Exhaled breath condensate as a source of biomarkers for lung carcinomas. A focus on genetic and epigenetic markers-A mini-review.

Lung carcinoma is one of the most common causes of cancer-related mortality worldwide. It is an aggressive tumor, often diagnosed at an advanced stage when treatment options are limited. Currently, the importance of detection and assessment of various genetic alterations in cancer is recognized as they can serve as very helpful markers in early diagnosis and follow-up of treatment regimens. Recently, several therapeutically important genetic markers have been identified. One major problem is that tumor tissue specimens used to assay these genetic biomarkers are not always available, especially in the early stages of the disease. Therefore, exhaled breath condensates (EBC) could represent a good non-invasive source to allow the evaluation of these important genetic markers; these could help in the diagnosis, follow-up of the disease and/or assessment of treatment efficacy. The key aims of this review are first to describe the origin and constituents of EBC, as well as the different methodological procedures used in studying EBC biomarkers, and second, to document genetic and epigenetic markers that have been analyzed in EBC from lung cancer patients and to estimate their diagnostic and prognostic value. © 2016 Wiley Periodicals, Inc.

Driver gene mutations of non-small-cell lung cancer are rare in primary carcinoids of the lung: NGS study by ion Torrent.

Lung carcinoids are rare neuroendocrine tumors of the lung. Very little is known about the genetic background of these tumors. We applied Ion Torrent Ampliseq next-generation technology to study hotspot mutations of 22 lung cancer-related genes from typical and atypical lung carcinoid tumors. DNA isolated from 25 formalin-fixed, paraffin-embedded carcinoid tumors were amplified to prepare barcoded libraries covering 507 mutations included in 90 amplicons. The libraries were pooled, purified, enriched, and sequenced on ion personal genome machine. The sequences were aligned and checked for known and novel variations using Torrent Suite Software v.4.0.2. One out of 25 patients had mutations in the targeted regions sequenced. This patient had mutations in BRAF, SMAD4, PIK3CA, and KRAS. All these mutations were confirmed as somatic and are previously known mutations. In summary, mutations in genes commonly mutated in non-small-cell lung cancer are not common in lung carcinoids.

Evaluation of γ-H2AX foci distribution among different peripheral blood mononucleated cell subtypes.

INTRODUCTION: The detection of γ-H2AX foci in peripheral blood mononucleated cells (PBMCs) has been incorporated as an early assay for biological dosimetry. However, overdispersion in the γ-H2AX foci distribution is generally reported. In a previous study from our group, it was suggested that overdispersion could be caused by the fact that when evaluating PBMCs, different cell subtypes are analyzed, and that these could differ in their radiosensitivity. This would cause a mixture of different frequencies that would result in the overdispersion observed. OBJECTIVES: The objective of this study was to evaluate both the possible differences in the radiosensitivities of the different cell subtypes present in the PBMCs and to evaluate the distribution of γ-H2AX foci in each cell subtype. MATERIALS AND METHODS: Peripheral blood samples from three healthy donors were obtained and total PBMCs, and CD3+, CD4+, CD8+, CD19+, and CD56+ cells were separated. Cells were irradiated with 1 and 2 Gy and incubated at 37 °C for 1, 2, 4, and 24 h. Sham-irradiated cells were also analyzed. γ-H2AX foci were detected after immunofluorescence staining and analyzed automatically using a Metafer Scanning System. For each condition, 250 nuclei were considered. RESULTS: When the results from each donor were compared, no observable significant differences between donors were observed. When the different cell subtypes were compared, CD8+ cells showed the highest mean of γ-H2AX foci in all post-irradiation time points. The cell type that showed the lowest γ-H2AX foci frequency was CD56+. The frequencies observed in CD4+ and CD19+ cells fluctuated between CD8+ and CD56+ without any clear pattern. For all cell types evaluated, and at all post-irradiation times, overdispersion in γ-H2AX foci distribution was significant. Independent of the cell type evaluated the value of the variance was four times greater than that of the mean. CONCLUSION: Although different PBMC subsets studied showed different radiation sensitivity, these differences did not explain the overdispersion observed in the γ-H2AX foci distribution after exposure to IR.

Dysfunction of the Salivary and Lacrimal Glands After Radioiodine Therapy for Thyroid Cancer: Results of the START Study After 6-Months of Follow-Up.

Background: Understanding of changes in salivary and lacrimal gland functions after radioactive iodine therapy (131I-therapy) remains limited, and, to date, no studies have evaluated dose-response relationships between absorbed dose from 131I-therapy and dysfunctions of these glands. This study investigates salivary/lacrimal dysfunctions in differentiated thyroid cancer (DTC) patients six months after 131I-therapy, identifies 131I-therapy-related risk factors for salivary/lacrimal dysfunctions, and assesses the relationships between 131I-therapy radiation dose and these dysfunctions. Methods: A cohort study was conducted involving 136 DTC patients treated by 131I-therapy of whom 44 and 92 patients received 1.1 and 3.7 GBq, respectively. Absorbed dose to the salivary glands was estimated using a dosimetric reconstruction method based on thermoluminescent dosimeter measurements. Salivary and lacrimal functions were assessed at baseline (T0, i.e., immediately before 131I-therapy) and six months later (T6) using validated questionnaires and salivary samplings, with and without stimulation of the salivary glands. Statistical analyses included descriptive analyses and random-effects multivariate logistic and linear regressions. Results: There was no difference between T0 and T6 in the level of parotid gland pain, nor was there difference in the number of patients with hyposalivation, but there were significantly more patients with dry mouth sensation and dry eyes after therapy compared with baseline. Age, menopause, depression and anxiety symptoms, history of systemic disease, and not taking painkillers in the past three months were found to be significantly associated with salivary or lacrimal disorders. Significant associations were found between 131I-exposure and salivary disorders adjusted on the previous variables: for example, per 1-Gy increase in mean dose to the salivary glands, odds ratio = 1.43 [CI 1.02 to 2.04] for dry mouth sensation, ß = -0.08 [CI -0.12 to -0.02] mL/min for stimulated saliva flow, and ß = 1.07 [CI 0.42 to 1.71] mmol/L for salivary potassium concentration. Conclusions: This study brings new knowledge on the relationship between the absorbed dose to the salivary glands from 131I-therapy and salivary/lacrimal dysfunctions in DTC patients six months after 131I-therapy. Despite the findings of some dysfunctions, the results do not show any obvious clinical disorders after the 131I-therapy. Nevertheless, this study raises awareness of the risk factors for salivary disorders, and calls for longer follow-up. Clinical Trials Registration: Number NCT04876287 on the public website (ClinicalTrials.gov).

Molecular Biomarkers in Cancer.

Molecular cancer biomarkers are any measurable molecular indicator of risk of cancer, occurrence of cancer, or patient outcome. They may include germline or somatic genetic variants, epigenetic signatures, transcriptional changes, and proteomic signatures. These indicators are based on biomolecules, such as nucleic acids and proteins, that can be detected in samples obtained from tissues through tumor biopsy or, more easily and non-invasively, from blood (or serum or plasma), saliva, buccal swabs, stool, urine, etc. Detection technologies have advanced tremendously over the last decades, including techniques such as next-generation sequencing, nanotechnology, or methods to study circulating tumor DNA/RNA or exosomes. Clinical applications of biomarkers are extensive. They can be used as tools for cancer risk assessment, screening and early detection of cancer, accurate diagnosis, patient prognosis, prediction of response to therapy, and cancer surveillance and monitoring response. Therefore, they can help to optimize making decisions in clinical practice. Moreover, precision oncology is needed for newly developed targeted therapies, as they are functional only in patients with specific cancer genetic mutations, and biomarkers are the tools used for the identification of these subsets of patients. Improvement in the field of cancer biomarkers is, however, needed to overcome the scientific challenge of developing new biomarkers with greater sensitivity, specificity, and positive predictive value.

Differential Radiosensitizing Effect of 50 nm Gold Nanoparticles in Two Cancer Cell Lines.

Radiation therapy is widely used as an anti-neoplastic treatment despite the adverse effects it can cause in non-tumoral tissues. Radiosensitizing agents, which can increase the effect of radiation in tumor cells, such as gold nanoparticles (GNPs), have been described. To evaluate the radiosensitizing effect of 50 nm GNPs, we carried out a series of studies in two neoplastic cell lines, Caco2 (colon adenocarcinoma) and SKBR3 (breast adenocarcinoma), qualitatively evaluating the internalization of the particles, determining with immunofluorescence the number of γ-H2AX foci after irradiation with ionizing radiation (3 Gy) and evaluating the viability rate of both cell lines after treatment by means of an MTT assay. Nanoparticle internalization varied between cell lines, though they both showed higher internalization degrees for functionalized GNPs. The γ-H2AX foci counts for the different times analyzed showed remarkable differences between cell lines, although they were always significantly higher for functionalized GNPs in both lines. Regarding cell viability, in most cases a statistically significant decreasing tendency was observed when treated with GNPs, especially those that were functionalized. Our results led us to conclude that, while 50 nm GNPs induce a clear radiosensitizing effect, it is highly difficult to describe the magnitude of this effect as universal because of the heterogeneity found between cell lines.

Establishment and validation of surface model for biodosimetry based on γ-H2AX foci detection.

INTRODUCTION: In the event of a radiation accident detecting γ-H2AX foci is being accepted as fast method for triage and dose assessment. However, due to their disappearance kinetics, published calibrations have been constructed at specific post-irradiation times. OBJECTIVES: To develop a surface, or tridimensional, model to estimate doses at times not included in the calibration analysis, and to validate it. MATERIALS AND METHODS: Calibration data was obtained irradiating peripheral mononucleated cells from one donor with radiation doses ranging from 0 to 3 Gy, and γ -H2AX foci were detected microscopically using a semi-automatic method, at different post-irradiation times from 0.5 to 24 h. For validation, in addition to the above-mentioned donor, blood samples from another donor were also used. Validation was done within the range of doses and post-irradiation times used in the calibration. RESULTS: The calibration data clearly shows that at each analyzed time, the γ-H2AX foci frequency increases as dose increases, and for each dose this frequency decreases with post-irradiation time. The γ-H2AX foci nucleus distribution was clearly overdispersed, for this reason to obtain bidimensional and tridimensional dose-effect relationships no probability distribution was assumed, and linear and non-linear least squares weighted regression was used. In the two validation exercises for most evaluated samples, the 95% confidence limits of the estimated dose were between ±0.5 Gy of the real dose. No major differences were observed between donors. CONCLUSION: In case of a suspected overexposure to radiation, the surface model here presented allows a correct dose estimation using γ-H2AX foci as biomarker. The advantage of this surface model is that it can be used at any post-irradiation time, in our model between 0.5 and 24 h.

Salivary Dysfunctions and Consequences After Radioiodine Treatment for Thyroid Cancer: Protocol for a Self-Controlled Study (START Study).

BACKGROUND: Following radioiodine (131I) therapy of differentiated thyroid cancer, the salivary glands may become inflamed, leading to dysfunctions and decreases in patients' nutritional status and quality of life. The incidence of these dysfunctions after 131I-therapy is poorly known, and no clinical or genetic factors have been identified to date to define at-risk patients, which would allow the delivered activity to be adapted to the expected risk of salivary dysfunctions. OBJECTIVE: The aims of this study are to estimate the incidence of salivary dysfunctions, and consequences on the quality of life and nutritional status for patients after 131I-therapy; to characterize at-risk patients of developing posttreatment dysfunctions using clinical, biomolecular, and biochemical factors; and to validate a dosimetric method to calculate the dose received at the salivary gland level for analyzing the dose-response relationship between absorbed doses to salivary glands and salivary dysfunctions. METHODS: This prospective study aims to include patients for whom 131I-therapy is indicated as part of the treatment for differentiated thyroid cancer in a Paris hospital (40 and 80 patients in the 1.1 GBq and 3.7 GBq groups, respectively). The follow-up is based on three scheduled visits: at inclusion (T0, immediately before 131I-therapy), and at 6 months (T6) and 18 months (T18) posttreatment. For each visit, questionnaires on salivary dysfunctions (validated French tool), quality of life (Hospital Anxiety and Depression scale, Medical Outcomes Study 36-Item Short Form Survey), and nutritional status (visual analog scale) are administered by a trained clinical research associate. At T0 and T6, saliva samples and individual measurements of the salivary flow, without and with salivary glands stimulation, are performed. External thermoluminescent dosimeters are positioned on the skin opposite the salivary glands and at the sternal fork immediately before 131I administration and removed after 5 days. From the doses recorded by the dosimeters, an estimation of the dose received at the salivary glands will be carried out using physical and computational phantoms. Genetic and epigenetic analyses will be performed to search for potential biomarkers of the predisposition to develop salivary dysfunctions after 131I-therapy. RESULTS: A total of 139 patients (99 women, 71.2%; mean age 47.4, SD 14.3 years) were enrolled in the study between September 2020 and April 2021 (45 and 94 patients in the 1.1 GBq and 3.7G Bq groups, respectively). T6 follow-up is complete and T18 follow-up is currently underway. Statistical analyses will assess the links between salivary dysfunctions and absorbed doses to the salivary glands, accounting for associated factors. Moreover, impacts on the patients' quality of life will be analyzed. CONCLUSIONS: To our knowledge, this study is the first to investigate the risk of salivary dysfunctions (using both objective and subjective indicators) in relation to organ (salivary glands) doses, based on individual dosimeter records and dose reconstructions. The results will allow the identification of patients at risk of salivary dysfunctions and will permit clinicians to propose a more adapted follow-up and/or countermeasures to adverse effects. TRIAL REGISTRATION: ClinicalTrials.gov NCT04876287; https://clinicaltrials.gov/ct2/show/NCT04876287. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/35565.

RSK4 inhibition results in bypass of stress-induced and oncogene-induced senescence.

p90 Ribosomal S6 kinase (RSK) 4 is a serine-threonine kinase that belongs to the p90RSK family. RSK4 has been proposed as a tumor suppressor gene, related with anti-invasive activity, inhibition of the RAS-mitogen-activated protein kinase (MAPK) pathway and induction of senescence. Despite the related findings, little is known about RSK4 effectors. In human tumors, RSK4 is downregulated even in some benign lesions, such as colon adenomas and breast papillomas, indicating that RSK4 inhibition could be an early event in cellular transformation. For cells to achieve immortality and transformation, it is believed that they must override senescence. In the present study, we found that when RSK4 is inhibited in vitro using short hairpin RNA technology, cells can bypass stress-induced senescence and oncogene-induced senescence: normal human fibroblasts grew following oxidative stress, induction of DNA damage and KRAS(V12) or BRAF(E600) overexpression. To investigate the RSK4 effectors, we used short hairpin RNA or inhibitor molecules against major senescence mediators. We found that RSK4-induced senescence is mediated through p21, but is independent of p16, p38MAPKs and induction of reactive oxygen species, delimiting RSK4 signaling. These data support the importance of RSK4 for regulating senescence and indicate that downregulation of this kinase could be an important element in facilitating cell transformation.

Identification of human specific gene duplications relative to other primates by array CGH and quantitative PCR.

In order to identify human lineage specific (HLS) copy number differences (CNDs) compared to other primates, we performed pair wise comparisons (human vs. chimpanzee, gorilla and orangutan) by using cDNA array comparative genomic hybridization (CGH). A set of 23 genes with HLS duplications were identified, as well as other lineage differences in gene copy number specific of chimpanzee, gorilla and orangutan. Each species has gained more copies of specific genes rather than losing gene copies. Eleven of the 23 genes have only been observed to have undergone HLS duplication in Fortna et al. (2004) and in the present study. Then, seven of these 11 genes were analyzed by quantitative PCR in chimpanzee, gorilla and orangutan, as well as in other six primate species (Hylobates lar, Cercopithecus aethiops, Papio hamadryas, Macaca mulatta, Lagothrix lagothricha, and Saimiri sciureus). Six genes confirmed array CGH data, and four of them appeared to have bona fide HLS duplications (ABCB10, E2F6, CDH12, and TDG genes). We propose that these gene duplications have a potential to contribute to specific human phenotypes.

Low dose ionizing radiation effects on the immune system.

Ionizing radiation interacts with the immune system in many ways with a multiplicity that mirrors the complexity of the immune system itself: namely the need to maintain a delicate balance between different compartments, cells and soluble factors that work collectively to protect, maintain, and restore tissue function in the face of severe challenges including radiation damage. The cytotoxic effects of high dose radiation are less relevant after low dose exposure, where subtle quantitative and functional effects predominate that may go unnoticed until late after exposure or after a second challenge reveals or exacerbates the effects. For example, low doses may permanently alter immune fitness and therefore accelerate immune senescence and pave the way for a wide spectrum of possible pathophysiological events, including early-onset of age-related degenerative disorders and cancer. By contrast, the so called low dose radiation therapy displays beneficial, anti-inflammatory and pain relieving properties in chronic inflammatory and degenerative diseases. In this review, epidemiological, clinical and experimental data regarding the effects of low-dose radiation on the homeostasis and functional integrity of immune cells will be discussed, as will be the role of immune-mediated mechanisms in the systemic manifestation of localized exposures such as inflammatory reactions. The central conclusion is that ionizing radiation fundamentally and durably reshapes the immune system. Further, the importance of discovery of immunological pathways for modifying radiation resilience amongst other research directions in this field is implied.

Chromosomal aberration dynamics through the cell cycle.

DNA double-strand breaks are the crucial lesions underlying the formation of chromosomal aberrations, their formation and kinetics have been extensively studied, although dynamics of the repair process has not been fully understood. By using a combination of different cytogenetic techniques to analyze cells in G0, G2 and M phase, in the present study we perform a follow up study of the dynamics of different radiation induced chromosomal aberrations. Data here presented show that in G0 phase chromosome fragments lacking telomere signals (incomplete chromosome elements, ICE) show a slow repair, but when repair occurs tend to reconstitute the original chromosomes, and those that do not repair seem to be selected by interphase cell death and cell cycle checkpoints. In contrast, complete chromosome aberrations, as dicentrics, show a very fast formation kinetics. Similar frequencies of dicentrics were observed in G0, G2 and M cells, indicating that this chromosome-type of aberration can progress through the cell cycle without negative selection. Our study reinforce the hypothesis that ICE are strongly negatively selected from G2 to M phase. However, the G2/M checkpoint seems to be not involved in this selection. The ICE frequencies observed after G2/M abrogation by caffeine are similar to the ones without abrogation, and clearly lower to the ones observed in G2.

4E-binding protein 1: a key molecular "funnel factor" in human cancer with clinical implications.

In an attempt to identify molecules that clearly reflect the oncogenic role of cell signaling pathways in human tumors, we propose a concept we term "funnel factor", a factor where several oncogenic signals converge and drive the proliferative signal downstream. In studies done in various tumor types, the expression of key cell signaling factors, including Her1 and Her2 growth factor receptors, as well as the RAS-RAF-mitogen-activated protein kinase and the phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathways was correlated with the associated clinicopathologic characteristics of these tumors. The downstream factors p70, S6, 4E-binding protein 1 (4E-BP1), and eukaryotic translation initiation factor 4E, which play a critical role in the control of protein synthesis, survival, and cell growth, were also analyzed. We found that phosphorylated 4E-BP1 (p-4E-BP1) expression in breast, ovary, and prostate tumors is associated with malignant progression and an adverse prognosis regardless of the upstream oncogenic alterations. Thus, p-4E-BP1 seems to act as a funnel factor for an essential oncogenic capability of tumor cells, self-sufficiency in growth signals, and could be a highly relevant molecular marker of malignant potential. Further investigation into this concept may identify additional funnel factors in the oncogenic pathways and provide potential therapeutic targets.

Polymorphisms in MDM2 and TP53 Genes and Risk of Developing Therapy-Related Myeloid Neoplasms.

One of the most severe complications after successful cancer therapy is the development of therapy-related myeloid neoplasms (t-MN). Constitutional genetic variation is likely to impact on t-MN risk. We aimed to evaluate if polymorphisms in the p53 pathway can be useful for predicting t-MN susceptibility. First, an association study revealed that the Pro variant of the TP53 Arg72Pro polymorphism and the G allele of the MDM2 SNP309 were associated with t-MN risk. The Arg variant of TP53 is more efficient at inducing apoptosis, whereas the Pro variant is a more potent inductor of cell cycle arrest and DNA repair. As regards MDM2 SNP309, the G allele is associated with attenuation of the p53 apoptotic response. Second, to evaluate the biological effect of the TP53 polymorphism, we established Jurkat isogenic cell lines expressing p53Arg or p53Pro. Jurkat p53Arg cells presented higher DNA damage and higher apoptotic potential than p53Pro cells, after treatment with chemotherapy agents. Only p53Pro cells presented t(15;17) translocation and del(5q). We suggest that failure to repair DNA lesions in p53Arg cells would lead them to apoptosis, whereas some p53Pro cells, prone to cell cycle arrest and DNA repair, could undergo misrepair, generating chromosomal abnormalities typical of t-MN.

Genomic imbalances in Schistosoma-associated and non-Schistosoma-associated bladder carcinoma. An array comparative genomic hybridization analysis.

Carcinoma of the urinary bladder is the most common malignancy in many tropical and subtropical countries due to endemic infection by Schistosoma hematobium (bilharzia). In the current study, we performed a high-resolution analysis of gene copy number amplifications using array comparative genomic hybridization to compare DNA copy number changes in pools of Schistosoma-associated (SA) and non-Schistosoma-associated (NSA) bladder cancer (BC). Many DNA copy number changes were detected in all studies, with multiple gains and losses of genetic material. The most frequent alterations were gains on 5p15.2 approximately p15.33, 8q13.1, and 11q13, and losses on 8p21.3 approximately p22 and 22q13. Even when SA pools showed no Schistosoma-specific gene copy number profiling as compared to NSA pools, some genes seemed to be gained (ELN on 7q11.23) and some lost (PRKAG3 on 2q35 and PRDM6 on 5q23.2) in SA-SCC. The following genes were gained in all histopathologic categories: SRC (20q11.23), CEBPB (20q13.13), and GPR9 (Xq13.1). Our study did not provide clear evidence of differences in carcinogenesis of SA-BC and NSA-BC.

Immune response in mice and cattle after immunization with a Boophilus microplus DNA vaccine containing bm86 gene.

Plasmid pBMC2 encoding antigen Bm86 from a Colombian strain of cattle tick Boophilus microplus, was used for DNA-mediated immunization of BALB/c mice, employing doses of 10 and 50microg, delivered by intradermic and intramuscular routes. Anti-Bm86 antibody levels were significantly higher compared to control mice treated with PBS. In the evaluation of immunoglobulin isotypes, significant levels of IgG2a and IgG2b were observed in mice immunized with 50microg of pBMC2. Measurement of interleukine (IL) levels (IL-4, IL-5, IL-12(p40)) and interferon-gamma (IFN-gamma) in the sera of mice immunized with pBMC2 indicated high levels of IL-4 and IL-5, although there were also significant levels of IFN-gamma. Mice immunized with pBMC2 showed antigen-specific stimulation of splenocytes according to the incorporation of bromodeoxyuridine and IFN-gamma secretion. In all trials, mice injected intramuscularly with 50microg of pBMC2 presented the highest immune response. Moreover, cattle immunized with this DNA vaccine showed antibody production significantly different to the negative control. In conclusion, these results suggest the potential of DNA immunization with pBMC2 to induce humoral and cellular immune responses against B. microplus.

Long-lasting effects of a Bacillus thuringiensis serovar israelensis experimental tablet formulation for Aedes aegypti (Diptera: Culicidae) control.

Dengue is a growing public health problem in many tropical and subtropical countries worldwide. At present, the only method of controlling or preventing the disease is to eliminate its vector, Aedes aegypti (L.) (Diptera: Culicidae). In the current study, an experimental larvicide tablet formulation XL-47 based on Bacillus thuringiensis serovar israelensis (Bti) and containing 4.8% of technical powder was developed. This formulation was evaluated against Ae. aegypti in three different sets of experiments, under field-simulated conditions: two experiments were indoors and under partial sunlight exposure and one experiment was outdoors with sunlight exposure. Larvae were added throughout the experiment two times per week, and the residual larvicidal activity was recorded daily. Pupal formation was reduced in the containers with Bti by > 80% in relation to the containers without treatment for 12 wk; to our knowledge, this is the longest period of control reported for a Bti tablet formulation outdoors under sunlight exposure. Moreover, samples from the top, middle, and bottom of the water column were collected to perform bacterial plate counts and toxicity assays. The Bti population and the active ingredient of the tablet formulation remained mainly at the bottom of the containers and mosquito larvae reached the formulation by diving and shredding the tablet's material. In conclusion, the experimental tablet formulation XL-47 showed an inhibition of pupal formation that lasted for long periods under sunlight exposure.

Differences in DNA Repair Capacity, Cell Death and Transcriptional Response after Irradiation between a Radiosensitive and a Radioresistant Cell Line.

Normal tissue toxicity after radiotherapy shows variability between patients, indicating inter-individual differences in radiosensitivity. Genetic variation probably contributes to these differences. The aim of the present study was to determine if two cell lines, one radiosensitive (RS) and another radioresistant (RR), showed differences in DNA repair capacity, cell viability, cell cycle progression and, in turn, if this response could be characterised by a differential gene expression profile at different post-irradiation times. After irradiation, the RS cell line showed a slower rate of γ-H2AX foci disappearance, a higher frequency of incomplete chromosomal aberrations, a reduced cell viability and a longer disturbance of the cell cycle when compared to the RR cell line. Moreover, a greater and prolonged transcriptional response after irradiation was induced in the RS cell line. Functional analysis showed that 24 h after irradiation genes involved in "DNA damage response", "direct p53 effectors" and apoptosis were still differentially up-regulated in the RS cell line but not in the RR cell line. The two cell lines showed different response to IR and can be distinguished with cell-based assays and differential gene expression analysis. The results emphasise the importance to identify biomarkers of radiosensitivity for tailoring individualized radiotherapy protocols.