Induction of erythroid differentiation and increased globin mRNA production with furocoumarins and their photoproducts

Differentiation-therapy is an important approach in the treatment of cancer, as in the case of erythroid induction in chronic myelogenous leukemia (CML). Moreover, an important therapeutic strategy for treating some hematological diseases, such as -thalassemia and sickle-cell anemia (SCA) could be the use of drugs able to induce erythroid differentiation and fetal hemoglobin (HbF) accumulation. It is widely accepted that the increased production of HbF can reduce the clinical symptoms and the frequency of transfusions. An important class of erythroid differentiating compounds and HbF inducers is composed by DNA-binding chemotherapeutics: however, they are not used in most instances considering their possible devastating side effects. In this context, we approached the study of erythrodifferentiating properties of furocoumarins. In fact, upon UV-A irradiation, they are able to covalently bind DNA. Thus, the erythrodifferentiation activity of some linear and angular furocoumarins was evaluated in the experimental K562 cellular model system. Quantitative real-time RT-PCR assay was employed to evaluate the accumulation of different globin mRNAs. The results demonstrated that both linear and angular furocoumarins are strong inducers of erythroid differentiation of K562 cells. The differentiating activity of these compounds in the presence of UV-A irradiation was associated with a dramatic induction of accumulation of the -like -globin and -globin mRNA and the -like -globin and -globin mRNA sequences. Of particular interest is our finding that erythroid induction and accumulation of -globin mRNA can be also obtained with psoralen plus UVA induced photolysis products. It will be of interest to identify and characterize the active products involved. From a preliminary screening, we selected the most active compounds and investigated the role of DNA photodamage in their erythroid inducing activity and mechanism of action. Moreover, some cytofluorimetric experiments were carried out to better study cell cycle modifications and the mitochondrial involvement. A further development of the work was carried out studying the erythroid differentiation of photolysis products of these molecules. The most interesting photoproducts mixtures were those obtained with 5,5’-DMP (5,5'-Dimethylpsoralen). The efficiency of this photoproducts in inducing increase of globin mRNA content was dramatic and much higher than those exhibited by other inducers of K562 erythroid differentiation, such as cytosine arabinoside, butyric acid, mithramyci