Mechanisms of therapy resistance in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a highly aggressive pediatric cancer that can affect both B cells and T cells. The advent of new therapies has increased the cure rates for both B-ALL and T-ALL patients. However, some patients still experience relapse with a variable response to the treatment and display poor survival. Thus,identification of novel predictive biomarkers that can predict therapy resistance may help to stratify this group of patients. This could also aid in developing an effective treatment strategy.Glucocorticoids are widely used along with the chemotherapeutic regimens for treating ALL patients. The response to glucocorticoids can predict long-term remission outcome. To understand the mechanisms of resistance to glucocorticoids, such as dexamethasone, we generated dexamethasone-resistant B-ALL cell lines in paper I. One such resistant cell line was found to possess increased FLT3 expression levels with FLT3-ITD and FLT3-R845G mutations that led to the activation of oncogenic RTK signaling. Further, second-generation FLT3 inhibitors, such as AC220 and crenolanib, suppressed this signaling both in vitro and in vivo.We continued exploring the dexamethasone resistance mechanisms in paper II using a different approach. We observed that dexamethasone exposure caused upregulation of Aurora kinase and its various downstream effector kinases such as JAK, p38, mTOR, and S6K. These kinases lead to β-catenin stabilization through phosphorylation-dependent inactivation of GSK-3β either directly or indirectly. Indeed, we observed partial restoration of dexamethasone sensitivity with a combination of dexamethasone and inhibitors targeting either these kinases or β-catenin.The expression of BCL2 varies in T-ALL depending on its stage of maturation, thereby T-ALL displays a heterogenous response to the BCL2-specific inhibitor venetoclax. We thus studied the mechanisms of venetoclax resistance using a panel of T-ALL cell lines in paper III. We observed that all the venetoclax-resistant T-ALL cell lines displayed non-universal changes in the expression of BCL2 family members and cancer stem cell markers, along with specific enrichment of cytokine signaling pathways. However, further investigations are warranted to identify additional mechanisms of venetoclax resistance in T-ALL.Combination therapy is usually the choice of treatment to overcome monotherapy resistance. With this in mind, in paper IV we identified that inhibiting BCL2 by venetoclax synergizes with PLK1 inhibition by volasertib in T-ALL cell lines and PDX models. We observed that BCL2L13 and PMAIP1 genes get upregulated upon PLK1 inhibition, probably through transcriptional regulation by FOXOs in interaction with β-catenin. Thus, the pro-apoptotic functions exhibited by BCL2L13 and PMAIP1 probably synergize with BCL2 inhibition in T-ALL, with the help of sustained β-catenin levels. Moreover, we also identified upregulation of oxidative phosphorylation (OXPHOS) in T-ALL PDXs that didn’t display synergy, which could be treated with a combination of venetoclax and oligomycin. However, additional experiments will be required to verify the above results

Interactions between platelets and hematopoietic cells

In addition to their primary role in hemostasis, platelets are increasingly recognized as important participants in numerous biological processes. Their ability to adhere to and communicate with different immune cells, endothelial cells, and cancer cells makes them a natural nexus that participates in development of different diseases, including cancer. Thus, one could also surmise interactions between platelets and hematopoietic stem and progenitor cells. Previous studies have shown that bone marrow function recovers more quickly after transplantation with mobilized peripheral blood stem cells than with bone marrow-derived hematopoietic stem cells. A major difference between the two techniques is that mobilized peripheral blood stem cells are exposed to activated platelets during harvesting. As platelets communicate with a myriad of blood cells and carry cargoes of hundreds of proteins and other biologically active compounds, I wanted to investigate potential interactions between platelets and hematopoietic progenitor cells, including leukemic cells from acute myelogenous leukemia (AML). Using flow cytometric analysis and colony forming unit (CFU) assessment, our group show that platelet releasate inhibits proliferation, conserves erythroid phenotype, and increases levels of erythroid progenitors in cultivated mobilized peripheral blood stem and progenitor cells. Expression of CD14 antigen and monocyte-associated mRNAs also increased, suggesting that platelet releasate induced monocytopoiesis. Upon activation, platelets degranulate and release the content of their alpha granules, dense granules, and lysosomes. Activated platelets also shed platelet microparticles (PMP), membranous vesicles that contain platelet cargo. These microparticles are internalized by many different cells, including cancer cells, and are known to alter their biological behavior. Using flow cytometry and fluorescence microscopy, we show that these microparticles are internalized by AML cells, with a subsequent transfer of miR-125a and miR-125b and a downregulation of the pro-apoptotic protein PUMA. This microRNA transfer could explain the anti-apoptotic properties of PMPs that we also observed following treatment with several apoptosis inductors, where daunorubicin is of particular interest, as it is a mainstay in the treatment of AML. Thus, multiple potential interactions between platelets and hematopoietic progenitor cells and leukemic cells are identified. The results must be confirmed by more advanced in vitro and translational models before their clinical relevance can be fully appreciated, but the findings may benefit ex vivo production of monocytes and erythrocytes and support the use of therapeutic platelet inhibition in AML patients

Nuclear receptors: Lipid and hormone sensors with essential roles in the control of cancer development

Nuclear receptors (NRs) are a superfamily of ligand-activated transcription factors that act as biological sensors and use a combination of mechanisms to modulate positively and negatively gene expression in a spatial and temporal manner. The highly orchestrated biological actions of several NRs influence the proliferation, differentiation, and apoptosis of many different cell types. Synthetic ligands for several NRs have been the focus of extensive drug discovery efforts for cancer intervention. This review summarizes the roles in tumour growth and metastasis of several relevant NR family members, namely androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR), thyroid hormone receptor (TR), retinoic acid receptors (RARs), retinoid X receptors (RXRs), peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). These studies are key to develop improved therapeutic agents based on novel modes of action with reduced side effects and overcoming resistance

Cell Lineage Choice During Haematopoiesis: A Commemorative Issue in Honor of Professor Antonius Rolink

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. This special issue of the International Journal of Molecular Sciences contains a collection of articles by colleagues of Antonius (Ton) Gerardus Rolink (19/04/1953-06/08/2017) and honors Ton’s life and profound knowledge of and huge contribution to science. Ton participated in an FP7 Marie Curie Initial Training Network called DECIDE, and partners have submitted articles for this Special Issue. Scientists outside this network have also submitted articles. The articles examine various aspects of how the hematopoietic stem-cell gives rise to the different types of blood and immune cells. These include decision-making by the hematopoietic stem cell and the importance of controlling events within cells and the niches the cell resides in. New insights into these processes at the basic scientific level have given rise to an emerging new model for the development of blood cells. In turn, changes to our understanding of this process have led to new and exciting propositions regarding what goes wrong during the early stages of the development of leukemia

The Role of CDCA7 in Akt-mediated Myc-Dependent Apoptosis and Proliferation

CDCA7, or cell division cycle associated protein A7, was described in 2001 by Prescott and colleagues as a target of Myc-dependent transcriptional regulation (Prescott et al., 2001). We have identified CDCA7 as associating with the transcription factor Myc and is the target of phosphorylation by the prosurvival serine/threonine kinase Akt. Phosphorylation by Akt at threonine 163 disrupts CDCA7 association with Myc, promotes binding to 14-3-3 and sequestration in the cytoplasm. Coexpression of CDCA7 and Myc in fibroblasts potentiates Myc-dependent apoptosis upon serum withdrawal. In contrast, knockdown of CDCA7 by shRNA abrogated Myc-dependent apoptosis. Myc induced transformation of fibroblasts was reduced in the presence of CDCA7 and significantly inhibited by the expression of the non-Myc binding mutant (156-187) CDCA7. We have shown that CDCA7 enhances the activation of an E-box in a Myc-binding dependent manner. CDCA7 increases Myc occupancy of the proapoptotic BAX promoter, elevates BAX and Cyclin B1 mRNA levels while reducing p15INK4B mRNA levels. This data points to a novel mechanism which implicates Akt phosphorylation of CDCA7 as participating in the dual signal model of Myc of function and thus affecting Myc-dependent growth and transformation. In this study, we have also shown that expression of CDCA7 reduces proliferation rates and shifts cell cycle distribution towards G2/M phase and that phosphorylation of CDCA7 at T163 occurs strictly in G2/M. CDCA7 phosphorylated at threonine 163 colocalizes with the centrosomal protein marker -Tubulin and activated Akt (phospho-serine 473) in mitotic cells. Finally, we have shown that CDCA7 co-associates with monomers of itself which is dependent on amino acids 187-234, adding to the possible mechanisms by which CDCA7 function may be regulated

Recent Developments in Cancer Systems Biology

This ebook includes original research articles and reviews to update readers on the state of the art systems approach to not only discover novel diagnostic and prognostic biomarkers for several cancer types, but also evaluate methodologies to map out important genomic signatures. In addition, therapeutic targets and drug repurposing have been emphasized for a variety of cancer types. In particular, new and established researchers who desire to learn about cancer systems biology and why it is possibly the leading front to a personalized medicine approach will enjoy reading this book

Computational Methods for the Analysis of Genomic Data and Biological Processes

In recent decades, new technologies have made remarkable progress in helping to understand biological systems. Rapid advances in genomic profiling techniques such as microarrays or high-performance sequencing have brought new opportunities and challenges in the fields of computational biology and bioinformatics. Such genetic sequencing techniques allow large amounts of data to be produced, whose analysis and cross-integration could provide a complete view of organisms. As a result, it is necessary to develop new techniques and algorithms that carry out an analysis of these data with reliability and efficiency. This Special Issue collected the latest advances in the field of computational methods for the analysis of gene expression data, and, in particular, the modeling of biological processes. Here we present eleven works selected to be published in this Special Issue due to their interest, quality, and originality