Wolfango Horn

Gene Expression Changes in Medical Workers Exposed to Radiation

Abstract The use of nuclear resources for medical purposes causes considerable concern about occupational exposure. Nevertheless, little information is available regarding the effects of low-dose irradiations protracted over time. We used oligomicroarrays to identify the genes that are transcriptionally regulated by persistent exposure to extremely low doses of ionizing radiation in 28 exposed professionals (mean cumulative effective dose ± SD, 19 ± 38 mSv) compared with a matched sample of nonexposed subjects. We identified 256 modulated genes from peripheral blood mononuclear cells profiles, and the main biological processes we found were DNA packaging and mitochondrial electron transport NADH to ubiquinone. Next we investigated whether a different pattern existed when only 22 exposed subjects with accumulated doses >2.5 mSv, a threshold corresponding to the natural background radiation in Italy per year, and mean equal to 25 ± 41 mSv were used. In addition to DNA packaging and NADH dehydrogenase function, the analysis of the higher-exposed subgroup revealed a significant modulation of ion homeostasis and programmed cell death as well. The changes in gene expression that we found suggest different mechanisms from those involved in high-dose studies that may help to define new biomarkers of radiation exposure for accumulated doses below 25 mSv.

Gene expression time-series analysis of Camptothecin effects in U87-MG and DBTRG-05 glioblastoma cell lines

BackgroundThe clinical efficacy of camptothecin (CPT), a drug specifically targeting topoisomerase I (TopoI), is under evaluation for the treatment of malignant gliomas. Due to the high unresponsiveness of these tumours to chemotherapy, it would be very important to study the signalling network that drives camptothecin outcome in this type of cancer cells. To address this issue, we had previously compared the expression profile of human U87-MG glioblastoma cells with that of a CPT-resistant counterpart, giving evidence that the development of a robust inflammatory response was the main transcriptional effect associated with CPT resistance.Here we report time-related changes and cell line specific patterns of gene expression after CPT treatment by using two p53 wild-type glioblastoma cell lines, U87-MG and DBTRG-05, with different sensitivities to TopoI inhibition.ResultsFirst, we demonstrated that CPT treatment brings the two cell lines to completely different outcomes: accelerated senescence in U87-MG and apoptosis in DBTRG-05 cells. Then, to understand the different susceptibility to CPT, we used oligo-microarray to identify the genes whose expression was regulated during a time-course treatment, ranging from 2 h to 72 h. The statistical analysis of microarray data by MAANOVA (MicroArray ANalysis Of VAriance) showed much less modulated genes in apoptotic DBTRG-05 cells (155) with respect to the senescent U87-MG cells (3168), where the number of down-regulated genes largely exceeded that of the up-regulated ones (80% vs. 20%). Despite this great difference, the two data-sets showed a large overlapping (60% circa) mainly due to the expression of early stress responsive genes. The use of High-Throughput GoMINER and EASE tools, for functional analysis of significantly enriched GO terms, highlighted common cellular processes and showed that U87-MG and DBTRG-05 cells shared many GO terms, which are related to the down-regulation of cell cycle and mitosis and to the up-regulation of cell growth inhibition and DNA damage.Furthermore, the down-regulation of MYC and DP1 genes, which act as key transcription factors in cell growth control, together with the inhibition of BUB1, BUB3 and MAD2 mRNAs, which are known to be involved in the spindle checkpoint pathway, were specifically associated with the execution of senescence in U87-MG cells and addressed as critical factors that could drive the choice between different CPT-inducible effectors programs. In U87-MG cells we also found inflammation response and IL1-beta induction, as late transcriptional effects of Topo I treatment but these changes were only partially involved in the senescence development, as shown by IL1-beta gene silencing.ConclusionBy comparing the transcription profile of two glioblastoma cell lines treated with camptothecin, we were able to identify the common cellular pathways activated upon Topo I inhibition. Moreover, our results helped in identifying some key genes whose expression seemed to be associated with the execution of senescence or apoptosis in U87-MG and DBTRG-05 cells, respectively.

1,2-Dibromoethane as an Initiating Agent for Cell Transformation

The two‐stage transformation assay increases the sensitivity of cells to chemicals and permits detection of carcinogens acting as initiating agents. 1,2‐Dibromoethane, a representative halogenated aliphatic, has been tested in the two‐stage BALB/c 3T3 cells transformation test at dosages from 16 μM to 128 μM. This dose range is much lower than those previously found efficient in transforming BALB/c 3T3 cells. Apart from the lowest dose, which induced borderline effects, all the other assayed dosages appeared to induce heritable changes in the traget cells. The initiated cells were revealed as fully transformed foci both in the combination with a chronic promoting treatment and also by allowing cells to perform more rounds of cell replication. The results clearly show that 1,2‐dibromo‐ethane can act as an initiator of cell transformation.