V(D)J targeting mistakes occur at low frequency in acute lymphoblastic leukemia.

Translocations of proto-oncogenes to the B-cell or T-cell antigen receptor loci in acute T- or B-cell leukemia and lymphoma have been, in most cases, accredited to V(D)J or switch recombination depending on the location of the breakpoint at the receptor locus. Only in rare instances, the reports take into account mechanistic characteristics of the translocation mechanism. To assess the functional ability of several sites implicated in supposedly V(D)J-mediated translocations, we tested five sites at four proto-oncogene loci in an ex vivo recombination substrate assay for their potential to act as direct target for V(D)J recombination. Our results show that the LMO2/RBTN2/TTG2 site and one LCK/P56 site readily engage in recombination with a genuine TCR element with the majority of breakpoint junctions showing the characteristics of V(D)J recombination, which strongly supports the involvement of this mechanism in the pathogenesis of the corresponding translocations in vivo. The site at the TLX1/HOX11 locus yielded 0.8% V(D)J-specific junctions. Sites at the LCK/P56 and TCF3/E2A proto-oncogenes resulted in exclusively unspecific breakpoints scattered over part of or the entire proto-oncogene region tested, marking them as unlikely V(D)J recombination targets. Our data suggest that, while being a potentially dangerous mechanism due to the introduction of DNA breaks, V(D)J recombination is a tightly controlled mechanism allowing for only few direct mistakes.

Modulating role of alcohol and acetaldehyde on neutrophil and monocyte functions in vitro.

Moderate alcohol intake lowers coronary heart disease risk. Because polymorphonuclear neutrophils (PMN) and monocytes (Mo) play a role in atherosclerotic plaque destabilization we investigated in vitro effects of clinically relevant concentrations of ethanol (0.05, 0.125, 0.25, and 0.5%) and its metabolite acetaldehyde (0.0625, 0.125, and 0.5 mM) on human PMN and Mo phagocytic functions. PMN and Mo from healthy volunteers were separated and purified according standard methods and the following parameters were determined: phagocytic activity (percent of phagocytes with at least one ingested particle), ingestion index (number of ingested particles per 100 phagocytic cells), and intracellular killing (percent of dead ingested particles per 100 phagocytes) using acridine orange method and living yeast cells as targets. Reactive oxygen species (ROS) formation of ethanol-treated PMN and Mo was evaluated using 2,7-dichlorofluorescin method and results were expressed as percent of fluorescence-positive cells. Ethanol and acetaldehyde significantly reduced PMN phagocytic functions, with the exception of phagocytic activity, starting at 0.125% for ethanol and 0.0625 mM for acetaldehyde. Mo ingestion and microbicidity were decreased at ethanol concentrations of 0.5% without effect on Mo phagocytic activity. Acetaldehyde impaired Mo ingestion ability starting at 0.0625 mM and phagocytic activity at 0.5 mM while was without effect on Mo microbicidity. ROS production was significantly increased at ethanol concentrations 0.25 and 0.5% in PMN and at 0.5% in Mo. These results might partly explain the beneficial role of moderate use of alcohol on cardiovascular disease.

Bone marrow renin-angiotensin system expression in polycythemia vera and essential thrombocythemia depends on JAK2 mutational status.

Recent observations raise possibility for constitutively active, mutated JAK2 to modulate expression of RAS genes in CMPD. We analyzed the expression of AGT, renin, AT2R1 and ACE genes in normal and bone marrows of PV and ET patients with the respect to the presence of V617F JAK2 mutation. PV and ET had different expression patterns of major RAS components compared to normal BM which was primarily associated with the JAK2V617F mutation and less with PV or ET disease phenotype. However, AT2R1 was exclusively markedly upregulated only in PV, while ET showed moderate expression irrespective of the JAK2 mutational status.

T- and B-cell clonality and frequency of human herpes viruses-6, -8 and Epstein Barr virus in angioimmunoblastic T-cell lymphoma.

Angioimmunoblastic T-cell lymphoma (T-AIL) is a peripheral T-cell lymphoma of unknown etiology. Previous clonality studies have shown a heterogeneous composition of this disease with varying restrictions of B- and T-cell populations in the tumour. For the first time in a single study and in the same pathological materials, we have analysed, lymphoid cell clonality and occurrence of human herpes viruses and Epstein Barr virus. Of 18 cases 12 (66.6%) had clonal T- and three (16.6%) had clonal B-cells. Presence of the lymphotropic viral genome of HHV6 was detected in four of 18 lymph node biopsies from T-AIL patients (22%), all were TCRgamma clonal. No HHV8 were found. Epstein Barr genome was found in 40% of cases. There was no significant association between T-cell clonality and HHV-6 or EBV infection, or between B-cell clonality and any virus infection. We conclude that T-AIL is a biologically and clinically heterogeneous entity whose true nature remains to be clarified.