Association between functional TERT promoter polymorphism rs2853669 and cervical cancer risk in South Indian women

Telomere length assessment and molecular characterization of TERT gene promoter in periampullary carcinomas

Genetic and epigenetic alterations of the telomere maintenance machinery like telomere length and telomerase reverse transcriptase (encoded by TERT gene) are reported in several human malignancies. However, there is limited knowledge on the status of the telomere machinery in periampullary carcinomas (PAC) which are rare and heterogeneous groups of cancers arising from different anatomic sites around the ampulla of Vater. In the current study, we investigated the relative telomere length (RTL) and the most frequent genetic and epigenetic alterations in the TERT promoter in PAC and compared it with tumor-adjacent nonpathological duodenum (NDu). We found shorter RTLs (1.27 vs 1.33, P = 0.01) and lower TERT protein expression (p = 0.04) in PAC tissues as compared to the NDu. Although we did not find any mutation at two reactivating hotspot mutation sites of the TERT promoter, we detected polymorphism in 45% (9/20) of the cases at rs2853669 (T > C). Also, we found a hypermethylated region in the TERT promoter of PACs consisting of four CpGs (cg10896616 with Δβ 7%; cg02545192 with Δβ 9%; cg03323598 with Δβ 19%; and cg07285213 with Δβ 15%). In conclusion, we identified shorter telomeres with DNA hypermethylation in the TERT promoter region and lower TERT protein expression in PAC tissues. These results could be used further to investigate molecular pathology and develop theranostics for PAC.

Association Between Potentially Functional Variants in chr5q14 and the Risk of Cervical Cancer in a Chinese Population

Cervical cancer is a complex polygenic disease, and the interaction between single-nucleotide polymorphisms (SNPs) may lead to differences in the incidence and susceptibility of cervical cancer. In this study, we explored whether three potentially functional SNPs-rs59661306, rs257847, and rs637442 with reference/alternative alleles A/G, C/T, and T/G, respectively-in chr5q14 were related to cervical cancer risk in a Chinese population. A total of 703 samples were collected, including 215 patients with cervical cancer and 488 normal controls. The SNP genotyping was determined by using polymerase chain reaction-restriction fragment length polymorphism. There was an association between the AG rs59661306 genotype or the GG rs59661306 genotype and cervical cancer risk, and the percentage of cancer patients with the A/G rs59661306 genotype plus the percentage of cancer patients with the G/G rs59661306 genotype (AG + GG) was significantly higher than the percentage of AG + GG healthy women in the control group. There was no association between either the rs257847 or the rs637442 and cervical cancer risk. Genotype analysis showed that the genotype CT of rs257847 in combination with the AG, GG, and AG + GG genotypes of rs59661306 were associated with a higher cervical cancer risk, and that the genotypes TG and TG + GG of rs637442 in combination with the AG and AG + GG genotypes of rs59661306 were also associated with a higher cervical cancer risk. These findings indicate that rs59661306, rs257847, and rs637442 may be susceptible loci for cervical cancer. Our study advances the understanding of SNPs that are responsible for cervical cancer susceptibility.

The Drivers, Mechanisms, and Consequences of Genome Instability in HPV-Driven Cancers

Human papillomavirus (HPV) is the causative driver of cervical cancer and a contributing risk factor of head and neck cancer and several anogenital cancers. HPV's ability to induce genome instability contributes to its oncogenicity. HPV genes can induce genome instability in several ways, including modulating the cell cycle to favour proliferation, interacting with DNA damage repair pathways to bring high-fidelity repair pathways to viral episomes and away from the host genome, inducing DNA-damaging oxidative stress, and altering the length of telomeres. In addition, the presence of a chronic viral infection can lead to immune responses that also cause genome instability of the infected tissue. The HPV genome can become integrated into the host genome during HPV-induced tumorigenesis. Viral integration requires double-stranded breaks on the DNA; therefore, regions around the integration event are prone to structural alterations and themselves are targets of genome instability. In this review, we present the mechanisms by which HPV-dependent and -independent genome instability is initiated and maintained in HPV-driven cancers, both across the genome and at regions of HPV integration.

Evaluation of possible role of the hTERT gene rs2853669 polymorphism in the development of colorectal cancer as a genetic risk factor

Colorectal cancer (CRC) is the second deadliest malignancy. Human telomerase reverse transcriptase (hTERT) gene has been identified as one of the potential cancer susceptibility genes. We evaluated the relationship between the risk of CRC and CRC's clinicopathological features of the hTERT rs2853669 (A > G/T > C, by the chain direction) polymorphism in Turkish population. The rs2853669 polymorphism was investigated with the LightCycler 96 device in 100 CRC patients and 327 controls. We found that the rs2853669 polymorphism AG/GG genotypes in genetic models reduced the risk of CRC. However, there was no significant relationship between rs2853669 polymorphism and clinicopathological features of CRC in studied population. The results of this study showed that the risk of colorectal cancer is significantly reduced in the individuals having the G (C) allele. Our recommendation is to analyze the hTERT gene expression by studying the hTERT promoter mutations with this polymorphism in colorectal cancer.

Anchored Multiplex PCR Custom Melanoma Next Generation Sequencing Panel for Analysis of Circulating Tumor DNA

Detection of melanoma mutations using circulating tumor DNA (ctDNA) is a potential alternative to using genomic DNA from invasive tissue biopsies. To date, mutations in the GC-rich TERT promoter region, which is commonly mutated in melanoma, have been technically difficult to detect in ctDNA using next-generation sequencing (NGS) panels. In this study, we developed a custom melanoma NGS panel for detection of ctDNA, which encompasses the top 15 gene mutations in melanoma including the TERT promoter. We analyzed 21 stage III and IV melanoma patient samples who were treatment-naïve or on therapy. The overall detection rate of the custom panel, based on BRAF/NRAS/TERT promoter mutations, was 14/21 (67%) patient samples which included a TERT C250T mutation in one BRAF and NRAS mutation negative sample. A BRAF or NRAS mutation was detected in the ctDNA of 13/21 (62%) patients while TERT promoter mutations were detected in 10/21 (48%) patients. Co-occurrence of TERT promoter mutations with BRAF or NRAS mutations was found in 9/10 (90%) patients. The custom ctDNA panel showed a concordance of 16/21 (76%) with tissue based-detection and included 12 BRAF/NRAS mutation positive and 4 BRAF/NRAS mutation negative patients. The ctDNA mutation detection rate for stage IV was 12/16 (75%) and for stage III was 1/5 (20%). Based on BRAF, NRAS and TERT promoter mutations, the custom melanoma panel displayed a limit of detection of ~0.2% mutant allele frequency and showed significant correlation with droplet digital PCR. For one patient, a novel MAP2K1 H119Y mutation was detected in an NRAS/BRAF/TERT promoter mutation negative background. To increase the detection rate to >90% for stage IV melanoma patients, we plan to expand our custom panel to 50 genes. This study represents one of the first to successfully detect TERT promoter mutations in ctDNA from cutaneous melanoma patients using a targeted NGS panel.

Human TERT promoter polymorphism rs2853669 is associated with cancers: an updated meta-analysis

The polymorphism rs2853669 in the telomerase reverse transcriptase gene (TERT) promoter region is widely investigated for the risk of different cancers. However, previous results remained inconclusive. Thus, we performed this updated meta-analysis to comprehensively evaluate the association between rs2853669 and the susceptibility of human cancer. A systematic literature search via PubMed, EMBASE, Cochrane Library, and Web of Science databases was conducted that produced a total of 19 eligible studies containing 23,085 subjects. The relationship was calculated with the odds ratio (OR) and 95% confidence intervals (CIs). Statistical analyses were performed using the RevMan 5.4 software. The analysis indicated that rs2853669 is associated with an enhanced risk of overall cancer risk. From subgroup analysis, a significantly increased association in five genetic models (p < 0.05) was found among Asians, but no association was observed in Caucasians. Although we did not find any significant correlation between rs2853669 and breast cancer, an increased and statistically significant association was found for both lung cancer and acute myeloid leukemia. We did not find any association in other cancer types during stratified analysis. Our meta-analysis suggests that rs2853669 polymorphism in TERT gene is associated with an increased risk of overall cancer susceptibility, particularly in the Asian population. Moreover, rs2853669 is significantly associated with lung cancer and acute myeloid lymphoma. However, large-scale studies are needed to confirm our findings.

TERT-Regulation and Roles in Cancer Formation

Telomerase reverse transcriptase (TERT) is a catalytic subunit of telomerase. Telomerase complex plays a key role in cancer formation by telomere dependent or independent mechanisms. Telomere maintenance mechanisms include complex TERT changes such as gene amplifications, TERT structural variants, TERT promoter germline and somatic mutations, TERT epigenetic changes, and alternative lengthening of telomere. All of them are cancer specific at tissue histotype and at single cell level. TERT expression is regulated in tumors via multiple genetic and epigenetic alterations which affect telomerase activity. Telomerase activity via TERT expression has an impact on telomere length and can be a useful marker in diagnosis and prognosis of various cancers and a new therapy approach. In this review we want to highlight the main roles of TERT in different mechanisms of cancer development and regulation.