Bis-epoxyethyl derivatives of distamycin A modified on the amidino moiety: Induction of production of fetal hemoglobin in human erythroid precursor cells

Abstract

Abstract.Derivatives of distamycin A modified at the Cterminal amidine moiety and tethered to bis-epoxyethyl moieties at the N-terminal position were tested for their ability to induce erythroid differentiation in the human erythroleukemic cell line K562. None of the compounds without bis-epoxyethyl moiety were active. A comparison of the biological activity of diepoxy compounds containing different non-basic amidine-modified moieties, showed low activity of amidoxime, carbamoyl and N-methyl carbamoyl derivatives as differentiation agents. In contrast, a cyanamidine derivative, compound 3, was able to induce erythroid differentiation of K562 cells. In addition, the cyanamidine derivative 3 was able to induce HbF accumulation following treatment of cultures of erythroid precursor cells isolated from the peripheral blood of normal subjects. IntroductionThe identification and characterization of potential therapeutic agents for the treatment of ß-thalassemia and sickle cell anemia is based on the pharmacologically mediated regulation of the expression of human Á-globin genes (1-8). It is well established that an increased production of fetal hemoglobin (HbF, · 2 Á 2 ) leads to a significant improvement of the clinical status of the patients (4,5,7). Therefore, many published experiments were designed to find hormones, cytotoxic agents, hemopoietic cytokines and short fatty acids as agents able to increase HbF levels in humans (1-3,9-11).In this respect, DNA-binding drugs are very interesting, since we reported that mithramycin, cis-platinum and tallimustine analogs are potent inducers of erythroid differentiation (12-14). The same compounds have been demonstrated to increase HbF production in human erythroid precursor cells obtained from peripheral blood of normal subjects and thalassemic patients (9). In particular, we found that the distamycin analog tallimustine and some related compounds are powerful inducers of differentiation and Á-globin mRNA accumulation in normal human erythroid progenitors (10).In this study, we report on the biological characterization of potential HbF inducers of the hybrid molecules 3-6 that include the amidine-modified tripeptide tris-N-methyl-pyrrolecarboxamide distamycin A, which contains two electrophile epoxydic functions on the amino end. In the bis-epoxyethyldistamycin A hybrids, the amidino moiety has been replaced by various non-basic groups of a different electronic nature, lipophilicity and bulk, such as cyanamidine (compound 3), amidoxime (compound 4), carbamoyl (compound 5) and Nmethyl carbamoyl (compound 6).As was previously reported, the synthesis of amidinomodified analogs provides a number of advantages (15-18). First, they are not hygroscopic and are easy to handle. Moreover, these derivatives are uncharged. Thus, products and intermediates can be readily purified by column chromatography and recrystallized.These compounds were investigated for potential erythrodifferentiation ability, in order to verify whether some of them were able to increase Á-globin gene express...