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Background: Drug combinations of the proteasome inhibitor bortezomib with cytotoxic chemotherapy are currently evaluated in phase 2 and 3 trials for the treatment of paediatric acute myeloid leukaemia (AML) and acute lymphocytic leukaemia (ALL)., Methods: We investigated whether expression ratios of immunoproteasome to constitutive proteasome in leukaemic cells correlated with response to bortezomib-containing re-induction chemotherapy in patients with relapsed and refractory acute leukaemia, enrolled in two Children's Oncology Group phase 2 trials of bortezomib for ALL (COG-AALL07P1) and AML (COG-AAML07P1). Expression of proteasome subunits was examined in 72 patient samples (ALL n = 60, AML n = 12) obtained before start of therapy. Statistical significance between groups was determined by Mann-Whitney U test., Results: Ratios of immunoproteasome to constitutive proteasome subunit expression were significantly higher in pre-B ALL cells than in AML cells for both β5i/β5 and β1i/β1 subunits (p = 0.004 and p < 0.001). These ratios correlated with therapy response in AML patients; β1i/β1 ratios were significantly higher (p = 0.028) between patients who did (n = 4) and did not reach complete remission (CR) (n = 8), although for β5i/β5 ratios, this did not reach significance. For ALL patients, the subunit ratios were also higher for patients who showed a good early response to therapy but this relation was not statistically significant. Overall, for this study, the patients were treated with combination therapy, so response was not only attributed to proteasome inhibition. Moreover, the leukaemic blast cells were not purified for these samples., Conclusions: These first ex vivo results encourage further studies into relative proteasome subunit expression to improve proteasome inhibition-containing therapy and as a potential indicator of bortezomib response in acute leukaemia.

Background: Hypoxia acts as a plant stress factor, particularly in cucumbers plants under hydroponic culture. Calcium is involved in stress signal transmission and in the growth of plants. To determine the effect of exogenous calcium on hypoxic-responsive proteins in cucumber (Cucumis sativus L. cv. Jinchun No.2) roots, proteomic analysis was performed using two-dimensional electrophoresis (2-DE) and mass spectrometry., Results: Cucumber roots were used to analyze the influence of hypoxia on plants. The expressions of 38 protein spots corresponding to enzymes were shown to change in response to hypoxia. Of these, 30 spots were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF/TOF MS analysis). The proteins were categorized according to functional groups, including glycolysis, the tricarboxylic acid (TCA) cycle, fermentative metabolism, nitrogen metabolism, energy metabolism, protein synthesis and defense against stress. Exogenous calcium appeared to alleviate hypoxic stress via these metabolic and physiological systems. Western blotting was used to analyze the accumulation of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC); calcium further increased the expression of ADH and PDC under hypoxia. In addition, semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to assess the transcript levels of differentially expressed proteins., Conclusions: Exogenous calcium enhanced the expression of enzymes involved in glycolysis, the TCA cycle, fermentative metabolism, nitrogen metabolism, and reactive oxygen species (ROS) defense in plants under hypoxia. Calcium appears to induce hypoxic tolerance of cucumber seedlings. These phenomena have prompted us to further investigate the mechanisms by which cucumbers respond to exogenous calcium under hypoxia.

Background: As a newly identified category of DNA transposon, helitrons have been found in a large number of eukaryotes genomes. Helitrons have contributed significantly to the intra-specific genome diversity in maize. Although many characteristics of helitrons in the maize genome have been well documented, the sequence of an intact autonomous helitrons has not been identified in maize. In addition, the process of gene fragment capturing during the transposition of helitrons has not been characterized., Results: The whole genome sequences of maize inbred line B73 were analyzed, 1,649 helitron-like transposons including 1,515 helAs and 134 helBs were identified. ZmhelA1, ZmhelB1 and ZmhelB2 all encode an open reading frame (ORF) with intact replication initiator (Rep) motif and a DNA helicase (Hel) domain, which are similar to previously reported autonomous helitrons in other organisms. The putative autonomous ZmhelB1 and ZmhelB2 contain an extra replication factor-a protein1 (RPA1) transposase (RPA-TPase) including three single strand DNA-binding domains (DBD)-A/-B/-C in the ORF. Over ninety percent of maize helitrons identified have captured gene fragments. HelAs and helBs carry 4,645 and 249 gene fragments, which yield 2,507 and 187 different genes respectively. Many helitrons contain mutilple terminal sequences, but only one 3'-terminal sequence had an intact "CTAG" motif. There were no significant differences in the 5'-termini sequence between the veritas terminal sequence and the pseudo sequence. Helitrons not only can capture fragments, but were also shown to lose internal sequences during the course of transposing., Conclusions: Three putative autonomous elements were identified, which encoded an intact Rep motif and a DNA helicase domain, suggesting that autonomous helitrons may exist in modern maize. The results indicate that gene fragments captured during the transposition of many helitrons happen in a stepwise way, with multiple gene fragments within one helitron resulting from several sequential transpositions. In addition, we have proposed a potential mechanism regarding how helitrons with multiple termini are generated.