Rumena Petkova

DO WE NEED MORE HUMAN EMBRYONIC STEM CELL LINES

ABSTRACT The enormous potential of human embryonic stem cells is fueling continuous research aimed at establishment of new lines of these cells. Currently, research groups from 24 countries have reported derivation of over 1000 human embryonic stem cell lines. Because of the controversy surrounding the derivation of these cells from human embryos it is important to clarify whether the existing hESC lines are sufficient for basic research and future therapeutic applications. Here we briefly review some of the most important arguments justifying the need for continuing derivation of human embryonic stem cell lines.

Children of the Sun, Children of the Moon—A Mini-Panel for Assessment of Inter-Individual Variation Between the Capacity of Healthy Individuals to Repair Everyday Genotoxic Insults

ABSTRACT The DNA repair machinery of healthy human cells usually manages the consequences of the daily barrage of DNA damage for years and decades before any adverse effects related to genotoxic impact become manifest. There is significant variance, however, even between healthy individuals, in regard to their ability to detect and repair genotoxic damage. Some aspects of this variance exist throughout the life of the individual (genetic factors, such as polymorphisms in genes coding for products acting in the repair of DNA damage), while others (e.g. telomere length) may be the outcome of the genotype-phenotype interplay, modified by environmental factors. Numerous markers for assessment of capacity to combat genotoxic damage have been described so far, with only some of them having a value of their own under physiological and/or pathological conditions. In the present study we provide the results from the evaluation of a mini-panel (p53 P72R, XPCins83PAT, rate of telomere attrition) for assessing the capacity of healthy individuals to repair genotoxic damage, and outline the possible fields of application.

What's your poison? Impact of individual repair capacity on the outcomes of genotoxic therapies in cancer. Part II - information content and validity of biomarkers for individual repair capacity in the assessment of outcomes of anticancer therapy.

ABSTRACT The individual variance in the efficiency of repair of damage induced by genotoxic therapies may be an important factor in the assessment of eligibility for different anticancer treatments, the outcomes of various treatments and the therapy-associated complications, including acute and delayed toxicity and acquired drug resistance. The second part of this paper analyses the currently available information about the possibilities of using experimentally obtained knowledge about individual repair capacity for the purposes of personalised medicine and healthcare.

WHAT'S YOUR POISON? IMPACT OF INDIVIDUAL REPAIR CAPACITY ON THE OUTCOMES OF GENOTOXIC THERAPIES IN CANCER. PART I - ROLE OF INDIVIDUAL REPAIR CAPACITY IN THE CONSTITUTION OF RISK FOR LATE-ONSET MULTIFACTORIAL DISEASE

ABSTRACT The capacity for repair of damage in DNA may vary between clinically healthy people and in patients with different diseases and conditions, contributing to the risk for development of late-onset multifactorial disease, eligibility for different therapies and various therapy-related complications. At present, the effects of individual variance in DNA repair capacity in human disease are best studied in cancer. The first part of this paper briefly reviews the history of the field and the currently available biomarkers of individual repair capacity associated with the risk for development of cancer and other late-onset multifactorial diseases and conditions.

p53—Guardian Angel and Archangel

ABSTRACT p53 is a master regulator of the cell cycle, capable of assessing the severity and the scope of damage to the cellular DNA, integrating the signals from the cell under stress and delivering the final decision about the destiny of the cell—undertaking repair activities; entering replicative senescence; inducing cell death; resorting to translesion transactions or altering the metabolism or the expression pattern of the cell. Proper functioning of p53 and its related pathways is essential in multicellular eukaryotes, with failures in the DNA-binding and transactivation properties of p53 usually resulting in cancer. Recent research on some common polymorphic variants of p53 that exhibit differential properties in their ability to induce cell cycle arrest or apoptosis indicate that p53 is not only the ‘guardian angel’ of the genome, as is commonly believed, keeping its integrity in check and disposing of damaged cells, but it is as well the ‘archangel’ that is responsible for cutting down the lifespan of the organism by the mechanism of ageing. One function can hardly exist without the other, and it is very individual as to whether carriership of one polymorphic form or another would be beneficial in the particular case, considering the general status of the patient and the specificities of the pathogenesis of the disease or condition in question. Age of the patient seems to be a major determining factor, as the differential pattern in the properties of p53 seems to become more pronounced as age advances.

Current state of the opportunities for derivation of germ-like cells from pluripotent stem cells: are you a man, or a mouse?

The concept of pluripotency as a prerogative of cells of early mammal embryos and cultured embryonic stem cells (ESC) has been invalidated with the advent of induced pluripotent stem cells. Later, it became clear that the ability to generate all cell types of the adult organism is also a questionable aspect of pluripotency, as there are cell types, such as germ cells, which are difficult to produce from pluripotent stem cells. Recently it has been proposed that there are at least two different states of pluripotency; namely, the naïve, or ground state, and the primed state, which may differ radically in terms of timeline of existence, signalling mechanisms, cell properties, capacity for differentiation into different cell types, etc. Germ-like male and female rodent cells have been successfully produced in vitro from ESC and induced pluripotent stem cells. The attempts to derive primate primordial germ cells (PGC) and germ cells in vitro from pluripotent stem cells, however, still have a low success rate, especially with the female germline. The paper reviews the properties of rodent and primate ESC with regard to their capacity for differentiation in vitro to germ-like cells, outlining the possible caveats to derivation of PGC and germ cells from primate and human pluripotent cells.

Measuring Telomere Length—From Ends to Means

ABSTRACT Telomeres are ribonucleoproteid complexes capping the ends of linear genomes and protecting them from attrition and fusion. The rate of telomere shortening is related to cellular aging and a loss of telomere length is observed in a significant proportion of human diseases and conditions. Telomerase activity may serve as a useful marker for capacity for self-renewal and potential for differentiation in stem cells. The present paper reviews the present-day methods for measuring telomere length in cell populations and/or assessment of telomerase activity—Southern hybridisation, flow cytometry/Flow FISH, real-time PCR and some less popular methods such as TRAP analysis and STELA, assessing the advantages and weaknesses of each method and outlining the possible fields of application.

Rapid and Efficient Method for Production of T4 Endonuclease V by Heterologous Expression in E.Coli

ABSTRACT T4 endonuclease V is specific to cyclobutane-pyrimidine dimers produced by UV-irradiation. When applied topically in mammals, it induces strand breaks in the altered DNA, thus triggering the cellular DNA repair system. Application of T4 endo V-containing preparations may ameliorate sun-induced damage in healthy persons as well as in patients defective in DNA repair capacity. We propose a rapid and efficient method for production of T4 endonuclease V without the need for phage inoculation of bacteria, thus allowing for easier and cost-effective manufacturing of T4endo V of the purity required by the GMP standards for medicinal preparations for use in humans.

Genetic Bases for Predisposition to Common Multifactorial Disease in Man. Part II

ABSTRACT Common diseases in man often have a genetic component. The risk for a carrier of alleles predisposing to some type of multifactorial disease to develop the disease is greater than it is for a non-carrier of the allele and proportional to the weight of the genetic component in the etiogenesis of the disease. Knowledge of carriership of high-risk alleles allows the individual to make informed choices about lifestyle and occupation and to ensure detection and timely intervention early in the pathological process. Also, specific features of the genetic background may play a major role when choosing between different therapeutic modalities. This paper presents the second part of an overview of the state of the art in the field of risk assessment for predisposition to human disease. A selection of genetic markers for disease predisposition is listed, including markers for inherited cardiac pathology, bone health, cancer-proneness and for traits related to individual eligibility for certain therapies. The role of genetic background is also discussed in aspect not related to disease but, rather, to physical fitness in healthy individuals.

Brown Trout-Salmon Hybrids in Bulgarian Rivers are not a Red Herring

ABSTRACT Brown trout (Salmo trutta fario) is a popular object of recreational fishing in Bulgaria and throughout Europe. Free-living (‘wild’) populations of brown trout are seen in many cold water rivers, and restocking of artificial as well natural water basins is carried out routinely. Genetic analysis for a microsatellite marker common for several salmonid species but discriminative in regards to species affiliation shows that allele lengths uncharacteristic of brown trout but typical of Atlantic salmon may be observed in Bulgarian ‘wild’ populations of brown trout. It is possible that a subpopulation containing interspecies hybrids with Atlantic salmon exists in the Bulgarian water basins populated with brown trout. Since brown trout-salmon hybrids have been shown to be viable and fertile, the possibility for future interspecies introgression cannot be ruled out. The biodiversity of Bulgarian natural populations of salmonid fishes may benefit from a more finely tailored stocking strategy.