A regimen of busulfan and cyclophosphamide (BuCy2) is regarded as the standard myeloablative regimen for SCT. This study evaluated the hypothesis that fludarabine can replace cyclophosphamide for myeloablative allogeneic SCT. Ninety-five patients underwent allogeneic SCT from HLA-identical donors, following BuCy2 (n ¼ 55) or busulfan þ fludarabine (BF, n ¼ 40). The efficacy of fludarabine compared to cyclophosphamide was retrospectively evaluated. The BF group exhibited a shorter duration until engraftment (P ¼ 0.001), lower incidence of acute and chronic GVHD (Po0.001 and P ¼ 0.003, respectively), and non-relapse mortality (NRM) (P ¼ 0.039). Furthermore, the event-free survival and overall survival were significantly higher for the BF group compared to the BuCy2 group (P ¼ 0.004 and 0.002, respectively). After adjusting for age, the risk status of disease, GVHD prophylaxis and donor type, the BF regimen was found to be an independent favorable risk factor for event-free survival (hazard ratio (HR), 0.181; 95% confidence interval, 0.045-0.720; P ¼ 0.016) and overall survival (HR, 0.168;; P ¼ 0.026). The replacement of cyclophosphamide with fludarabine for myeloablative conditioning seems to be more effective in terms of short-term NRM, and GVHD compared to BuCy2 regimen in allogeneic transplantation.
PTEN is one of the most frequently mutated or deleted tumor suppressors in human cancers. NEDD4-1 was recently identified as the E3 ubiquitin ligase for PTEN; however, a number of important questions remain regarding the role of ubiquitination in regulating PTEN function and the mechanisms by which PTEN ubiquitination is regulated. In the present study, we demonstrated that p34, which was identified as a binding partner of NEDD4-1, controls PTEN ubiquitination by regulating NEDD4-1 protein stability. p34 interacts with the WW1 domain of NEDD4-1, an interaction that enhances NEDD4-1 stability. Expression of p34 promotes PTEN poly-ubiquitination, leading to PTEN protein degradation, whereas p34 knockdown results in PTEN mono-ubiquitination. Notably, an inverse correlation between PTEN and p34/NEDD4-1 levels was confirmed in tumor samples from colon cancer patients. Thus, p34 acts as a key regulator of the oncogenic behavior of NEDD4-1 and PTEN.
The downstream events and target genes of p53 in the process of senescence are not fully understood. Here, we report a novel function of the forkhead transcription factor Foxp3, which is a key player in mediating T-cell inhibitory functions, in p53-mediated cellular senescence. The overexpression of Foxp3 in mouse embryonic fibroblasts (MEFs) accelerates senescence, whereas Foxp3 knockdown leads to escape from p53-mediated senescence in p53-expressing MEFs. Consistent with these results, Foxp3 expression resulted in the induction of senescence in epithelial cancer cells, including MCF7 and HCT116 cells. Foxp3 overexpression also increased the intracellular levels of reactive oxygen species (ROS). The ROS inhibitor N-acetyl-l-cysteine rescued cells from Foxp3-expression-induced senescence. Furthermore, the elevated ROS levels that accompanied Foxp3 overexpression were paralleled by an increase in p21 expression. Knockdown of p21 in Foxp3-expressing MEFs abrogated the Foxp3-dependent increase in ROS levels, indicating that Foxp3 acts through the induction of p21 and the subsequent ROS elevation to trigger senescence. Collectively, these results suggest that Foxp3 is a downstream target of p53 that is sufficient to induce p21 expression, ROS production and p53-mediated senescence.
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