Aurora A Kinase Inhibitor AKI603 Induces Cellular Senescence in Chronic Myeloid Leukemia Cells Harboring T315I Mutation

Aurora kinases signaling in cancer: from molecular perception to targeted therapies

Aurora kinases, AURKA, AURKB, and AURKC, are serine/threonine kinases that play a vital role in regulating cell division and mitosis, particularly in the separation of chromosomes. These kinases are often overexpressed in human tumor cell lines, indicating their potential involvement in tumorigenesis. Preliminary evidence supports the use of Aurora kinase inhibitors for certain types of tumors, several AURKs inhibitors are currently under phase I and II trials. As a result, there is a growing interest in identifying small-molecule Aurora kinase inhibitors to develop as anti-cancer agents. The regulation of the cell cycle, including mitosis, is increasingly recognized as a key target in the fight against various forms of cancer. Novel drugs are being designed to inhibit the function of regulatory proteins, such as Aurora kinases, with the goal of creating personalized treatments. This review summarizes the biology of Aurora kinases in the context of cancer, integrating both preclinical and clinical data. It discusses the challenges and opportunities associated with using Aurora kinases to enhance cancer treatment. Future directions for Aurora kinase-based therapies include developing more selective inhibitors that minimize off-target effects and improve therapeutic efficacy. Researchers are also exploring combination therapies that use Aurora kinase inhibitors alongside other targeted treatments to overcome resistance and improve patient outcomes. Additionally, advancements in biomarker discovery are expected to facilitate the identification of patients most likely to benefit from Aurora kinase-targeted therapies, paving the way for more personalized approaches to cancer treatment.

Regulation of cellular senescence in tumor progression and therapeutic targeting: mechanisms and pathways

Cellular senescence, a stable state of cell cycle arrest induced by various stressors or genomic damage, is recognized as a hallmark of cancer. It exerts a context-dependent dual role in cancer initiation and progression, functioning as a tumor suppressor and promoter. The complexity of senescence in cancer arises from its mechanistic diversity, potential reversibility, and heterogeneity. A key mediator of these effects is the senescence-associated secretory phenotype (SASP), a repertoire of bioactive molecules that influence tumor microenvironment (TME) remodeling, modulate cancer cell behavior, and contribute to therapeutic resistance. Given its intricate role in cancer biology, senescence presents both challenges and opportunities for therapeutic intervention. Strategies targeting senescence pathways, including senescence-inducing therapies and senolytic approaches, offer promising avenues for cancer treatment. This review provides a comprehensive analysis of the regulatory mechanisms governing cellular senescence in tumors. We also discuss emerging strategies to modulate senescence, highlighting novel therapeutic opportunities. A deeper understanding of these processes is essential for developing precision therapies and improving clinical outcomes.

Senolytics: charting a new course or enhancing existing anti-tumor therapies?

Cell senescence is a natural response within our organisms. Initially, it was considered an effective anti-tumor mechanism. However, it is now believed that while cell senescence initially acts as a robust barrier against tumor initiation, the subsequent accumulation of senescent cells can paradoxically promote cancer recurrence and cause damage to neighboring tissues. This intricate balance between cell proliferation and senescence plays a pivotal role in maintaining tissue homeostasis. Moreover, senescence cells secrete many bioactive molecules collectively termed the senescence-associated secretory phenotype (SASP), which can induce chronic inflammation, alter tissue architecture, and promote tumorigenesis through paracrine signaling. Among the myriads of compounds, senotherapeutic drugs have emerged as exceptionally promising candidates in anticancer treatment. Their ability to selectively target senescent cells while sparing healthy tissues represents a paradigm shift in therapeutic intervention, offering new avenues for personalized oncology medicine. Senolytics have introduced new therapeutic possibilities by enabling the targeted removal of senescent cells. As standalone agents, they can clear tumor cells in a senescent state and, when combined with chemo- or radiotherapy, eliminate residual senescent cancer cells after treatment. This dual approach allows for the intentional use of lower-dose therapies or the removal of unintended senescent cells post-treatment. Additionally, by targeting non-cancerous senescent cells, senolytics may help reduce tumor formation risk, limit recurrence, and slow disease progression. This article examines the mechanisms of cellular senescence, its role in cancer treatment, and the importance of senotherapy, with particular attention to the therapeutic potential of senolytic drugs.

Remodeling of tumor microenvironment by cellular senescence and immunosenescence in cervical cancer

Cellular senescence is a response to various stress signals, which is characterized by stable cell cycle arrest, alterations in cellular morphology, metabolic reprogramming and production of senescence-associated secretory phenotype (SASP). When it occurs in the immune system, it is called immunosenescence. Cervical cancer is a common gynecological malignancy, and cervical cancer screening is generally recommended before the age of 65. Elderly women (≥65 years) are more often diagnosed with advanced disease and have poorer prognosis compared to younger patients. Despite extensive research, the tumor microenvironment requires more in-depth exploration, particularly in elderly patients. In cervical cancer, senescent cells have a double-edged sword effect on tumor progression. Induction of preneoplastic cell senescence prevents tumor initiation, and several treatment approaches of cervical cancer act in part by inducing cancer cell senescence. However, senescent immune cell populations within the tumor microenvironment facilitate tumor development, recurrence, treatment resistance, etc. Amplification of beneficial effects and inhibition of aging-related pro-tumorigenic pathways contribute to improving antitumor effects. This review discusses senescent cancer and immune cells present in the tumor microenvironment of cervical cancer and how these senescent cells and their SASP remodel the tumor microenvironment, influence antitumor immunity and tumor initiation and development. Moreover, we discuss the significance of senotherapeutics that enable to eliminate senescent cells and prevent tumor progression and development through improving antitumor immunity and affecting the tumor microenvironment.

Aurora B inhibitors promote RB hypophosphorylation and senescence independent of p53-dependent CDK2/4 inhibition

Aurora B kinase (AURKB) inhibitors have been trialled in a range of different tumour types but are not approved for any indication. Expression of the human papilloma virus (HPV) oncogenes and loss of retinoblastoma (RB) protein function has been reported to increase sensitivity to AURKB inhibitors but the mechanism of their contribution to sensitivity is poorly understood. Two commonly reported outcomes of AURKB inhibition are polyploidy and senescence, although their relationship is unclear. Here we have investigated the major cellular targets of the HPV E6 and E7, p53 and RB, to determine their contribution to AURKB inhibitor induced polyploidy and senescence. We demonstrate that polyploidy is a universal feature of AURKB inhibitor treatment in all cell types including normal primary cells, but the subsequent outcomes are controlled by RB and p53. We demonstrate that p53 by regulating p21 expression is required for an initial cell cycle arrest by inhibiting both CDK2 and CDK4 activity, but this arrest is only triggered after cells have undergone two failed mitosis and cytokinesis. However, cells can enter senescence in the absence of p53. RB is essential for AURKB inhibitor-induced senescence. AURKB inhibitor induces rapid hypophosphorylation of RB independent of inhibition of CDK2 or CDK4 kinases and p53. This work demonstrates that p53 activation determines the timing of senescence onset, but RB is indispensable for senescence.

Promoting reactive oxygen species accumulation to overcome tyrosine kinase inhibitor resistance in cancer

BACKGROUND

In tumor treatment, protein tyrosine kinase inhibitors (TKIs) have been extensively utilized. However, the efficacy of TKI is significantly compromised by drug resistance. Consequently, finding an effective solution to overcome TKI resistance becomes crucial. Reactive oxygen species (ROS) are a group of highly active molecules that play important roles in targeted cancer therapy including TKI targeted therapy. In this review, we concentrate on the ROS-associated mechanisms of TKI lethality in tumors and strategies for regulating ROS to reverse TKI resistance in cancer.

MAIN BODY

Elevated ROS levels often manifest during TKI therapy in cancers, potentially causing organelle damage and cell death, which are critical to the success of TKIs in eradicating cancer cells. However, it is noteworthy that cancer cells might initiate resistance pathways to shield themselves from ROS-induced damage, leading to TKI resistance. Addressing this challenge involves blocking these resistance pathways, for instance, the NRF2-KEAP1 axis and protective autophagy, to promote ROS accumulation in cells, thereby resensitizing drug-resistant cancer cells to TKIs. Additional effective approaches inducing ROS generation within drug-resistant cells and providing exogenous ROS stimulation.

CONCLUSION

ROS play pivotal roles in the eradication of tumor cells by TKI. Harnessing the accumulation of ROS to overcome TKI resistance is an effective and widely applicable approach.

EZH2 inhibition induces senescence via ERK1/2 signaling pathway in multiple myeloma

Epigenetic modifications play an important role in cellular senescence, and enhancer of zeste homolog 2 (EZH2) is a key methyltransferase involved in epigenetic remodeling in multiple myeloma (MM) cells. We have previously demonstrated that GSK126, a specific EZH2 inhibitor, exhibits anti-MM therapeutic efficacy and safety in vivo and in vitro; however, its specific mechanism remains unclear. This study shows that GSK126 induces cellular senescence in MM, which is characterized by the accumulation of senescence-associated heterochromatin foci (SAHF) and p21, and increased senescence-associated β galactosidase activity. Furthermore, EZH2 is inhibited in ribonucleotide reductase regulatory subunit M2 (RRM2)-overexpressing OCI-MY5 and RPMI-8226 cells. RRM2 overexpression inhibits the methyltransferase function of EZH2 and promotes its degradation through the ubiquitin-proteasome pathway, thereby inducing cellular senescence. In this senescence model, Lamin B1, a key component of the nuclear envelope and a marker of senescence, does not decrease but instead undergoes aberrant accumulation. Meanwhile, phosphorylation of extracellular signal-regulated protein kinase (ERK1/2) is significantly increased. The inhibition of ERK1/2 phosphorylation in turn partially restores Lamin B1 level and alleviates senescence. These findings suggest that EZH2 inhibition increases Lamin B1 level and induces senescence by promoting ERK1/2 phosphorylation. These data indicate that EZH2 plays an important role in MM cellular senescence and provide insights into the relationships among Lamin B1, p-ERK1/2, and cellular senescence.

AS1041, a novel derivative of marine natural compound Aspergiolide A, induces senescence of leukemia cells via oxidative stress-induced DNA damage and BCR-ABL degradation

Chronic myelogenous leukemia (CML) is characterized by the constitutive activation of BCR-ABL tyrosine kinase. Imatinib was approved for CML therapy, however, BCR-ABL-dependent drug resistance, especially BCR-ABL-T315I mutation, restricts its clinical application. In this study, we reported anthraquinone lactone AS1041, a synthesized derivative of marine natural compound Aspergiolide A, showed anti-leukemia effect in vitro and in vivo by promoting cell senescence. Mechanistic study revealed the pro-senescence effect of AS1041 was dependent on oxidative stress-induced DNA damage, and the resultant activation of P53/P21 and P16INK4a/Rb. Also, AS1041 promoted ubiquitin proteasome system (UPS)-mediated BCR-ABL degradation, which also contributed to AS1041-induced senescence. In vivo, AS1041-induced senescence promoted tumor growth inhibition. In summary, the in vitro and in vivo antitumor effect of AS1041 suggests it can serve as a pro-senescence agent for alternative antileukemia therapy and imatinib-resistant cancer therapy by enhancing cellular oxidative stress and BCR-ABL degradation.

Assessment of cell cycle progression and mitotic slippage by videomicroscopy

Senescence is a state of irreversible cell cycle arrest accompanied by the acquisition of the senescence-associated secretory phenotype (SASP), which is activated in response to a variety of damaging stimuli, including genotoxic therapy. Accumulating evidence indicates that mitotic stress also promotes entry into senescence. This occurs via a mechanism involving defective mitoses and mitotic arrest, followed by abortion of cell division and slippage in the G1 phase. In this process, mitotic slippage leads to the generation of senescent cells characterized by a large cell body and a multinucleated and/or enlarged nuclear size. Here, we provide a detailed protocol for the assessment of cell proliferation and mitotic slippage in colorectal cancer cells upon pharmacological inhibition of the mitotic kinesin KIF11, best known as EG5. This approach can be used for preliminary characterization of senescence induction by therapeutics, but requires validation with standard senescence assays.

The promotion action of AURKA on post-ischemic angiogenesis in diabetes-related limb ischemia

Background

Diabetes-related limb ischemia is a challenge for lower extremity amputation. Aurora Kinase A (AURKA) is an essential serine/threonine kinase for mitosis, while its role in limb ischemia remains unclear.

Method

Human microvascular endothelial cells (HMEC-1) were cultured in high glucose (HG, 25 mmol/L d-glucose) and no additional growth factors (ND) medium to mimic diabetes and low growth factors deprivation as in vitro model. Diabetic C57BL/6 mice were induced by streptozotocin (STZ) administration. After seven days, ischemia was surgically performed by left unilateral femoral artery ligation on diabetic mice. The vector of adenovirus was utilized to overexpress AURKA in vitro and in vivo.

Results

In our study, HG and ND-mediated downregulation of AURKA impaired the cell cycle progression, proliferation, migration, and tube formation ability of HMEC-1, which were rescued by overexpressed AURKA. Increased expression of vascular endothelial growth factor A (VEGFA) induced by overexpressed AURKA were likely regulatory molecules that coordinate these events. Mice with AURKA overexpression exhibited improved angiogenesis in response to VEGF in Matrigel plug assay, with increased capillary density and hemoglobin content. In diabetic limb ischemia mice, AURKA overexpression rescued blood perfusion and motor deficits, accompanied by the recovery of gastrocnemius muscles observed by H&E staining and positive Desmin staining. Moreover, AURKA overexpression rescued diabetes-related impairment of angiogenesis, arteriogenesis, and functional recovery in the ischemic limb. Signal pathway results revealed that VEGFR2/PI3K/AKT pathway might be involved in AURKA triggered angiogenesis procedure. In addition, AURKA overexpression impeded oxidative stress and subsequent following lipid peroxidation both in vitro and in vivo, indicating another protective mechanism of AURKA function in diabetic limb ischemia. The changes in lipid peroxidation biomarkers (lipid ROS, GPX4, SLC7A11, ALOX5, and ASLC4) in in vitro and in vivo were suggestive of the possible involvement of ferroptosis and interaction between AUKRA and ferroptosis in diabetic limb ischemia, which need further investigation.

Conclusions

These results implicated a potent role of AURKA in diabetes-related impairment of ischemia-mediated angiogenesis and implied a potential therapeutic target for ischemic diseases of diabetes.

Therapy Resistance and Disease Progression in CML: Mechanistic Links and Therapeutic Strategies

PURPOSE OF REVIEW

Despite the adoption of tyrosine kinases inhibitors (TKIs) as molecular targeted therapy in chronic myeloid leukemia, some patients do not respond to treatment and even experience disease progression. This review aims to give a broad summary of advances in understanding of the mechanisms of therapy resistance, as well as management strategies that may overcome or prevent the emergence of drug resistance. Ultimately, the goal of therapy is the cure of CML, which will also require an increased understanding of the leukemia stem cell (LSC).

RECENT FINDINGS

Resistance to tyrosine kinase inhibitors stems from a range of possible causes. Mutations of the BCR-ABL1 fusion oncoprotein have been well-studied. Other causes range from cell-intrinsic factors, such as the inherent resistance of primitive stem cells to drug treatment, to mechanisms extrinsic to the leukemic compartment that help CML cells evade apoptosis. There exists heterogeneity in TKI response among different hematopoietic populations in CML. The abundances of these TKI-sensitive and TKI-insensitive populations differ from patient to patient and contribute to response heterogeneity. It is becoming clear that targeting the BCR-ABL1 kinase through TKIs is only one part of the equation, and TKI usage alone may not cure the majority of patients with CML. Considerable effort should be devoted to targeting the BCR-ABL1-independent mechanisms of resistance and persistence of CML LSCs.

A Temporal PROTAC Cocktail-Mediated Sequential Degradation of AURKA Abrogates Acute Myeloid Leukemia Stem Cells

AURKA is a potential kinase target in various malignancies. The kinase-independent oncogenic functions partially disclose the inadequate efficacy of the kinase inhibitor in a Phase III clinical trial. Simultaneously targeting the catalytic and noncatalytic functions of AURKA may be a feasible approach. Here, a set of AURKA proteolysis targeting chimeras (PROTACs) are developed. The CRBN-based dAurA383 preferentially degrades the highly abundant mitotic AURKA, while cIAP-based dAurA450 degrades the lowly abundant interphase AURKA in acute myeloid leukemia (AML) cells. The proteomic and transcriptomic analyses indicate that dAurA383 triggers the "mitotic cell cycle" and "stem cell" processes, while dAurA450 inhibits the "MYC/E2F targets" and "stem cell" processes. dAurA383 and dAurA450 are combined as a PROTAC cocktail. The cocktail effectively degrades AURKA, relieves the hook effect, and synergistically inhibits AML stem cells. Furthermore, the PROTAC cocktail induces AML regression in a xenograft mouse model and primary patient blasts. These findings establish the PROTAC cocktail as a promising spatial-temporal drug administration strategy to sequentially eliminate the multifaceted functions of oncoproteins, relieve the hook effect, and prevent cancer stem cell-mediated drug resistance.

Antiproliferative Activity of a New Quinazolin-4(3H)-One Derivative via Targeting Aurora Kinase A in Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is the most common lung cancer subtype. Although chemotherapy and targeted therapy are used for the treatment of patients with NSCLC, the survival rate remains very low. Recent findings suggested that aurora kinase A (AKA), a cell cycle regulator, is a potential target for NSCLC therapy. Previously, we reported that a chemical entity of quinazolin-4(3H)-one represents a new template for AKA inhibitors, with antiproliferative activity against cancer cells. A quinazolin-4(3H)-one derivative was further designed and synthesized in order to improve the pharmacokinetic properties and antiproliferation activity against NSCLC cell lines. The derivative, BIQO-19 (Ethyl 6-(4-oxo-3-(pyrimidin-2-ylmethyl)-3,4-dihydroquinazolin-6-yl)imidazo [1,2-a]pyridine-2-carboxylate), exhibited improved solubility and antiproliferative activity in NSCLC cells, including epidermal growth factor receptor–tyrosine kinase inhibitor (EGFR-TKI)-resistant NSCLC cells. BIQO-19 effectively inhibited the growth of the EGFR-TKI-resistant H1975 NSCLC cells, with the suppression of activated AKA (p-AKA) expression in these cells. The inhibition of AKA by BIQO-19 significantly induced G₂/M phase arrest and subsequently evoked apoptosis in H1975 cells. In addition, the combination of gefitinib and BIQO-19 exhibited synergistic antiproliferative activity in NSCLC cells. These findings suggest the potential of BIQO-19 as a novel therapeutic agent for restoring the sensitivity of gefitinib in EGFR-TKI-resistant NSCLC cells.

Aurora kinase a inhibitor MLN8237 suppresses pancreatic cancer growth

Pancreatic ductal adenocarcinoma (PDAC) is notorious for high mortality due to limited options of appropriate chemotherapy drugs. Here we report that Aurora kinase-A expression is elevated in both human and mouse PDAC samples. MLN8237, an inhibitor of Aurora kinase-A, efficiently reduced the proliferation and motility of PDAC cells in vitro as well as tumor growth in orthotropic xenograft model and genetic pancreatic cancer animal models (p53/LSL/Pdx-Cre mice) in vivo. MLN8237 exhibited tumor inhibitory effect through inhibiting proliferation and migration, and inducing apoptosis and senescence. These results provide the molecular basis for a novel chemotherapy strategy for PDAC patients.

Targeting tumor cell senescence and polyploidy as potential therapeutic strategies

Senescence is a unique state of growth arrest that develops in response to a plethora of cellular stresses, including replicative exhaustion, oxidative injury, and genotoxic insults. Senescence has been implicated in the pathogenesis of multiple aging-related pathologies, including cancer. In cancer, senescence plays a dual role, initially acting as a barrier against tumor progression by enforcing a durable growth arrest in premalignant cells, but potentially promoting malignant transformation in neighboring cells through the secretion of pro-tumorigenic drivers. Moreover, senescence is induced in tumor cells upon exposure to a wide variety of conventional and targeted anticancer drugs (termed Therapy-Induced Senescence-TIS), representing a critical contributing factor to therapeutic outcomes. As with replicative or oxidative senescence, TIS manifests as a complex phenotype of macromolecular damage, energetic dysregulation, and altered gene expression. Senescent cells are also frequently polyploid. In vitro studies have suggested that polyploidy may confer upon senescent tumor cells the ability to escape from growth arrest, thereby providing an additional avenue whereby tumor cells escape the lethality of anticancer treatment. Polyploidy in tumor cells is also associated with persistent energy production, chromatin remodeling, self-renewal, stemness and drug resistance - features that are also associated with escape from senescence and conversion to a more malignant phenotype. However, senescent cells are highly heterogenous and can present with variable phenotypes, where polyploidy is one component of a complex reversion process. Lastly, emerging efforts to pharmacologically target polyploid tumor cells might pave the way towards the identification of novel targets for the elimination of senescent tumor cells by the incorporation of senolytic agents into cancer therapeutic strategies.

Exploiting senescence for the treatment of cancer

Senescence is a cellular response to a variety of stress signals that is characterized by a stable withdrawal from the cell cycle and major changes in cell morphology and physiology. While most research on senescence has been performed on non-cancer cells, it is evident that cancer cells can also mount a senescence response. In this Review, we discuss how senescence can be induced in cancer cells. We describe the distinctive features of senescent cancer cells and how these changes in cellular physiology might be exploited for the selective eradication of these cells (senolysis). We discuss activation of the host immune system as a particularly attractive way to clear senescent cancer cells. Finally, we consider the challenges and opportunities provided by a 'one-two punch' sequential treatment of cancer with pro-senescence therapy followed by senolytic therapy.

Expression of proliferation-related genes in BM-MSC-treated ALL cells in hypoxia condition is regulated under the influence of epigenetic factors in-vitro

Mesenchymal stem cells affect ALL cell biology under hypoxic conditions. We studied survival, proliferation, expression, and promoter methylation levels of essential genes involved in expanding MOLT-4 cells co-cultured with BM-MSC under the hypoxic condition. Here, MOLT-4 cells were co-cultured with BMMSCs under hypoxic conditions. First, the apoptosis rate was evaluated by Flow cytometry. Then, MOLT-4 cells' proliferation rate was assessed using MTT assay, and the expressions and methylation rates of genes were determined by qRT-PCR and MS-qPCR, respectively. The results showed that although MOLT-4 cells proliferation and survival rates were reduced under hypoxic conditions, this reduction was not statistically significant. Also, we showed that hypoxic conditions caused upregulation of candidate genes and affected their methylation status. Besides, it was revealed that Pontin was downregulated, while KDM3A, SKP2, and AURKA had an upward trend in the presence of MOLT-4 cells plus BM-MSC. The co-culture of leukemia cells with BMMSCs under hypoxic conditions may be a potential therapeutic approach for ALL.

HNRNPH1 Is a Novel Regulator Of Cellular Proliferation and Disease Progression in Chronic Myeloid Leukemia

RNA binding proteins act as essential modulators in cancers by regulating biological cellular processes. Heterogeneous nuclear ribonucleoprotein H1 (HNRNPH1), as a key member of the heterogeneous nuclear ribonucleoproteins family, is frequently upregulated in multiple cancer cells and involved in tumorigenesis. However, the function of HNRNPH1 in chronic myeloid leukemia (CML) remains unclear. In the present study, we revealed that HNRNPH1 expression level was upregulated in CML patients and cell lines. Moreover, the higher level of HNRNPH1 was correlated with disease progression of CML. In vivo and in vitro experiments showed that knockdown of HNRNPH1 inhibited cell proliferation and promoted cell apoptosis in CML cells. Importantly, knockdown of HNRNPH1 in CML cells enhanced sensitivity to imatinib. Mechanically, HNRNPH1 could bind to the mRNA of PTPN6 and negatively regulated its expression. PTPN6 mediated the regulation between HNRNPH1 and PI3K/AKT activation. Furthermore, the HNRNPH1–PTPN6–PI3K/AKT axis played a critical role in CML tumorigenesis and development. The present study first investigated the deregulated HNRNPH1–PTPN6–PI3K/AKT axis moderated cell growth and apoptosis in CML cells, whereby targeting this pathway may be a therapeutic CML treatment.

Biological functions of therapy-induced senescence in cancer

Therapy-induced cellular senescence is a state of stable growth arrest induced by common cancer treatments such as chemotherapy and radiation. In an oncogenic context, therapy-induced senescence can have different consequences. By blocking cellular proliferation and by facilitating immune cell infiltration, it functions as tumor suppressive mechanism. By fueling the proliferation of bystander cells and facilitating metastasis, it acts as a tumor promoting factor. This dual role is mainly attributed to the differential expression and secretion of a set of pro-inflammatory cytokines and tissue remodeling factors, collectively known as the Senescence-Associated Secretory Phenotype (SASP). Here, we describe cell-autonomous and non-cell-autonomous mechanisms that senescent cells activate in response to chemotherapy and radiation leading to tumor suppression and tumor promotion. We present the current state of knowledge on the stimuli that affect the activation of these opposing mechanisms and the effect of senescent cells on their micro-environment eg. by regulating the functions of immune cells in tumor clearance as well as strategies to eliminate senescent tumor cells before exerting their deleterious side-effects.

The Discovery of Novel BCR-ABL Tyrosine Kinase Inhibitors Using a Pharmacophore Modeling and Virtual Screening Approach

Chronic myelogenous leukemia (CML) typically results from a reciprocal translocation between chromosomes 9 and 22 to produce the bcr-abl oncogene that when translated, yields the p210 BCR-ABL protein in more than 90% of all CML patients. This protein has constitutive tyrosine kinase activity that activates numerous downstream pathways that ultimately produces uncontrolled myeloid proliferation. Although the use of the BCR-ABL tyrosine kinase inhibitors (TKIs), such as imatinib, nilotinib, dasatinib, bosutinib, and ponatinib have increased the overall survival of CML patients, their use is limited by drug resistance and severe adverse effects. Therefore, there is the need to develop novel compounds that can overcome these problems that limit the use of these drugs. Therefore, in this study, we sought to find novel compounds using Hypogen and Hiphip pharmacophore models based on the structures of clinically approved BCR-ABL TKIs. We also used optimal pharmacophore models such as three-dimensional queries to screen the ZINC database to search for potential BCR-ABL inhibitors. The hit compounds were further screened using Lipinski’s rule of five, ADMET and molecular docking, and the efficacy of the hit compounds was evaluated. Our in vitro results indicated that compound ZINC21710815 significantly inhibited the proliferation of K562, BaF3/WT, and BaF3/T315I leukemia cells by inducing cell cycle arrest. The compound ZINC21710815 decreased the expression of p-BCR-ABL, STAT5, and Crkl and produced apoptosis and autophagy. Our results suggest that ZINC21710815 may be a potential BCR-ABL inhibitor that should undergo in vivo evaluation.

Cellular senescence and hematological malignancies: From pathogenesis to therapeutics

Cellular senescence constitutes a permanent state of cell cycle arrest in proliferative cells induced by different stresses. The exploration of tumor pathogenesis and therapies has been a research hotspot in recent years. Cellular senescence is a significant mechanism to prevent the proliferation of potential tumor cells, but it can also promote tumor growth. Increasing evidence suggests that cellular senescence is involved in the pathogenesis and development of hematological malignancies, including leukemia, myelodysplastic syndrome (MDS) and multiple myeloma (MM). Cellular senescence is associated with functional decline of hematopoietic stem cells (HSCs) and increased risk of hematological malignancies. Moreover, the bone marrow (BM) microenvironment has a crucial regulatory effect in the process of these diseases. The senescence-associated secretory phenotype (SASP) in the BM microenvironment establishes a protumor environment that supports the proliferation and survival of tumor cells. Therefore, a series of therapeutic strategies targeting cellular senescence have been gradually developed, including the induction of cellular senescence and elimination of senescent cells. This review systematically summarizes the emerging information describing the roles of cellular senescence in tumorigenesis and potential clinical applications, which may be beneficial for designing rational therapeutic strategies for various hematopoietic malignancies.

A Novel Aurora Kinase Inhibitor Attenuates Leukemic Cell Proliferation Induced by Mesenchymal Stem Cells

Acute myeloid leukemia (AML) mesenchymal stem cells (MSCs) play an essential role in protecting leukemic cells from chemotherapeutic agents through activating a wide range of adhesion molecules and cytokines. Thus, more attention should be paid to attenuate the protection of leukemic cells by MSCs. By examining the gene expression files of MSCs from healthy donors and AML patients through high-throughput microarrays, we found that interleukin (IL)-6 was an important cytokine secreted by AML MSCs to protect leukemic cells, contributing to disease progression. Strikingly, Aurora A (AURKA) was activated by IL-6, offering a new target to interfere with leukemia. Importantly, a novel AURKA inhibitor, PW21, showed excellent AURKA kinase inhibitory activities and attenuated the interaction of leukemic cells and the microenvironment. PW21 inhibited MSC-induced cell proliferation, colony formation, and migration, and it induced cell apoptosis. Mechanically, PW21 could inhibit IL-6 secreted by MSCs. Moreover, we found that PW21 displayed a strong anti-leukemia effect on non-obese diabetic (NOD)-severe combined immunodeficiency (SCID) and murine MLL-AF9 leukemic models. PW21 significantly prolonged the survival of leukemic mice and eliminated the leukemic progenitor cells. AURKA inhibitor PW21 could provide a new approach for treatment of leukemia through blocking the protection by the leukemic microenvironment in clinical application.

Aurora kinase inhibitor restrains STAT5-activated leukemic cell proliferation by inducing mitochondrial impairment

Current chemotherapy regimens on acute myeloid leukemia (AML) still have some drawbacks, such as intolerance and drug resistance, which calls need for the development of targeted therapy. Signal transducer and activator of transcription 5 (STAT5) is often overexpressed or abnormally activated in leukemia and involved in cell self-renewal, proliferation, and stress adaptation. Overexpressed Aurora A (AURKA) is associated with poor prognosis in tumors, and inhibitors against AURKA are already in clinical trials. However, it has rarely been reported whether AURKA inhibitors restrain STAT5-activated leukemia cells. In this study, we constructed STAT5 constitutively activated (cS5) cells and found that STAT5 promoted cell proliferation and colony formation. Moreover, cS5 cells showed elevated reactive oxygen species (ROS) and adenosine triphosphate (ATP) levels, which indicated higher mitochondrial metabolism in cS5 cells. A novel AURKA inhibitor AKI604 was synthesized and showed significant inhibitory effects to the proliferation and colony formation in both STAT5 constitutively activated and nonactivated AML cells. AKI604 induced mitochondrial impairment, leading to the disruption of mitochondrial membrane potential and the elevation of ROS as well as cellular calcium (Ca²⁺ ) levels. AKI604 could also decline basal oxygen consumption rate and ATP biosynthesis, indicating the damage of oxidative phosphorylation. Furthermore, AKI604 exhibited significant antitumor effect in the HL-60 cS5 xenograft model of the BALB/c nude mice without an obvious influence on mice body weight and other healthy indicators. This study suggested that AKI604 was a potential strategy to overcome STAT5-induced leukemic proliferation in AML treatment by inducing mitochondrial impairment.

Insights into the non-mitotic functions of Aurora kinase A: more than just cell division

AURKA is a serine/threonine kinase overexpressed in several cancers. Originally identified as a protein with multifaceted roles during mitosis, improvements in quantitative microscopy uncovered several non-mitotic roles as well. In physiological conditions, AURKA regulates cilia disassembly, neurite extension, cell motility, DNA replication and senescence programs. In cancer-like contexts, AURKA actively promotes DNA repair, it acts as a transcription factor, promotes cell migration and invasion, and it localises at mitochondria to regulate mitochondrial dynamics and ATP production. Here we review the non-mitotic roles of AURKA, and its partners outside of cell division. In addition, we give an insight into how structural data and quantitative fluorescence microscopy allowed to understand AURKA activation and its interaction with new substrates, highlighting future developments in fluorescence microscopy needed to better understand AURKA functions in vivo. Last, we will recapitulate the most significant AURKA inhibitors currently in clinical trials, and we will explore how the non-mitotic roles of the kinase may provide new insights to ameliorate current pharmacological strategies against AURKA overexpression.

Targeted blocking of miR328 lysosomal degradation with alkalized exosomes sensitizes the chronic leukemia cells to imatinib

Imatinib resistance remains the biggest hurdle for the treatment of chronic myeloid leukemia (CML), with the underlying mechanisms not fully understood. In this study, we found that miR328 significantly and strikingly decreased among other miRNA candidates during the induction of imatinib resistance. Overexpression of miR328 sensitized resistant cells to imatinib via post-transcriptionally decreasing ABCG2 expression, while miR328 knockdown conferred imatinib resistance in parental K562 cells. Moreover, miR328 was found selectively degraded in the lysosomes of K562R cells, as inhibition of lysosome with chloroquine restored miR328 expression and increased sensitivity to imatinib. Moreover, delivery of alkalized exosomes increased endogenous miR328 expression. Compared with the corresponding controls, the alkalized exosomes with or without miR328 sensitized the chronic leukemia cells to imatinib. Taken together, our study has revealed that lysosomal clearance of miR328 in imatinib-resistant cells at least partially contributes to the drug resistance, while delivery of alkalized exosomes would sensitize the chromic leukemia cells to imatinib.

A Ploidy Increase Promotes Sensitivity of Glioma Stem Cells to Aurora Kinases Inhibition

Glioma stem cells account for glioblastoma relapse and resistance to conventional therapies, and protein kinases, involved in the regulation of the mitotic machinery (i.e., Aurora kinases), have recently emerged as attractive therapeutic targets. In this study, we investigated the effect of Aurora kinases inhibition in five glioma stem cell lines isolated from glioblastoma patients. As expected, cell lines responded to the loss of Aurora kinases with cytokinesis failure and mitotic exit without cell division. Surprisingly, this resulted in a proliferative arrest in only two of the five cell lines. These sensitive cell lines entered a senescent/autophagic state following aberrant mitotic exit, while the non-sensitive cell lines continued to proliferate. This senescence response did not correlate with TP53 mutation status but only occurred in the cell lines with the highest chromosome content. Repeated rounds of Aurora kinases inhibition caused a gradual increase in chromosome content in the resistant cell lines and eventually caused a similar senescence response and proliferative arrest. Our results suggest that a ploidy threshold is the main determinant of Aurora kinases sensitivity in TP53 mutant glioma stem cells. Thus, ploidy could be used as a biomarker for treating glioma patients with Aurora kinases inhibitors.

Targeting the Chromosomal Passenger Complex Subunit INCENP Induces Polyploidization, Apoptosis, and Senescence in Neuroblastoma

Chromosomal passenger complex (CPC) has been demonstrated to be a potential target of cancer therapy by inhibiting Aurora B or survivin in different types of cancer including neuroblastoma. However, chemical inhibition of either Aurora B or survivin does not target CPC specifically due to off-target effects or CPC-independent activities of these two components. In a previous chromatin-focused siRNA screen, we found that neuroblastoma cells were particularly vulnerable to loss of INCENP, a gene encoding a key scaffolding component of the CPC. In this study, INCENP was highly expressed by neuroblastoma cells, and its expression decreased following retinoic acid-induced neuroblastoma differentiation. Elevated levels of INCENP were significantly associated with poor prognosis in primary tumors of neuroblastoma patients with high-risk disease. Genetic silencing of INCENP reduced the growth of both MYCN-wild-type and MYCN-amplified neuroblastoma cell lines in vitro and decreased the growth of neuroblastoma xenografts in vivo, with significant increases in murine survival. Mechanistically, INCENP depletion suppressed neuroblastoma cell growth by inducing polyploidization, apoptosis, and senescence. In most neuroblastoma cell lines tested in vitro, apoptosis was the primary cell fate after INCENP silencing due to induction of DNA damage response and activation of the p53-p21 axis. These results confirm that CPC is a therapeutic target in neuroblastoma, and targeting INCENP is a novel way to disrupt the activity of CPC and inhibit tumor progression in neuroblastoma. SIGNIFICANCE: Dysregulation of INCENP contributes to neuroblastoma tumorigenesis and targeting INCENP presents a novel strategy to disrupt the activity of chromosomal passenger complex and inhibit neuroblastoma progression.

AURKB as a target in non-small cell lung cancer with acquired resistance to anti-EGFR therapy

Non-small cell lung cancer (NSCLC) tumors harboring mutations in EGFR ultimately relapse to therapy with EGFR tyrosine kinase inhibitors (EGFR TKIs). Here, we show that resistant cells without the p.T790M or other acquired mutations are sensitive to the Aurora B (AURKB) inhibitors barasertib and S49076. Phospho-histone H3 (pH3), a major product of AURKB, is increased in most resistant cells and treatment with AURKB inhibitors reduces the levels of pH3, triggering G1/S arrest and polyploidy. Senescence is subsequently induced in cells with acquired mutations while, in their absence, polyploidy is followed by cell death. Finally, in NSCLC patients, pH3 levels are increased after progression on EGFR TKIs and high pH3 baseline correlates with shorter survival. Our results reveal that AURKB activation is associated with acquired resistance to EGFR TKIs, and that AURKB constitutes a potential target in NSCLC progressing to anti-EGFR therapy and not carrying resistance mutations.

Non-small cell lung cancer with EGFR mutations are known to develop resistance to EGFR tyrosine kinase inhibitors. Here, the authors show AURKB activation to be associated with resistance in EGFR mutant lung cancer cells, and that AURKB is a therapeutic target in resistant tumours that lack the p.T790M or other acquired mutations.

Insights into the optimal use of ponatinib in patients with chronic phase chronic myeloid leukaemia

There are five tyrosine kinase inhibitors (TKIs) that are currently approved (in the European Union and the United States) for the treatment of chronic myeloid leukaemia (CML) in the chronic phase (CP) and each of them has its own efficacy and toxicity profile. Oral ponatinib (Iclusig^®) is a third-generation TKI structurally designed to inhibit native BCR-ABL1 tyrosine kinase and several BCR-ABL1 mutants, including T315I. Ponatinib is now approved for patients with CML who are resistant or intolerant to prior TKI therapy (European Union) or for whom no other TKI therapy is indicated (United States). Despite achieving results in heavily treated patients, which led to its approval, the drug may induce cardiovascular events, requiring a careful baseline assessment of predisposing risk factors and specific management during treatment. Pharmacokinetic analysis has indicated the possibility of reducing the starting dose of ponatinib to 15 mg/day and preliminary data showed advantages in terms of safety while maintained its efficacy. This review summarizes the results achieved and drug-related side effects reported in all clinical trials and real-life experiences, testing ponatinib in patients with CP-CML. In addition, we focus on the appropriate use of ponatinib in clinical practice suggesting some useful recommendations on the proper management of this drug.

Non‑thermal plasma inhibits tumor growth and proliferation and enhances the sensitivity to radiation in vitro and in vivo

Cancer is a major disease currently endangering the entire world population. Morbidity and mortality have increased substantially during recent decades. Radiotherapy is a primary treatment for malignant tumors, however side-effects and tumor cell resistance to ionizing radiation reduce the efficacy of radiotherapy. In recent years, non-thermal plasma (NTP) technology been used to treat cancer. In this study, we investigated the toxic effects of NTP on normal cells and tumor cells. We explored the inhibitory effect of NTP on tumor cell proliferation and evaluated the radiation-sensitizing effects of NTP on tumor cells and its mechanisms. In short, we examined the effect of NTP-combined radiation on proliferation, the cell cycle, apoptosis and DNA damage in normal and cancer cells. We found that NTP inhibited proliferation and induced apoptosis in tumor cells. NTP was more lethal to tumor cells than to normal cells. We found promising synergies of NTP with radiotherapy on cancer cells owing to their combined cytotoxic effects by generating ROS, inducing cell cycle arrest and apoptosis. NTP may be a new candidate for the treatment of cancer.

Non-Cell Autonomous Effects of the Senescence-Associated Secretory Phenotype in Cancer Therapy

In addition to promoting various forms of cell death, most conventional anti-tumor therapies also promote senescence. There is now extensive evidence that therapy-induced senescence (TIS) might be transient, raising the concern that TIS could represent an undesirable outcome of therapy by providing a mechanism for tumor dormancy and eventual disease recurrence. The senescence-associated secretory phenotype (SASP) is a hallmark of TIS and may contribute to aberrant effects of cancer therapy. Here, we propose that the SASP may also serve as a major driver of escape from senescence and the re-emergence of proliferating tumor cells, wherein factors secreted from the senescent cells contribute to the restoration of tumor growth in a non-cell autonomous fashion. Accordingly, anti-SASP therapies might serve to mitigate the deleterious outcomes of TIS. In addition to providing an overview of the putative actions of the SASP, we discuss recent efforts to identify and eliminate senescent tumor cells.

Non ABL-directed inhibitors as alternative treatment strategies for chronic myeloid leukemia

The introduction of ABL Tyrosine Kinase Inhibitors (TKIs) has significantly improved the outcome of Chronic Myeloid Leukemia (CML) patients that, in large part, achieve satisfactory hematological, cytogenetic and molecular remissions. However, approximately 15-20% fail to obtain optimal responses according to the current European Leukemia Network recommendation because of drug intolerance or resistance.Moreover, a plethora of evidence suggests that Leukemic Stem Cells (LSCs) show BCR-ABL1-independent survival. Hence, they are unresponsive to TKIs, leading to disease relapse if pharmacological treatment is discontinued.All together, these biological events generate a subpopulation of CML patients in need of alternative therapeutic strategies to overcome TKI resistance or to eradicate LSCs in order to allow cure of the disease.In this review we update the role of "non ABL-directed inhibitors" targeting signaling pathways downstream of the BCR-ABL1 oncoprotein and describe immunological approaches activating specific T cell responses against CML cells.

Semi‑random mutagenesis profile of BCR‑ABL during imatinib resistance acquirement in K562 cells

Although imatinib is effective in chronic myeloid leukemia treatment, imatinib resistance due to the T315I mutation and/or other mutations is a challenge to be overcome. However, how DNA mutation occurs, particularly the T315I mutation, remains unclear. In the current study, the mutagenesis of BCR-ABL was analyzed via focusing on the process of drug resistance, rather than the final results. Clone sequencing of the BCR-ABL gene and other control genes was applied in two imatinib-resistant cell models. The results have indicated that imatinib actively and selectively causes sporadic mutations in the BCR-ABL gene, however not in the control genes. The majority of the mutations of BCR-ABL were not the clinically observed T315I mutation, suggesting that the T315I mutation may be due to clonal expansion of cells with survival advantages. Taken together, the results of the current study elucidated the mutagenesis process during drug resistance and thus aids in the management of chemotherapy.

The hOCT1 and ABCB1 polymorphisms do not influence the pharmacodynamics of nilotinib in chronic myeloid leukemia

First-line nilotinib in chronic myeloid leukemia is more effective than imatinib to achieve early and deep molecular responses, despite poor tolerability or failure observed in one-third of patients. The toxicity and efficacy of tyrosine kinase inhibitors might depend on the activity of transmembrane transporters. However, the impact of transporters genes polymorphisms in nilotinib setting is still debated. We investigated the possible correlation between single nucleotide polymorphisms of hOCT1 (rs683369 [c.480C>G]) and ABCB1 (rs1128503 [c.1236C>T], rs2032582 [c.2677G>T/A], rs1045642 [c.3435C>T]) and nilotinib efficacy and toxicity in a cohort of 78 patients affected by chronic myeloid leukemia in the context of current clinical practice. The early molecular response was achieved by 81% of patients while 64% of them attained deep molecular response (median time, 26 months). The 36-month event-free survival was 86%, whereas 58% of patients experienced toxicities. Interestingly, hOCT1 and ABCB1 polymorphisms alone or in combination did not influence event-free survival or the adverse events rate. Therefore, in contrast to data obtained in patients treated with imatinib, hOCT1 and ABCB1 polymorphisms do not impact on nilotinib efficacy or toxicity. This could be relevant in the choice of the first-line therapy: patients with polymorphisms that negatively condition imatinib efficacy might thus receive nilotinib as first-line therapy.