Cytoplasmic localization of wild-type survivin is associated with constitutive activation of the PI3K/Akt signaling pathway and represents a favorable prognostic factor in patients with acute myeloid leukemia.

Survivin is over-expressed in most hematologic malignancies but the prognostic significance of the subcompartmental distribution of wild-type or splicing variants in acute myeloid leukemia has not been addressed yet. Using western blotting, we assessed the expression of wild-type survivin and survivin splice variants 2B and Delta-Ex3 in nuclear and cytoplasmic protein extracts in samples taken from 105 patients at the time of their diagnosis of acute myeloid leukemia. Given that survivin is a downstream effector of the PI3K/Akt signaling pathway, survivin expression was also correlated with pSer473-Akt. Wild-type survivin and the 2B splice variant were positive in 76.3% and 78.0% of samples in the nucleus, cytoplasm or both, whereas the Delta-Ex3 isoform was only positive in the nucleus in 37.7% of samples. Cytoplasmic localization of wild-type survivin was significantly associated with the presence of high levels of pSer473-Akt (P<0.001). Inhibition of the PI3K/Akt pathway with wortmannin and Ly294002 caused a significant reduction in the expression of cytoplasmic wild-type survivin. The presence of cytoplasmic wild-type survivin and pSer473-Akt was associated with a lower fraction of quiescent leukemia stem cells (P=0.02). The presence of cytoplasmic wild-type survivin and pSer473-Akt were favorable independent prognostic factors. Moreover, the activation of the PI3K/Akt pathway with expression of cytoplasmic wild-type survivin identified a subgroup of acute myeloid leukemia patients with an excellent outcome (overall survival rate of 60.0±21.9% and relapse-free survival of 63.0±13.5%). Our findings suggest that cytoplasmic wild-type survivin is a critical downstream effector of the PI3K/Akt pathway leading to more chemosensitive cells and a more favorable outcome in acute myeloid leukemia.

MicroRNA signatures and treatment response in patients with advanced classical Hodgkin lymphoma.

Although specific microRNA (miRNA) signatures in classical Hodgkin lymphoma (cHL) have been proposed, their relationship with clinical outcome remains unclear. Despite treatment advances, a substantial subset of patients with advanced cHL are refractory to standard therapies based on adriamycin and its variants. Global miRNA expression data of 29 advanced cHL patients and five cHL-derived cell lines were used to identify profiles from Hodgkin-Reed-Sternberg (HRS) cells and their non-tumoural microenvironment. A cHL-miRNA signature was identified with 234 miRNAs differentially expressed. A subset of these miRNAs was associated with outcome and selected for study in an independent set of 168 cHL samples using quantitative reverse transcription polymerase chain reaction. Multivariate Cox regression analyses including cross-validation with failure-free survival (FFS) as clinical endpoint revealed a miRNA signature with MIR21, MIR30E, MIR30D and MIR92B* that identified two risk-groups with significant differences in 5-year FFS (81% vs. 35.7%; P < 0.001). Additionally, functional silencing of MIR21 and MIR30D in L428 cells showed increased sensitivity to doxorubicin-induced apoptosis, pointing towards abnormalities of mitochondrial intrinsic and TP53-CDKN1A pathways as related to miRNA deregulation in cHL. These results suggest that clinical outcome in cHL is associated with a specific miRNA signature. Moreover, functional analyses suggest a role for MIR21 and MIR30D in cHL pathogenesis and therapeutic resistance.