Cooperation of cytokine signaling with chimeric transcription factors in leukemogenesis: PML-retinoic acid receptor alpha blocks growth factor-mediated differentiation

Emerging In Vitro and In Vivo Models: Hope for the Better Understanding of Cancer Progression and Treatment

Various cancer models have been developed to aid the understanding of the underlying mechanisms of tumor development and evaluate the effectiveness of various anticancer drugs in preclinical studies. These models accurately reproduce the critical stages of tumor initiation and development to mimic the tumor microenvironment better. Using these models for target validation, tumor response evaluation, resistance modeling, and toxicity comprehension can significantly enhance the drug development process. Herein, various in vivo or animal models are presented, typically consisting of several mice and in vitro models ranging in complexity from transwell models to spheroids and CRISPR-Cas9 technologies. While in vitro models have been used for decades and dominate the early stages of drug development, they are still limited primary to simplistic tests based on testing on a single cell type cultivated in Petri dishes. Recent advancements in developing new cancer therapies necessitate the generation of complicated animal models that accurately mimic the tumor's complexity and microenvironment. Mice make effective tumor models as they are affordable, have a short reproductive cycle, exhibit rapid tumor growth, and are simple to manipulate genetically. Human cancer mouse models are crucial to understanding the neoplastic process and basic and clinical research improvements. The following review summarizes different in vitro and in vivo metastasis models, their advantages and disadvantages, and their ability to serve as a model for cancer research.

Down-regulating the expression of IL-3Rβ interfered with the proliferation, not differentiation in NB4 cells

The human IL-3 receptor is composed of both α and β subunits. In early studies, we showed that the level of IL-3Rβ expression was lower in patients with acute promyelocytic leukemia (APL) than healthy donors and patients in complete remission by real-time quantitative polymerase chain reaction (RT-qPCR). With the differentiation of cells, enhanced expression of IL-3Rβ was also observed in all-trans-retinoic acid (ATRA)-induced NB4 cells. To unravel the role of IL-3Rβ upregulation in NB4 cells induced with ATRA, we knocked down IL-3Rβ expression by RNA interference (RNAi). Knockdown of IL-3Rβ resulted in decreased proliferation in NB4 cells induced with or without ATRA, observed by cell growth curves, colony formation assays and cell cycle analysis. Surface expression of CD11b antigen and nitroblue tetrazolium (NBT) reduction assays were also carried out at different time points. However, no significant difference was observed between the experimental and control groups treated with ATRA. Other findings suggested that IL-3Rα was decreased in NB4-IL-3Rβ shRNA cells by western blot. Down-regulation of IL-3Rβ also caused a decrease in PML/RARα expression detected with RT-qPCR. Together, these results suggest that abnormalities of IL-3Rβ expression were observed in APL; knockdown of IL-3Rβ inhibited the proliferation of NB4 cells with or without ATRA, but no effect was detected in the cellular differentiation. When NB4 cells exposed to ATAR, the up-regulation of IL-3Rβ expression may contribute to the maintenance of proliferation rather than cell differentiation.

Non-germline genetically engineered mouse models for translational cancer research

Genetically engineered mouse models (GEMMs) of cancer have affected virtually all areas of cancer research. However, the accelerated discovery of new cancer genes emerging from large-scale cancer genomics and new chemical entities pouring from the drug discovery pipeline have strained the capacity of traditional germline mouse models to provide crucial insights. This Review introduces new approaches to modelling cancer, with emphasis on a growing collection of non-germline GEMMs (nGEMMs). These offer flexibility, speed and uniformity at reduced costs, thus paving the way for much needed throughput and practical preclinical therapeutic testing models.

Forced retinoic acid receptor alpha homodimers prime mice for APL-like leukemia

RARA becomes an acute promyelocytic leukemia (APL) oncogene by fusion with any of five translocation partners. Unlike RARalpha, the fusion proteins homodimerize, which may be central to oncogenic activation. This model was tested by replacing PML with dimerization domains from p50NFkappaB (p50-RARalpha) or the rapamycin-sensitive dimerizing peptide of FKBP12 (F3-RARalpha). The X-RARalpha fusions recapitulated in vitro activities of PML-RARalpha. For F3-RARalpha, these properties were rapamycin sensitive. Although in vivo the artificial fusions alone are poor initiators of leukemia, p50-RARalpha readily cooperates with an activated mutant CDw131 to induce APL-like disease. These results demonstrate that the dimerization interface of RARalpha fusion partners is a critical element in APL pathogenesis while pointing to other features of PML for enhancing penetrance and progression.

Animal models of acute myelogenous leukaemia - development, application and future perspectives

From the early inception of the transplant models through to contemporary genetic and xenograft models, evolution of murine leukaemic model systems have been critical to our general comprehension and treatment of cancer, and, more specifically, disease states such as acute myelogenous leukaemia (AML). However, even with modern advances in therapeutics and molecular diagnostics, the majority of AML patients die from their disease. Thus, in the absence of definitive in vitro models which precisely recapitulate the in vivo setting of human AMLs and failure of significant numbers of new drugs late in clinical trials, it is essential that murine AML models are developed to exploit more specific, targeted therapeutics. While various model systems are described and discussed in the literature from initial transplant models such as BNML and spontaneous murine leukaemia virus models, to the more definitive genetic and clinically significant NOD/SCID xenograft models, there exists no single compendium which directly assesses, reviews or compares the relevance of these models. Thus, the function of this article is to provide clinicians and experimentalists a chronological, comprehensive appraisal of all AML model systems, critical discussion on the elucidation of their roles in our understanding of AML and consideration to their efficacy in the development of AML chemotherapeutics.

Immunophenotypic features of acute myeloid leukemias overexpressing the interleukin 3 receptor alpha chain

In a previous study we have shown that the interleukin-3 receptor alpha chain (IL-3Ralpha) is over expressed in about 45% of acute myeloid leukemias (AMLs) and this phenomenon was associated with high blast cell counts at diagnosis, high rate of cycling of leukemic blasts and with a worse prognosis. Here we have investigated the immunophenotypic features of 125 AML patients subdivided into three groups (IL-3R(high), IL-3R(middle) and IL-3R(low)) according to the level of IL-3Ralpha expression. AMLs over expressing the IL-3Ralpha represent a subgroup of AMLs with a peculiar immunophenotype mainly consisting in the elevated expression of CD34 and several receptor membrane tyrosine kinases, such as c-kit and flt3, and in a usually low expression of myeloid-associated antigens such as CD11b, CD14 and CD15. These findings suggest that IL-3Ralpha + + + AMLs are blocked at an early stage of differentiation and express at elevated levels several growth factor receptors. It is proposed that these findings may further help to understand the mechanisms involved in the development of high-risk acute leukemias.

Retinoic acid receptors and cancers

Studies utilizing experimental animals, epidemiological approaches, cellular models, and clinical trials all provide evidence that retinoic acid and some of its synthetic derivatives (retinoids) are useful pharmacological agents in cancer therapy and prevention. In this chapter, we first review the current knowledge of retinoic acid receptors (RARs) and their role in mediating the actions of retinoic acid. We then focus on a discussion of RARalpha and acute promyelocytic leukemia followed by a discussion of the role of RARs, in particular RARbeta expression, in other cancer types. Loss of normal RAR function in the presence of physiological levels of RA (either due to alterations in the protein structure or level of expression) is associated with a variety of different cancers. In some cases treatment with pharmacological doses of RA can be effective.

Effects of the leukemia-associated AML1-ETO protein on hematopoietic stem and progenitor cells

Insights into the pathogenesis of human leukemia have relied heavily on studies of the identified chromosomal translocations found in this group of malignant diseases. Acquired, balanced translocations in acute myelogenous leukemia (AML) generally involve transcriptional regulatory genes, whereas in the myeloproliferative disorders tyrosine kinases are frequently involved. These rearrangements alter the function of at least one and often both of the involved genes. In this review, we focus on the AML1-ETO (a.k.a. RUNX1-ETO) fusion protein, which is found in t(8;21)+ AML. Expression of AML1-ETO in human hematopoietic stem cells (HSCs) preferentially enhances their maintenance, as opposed to their differentiation. The direct effects of AML1-ETO on human and murine HSCs, and the potentially cooperating events that may contribute to its leukemogenic properties, are discussed.

Interleukin-3 receptor in acute leukemia

Recent studies indicate that abnormalities of the interleukin-3 receptor (IL-3R) are frequently observed in acute myeloid leukemias (AMLs) and may contribute to the proliferative advantage of leukemic blasts. This review analyzes the evidences indicating that the IL-3R represents one of the target molecules involved in the stimulation of proliferation of AMLs, and the overexpression of the IL-3Ralpha chain may represent one of the mechanisms contributing to the development of a highly malignant leukemic phenotype. Furthermore, there is evidence that the IL-3Ralpha is a marker of leukemic stem cells, at variance with normal stem cells that are IL-3Ralpha-. Finally, the IL-3R may represent an important target for the development of new antileukemic drugs.