The TERT MNS16A polymorphism contributes to cancer susceptibility: meta-analysis of the current studies

Association of hTERT MNS16A polymorphism with clinical outcomes of North Indian lung cancer patients undergoing platinum-based doublet chemotherapy

BACKGROUND

Telomerase has been linked to aging and cancer. The MNS16A polymorphism in the hTERT gene plays a significant role in modulating telomerase activity and highlights the complexity of telomere-related genetics in cancer research.

EXPERIMENTAL DESIGN

We genotyped 401 lung-cancer samples treated with platinum-based chemotherapy to identify the MNS16A polymorphism. We assessed overall survival using the Kaplan-Meier method and Cox regression analysis for adjusted hazard ratios. Stratified analyses evaluated risks for subgroups based on clinicopathologic parameters, outcomes, and toxicity calculated.

RESULTS

Our findings show no significant link between MNS16A polymorphism and lung-cancer survival. However, in squamous cell carcinoma (SQCC) patients, the SS genotype was associated with poorer survival (p = 0.004). Patients with LS + SS genotypes responded better to gemcitabine in univariate (p = 0.003) and multivariate analyses (p = 0.014). The LS genotype was linked to a lower risk of progression to stage 4 (p = 0.011) and metastasis (p = 0.015) but an increased risk of T4 tumor size (p = 0.026). No significant correlations were found between MNS16A polymorphism and treatment-related toxicities.

CONCLUSION

The MNS16A polymorphism does not significantly impact overall lung-cancer survival but affects specific subgroups, influencing certain lung-cancer subtypes and treatment responses while having limited predictive value for overall outcomes or toxicity risks.

MNS16A VNTR polymorphism of human telomerase gene: Elucidation of a gender specific potential allele associated with type 2 diabetes in Bangladeshi population

BACKGROUND

Type 2 diabetes (T2D) is a multifactorial disorder that affects multi-organ and can alter telomerase (encoded by hTERT gene) activity and thus, may affect telomere length. The variable number of tandem repeats MNS16A in hTERT gene facilitates extension of telomeres by regulating telomerase. In the present study, genetic analysis of MNS16A tandem repeats in hTERT gene was performed with the aim of finding out any association of allelic and genotypic variations with the risk of T2D in Bangladeshi population.

METHODS

A total of unrelated 395 individuals with T2D and 247 healthy individuals were included in the study. The genotypic and allelic frequencies were determined using allele specific polymerase chain reaction. The association of allelic and genotypic frequencies with risk of T2D was analyzed using logistic regression analysis on the basis of odds ratio at 95% confidence interval. Hardy-Weinberg equilibrium (HWE) test was performed to evaluate the uniformity of the genotypic frequencies and deviation from the HWE was tested using Chi-square test.

RESULTS

Logistic regression analyses revealed significant association of short allele containing 243 bp (OR: 1.37 and p = 0.03) with T2D, when the long alleles (commonly found) were considered as reference. The heterozygous genotype 272/302 was significantly associated with the decreased risk of T2D (OR: 0.33, p = 0.001). The combined results of genotypes indicated that the MNS16A polymorphism was significantly associated with the increased risk of T2D under the dominant model (LL vs SL + SS; OR: 2.62, p < 0.0001). Interestingly, short allele 243 was associated with the risk of disease only in male population (OR: 1.62, p = 0.02). The genotype 272/302 was also found to be associated with the decreased risk of T2D when respective data for male was analyzed individually.

CONCLUSIONS

We have identified four variable number of tandem repeats with varying patterns of association with T2D in Bangladeshi population and to extend our knowledge of understanding regarding these VNTRs, further large-scale studies are warranted.

Variability within the human TERT gene, telomere length and predisposition to chronic lymphocytic leukemia

Background: The human telomerase reverse transcriptase (TERT) gene encodes the catalytic subunit of telomerase that is essential for maintenance of telomere length. We aimed to find out whether variability within the TERT gene could be associated with telomere length and development of the disease in non-treated patients with chronic lymphocytic leukemia (CLL). Materials and methods: Telomere length, rs2736100, rs2853690, rs33954691, rs35033501 single-nucleotide polymorphisms, and variable number of tandem repeats (VNTR-MNS16A) were assessed in patients at diagnosis. In addition, blood donors served as controls for the polymorphism studies. Results: The minor rs35033501 A variant was more frequent among CLL patients than in healthy controls (OR=3.488, p=0.039). CLL patients over 60 years of age were characterized with lower disease stage at diagnosis (p=0.001 and p=0.008, for the Rai and Binet criteria, respectively). The MNS16A VNTR-243 short allele was more frequent in patients with a low disease stage (p=0.020 and p=0.028, for the Rai and Binet staging system) and also among older patients having longer telomeres (p=0.046). Patients with Rai 0-I stage were characterized with longer telomeres than those with more advanced disease (p=0.030). This relationship was especially pronounced in patients carrying the rs2736100 C allele, independently of the criteria used, ie, Binet (p=0.048) or Rai (p=0.001). Conclusion: Our results showed that the genetic variation within the TERT gene seems to play a regulatory role in CLL and telomere length.

Leukocyte Telomere Length Shortening, hTERT Genetic Polymorphisms and Risk of Childhood Acute Lymphoblastic Leukemia

Background: Telomeres are involved in chromosomal stability, cellular immortality and tumorigenesis. Human telomerase reverse transcriptase (TERT) is essential for the maintenance of telomere DNA length. Recently, a variable tandem-repeats polymorphism, MNS16A, located in the downstream region of the TERT gene, was reported to have an effect on TERT expression and telomerase activity. Previous studies have linked both relative telomere length (RTL) and TERT variants with cancer. Therefore, we evaluated associations between RTL, TERT gene polymorphisms (hTERT, rs2735940 C/T and MNS16A Ins/Del) and risk of childhood acute lymphoblastic leukemia (ALL) in an Iranian population. Methods: RTL was determined by a multiplex quantitative PCR-based method, and variants of the hTERT, rs2735940 C/T and MNS16A Ins/Del, were genotyped by amplification refractory mutation system PCR (ARMS-PCR), and PCR, respectively. Results: Our results indicated that RTL was shorter in ALL patients (1.53±0.12) compared to the control group (2.04±0.19) (P=0.029). However, no associations between hTERT gene variants or haplotypes and the risk of childhood ALL were observed (P>0.05). Also hTERT polymorphisms were not associated with RTL or patient clinicopathological characteristics, including age (P=0.304), sex (P=0.061) organomegally (P=0.212) CSF involvement (P=0.966) or response to treatment (P=0.58). Conclusions: We found that telomere attrition may be related to the pathogenesis of childhood ALL, irrespective to TERT variants.

MNS16A tandem repeat minisatellite of human telomerase gene: functional studies in colorectal, lung and prostate cancer

MNS16A, a functional polymorphic tandem repeat minisatellite, is located in the promoter region of an antisense transcript of the human telomerase reverse transcriptase gene. MNS16A promoter activity depends on the variable number of tandem repeats (VNTR) presenting varying numbers of transcription factor binding sites for GATA binding protein 1. Although MNS16A has been investigated in multiple cancer epidemiology studies with incongruent findings, functional data of only two VNTRs (VNTR-243 and VNTR-302) were available thus far, linking the shorter VNTR to higher promoter activity.

For the first time, we investigated promoter activity of all six VNTRs of MNS16A in cell lines of colorectal, lung and prostate cancer using Luciferase reporter assay. In all investigated cell lines shorter VNTRs showed higher promoter activity. While this anticipated indirect linear relationship was affirmed for colorectal cancer SW480 (P = 0.006), a piecewise linear regression model provided significantly better model fit in lung cancer A-427 (P = 6.9 × 10⁻⁹) and prostate cancer LNCaP (P = 0.039). In silico search for transcription factor binding sites in MNS16A core repeat element suggested a higher degree of complexity involving X-box binding protein 1, general transcription factor II–I, and glucocorticoid receptor alpha in addition to GATA binding protein 1.

Further functional studies in additional cancers are requested to extend our knowledge of MNS16A functionality uncovering potential cancer type-specific differences. Risk alleles may vary in different malignancies and their determination in vitro could be relevant for interpretation of genotype data.

The frequency and prognostic effect of TERT promoter mutation in diffuse gliomas

Mutations in the telomerase reverse transcriptase gene promoter (TERTp) are common in glioblastomas (GBMs) and oligodendrogliomas (ODGs), and therefore, have a key role in tumorigenesis and may be of prognostic value. However, the extent of their prognostic importance in various gliomas is controversial. We studied 168 patients separated into five groups: Group 1: 65 patients with ODG carrying an IDH1 or IDH2 mutation (IDH-mutant) and 1p/19q–codeletion, Group 2: 23 patients with anaplastic astrocytoma (AA), IDH-mutant, Group 3: 13 patients with GBM, IDH-mutant, Group 4: 15 patients with AA, IDH-wildtype (WT), and Group 5: 52 patients with GBM, IDH-WT. TERTp mutations were found in 96.9%, 4.4%, 76.9%, 20.0%, and 84.6% of patients in Groups 1, 2, 3, 4, and 5, respectively. The R132H mutation in IDH1 was found in 60.5% (23/38) of patients in the AA cohort (Groups 2 and 4) and 20.0% (13/65) of patients from our GBM cohort (Groups 3 and 5), whereas all patients with ODG (Group 1) had a mutation either in IDH1 (n = 62) or IDH2 (n = 3). Using Kaplan Meier survival analysis, we found that the TERTp mutation was correlated with poor overall survival (OS) in Groups 2 and 4 combined (P = 0.001) and in Group 4 (P = 0.113), and in multivariate analysis, the TERTp mutant group was associated with significantly poor survival in Group 5 (P = 0.045). However, IDH mutation, MGMT methylation, and younger patient age (<55 years old) were significantly correlated with favorable OS (all P < 0.05) in our cohort of astrocytic and ODGs. In patients with ODG (Group 1), mutant IDH and TERTp did not have prognostic value because these mutations were universally present. Based on the revised 2016 WHO classification of gliomas, we found that TERTp mutation was frequently present in patients with GBM or ODG and because it was strongly correlated with poor survival outcome in patients with IDH-WT GBM in multivariate analysis, it may be of prognostic value in this subgroup of patients with gliomas.

Glioma diagnostics and biomarkers: an ongoing challenge in the field of medicine and science

Glioma is the most common brain tumor. For the more aggressive form, glioblastoma, standard treatment includes surgical resection, irradiation with adjuvant temozolomide and, on recurrence, experimental chemotherapy. However, the survival of patients remains poor. There is a critical need for minimally invasive biomarkers for diagnosis and as measures of response to therapeutic interventions. Glioma shed extracellular vesicles (EVs), which invade the surrounding tissue and circulate within both the cerebrospinal fluid and the systemic circulation. These tumor-derived EVs and their content serve as an attractive source of biomarkers. In this review, we discuss the current state of the art of biomarkers for glioma with emphasis on their EV derivation.

The associations between the Val158Met in the catechol-O-methyltransferase (COMT) gene and the risk of uterine leiomyoma (ULM)

The Val158Met polymorphism of the COMT gene has been implicated in susceptibility to uterine leiomyoma (ULM), but the reported results were inconclusive. The aim of the study was to evaluate the Val158Met polymorphism of the COMT gene and the risk of ULM by meta-analysis. A comprehensive electronic search for relevant articles was conducted in Pubmed, Embase, CNKI, Wanfang, and Weipu databases. Statistical analysis was performed by using the Revman4.2 software and Stata10.0 software. A total of 7 articles including 12 case-control studies were identified in this meta-analysis. The results showed that the polymorphism was associated with decreased risk of ULM (Met/Met+Val/Met vs. Met/Met: OR=0.84, 95% CI=0.70-0.99, Z=2.07, p=0.04). In the subgroup analyses by ethnicity, significant decreased risk was found among the black populations (OR=0.68, 95% CI=0.48-0.97, Z=2.15, p=0.03). The current meta-analysis suggested that the Val158Met polymorphism in the COMT gene was associated with decreased risk of ULM, especially in the black population. Future studies are needed to validate our conclusions.