The non-genomic loss of function of tumor suppressors: an essential role in the pathogenesis of chronic myeloid leukemia chronic phase

Pathogenesis and management of accelerated and blast phases of chronic myeloid leukemia

The treatment of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKIs) has been a model for cancer therapy development. Though most patients with CML have a normal quality and duration of life with TKI therapy, some patients progress to accelerated phase (AP) and blast phase (BP), both of which have a relatively poor prognosis. The rates of progression have reduced significantly from over >20% in the pre-TKI era to <5% now, largely due to refinements in CML therapy and response monitoring. Significant insights have been gained into the mechanisms of disease transformation including the role of additional cytogenetic abnormalities, somatic mutations, and other genomic alterations present at diagnosis or evolving on therapy. This knowledge is helping to optimize TKI therapy, improve prognostication and inform the development of novel combination regimens in these patients. While patients with de novo CML-AP have outcomes almost similar to CML in chronic phase (CP), those transformed from previously treated CML-CP should receive second- or third- generation TKIs and be strongly considered for allogeneic stem cell transplantation (allo-SCT). Similarly, patients with transformed CML-BP have particularly dismal outcomes with a median survival usually less than one year. Combination regimens with a potent TKI such as ponatinib followed by allo-SCT can achieve long-term survival in some transformed BP patients. Regimens including venetoclax in myeloid BP or inotuzumab ozogamicin or blinatumomab in lymphoid BP might lead to deeper and longer responses, facilitating potentially curative allo-SCT for patients with CML-BP once CP is achieved. Newer agents and novel combination therapies are further expanding the therapeutic arsenal in advanced phase CML.

Copper-imidazo[1,2-a]pyridines differentially modulate pro- and anti-apoptotic protein and gene expression in HL-60 and K562 leukaemic cells to cause apoptotic cell death

Despite the availability of a myriad targeted treatments, resistance and treatment failures remains common in cancer treatment. Moreover, the high cost of targeted antibodies excludes a large cohort of patients from their benefits. In this context, copper-imidazo[1,2-a]pyridines were evaluated as alternative drug candidates against two common leukaemias, represented by HL-60 and K562 cells. A previous study identified JD88(21), JD47(29) and JD49(28) to be active against these cell lines with IC₅₀ values between 1.9 and 6 μM and low leukocyte toxicity. To better understand their mechanism of action, their mode of cell death, effects on expression of apoptotic regulatory proteins and their respective genes were investigated. In both cell lines, the copper-imidazo[1,2-a]pyridines, at IC₇₅ concentrations, caused membrane blebbing, raised phosphatidyl-serine levels on cell membranes and increased caspase-3 activity. A loss of mitochondrial membrane potential and activation of caspase-9, combined with poor caspase-8 activity indicated activation of intrinsic apoptosis. Apoptotic proteome analysis showed that the copper-imidazo[1,2-a] pyridines elevated protein levels of pro-apoptotic Bax and Smac/DIABLO in both cell lines, confirming their importance in apoptotic cell death. Conversely, though survivin was increased, this was counteracted by high levels of HTRA2/Omi expression. Effects on apoptotic regulatory proteins Bad, Bcl-2, XIAP and cIAP-1 was inconsistent between the copper-imidazo[1,2-a]pyridines and between the two cell lines, suggesting that the effect of the complexes was modulated by the molecular signature of each cell line. Analysis of mRNA transcripts showed a poor correlation between mRNA levels and associated proteins, implying that copper-imidazo[1,2-a]pyridines compromised protein synthesis and degradation.

NF-κB-Dependent and -Independent (Moonlighting) IκBα Functions in Differentiation and Cancer

IκBα is considered to play an almost exclusive role as inhibitor of the NF-κB signaling pathway. However, previous results have demonstrated that SUMOylation imposes a distinct subcellular distribution, regulation, NF-κB-binding affinity and function to the IκBα protein. In this review we discuss the main alterations of IκBα found in cancer and whether they are (most likely) associated with NF-κB-dependent or NF-κB-independent (moonlighting) activities of the protein.

Emerging Kinase Therapeutic Targets in Pancreatic Ductal Adenocarcinoma and Pancreatic Cancer Desmoplasia

Kinase drug discovery represents an active area of therapeutic research, with previous pharmaceutical success improving patient outcomes across a wide variety of human diseases. In pancreatic ductal adenocarcinoma (PDAC), innovative pharmaceutical strategies such as kinase targeting have been unable to appreciably increase patient survival. This may be due, in part, to unchecked desmoplastic reactions to pancreatic tumors. Desmoplastic stroma enhances tumor development and progression while simultaneously restricting drug delivery to the tumor cells it protects. Emerging evidence indicates that many of the pathologic fibrotic processes directly or indirectly supporting desmoplasia may be driven by targetable protein tyrosine kinases such as Fyn-related kinase (FRK); B lymphoid kinase (BLK); hemopoietic cell kinase (HCK); ABL proto-oncogene 2 kinase (ABL2); discoidin domain receptor 1 kinase (DDR1); Lck/Yes-related novel kinase (LYN); ephrin receptor A8 kinase (EPHA8); FYN proto-oncogene kinase (FYN); lymphocyte cell-specific kinase (LCK); tec protein kinase (TEC). Herein, we review literature related to these kinases and posit signaling networks, mechanisms, and biochemical relationships by which this group may contribute to PDAC tumor growth and desmoplasia.

Strategies For Targeting Chronic Myeloid Leukaemia Stem Cells

Chronic Myeloid Leukaemia is a myeloproliferative disorder driven by the t(9;22) chromosomal translocation coding for the chimeric protein BCR-ABL. CML treatment represents the paradigm of molecular therapy of cancer. Since the development of the tyrosine kinase inhibitor of the BCR-ABL kinase, the clinical approach to CML has dramatically changed, with a stunning improvement in the quality of life and response rates of patients. However, it remains clear that tyrosine kinase inhibitors (TKIs) are unable to target the most immature cellular component of CML, the CML stem cell. This review summarizes new insights into the mechanisms of resistance to TKIs.

Nuclear-cytoplasmic Shuttling in Chronic Myeloid Leukemia: Implications in Leukemia Maintenance and Therapy

Nuclear-cytoplasmic shuttling is a highly regulated and complex process, which involves both proteins and nucleic acids. Changes in cellular compartmentalization of various proteins, including oncogenes and tumor suppressors, affect cellular behavior, promoting or inhibiting proliferation, apoptosis and sensitivity to therapies. In this review, we will recapitulate the role of various shuttling components in Chronic Myeloid Leukemia and we will provide insights on the potential role of shuttling proteins as therapeutic targets.

Metabolic, Anti-apoptotic and Immune Evasion Strategies of Primary Human Myeloma Cells Indicate Adaptations to Hypoxia

Multiple Myeloma (MM) is an incurable plasma cell malignancy primarily localized within the bone marrow (BM). It develops from a premalignant stage, monoclonal gammopathy of undetermined significance (MGUS), often via an intermediate stage, smoldering MM (SMM). The mechanisms of MM progression have not yet been fully understood, all the more because patients with MGUS and SMM already carry similar initial mutations as found in MM cells. Over the last years, increased importance has been attributed to the tumor microenvironment and its role in the pathophysiology of the disease. Adaptations of MM cells to hypoxic conditions in the BM have been shown to contribute significantly to MM progression, independently from the genetic predispositions of the tumor cells. Searching for consequences of hypoxia-induced adaptations in primary human MM cells, CD138-positive plasma cells freshly isolated from BM of patients with different disease stages, comprising MGUS, SMM, and MM, were analyzed by proteome profiling, which resulted in the identification of 6218 proteins. Results have been made fully accessible via ProteomeXchange with identifier PXD010600. Data previously obtained from normal primary B cells were included for comparative purposes. A principle component analysis revealed three clusters, differentiating B cells as well as MM cells corresponding to less and more advanced disease stages. Comparing these three clusters pointed to the alteration of pathways indicating adaptations to hypoxic stress in MM cells on disease progression. Protein regulations indicating immune evasion strategies of MM cells were determined, supported by immunohistochemical staining, as well as transcription factors involved in MM development and progression. Protein regulatory networks related to metabolic adaptations of the cells became apparent. Results were strengthened by targeted analyses of a selected panel of metabolites in MM cells and MM-associated fibroblasts. Based on our data, new opportunities may arise for developing therapeutic strategies targeting myeloma disease progression.

Leukemia multiclass assessment and classification from Microarray and RNA-seq technologies integration at gene expression level

In more recent years, a significant increase in the number of available biological experiments has taken place due to the widespread use of massive sequencing data. Furthermore, the continuous developments in the machine learning and in the high performance computing areas, are allowing a faster and more efficient analysis and processing of this type of data. However, biological information about a certain disease is normally widespread due to the use of different sequencing technologies and different manufacturers, in different experiments along the years around the world. Thus, nowadays it is of paramount importance to attain a correct integration of biologically-related data in order to achieve genuine benefits from them. For this purpose, this work presents an integration of multiple Microarray and RNA-seq platforms, which has led to the design of a multiclass study by collecting samples from the main four types of leukemia, quantified at gene expression. Subsequently, in order to find a set of differentially expressed genes with the highest discernment capability among different types of leukemia, an innovative parameter referred to as coverage is presented here. This parameter allows assessing the number of different pathologies that a certain gen is able to discern. It has been evaluated together with other widely known parameters under assessment of an ANOVA statistical test which corroborated its filtering power when the identified genes are subjected to a machine learning process at multiclass level. The optimal tuning of gene extraction evaluated parameters by means of this statistical test led to the selection of 42 highly relevant expressed genes. By the use of minimum-Redundancy Maximum-Relevance (mRMR) feature selection algorithm, these genes were reordered and assessed under the operation of four different classification techniques. Outstanding results were achieved by taking exclusively the first ten genes of the ranking into consideration. Finally, specific literature was consulted on this last subset of genes, revealing the occurrence of practically all of them with biological processes related to leukemia. At sight of these results, this study underlines the relevance of considering a new parameter which facilitates the identification of highly valid expressed genes for simultaneously discerning multiple types of leukemia.

Crosstalk between BCR-ABL and protease-activated receptor 1 (PAR1) suggests a novel target in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the presence of the Philadelphia chromosome, which generates the oncogene BCR-ABL1. Protease-activated receptor 1 (PAR1) is involved in tumor progression and angiogenesis. We have previously reported that PAR1 expression is elevated in human leukemias that display a more aggressive clinical behavior, including the blast crisis of CML. In this study, we analyzed the crosstalk between the oncoprotein BCR-ABL and PAR1 in CML. Leukemic cell lines transfected with the BCR-ABL1 oncogene showed significantly higher expression levels of PAR1 compared with that of wild-type counterparts. This phenomenon was reversed by treatment with tyrosine kinase inhibitors (TKIs). Conversely, treatment with the PAR1 antagonist SCH79797 inhibited BCR-ABL expression. The PAR1 antagonist induced apoptosis in a dose- and time-dependent manner. Higher vascular endothelial growth factor (VEGF) levels were observed in cells transfected with BCR-ABL1 than in their wild-type counterparts. VEGF expression was strongly inhibited after treatment with either TKIs or the PAR1 antagonist. Finally, we evaluated PAR1 expression in CML patients who were either in the blast or chronic phases and had either received TKI treatment or no treatment. A significant decrease in PAR1 expression was observed in treatment-responsive patients, as opposed to a significant increase in PAR1 expression levels in treatment-resistant patients. Patients classified as high risk according to the Sokal index showed higher PAR1 expression levels. Our results demonstrate the crosstalk between BCR-ABL and PAR1. These data may offer important insight into the development of new therapeutic strategies for CML.

Nuclear Export Inhibition for Pancreatic Cancer Therapy

Pancreatic cancer is a deadly disease that is resistant to most available therapeutics. Pancreatic cancer to date has no effective drugs that could enhance the survival of patients once their disease has metastasized. There is a need for the identification of novel actionable drug targets in this unusually recalcitrant cancer. Nuclear protein transport is an important mechanism that regulates the function of several tumor suppressor proteins (TSPs) in a compartmentalization-dependent manner. High expression of the nuclear exporter chromosome maintenance region 1 (CRM1) or exportin 1 (XPO1), a common feature of several cancers including pancreatic cancer, results in excessive export of critical TSPs to the incorrect cellular compartment, leading to their functional inactivation. Small molecule inhibitors of XPO1 can block this export, retaining very important and functional TSPs in the nucleus and leading to the effective killing of the cancer cells. This review highlights the current knowledge on the role of XPO1 in pancreatic cancer and how this serves as a unique and clinically viable target in this devastating and by far incurable cancer.