Drug resistance: still a daunting challenge to the successful treatment of AML

Continuous 72-h infusion of zosuquidar with chemotherapy in patients with newly diagnosed acute myeloid leukemia stratified for leukemic blast P-glycoprotein phenotype

PURPOSE

To evaluate the safety, tolerability, pharmacodynamics (PD), and potential efficacy of zosuquidar (Zos) in combination with daunorubicin and cytarabine in elderly patients with newly diagnosed acute myeloid leukemia (AML).

METHODS

Patients with AML (N = 106) were treated with Zos as a 72-h continuous intravenous (CIV) infusion along with chemotherapy. Leukemic blasts from the patients were assessed for P-glycoprotein (P-gp) function using ex vivo bioassays for screening and PD analyses. Patient outcomes were categorized according to primary (N = 56) and secondary (N = 50) AML cohorts (pAML and sAML, respectively) and stratified into P-gp-high and P-gp-low subgroups.

RESULTS

Patients with P-gp-high blasts exhibited comparable overall remission rates (ORR) to those with P-gp-low blasts in both the pAML and sAML cohorts. The P-gp-high and P-gp-low subgroups in the pAML cohort exhibited similar overall survival (OS). Patients with sAML and P-gp-high blasts exhibited significantly better OS than those in the P-gp-low subgroup. PD analyses revealed that Zos infusion provided 82 h of uninterrupted effective ≥ 90% inhibition of P-gp functional activity in leukemic blasts.

CONCLUSIONS

These observations provide evidence of Zos efficacy with the 72-h CIV infusion approach. The similarity of ORR in the P-gp-high and P-gp-low subgroups is consistent with Zos-mediated neutralization of P-gp as verified by PD analyses. The bioassay identified sAML patients most likely to respond favorably to Zos co-therapy indicating feasibility as a Zos companion diagnostic. A follow-up placebo-controlled trial is needed to verify these promising results.

CLINICALTRIALS

GOV IDENTIFIER

NCT00129168; First posted on August 11, 2005.

Reactive oxygen species and its role in pathogenesis and resistance to therapy in acute myeloid leukemia

Relapse following a short clinical response to therapy is the major challenge for the management of acute myeloid leukemia (AML) patients. Leukemic stem cells (LSC), as the source of relapse, have been investigated for their metabolic preferences and their alterations at the time of relapse. As LSC rely on oxidative phosphorylation (OXPHOS) for energy requirement, reactive oxygen species (ROS), as by-products of OXPHOS, have been investigated for their role in the effectiveness of the standard AML therapy. Increased levels of non-mitochondrial ROS, generated by nicotinamide adenine dinucleotide phosphate oxidase, in a subgroup of AML patients add to the complexity of studying ROS. Although there are various studies presenting the contribution of ROS to AML pathogenesis, resistance, and its inhibition or activation as a target, a model that can clearly explain its role in AML has not been conceptualized. This is due to the heterogeneity of AML, the dynamics of ROS production, which is influenced by factors such as the type of treatment, cell differentiation state, mitochondrial activity, and also the heterogeneous generation of non-mitochondrial ROS and limited available data on their interaction with the microenvironment. This review summarizes these challenges and the recent progress in this field.

Structural View of Cryo-Electron Microscopy-Determined ATP-Binding Cassette Transporters in Human Multidrug Resistance

ATP-binding cassette (ABC) transporters, acting as cellular "pumps," facilitate solute translocation through membranes via ATP hydrolysis. Their overexpression is closely tied to multidrug resistance (MDR), a major obstacle in chemotherapy and neurological disorder treatment, hampering drug accumulation and delivery. Extensive research has delved into the intricate interplay between ABC transporter structure, function, and potential inhibition for MDR reversal. Cryo-electron microscopy has been instrumental in unveiling structural details of various MDR-causing ABC transporters, encompassing ABCB1, ABCC1, and ABCG2, as well as the recently revealed ABCC3 and ABCC4 structures. The newly obtained structural insight has deepened our understanding of substrate and drug binding, translocation mechanisms, and inhibitor interactions. Given the growing body of structural information available for human MDR transporters and their associated mechanisms, we believe it is timely to compile a comprehensive review of these transporters and compare their functional mechanisms in the context of multidrug resistance. Therefore, this review primarily focuses on the structural aspects of clinically significant human ABC transporters linked to MDR, with the aim of providing valuable insights to enhance the effectiveness of MDR reversal strategies in clinical therapies.

Structure-ATPase Activity Relationship of Rhodamine Derivatives as Potent Inhibitors of P-Glycoprotein CmABCB1

Understanding the transport and inhibition mechanisms of substrates by P-glycoprotein (P-gp) is one of the important approaches in addressing multidrug resistance (MDR). In this study, we evaluated a variety of rhodamine derivatives as potential P-gp inhibitors targeting CmABCB1, a P-gp homologue, with a focus on their ATPase activity. Notably, a Q-rhodamine derivative with an o,o'-dimethoxybenzyl ester moiety (RhQ-DMB) demonstrated superior affinity and inhibitory activity, which was further confirmed by a drug susceptibility assay in yeast strains expressing CmABCB1. Results from a tryptophan fluorescence quenching experiment using a CmABCB1 mutant suggested that RhQ-DMB effectively enters and binds to the inner chamber of CmABCB1. These findings underscore the promising potential of RhQ-DMB as a tool for future studies aimed at elucidating the substrate-bound state of CmABCB1.

IL-8 from CD248-expressing cancer-associated fibroblasts generates cisplatin resistance in non-small cell lung cancer

Chemotherapy-resistant non-small cell lung cancer (NSCLC) presents a substantial barrier to effective care. It is still unclear how cancer-associated fibroblasts (CAFs) contribute to NSCLC resistance to chemotherapy. Here, we found that CD248+ CAFs released IL-8 in NSCLC, which, in turn, enhanced the cisplatin (CDDP) IC50 in A549 and NCI-H460 while decreasing the apoptotic percentage of A549 and NCI-H460 in vitro. The CD248+ CAFs-based IL-8 secretion induced NSCLC chemoresistance by stimulating nuclear factor kappa B (NF-κB) and elevating ATP-binding cassette transporter B1 (ABCB1). We also revealed that the CD248+ CAFs-based IL-8 release enhanced cisplatin chemoresistance in NSCLC mouse models in vivo. Relative to wild-type control mice, the CD248 conditional knockout mice exhibited significant reduction of IL-8 secretion, which, in turn, enhanced the therapeutic efficacy of cisplatin in vivo. In summary, our study identified CD248 activates the NF-κB axis, which, consecutively induces the CAFs-based secretion of IL-8, which promotes NSCLC chemoresistance. This report highlights a potential new approach to enhancing the chemotherapeutic potential of NSCLC-treating cisplatin.

Linking ABC transporters to the hallmarks of cancer

Human ATP-binding cassette (ABC) transporters are ubiquitously expressed and transport a broad range of endogenous and xenobiotic substrates across extra- and intracellular membranes. Mutations in ABC genes cause 21 monogenic diseases, and polymorphisms in these genes are associated with susceptibility to complex diseases. ABC transporters also play a major role in drug bioavailability, and they mediate multidrug resistance in cancer. At least 13 ABC transporters were shown to be involved in drug resistance in vitro. In the past decade, efforts have been made to elucidate their roles in tumor biology. Herein, we explore their involvement in tumorigenesis, focusing on the hallmarks of cells as they make their way from normalcy to neoplastic growth states.

Overcoming Chemotherapy Resistance in Metastatic Cancer: A Comprehensive Review

The management of metastatic cancer is complicated by chemotherapy resistance. This manuscript provides a comprehensive academic review of strategies to overcome chemotherapy resistance in metastatic cancer. The manuscript presents background information on chemotherapy resistance in metastatic cancer cells, highlighting its clinical significance and the current challenges associated with using chemotherapy to treat metastatic cancer. The manuscript delves into the molecular mechanisms underlying chemotherapy resistance in subsequent sections. It discusses the genetic alterations, mutations, and epigenetic modifications that contribute to the development of resistance. Additionally, the role of altered drug metabolism and efflux mechanisms, as well as the activation of survival pathways and evasion of cell death, are explored in detail. The strategies to overcome chemotherapy resistance are thoroughly examined, covering various approaches that have shown promise. These include combination therapy approaches, targeted therapies, immunotherapeutic strategies, and the repurposing of existing drugs. Each strategy is discussed in terms of its rationale and potential effectiveness. Strategies for early detection and monitoring of chemotherapy drug resistance, rational drug design vis-a-vis personalized medicine approaches, the role of predictive biomarkers in guiding treatment decisions, and the importance of lifestyle modifications and supportive therapies in improving treatment outcomes are discussed. Lastly, the manuscript outlines the clinical implications of the discussed strategies. It provides insights into ongoing clinical trials and emerging therapies that address chemotherapy resistance in metastatic cancer cells. The manuscript also explores the challenges and opportunities in translating laboratory findings into clinical practice and identifies potential future directions and novel therapeutic avenues. This comprehensive review provides a detailed analysis of strategies to overcome chemotherapy resistance in metastatic cancer. It emphasizes the importance of understanding the molecular mechanisms underlying resistance and presents a range of approaches for addressing this critical issue in treating metastatic cancer.

Serum circRNA_100199 is a Prognostic Biomarker in Acute Myeloid Leukemia

Background

An aberrant level of serum microRNA expression has been demonstrated to be a prognostic marker for acute myeloid leukemia (AML). The therapeutic relevance of serum circRNA 100199 remained unknown, however. This research aimed to investigate the probable prognostic significance of serum circRNA_100199 for AML.

Methods

This study included a total of 200 participants consisting of 114 AML-diagnosed patients and 86 healthy people. Blood samples were taken, and the level of circRNA_100199 in the serum was measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR) to explore its potential clinical significance.

Results

Our study demonstrated that circRNA_100199 expression in the serum was substantially higher in AML subjects than in healthy persons. This increase in serum circRNA_100199 levels was particularly noticeable in M4/M5 subtype AML patients, and those with poor cytogenetic risk or higher white blood cell counts. Using receiver operating characteristic (ROC) analysis, AML cases were effectively differentiated from healthy persons based on the level of serum circRNA_100199. Furthermore, it was found that high serum circRNA_100199 expression was strongly linked with shorter survival times and more severe clinical features. Our study also confirmed that high serum circRNA_100199 expression was an independent predictor of relapse-free survival (RFS) and overall survival (OS) in AML patients. Interestingly, the serum expression level of circRNA_100199 was significantly reduced following treatment, and its levels were substantially lower in AML patients who achieved complete remission (CR) than those who did not.

Conclusion

Overall, these findings suggest that serum circRNA_100199 has the potential to be a favorable prognostic biomarker for AML.

The influence of BCL2, BAX, and ABCB1 gene expression on prognosis of adult de novo acute myeloid leukemia with normal karyotype patients

BACKGROUND

Deregulation of the apoptotic process underlies the pathogenesis of many cancers, including leukemia, but is also very important for the success of chemotherapy treatment. Therefore, the gene expression profile of main apoptotic factors, such as anti-apoptotic BCL2 (B-cell lymphoma protein 2) and pro-apoptotic BAX (BCL2-associated X), as well as genes involved in the multi-drug resistance (ABCB1), could have significant impact on the prognosis and could be used as targets for specific therapy.

PATIENTS AND METHODS

We analyzed the expression of BCL2, BAX, and ABCB1 in bone-marrow samples collected at diagnosis from 51 adult patients with acute myeloid leukemia with normal karyotype (AML-NK) using real-time polymerase chain reaction method, and examined their prognostic potential.

RESULTS

Increased expression of BCL2 (BCL2 ⁺) was associated with the presence of chemoresistance (p = 0.024), while patients with low BAX expression were more prone to relapse (p = 0.047). Analysis of the combined effect of BCL2 and BAX expression showed that 87% of patients with BAX/BCL2 ^low status were resistant to therapy (p = 0.044). High expression of ABCB1 was associated with BCL2 ⁺ status (p < 0.001), and with absence FLT3-ITD mutations (p = 0.019).

CONCLUSIONS

The present analysis of BCL2, BAX, and ABCB1 gene expression profiles is the first study focusing solely on AML-NK patients. Preliminary results showed that patients with high BCL2 expression are likely to experience resistance to chemotherapy, and may benefit from specific anti-BCL2 treatment. Further investigations conducted on a larger number of patients could elucidate actual prognostic significance of these genes in AML-NK patients.

The ATP-binding cassette proteins ABCB1 and ABCC1 as modulators of glucocorticoid action

Responses to hormones that act through nuclear receptors are controlled by modulating hormone concentrations not only in the circulation but also within target tissues. The role of enzymes that amplify or reduce local hormone concentrations is well established for glucocorticoid and other lipophilic hormones; moreover, transmembrane transporters have proven critical in determining tissue responses to thyroid hormones. However, there has been less consideration of the role of transmembrane transport for steroid hormones. ATP-binding cassette (ABC) proteins were first shown to influence the accumulation of glucocorticoids in cells almost three decades ago, but observations over the past 10 years suggest that differential transport propensities of both exogenous and endogenous glucocorticoids by ABCB1 and ABCC1 transporters provide a mechanism whereby different tissues are preferentially sensitive to different steroids. This Review summarizes this evidence and the new insights provided for the physiology and pharmacology of glucocorticoid action, including new approaches to glucocorticoid replacement.

The anti-estrogen receptor drug, tamoxifen, is selectively Lethal to P-glycoprotein-expressing Multidrug resistant tumor cells

BACKGROUND

P-glycoprotein (P-gp), a member of the ATP Binding Cassette B1 subfamily (ABCB1), confers resistance to clinically relevant anticancer drugs and targeted chemotherapeutics. However, paradoxically P-glycoprotein overexpressing drug resistant cells are "collaterally sensitive" to non-toxic drugs that stimulate its ATPase activity.

METHODS

Cell viability assays were used to determine the effect of low concentrations of tamoxifen on the proliferation of multidrug resistant cells (CHO^RC5 and MDA-Doxo⁴⁰⁰), expressing P-gp, their parental cell lines (AuxB1 and MDA-MB-231) or P-gp-CRISPR knockout clones of AuxB1 and CHO^RC5 cells. Western blot analysis was used to estimate P-gp expression in different cell lines. Apoptosis of tamoxifen-induced cell death was estimated by flow cytometry using Annexin-V-FITC stained cells. Oxidative stress of tamoxifen treated cells was determined by measuring levels of reactive oxygen species and reduced thiols using cell-permeant 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) and 5,5-dithio-bis-(2-nitrobenzoic acid) DTNB, respectively.

RESULTS

In this report, we show that P-gp-expressing drug resistant cells (CHO^RC5 and MDA-Doxo⁴⁰⁰) are collaterally sensitive to the anti-estrogen tamoxifen or its metabolite (4-hydroxy-tamoxifen). Moreover, P-gp-knockout clones of CHO^RC5 cells display complete reversal of collateral sensitivity to tamoxifen. Drug resistant cells exposed to low concentrations of tamoxifen show significant rise in reactive oxygen species, drop of reduced cellular thiols and increased apoptosis. Consistent with the latter, CHO^RC5 cells expressing high levels of human Bcl-2 (CHO^RC5-Bcl-2) show significant resistance to tamoxifen. In addition, the presence of the antioxidant N-acetylcysteine or P-gp ATPase inhibitor, PSC-833, reverse the collateral sensitivity of resistant cells to tamoxifen. By contrast, the presence of rotenone (specific inhibitor of mitochondria complex I) synergizes with tamoxifen.

CONCLUSION

This study demonstrates the use of tamoxifen as collateral sensitivity drug that can preferentially target multidrug resistant cells expressing P-gp at clinically achievable concentrations. Given the widespread use of tamoxifen in the treatment of estrogen receptor-positive breast cancers, this property of tamoxifen may have clinical applications in treatment of P-gp-positive drug resistant breast tumors.

Pharmacological Activities and Pharmacokinetics of Glycycoumarin

Glycycoumarin is a representative coumarin compound with significant pharmacological activities isolated from Glycyrrhiza uralensis Fisch., Fabaceae. Studies have shown that glycycoumarin has many biological activities, such as anti-tumor, liver protection, antispasmodic, antibacterial, and antivirus. However, the poor solubility of glycycoumarin in water and the accompanying reactions of the phase I (hydroxylation) and II (glucuronidation) metabolism limit its druggability, which manifests as low absorption in the body after oral administration and low free drug concentration, ultimately leading to low bioavailability. Therefore, a comprehensive review of the pharmacological effects and pharmacokinetics of glycycoumarin is presented to provide a reference for further research and application as a therapeutic agent.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43450-022-00342-x.

PPARγ activation by pioglitazone enhances the anti-proliferative effects of doxorubicin on pro-monocytic THP-1 leukemia cells via inducing apoptosis and G2/M cell cycle arrest

PURPOSE

Doxorubicin (DOX) is a common chemotherapeutic agent, with toxic side effects, and chemoresistance. Combination chemotherapy is a successful approach to overcome these limitations. Here, we investigated the effects of pioglitazone (PGZ), a PPARγ agonist, and/or DOX on the viability, cell cycle, apoptosis on THP-1 cells and normal human monocytes (NHMs).

METHODS

MTT assay was used to evaluate the cytotoxicity of DOX and/or PGZ. Cell cycle progression and apoptosis induction were examined by PI or Annexin V-PI double staining, and analyzed by flow cytometry. Quantitative RT-PCR was used to evaluate the changes in the mRNA expression of cell cycle progression or apoptosis-associated genes including P27, P21, CDK2, P53, BCL2 and FasR.

RESULTS

DOX, PGZ and DOX + PGZ exerted their cytotoxic effects in a dose- and time-dependent manner with low toxicity on NHMs. The cell growth inhibitory effects of DOX were in association with G2/M arrest, while PGZ executed S phase arrest. PGZ treatment enhanced G2/M among DOX-treated combinations with moderate elevation in the S phase. DOX, PGZ and combined treatments induced apoptosis (mostly late phase) in a dose-dependent manner. All treatments resulted in the significant overexpression of p21, p27, p53 and FasR genes and downregulation of CDK2. DOX + PGZ combined treatments exhibited the most significant changes in mRNA expression.

CONCLUSION

We demonstrated that the antiproliferative, cell cycle regulation and apoptosis-inducing capacity of DOX was enhanced by PGZ in THP-1 leukemia cells in a dose-dependent manner. Therefore, the combination of DOX + PGZ could be used as a novel combination to target AML.

Harnessing the power of sphingolipids: Prospects for acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive, heterogenous malignancy characterized by clonal expansion of bone marrow-derived myeloid progenitor cells. While our current understanding of the molecular and genomic landscape of AML has evolved dramatically and opened avenues for molecularly targeted therapeutics to improve upon standard intensive induction chemotherapy, curative treatments are elusive, particularly in older patients. Responses to current AML treatments are transient and incomplete, necessitating the development of novel treatment strategies to improve outcomes. To this end, harnessing the power of bioactive sphingolipids to treat cancer shows great promise. Sphingolipids are involved in many hallmarks of cancer of paramount importance in AML. Leukemic blast survival is influenced by cellular levels of ceramide, a bona fide pro-death molecule, and its conversion to signaling molecules such as sphingosine-1-phosphate and glycosphingolipids. Preclinical studies demonstrate the efficacy of therapeutics that target dysregulated sphingolipid metabolism as well as their combinatorial synergy with clinically-relevant therapeutics. Thus, increased understanding of sphingolipid dysregulation may be exploited to improve AML patient care and outcomes. This review summarizes the current knowledge of dysregulated sphingolipid metabolism in AML, evaluates how pro-survival sphingolipids promote AML pathogenesis, and discusses the therapeutic potential of targeting these dysregulated sphingolipid pathways.

Targeting histone methylation to reprogram the transcriptional state that drives survival of drug-tolerant myeloid leukemia persisters

Although chemotherapy induces complete remission in the majority of acute myeloid leukemia (AML) patients, many face a relapse. This relapse is caused by survival of chemotherapy-resistant leukemia (stem) cells (measurable residual disease; MRD). Here, we demonstrate that the anthracycline doxorubicin epigenetically reprograms leukemia cells by inducing histone 3 lysine 27 (H3K27) and H3K4 tri-methylation. Within a doxorubicin-sensitive leukemia cell population, we identified a subpopulation of reversible anthracycline-tolerant cells (ATCs) with leukemic stem cell (LSC) features lacking doxorubicin-induced H3K27me3 or H3K4me3 upregulation. These ATCs have a distinct transcriptional landscape than the leukemia bulk and could be eradicated by KDM6 inhibition. In primary AML, reprogramming the transcriptional state by targeting KDM6 reduced MRD load and survival of LSCs residing within MRD, and enhanced chemotherapy response in vivo. Our results reveal plasticity of anthracycline resistance in AML cells and highlight the potential of transcriptional reprogramming by epigenetic-based therapeutics to target chemotherapy-resistant AML cells.

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Reversible anthracycline-tolerant leukemia cells (ATCs) have low H3K27me3 or H3K4me3

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ATCs exhibit stem cell features similar to leukemic stem cells

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Reprogramming the transcriptional state by inhibition of KDM6 depletes ATCs

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Inhibiting KDM6 adds to doxorubicin treatment and eradicates AML MRD (stem) cells

Molecular Profiling of Kenyan Acute Myeloid Leukemia Patients

Acute myeloid leukemia (AML) is an infrequent disease, and it is associated with high morbidity and mortality. It harbors a unique configuration of cytogenetic abnormalities and molecular mutations that can be detected using microscopic and molecular methods respectively. These genetic tests are core elements of diagnosis and prognostication in high-income countries. They are routinely incorporated in clinical decision making, allowing for the individualization of therapy. However, these tests are largely inaccessible to most patients in Kenya and therefore no data has been reported on this group of patients. The main purpose of this study is to describe the cytogenetic and molecular abnormalities of acute myeloid leukemia patients seen at the hemato-oncology unit of Kenyatta National Hospital. A cross-sectional descriptive study was carried out over a 3-month period on ten patients with a diagnosis of AML. Social demographics and clinical data were collected through a study proforma. A peripheral blood sample was collected for conventional metaphase G-banding technique and next generation sequencing. Particularly, targeted DNA sequencing (Illumina myeloid panel) and whole exome sequencing (WES) were performed. Cytogenetic analysis failed in 10/10 cases. Targeted sequencing was successfully obtained in 8 cases, whereas WES in 7. Cytogenetic studies yielded no results. There were 20 mutations detected across 10 commonly mutated genes. All patients had at least one clinically relevant mutation. Based on ELN criteria, NGS identified three patients with high-risk mutations, affecting TP53 (n = 2) and RUNX1 (n = 1). One patient was classified as favorable (PML-RARA) while 4 were standard risk. However, WT1 mutations associated with unfavorable prognosis were recorded in additional 2 cases. WES showed concordant results with targeted sequencing while unveiling more mutations that warrant further attention. In conclusion, we provide the first molecular profiling study of AML patients in Kenya including application of advanced next generation sequencing technologies, highlighting current limitations of AML diagnostics and treatment while confirming the relevance of NGS in AML characterization.

ABCB1 as a potential beneficial target of midostaurin in acute myeloid leukemia

Low curability of patients diagnosed with acute myeloid leukemia (AML) must be seen as a call for better understanding the disease's mechanisms and improving the treatment strategy. Therapeutic outcome of the crucial anthracycline-based induction therapy often can be compromised by a resistant phenotype associated with overexpression of ABCB1 transporters. Here, we evaluated clinical relevance of ABCB1 in a context of the FMS-like tyrosine kinase 3 (FLT3) inhibitor midostaurin in a set of 28 primary AML samples. ABCB1 gene expression was absolutely quantified, confirming its association with CD34 positivity, adverse cytogenetic risk, and unachieved complete remission (CR). Midostaurin, identified as an ABCB1 inhibitor, increased anthracycline accumulation in peripheral blood mononuclear cells (PBMC) of CD34⁺ AML patients and those not achieving CR. This effect was independent of FLT3 mutation, indicating even FLT3^- AML patients might benefit from midostaurin therapy. In line with these data, midostaurin potentiated proapoptotic processes in ABCB1-overexpressing leukemic cells when combined with anthracyclines. Furthermore, we report a direct linkage of miR-9 to ABCB1 efflux activity in the PBMC and propose miR-9 as a useful prognostic marker in AML. Overall, we highlight the therapeutic value of midostaurin as more than just a FLT3 inhibitor, suggesting its maximal therapeutic outcomes might be very sensitive to proper timing and well-optimized dosage schemes based upon patient's characteristics, such as CD34 positivity and ABCB1 activity. Moreover, we suggest miR-9 as a predictive ABCB1-related biomarker that could be immensely helpful in identifying ABCB1-resistant AML phenotype to enable optimized therapeutic regimen and improved treatment outcome.

Natural killer cells and acute myeloid leukemia: promises and challenges

Acute myeloid leukemia (AML) is considered as one of the most malignant conditions of the bone marrow. Over the past few decades, despite substantial progresses in the management of AML, relapse remission remains a major problem. Natural killer cells (NK cells) are known as a unique component of the innate immune system. Due to swift tumor detection, distinct cytotoxic action, and extensive immune interaction, NK cells have been used in various cancer settings for decades. It has been a growing knowledge of therapeutic magnitudes ranging from adoptive NK cell transfer to chimeric antigen receptor NK cells, aiming to achieve better therapeutic responses in patients with AML. In this article, the potentials of NK cells for treatment of AML are highlighted, and challenges for such therapeutic methods are discussed. In addition, the clinical application of NK cells, mainly in patients with AML, is pictured according to the existing evidence.

Tumor microenvironment manipulates chemoresistance in ovarian cancer (Review)

Ovarian cancer (OC) is the leading cause of mortality among the various types of gynecological cancer, and >75% of the cases are diagnosed at a late stage. Although platinum‑based chemotherapy is able to help the majority of patients to achieve remission, the disease frequently recurs and acquires chemoresistance, resulting in high mortality rates. The complexity of OC therapy is not solely governed by the intrinsic characteristics of the OC cells (OCCs) themselves, but is also largely dependent on the dynamic communication between OCCs and various components of their surrounding microenvironment. The present review attempts to describe the mutual interplay between OCCs and their surrounding microenvironment. Tumor‑associated macrophages (TAMs) and cancer‑associated fibroblasts (CAFs) are the most abundant stromal cell types in OC. Soluble factors derived from CAFs steadily nourish both the OCCs and TAMs, facilitating their proliferation and immune evasion. ATP binding cassette transporters facilitate the extrusion of cytotoxic molecules, eventually promoting cell survival and multidrug resistance. Extracellular vesicles fulfill their role as genetic exchange vectors, transferring cargo from the donor cells to the recipient cells and propagating oncogenic signaling. A greater understanding of the vital roles of the tumor microenvironment will allow researchers to be open to the prospect of developing therapeutic approaches for combating OC chemoresistance.

Phytol and Heptacosane Are Possible Tools to Overcome Multidrug Resistance in an In Vitro Model of Acute Myeloid Leukemia

Drug resistance is the ability of cancer cells to gain resistance to both conventional and novel chemotherapy agents, and remains a major problem in cancer therapy. Resistance mechanisms are multifactorial and involve more strictly pharmacological factors, such as P-glycoprotein (P-gp) and biological factors such as inhibitor of apoptosis proteins (IAPs) and the nuclear factor-kappa B (NF-κB) pathway. Possible therapeutic strategies for the treatment of acute myeloid leukemia (AML) have increased in recent years; however, drug resistance remains a problem for most pa-tients. Phytol and heptacosane are the major compounds of Euphorbia intisy essential oil (EO) which were demonstrated to inhibit P-gp in a multidrug resistant in vitro model of AML. This study investigated the mechanism by which phytol and heptacosane improve P-gp-mediated drug transport. Phytol suppresses the P-gp expression via NF-κB inhibition and does not seem to act on the efflux system. Heptacosane acts as a substrate and potent P-gp inhibitor, demonstrating the ability to retain the substrate doxorubicin inside the cell and enhancing its cytotoxic effects. Our results suggest that these compounds act as non-toxic modulators of P-gp through different mechanisms and are able to revert P-gp-mediated drug resistance in tumor cells.

Decreased expression of autophagy‐related genes in the complete remission phase of acute myeloid leukemia

Background

Autophagy is a conserved recycling process in cells. However, the effects of autophagy on the remission and treatment response of acute myeloid leukemia (AML) patients have not been clarified.

Methods

The expression of MAP1LC3B, ATG5, ATG10, RB1CC1, and AMBRA1 genes was assessed in 32 newly diagnosed AML patients, 18 complete remission (CR) patients, and seven relapsed patients, as well as 15 controls, by real‐time polymerase chain reaction (PCR).

Results

The expression of all five genes was significantly higher in the newly diagnosed AML patients as compared to the controls (p < 0.0001). The MAP1LC3B, ATG5, ATG10, RB1CC1, and AMBRA1 gene expression significantly reduced in CR patients compared to newly diagnosed AML patients (p = 0.006, 0.003, 0.0002, 0.006, and 0.004, respectively). The AMBRA1 gene expression was significantly higher in the relapsed cases as compared to both newly diagnosed (p = 0.01) and CR patients (p = 0.03). Moreover, a significant positive correlation was observed between the expression of MAP1LC3B (r = 0.739, p = 0.000001), ATG5 (r = 0.682, p = 0.00001), and ATG10 (r = 0.586, p = 0.0004) genes and white blood cell (WBC) count in patients at diagnosis.

Conclusion

The expression of MAP1LC3B, ATG5, ATG10, RB1CC1, and AMBRA1 genes can be examined to follow‐up the remission of AML and the patient's response to treatment.

Targeted disruption of mitochondria potently reverses multidrug resistance in cancer therapy

BACKGROUND AND PURPOSE

Multidrug resistance (MDR) is the main obstacle to cancer therapy. Ample evidence shows that ATP-binding cassette (ABC) transporters and high-energy state substantially relate to cancer drug resistance. Our previous work reported an engineered therapeutic protein named PAK, which selectively inhibited tumor progression by targeting mitochondria.

EXPERIMENTAL APPROACH

Here, we studied the effects of PAK on reversing drug resistance in MDR phenotypic cells and xenograft mice models. The effects of PAK on the process of mitochondrial energy production, ABC transporters expression, and the drugs enrichment in cancer cells were further investigated. RNA-seq and co-immunoprecipitation were employed to analyze the mechanism of PAK on the redistribution of ABC transporters.

KEY RESULTS

PAK promoted the enrichment of drugs in MDR cancer cells, thus enhancing the sensitivity of cancer cells to chemotherapy. Furthermore, PAK was colocalized in the mitochondria and initiated mitochondrial injury by selectively inhibiting the mitochondrial complex V. Besides, ABCB1 and ABCC1 were found to be redistributed from the plasma membrane to the cytoplasm through the disruption of lipid rafts, which was attributed to the low energy state and the decrease of cholesterol levels.

CONCLUSIONS AND IMPLICATIONS

Our results revealed a previously unrecognized drug resistance reversal pattern and suggested mitochondria as a clinically relevant target for the treatment of MDR malignant tumors.

Rutaecarpine Inhibits U87 Glioblastoma Cell Migration by Activating the Aryl Hydrocarbon Receptor Signaling Pathway

Glioblastoma is the most frequent and aggressive primary astrocytoma in adults. The high migration ability of the tumor cells is an important reason for the high recurrence rate and poor prognosis of glioblastoma. Recently, emerging evidence has shown that the migration ability of glioblastoma cells was inhibited upon the activation of aryl hydrocarbon receptor (AhR), suggesting potential anti-tumor effects of AhR agonists. Rutaecarpine is a natural compound with potential tumor therapeutic effects which can possibly bind to AhR. However, its effect on the migration of glioblastoma is unclear. Therefore, we aim to explore the effects of rutaecarpine on the migration of human glioblastoma cells U87 and the involvement of the AhR signaling pathway. The results showed that: (i) compared with other structural related alkaloids, like evodiamine and dehydroevodiamine, rutaecarpine was a more potent AhR activator, and has a stronger inhibitory effect on the glioblastoma cell migration; (ii) rutaecarpine decreased the migration ability of U87 cells in an AhR-dependent manner; (iii) AhR mediated the expression of a tumor suppressor interleukin 24 (IL24) induced by rutaecarpine, and AhR-IL24 axis was involved in the anti-migratory effects of rutaecarpine on the glioblastoma. Besides IL24, other candidates AhR downstream genes both associated with cancer and migration were proposed to participate in the migration regulation of rutaecarpine by RNA-Seq and bioinformatic analysis. These data indicate that rutaecarpine is a naturally-derived AhR agonist that could inhibit the migration of U87 human glioblastoma cells mostly via the AhR-IL24 axis.

Alterations in sphingolipid composition and mitochondrial bioenergetics represent synergistic therapeutic vulnerabilities linked to multidrug resistance in leukemia

Modifications in sphingolipid (SL) metabolism and mitochondrial bioenergetics are key factors implicated in cancer cell response to chemotherapy, including chemotherapy resistance. In the present work, we utilized acute myeloid leukemia (AML) cell lines, selected to be refractory to various chemotherapeutics, to explore the interplay between SL metabolism and mitochondrial biology supportive of multidrug resistance (MDR). In agreement with previous findings in cytarabine or daunorubicin resistant AML cells, relative to chemosensitive wildtype controls, HL-60 cells refractory to vincristine (HL60/VCR) presented with alterations in SL enzyme expression and lipidome composition. Such changes were typified by upregulated expression of various ceramide detoxifying enzymes, as well as corresponding shifts in ceramide, glucosylceramide, and sphingomyelin (SM) molecular species. With respect to mitochondria, despite consistent increases in both basal respiration and maximal respiratory capacity, direct interrogation of the oxidative phosphorylation (OXPHOS) system revealed intrinsic deficiencies in HL60/VCR, as well as across multiple MDR model systems. Based on the apparent requirement for augmented SL and mitochondrial flux to support the MDR phenotype, we explored a combinatorial therapeutic paradigm designed to target each pathway. Remarkably, despite minimal cytotoxicity in peripheral blood mononuclear cells (PBMC), co-targeting SL metabolism, and respiratory complex I (CI) induced synergistic cytotoxicity consistently across multiple MDR leukemia models. Together, these data underscore the intimate connection between cellular sphingolipids and mitochondrial metabolism and suggest that pharmacological intervention across both pathways may represent a novel treatment strategy against MDR.

The Molecular Basis and Therapeutic Aspects of Cisplatin Resistance in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a kind of malignant tumors with low survival rate and prone to have early metastasis and recurrence. Cisplatin is an alkylating agent which induces DNA damage through the formation of cisplatin-DNA adducts, leading to cell cycle arrest and apoptosis. In the management of advanced OSCC, cisplatin-based chemotherapy or chemoradiotherapy has been considered as the first-line treatment. Unfortunately, only a portion of OSCC patients can benefit from cisplatin treatment, both inherent resistance and acquired resistance greatly limit the efficacy of cisplatin and even cause treatment failure. Herein, this review outline the underlying mechanisms of cisplatin resistance in OSCC from the aspects of DNA damage and repair, epigenetic regulation, transport processes, programmed cell death and tumor microenvironment. In addition, this review summarizes the strategies applicable to overcome cisplatin resistance, which can provide new ideas to improve the clinical therapeutic outcome of OSCC.

Regulatory noncoding RNAs: potential biomarkers and therapeutic targets in acute myeloid leukemia

The noncoding RNAs (ncRNA) comprise a substantial segment of the human transcriptome and have emerged as key elements of cellular homeostasis and disease pathogenesis. Dysregulation of these ncRNAs by alterations in the primary RNA motifs and/or aberrant expression levels is relevant in various diseases, especially cancer. The recent research advances indicate that ncRNAs regulate vital oncogenic processes, including hematopoietic cell differentiation, proliferation, apoptosis, migration, and angiogenesis. The ever-expanding role of ncRNAs in cancer progression and metastasis has sparked interest as potential diagnostic and prognostic biomarkers in acute myeloid leukemia. Moreover, advances in antisense oligonucleotide technologies and pharmacologic discoveries of small molecule inhibitors in targeting RNA structures and RNA-protein complexes have opened newer avenues that may help develop the next generation anti-cancer therapeutics. In this review, we have discussed the role of ncRNA in acute myeloid leukemia and their utility as potential biomarkers and therapeutic targets.

Kinase Inhibition in Relapsed/Refractory Leukemia and Lymphoma Settings: Recent Prospects into Clinical Investigations

Cancer is still a major barrier to life expectancy increase worldwide, and hematologic neoplasms represent a relevant percentage of cancer incidence rates. Tumor dependence of continuous proliferative signals mediated through protein kinases overexpression instigated increased strategies of kinase inhibition in the oncologic practice over the last couple decades, and in this review, we focused our discussion on relevant clinical trials of the past five years that investigated kinase inhibitor (KI) usage in patients afflicted with relapsed/refractory (R/R) hematologic malignancies as well as in the pharmacological characteristics of available KIs and the dissertation about traditional chemotherapy treatment approaches and its hindrances. A trend towards investigations on KI usage for the treatment of chronic lymphoid leukemia and acute myeloid leukemia in R/R settings was observed, and it likely reflects the existence of already established treatment protocols for chronic myeloid leukemia and acute lymphoid leukemia patient cohorts. Overall, regimens of KI treatment are clinically manageable, and results are especially effective when allied with tumor genetic profiles, giving rise to encouraging future prospects of an era where chemotherapy-free treatment regimens are a reality for many oncologic patients.

Rutaecarpine Increases Anticancer Drug Sensitivity in Drug-Resistant Cells through MARCH8-Dependent ABCB1 Degradation

The overexpression of adenosine triphosphate (ATP)-binding cassette (ABC) subfamily B member 1 (ABCB1; P-glycoprotein; MDR1) in some types of cancer cells is one of the mechanisms responsible for the development of multidrug resistance (MDR), which leads to the failure of chemotherapy. Therefore, it is important to inhibit the activity or reduce the expression level of ABCB1 to maintain an effective intracellular level of chemotherapeutic drugs. In this study, we found that rutaecarpine, a bioactive alkaloid isolated from Evodia Rutaecarpa, has the capacity to reverse ABCB1-mediated MDR. Our data indicated that the reversal effect of rutaecarpine was related to the attenuation of the protein level of ABCB1. Mechanistically, we demonstrated that ABCB1 is a newly discovered substrate of E3 ubiquitin ligase membrane-associated RING-CH 8 (MARCH8). MARCH8 can interact with ABCB1 and promote its ubiquitination and degradation. In short, rutaecarpine increased the degradation of ABCB1 protein by upregulating the protein level of MARCH8, thereby antagonizing ABCB1-mediated MDR. Notably, the treatment of rutaecarpine combined with other anticancer drugs exhibits a therapeutic effect on transplanted tumors. Therefore, our study provides a potential chemotherapeutic strategy of co-administrating rutaecarpine with other conventional chemotherapeutic agents to overcome MDR and improve therapeutic effect.

Novel CAR T therapy is a ray of hope in the treatment of seriously ill AML patients

Acute myeloid leukemia (AML) is a serious, life-threatening, and hardly curable hematological malignancy that affects the myeloid cell progenies and challenges patients of all ages but mostly occurs in adults. Although several therapies are available including chemotherapy, allogeneic hematopoietic stem cell transplantation (alloHSCT), and receptor-antagonist drugs, the 5-year survival of patients is quietly disappointing, less than 30%. alloHSCT is the major curative approach for AML with promising results but the treatment has severe adverse effects such as graft-versus-host disease (GVHD). Therefore, as an alternative, more efficient and less harmful immunotherapy-based approaches such as the adoptive transferring T cell therapy are in development for the treatment of AML. As such, chimeric antigen receptor (CAR) T cells are engineered T cells which have been developed in recent years as a breakthrough in cancer therapy. Interestingly, CAR T cells are effective against both solid tumors and hematological cancers such as AML. Gradually, CAR T cell therapy found its way into cancer therapy and was widely used for the treatment of hematologic malignancies with successful results particularly with somewhat better results in hematological cancer in comparison to solid tumors. The AML is generally fatal, therapy-resistant, and sometimes refractory disease with a disappointing low survival rate and weak prognosis. The 5-year survival rate for AML is only about 30%. However, the survival rate seems to be age-dependent. Novel CAR T cell therapy is a light at the end of the tunnel. The CD19 is an important target antigen in AML and lymphoma and the CAR T cells are engineered to target the CD19. In addition, a lot of research goes on the discovery of novel target antigens with therapeutic efficacy and utilizable for generating CAR T cells against various types of cancers. In recent years, many pieces of research on screening and identification of novel AML antigen targets with the goal of generation of effective anti-cancer CAR T cells have led to new therapies with strong cytotoxicity against cancerous cells and impressive clinical outcomes. Also, more recently, an improved version of CAR T cells which were called modified or smartly reprogrammed CAR T cells has been designed with less unwelcome effects, less toxicity against normal cells, more safety, more specificity, longer persistence, and proliferation capability. The purpose of this review is to discuss and explain the most recent advances in CAR T cell-based therapies targeting AML antigens and review the results of preclinical and clinical trials. Moreover, we will criticize the clinical challenges, side effects, and the different strategies for CAR T cell therapy.

Anticancer Activity and In Vitro to In Vivo Mechanistic Recapitulation of Novel Ruthenium-Based Metallodrugs in the Zebrafish Model

Ruthenium is popular as a metal core for chemotherapeutics, due to versatile molecular coordination. Because new metallodrugs are synthesized at high rates, our studies included assays in zebrafish to expedite the initial evaluation as anticancer agents. Here we evaluated novel metallodrugs (PMC79 and LCR134), and cisplatin, a widely used platinum-based chemotherapeutic. We hypothesized that this model could characterize anticancer properties and recapitulate previous in vitro results in vivo. Our findings suggest anticancer properties of PMC79 and LCR134 were similar with less toxicity than cisplatin. Exposures from 24 to 72 h at or below the LOAELs of PMC79 and LCR134 (3.9 µM and 13.5 µm, respectively), impaired blood vessel development and tailfin regeneration. Blood vessel examination through live imaging of larvae revealed distinct regional antiangiogenic impacts. The significant decrease in gene expression of the VEGF-HIF pathway and beta-actin could explain the morphological effects observed in the whole organism following exposure. Tailfin amputation in larvae exposed to PMC79 or LCR134 inhibited tissue regrowth and cell division, but did not impact normal cell proliferation unlike cisplatin. This suggests Ru drugs may be more selective in targeting cancerous cells than cisplatin. Additionally, in vitro mechanisms were confirmed. PMC79 disrupted cytoskeleton formation in larvae and P-glycoprotein transporters in vivo was inhibited at low doses which could limit off-target effects of chemotherapeutics. Our results demonstrate the value for using the zebrafish in metallodrug research to evaluate mechanisms and off-target effects. In light of the findings reported in this article, future investigation of PMC79 and LCR134 are warranted in higher vertebrate models.

A comparative study of anti-leukemic effects of kaempferol and epigallocatechin-3-gallate (EGCG) on human leukemia HL-60 cells

OBJECTIVE

Acute promyelocytic leukemia (APL) is among the most threatening hematological malignant cancers. Defects in cell growth and apoptotic pathways lead to the pathogenesis of the disease as well as its resistance to therapy; therefore, it is a good model for examining pro-apoptotic agents. The present study compared the molecular mechanism induced by kaempferol and epigallocatechin gallate (EGCG) as well as all-trans retinoic acid (ATRA), in HL-60 leukemia cells during five days.

MATERIALS AND METHODS

Cell viability was determined by resazurin assay following treatment with ATRA (10 µM), EGCG, and kaempferol (12.5-100 µM), and apoptosis was detected by the ANX V/PI kit. Moreover, the levels of genes involved in apoptosis (PI3K, AKT, BCL2, BAX, P21, PTEN, CASP3, CASP8, and CASP9) and multi-drug resistance (MDR, ABCB1 and ABCC1) were assessed by using real-time PCR test.

RESULTS

Based on the findings, kaempferol decreased cell viability and increased apoptosis in HL60 cells more than EGCG. Apoptosis was induced via extrinsic and intrinsic pathways in HL60 cells by kaempferol and EGCG. In addition, kaempferol and EGCG increased apoptosis and inhibited MDR in a concentration- and time-dependent manner.

CONCLUSION

Kaempferol at high concentrations can be taken into consideration for treating patients with APL as compared with EGCG.

Targeting cancer epigenetic pathways with small-molecule compounds: Therapeutic efficacy and combination therapies

Epigenetics mainly refers to covalent modifications to DNA or histones without affecting genomes, which ultimately lead to phenotypic changes in cells or organisms. Given the abundance of regulatory targets in epigenetic pathways and their pivotal roles in tumorigenesis and drug resistance, the development of epigenetic drugs holds a great promise for the current cancer therapy. However, lack of potent, selective, and clinically tractable small-molecule compounds makes the strategy to target cancer epigenetic pathways still challenging. Therefore, this review focuses on epigenetic pathways, small molecule inhibitors targeting DNA methyltransferase (DNMT) and small molecule inhibitors targeting histone modification (the main regulatory targets are histone acetyltransferases (HAT), histone deacetylases (HDACs) and histone methyltransferases (HMTS)), as well as the combination strategies of the existing epigenetic therapeutic drugs and more new therapies to improve the efficacy, which will shed light on a new clue on discovery of more small-molecule drugs targeting cancer epigenetic pathways as promising strategies in the future.

High HSPA8 expression predicts adverse outcomes of acute myeloid leukemia

Background

Acute myeloid leukemia (AML) remains one of the most common hematological malignancies, posing a serious challenge to human health. HSPA8 is a chaperone protein that facilitates proper protein folding. It contributes to various activities of cell function and also is associated with various types of cancers. To date, the role of HSPA8 in AML is still undetermined.

Methods

In this study, public datasets available from the TCGA (Cancer Genome Atlas) and GEO (Gene Expression Omnibus) were mined to discover the association between the expression of HSPA8 and clinical phenotypes of CN-AML. A series of bioinformatics analysis methods, including functional annotation and miRNA-mRNA regulation network analysis, were employed to investigate the role of HSPA8 in CN-AML.

Results

HSPA8 was highly expressed in the AML patients compared to the healthy controls. The high HSPA8 expression had lower overall survival (OS) rate than those with low HSPA8 expression. High expression of HSPA8 was also an independent prognostic factor for overall survival (OS) of CN-AML patients by multivariate analysis. The differential expressed genes (DEGs) associated with HSPA8 high expression were identified, and they were enriched PI3k-Akt signaling, cAMP signaling, calcium signaling pathway. HSPA8 high expression was also positively associated with micro-RNAs (hsa-mir-1269a, hsa-mir-508-3p, hsa-mir-203a), the micro-RNAs targeted genes (VSTM4, RHOB, HOBX7) and key known oncogenes (KLF5, RAN, and IDH1), and negatively associated with tumor suppressors (KLF12, PRKG1, TRPS1, NOTCH1, RORA).

Conclusions

Our research revealed HSPA8 as a novel potential prognostic factor to predict the survival of CN-AML patients. Our data also revealed the possible carcinogenic mechanism and the complicated microRNA-mRNA network associated with the HSPA8 high expression in AML.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08193-w.

Cyclodextrin-Based Hybrid Polymeric Complex to Overcome Dual Drug Resistance Mechanisms for Cancer Therapy

Drug resistance always reduces the efficacy of chemotherapy, and the classical mechanisms of drug resistance include drug pump efflux and anti-apoptosis mediators-mediated non-pump resistance. In addition, the amphiphilic polymeric micelles with good biocompatibility and high stability have been proven to deliver the drug molecules inside the cavity into the cell membrane regardless of the efflux of the cell membrane pump. We designed a cyclodextrin (CD)-based polymeric complex to deliver chemotherapeutic doxorubicin (DOX) and Nur77ΔDBD gene for combating pumps and non-pump resistance simultaneously. The natural cavity structure of the polymeric complex, which was comprised with β-cyclodextrin-graft-(poly(ε-caprolactone)-adamantly (β-CD-PCL-AD) and β-cyclodextrin-graft-(poly(ε-caprolactone)-poly(2-(dimethylamino) ethyl methacrylate) (β-CD-PCL-PDMAEMA), can achieve the efficient drug loading and delivery to overcome pump drug resistance. The excellent Nur77ΔDBD gene delivery can reverse Bcl-2 from the tumor protector to killer for inhibiting non-pump resistance. The presence of terminal adamantyl (AD) could insert into the cavity of β-CD-PCL-PDMAEMA via host-guest interaction, and the releasing rate of polymeric inclusion complex was higher than that of the individual β-CD-PCL-PDMAEMA. The polymeric inclusion complex can efficiently deliver the Nur77ΔDBD gene than polyethylenimine (PEI-25k), which is a golden standard for nonviral vector gene delivery. The higher transfection efficacy, rapid DOX cellular uptake, and significant synergetic tumor cell viability inhibition were achieved in a pump and non-pump drug resistance cell model. The combined strategy with dual drug resistance mechanisms holds great potential to combat drug-resistant cancer.

Overexpression of BAMBI and SMAD7 impacts prognosis of acute myeloid leukemia patients: A potential TERT non-canonical role

BACKGROUND

Bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) and mothers against decapentaplegic homolog 7 (SMAD7) are important transforming growth factor-β (TGF-β) signaling antagonists, however their roles in acute myeloid leukemia (AML) remains unclear. Telomerase reverse transcriptase (TERT) may be involved in regulating BAMBI and SMAD7 expressions; a role beyond telomeres that is not clinically validated yet.

OBJECTIVE

In this study, we examined the expression levels and prognostic values of BAMBI, SMAD7 and TERT and their association with AML patients' outcomes.

METHODS

Blood samples were collected from 74 de-novo AML patients and 16 controls. Real-time quantitative PCR (qRT-PCR) was performed to analyze BAMBI, SMAD7 and TERT expressions.

RESULTS

BAMBI and SMAD7 expression in AML were significantly upregulated versus controls (p< 0.05). BAMBI, SMAD7 and TERT levels were significantly correlated together (p< 0.001). Kaplan-Meier analysis indicated that patients with high BAMBI, SMAD7 and TERT expression levels had markedly shorter event free survival (EFS) and overall survival (OS) time (p< 0.01). Furthermore, multivariate analysis revealed that only high BAMBI expression was an independent risk factor for OS (p= 0.001).

CONCLUSIONS

BAMBI is a novel biomarker in predicting prognosis in AML patients. Moreover, a potential interplay is found between BAMBI, SMAD7 and TERT in AML pathogenies.

Targeting tumor resistance mechanisms

Cancer develops resistance to treatments through many mechanisms. Single-cell analyses reveal the intratumor heterogeneity and dynamic relationships between cancer cell subpopulations. These analyses also highlight that various mechanisms of resistance may coexist in a given tumor. Studies have unraveled how the microenvironment affects tumor response to treatments and how cancer cells may adapt to these treatments. Though challenging, individualized treatment based on the molecular characterization of the tumor should become the new standard of care. In the meantime, the success rate of clinical trials in oncology remains dramatically low. There is a need to do better and improve the predictability of preclinical models. This requires innovative changes in ex vivo models and the culture system currently being used. An innovative ligand design is also urgently needed. The limited arsenal of medicinal chemistry reactions and the biases of scaffold selection favor structurally similar compounds with linear shapes at the expense of disc and spherical shapes, which leave a large chemical shape space untouched. In this regard, venoms have received increasing interest as a wellspring for drug candidates. Overall, the characterization of tumor heterogeneity has contributed to advancing our understanding of the mechanisms that underlie cancer resistance to treatments. Targeting these mechanisms will require setting key milestones to significantly improve the translatability of preclinical studies to the clinic with the hope of increasing the success rate of clinical trials.

Pentraxin 3 acts as a functional effector of Akt/NF-κB signaling to modulate the progression and cisplatin-resistance in non-small cell lung cancer

Pentraxin 3 (PTX3) has been documented to be involved in the development of chemoresistance, however, the mechanisms by which it regulates cisplatin (DDP) resistance in non-small cell lung cancer (NSCLC) have never been elucidated. Quantitative reverse transcriptase polymerase chain reaction and Western blot were carried to determine the expression of PTX3, ATP-binding cassette sub-family B member 1 (ABCB1)/P-glycoprotein 1 (p-gp), protein kinase B (Akt), phosphorylated Akt and nuclear factor-kappa B (NF-кB) p65. The biological roles of PTX3 in NSCLC progression and NSCLC cell resistance to DDP were evaluated using enzyme-linked immunosorbent assay, cell count kit-8, colony formation assay, flow cytometry, as well as xenograft tumor assay. The expression of PTX3 was increased in the serum of NSCLC patients as well as in NSCLC cell lines. Lower PTX3 level was associated with longer overall survival in lung adenocarcinoma and lung squamous cell carcinoma patients. Furthermore, PTX3 expression was greatly higher in DDP-resistant NSCLC cells than that in NSCLC cells. Silencing of PTX3 restrained the proliferation and promoted the apoptosis of NSCLC cells, as well as sensitized DDP-resistant NSCLC cells to DDP. Additionally, knockdown of PTX3 inhibited the growth of NSCLC tumors in vivo. Upregulation of PTX3 expression was dependent on the activation of Akt/NF-κB signaling. The induction of apoptosis by PTX3 knockdown was enhanced by MK-2206 or JSH-23. In conclusion, knockdown of PTX3 restrained the progression of NSCLC and sensitized NSCLC cells towards DDP, which provides a potential target to restore DDP chemoresponse.

Overexpression of LncRNA-HOTAIR promotes chemoresistance in acute leukemia cells

Chemotherapy treatment of acute myeloid leukemia (AML) can be compromised due to the multidrug resistance (MDR) of leukemia cells. HOTAIR, a long noncoding RNA (LncRNA), is involved in MDR development of various solid tumors. However, whether it functions in MDR development of leukemia remains unclear. In this study, expressions of HOTAIR in leukemia cell line K562/A02 and bone marrow samples from 10 patients with refractory and relapsed AML were detected by qRT-PCR. The apoptosis, proliferation, and susceptibility of K562/A02 cells to Adriamycin (ADR) were analyzed by flow cytometry and CCK8 assay, respectively. The expression of cell cycle regulator P21 and Notch1 in the K562/A02 cells was examined by qRT-PCR. The accumulation of total AKT and the phosphorylated AKT (pAKT^S473) were detected by western blotting. We found that the expression of HOTAIR in drug-resistant cells and patient samples was increased. Inhibition of HOTAIR expression could suppress the proliferation, increase the apoptosis, and promote the doxorubicin sensitivity of K562/A02 cells. Moreover, inhibiting expression of HOTAIR could attenuate the expression of P21 and Notch1 and inhibit the phosphorylation of AKT in drug-resistant cells. In conclusion, our results demonstrated that LncRNA-HOTAIR is involved in MDR development of leukemia cells by regulating the expression of P21 and the AKT/Notch1 signaling pathway.

Silencing long non-coding RNA XIST suppresses drug resistance in acute myeloid leukemia through down-regulation of MYC by elevating microRNA-29a expression

Background

Long non-coding RNAs (lncRNAs) are biomarkers participating in multiple disease development including acute myeloid leukemia (AML). Here, we investigated molecular mechanism of X Inactive-Specific Transcript (XIST) in regulating cellular viability, apoptosis and drug resistance in AML.

Methods

XIST, miR-29a and myelocytomatosis oncogene (MYC) expression in AML bone marrow cells collected from 62 patients was evaluated by RT-qPCR and Western blot analysis. Besides, the relationship among XIST, miR-29a and MYC was analyzed by dual luciferase reporter assay, RIP, and RNA pull down assays. AML KG-1 cells were treated with anti-tumor drug Adriamycin. The role of XIST/miR-29a/MYC in cellular viability, apoptosis and drug resistance in AML was accessed via gain- and loss-of-function approaches. At last, we evaluated role of XIST/miR-29a/MYC on tumorigenesis in vivo.

Results

XIST and MYC were up-regulated, and miR-29a was down-regulated in AML bone marrow cells. Silencing XIST inhibited cellular activity and drug resistance but promoted cellular apoptosis of KG-1 cells by down-regulating MYC. XIST inhibited miR-29a expression to up-regulate MYC. Moreover, silencing XIST inhibited tumorigenesis of AML cells in vivo.

Conclusions

Overall, down-regulation of XIST decreased MYC expression through releasing the inhibition on miR-29a, thereby reducing drug resistance, inhibiting viability and promoting apoptosis of AML cells.

Therapeutic targeting of FLT3 and associated drug resistance in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous disease caused by several gene mutations and cytogenetic abnormalities affecting differentiation and proliferation of myeloid lineage cells. FLT3 is a receptor tyrosine kinase commonly overexpressed or mutated, and its mutations are associated with poor prognosis in AML. Although aggressive chemotherapy often followed by hematopoietic stem cell transplant is the current standard of care, the recent approval of FLT3-targeted drugs is revolutionizing AML treatment that had remained unchanged since the 1970s. However, despite the dramatic clinical response to targeted agents, such as FLT3 inhibitors, remission is almost invariably short-lived and ensued by relapse and drug resistance. Hence, there is an urgent need to understand the molecular mechanisms driving drug resistance in order to prevent relapse. In this review, we discuss FLT3 as a target and highlight current understanding of FLT3 inhibitor resistance.

Targeted nanopore sequencing for the identification of ABCB1 promoter translocations in cancer

BACKGROUND

Resistance to chemotherapy is the most common cause of treatment failure in acute myeloid leukemia (AML) and the drug efflux pump ABCB1 is a critical mediator. Recent studies have identified promoter translocations as common drivers of high ABCB1 expression in recurrent, chemotherapy-treated high-grade serous ovarian cancer (HGSC) and breast cancer. These fusions place ABCB1 under the control of a strong promoter while leaving its open reading frame intact. The mechanisms controlling high ABCB1 expression in AML are largely unknown. We therefore established an experimental system and analysis pipeline to determine whether promoter translocations account for high ABCB1 expression in cases of relapsed human AML.

METHODS

The human AML cell line THP-1 was used to create a model of chemotherapy resistance in which ABCB1 expression was driven by a promoter fusion. The THP-1 model was used to establish a targeted nanopore long-read sequencing approach that was then applied to cases of ABCB1high HGSC and AML. H3K27Ac ChIP sequencing was used to assess the activity of native promoters in cases of ABCB1high AML.

RESULTS

Prolonged in vitro daunorubicin exposure induced activating ABCB1 promoter translocations in human THP-1 AML cells, similar to those recently described in recurrent high-grade serous ovarian and breast cancers. Targeted nanopore sequencing proved an efficient method for identifying ABCB1 structural variants in THP-1 AML cells and HGSC; the promoter translocations identified in HGSC were both previously described and novel. In contrast, activating ABCB1 promoter translocations were not identified in ABCB1high AML; instead H3K27Ac ChIP sequencing demonstrated active native promoters in all cases studied.

CONCLUSIONS

Despite frequent high level expression of ABCB1 in relapsed primary AML we found no evidence of ABCB1 translocations and instead confirmed high-level activity of native ABCB1 promoters, consistent with endogenous regulation.

Chemical molecular-based approach to overcome multidrug resistance in cancer by targeting P-glycoprotein (P-gp)

Multidrug resistance (MDR) remains one of the major impediments for efficacious cancer chemotherapy. Increased efflux of multiple chemotherapeutic drugs by transmembrane ATP-binding cassette (ABC) transporter superfamily is considered one of the primary causes for cancer MDR, in which the role of P-glycoprotein (P-gp/ABCB1) has been most well-established. The clinical co-administration of P-gp drug efflux inhibitors, in combination with anticancer drugs which are P-gp transport substrates, was considered to be a treatment modality to surmount MDR in anticancer therapy by blocking P-gp-mediated multidrug efflux. Extensive attempts have been carried out to screen for sets of nontoxic, selective, and efficacious P-gp efflux inhibitors. In this review, we highlight the recent achievements in drug design, characterization, structure-activity relationship (SAR) studies, and mechanisms of action of the newly synthetic, potent small molecules P-gp inhibitors in the past 5 years. The development of P-gp inhibitors will increase our knowledge of the mechanisms and functions of P-gp-mediated drug efflux which will benefit drug discovery and clinical cancer therapeutics where P-gp transporter overexpression has been implicated in MDR.

Putative molecular determinants mediating sensitivity or resistance towards carnosic acid tumor cell responses

BACKGROUND

Carnosic acid (CA) is one of the main constituents in rosemary extract. It possesses valuable pharmacological properties, including anti-oxidant, anti-inflammatory, anti-microbial and anti-cancer activities. Numerous in vitro and in vivo studies investigated the anticancer profile of CA and emphasized its potentiality for cancer treatment. Nevertheless, the role of multidrug-resistance (MDR) related mechanisms for CA's anticancer effect is not yet known.

PURPOSE

We investigated the cytotoxicity of CA against known mechanisms of anticancer drug resistance (P-gp, ABCB5, BCRP, EGFR and p53) and determined novel putative molecular factors associated with cellular response towards CA.

STUDY DESIGN

Cytotoxicity assays, bioinformatic analysis, flow cytometry and western blotting were performed to identify the mode of action of CA towards cancer cells.

METHODS

The cytotoxicity to CA was assessed using the resazurin assays in cell lines expressing the mentioned resistance mechanisms. A pharmacogenomic characterization of the NCI 60 cell line panel was applied via COMPARE, hierarchical cluster and network analyses. Flow cytometry was used to detect cellular mode of death and ROS generation. Changes in proteins-related to apoptosis were determined by Western blotting.

RESULTS

Cell lines expressing ABC transporters (P-gp, BCRP or ABCB5), mutant EGFR or p53 were not cross-resistant to CA compared to their parental counterparts. By pharmacogenomic approaches, we identified genes that belong to different functional groups (e.g. signal transduction, regulation of cytoskeleton and developmental regulatory system). These genes were predicted as molecular determinants that mediate CA tumor cellular responses. The top affected biofunctions included cellular development, cellular proliferation and cellular death and survival. The effect of CA-mediated apoptosis in leukemia cells, which were recognized as the most sensitive tumor type, was confirmed via flow cytometry and western blot analysis.

CONCLUSION

CA may provide a novel treatment option to target refractory tumors and to effectively cooperate with established chemotherapy. Using pharmacogenomic approaches and network pharmacology, the relationship between cancer complexity and multi-target potentials of CA was analyzed and many putative molecular determinants were identified. They could serve as novel targets for CA and further studies are needed to translate the possible implications to clinical cancer treatment.

KD025, an anti-adipocyte differentiation drug, enhances the efficacy of conventional chemotherapeutic drugs in ABCG2-overexpressing leukemia cells

Most patients with advanced leukemia eventually die from multidrug resistance (MDR). Chemotherapy-resistant leukemia cells may lead to treatment failure and disease relapse. Overexpression of ATP-binding cassette subfamily G member 2 (ABCG2) leads to MDR, which serves as a potential biomarker and target of therapeutic intervention for leukemia cells. Targeting ABCG2 is a potential strategy for selective therapy and eradicate MDR cells, thus improving malignant leukemia treatment. KD025 (SLx-2119) is a novel Rho-associated protein kinase 2-selective inhibitor, which has been shown to inhibit adipogenesis in human adipose-derived stem cells and restore impaired immune homeostasis in autoimmunity therapy. The present study demonstrated that KD025 improved the efficacy of antineoplastic drugs in ABCG2-overexpressing leukemia cells and primary leukemia blast cells derived from patients with leukemia. Moreover, KD025 significantly inhibited the efflux of [³H]-mitoxantrone and hence accumulated higher levels of [³H]-mitoxantrone in HL60/ABCG2 cells. However, mechanistic research indicated that KD025 did not alter the protein levels and subcellular locations of ABCG2. KD025 may restrain the efflux activity of ABCG2 by obstructing ATPase activity. Taken together, KD025 can sensitize conventional antineoplastic drugs in ABCG2-overexpressing leukemia cells by blocking the pump function of ABCG2 protein. The present findings may provide a novel and useful combinational therapeutic strategy of KD025 and antineoplastic drugs for leukemia patients with ABCG2-mediated MDR.

Melatonin increases the chemosensitivity of diffuse large B-cell lymphoma cells to epirubicin by inhibiting P-glycoprotein expression via the NF-κB pathway

Background

Epirubicin is a first-line chemotherapeutic drug for the clinical treatment of diffuse large B cell lymphoma (DLBCL), but the overexpression of multidrug resistance (MDR) transporter proteins, especially P-glycoprotein (P-gp), renders epirubicin ineffective. Some studies reveal the potential role of melatonin in chemotherapeutic synergy and MDR.

Methods

The cell viability and apoptosis were determined by CCK-8 assay and acridine orange/ethidium bromide (AO/EB) fluorescence staining assay. Immunofluorescence and immunohistochemical staining were used to detect the expression of P-gp in DLBCL cells and tissues. Rhodamine-123 accumulation assay was used to evaluate the pump function of P-gp. The possible mechanisms of melatonin sensitize DLBCL cells to epirubicin were explored by western blotting, cytochrome C release, and pulldown assay.

Results

Melatonin significantly enhanced the epirubicin-induced cell proliferation suppression, epirubicin-induced apoptosis, and reduced the IC50 value of epirubicin. Further, melatonin synergized with epirubicin to promote the activation of the mitochondria-mediated apoptosis pathway and increased the accumulation of epirubicin in DLBCL cells by inhibiting the expression and function of P-gp. Immunohistochemical staining studies revealed that P-gp expression was positively correlated with P65 expression. Epirubicin was subsequently discovered to upregulate the expression of P-gp by activating the NF-κB pathway in the DLBCL cells. Melatonin reduced the amount of P65 protein in the nucleus and abrogated the ability of P65 to bind to the ABCB1 promoter, decisively suppressing P-gp expression.

Conclusions

Our results demonstrated that melatonin inactivates the NF-κB pathway and downregulates the expression of P-gp, ultimately sensitizing DLBCL cells to the epirubicin that suppresses their growth.

Association of three factors (ABCB1 gene expression, steroid response, early response at day + 8) on the response to induction in patients with acute lymphoblastic leukemia

Treatment of acute lymphoblastic leukemia (ALL) requires the combination of multiple drugs to integrate a complete remission. The different prognostic factors (age, leukocytes, risk, cytogenetic alterations) allow identifying those patients with a high risk of relapse, but there are few described factors that impact the induction response. The objective was to identify the utility of different risk factors (overexpression of the ABCB1 drug resistance gene, favorable response to steroids (FRS) and early response at day + 8 of treatment) on the percentage of complete remissions and overall survival. This is a prospective, observational study in adult patients with B-ALL without specific cytogenetic alterations, who started induction treatment based on a pretreatment with prednisone and subsequently vincristine (1.6 mg/m² subcutaneous) plus daunorubicin (45 mg/m² subcutaneously) on days + 1, + 8, + 15. The ABCB1 resistance gene was evaluated at diagnosis, the FRS at the end of the pretreatment and the early response during day + 8. A total of 53 adult patients diagnosed with ALL Philadelphia negative chromosome (Ph^-), with immunophenotype B, with a normal karyotype, were studied. Cases with genetic abnormalities with a poor prognosis were excluded in order to reduce bias. The mean age was 48 years (range 17-68 years). 62.3% of patients were at high risk of relapse. When analyzing the risk factors, 30.2% showed high levels of the ABCB1 resistance gene, without showing an impact on the induction response (OR: 1.218, p = 0.743), but its overexpression was associated with a poor response to steroids as in the absence of early response. Individually, both the FRS (OR: 5.7, p = 0.004) and the absence of early response to day + 8 (OR: 6.42, p = 0.002) showed significance. By combining the different factors, having more than 2 was directly related to a failure (OR: 9.514, p = 0.000). The identification of factors such as FRS such as the persistence of blasts at the end of the first week of treatment is useful to identify patients at risk of failure in induction.

Chidamide, decitabine, cytarabine, aclarubicin, and granulocyte colony-stimulating factor (CDCAG) in patients with relapsed/refractory acute myeloid leukemia: a single-arm, phase 1/2 study

Background

Epigenetic mechanisms play an important role in the chemoresistance of acute myeloid leukemia (AML). The clinical response to epigenetic modifier-based chemotherapy in patients with relapsed/refractory AML (r/r AML) is unclear. This multicenter clinical trial evaluated the safety and efficacy of epigenetic modifiers (chidamide and decitabine) in combination with aclarubicin, cytarabine, and granulocyte colony-stimulating factor (G-CSF) in patients with r/r AML.

Results

Adult patients with r/r AML were treated with chidamide, decitabine, cytarabine, aclarubicin, and G-CSF (CDCAG). The primary measures were overall response (OR), overall survival (OS), and safety. Next-generation sequencing was performed to analyze the correlation between gene mutations and response. A total of 93 patients with r/r AML were enrolled. Overall, 24 patients had a complete remission (CR) and 19 patients achieved CR with incomplete blood count recovery (CRi). The overall response rate (ORR) was 46.2%. The overall survival of these 43 patients who achieved CR/CRi was significantly longer than that of patients who failed to achieve remission (563 vs 152 days, P < 0.0001). Of the patients with mutations in epigenetic and transcription factor-related genes, but without internal tandem duplications in FMS-like tyrosine kinase3 (FLT3-ITDs), 55.6% achieved CR/CRi, whereas the ORR was 28.2% for patients with mutations in other genes.

Conclusions

The CDCAG regimen was well tolerated and effective in r/r AML. Patients with epigenetic and transcription factor-related gene mutations, but without FLT3-ITD mutations, may benefit from this regimen.

Trial registration

Clinical Trials, NCT02886559. Registered 01 September 2016

Therapeutic Target Discovery Using High-Throughput Genetic Screens in Acute Myeloid Leukemia

The development of high-throughput gene manipulating tools such as short hairpin RNA (shRNA) and CRISPR/Cas9 libraries has enabled robust characterization of novel functional genes contributing to the pathological states of the diseases. In acute myeloid leukemia (AML), these genetic screen approaches have been used to identify effector genes with previously unknown roles in AML. These AML-related genes centralize alongside the cellular pathways mediating epigenetics, signaling transduction, transcriptional regulation, and energy metabolism. The shRNA/CRISPR genetic screens also realized an array of candidate genes amenable to pharmaceutical targeting. This review aims to summarize genes, mechanisms, and potential therapeutic strategies found via high-throughput genetic screens in AML. We also discuss the potential of these findings to instruct novel AML therapies for combating drug resistance in this genetically heterogeneous disease.