesis is that the differences in cutaneous phenotypes already observed by dermatologists for skin cancers may, in fact, be useful as well for cancer prediction in general as it may reflect underlying telomere biology. This manuscript will address the evidence for links between telomere biology, skin phenotypes and cancer risk.