mRNA expression profile of multidrug-resistant genes in acute lymphoblastic leukemia of children, a prognostic value for ABCA3 and ABCA2

Role of epigenetics in paediatric cancer pathogenesis & drug resistance

Paediatric oncogenesis is tightly intertwined with errors in developmental processes involving cell specification and differentiation, which are governed by intricate temporal epigenetic signals. As paediatric cancers are characterised by a low number of somatic mutations, dysregulated chromatin landscapes are believed to be key drivers of oncogenesis. Epigenetic dysregulation is induced by mutations and aberrant expression of histones and epigenetic regulatory genes, to altered DNA methylation patterns and dysregulated noncoding RNA expression. In this review, we discuss epigenetic alterations in paediatric cancer oncogenesis and recurrence, and their potential as diagnostic biomarkers. We also discuss various epigenetic drugs that have entered clinical trials for aggressive paediatric cancers. Targeting paediatric-specific epigenetic vulnerabilities may improve recurrence-free survival in high-risk cancers.

Meningeal leukaemic aggregates as foci of cell expansion and chemoresistance in acute lymphoblastic leukaemia metastasis

PURPOSE

Central nervous system (CNS) involvement and/or relapse remains one of the most important causes of morbidity/mortality in paediatric B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) patients. To identify novel therapeutic targets and develop less aggressive therapies, a better understanding of the cellular and molecular microenvironment in leptomeningeal metastases is key. Here, we aimed to investigate the formation of metastatic leptomeningeal aggregates and their relevance to the expansion, survival and chemoresistance acquisition of leukaemia cells.

METHODS

We used BCP-ALL xenograft mouse models, combined with immunohistofluorescence and flow cytometry, to study the development of CNS metastasis and the contribution of leptomeningeal cells to the organisation of leukaemic aggregates. To in vitro mimic the CNS metastasis, we established co-cultures of three-dimensional (3D) ALL cell spheroids and human leptomeningeal cells (hLMCs) and studied the effects on gene expression, proliferation, cytokine production, and chemoresistance.

RESULTS

In xenografted mice, ALL cells infiltrated the CNS at an early stage and, after crossing an ER-TR7+ fibroblast-like meningeal cell layer, they proliferated extensively and formed large vascularised leukaemic aggregates supported by a network of podoplanin+ leptomeningeal cells. In leukaemia spheroid-hLMC co-cultures, unlike conventional 2D co-cultures, meningeal cells strongly promoted the proliferation of leukaemic cells and generated a pro-inflammatory microenvironment. Furthermore, in 3D cell aggregates, leukaemic cells also developed chemoresistance, at least in part due to ABC transporter up-regulation.

CONCLUSION

Our results provide evidence for the formation of metastatic ALL-leptomeningeal cell aggregates, their pro-inflammatory profile and their contribution to leukaemic cell expansion, survival and chemoresistance in the CNS.

The association of ABC proteins with multidrug resistance in cancer

Multidrug resistance (MDR) poses one of the primary challenges for cancer treatment, especially in cases of metastatic disease. Various mechanisms contribute to MDR, including the overexpression of ATP-binding cassette (ABC) proteins. In this context, we reviewed the literature to establish a correlation between the overexpression of ABC proteins and MDR in cancer, considering both in vitro and clinical studies. Initially, we presented an overview of the seven subfamilies of ABC proteins, along with the subcellular localization of each protein. Subsequently, we identified a panel of 20 ABC proteins (ABCA1-3, ABCA7, ABCB1-2, ABCB4-6, ABCC1-5, ABCC10-11, ABCE1, ABCF2, ABCG1, and ABCG2) associated with MDR. We also emphasize the significance of drug sequestration by certain ABC proteins into intracellular compartments. Among the anticancer drugs linked to MDR, 29 were definitively identified as substrates for at least one of the three most crucial ABC transporters: ABCB1, ABCC1, and ABCG2. We further discussed that the most commonly used drugs in standard regimens for mainly breast cancer, lung cancer, and acute lymphoblastic leukemia could be subject to MDR mediated by ABC transporters. Collectively, these insights will aid in conducting new studies aimed at a deeper understanding of the clinical MDR mediated by ABC proteins and in designing more effective pharmacological treatments to enhance the objective response rate in cancer patients.

Exploring bile acid transporters as key players in cancer development and treatment: Evidence from preclinical and clinical studies

Bile acid transporters (BATs) are integral membrane proteins belonging to various families, such as solute carriers, organic anion transporters, and ATP-binding cassette families. These transporters play a crucial role in bile acid transportation within the portal and systemic circulations, with expression observed in tissues, including the liver, kidney, and small intestine. Bile acids serve as signaling molecules facilitating the absorption and reabsorption of fats and lipids. Dysregulation of bile acid concentration has been implicated in tumorigenesis, yet the role of BATs in this process remains underexplored. Emerging evidence suggests that BATs may modulate various stages of cancer progression, including initiation, development, proliferation, metastasis, and tumor microenvironment regulation. Targeting BATs using siRNAs, miRNAs, and small compound inhibitors in preclinical models and their polymorphisms are well-studied for transporters like BSEP, MDR1, MRP2, OATP1A2, etc., and have shed light on their involvement in tumorigenesis, particularly in cancers such as those affecting the liver and gastrointestinal tract. While BATs' role in diseases like Alagille syndrome, biliary atresia, and cirrhosis have been extensively studied, their implications in cancer warrant further investigation. This review highlights the expression and function of BATs in cancer development and emphasizes the potential of targeting these transporters as a novel therapeutic strategy for various malignancies.

Targeting nucleolin improves sensitivity to chemotherapy in acute lymphoblastic leukemia

PURPOSE

Most patients with acute lymphoblastic leukemia (ALL) are treated with chemotherapy as primary care. Although the treatment response is usually positive, resistance and relapse often occur via unknown mechanisms. The purpose of this study was to identify factors associated with chemotherapy resistance in ALL. Here, we present clinical and experimental evidence that overexpression of nucleolin (NCL), a multifunctional nucleolar protein, is linked to drug resistance in ALL.

METHODS

NCL mRNA and protein levels were compared between cell lines and patient samples using qRT-PCR and immunoblotting. NCL mRNA levels were compared between patients of different disease stages from our clinic patients' specimens and publicly available ALL patient datasets. Cells and patient-derived xenograft mouse experiments were performed to assess the effect of NCL inhibition on ALL chemotherapy effectiveness.

RESULTS

Analysis of patient specimens, and publicly available RNA-sequencing datasets revealed a strong correlation between the abundance of NCL and disease relapse or poor survival in B-ALL. Altering NCL expression results in changes in drug sensitivity in ALL cell lines. High levels of NCL upregulated components of the ATP-binding cassette transporters via activation of the ERK pathway, resulting in a decrease in drug accumulation inside the cells. Targeting NCL with AS1411, an NCL-binding oligonucleotide aptamer, significantly increased the sensitivity of ALL cell lines and cells/patient-derived ALL xenograft mice to chemotherapeutic drugs and prolonged mouse survival.

CONCLUSION

Our results highlight NCL as a prognostic marker in B-ALL and a potential therapeutic target to combat chemotherapy resistance in ALL.

Increased Expression of the ABCA1 and ABCA3 Transporter Genes is Associated with Cisplatin Resistance in Breast Cancer Cells

OBJECTIVE

Breast cancer (BC) is a highly malignant neoplasm with resistance to therapeutics that are related to genes associated with multidrug resistance. The excessive expression of ATP-binding cassette transporters (ABCs) genes, including ABCA1 and ABCA3, is a primary factor contributing to the increased effluent of cell-toxic drugs and subsequent treatment resistance. Therefore, the current work aimed to explore the role of ABCA1 and ABCA3 in chemoresistance activity against cisplatin in breast cancer cells.

METHODS

The current study compared the AMJ13 breast cancer cells derived from a woman Iraqi patient, which are hormone receptor-negative, with MCF-7 breast cancer cells, which are hormone receptor-positive.  Cytotoxic assay (CCK-8 assay) is used to measure the cell's viability and cytotoxic activity after it has been treated with cisplatin. Morphological Study using crystal violet stain to examine cytological changes was conducted. Quantitative RT-PCR is used to measure how much the ABCA1, and 3 genes mRNA are being expressed before and after treatment.

RESULTS

The CCK-8 assay found that IC50 values of cisplatin in AMJ13 and MCF-7 cells were 202.2 µg/ml and 90.23 µg/ml, respectively. The IC50 value of AMJ13 is 2-fold higher than in MCF-7 cells. The QPCR study revealed that breast cancer cell lines AMJ13 and MCF-7 subjected to cisplatin showed upregulated levels of ABCA1 and ABCA3 expression. Experiments with cytotoxicity assays demonstrate that higher expression of ABCA1 and ABCA3 in AMJ13 and MCF-7 breast cancer cell lines is linked to their resistance.  Conclusion: The findings of this study suggest that the ABCA1 and ABCA3 transporters play a significant role in the resistance to cisplatin and,.

The effects of Astragalus polysaccharides, tragacanthin, and bassorin on methotrexate-resistant acute lymphoblastic leukemia

Background and purpose

One strategy to overcome methotrexate (MTX) resistance in acute lymphoblastic leukemia is suppressing MDR1 expression. It has been proved Astragalus polysaccharides (APS) exert their anticancer effect by reversing drug resistance. Due to the structural similarity of tragacanthin and bassorin with APS, we aimed to investigate the effects of the aforementioned polysaccharides on the expression of the MDR1 gene in the MTX-treated CCRF-CEM cells.

Experimental approach

Cytotoxicity of APS, bassorin, and tragacanthin on CCRF-CEM, CCRF-CEM/MTX (cells treated with MTX at IC50), and CCRF-CEM/R cells (CCRF-CEM cells resistant to MTX) was evaluated by MTT assay. The effect of all three compounds on MDR1 expression was evaluated using RT-PCR.

Findings/Results

All the concentrations of tragacanthin, bassorin, and APS (except at 0.8-100 μg/mL in CCRF-CEM) decreased the viability of all the cells compared to the negative control group; and against the positive control (MTX-treated cells), only bassorin at 20-100 μg/mL in CCRF-CEM/R and tragacanthin at 50 and 100 μg/mL in CCRF-CEM/MTX and at 2-100 μg/mL in CCRF-CEM/R decreased cell viability. Tragacanthin diminished MDR1 expression in CCRF-CEM/MTX and CCRF-CEM/R cells, which MTX had already induced.

Conclusion and implication

According to the results of this study, tragacanthin was a potent cytotoxic agent against CCRF-CEM cells and enhanced the chemosensitivity of CCRF-CEM/MTX and CCRF-CEM/R cells to MTX by down-regulation of MDR1 gene expression. Therefore, it could be a promising compound against cancer. Other possible mechanisms of action of tragacanthin should be evaluated and further in vitro and in vivo investigations are required.

Drug-tolerant persister B-cell precursor acute lymphoblastic leukemia cells

Reduced responsiveness of precursor B-acute lymphoblastic leukemia (BCP-ALL) to chemotherapy can be inferred when leukemia cells persist after 28 days of initial treatment. Survival of these long-term persister (LTP) / minimal residual disease (MRD) cells is partly due to bone marrow stromal cells that protect them under conditions of chemotherapy stress. We used RNA-seq to analyse BCP-ALL cells that survived a long-term, 30-day vincristine chemotherapy treatment while in co-culture with bone marrow stromal cells. RNAs of as many as 10% of the protein-encoding genes were differentially expressed. There was substantial overlap with genes associated with MRD cell persistence reported in other studies. The top pathway regulated in the LTP cells was that involving p53, a master regulator of a spectrum of responses relevant to drug resistance and cytotoxic drug exposure including control of autophagy. We tested a select number of genes for contribution to BCP-ALL cell survival using Cas9/CRISPR in a 2-step selection, initially for overall effect on cell fitness, followed by 21 days of exposure to vincristine. Many genes involved in autophagy and lysosomal function were found to contribute to survival both at steady-state and during drug treatment. We also identified MYH9, NCSTN and KIAA2013 as specific genes contributing to fitness of BCP-ALL cells. CD44 was not essential for growth under steady state conditions but was needed for survival of vincristine treatment. Finally, although the drug transporter ABCC1/MRP1 is not overexpressed in BCP-ALL, a functional gene was needed for DTP cells to survive treatment with vincristine. This suggests that addition of possible ABCC1 inhibitors during induction therapy could provide benefit in eradication of minimal residual disease in patients treated with a chemotherapy regimen that includes vincristine.

What Is the Significance of Lysosomal-Mediated Resistance to Imatinib?

The lysosomal sequestration of hydrophobic weak-base anticancer drugs is one proposed mechanism for the reduced availability of these drugs at target sites, resulting in a marked decrease in cytotoxicity and consequent resistance. While this subject is receiving increasing emphasis, it is so far only in laboratory experiments. Imatinib is a targeted anticancer drug used to treat chronic myeloid leukaemia (CML), gastrointestinal stromal tumours (GISTs), and a number of other malignancies. Its physicochemical properties make it a typical hydrophobic weak-base drug that accumulates in the lysosomes of tumour cells. Further laboratory studies suggest that this might significantly reduce its antitumor efficacy. However, a detailed analysis of published laboratory studies shows that lysosomal accumulation cannot be considered a clearly proven mechanism of resistance to imatinib. Second, more than 20 years of clinical experience with imatinib has revealed a number of resistance mechanisms, none of which is related to its accumulation in lysosomes. This review focuses on the analysis of salient evidence and raises a fundamental question about the significance of lysosomal sequestration of weak-base drugs in general as a possible resistance mechanism both in clinical and laboratory settings.

Puzzling Out Iron Complications in Cancer Drug Resistance

Iron metabolism are frequently disrupted in cancer. Patients with cancer are prone to anemia and receive transfusions frequently; the condition which results in iron overload, contributing to serious therapeutic complications. Iron is introduced as a carcinogen that may increase tumor growth. However, investigations regarding its impact on response to chemotherapy, particularly the induction of drug resistance are still limited. Here, iron contribution to cell signaling and various molecular mechanisms underlying iron-mediated drug resistance are described. A dual role of this vital element in cancer treatment is also addressed. On one hand, the need to administer iron chelators to surmount iron overload and improve the sensitivity of tumor cells to chemotherapy is discussed. On the other hand, the necessary application of iron as a therapeutic option by iron-oxide nanoparticles or ferroptosis inducers is explained. Authors hope that this paper can help unravel the clinical complications related to iron in cancer therapy.

Negative value of CD10-/CD34- immunophenotype in pediatric leukemia and development of a related cell line model for investigating drug resistance

PURPOSE

Appropriate sub-classification of leukemia according to the immunophenotypic characteristics of the malignant cells may improve therapeutic strategies. The aim of this study was to investigate the prognostic value of CD10/CD34 surface markers in pediatric acute lymphoblastic leukemia (pALL).

PATIENTS AND METHODS

A retrospective cohort study was performed in 79 children with ALL. Possible correlation between leukemia prognosis and CD10 CD34 immunophenotype was assessed using Kaplan-Meier and Cox regression analyses. A CD10- CD34- pre-B-ALL cell line was generated from a patient with resistant ALL. RN95 was characterized using light microscopy, immunophenotyping, karyotyping, and Western blotting. Drug sensitivity and resistant genes' expression profile were assessed using MTT and RT-PCR assays.

RESULTS

Kaplan-Meier analysis showed negative correlation between CD10/CD34 double negativity and patients' 2- and 5-year disease-free survival (DFS). Multivariate analysis indicated that the absence of CD10 and CD34 expression in the ALL patients was an independent negative prognostic marker for 2- and 5-year DFS. A novel cell line model, RN95, was developed with similar immunophenotype from a primary relapsed sample. Cells showed p53 positive functionality and demonstrated partial sensitivity to Vincristine, but complete resistance to Cytarabine. Overexpression of ABCB1, ABCA2, and ABCA3 was detected.

CONCLUSION

In the current study, simultaneous absence of CD10 and CD34 cell surface markers was introduced as an unfavorable prognostic factor in pediatric B-ALL. Moreover, a special cell line was established to help delineation of novel therapeutics for B-ALL drug resistance.

Pharmacogenetics of induction therapy-related toxicities in childhood acute lymphoblastic leukemia patients treated with UKALL 2003 protocol

Chemotherapy related toxicities have been the major factor limiting the success of acute lymphoblastic leukemia (ALL) induction therapy. Several factors, including the pharmacogenetics of asparaginase and anthracyclines, could contribute to difference in treatment outcome in ALL. We investigated the significance of variations in genes involved in hepatic and cardiac toxicity in acute lymphoblastic leukemia (ALL). Genotyping of SOD2 (rs4880), PNPL3 (rs738409) and ABCC1 (rs4148350), CBR1 (rs9024) and ABCG2 (rs2231142) was performed by Tetra-ARMS PCR-based technique to evaluate the genotype-phenotype correlation. Our results showed only minor allele G of SOD2 rs4880 increase the risk of hepatic toxicity [OR 2.63 (1.42-4.84), P =  < 0.05] while minor alleles of other SNPs showed protective impact. However, the genetic contrast analysis showed a recessive form of SOD2 rs4880 [OR 7.82 (3.86-15.85), P =  < 0.05] and PNPLA3 I148M [OR 5.82 (3.43-9.87), P =  < 0.05] variants whereas dominant genotype of ABCC1 rs4148350 [OR 2.52 (1.55-4.10), P =  < 0.05] significantly predisposes hepatotoxicity. Furthermore, heterozygous form of ABCG2 rs2231142 [OR 5.25 (1.84-14.95), P =  < 0.05] and recessive genotype of 3'UTR variant CBR1 rs9024 [OR 2.31 (1.31-4.07), P =  < 0.05] were strongly associated with cardiotoxicity. The information obtained from these genetic variations could offer biomarkers for individualization of therapeutic intervention in ALL.

miR-324-3p and miR-508-5p expression levels could serve as potential diagnostic and multidrug-resistant biomarkers in childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is one of the most frequent hematological malignancies in children, representing approximately 25 % of all pediatric cancers. Despite striking advances in ALL treatments, a small population of patients does not still respond to chemotherapy, raising the number of deaths in children. ABC transporters are one of the major causes of multidrug resistance (MDR) in cancers and overexpression of ABCA3 is directly associated with increased chemo-resistance in pediatric ALL. Here, we aimed to identify the microRNAs (miRNAs) which may regulate the expression of ABCA3 in childhood ALL. Bone marrow samples from a total of 50 ALLs and 59 controls were collected and after in silico and literature search, miR-324-3p and miR-508-5p were nominated from a list of putative miRNAs targeting ABCA3. Our qPCR analysis showed a low expression profile of selected miRNAs in pediatric ALL patients compared with non-cancer controls. Furthermore, we found that both miR-324-3p and miR-508-5p were significantly differentially expressed between patients with positive and negative minimal residual disease (MRD + vs MRD-) after one year of chemotherapy while only miR-508-5p was underexpressed in relapsed ALL patients. Additionally, a negative correlation was identified between the expression of these two miRNAs and ABCA3, supporting the regulatory effect of them on drug resistance through interacting with ABCA3. Overall, we suggested miR-324-3p and miR-508-5p as potential diagnostic and drug-resistant biomarkers in pediatric ALL. Moreover, our findings presented miR-508-5p to behave as a promising relapsed indicator in childhood ALL which can be applied in the development of novel therapeutic strategies.

The REASON score: an epigenetic and clinicopathologic score to predict risk of poor survival in patients with early stage oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a capricious cancer with poor survival rates, even for early-stage patients. There is a pressing need to develop more precise risk assessment methods to appropriately tailor clinical treatment. Genome-wide association studies have not produced a viable biomarker. However, these studies are limited by using heterogeneous cohorts, not focusing on methylation although OSCC is a heavily epigenetically-regulated cancer, and not combining molecular data with clinicopathologic data for risk prediction. In this study we focused on early-stage (I/II) OSCC and created a risk score called the REASON score, which combines clinicopathologic characteristics with a 12-gene methylation signature, to predict the risk of 5-year mortality.

METHODS

We combined data from an internal cohort (n = 515) and The Cancer Genome Atlas (TCGA) cohort (n = 58). We collected clinicopathologic data from both cohorts to derive the non-molecular portion of the REASON score. We then analyzed the TCGA cohort DNA methylation data to derive the molecular portion of the risk score.

RESULTS

5-year disease specific survival was 63% for the internal cohort and 86% for the TCGA cohort. The clinicopathologic features with the highest predictive ability among the two the cohorts were age, race, sex, tobacco use, alcohol use, histologic grade, stage, perineural invasion (PNI), lymphovascular invasion (LVI), and margin status. This panel of 10 non-molecular features predicted 5-year mortality risk with a concordance (c)-index = 0.67. Our molecular panel consisted of a 12-gene methylation signature (i.e., HORMAD2, MYLK, GPR133, SOX8, TRPA1, ABCA2, HGFAC, MCPH1, WDR86, CACNA1H, RNF216, CCNJL), which had the most significant differential methylation between patients who survived vs. died by 5 years. All 12 genes have already been linked to survival in other cancers. Of the genes, only SOX8 was previously associated with OSCC; our study was the first to link the remaining 11 genes to OSCC survival. The combined molecular and non-molecular panel formed the REASON score, which predicted risk of death with a c-index = 0.915.

CONCLUSIONS

The REASON score is a promising biomarker to predict risk of mortality in early-stage OSCC patients. Validation of the REASON score in a larger independent cohort is warranted.

Selective dysregulation of ABC transporters in methotrexate-resistant leukemia T-cells can confer cross-resistance to cytarabine, vincristine and dexamethasone, but not doxorubicin

Pediatric acute lymphoblastic leukemia (pALL) includes 75 % of childhood leukemias, and methotrexate (MTX) is one of the most effective chemotherapy agents prescribed for pALL treatment. The aim of this study was to establish and characterize an MTX-resistant tumor cell model in order to study the mechanism contributing to drug sensitivity loss in pALL. Parental CCRF-CEM cells were treated with a gradual increasing concentration of MTX from 5 nM to 1.28 μM. The resistant subline was then characterized according to the cellular morphology, cellular growth curves and specific mRNA expression changes associated with drug resistance in ALL. Moreover, in vitro cytotoxicity assays were used to analyze cells relative responsiveness to a set of clinically used anti-ALL chemotherapy drugs. The morphological changes observed in the new R-CCRF-CEM/MVCD subline were associated with dysregulation of the EMT-related genes, Twist1 and CDH1. Cells demonstrated downregulation of ABCC1 and the overexpression of ABCA2, ABCA3, and ABCB1 membrane transporters. However, short treatment of the sensitive and parental cell line with MTX did not affect the expression profiles of the former ABC pumps. Moreover, R-CCRF-CEM/MVCD cells demonstrated cross-resistance to cytarabine (cytosine arabinoside, ara-C), vincristine, and dexamethasone, but not doxorubicin. The induced cross-resistance to specific chemotherapy drugs may possibly be attributed to selective dysregulation of the ABC transporters and EMT-related genes. These data may pave the way for the development of new cancer therapeutic strategies.

Effect of ABC transporter expression and mutational status on survival rates of cancer patients

ATP-binding cassette (ABC) transporters mediate multidrug resistance in cancer. In contrast to DNA single nucleotide polymorphisms in normal tissues, the role of mutations in tumors is unknown. Furthermore, the significance of their expression for prediction of chemoresistance and survival prognosis is still under debate. We investigated 18 tumors by RNA-sequencing. The mutation rate varied from 27,507 to 300885. In ABCB1, three hotspots with novel mutations were in transmembrane domains 3, 8, and 9. We also mined the cBioPortal database with 11,814 patients from 23 different tumor entities. We performed Kaplan-Meier survival analyses to investigate the effect of ABC transporter expression on survival rates of cancer patients. Novel mutations were also found in ABCA2, ABCA3, ABCB2, ABCB5, ABCC1-6, and ABCG2. Mining the cBioPortal database with 11,814 patients from 23 different tumor entities validated our results. Missense and in-frame mutations led to altered binding of anticancer drugs in molecular docking approaches. The ABCB1 nonsense mutation Q856* led to a truncated P-glycoprotein, which may sensitize tumors to anticancer drugs. The search for ABC transporter nonsense mutations represents a novel approach for precision medicine.. Low ABCB1 mRNA expression correlated with significantly longer survival in ovarian or kidney cancer and thymoma. In cancers of breast, kidney or lung, ABC transporter expression correlated with different tumor stages and human populations as further parameters to refine strategies for more individualized chemotherapy.

Targeting p53-MDM2 Interaction Using Small Molecule Inhibitors and the Challenges Needed to be Addressed

MDM2 protein is the core negative regulator of p53 that maintains the cellular levels of p53 at a low level in normal cells. Mutation of the TP53 gene accounts for 50% of all human cancers. In the remaining malignancies with wild-type TP53, p53 function is inhibited through other mechanisms. Recently, synthetic small molecule inhibitors have been developed which target a small hydrophobic pocket on MDM2 to which p53 normally binds. Given that MDM2-p53 antagonists have been undergoing clinical trials for different types of cancer, this review illustrates different aspects of these new cancer targeted therapeutic agents with the focus on the major advances in the field. It emphasizes on the p53 function, regulation of p53, targeting of the p53-MDM2 interaction for cancer therapy, and p53-dependent and -independent effects of inhibition of p53-MDM2 interaction. Then, representatives of small molecule MDM2-p53 binding antagonists are introduced with a focus on those entered into clinical trials. Furthermore, the review discusses the gene signatures in order to predict sensitivity to MDM2 antagonists, potential side effects and the reasons for the observed hematotoxicity, mechanisms of resistance to these drugs, their evaluation as monotherapy or in combination with conventional chemotherapy or with other targeted therapeutic agents. Finally, it highlights the certainly intriguing questions and challenges which would be addressed in future studies.

microRNAs targeting cellular cholesterol: implications for combating anticancer drug resistance

Over sixty percent of all mammalian protein-coding genes are estimated to be regulated by microRNAs (miRNAs), and unsurprisingly miRNA dysregulation has been linked with cancer. Aberrant miRNA expression in cancer cells has been linked with tumourigenesis and drug resistance. In the past decade, increasing number of studies have demonstrated that cholesterol accumulation fuels tumour growth and contributes to drug resistance, therefore, miRNAs controlling cholesterol metabolism and homeostasis are obvious hypothetical targets for investigating their role in cholesterol-mediated drug resistance in cancer. In this review, we have collated published evidences to consolidate this hypothesis and have scrutinized it by utilizing computational tools to explore the role of miRNAs in cholesterol-mediated drug resistance in breast cancer cells. We found that hsa-miR-128 and hsa-miR-223 regulate genes mediating lipid signalling and cholesterol metabolism, cancer drug resistance and breast cancer genes. The analysis demonstrates that targeting these miRNAs in cancer cells presents an opportunity for developing new strategies to combat anticancer drug resistance.

Genetics of blood malignancies among Iranian population: an overview

BACKGROUND

Blood malignancies are among the leading causes of cancer related deaths in the world. Different environmental and genetic risk factors are involved in progression of blood malignancies. It has been shown that the lifestyle changes have affected the epidemiological patterns of these malignancies. Hematologic cancers are the 5th common cancer among Iranian population. It has been observed that there is a rising trend of blood malignancies incidences during the recent decades. Therefore, it is required to design novel diagnostic methods for the early detection of such malignancies in this population.

MAIN BODY

In present review we have summarized all of the significant genes which have been reported among Iranian patients with blood malignancies. The reported genes were categorized based on their cell and molecular functions to clarify the molecular biology and genetics of blood malignancies among Iranian patients.

CONCLUSION

It was observed that the epigenetic and immune response factors were the most frequent molecular processes associated with progression of blood malignancies among Iranian population. This review paves the way of introducing a population based panel of genetic markers for the early detection of blood malignancies in this population.

Iron protects childhood acute lymphoblastic leukemia cells from methotrexate cytotoxicity

Drug resistance is a fundamental clinical concern in pediatric acute lymphoblastic leukemia (pALL), and methotrexate (MTX) is an essential chemotherapy drug administered for the treatment. In the current study, the effect of iron in response to methotrexate and its underlying mechanisms were investigated in pALL cells. CCRF-CEM and Nalm6 cell lines were selected as T and B-ALL subtypes. Cells were pretreated with ferric ammonium citrate, exposed to the IC50 concentration of MTX and cell viability was assessed using MTT, colony formation, and flow cytometry assays. Iron-loaded cells were strongly resistant to MTX cytotoxicity. The inhibitory effect of N-acetyl cysteine to reverse the acquired MTX resistance was greater than that of the iron chelator, deferasirox, highlighting the importance of iron-mediated ROS in MTX resistance. Subsequently, the upregulation of BCL2, SOD2, NRF2, and MRP1 was confirmed using quantitative RT-PCR. Moreover, a positive correlation was demonstrated between the MRP1 expression levels and bone marrow iron storage in pALL patients. Further supporting our findings were the hematoxylin and eosin-stained histological sections showing that iron-treated nude mice xenografts demonstrated significantly more liver damage than those unexposed to iron. Overall, iron is introduced as a player with a novel role contributing to methotrexate resistance in pALL. Our findings suggest that the patients' bone marrow iron stores are necessary to be assessed during the chemotherapy, and transfusions should be carefully administrated.

Sal-Like Protein 4 Transcription Factor: A Significant Diagnostic Biomarker Involved in Childhood ALL Resistance and Relapse

Purpose

Sal‐like protein 4 transcription factor (SALL4) is a stem cell transcription factor that plays an essential role in the maintenance and self-renewal of embryonic and hematopoietic stem cells, functioning as an oncogene in several cancers. However, the role of SALL4 in the biological behavior of childhood acute lymphoblastic leukemia and its relationship with multidrug resistance and relapse has remained largely unknown.

Patients and Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to characterize the expression pattern of SALL4 in the bone marrow samples of 43 patients with Philadelphia negative ALL and 18 children in the non-cancer control group. The presence of minimal residual disease was measured a year after the initial therapy using SSCP (single-strand conformation polymorphism). In addition, the correlation between the expression of SALL4 and ABCA3 in relapsed patients was analyzed statistically.

Results

Results showed an overexpression of SALL4 in de novo patients compared with the control group (P=0.0001, AUC= 0.93), indicating the importance of this gene in the induction of leukemia. A significant increase in the ABCA3 expression levels was revealed in the relapsed patients, in comparison with the drug-sensitive group (P = 0.0005). The leukemogenetic effect of SALL4 can be related to the effect of this gene on the maintenance of pluripotency in cancer stem cells. Results also suggest that the expression of SALL4 can be considered as a diagnostic marker for pediatric ALL. Moreover, SALL4 expression levels in the minimal residual disease positive (mrd+) ALL group was significantly higher than those in the mrd− group (p=0.0001, AUC= 0.92).

Conclusion

These data demonstrate the prognostic impact of SALL4 in childhood ALL. Our findings also indicated a direct correlation between the mRNA expression levels of SALL4 and ABCA3 transporter in the relapsed group of ALL patients (r=0.7). These results describe a possible mechanism by which SALL4 may lead to the development of multidrug resistance.

Drug Resistance Biomarkers and Their Clinical Applications in Childhood Acute Lymphoblastic Leukemia

Biomarkers are biological molecules found in body fluids or tissues, which can be considered as indications of a normal or abnormal process, or of a condition or disease. There are various types of biomarkers based on their application and molecular alterations. Treatment-sensitivity or drug resistance biomarkers include prognostic and predictive molecules with utmost importance in selecting appropriate treatment protocols and improving survival rates. Acute lymphoblastic leukemia (ALL) is the most prevalent hematological malignancy diagnosed in children with nearly 80% cure rate. Despite the favorable survival rates of childhood ALL (chALL), resistance to chemotherapeutic agents and, as a consequence, a dismal prognosis develops in a significant number of patients. Therefore, there are urgent needs to have robust, sensitive, and disease-specific molecular prognostic and predictive biomarkers, which could allow better risk classification and then better clinical results. In this article, we review the currently known drug resistance biomarkers, including somatic or germ line nucleic acids, epigenetic alterations, protein expressions and metabolic variations. Moreover, biomarkers with potential clinical applications are discussed.

The Role of MicroRNA in Paediatric Acute Lymphoblastic Leukaemia: Challenges for Diagnosis and Therapy

Acute lymphoblastic leukaemia (ALL) is the most common cancer of childhood. Although the overall survival of children with ALL is now more than 90%, leukaemia remains one of the leading causes of death from disease. In developed countries, the overall survival of patients with ALL has increased to more than 80%; however, those children cured from ALL still show a significant risk of short- and long-term complications as a consequence of their treatment. Accordingly, there is a need not only to develop new methods of diagnosis and prognosis but also to provide patients with less toxic therapies. MicroRNAs (miRNAs) are small ribonucleic acids (RNA), usually without coding potential, that regulate gene expression by directing their target messenger RNAs (mRNAs) for degradation or translational suppression. In paediatric ALL, several miRNAs have been observed to be overexpressed or underexpressed in patient cohorts compared to healthy individuals, while numerous studies have identified specific miRNAs that can be used as biomarkers to diagnose ALL, classify it into subgroups, and predict prognosis. Likewise, a variety of miRNAs identify as candidate targets for treatment, although there are numerous obstacles to overcome before their clinical use in patients. Here, we summarise the roles played by different miRNAs in childhood leukaemia, focussing primarily on their use as diagnostic tools and potential therapeutic targets, as well as a role in predicting treatment outcome. Finally, we discuss the potential roles of miRNA in immunotherapy and the novel contributions made by gut miRNAs to regulation of the host microbiome.

The ABC subfamily A transporters: Multifaceted players with incipient potentialities in cancer

Overexpression of ATP-binding cassette (ABC) transporters is a cause of drug resistance in a plethora of tumors. More recent evidence indicates additional contribution of these transporters to other processes, such as tumor cell dissemination and metastasis, thereby extending their possible roles in tumor progression. While the role of some ABC transporters, such as ABCB1, ABCC1 and ABCG2, in multidrug resistance is well documented, the mechanisms by which ABC transporters affect the proliferation, differentiation, migration and invasion of cancer cells are still poorly defined and are frequently controversial. This review, summarizes recent advances that highlight the role of subfamily A members in cancer. Emerging evidence highlights the potential value of ABCA members as biomarkers of risk and response in different tumors, but information is disperse and very little is known about their possible mechanisms of action. The only clear evidence is that ABCA members are involved in lipid metabolism and homeostasis. In particular, the relationship between ABCA1 and cholesterol is becoming evident in different fields of biology, including cancer. In parallel, emerging findings indicate that cholesterol, the main component of cell membranes, can influence many physiological and pathological processes, including cell migration, cancer progression and metastasis. This review aims to link the dispersed knowledge regarding the relationship of ABCA members with lipid metabolism and cancer in an effort to stimulate and guide readers to areas that the writers consider to have significant impact and relevant potentialities.

The Hedgehog signal transducer Smoothened and microRNA-326: pathogenesis and regulation of drug resistance in pediatric B-cell acute lymphoblastic leukemia

Purpose

Multidrug resistance (MDR) and the subsequent disease relapse are the major causes of childhood acute lymphoblastic leukemia (ALL) related death. The Hedgehog (Hh) signaling pathway can contribute to cancer MDR. In the current study, Smoothened (Smo) was selected as the experimental target due to its importance in the Hh pathway in order to evaluate its probable role in pediatric B-ALL drug resistance.

Patients and methods

The study included 27 pediatric B-ALL and 16 control bone marrow samples. Quantitative RT-PCR was used to investigate the expression levels of Smo and miR-326 as the key players of the Hh pathway. Western blot analysis was performed. The presence of minimal residual disease was studied using PCR-SSCP. The association between Smo expression and drug resistance was analyzed statistically.

Results

Results showed a significant increase in the Smo expression levels in drug-resistant patients in comparison with drug-sensitive children with B-ALL (P=0.0128, AUC=0.82). A considerable negative association between miR-326 and Smo expression levels was identified (r=-0.624, P=0.002). A binomial test confirmed the regulatory role of miR-326 on the translational repression of Smo (P=0.031). Statistics showed no association between Smo and ABCA2 expression levels. However, a significant positive correlation was observed between the Smo and ABCA3 transcripts in the resistant ALL children (r=0.607, P=0.016).

Conclusion

Data revealed the possible oncogenic impact of Smo on leukemogenesis and drug resistance in pediatric B-ALL. Upregulation of Smo was introduced, for the first time, as a prognostic factor for drug resistance in childhood B-ALL. To the best of our knowledge, this is the first study that shows a positive correlation between Smo and ABCA3 expression levels in pediatric B-ALL, explaining a possible mechanism for the development of drug resistance in this cancer. Moreover, the current project revealed a negative modulatory effect of miR-326 on the expression levels of Smo.

Ginger extract has anti-leukemia and anti-drug resistant effects on malignant cells

PURPOSE

Based on the poor prognosis of drug resistance in pediatric acute lymphoblastic leukemia (ALL) and adverse effects of chemotherapy, this study was aimed to evaluate the effect of several herbal extracts on leukemic cells.

METHODS

Two subtypes of T- and B-ALL cell lines, followed by ALL primary cells were treated with cinnamon, ginger, and green tea extracts, alone or in combination with methotrexate (MTX). Possible apoptosis was investigated using Annexin-V/PI double staining. Real-time PCR was applied to evaluate the expression levels of related ABC transporters upon combination therapy.

RESULTS

The IC50s for cinnamon, ginger and green tea extracts on ALL cell lines were 300 μg/ml, 167 μg/ml and 70 μg/ml, respectively. Surprisingly, the methotrexate (MTX)-resistant sub-line showed more sensitivity to ginger. Combined treatment with ginger and MTX showed synergistic effects on CCRF-CEM, Nalm-6 and ALL primary cells. It was shown that ginger does not impair the high expression levels of ABCA2 or ABCA3 transporter genes in the ALL malignant cells, suggesting other molecular pathways involved in its anticancer potential.

CONCLUSION

To the best of our knowledge, this is the first study that reveals the antileukemic effect of ginger extract on both, pediatric ALL cell lines and primary cells.

Dysregulation of miR-335-3p, targeted by NEAT1 and MALAT1 long non-coding RNAs, is associated with poor prognosis in childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most prevalent cancer among children, and multidrug efflux mediated by overexpression of ABC transporters is the major impediment to successful chemotherapy in this malignancy. The goal of this study is to identify the non-coding RNAs (ncRNAs) which may affect the expression levels of ABCA3; the previously identified prognostic biomarker for multidrug resistance (MDR) in childhood ALL (cALL). Bone marrow samples from 64 cALLs, including 46 de novo and 18 relapsed patients, in addition to 30 non-cancer controls were collected, and ncRNAs were nominated using in silico studies. Quantitative RT-PCR showed low expression profiles of miR-335-3p in cALLs compared with the control group (P = 0.018). Inverse correlation was determined between the miR-335-3p and ABCA3 mRNA expression profiles in cALL patients (r = 0.5019, P = 0.002). Moreover, it was shown that the expression levels of miR-335-3p was downregulated in the drug-resistant samples (MDR group) compared with the drug-sensitive patients (mrd- group), (P = 0.0005, AUC = 0.801). On the other hand, negative correlations were identified between the expression levels of miR-335-3p and the selected LncRNAs, NEAT1 and MALAT1, in the MDR group compared with the mrd- patients (P = 0.009), suggesting a sponge effect for these LncRNAs. The current study showed a potential regulatory role for miR-335-3p in ABCA3 expression targeted by NEAT1 and MALAT1 long non-coding RNAs. This negative impact may possibly contribute to the development of chemoresistance in childhood ALL, and provide an exceptional insight to new therapeutic approaches.

ABC Family Transporters

The transport of specific molecules across lipid membranes is an essential function of all living organisms. The processes are usually mediated by specific transporters. One of the largest transporter families is the ATP-binding cassette (ABC) family. More than 40 ABC transporters have been identified in human, which are divided into 7 subfamilies (ABCA to ABCG) based on their gene structure, amino acid sequence, domain organization, and phylogenetic analysis. Of them, at least 11 ABC transporters including P-glycoprotein (P-GP/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2) are involved in multidrug resistance (MDR) development. These ABC transporters are expressed in various tissues such as the liver, intestine, kidney, and brain, playing important roles in absorption, distribution, and excretion of drugs. Some ABC transporters are also involved in diverse cellular processes such as maintenance of osmotic homeostasis, antigen processing, cell division, immunity, cholesterol, and lipid trafficking. Several human diseases such as cystic fibrosis, sitosterolemia, Tangier disease, intrahepatic cholestasis, and retinal degeneration are associated with mutations in corresponding transporters. This chapter will describe function and expression of several ABC transporters (such as P-GP, BCRP, and MRPs), their substrates and inhibitors, as well as their clinical significance.

ABC transporters as cancer drivers: Potential functions in cancer development

BACKGROUND

ABC transporters have attracted considerable attention for their function as drug transporters in a broad range of tumours and are therefore considered as major players in cancer chemoresistance. However, less attention has been focused on their potential role as active players in cancer development and progression.

SCOPE OF REVIEW

This review presents the evidence suggesting that ABC transporters might have a more active role in cancer other than the well known involvement in multidrug resistance and discusses the potential strategies to target each ABC transporter for a specific tumour setting.

MAJOR CONCLUSIONS

Emerging evidence suggests that ABC transporters are able to transport bioactive molecules capable of playing key roles in tumour development. Characterization of the effects of these transporters in specific cancer settings opens the possibility for the development of personalized treatments.

GENERAL SIGNIFICANCE

A more targeted approach of ABC transporters should be implemented that considers which specific transporter is playing a major role in a particular tumour setting in order to achieve a more successful outcome for ABC transporters inhibitors in cancer therapy.

Neuroblastoma Origin and Therapeutic Targets for Immunotherapy

Neuroblastoma is a pediatric solid cancer of heterogeneous clinical behavior. The unique features of this type of cancer frequently hamper the process of determining clinical presentation and predicting therapy effectiveness. The tumor can spontaneously regress without treatment or actively develop and give rise to metastases despite aggressive multimodal therapy. In recent years, immunotherapy has become one of the most promising approaches to the treatment of neuroblastoma. Still, only one drug for targeted immunotherapy of neuroblastoma, chimeric monoclonal GD2-specific antibodies, is used in the clinic today, and its application has significant limitations. In this regard, the development of effective and safe GD2-targeted immunotherapies and analysis of other potential molecular targets for the treatment of neuroblastoma represents an important and topical task. The review summarizes biological characteristics of the origin and development of neuroblastoma and outlines molecular markers of neuroblastoma and modern immunotherapy approaches directed towards these markers.

MicroRNA-326 and microRNA-200c: Two novel biomarkers for diagnosis and prognosis of pediatric acute lymphoblastic leukemia

Multidrug resistance (MDR) is considered as the major obstacle for treating pediatric acute lymphoblastic leukemia (ALL). MicroRNAs (miRNAs) are small non coding RNAs which may potentially regulate response to chemotherapy. In this study, total RNA was isolated from bone marrow samples of 46 children with de novo ALL and 16 controls. Quantitative reverse transcriptase polymerase chain reaction was used to investigate the expression profile of the predicted miRNAs; miR-326 and miR-200c, and their predicted targets ABCA2, and ABCA3 transporters. The presence of minimal residual disease was studied using PCR-SSCP (single-strand conformation polymorphism) 1 year after treatment. The association between the miRNA expression and drug resistance was analyzed statistically. Results showed a significant down-regulation of both miR-326 and miR-200c expressions in ALL patients compared with non-cancer controls (P = 0.0002, AUC = 0.813 and P = 0.035, AUC = 0.79, respectively). A considerable negative association between miR-326 expression and MDR was identified which could raise the risk of chemoresistance by 4.8- fold. The expression profiles of miR-326 and ABCA2 transporter were inversely correlated. Data revealed, a novel diagnostic role for miR-326 and miR-200c as potential biomarkers of pediatric ALL. Down-regulation of miR-326 was introduced, for the first time, as a prognostic factor for drug resistance in childhood ALL. To the best of our knowledge, this is the first time that ABCA2 transporter is proposed as a target gene for miR-326, through which it can exert its impact on drug resistance. These data may provide novel approaches to new therapeutics and diagnostics.

Heterogeneity in mechanisms of emergent resistance in pediatric T-cell acute lymphoblastic leukemia

Relapse in pediatric T-cell acute lymphoblastic leukemia (T-ALL) remains a significant clinical problem and is thought to be associated with clonal selection during treatment. In this study we used an established pre-clinical model of induction therapy to increase our understanding of the effect of engraftment and chemotherapy on clonal selection and acquisition of drug resistance in vivo. Immune-deficient mice were engrafted with patient diagnostic specimens and exposed to a repeated combination therapy consisting of vincristine, dexamethasone, L-asparaginase and daunorubicin. Any re-emergence of disease following therapy was shown to be associated with resistance to dexamethasone, no resistance was observed to the other three drugs. Immunoglobulin/T-cell receptor gene rearrangements closely matched those in respective diagnosis and relapse patient specimens, highlighting that these clonal markers do not fully reflect the biological changes associated with drug resistance. Gene expression profiling revealed the significant underlying heterogeneity of dexamethasone-resistant xenografts. Alterations were observed in a large number of biological pathways, yet no dominant signature was common to all lines. These findings indicate that the biological changes associated with T-ALL relapse and resistance are stochastic and highly individual, and underline the importance of using sophisticated molecular techniques or single cell analyses in developing personalized approaches to therapy.

The translational expression of ABCA2 and ABCA3 is a strong prognostic biomarker for multidrug resistance in pediatric acute lymphoblastic leukemia

Purpose

The aim of this work was to study the correlation between the expressions of the ABCA2 and ABCA3 genes at the mRNA and protein levels in children with acute lymphoblastic leukemia (ALL) and the effects of this association on multidrug resistance (MDR).

Materials and methods

Sixty-nine children with de novo ALL and 25 controls were enrolled in the study. Mononuclear cells were isolated from the bone marrow. The mRNA levels of ABCA2 and ABCA3 were measured by real-time polymerase chain reaction (PCR). Samples with high mRNA levels were assessed for respective protein levels by Western blotting. Following the first year of treatment, persistent monoclonality of T-cell gamma receptors or immunoglobulin H (IgH) gene rearrangement was assessed and considered as the MDR. The tertiary structure of ABCA2 was predicted using Phyre2 and I-TASSER web systems and compared to that of ABCA3, which has been previously reported. Molecular docking was performed using DOCK 6.7.

Results

Real-time quantitative PCR (qRT-PCR) showed high levels of ABCA2 and ABCA3 mRNAs in 13 and 17 samples, respectively. Among them, five and eight individuals demonstrated high levels of ABCA2 and ABCA3, respectively. Response to chemotherapy was significantly decreased (P=0.001) when the mRNA and protein of both genes were overexpressed compared to individuals with high transcriptional levels of either ABCA2 or ABCA3 alone. Close similarity between ABCA2 and ABCA3 structures was revealed by protein tertiary structure prediction, whereas molecular docking analysis suggested similar binding of chemotherapy drugs and therefore a potentially similar role in determining the MDR.

Conclusion

Our findings suggested, for the first time, that quantification of the protein level of ABCA2 and ABCA3 transporters had a prognostic impact on pediatric ALL MDR. Furthermore, the tertiary structure of ABCA2 was predicted for the first time, and docking analysis revealed a possible compensatory effect between ABCA2 and ABCA3 transporters, which may contribute to the efflux of cytotoxic drugs and, ultimately, to chemoresistance.

Multinucleated polyploidy drives resistance to Docetaxel chemotherapy in prostate cancer

BACKGROUND

Docetaxel is the only FDA-approved first-line treatment for castration-resistant prostate cancer (CRPC) patients. Docetaxel treatment inevitably leads to tumour recurrence after an initial therapeutic response with generation of multinucleated polyploid (MP) cells. Here we investigated role of MP cells in clinical relapse of CRPC.

METHODS

Prostate cancer (PC-3) cells were treated with docetaxel (5 nM) for 3 days followed by a washout and samples were collected at close intervals over 35 days post drug washout. The tumorigenic potential of the giant MP cells was studied by implanting MP cells subcutaneously as tumour xenografts in nude mice.

RESULTS

Docetaxel-induced polyploid cells undergo mitotic slippage and eventually spawn mononucleated cells via asymmetric cell division or neosis. Both MP and cells derived from polyploid cells had increased survival signals, were positive for CD44 and were resistant to docetaxel chemotherapy. Although MP cells were tumorigenic in nude mice, these cells took a significantly longer time to form tumours compared with parent PC-3 cells.

CONCLUSIONS

Generation of MP cells upon docetaxel therapy is an adaptive response of apoptosis-reluctant cells. These giant cells ultimately contribute to the generation of mononucleated aneuploid cells via neosis and may have a fundamental role precipitating clinical relapse and chemoresistance in CRPC.

Clinical significance of the ABCB1 and ABCG2 gene expression levels in acute lymphoblastic leukemia

OBJECTIVES

Acute lymphoblastic leukemia (ALL) is a clonal disease that accounts for 20% of acute leukemias in adults. A high percentage of adult patients (ranging from 70 to 80%) reach complete remission; however, the 5-year survival rate is only 20-40%. One of the main obstacles to treatment success is the drug resistance of leukemic cells. Therefore, our research group analyzed the ABCB1 and ABCG2 gene expression levels in 61 patients diagnosed with ALL and assessed whether the levels affected the clinical parameters and 40-month survival rate.

METHODS

The ABCB1 and ABCG2 gene expression levels were analyzed using real-time polymerase chain reaction in 61 patients diagnosed with ALL and 99 healthy donors as controls. The association between ABCB1 and ABCG2 gene expression levels and clinical variables was determined using the Chi-square test and Fisher's exact test. Overall survival (OS) was determined using the Kaplan-Meier method.

RESULTS

The results showed high ABCB1 and ABCG2 gene levels, which were 4.5 and 2.3 times the levels of healthy donors, respectively. A total of 52% of the study patients expressed high ABCB1 levels and were significantly associated with the high-risk patient group and a decreased 40-month survival rate of 78%. Only 49% of the patients expressed high ABCG2 gene levels. No association was found between the clinical parameters and the ABCG2 gene expression levels.

CONCLUSIONS

Early detection of ABCB1 gene expression levels could be important for the diagnosis and monitoring of ALL patients.

Inorganic Nanocarriers Overcoming Multidrug Resistance for Cancer Theranostics

Cancer multidrug resistance (MDR) could lead to therapeutic failure of chemotherapy and radiotherapy, and has become one of the main obstacles to successful cancer treatment. Some advanced drug delivery platforms, such as inorganic nanocarriers, demonstrate a high potential for cancer theranostic to overcome the cancer-specific limitation of conventional low-molecular-weight anticancer agents and imaging probes. Specifically, it could achieve synergetic therapeutic effects, demonstrating stronger killing effects to MDR cancer cells by combining the inorganic nanocarriers with other treatment manners, such as RNA interference and thermal therapy. Moreover, the inorganic nanocarriers could provide imaging functions to help monitor treatment responses, e.g., drug resistance and therapeutic effects, as well as analyze the mechanism of MDR by molecular imaging modalities. In this review, the mechanisms involved in cancer MDR and recent advances of applying inorganic nanocarriers for MDR cancer imaging and therapy are summarized. The inorganic nanocarriers may circumvent cancer MDR for effective therapy and provide a way to track the therapeutic processes for real-time molecular imaging, demonstrating high performance in studying the interaction of nanocarriers and MDR cancer cells/tissues in laboratory study and further shedding light on elaborate design of nanocarriers that could overcome MDR for clinical translation.

Identification of mutations, gene expression changes and fusion transcripts by whole transcriptome RNAseq in docetaxel resistant prostate cancer cells

Docetaxel has been the standard first-line therapy in metastatic castration resistant prostate cancer. The survival benefit is, however, limited by either primary or acquired resistance. In this study, Du145 prostate cancer cells were converted to docetaxel-resistant cells Du145-R and Du145-RB by in vitro culturing. Next generation RNAseq was employed to analyze these cell lines. Forty-two genes were identified to have acquired mutations after the resistance development, of which thirty-four were found to have mutations in published sequencing studies using prostate cancer samples from patients. Fourteen novel and 2 previously known fusion genes were inferred from the RNA-seq data, and 13 of these were validated by RT-PCR and/or re-sequencing. Four in-frame fusion transcripts could be transcribed into fusion proteins in stably transfected HEK293 cells, including MYH9-EIF3D and LDLR-RPL31P11, which were specific identified or up-regulated in the docetaxel resistant DU145 cells. A panel of 615 gene transcripts was identified to have significantly changed expression profile in the docetaxel resistant cells. These transcriptional changes have potential for further study as predictive biomarkers and as targets of docetaxel treatment.

Overexpression of SORCIN is a Prognostic Biomarker for Multidrug-Resistant Pediatric Acute Lymphoblastic Leukemia and Correlates with Upregulated MDR1/P-gp

BACKGROUND

Multidrug resistance is one of the major causes of treatment failure in pediatric acute lymphoblastic leukemia (ALL), and SORCIN is an intracellular calcium modulator protein. The current study was designed to investigate the in vitro and in vivo relationships between the expression levels of SORCIN: in tumor cell lines and children with ALL; its possible correlation with MDR1/P-glycoprotein (P-gp), a multidrug resistance-related gene; and response to therapy.

MATERIALS AND METHODS

Childhood T-lymphoblastic leukemia (CCRF-CEM) cell lines resistant to methotrexate (MTX) were developed. Patient studies were performed by including 30 children with ALL at diagnosis, 3 children with bone marrow relapse, and 15 children with no symptoms of cancer. The mRNA expression profiles of SORCIN and MDR1/P-gp was assessed using quantitative polymerase chain reaction (qPCR). Minimal residual disease (MRD) was measured in the patient population, a year following the initial therapy using qPCR.

RESULTS

Cell line data analyses showed a positive correlation between SORCIN mRNA levels and resistance to MTX. The difference between patient and control groups for SORCIN expression levels was not significant. However, patients with a negative response to therapy showed an increase in SORCIN mRNA levels (up to 6.8-fold) compared with those with negative MRD. In addition, the results demonstrated a significant positive correlation between SORCIN and MDR1/P-gp gene expression levels.

CONCLUSION

The current study introduces, for the first time, a possible prognostic value of SORCIN in childhood ALL, which may be correlated with MDR1/P-gp gene expression in these patients.

Overexpression of lncRNA NEAT1 mitigates multidrug resistance by inhibiting ABCG2 in leukemia

Leukemia is a heterogeneous clonal disorder in which early hematopoietic cells fail to differentiate and do not undergo programmed cell death or apoptosis. Less than one-third of adult patients with leukemia are managed using current therapies due to the emergence of multidrug resistance (MDR), emphasizing the need for newer and more robust approaches. Recent reports have suggested that long non-coding RNAs (lncRNAs) contribute to selective gene expression and, hence, could be manipulated effectively to halt the progression of cancer. However, little is known regarding the role of lncRNA in leukemia. Nuclear paraspeckle assembly transcript 1 (NEAT1) is a nuclear-restricted lncRNA involved in the pathogenesis of certain types of cancer. Deregulated expression of NEAT1 has been reported in a number of human malignancies, including leukemia and other solid tumors. The present study aimed to characterize the role of NEAT1 in the regulation of MDR in leukemia. Using reverse transcription-quantitative polymerase chain reaction, it was demonstrated that NEAT1 messenger RNA (mRNA) expression levels were significantly downregulated in leukemia patient samples compared with those from healthy donors. Furthermore, NEAT1 mRNA expression was repressed in a number of leukemia cell lines, including K562, THP-1, HL-60 and Jurkat cells, compared with peripheral white blood control cells, consistent with the expression observed in patients with leukemia. In addition, the transfection of a NEAT1 overexpression plasmid into K562 and THP-1 leukemia cell lines alleviated MDR induced by cytotoxic agents, such as Alisertib and Bortezomib, through inhibition of ATP-binding cassette G2. Although more robust studies are warranted, the current findings provide the basis for the use of NEAT1 as a novel promising target in the treatment of leukemia.

Modulation of P-glycoprotein activity by novel synthetic curcumin derivatives in sensitive and multidrug-resistant T-cell acute lymphoblastic leukemia cell lines

BACKGROUND

Multidrug resistance (MDR) and drug transporter P-glycoprotein (P-gp) represent major obstacles in cancer chemotherapy. We investigated 19 synthetic curcumin derivatives in drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and their multidrug-resistant P-gp-overexpressing subline, CEM/ADR5000.

MATERIAL AND METHODS

Cytotoxicity was tested by resazurin assays. Doxorubicin uptake was assessed by flow cytometry. Binding modes of compounds to P-gp were analyzed by molecular docking. Chemical features responsible for bioactivity were studied by quantitative structure activity relationship (QSAR) analyses. A 7-descriptor QSAR model was correlated with doxorubicin uptake values, IC50 values and binding energies.

RESULTS

The compounds displayed IC50 values between 0.7±0.03 and 20.2±0.25μM. CEM/ADR5000 cells exhibited cross-resistance to 10 compounds, collateral sensitivity to three compounds and regular sensitivity to the remaining six curcumins. Molecular docking studies at the intra-channel transmembrane domain of human P-gp resulted in lowest binding energies ranging from -9.00±0.10 to -6.20±0.02kcal/mol and pKi values from 0.24±0.04 to 29.17±0.88μM. At the ATP-binding site of P-gp, lowest binding energies ranged from -9.78±0.17 to -6.79±0.01kcal/mol and pKi values from 0.07±0.02 to 0.03±0.03μM. CEM/ADR5000 cells accumulated approximately 4-fold less doxorubicin than CCRF-CEM cells. The control P-gp inhibitor, verapamil, partially increased doxorubicin uptake in CEM/ADR5000 cells. Six curcumins increased doxorubicin uptake in resistant cells or even exceeded uptake levels compared to sensitive one. QSAR yielded good activity prediction (R=0.797 and R=0.794 for training and test sets).

CONCLUSION

Selected derivatives may serve to guide future design of novel P-gp inhibitors and collateral sensitive drugs to combat MDR.

Apoptosis pathway signature for prediction of treatment response and clinical outcome in childhood high risk B-Precursor acute lymphoblastic leukemia

The most common cancer in children is acute lymphoblastic leukemia (ALL) and it had high cure rate, especially for B-precursor ALL. However, relapse due to drug resistance and overdose treatment reach the limitations in patient managements. In this study, integration of gene expression microarray data, logistic regression, analysis of microarray (SAM) method, and gene set analysis were performed to discover treatment response associated pathway-based signatures in the original cohort. Results showed that 3772 probes were significantly associated with treatment response. After pathway analysis, only apoptosis pathway had significant association with treatment response. Apoptosis pathway signature (APS) derived from 15 significantly expressed genes had 88% accuracy for treatment response prediction. The APS was further validated in two independent cohorts. Results also showed that APS was significantly associated with induction failure time (adjusted hazard ratio [HR] = 1.60, 95% confidence interval [CI] = [1.13, 2.27]) in the first cohort and significantly associated with event-free survival (adjusted HR = 1.56, 95% CI = [1.13, 2.16]) or overall survival in the second cohort (adjusted HR = 1.74, 95% CI = [1.24, 2.45]). APS not only can predict clinical outcome, but also provide molecular guidance of patient management.

mRNA overexpression of BAALC: A novel prognostic factor for pediatric acute lymphoblastic leukemia

BAALC is a novel molecular marker in leukemia that is highly expressed in patients with acute leukemia. Increased expression levels of BAALC are known as poor prognostic factors in adult acute myeloid and lymphoid leukemia. The purpose of the present study was to evaluate the prognostic significance of the BAALC gene expression levels in pediatric acute lymphoblastic leukemia (ALL) and its association with MDR1. Using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), the mRNA expression levels of BAALC and MRD1 were measured in bone marrow samples of 28 new diagnosed childhood ALL patients and 13 children without cancer. Minimal residual disease (MRD) was measured one year after the initiation of the chemotherapy using the RT-qPCR method. The high level expression of BAALC had a significant association with the pre-B-ALL subtype, leukocytosis and positive MRD after one year of treatment in leukemic patients. In addition, a positive correlation between BAALC and MDR1 mRNA expression was shown in this group. In conclusion, to the best of our knowledge, the increase of BAALC expression as a poor prognostic factor for childhood ALL is shown for the first time. Additionally, the correlation between BAALC and MDR1 in mRNA expression levels can aid for an improved understanding of the mechanism through which BAALC may function in ALL and multidrug resistance.

Piperlongumine reverses doxorubicin resistance through the PI3K/Akt signaling pathway in K562/A02 human leukemia cells

Drug resistance is an important obstacle to human leukemia therapeutics. Piperlongumine has previously demonstrated the ability to suppress certain human tumor processes; however, the ability of piperlongumine to reverse the drug resistance of human leukemia and its mechanism of action have not yet been clearly elucidated. In this study, the doxorubicin resistance reversal effect of piperlongumine on K562/A02 human leukemia cells and the underlying mechanism were investigated. The results indicated that piperlongumine promoted doxorubicin sensitivity, apoptosis, the intracellular accumulation of rhodamine-123, the activities of caspase-3 and -8, and the expression of reactive oxygen species, p53, p27 and p-PTEN. Furthermore, it suppressed the expression of P-glycoprotein, MDR1, MRP1, survivin and p-Akt, and the transcriptional activities of NF-κB and twist, and arrested the cell cycle in the G2/M phase. The results indicate that piperlongumine has the potential to be used as a therapeutic agent for human leukemia.

The role of ATP-binding cassette transporter A2 in childhood acute lymphoblastic leukemia multidrug resistance

Acute lymphoblastic leukemia (ALL) is one of the most prevalent hematologic malignancies in children. Although the cure rate of ALL has improved over the past decades, the most important reason for ALL treatment failure is multidrug resistance (MDR) phenomenon. The current study aims to explain the mechanisms involved in multidrug resistance of childhood ALL, and introduces ATP-binding cassette transporterA2 (ABCA2) as an ABC transporter gene which may have a high impact on MDR. Benefiting from articles published inreputable journals from1994 to date and experiments newly performed by our group, a comprehensive review is written about ABCA2 and its role in MDR regarding childhood ALL. ABCA2 transports drugs from the cytoplasm into the lysosomal compartment, where they may become degraded and exported from the cell. The aforementioned mechanism may contribute to MDR. It has been reported that ABCA2 may induce resistance to mitoxantrone, estrogen derivatives and estramustine. It is resistant to the aforementioned compounds. Furthermore, the overexpression ofABCA2 in methotrexate, vinblastine and/or doxorubicin treated Jurkat cells are observed in several publications. The recent study of our group showsthatthe overexpression ofABCA2 gene in children with ALL increases the risk of MDR by 15 times. ABCA2 is the second identified member of the ABCA; ABC transporters' subfamily. ABCA2 gene expression profile is suggested to be an unfavorable prognostic factor in ALL treatment. Better understanding of the MDR mechanisms and the factors involved may improve the therapeutic outcome of ALL by modifying the treatment protocols.

Host genetic variants of ABCB1 and IL15 influence treatment outcome in paediatric acute lymphoblastic leukaemia

BACKGROUND

Host germline variations and their potential prognostic importance is an emerging area of interest in paediatric ALL.

METHODS

We investigated the associations between 20 germline variations and various clinical end points in 463 children with ALL.

RESULTS

After adjusting for known prognostic factors, variants in two genes were found to be independently associated with poorer EFS: ABCB1 T/T at either 2677 (rs2032582) or 3435 (rs1045642) position (P=0.003) and IL15 67276493G/G (rs17015014; P=0.022). These variants showed a strong additive effect affecting outcome (P<0.001), whereby patients with both risk genotypes had the worst EFS (P=0.001), even after adjusting for MRD levels at the end of remission induction. The adverse effect of ABCB1 T/T genotypes was most pronounced in patients with favourable cytogenetics (P=0.011) while the IL15 67276493G/G genotype mainly affected patients without common chromosomal abnormalities (P=0.022). In both cytogenetic subgroups, increasing number of such risk genotypes still predicted worsening outcome (P<0.001 and=0.009, respectively).

CONCLUSION

These results point to the prognostic importance of host genetic variants, although the specific mechanisms remain unclarified. Inclusion of ABCB1 and IL15 variants may help improve risk assignment strategies in paediatric ALL.