Up-regulation of survivin by the E2A-HLF chimera is indispensable for the survival of t(17;19)-positive leukemia cells

Eya2 is critical for the E2A‑HLF‑mediated immortalization of mouse hematopoietic stem/progenitor cells

The immunoglobulin enhancer‑binding factor/hepatic leukemia factor (E2A‑HLF) oncogenic fusion gene, generated by t(17;19)(q22;p13) translocation in childhood B‑cell acute lymphoblastic leukemia with a very poor prognosis, encodes a chimeric transcription factor in which the transactivation domains of E2A are fused to the DNA‑binding and dimerization domain of HLF. E2A‑HLF has been demonstrated to have an anti‑apoptotic effect. However, the molecular mechanism underlying E2A‑HLF‑mediated leukemogenesis remains unclear. The present study identified EYA transcriptional coactivator and phosphatase 2 (Eya2), the forced expression of which is known to immortalize mouse hematopoietic stem/progenitor cells (HSPCs), as a direct target molecule downstream of E2A‑HLF. E2A‑HLF‑immortalized mouse HSPCs expressed Eya2 at a high level in the aberrant self‑renewal program. Chromatin immunoprecipitation‑quantitative polymerase chain reaction and a reporter assay revealed that E2A‑HLF enhanced the Eya2 expression by binding to the promoter region containing the E2A‑HLF‑binding consensus sequence. Eya2 knockdown in E2A‑HLF‑immortalized cells resulted in reduced colony‑forming efficiency. These results suggest a critical role of Eya2 in E2A‑HLF‑mediated leukemogenesis.

Conditional Expression of E2A-HLF Induces B-Cell Precursor Death and Myeloproliferative-Like Disease in Knock-In Mice

Chromosomal translocations are driver mutations of human cancers, particularly leukemias. They define disease subtypes and are used as prognostic markers, for minimal residual disease monitoring and therapeutic targets. Due to their low incidence, several translocations and their biological consequences remain poorly characterized. To address this, we engineered mouse strains that conditionally express E2A-HLF, a fusion oncogene from the translocation t(17;19) associated with 1% of pediatric B-cell precursor ALL. Conditional oncogene activation and expression were directed to the B-cell compartment by the Cre driver promoters CD19 or Mb1 (Igα, CD79a), or to the hematopoietic stem cell compartment by the Mx1 promoter. E2A-HLF expression in B-cell progenitors induced hyposplenia and lymphopenia, whereas expression in hematopoietic stem/progenitor cells was embryonic lethal. Increased cell death was detected in E2A-HLF expressing cells, suggesting the need for cooperating genetic events that suppress cell death for B-cell oncogenic transformation. E2A-HLF/Mb1.Cre aged mice developed a fatal myeloproliferative-like disorder with low frequency characterized by leukocytosis, anemia, hepatosplenomegaly and organ-infiltration by mature myelocytes. In conclusion, we have developed conditional E2A-HLF knock-in mice, which provide an experimental platform to study cooperating genetic events and further elucidate translational biology in cross-species comparative studies.

Discovery of novel second mitochondria-derived activator of caspase mimetics as selective inhibitor of apoptosis protein inhibitors

Inhibitor of apoptosis (IAP) proteins are widely considered as promising cancer drug targets, especially for drug-resistant tumors. Mimicking the IAP-binding motif of second mitochondria-derived activator of caspases (SMAC) is a rational strategy to design potential IAP inhibitors. In this report, we used the bioactive conformation of AVPI tetrapeptide in the N terminus of SMAC as a template and performed a shape-based virtual screening against a drug-like compound library to identify novel IAP inhibitors. Top hits were subsequently docked to available IAP crystal structures as a secondary screening followed by validation using in vitro biologic assays. Four novel hit compounds were identified to potently inhibit cell growth in two human melanoma (A375 and M14) and two human prostate (PC-3 and DU145) cancer cell lines. The best compound, UC-112 [5-((benzyloxy)methyl)-7-(pyrrolidin-1-ylmethyl)quinolin-8-ol], has IC50 values ranging from 0.7 to 3.4 µM. UC-112 also potently inhibits the growth of P-glycoprotein (P-gp)-overexpressed multidrug-resistant cancer cells, strongly activates caspase-3/7 and caspase-9 activities, and selectively downregulates survivin level at a concentration as low as 1 µM. Coincubation of UC-112 with a known proteasome inhibitor Z-Leu-Leu-Leu-CHO (MG-132) rescued survivin inhibition, consistent with the anticipated mechanism of action for UC-112. As a single agent, UC-112 strongly inhibits tumor growth and reduces both X chromosome-linked IAP and survivin levels in an A375 human melanoma xenograft model in vivo. Overall, our study identified novel scaffolds, especially UC-112, as new platforms on which potent and selective IAP antagonists can be developed.

Survivin and YM155: how faithful is the liaison?

Survivin belongs to the family of apoptosis inhibitors (IAPs), which antagonizes the induction of cell death. Dysregulated expression of IAPs is frequently observed in cancers, and the high levels of survivin in tumors compared to normal adult tissues make it an attractive target for pharmacological interventions. The small imidazolium-based compound YM155 has recently been reported to block the expression of survivin via inhibition of the survivin promoter. Recent data, however, question that this is the sole and main effect of this drug, which is already being tested in ongoing clinical studies. Here, we critically review the current data on YM155 and other new experimental agents supposed to antagonize survivin. We summarize how cells from various tumor entities and with differential expression of the tumor suppressor p53 respond to this agent in vitro and as murine xenografts. Additionally, we recapitulate clinical trials conducted with YM155. Our article further considers the potency of YM155 in combination with other anti-cancer agents and epigenetic modulators. We also assess state-of-the-art data on the sometimes very promiscuous molecular mechanisms affected by YM155 in cancer cells.

Survivin expression and prognostic significance in pediatric malignant peripheral nerve sheath tumors (MPNST)

Malignant peripheral nerve sheath tumors (MPNST) are very aggressive malignancies comprising approximately 5–10% of all soft tissue sarcomas. In this study, we focused on pediatric MPNST arising in the first 2 decades of life, as they represent one the most frequent non-rhabdomyosarcomatous soft tissue sarcomas in children. In MPNST, several genetic alterations affect the chromosomal region 17q encompassing the BIRC5/SURVIVIN gene. As cancer-specific expression of survivin has been found to be an effective marker for cancer detection and outcome prediction, we analyzed survivin expression in 35 tumor samples derived from young patients affected by sporadic and neurofibromatosis type 1-associated MPNST. Survivin mRNA and protein expression were assessed by Real-Time PCR and immunohistochemical staining, respectively, while gene amplification was analyzed by FISH. Data were correlated with the clinicopathological characteristics of patients. Survivin mRNA was overexpressed in pediatric MPNST and associated to a copy number gain of BIRC5; furthermore, increased levels of transcripts correlated with a higher FNCLCC tumor grade (grade 1 and 2 vs. 3, p = 0.0067), and with a lower survival probability (Log-rank test, p = 0.0038). Overall, these data support the concept that survivin can be regarded as a useful prognostic marker for pediatric MPNST and a promising target for therapeutic interventions.

Cell separation by countercurrent centrifugal elutriation: recent developments

Countercurrent centrifugal elutriation (CCE) is a cell separation technique that separates particles predominantly according to their size, and to some degree according to their specific density, without a need for antibodies or ligands tagging cell surfaces. The principles of this technique have been known for half a century. Still, numerous recent publications confirmed that CCE is a valuable supplement to current cell separation technology. It is mainly applied when homogeneous populations of cells, which mirror an in vivo situation, are required for answering scientific questions or for clinical transplantation, while antibodies or ligands suitable for cell isolation are not available. Currently, new technical developments are expanding its application toward fractionation of healthy and malignant tissue cells and the preparation of dendritic cells for immunotherapy.

Targeting survivin and p53 in pediatric acute lymphoblastic leukemia

Despite advances in treatment and outcomes for patients with pediatric acute lymphoblastic leukemia (ALL), there continue to be subsets of patients who are refractory to standard chemotherapy and hematopoietic stem cell transplant. Therefore, novel gene targets for therapy are needed to further advance treatment for this disease. RNA interference technology has identified survivin as a potential therapeutic target. Survivin, a member of the inhibitor of apoptosis (IAP) proteins and chromosome passenger complex, is expressed in hematologic malignancies and overexpressed in relapsed pediatric ALL. Our studies show that survivin is uniformly expressed at high levels in multiple pediatric ALL cell lines. Furthermore, silencing of survivin expression in pediatric ALL cell lines as well as primary leukemic blasts reduces viability of these cells. This includes cell lines derived from patients with relapsed disease featuring cytogenetic anomalies such as t(12;21), Philadelphia chromosome t(9;22), t(1;19) as well as a cell line carrying t(17;19) from a patient with de novo ALL. Furthermore, inhibition of survivin increases p53-dependent apoptosis that can be rescued by inhibition of p53. Finally, a screen of randomly selected primary patient samples confirms that survivin-specific small interfering RNA and survivin-targeted drug, YM155, effectively reduce viability of leukemic blasts.

Targeting survivin in cancer: the cell-signalling perspective

Survivin, a prominent anticancer target, is ubiquitously expressed in a plethora of cancers and the evolving complexity in functional regulation of survivin is yet to be deciphered. However, pertaining to the recent studies, therapeutic modulation of survivin is critically regulated by interaction with prominent cell-signalling pathways [HIF-1α, HSP90, PI3K/AKT, mTOR, ERK, tumour suppressor genes (p53, PTEN), oncogenes (Bcl-2, Ras)] and a wide range of growth factors (EGFR, VEGF, among others). In our article we discuss, in detail, an overview of the recent developments in the pharmacological modulation of survivin via cell-signalling paradigms and antisurvivin therapeutics, along with an outlook on therapeutic management of survivin in drug-resistant cancers.

Optimization based tumor classification from microarray gene expression data

BACKGROUND

An important use of data obtained from microarray measurements is the classification of tumor types with respect to genes that are either up or down regulated in specific cancer types. A number of algorithms have been proposed to obtain such classifications. These algorithms usually require parameter optimization to obtain accurate results depending on the type of data. Additionally, it is highly critical to find an optimal set of markers among those up or down regulated genes that can be clinically utilized to build assays for the diagnosis or to follow progression of specific cancer types. In this paper, we employ a mixed integer programming based classification algorithm named hyper-box enclosure method (HBE) for the classification of some cancer types with a minimal set of predictor genes. This optimization based method which is a user friendly and efficient classifier may allow the clinicians to diagnose and follow progression of certain cancer types.

METHODOLOGY/PRINCIPAL FINDINGS

We apply HBE algorithm to some well known data sets such as leukemia, prostate cancer, diffuse large B-cell lymphoma (DLBCL), small round blue cell tumors (SRBCT) to find some predictor genes that can be utilized for diagnosis and prognosis in a robust manner with a high accuracy. Our approach does not require any modification or parameter optimization for each data set. Additionally, information gain attribute evaluator, relief attribute evaluator and correlation-based feature selection methods are employed for the gene selection. The results are compared with those from other studies and biological roles of selected genes in corresponding cancer type are described.

CONCLUSIONS/SIGNIFICANCE

The performance of our algorithm overall was better than the other algorithms reported in the literature and classifiers found in WEKA data-mining package. Since it does not require a parameter optimization and it performs consistently very high prediction rate on different type of data sets, HBE method is an effective and consistent tool for cancer type prediction with a small number of gene markers.