[New perspective in the treatment of chronic myeloid leukemia? gene silencing therapy]. / Új perspektíva a krónikus mieloid leukémia kezelésében? géncsendesítéses terápia.

Chronic myeloid leukemia is an incurable white blood cell disease with slow progression which affects myeloid stem cells. In the course of chromosome 22 shortening a fusion oncogene arises whose product, a Bcr-Abl oncoprotein, is a continuously expressed tyrosine kinase protein. Beside the opportunity of chemotherapy, stem cell therapy and interferon-a therapy, the application of tyrosine kinase inhibitors also became widespread in the treatment of the disease. Patients bearing the T315I point mutation, however, show resistance against all tyrosine kinase inhibitors, which can be managed by dose escalation or the combination of therapies. The discovery of RNA interference or gene silencing put the therapeutic opportunity of CML in new light. The in vitro application of anti-bcr-abl siRNA showed promising results in the causal treatment of the disease, feasible for identification of new genes associated to the disease, but we do not have sufficient evidence for the safety and efficacy of this method in human therapy.

Visualization of mitochondrial membrane potential and reactive oxygen species via double staining.

Quantitative and qualitative analysis of both generated reactive oxygen species (ROS) and mitochondrial membrane potential cannot be detected simultaneously. We here introduce a simple, new double staining method. We have successfully used this for several years utilizing cerium for ROS detection and JC-1 staining to assess the mitochondrial membrane potential. The resultant signals on laser confocal images can be localized in the same cells and can easily quantify them. We used a confocal microscope along with our new, combined staining method to both visualize mitochondrial membrane potential (DeltaPsim) and imaged ROS. These were quantified by JC-1 staining and by cerium ions with reflectance in a method modified in our laboratory. To test this double labeling technique we used PC 12 cells subjected to 1 h hypoxia and 24h re-oxygenization. We are able to produce a quantitative analysis of red/green signals of JC-1 that reflected the energy state of the cells. Cerium reflectance correlates with the amount of ROS release in the same cells. Significant differences have been calculated after hypoxia and re-oxygenation in both modality of the cell staining. The red/green ratio was 18.2+/-9.3 (n=30) in normoxic cells versus 1.65+/-0.9 (n=30) in the hypoxia/re-oxygenation group (p<0.05). In the same randomly selected cells the average cerium reflectance signal intensity was 2.5+/-1.2 (n=30) in the control group while 5.8+/-3.1 (n=30) in the hypoxia/re-oxygenation group (p<0.05). This assay, by characterizing hypoxic injury and re-oxygenization induced ROS production, offers a qualitative and quantitative method to detect the consequences of oxidative stress in experimental conditions and to detect different cell protective strategies.