Fine structure of translocation breakpoints within the major breakpoint region in BCR-ABL1-positive leukemias.

The chromosomal translocation t(9;22)(q34;q22), with expression of the BCR-ABL1 fusion gene is the cytogenetic and molecular hallmark of chronic myeloid leukemia (CML) and a subset of acute lymphoblastic leukemia (ALL). Basically two types of BCR-ABL1 chimeric mRNA transcripts have been observed: (1) e13a2/e14a2 transcripts in CML and ALL, resulting from chromosomal breaks in the major breakpoint cluster region (M-bcr) of the BCR gene and (2) e1a2 transcripts in ALL resulting from breaks in the minor breakpoint cluster region (m-bcr) of the BCR gene. To gain a better understanding of this molecular alteration, we developed a long-distance inverse PCR (LDI PCR) method for M-bcr breakpoint identification in BCR-ABL1-positive cases and were thus able to identify the chromosomal breakpoints within the M-bcr in 62 BCR-ABL1-positive samples. The corresponding reciprocal breakpoints were identified and molecularly characterized in 45 of these cases. In 2 samples, the breaks were located 5' to the ABL1 locus and in one case, the der(9) break was identified on 9q34.13 several hundred kB 3' telomeric to ABL1. The analysis of breaks revealed no significant clustering and no association with repetitive elements (Alu, L1, L2) or recombination signal sequence sites. The established LDI PCR permits fast, relatively easy and unbiased identification of breakpoints in the M-bcr region of BCR and also enables the molecular analysis of more complex translocations with breakpoints outside the ABL1 gene locus or other BCR fusion genes.

Immobilization of an anticoagulant benzamidine derivative: effect of spacer arms and carrier hydrophobicity on thrombin binding.

Prevention of blood coagulation is very often a prerequisite for successful medical devices. For that purpose, passivation of the key coagulation enzyme thrombin through the derivatization of the material's surface with an amidine-based molecule has been found to be promising. To further enhance the efficiency of this approach, thin layers of maleic anhydride copolymers offering different physico-chemical characteristics were tethered with carboxyl terminated polyethylene glycol to covalently immobilize a benzamidine-type derivative. The free carboxyl surface groups produced by the attachment of polyethylene glycol (PEG) were quantified by Ag(+) labeling and subsequent XPS detection. The film thickness as well as the carboxyl group content were found to be clearly dependent on the copolymer hydrophobicity and the nature of the PEG molecule. For the assessment of the anchorage of the thrombin to the benzamidine-derivative functionalized surfaces, the substrates were immersed in a buffered thrombin solution and the enzyme adsorption was studied using immunostaining/confocal laser scanning microscopy. Higher degrees of thrombin binding were observed for substrates configured with the hydrophilic compared to the more hydrophobic copolymer. Moreover, surface-bound spacers based on alpha,omega-heterobifunctional PEG amino acids (alphaAm,omegaAc-PEG) also enhanced the benzamidine surface density in comparison to homofunctional PEG diacids (alphaAc,omegaAc-PEG) because of a lower degree of carboxyl inactivation due to PEG 'bridging'. Altogether, the choice of copolymer coatings and the type of PEG spacers were demonstrated to enhance the efficiency of the thrombin scavenging by the covalently immobilized coagulation inhibitor.