Sometimes short telomeres prolong life
Telomeres are repetitive DNA sequences at the ends of chromosomes. In somatic cells, telomeres shorten with each cell division until a critical length is reached, after which the cell enters a phase of physiological aging or dies.
At the same time, in actively dividing cells, such as germ and stem cells, the length of these protective fragments of chromosomes is restored due to the activity of the enzyme telomerase. Tumor cells can also activate telomerase, which gives them the ability to divide indefinitely with corresponding consequences for the patient. However, researchers from the University of Copenhagen have found that the level of telomerase use by individual cancer cells depends on the gene variants they express associated with the activity of this enzyme.
Telomere shortening is an inevitable age-related process that can be accelerated by factors such as obesity and smoking. Most of the studies have revealed a relationship between short telomere length and high mortality, including from malignant diseases; at the same time, a number of studies have not found such an association.
A possible explanation for this contradiction may be that the relationship between short telomeres and cancer mortality is correlative, but the causal nature may belong to other factors (age and lifestyle) that were not taken into account during earlier studies. Genetic variations of several telomere length-associated genes (TERC, TERT, OBFC1) do not depend on age and lifestyle. Therefore, the authors decided to analyze the relationship between telomere length and cancer mortality using genetic analysis.
To do this, they used data collected within the framework of two prospective cohort studies, in which 64,637 people participated, whose health status was monitored in the period from 1991 to 2011. All participants filled out special questionnaires, after which they underwent a physical examination and donated blood for biochemical and genotypic tests, as well as for measuring the length of telomeres in leukocytes.
The following physical parameters were determined for each of the participants: body mass index, blood pressure, cholesterol level in the blood. Information was also collected on smoking, alcohol consumption, physical activity and socio-economic status. In addition, three single nucleotide polymorphisms for the TERC, TERT and OBFC1 genes were used to assess the level of presence of alleles associated with short telomeres.
During the study, 7,607 participants died, 2,420 of them from cancer. In general, as expected, shorter telomere length in leukocytes was associated with age and other parameters, such as body mass index and smoking, as well as with mortality from any cause, including cancer. At the same time, unexpectedly for the researchers, it turned out that a higher level of the presence of telomere-shortening alleles was associated with reduced mortality from cancer, but not with reduced mortality from other causes. Apparently, the genetically determined shortening of telomeres in cancer patients has a positive effect by suppressing uncontrolled division of malignant cells.
Based on the results obtained, the authors concluded that long telomeres are an advantage for cancer cells, providing the possibility of their multiple division, thereby increasing the mortality of cancer patients.
Article by L. Rode et al. Peripheral Blood Leukocyte Telomere Length and Mortality Among 64,637 Individuals From the General Population is published in the Journal of the National Cancer Institute.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on BioQuick News:
Study Associates Genes for Shorter Telomeres with Decreased Cancer Mortality.
13.04.2015