Telomeres are highly conserved tandem nucleotide repeats that include proximal double-stranded and distal single-stranded regions that in complex with shelterin proteins afford protection at chromosomal ends to maintain genomic integrity. Due to the inherent limitations of DNA replication and telomerase suppression in most somatic cells, telomeres undergo age-dependent incremental attrition. Short or dysfunctional telomeres are recognized as DNA double-stranded breaks, triggering cells to undergo replicative senescence. Telomere shortening, therefore, acts as a counting mechanism that drives replicative senescence by limiting the mitotic potential of cells. Telomere length, a complex hereditary trait, is associated with aging and age-related diseases. Epidemiological data, in general, support an association with varying magnitudes between constitutive telomere length and several disorders, including cancers. Telomere attrition is also influenced by oxidative damage and replicative stress caused by genetic, epigenetic, and environmental factors. Several single nucleotide polymorphisms at different loci, identified through genome-wide association studies, influence inter-individual variation in telomere length. In addition to genetic factors, environmental factors also influence telomere length during growth and development. Telomeres hold potential as biomarkers that reflect the genetic predisposition together with the impact of environmental conditions and as targets for anti-cancer therapies.

Mutations within the promoter of gene encoding telomerase reverse transcriptase subunit are frequent in many cancers including melanoma. Previously, the TERT promoter mutations were shown to associate with markers of poor outcome and reduced survival in patients with primary melanoma. In this study, we investigated the impact of the subtypes of TERT mutations on disease-free and melanoma-specific survival in 287 patients with stage I/II nonacral melanoma. Our results showed that of the three TERT promoter mutation subtypes, in multivariate models, the -138/-139 CC > TT tandem mutation associated with worst disease-free and melanoma-specific survival. In particular, in combination with BRAF/NRAS mutations, the -138/-139 CC > TT TERT promoter mutation associated with statistically significant poor disease-free and melanoma-specific survival with hazard ratios of 6.04 (95% CI 2.03-17.94, p = 0.001) and 12.59 (95% CI 2.18-72.70, p = 0.005), respectively. In contrast to the survival data, luciferase assays showed that the highest activity was observed in experiments with a promoter construct with -124 C > T mutation followed by the -138/-139 CC > TT and -146 C > T mutations, which showed similar activity. Based on previous reports, we speculate that the tandem mutation probably leads to greater genomic instability than the common TERT promoter mutations, hence the association with worst survival. However, the results from the study are only preliminary with limited patient data, therefore, require a cautious interpretation. The observations in this study, if confirmed, could have implications for melanoma patients treated with MAP-kinase inhibitors.

Telomere repeats at chromosomal ends, critical for genomic integrity, undergo age-dependent attrition and telomere length has been associated with different disorders including cancers. In this study, based on 1469 patients and 1158 healthy controls, we show a statistically significant (P = 6 × 10 ) association between increased telomere length and melanoma risk. Mendelian randomization, using 5 telomere length-associated polymorphisms, ruled out confounding factors or reverse causality and showed association between increased telomere length and melanoma risk with odds ratio of 2.66 (95% confidence interval: 2.07-3.25). Age-dependent telomere attrition was faster in melanoma cases than controls (P = .01). The carriers of a highly penetrant germline -57A>C TERT promoter mutation, in a previously reported melanoma family, had longer telomeres than the noncarriers. The mutation causes increased TERT and telomerase levels through creation of a binding motif for E-twenty six (ETS) transcription factors and the carriers develop melanoma with an early age of onset and rapid progression to metastasis. In analogy, we hypothesize that increased telomere length in melanoma patients reflects stochastic increased telomerase levels due to common genetic variation. Paradoxically, we observed shorter telomeres (P = 1 × 10 ) in primary tumors from unrelated melanoma patients with (121) than without (170) somatic TERT promoter mutations that similar to the germline mutation, also create binding motifs for ETS transcription factors. However, the age-dependent telomere attrition was faster in tumors with the TERT promoter mutations than in those without such mutations. Besides a robust association between increased telomere length and risk, our data show a perturbed telomere homeostasis in melanoma.

BACKGROUND: Telomeres, repetitive DNA capping ends of eukaryotic chromosomes, are important in the maintenance of genomic integrity. Perturbed telomeres are common features of many human malignancies, including colorectal cancer. METHODS: Telomere length (TL), measured by a Monochrome Multiplex Real-Time qPCR, was investigated in tumour tissues, adjacent mucosa, and blood from patients with colorectal cancer with different clinicopathological features and its impact on patient survival. TL was also measured in a limited number of liver metastases, non-cancerous liver tissues or corresponding tissues from the same patients. RESULTS: TL in tumour tissues was shorter than in the adjacent mucosa (P < 0.0001). Shorter TL was observed in tumours with lower stage than in those with advanced stages (P = 0.001). TL was shorter in tumours at the proximal than at the distal sites of the colon (P < 0.0001). Shorter TL was also associated with microsatellite instability (P = 0.001) and mucinous tumour histology (P < 0.0001). Patients with a smaller TL ratio between tumour tissues and the adjacent mucosa were associated with increased overall survival (P = 0.022). Metastasised tumours had shorter telomeres than the adjacent non-cancerous liver tissues (P = 0.0005). CONCLUSIONS: Overall, the results demonstrate differences in TL between tumours and the adjacent mucosa, between tumours located at different sites and association with patient survival.

Telomere repeats at chromosomal ends, critical to genomic integrity, undergo age-dependent attrition. Telomere length, a polygenic trait, has been associated with risk of several disorders including cancers. In contrast to association of long telomeres with increased risk of several cancers, including melanoma, emerging reports suggest that short telomeres predict poor survival in patients with different cancers. In this study based on 1019 stage I and II cutaneous melanoma patients, we show an association between the patients with short telomeres and poor melanoma-specific survival (HR 2.05, 95% CI 1.33–3.16) compared to patients with long telomeres. Due to inverse correlation between age and telomere length (r -0.19, P < 0.0001), we stratified the patients into quantiles based on age at diagnosis and also carried out age-matched analysis. The effect of short telomeres on survival was determined by using multivariate Cox regression that included composite genetic risk score computed from genotyping of the patients for telomere-length associated polymorphisms. The effect of decreased telomere length on poor melanoma-specific survival was particularly strong in patients within the age quantile below 30 years (HR 3.82, 95% CI 1.10–13.30) and between 30–40 years (HR 2.69, 95% CI 1.03–7.03). Our study shows that in contrast to increased melanoma risk associated with increased telomere length, decreased telomere length predicts poor survival in melanoma subgroups.

Basal cell carcinoma (BCC) represents the most commonly diagnosed human cancer among persons of European ancestry with etiology mainly attributed to sun-exposure. In this study we investigated mutations in coding and flanking regions of PTCH1 and TP53 and noncoding alterations in the TERT and DPH3 promoters in 191 BCC tumors. In addition, we measured CpG methylation within the TERT hypermethylated oncological region (THOR) and transcription levels of the reverse transcriptase subunit. We observed mutations in PTCH1 in 58.6% and TP53 in 31.4% of the tumors. Noncoding mutations in TERT and DPH3 promoters were detected in 59.2% and 38.2% of the tumors, respectively. We observed a statistically significant co-occurrence of mutations at the four investigated loci. While PTCH1 mutations tended to associate with decreased patient age at diagnosis; TP53 mutations were associated with light skin color and increased number of nevi; TERT and DPH3 promoter with history of cutaneous neoplasms in BCC patients. Increased reverse transcriptase subunit expression was observed in tumors with TERT promoter mutations and not with THOR methylation. Our study signifies, in addition to the protein altering mutations in the PTCH1 and TP53 genes, the importance of noncoding mutations in BCC, particularly functional alterations in the TERT promoter. Basal cell carcinoma (BCC) accounts for about 80 percent of all skin cancers and it is the most commonly diagnosed neoplasm among the Caucasian population 1-3. The tumor originates from stem cells within hair follicles or the interfollicular epidermis and infundibulum undergoing ultraviolet (UV) radiation induced mutagenesis 4-6. Basal cell carcinoma rarely metastasizes; however, due to sheer number of people affected, the disease poses a considerable health hazard as it causes extensive morbidity through local invasion and tissue destruction 7. The most common genetic alterations in BCC involve the Hedgehog receptor patched 1 (PTCH1) and the cell cycle regulator TP53 and the mutations in both genes predominantly reflect UV etiology 8. Exome sequencing based studies, besides denoting BCC as the cancer with highest mutation burden, have also identified less frequent alterations in genes other than PTCH1 and TP53 8,9. Germline mutations PTCH1 also occur in patients with Gorlin syndrome, a Mendelian disease with a high prevalence of BCC 10. Aberrant activation of the Hedgehog pathway is common in sporadic BCC either through mutations in the PTCH1 gene, activating mutations in smoothened (SMO) or loss-of-function mutations in suppressor of fused homolog (SUFU) 9,11,12. Ubiquitous hyper-activation of the Hedgehog has led to development of inhibitors targeting G-protein coupled receptor Smoothened for treatment of advanced BCC 11,12. While, the studies based on exome sequencing have confirmed the centrality of PTCH1 mutations in BCC, the variants within smoothened are reportedly causal in resistance to the inhibitors 8. TP53 encodes a transcription factor, which is a tumor suppressor involved in cel...

Telomere length per se a heritable trait has been reported to be associated with different diseases including cancers. In this study, based on arsenic-exposed 528 cases with basal cell carcinoma (BCC) of skin and 533 healthy controls, we investigated effect of telomere length, measured by real-time PCR, on the disease risk. We observed a statistically significant association between decreased telomere length and increased BCC risk [odds ratio (OR) = 5.92, 95% confidence interval (CI) = 3.92 to 9.01, P < 0.0001]. Due to confounder effect of arsenic exposure, in a two-sample Mendelian randomization (MR), telomere length associated single-nucleotide polymorphisms as instrument variables violated valid assumptions; however, one-sample MR adjusted for arsenic exposure indicated an increased risk of BCC with short telomeres. The interaction between arsenic exposure and telomere length on BCC risk was statistically significant (P = 0.02). Within each tertile based on arsenic exposure, the individuals with shorter telomeres were at an increased risk of BCC, with highest risk being in the highest exposed group (OR = 16.13, 95% CI = 6.71 to 40.00, P < 0.0001), followed by those in medium exposure group and low exposure group. The combined effect of highest arsenic exposure and shortest telomeres on BCC risk (OR = 10.56, 95% CI = 5.14 to 21.70) showed a statistically significant departure from additivity (interaction contrast ratio 6.56, P = 0.03). Our results show that in the presence of arsenic exposure, decreased telomere length predisposes individuals to increased risk of BCC, with the effect being synergistic in individuals with highest arsenic exposure and shortest telomeres.

Detailed examination of tumor components is leading-edge to establish personalized cancer therapy. Accompanying research on cell-free DNA, the cell count of circulating tumor cells (CTCs) in patient blood is seen as a crucial prognostic factor. The potential of CTC analysis is further not limited to the determination of the overall survival rate but sheds light on understanding inter-and intratumoral heterogeneity. In this regard, commercial CTC isolation devices combining an efficient enrichment of rare cells with a droplet deposition of single cells for downstream analysis are highly appreciated. The Liquid biopsy platform CTCelect was developed to realize a fully-automated enrichment and single cell dispensing of CTCs from whole blood without pre-processing. We characterized each process step with two different carcinoma cell lines demonstrating up to 87 % enrichment (n = 10) with EpCAM coupled immunomagnetic beads, 73 % optical detection and dispensing efficiency (n = 5). 40 to 56.7 % of cells were recovered after complete isolation from 7.5 ml untreated whole blood (n = 6). In this study, CTCelect enabled automated dispensing of single circulating tumor