c-Jun promotes cellular survival by suppression of PTEN.

Activation of c-Jun, a component of the AP-1 family of transcription factors, leads to either promotion or prevention of apoptosis. However, the molecular determinants of c-Jun-mediated cell survival are still unclear. We show here that inducible expression of c-Jun promotes cellular survival by negatively regulating the expression of the tumor-suppressor PTEN, resulting in the concomitant activation of the Akt survival pathway. Consistently, c-jun-/- fibroblasts, which are sensitive to nutrient deprivation, and human cell lines in which c-Jun expression is silenced, express elevated levels of PTEN. siRNA-mediated silencing of PTEN resulted in the reduction of cell-death owing to c-Jun deficiency. c-Jun was found to suppress PTEN expression by binding to a variant AP-1 site found in the 5' upstream sequences of PTEN promoter. Finally, an inverse correlation between c-Jun and PTEN levels was apparent in a panel of human tumor cell lines, independent of their p53 status. Together, the data demonstrate that c-Jun contributes to the promotion of cellular survival by regulating the expression of PTEN.

Influence of transplantation regimen on prognostic significance of high-level minimal residual disease before allogeneic stem cell transplantation in children with ALL.

High MRD levels before transplantation in children receiving T cell-depleted unrelated grafts for relapsed ALL were associated with a 100% relapse risk. We report on two children with relapsed ALL who underwent non T cell-depleted BMT from unrelated donors. Despite a high residual tumor load pre- transplant and the occurrence of only aGVHD grade I, they are still in second complete remission 2.7 and 5.2 years after transplantation, respectively. Thus, we propose that the transplant regimens influence the prognostic significance of high MRD levels pre-BMT.

Prognostic value of minimal residual disease in acute lymphoblastic leukaemia in childhood.

BACKGROUND: Sensitive techniques for detection of minimal residual disease (MRD) at degrees of one leukaemic cell per 10(3)-10(6) cells (10(-3)-10(-6)) during follow-up of children with acute lymphoblastic leukaemia (ALL) can provide insight into the effectiveness of cytotoxic treatment. However, it is not yet clear how information on MRD can be applied to treatment protocols. METHODS: We monitored 240 patients with childhood ALL who were treated according to national protocols of the International BFM Study Group. 60 patients relapsed and the patients in continuous complete remission (CCR) had a median event-free follow-up of 48 months. Bone-marrow samples were collected at up to nine time points during and after treatment. Standardised PCR analysis of patient-specific immunoglobulin and T-cell receptor gene rearrangements and TAL1 deletions were used as targets for semiquantitative estimation of MRD. Amount of MRD was classed as 10(-2) or more, 10(-3), and 10(-4) or less. FINDINGS: MRD negativity at the various follow-up times was associated with low relapse rates (3-15% at 3 years), but five-fold to ten-fold higher relapse rates (39-86% at 3 years) were found in MRD-positive patients. The distinct degrees of MRD appeared to have independent prognostic value (p [trend]<0.001) at all separate time points, especially at the first two time points (at the end of induction treatment and before consolidation treatment). At these two time points a high degree of MRD (> or = 10(-2)) was associated with a three-fold higher relapse rate when compared with patients with a low degree of MRD (< or = 10(-4)). At later time points (including the end of treatment) even a low degree of MRD was associated with a poor outcome. Positivity in patients in CCR after treatment was rare (< 1%). With the combined MRD information from the first two follow-up time points, it was possible to recognise three different risk groups--55 (43%) were in a low-risk group and had a 3-year relapse rate of only 2% (95% CI 0.05-12%); 19 (15%) were in a high-risk group and had a relapse rate of 75% (55-95%); and 55 (43%) were in an intermediate-risk group and had a 3-year relapse rate of 23% (13-36%). INTERPRETATION: Our collaborative MRD study shows that monitoring patients with childhood ALL at consecutive time points gives clinically relevant insight into the effectiveness of treatment. Combined information on MRD from the first 3 months of treatment distinguishes patients with good prognoses from those with poor prognoses, and this helps in decisions whether and how to modify treatment.

Multiplex PCR for TCR delta rearrangements: a rapid and specific approach for the detection and identification of immature and mature rearrangements in ALL.

The preferential occurrence of immature T-cell receptor (TCR) delta rearrangements (i.e. incomplete Ddelta2-Ddelta3 and Vdelta2-Ddelta3) in B-cell precursor acute lymphoblastic leukaemia (BCP ALL) and of predominantly mature rearrangements (incomplete Ddelta2-Jdelta1, complete Vdelta1, Vdelta2, Vdelta3 to Jdelta1) in T-lineage ALL prompted us to establish two separate multiplex PCR systems for the identification of clonal TCRdelta rearrangements. PCR products of the expected size for the specific rearrangements were detectable from a dilution of 100-1000 clonal cells in 150000 polyclonal cells. Both multiplex PCR systems were used to analyse samples from 86 childhood BCPALLs and 30 T-lineage ALLs. The results of the multiplex PCRs were controlled by standard PCR analyses for the individual rearrangements and Southern blots, which were identical. Only immature TCRdelta rearrangements were detected in BCP ALL (59%), whereas no rearrangement was found in the remaining BCP leukaemias, thus confirming the exclusive presence of immature TCRdelta rearrangements in B-lineage cells. 50% of the T-lineage ALLs contained mature rearrangements, but no immature rearrangements were found. These two multiplex PCR techniques appear to be reliable and fast aids in the analysis of clonal TCRdelta rearrangements in ALL.