Telomere dynamics play a crucial role in the maintenance of chromosome integrity; changes in telomere length may thus contribute to the development of various diseases including cancer. Understanding the role of telomeric DNA in carcinogenesis and detecting the presence of cell-free telomeric DNA (cf-telDNA) in body fluids offer a potential biomarker for novel cancer screening and diagnostic strategies. Liquid biopsy is becoming increasingly popular due to its undeniable benefits over conventional invasive methods. However, the organization and function of cf-telDNA in the extracellular milieu are understudied. This paper provides a review based on 3,398,017 cancer patients, patients with other conditions, and control individuals with the aim to shed more light on the inconsistent nature of telomere lengthening/shortening in oncological contexts. To gain a better understanding of biological factors (e.g., telomerase activation, alternative lengthening of telomeres) affecting telomere homeostasis across different types of cancer, we summarize mechanisms responsible for telomere length maintenance. In conclusion, we compare tissue- and liquid biopsy-based approaches in cancer assessment and provide a brief outlook on the methodology used for telomere length evaluation, highlighting the advances of state-of-the-art approaches in the field.

CNVs are structural alterations in the genome that involve the duplication or deletion of DNA segments, contributing to genetic diversity and playing a crucial role in evolution and development of various diseases and disorders. Massively parallel sequencing (MPS) has revolutionized the field of genetic analysis and contributed significantly to routine clinical diagnosis and screening. It offers a precise method for detecting copy number variations (CNVs) with exceptional accuracy. In this context, non-invasive prenatal test (NIPT) based on the sequencing of cell-free DNA (cfDNA) from pregnant women's plasma using a low coverage whole genome MPS (WGS) approach represents a valuable source for population studies. Here, we analyzed genomic data of 12 732 pregnant women from the Slovak (9 230), Czech (1 583), and Hungarian (1 919) populations. We identified 5 062 CNVs ranging from 200 kbp and described its basic characteristics and differences between the subject populations. Our results suggest that re-analysis of sequencing data from routine WGS assays has the potential to obtain CNVs population frequencies, and may provide valuable information to support classification and interpretation of this type of genetic variation.

Background COVID-19 caused by the SARS-CoV-2 infection may result in various disease symptoms and severity, ranging from asymptomatic, through mildly symptomatic, up to very severe and even fatal cases. Although environmental, clinical, and social factors play important roles in both susceptibility to the SARS-CoV-2 infection and progress of COVID-19 disease, it is becoming evident that both pathogen and host genetic factors are important too. In this study, we report findings from whole-exome sequencing (WES) of 27 individuals who died due to COVID-19, especially focusing on frequencies of DNA variants in genes previously associated with the SARS-CoV-2 infection and the severity of COVID-19. Results We selected the risk DNA variants/alleles or target genes using four different approaches: 1) aggregated GWAS results from the GWAS Catalog; 2) selected publications from PubMed; 3) the aggregated results of the Host Genetics Initiative database; and 4) a commercial DNA variant annotation/interpretation tool providing its own knowledgebase. We divided these variants/genes into those reported to influence the susceptibility to the SARS-CoV-2 infection and those influencing the severity of COVID-19. Based on the above, we compared the frequencies of alleles found in the fatal COVID-19 cases to the frequencies identified in two population control datasets (non-Finnish European population from the gnomAD database and genomic frequencies specific for the Slovak population from our own database). When compared to both control population datasets, our analyses indicated a trend of higher frequencies of severe COVID-19 associated risk alleles among fatal COVID-19 cases. This trend reached statistical significance specifically when using the HGI-derived variant list. We also analysed other approaches to WES data evaluation, demonstrating its utility as well as limitations. Conclusions Although our results proved the likely involvement of host genetic factors pointed out by previous studies looking into severity of COVID-19 disease, careful considerations of the molecular-testing strategies and the evaluated genomic positions may have a strong impact on the utility of genomic testing.

Background: COVID-19 caused by SARS-CoV-2 infection may result in various disease symptoms and severity, ranging from asymptomatic, through mild, up to very severe and fatal cases. Although environmental, clinical, and social factors play important roles in both susceptibility to SARS-CoV-2 infection and COVID-19 disease progress, it is becoming evident that both pathogen and host genetic factors are important too. Here we report whole-exome sequencing (WES) findings of 27 individuals who died as a result of COVID-19 infection, especially focusing on frequencies of DNA variants in genes previously associated with SARS-CoV-2 infection and COVID-19 severity. Results: We selected risk DNA variants/alleles or target genes using four different approaches: 1) aggregated GWAS results from the GWAS Catalog; 2) selected publications from PubMed; 3) the aggregated results of the Host Genetics Initiative database; and 4) a commercial DNA variant annotation/interpretation tool providing its own knowledgebase. We divided these variants/genes into those reported to influence the susceptibility to SARS-CoV-2 infection and those influencing COVID-19 severity. Based on these, we compared frequencies of alleles among the fatal COVID-19 cases to frequencies identified in two population control datasets (non-Finnish European population from the gnomAD database and genomic frequencies specific for the Slovak population from our own database). Our comparisons delineated a trend of higher frequencies of severe COVID-19 associated risk alleles among fatal COVID-19 cases, when compared to both control population datasets. This trend reached statistical significance specifically when using the HGI derived variant list. We also analyzed other approaches to WES data evaluation, where we showed their usage as well as limitations. Conclusions: Although our results proved the likely involvement of host genetic factors pinned out by previous studies for COVID-19 disease severity, careful considerations about the molecular-testing strategies and the evaluated genomic positions may have a strong impact on the utility of genomic testing.