CD34+ leukemic subpopulation predominantly displays lower spontaneous apoptosis and has higher expression levels of Bcl-2 and MDR1 genes than CD34− cells in childhood AML

In view of obscure clinical and biological significance of leukemic cells heterogeneity, we studied the efficacy of apoptosis, proliferation, and expression levels of the Bcl-2, MDR1, LRP, and BCRP genes in sorted CD34+ and CD34− subpopulations of childhood AML leukemic samples. In five out of nine cases, CD34+ cells were less sensitive to spontaneous apoptosis and had from 1.2- to 5.0-fold higher expression levels of Bcl-2 (eight of ten) and from 1.5- to 28.7-fold higher expression levels of MDR1 (eight of ten). The expression levels of the LRP gene were from 1.1- to 1.8-fold higher in CD34+ subpopulations (five of ten cases), and the expression levels of the BCRP gene were from 1.1- to 22.4-fold higher in CD34+ leukemic cells (six of ten). In all M4 cases, the expression levels of LRP were higher in the CD34− subpopulation. Significant differences in the patterns of genes expression between patients do not allow us to conclude that the CD34+ fractions have more resistant phenotype than the CD34− subpopulations. Nevertheless, distinctions between CD34+ and CD34− cells may lead to different chemosensitivities between leukemic subpopulations in vivo and may determine the alteration of the leukemic immunophenotype during treatment and in relapse.     

Apoptosis and proliferation differences between CD34+ and CD34- leukemic subpopulations in childhood acute leukemia

In view of the clinical and biological significance of leukemic heterogeneity we studied the efficacy of spontaneous apoptosis and cell cycle distribution in CD34+ and CD34 - leukemic subpopulations. Acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) leukemic samples with CD34 heterogeneous expression were separated into CD34+ and CD34 - fractions using fluorescence activated cell sorting. Cell cycle distribution, and apoptosis of the sorted subpopulations were estimated. CD34+ leukemic subpopulations had lower ability to apoptosis than that of CD34 - fractions in 6 out of 8 ALL samples and in 4 out of 5 AML samples. CD34+ fractions showed a higher percentage of proliferating cells compared to CD34 - cells in T-lineage ALL. These differences may lead to a more resistant phenotype of one of the subpopulations and reappearance this population in relapse.     

Neuronal level of organization of the visual analyzer in frog tectum

A study of neuronal responses of frog tectum to diffuse light and a moving visual stimulus, in which paired microelectrodes were used, disclosed the excitation-inhibition constructions originating in the midbrain tectum in response to various forms of visual stimulation. It was demonstrated that the dimensions of the excitation zones of these constructions are 100–200 in cross section, and are separated by inhibition zones. The dimensions of the excitatory tectal constructions resulting from various kinds of visual stimulation correlated with the width of the branching zones and locations of terminals of the afferents and intratectal fibers.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 68, No. 1, pp. 19–24, January, 1982.     

Epidemiology of venous thromboembolism in children with malignant diseases: a single-center study of the Belarusian Center for Pediatric Oncology and Hematology

Background

Venous thrombosis is a complication of treatment of children with cancer but studies devoted to the epidemiology of thrombosis in children with cancer are rare and data are scanty.

Objective

To determine the prevalence and clinical characteristics of VT as a secondary complication in children with malignant disease and to estimate the ten-year experience of our hospital.

Method

Retrospective analysis of data of Children's Cancer Subregistry of Belarus, which included information about age, gender, details of diagnosis, classification of malignant neoplasm according to ICD-10, treatment protocol and outcome. Clinical information was obtained from case histories.

Results

For the specified period, 2061 children with newly diagnosed cancer and 44 cases of VT have been registered. Among VT cases, hematological malignancies prevailed (32 of total 44). Higher incidence of VT in AML and APL groups was shown (p‹0.05). In patients with VT, boys (M/F = 1,6/1) and teenagers prevailed (65,9%). Of 44 patients, 33 had catheter-associated thrombosis (CAT). Almost all CAT (91,7%) were in the upper venous system. Children with non-CAT (11 out of 44) had more prolonged duration of immobilization, than children with CAT (p‹0.05) and in this group, thrombosis affected predominantly the lower limb (9 out of 11).

Conclusion

The present study has shown that venous thrombosis occurs significantly more often in children with AML and APL. Prevalence of boys in patients with venous thrombosis has been noted. Increased frequency of VT events in teenagers has been observed and the provoking role of CVC and immobilization for thrombosis has been confirmed.     

Dietary polyamines promote the growth of azoxymethane-induced aberrant crypt foci in rat colon

We have examined whether dietary polyamines influence the formation and initial growth of azoxymethane (AOM)-induced aberrant crypt foci (ACF) in rat colon. Effects of a combination of dietary polyamines at three dose levels (putrescine: 50, 280, 740 nmol/g; spermidine: 10, 261, 763 nmol/g; spermine: 1, 31, 91 nmol/g) in the polyamine-poor AIN-76A diet were studied in animals in two different experimental situations: animals treated with AOM alone and animals treated with AOM + difluoromethylornithine (DFMO), a specific inhibitor of endogenous polyamine synthesis. In both experimental situations, dietary polyamines enhanced the growth of ACF, expressed as the number of large ACF (foci with three or more aberrant crypts, ACF > or = 3), whereas the formation of ACF, expressed as the number of ACF, was apparently not altered. In animals treated with AOM alone, maximal growth enhancing effect on ACF was nearly obtained with the median level of dietary polyamine. In rats fed a low polyamine diet, basic AIN-76A, DFMO reduced the growth of AOM-induced ACF by 83%. This inhibitory effect of DFMO was counteracted by dietary polyamines in a dose- dependent manner, and it was abolished at the highest level of polyamines. In conclusion, it was demonstrated that dietary polyamines are able to enhance the growth of AOM-induced ACF. Further, dietary polyamines reversed the DFMO-caused inhibition of ACF growth, probably by compensating for the DFMO-reduced endogenous polyamine synthesis.      

Prognostic value of MRD-dynamics in childhood acute lymphoblastic leukemia treated according to the MB-2002/2008 protocols

Detection of minimal residual disease (MRD) during the treatment of acute lymphoblastic leukemia (ALL) by RQ-PCR analysis of clonal Ig/TCR rearrangements is used for risk group stratification in European treatment protocols. In Belarus patients with childhood ALL are treated according to ALL-MB protocols, which do not use MRD-based risk stratification. To evaluate the prognostic significance of MRD for ALL-MB-2002/2008 protocols, MRD was quantified by RQ-PCR in 68 ALL patients at four time points: on day 15, on day 36, before and after maintenance therapy (MT). MRD positivity, as well as quantitative level of MRD were analyzed and compared between patients who stayed in remission and relapsed. Relapse-free survival revealed to be significantly associated with MRD levels at different time points. Unfavorable prognosis was shown for MRD ≥ 10⁻³ on day 36 (p < 0.001), and any positive MRD before (p < 0.001) and after (p = 0.001) MT. Multivariate Cox regression analysis proved MRD as independent significant prognosis factor at day 36 (p = 0.005) and before MT (p = 0.001). We conclude, that MRD quantified by RQ-PCR in children with ALL treated with ALL-MB protocols is feasible and independently associated with outcome. MRD may be a suitable parameter for treatment stratification in MB protocols in future.