Molecular mechanisms of drug resistance in acute myeloid leukaemia

Dexamethasone Sensitizes Acute Monocytic Leukemia Cells to Ara-C by Upregulating FKBP51

In this study, we demonstrated that the expression of FK506 binding protein 51 (FKBP51) is upregulated in acute monocytic leukemia (AML-M5) cells by dexamethasone and aimed to investigate the possible effects of FKBP51 on the growth and cytarabine sensitivity of AML-M5 cells. THP-1 and U937cells were used to establish AML-M5 cell models with FKBP51 overexpression and knockdown, respectively. Cell proliferation, apoptosis and response to cytarabine were investigated by cell cycle, CCK-8 and Flow cytometry analyses. The mice experiment was conducted to detect the role of FKBP51 on AML-M5 cells proliferation and antileukemia effect of Ara-C/Dexamethasone co-therapy in vivo. Western blots were employed to determine protein expression levels. FKBP51 upregulation significantly attenuated THP-1 cell proliferation and sensitized the cells to cytarabine treatment which was further enhanced by dexamethasone. These effects were indicated by decreases in cell viability, S-G2/M phase cell cycle distribution, cytarabine 50% inhibitory concentration (IC50) values and increases in apoptosis and were supported by decreased phosphorylation levels of AKT, GSK3β and FOXO1A and decreased levels of BCL-2 and increased levels of P21 and P27. In contrast, FKBP51 knockdown led to excessive U937 cell proliferation and cytarabine resistance, as indicated by increased cell viability and S-G2/M phase cell cycle distribution, decreased apoptosis, increased phosphorylation levels of AKT, GSK3β and FOXO1A, and increased BCL-2 and decreased P21 and P27 expression. In addition, an AKT inhibitor blocked cell cycle progression and reduced cell viability in all groups of cells. Furthermore, SAFit2, a specific FKBP51 inhibitor, increased U937 cell viability and cytarabine resistance as well as AKT phosphorylation. In conclusion, FKBP51 decelerates proliferation and improves the cytarabine sensitivity of AML-M5 cells by inhibiting AKT pathways, and dexamethasone in combination with Ara-C improves the chemosensitivity of AML-M5.

Harnessing Gene Expression Profiles for the Identification of Ex Vivo Drug Response Genes in Pediatric Acute Myeloid Leukemia

Novel treatment strategies are of paramount importance to improve clinical outcomes in pediatric AML. Since chemotherapy is likely to remain the cornerstone of curative treatment of AML, insights in the molecular mechanisms that determine its cytotoxic effects could aid further treatment optimization. To assess which genes and pathways are implicated in tumor drug resistance, we correlated ex vivo drug response data to genome-wide gene expression profiles of 73 primary pediatric AML samples obtained at initial diagnosis. Ex vivo response of primary AML blasts towards cytarabine (Ara C), daunorubicin (DNR), etoposide (VP16), and cladribine (2-CdA) was associated with the expression of 101, 345, 206, and 599 genes, respectively (p < 0.001, FDR 0.004–0.416). Microarray based expression of multiple genes was technically validated using qRT-PCR for a selection of genes. Moreover, expression levels of BRE, HIF1A, and CLEC7A were confirmed to be significantly (p < 0.05) associated with ex vivo drug response in an independent set of 48 primary pediatric AML patients. We present unique data that addresses transcriptomic analyses of the mechanisms underlying ex vivo drug response of primary tumor samples. Our data suggest that distinct gene expression profiles are associated with ex vivo drug response, and may confer a priori drug resistance in leukemic cells. The described associations represent a fundament for the development of interventions to overcome drug resistance in AML, and maximize the benefits of current chemotherapy for sensitive patients.

Potential CD34 signaling through phosphorylated-BAD in chemotherapy-resistant acute myeloid leukemia

Acute myeloid leukemia (AML) constitutively express growth factors and cytokines for survival. Chemotherapy alters these signals to induce cell death. However, drug resistance in AML remains a major hindrance to successful treatment and early warning is unavailable. Modulation of signaling pathways during chemotherapy may provide a window to detect response and predict treatment outcome. Blood samples collected from AML patients before and at day-3 of induction therapy were compared for changes in expression of CD117, CD34, pro-inflammatory cytokines and mediators of Akt and MAPK pathways, using multi-color flow cytometry. Nine patients were diagnosed as drug-resistant and seven sensitive to chemotherapy. Twelve were paired. Average percentages of CD34 (66.8 ± 11.7% vs. 26.2 ± 5.8%, p = 0.033) and pBAD (66.9 ± 8.2% vs. 28.9 ± 8.2%, p = 0.016) were significantly increased in chemo-resistant (N = 9) compared to chemo-sensitive (N = 5) samples. Percentages of CD34 were strongly correlated with pBAD (R = 0.785; p = 0.001; N = 14) and pFKHR (R = 0.755; p = 0.002; N = 14) at day-3 induction. Chemo-sensitive cases expressed significantly higher percentages of IL-18Rα (71.9 ± 9.6% vs. 29.8 ± 5.8%, p = 0.016). Though not significantly different in the outcome, IL-1β was strongly associated with activated Akt-S473, IL-6 with phosphorylated JNK and FKHR while TNF-α appeared to trigger Bim, in treated samples. These preliminary results suggested AML cells resistant to chemotherapy increased expression of CD34 and may signal through pBAD while cells sensitive to chemotherapy-induced IL18Rα expression. These were observed early during induction therapy. Identifying CD34 is interesting as it is a convenient marker to monitor drug-resistance in AML patients. Inhibition of CD34 and pBAD signaling may be important in treating drug-resistant AML.

Chemotherapy selection pressure alters sphingolipid composition and mitochondrial bioenergetics in resistant HL-60 cells

The combination of daunorubicin (dnr) and cytarabine (Ara-C) is a cornerstone of treatment for acute myelogenous leukemia (AML); resistance to these drugs is a major cause of treatment failure. Ceramide, a sphingolipid (SL), plays a critical role in cancer cell apoptosis in response to chemotherapy. Here, we investigated the effects of chemotherapy selection pressure with Ara-C and dnr on SL composition and enzyme activity in the AML cell line HL-60. Resistant cells, those selected for growth in Ara-C- and dnr-containing medium (HL-60/Ara-C and HL-60/dnr, respectively), demonstrated upregulated expression and activity of glucosylceramide synthase, acid ceramidase (AC), and sphingosine kinase 1 (SPHK1); were more resistant to ceramide than parental cells; and displayed sensitivity to inhibitors of SL metabolism. Lipidomic analysis revealed a general ceramide deficit and a profound upswing in levels of sphingosine 1-phosphate (S1P) and ceramide 1-phosphate (C1P) in HL-60/dnr cells versus parental and HL-60/Ara-C cells. Both chemotherapy-selected cells also exhibited comprehensive upregulations in mitochondrial biogenesis consistent with heightened reliance on oxidative phosphorylation, a property that was partially reversed by exposure to AC and SPHK1 inhibitors and that supports a role for the phosphorylation system in resistance. In summary, dnr and Ara-C selection pressure induces acute reductions in ceramide levels and large increases in S1P and C1P, concomitant with cell resilience bolstered by enhanced mitochondrial remodeling. Thus, strategic control of ceramide metabolism and further research to define mitochondrial perturbations that accompany the drug-resistant phenotype offer new opportunities for developing therapies that regulate cancer growth.

In-silico comparison of two induction regimens (7 + 3 vs 7 + 3 plus additional bone marrow evaluation) in acute myeloid leukemia treatment

BACKGROUND

Clinical integration of systems biology approaches is gaining in importance in the course of digital revolution in modern medicine. We present our results of the analysis of an extended mathematical model describing abnormal human hematopoiesis. The model is able to describe the course of an acute myeloid leukemia including its treatment. In first-line treatment of acute myeloid leukemia, the induction chemotherapy aims for a rapid leukemic cell reduction. We consider combinations of cytarabine and anthracycline-like chemotherapy. Both substances are widely used as standard treatment to achieve first remission. In particular, we compare two scenarios: a single-induction course with 7 days cytarabine and 3 day of anthracycline-like treatment (7 + 3) with a 7 + 3 course and a bone marrow evaluation that leads, in case of insufficient leukemic cell reduction, to the provision of a second chemotherapy course. Three scenarios, based on the leukemias growth kinetics (slow, intermediate, fast), were analyzed. We simulated different intensity combinations for both therapy schemata (7 + 3 and 7 + 3 + evaluation).

RESULTS

Our model shows that within the 7 + 3 regimen a wider range of intensity combinations result in a complete remission (CR), compared to 7 + 3 + evaluation (fast: 64.3% vs 46.4%; intermediate: 63.7% vs 46.7%; slow: 0% vs 0%). Additionally, the number of simulations resulting in a prolonged CR was higher within the standard regimen (fast: 59.8% vs 40.1%; intermediate: 48.6% vs 31.0%; slow: 0% vs 0%). On the contrary, the 7 + 3 + evaluation regimen allows CR and prolonged CR by lower chemotherapy intensities compared to 7 + 3. Leukemic pace has a strong impact on treatment response and especially on specific effective doses. As a result, faster leukemias are characterized by superior treatment outcomes and can be treated effectively with lower treatment intensities.

CONCLUSIONS

We could show that 7 + 3 treatment has considerable more chemotherapy combinations leading to a first CR. However, the 7 + 3 + evaluation regimen leads to CR for lower therapy intensity and presumably less side effects. An additional evaluation can be considered beneficial to control therapy success, especially in low dose settings. The treatment success is dependent on leukemia growth dynamics. The determination of leukemic pace should be a relevant part of a personalized medicine.

The Onus of Sphingolipid Enzymes in Cancer Drug Resistance

Chemotherapy resistance, inherent or acquired, represents a serious barrier to the successful treatment of cancer. Although drug efflux, conducted by plasma membrane-resident proteins, detoxification enzymes, cell death inhibition, and DNA damage repair are ensemble players in this unwanted biology, a full understanding of the many in concert molecular mechanisms driving drug resistance is lacking. Recent discoveries in sphingolipid (SL) metabolism have provided significant insight into the role of these lipids in cancer growth; however, considerably less is known with respect to SLs and the drug-resistant phenotype. One exception here is enhanced ceramide glycosylation, a hallmark of multidrug resistance that is believed responsible, in part, for diminishing ceramides tumor-suppressor potential. This chapter will review various aspects of SL biology that relate to chemotherapy resistance and extend this topic to acknowledge the role of chemotherapy selection pressure in promoting dysregulated SL metabolism, a characteristic in cancer and an exploitable target for therapy.

MRP1 and P-glycoprotein expression assays would be useful in the additional detection of treatment non-responders in CML patients without ABL1 mutation

We evaluated the ability of the rhodamine-123 efflux assay, multidrug resistance-associated protein-1 (MRP1) expression assay and P-glycoprotein (Pgp) expression assay to discriminate chronic myelogenous leukemia (CML) patients who had failed treatment or were at risk of failure. Each assay was performed in blood samples from CML patients (n=224) treated with tyrosine kinase inhibitors, taken at diagnosis (n=14) and follow-up (n=210). Patient samples were categorized as optimal response (n=120), suboptimal response (n=54), and treatment failure (n=36). Treatment-failed patients had a significantly higher MRP1 expression (5.24% vs. 3.54%, P=0.006) and Pgp expression (5.25% vs. 3.48%, P=0.005) than responders. Both MRP1 (%) and Pgp (%) were highly specific (95.2% and 94.5%) and relatively accurate (83.0% and 82.5%) in the detection of treatment non-responders. Of treatment-failed patients, 41.2% had a positive result in at least one assay and of these patients without ABL1 kinase domain mutation, 51.9% were positive in at least one assay. However, the rhodamine-123 efflux assay failed to discriminate two patient groups. Thus, both MRP1 and Pgp expression assays could be useful for additional identification of treatment non-responders in CML patients without ABL1 mutation.

ABCB1 polymorphisms correlate with susceptibility to adult acute leukemia and response to high-dose methotrexate

The aim of this study is to investigate the association of ABCB1 polymorphisms with susceptibility to adult acute leukemia, and the influence of ABCB1 polymorphisms on the efficacy of high-dose methotrexate (HDMTX). ABCB1 polymorphisms in 178 acute leukemia patients (case group) and 150 healthy subjects (control group) were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. All patients received HDMTX therapy. Correlation analysis was performed to explore the associations of ABCB1 polymorphisms with MTX concentration and efficacy of MTX therapy. All statistical analyses were conducted with SPSS 19.0 software. The frequency of TT genotype and T allele on ABCB1 3435C > T in case group were significantly higher than the control group (P < 0.05), while no statistical difference between the two groups was observed in genotypic distribution and allele frequencies of ABCB1 2677G > T/A (P > 0.05). Furthermore, 24-h MTX concentration of patients carrying TT and TA genotypes on 2677G > T/A was higher than carriers with other genotypes (P < 0.05), and 24-h MTX concentration of patients with TT and CT genotypes on 3435C > T was also apparently higher than carriers with CC genotype (P < 0.05). In addition, ABCB1 polymorphisms were connected with increased risk of liver dysfunction and infection (P < 0.05). Complete remission (CR) rate in patients carrying GG on 2677G > T/A was markedly lower than carriers with non-GG genotype (P < 0.05). ABCB1 3435C > T polymorphisms may be associated with susceptibility to acute leukemia, and ABCB1 polymorphisms might be a sensitive indicator for predicting efficacy of MTX therapy in the treatment of acute leukemia.

MicroRNA-21 regulates the sensitivity to cisplatin in a human osteosarcoma cell line

BACKGROUND

Recent studies have shown that microRNA-21 (miR-21) is overexpressed in solid tumors and implicated in the modulation of drug-induced resistance.

METHODS

In this study, we investigated the anti-tumor effects of miR-21 on the sensitivity of osteosarcoma cells to CDDP.

RESULTS

Changes in the sensitivity of osteosarcoma cells to CDDP were examined after transfection with miR-21 mimics or anti-miR-21 or bcl-2 siRNA in combination with CDDP. Osteosarcoma cells transfected with miR-21 mimics were significantly resistant to CDDP, while suppression of miR-21 in osteosarcoma cells led to enhanced CDDP cytotoxicity. Moreover, the miR-21-induced changes in chemoresponse were ameliorated by down-regulation of bcl-2 by its siRNA.

CONCLUSION

The miR-21 in osteosarcoma cells is a significant modulator of the anti-tumor effect of CDDP by regulating the expression of bcl-2, and the study reveals a novel mechanism of osteosarcoma drug resistance.

Prognostic and therapeutic relevance of c-FLIP in acute myeloid leukaemia

Chemoresistance is a major contributor to the aggressiveness of AML and is often due to insufficient apoptosis. The CFLAR gene is expressed as long and short splice forms encoding the anti-apoptotic proteins c-FLIP(L) and c-FLIP(S) (CFLAR(L) and CFLAR(S) , respectively) that play important roles in drug resistance. In univariate analyses of CFLAR mRNA expression in adult AML patients, those individuals with higher than median mRNA expression of the long splice form CFLAR(L) (but not the short splice form) had significantly lower 3 year overall survival (P = 0·04) compared to those with low expression. In cell line studies, simultaneous down-regulation of c-FLIP(L) and c-FLIP(S) proteins using siRNA induced apoptosis in U937 and NB-4 AML cells, but not K562 or OCI-AML3 cells. However, dual c-FLIP(L/S) downregulation sensitized all four cell lines to apoptosis induced by recombinant tumour necrosis factor-related apoptosis-inducing ligand (rTRAIL). Moreover, specific downregulation of c-FLIP(L) was found to recapitulate the phenotypic effects of dual c-FLIP(L/S) downregulation. The histone deacetylase (HDAC)1/2/3/6 inhibitor Vorinostat was found to potently down-regulate c-FLIP(L) expression by transcriptional and post-transcriptional mechanisms and to sensitize AML cells to rTRAIL. Further analyses using more selective HDAC inhibitors revealed that HDAC6 inhibition was not required for c-FLIP(L) down-regulation. These results suggest that c-FLIP(L) may have clinical relevance both as a prognostic biomarker and potential therapeutic target for HDAC inhibitors in AML although this requires further study.

Class I phosphoinositide 3-kinases in normal and pathologic hematopoietic cells

Class I phosphoinositide 3-kinases which produce the D3-phosphoinositide second messenger phosphatidylinositol 3,4,5-trisphosphate in response to membrane receptors activation play a critical role in cell proliferation, survival, metabolism, and motility. These lipid kinases and the phosphatases regulating the level of D3-phosphoinositides have been an intense area of research these last two decades. The class I phosphoinositide 3-kinases signaling is found aberrantly activated in numerous human cancers, including in malignant hemopathies, and are important therapeutic targets for cancer therapy. Haematopoiesis is an ongoing process which generates the distinct blood cell types from a common hematopoietic stem cell through the action of a variety of cytokines. In the human adult hematopoiesis occurs primarily in the bone marrow, and defects in hematopoiesis result in diseases, such as anemia, thrombocytopenia, myeloproliferative syndromes, or leukemia. Here we give a brief overview of the role of class I phosphoinositide 3-kinases in hematopoietic stem cells, in hematopoietic lineage development and in leukemia, particularly in acute myeloid leukemia and summarize the potential therapeutic implications.

Involvement of miR-21 in resistance to daunorubicin by regulating PTEN expression in the leukaemia K562 cell line

Recent studies have shown microRNA-21 (miR-21) is overexpressed in several types of cancer and contributes to tumor resistance to chemotherapy. In this study, we investigated whether miR-21 mediated resistance of the leukaemia cell line K562 to the chemotherapeutic agent daunorubicin (DNR). miR-21 expression was upregulated in the DNR resistant cell line K562/DNR compared to its parental line K562. Stable transfection of miR-21 induced drug resistance in K562, while suppression of miR-21 in K562/DNR led to enhanced DNR cytotoxicity. Additional experiments indicate that the mechanism of miR-21 drug resistance involves the PI3K/Akt pathway and changes following PTEN protein expression. This study provides a novel mechanism for understanding leukaemia drug resistance.

Variation of MDR proteins expression and activity levels according to clinical status and evolution of CML patients

The involvement of the multidrug resistance (MDR) mediated by ABC transporter proteins P-glycoprotein (Pgp) and multidrug resistance-associated protein-1 (MRP1) overexpressions in patients with chronic myeloid leukemia (CML) are not completely understood. Pgp and MRP1 expressions and activity were analyzed in samples from 158 patients with chronic myeloid leukemia (CML). Using flow cytometry, Pgp expression was more frequently observed in early chronic (P = 0.00) and in advanced (P = 0.02) CML phases when it was compared to MRP1 expression. Variation of MDR expression and activity were observed during the CML evolution in patients previously treated with interferon and imatinib. In the K562-Lucena cell line, Pgp positive, imatinib caused an enhancing in Pgp expression at protein and mRNA levels, whereas in the Pgp negative cell line, this drug was capable of decreasing MDR1/Pgp mRNA levels. Our result emphasizes the importance of understanding the different aspects of MDR status in patients with CML when they are under investigation in determining imatinib resistance.

mRNA expression profile of multidrug resistance genes in childhood acute lymphoblastic leukemia. Low expression levels associated with a higher risk of toxic death

BACKGROUND

Increased activity of multidrug resistance (MDR) genes has been associated with treatment failure in acute leukemias, although with controversial reports. The objective of the present study was to assess the expression profile of the genes related to MDR: ABCB1, ABCC1, ABCC3, ABCG2, and LRP/MVP in terms of the clinical and biological variable and the survival of children with acute lymphoblastic leukemia (ALL).

PROCEDURE

The levels of mRNA expression of the drug resistance genes ABCB1, ABCC1, ABCC3, ABCG2, and LRP/MVP were analyzed by quantitative real-time PCR using the median values as cut-off points, in consecutive samples from 140 children with ALL at diagnosis.

RESULTS

Expression levels of the ABCG2 gene in the patient group as a whole (P = 0.05) and of the ABCG2 and ABCC1 genes in patients classified as being at high risk were associated with higher rates of 5-year event-free survival (EFS) (P = 0.04 and P = 0.01). Expression levels of the ABCG2 gene below the median were associated with a greater chance of death related to treatment toxicity for the patient group as a whole (P = 0.009) and expression levels below the median of the ABCG2 and ABCC1 genes were associated with a greater chance of death due to treatment toxicity for the high-risk group (P = 0.02 and P = 0.03, respectively).

CONCLUSION

The present data suggest a low participation of the drug efflux genes in treatment failure in patients with childhood ALL. However, the low expression of some of these genes may be associated with a higher death risk related to treatment toxicity.

Drug-resistant AML cells and primary AML specimens are killed by 111In-anti-CD33 monoclonal antibodies modified with nuclear localizing peptide sequences

Multidrug resistance (MDR) is a major challenge to the successful treatment of acute myeloid leukemia (AML). Our purpose was to determine whether (111)In-HuM195 anti-CD33 antibodies modified with peptides harboring nuclear localizing sequences (NLS) could kill drug-resistant AML cell lines and primary AML patient specimens expressing MDR transporters through the emission of Auger electrons.

METHODS

HuM195, M195, and irrelevant mouse IgG (mIgG) were conjugated to 10+/-3 NLS peptides and then labeled with (111)In by diethylenetriaminepentaacetic acid substitution to a specific activity of 1-8 MBq/microg. The binding affinity of HuM195 and M195 was determined for HL-60 and mitoxantrone-resistant HL-60-MX-1 cells. Nuclear localization of (111)In-NLS-HuM195, (111)In-NLS-M195, (111)In-HuM195, and (111)In-M195 was measured by subcellular fractionation. The antiproliferative effects of (111)In-NLS-HuM195, (111)In-NLS-M195, (111)In-HuM195, and (111)In-M195 (2.5-250 kBq/well) on HL-60 and HL-60-MX-1 were studied using the WST-1 assay. Clonogenic survival of HL-60 and HL-60-MX-1 leukemic cells and 10 primary AML specimens with MDR phenotype (assessed by flow cytometry) was determined after exposure for 3 h at 37 degrees C to 2.5-250 mBq/cell of (111)In-NLS-HuM195, (111)In-HuM195, or (111)In-NLS-mIgG. Clonogenic survival versus the amount of radioactivity incubated with the cells (mBq/cell) was plotted, and the mean lethal amount of radioactivity and the lower asymptote of the curve (plateau) were determined.

RESULTS

The (111)In-labeled anti-CD33 monoclonal antibodies HuM195 and M195 modified with NLS were efficiently routed to the nucleus of HL-60 cells and their mitoxantrone-resistant clone after CD33-mediated internalization. The following are the principal findings of our study: (111)In-NLS-HuM195 was more effective at killing HL-60 and HL-60-MX-1 cells than was (111)In-HuM195, a strong correlation between the specific activity of the (111)In-labeled radioimmunoconjugates and their cytotoxicity toward AML cells existed, and leukemic cells from patients were killed by (111)In-NLS-M195 or (111)In-M195, but the cytotoxic response among specimens was heterogeneous.

CONCLUSION

NLS conjugation enhanced the nuclear uptake and cytotoxicity of (111)In-HuM195 and (111)In-M195 toward drug-resistant AML cell lines as well as patient specimens expressing a diversity of MDR phenotypes, including Pgp-170, BCRP1, or MRP1 transporters. Targeted Auger electron radioimmunotherapy using (111)In-labeled anti-CD33 monoclonal antibodies modified with NLS may be able to overcome MDR and provide a means of treating chemotherapy-resistant myeloid leukemias in patients.