Inhibitors of Chemoresistance Pathways in Combination with Ara-C to Overcome Multidrug Resistance in AML. A Mini Review

Pharmacological p38 MAPK inhibitor SB203580 enhances AML stem cell line KG1a chemosensitivity to daunorubicin by promoting late apoptosis, cell growth arrest in S-phase, and miR-328-3p upregulation

Acute myeloid leukaemia (AML) is characterized by uncontrolled proliferation of myeloid progenitor cells and impaired maturation, leading to immature cell accumulation in the bone marrow and bloodstream, resulting in hematopoietic dysfunction. Chemoresistance, hyperactivity of survival pathways, and miRNA alteration are major factors contributing to treatment failure and poor outcomes in AML patients. This study aimed to investigate the impact of the pharmacological p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 on the chemoresistance potential of AML stem cell line KG1a to the therapeutic drug daunorubicin (DNR). KG1a and chemosensitive leukemic HL60 cells were treated with increasing concentrations of DNR. Cell Titer-Glo®, flow cytometry, phosphokinase and protein arrays, Western blot technology, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were employed for assessment of cell viability, half-maximal inhibitory concentration (IC50) determination, apoptotic status detection, cell cycle analysis, apoptosis-related protein and gene expression monitoring. Confocal microscopy was used to visualize caspase and mitochondrial permeability transition pore (mPTP) activities. Exposed at various incubation times, higher DNR IC50 values were determined for KG1a cells than for HL60 cells, confirming KG1a cell chemoresistance potential. Exposed to DNR, late apoptosis induction in KG1a cells was enhanced after SB203580 pretreatment, defined as the combination treatment. This enhancement was confirmed by increased cleavage of poly(ADP-ribose) polymerase, caspase-9, caspase-3, and augmented caspase-3/-7 and mPTP activities in KG1a cells upon combination treatment, compared to DNR. Using phosphokinase and apoptosis protein arrays, the combination treatment decreased survival Akt phosphorylation and anti-apoptotic Bcl-2 expression levels in KG1a cells while increasing the expression levels of the tumor suppressor p53 and cyclin-dependent kinase inhibitor p21, compared to DNR. Cell cycle analysis revealed KG1a cell growth arrest in G2/M-phase caused by DNR, while combined treatment led to cell growth arrest in S-phase, mainly associated with cyclin B1 expression levels. Remarkably, the enhanced KG1a cell sensitivity to DNR after SB203580 pretreatment was associated with an increased upregulation of miR-328-3p and slight downregulation of miR-26b-5p, compared to DNR effect. Altogether, these findings could contribute to the development of a new therapeutic strategy by targeting the p38 MAPK pathway to improve treatment outcomes in patients with refractory or relapsed AML.

GAS5 promotes cytarabine induced myelosuppression via inhibition of hematopoietic stem cell differentiation

Cytarabine (Ara-C) is widely used in the induction chemotherapy for acute myeloid leukemia (AML). Association between LncRNA GAS5 genetic polymorphism and the recovery of hematopoietic function after Ara-C-based chemotherapy is observed. This study aimed to identify whether intervention of GAS5 expression and GAS5 genotype affect Ara-C-induced inhibition of hematopoietic stem cells (HSCs) differentiation. In this study, cord blood-derived CD34+ cells were cultured in vitro, and a cell model of myelosuppression was established by treatment of CD34+ cells with Ara-C. The effect of GAS5 overexpression, Ara-C treatment, and GAS5 rs55829688 genotype on the hematopoietic colony-forming ability of CD34+ cells was assessed using methylcellulose-based colony forming unit assay. GAS5 overexpression slowed down the proliferation of cord blood-derived CD34+ cells significantly (p < 0.05) and decreased their ability to form hematopoietic colonies in vitro. Ara-C significantly reduced the hematopoietic colony-forming ability of CD34+ cells in vitro (p < 0.0001), and overexpressing GAS5 further decreased the number of hematopoietic colonies. GAS5 expression was higher in CD34+ cells than in CD34- cells, and positively correlated with GATA1 mRNA expression in CD34+ cells in vitro culture. However, GAS5 genotype had no effect on the total number of hematopoietic colonies formed from cord blood-derived CD34+ cells. In conclusion, our study highlights that GAS5 inhibited the in vitro proliferation and reduced the hematopoietic colony-forming ability of cord blood-derived CD34+ cells, with the most pronounced effect observed on CFU-GEMM formation. GAS5 also enhanced the inhibitory effect of Ara-C on the in vitro hematopoietic ability of CD34+ HSCs.

E2F1 rs3213150 polymorphism influences cytarabine sensitivity and prognosis in patients with acute myeloid leukemia

Cytarabine (Ara-C) plays an irreplaceable role in the treatment of acute myeloid leukemia (AML). However, there are significant differences in efficacy among patients. Our previous studies found that E2F1 rs3213150 polymorphism was associated with remission rate of Ara-C chemotherapy, but the specific mechanism is not clear. This study aimed to further confirm the correlation between E2F1 rs3213150 polymorphism and Ara-C resistance and prognosis in AML patients, and to provide valuable information for elucidating the molecular mechanisms involved.

METHODS

Rs3213150 genotyping was performed in 922 AML patients by Sanger sequencing, and the effects of different genotypes on chemosensitivity and prognosis were analyzed by Logistic regression and Cox regression. Meanwhile, a prediction model of Ara-C chemotherapy resistance was established. The impact of rs3213150 polymorphism on E2F1 expression level was determined by luciferase reporter gene assay, and differentially expressed genes between patients with different genotypes were identified by RNA sequencing.

RESULTS

Compared with rs3213150 G allele carriers, patients with AA genotype had more obvious Ara-C resistance (41.94% vs. 27.94%, P = 0.002), shorter overall survival (529 d vs. 644 d, P = 0.008) and disease-free survival (519 d vs. 556 d, P = 0.023). Rs3213150G > A mutation resulted in decreased E2F1 expression.

CONCLUSION

E2F1 rs3213150 polymorphism influences the chemosensitivity and prognosis of Ara-C in Chinese AML patients.

Pinostrobin modulates FOXO3 expression, nuclear localization, and exerts antileukemic effects in AML cells and zebrafish xenografts

Acute myeloid leukemia (AML) is a disease characterized by abnormal cell proliferation in the bone marrow and is the most common quickly progressive leukemia in adults. Pinostrobin, a flavonoid phytochemical, has been reported to exhibit antioxidant, anti-inflammatory, and anticancer properties. In this study, we aimed to investigate the antileukemic effects of pinostrobin and its molecular mechanisms in human AML cells. Our study found that pinostrobin (0-80 μM) significantly reduced the viability of human AML cells, with the pronounced cytotoxic effects observed in MV4-11 > MOLM-13 > HL-60 > U-937 > THP-1 cells. Pinostrobin was found to suppress leukemia cell proliferation, modulate cell cycle progression, promote cell apoptosis, and induce monocytic differentiation in MV4-11 cells. In animal studies, pinostrobin significantly suppressed the growth of leukemia cells in a zebrafish xenograft model. Microarray-based transcriptome analysis showed that the differentially expressed genes (DEGs) in pinostrobin-treated cells were strongly associated with enriched Gene Ontology (GO) terms related to apoptotic process, cell death, cell differentiation, cell cycle progression, and cell division. Combining DisGeNET and STRING database analysis revealed that pinostrobin upregulates forkhead box 3 (FOXO3), a tumor suppressor in cancer development, and plays an essential role in controlling AML cell viability. Our study demonstrated that pinostrobin increases FOXO3 gene expression and promotes its nuclear translocation, leading to the inhibition of cell growth. Finally, the study found that pinostrobin, when combined with cytarabine, synergistically reduces the viability of AML cells. Our current findings shed light on pinostrobin's mechanisms in inhibiting leukemia cell growth, highlighting its potential as a chemotherapeutic agent or nutraceutical supplement for AML prevention or treatment.

Effective Prognostic Model for Therapy Response Prediction in Acute Myeloid Leukemia Patients

Acute myeloid leukemia (AML) is a hematopoietic disorder characterized by the malignant transformation of bone marrow-derived myeloid progenitor cells with extremely short survival. To select the optimal treatment options and predict the response to therapy, the stratification of AML patients into risk groups based on genetic factors along with clinical characteristics is carried out. Despite this thorough approach, the therapy response and disease outcome for a particular patient with AML depends on several patient- and tumor-associated factors. Among these, tumor cell resistance to chemotherapeutic agents represents one of the main obstacles for improving survival outcomes in AML patients. In our study, a new prognostic scale for the risk stratification of AML patients based on the detection of the sensitivity or resistance of tumor cells to chemotherapeutic drugs in vitro as well as MDR1 mRNA/P-glycoprotein expression, tumor origin (primary or secondary), cytogenetic abnormalities, and aberrant immunophenotype was developed. This study included 53 patients diagnosed with AML. Patients who received intensive or non-intensive induction therapy were analyzed separately. Using correlation, ROC, and Cox regression analyses, we show that the risk stratification of AML patients in accordance with the developed prognostic scale correlates well with the response to therapy and represents an independent predictive factor for the overall survival of patients with newly diagnosed AML.

Prolactin receptor signaling induces acquisition of chemoresistance and reduces clonogenicity in acute myeloid leukemia

BACKGROUND

Development of precision medicine requires the identification of easily detectable and druggable biomarkers. Despite recent targeted drug approvals, prognosis of acute myeloid leukemia (AML) patients needs to be greatly improved, as relapse and refractory disease are still difficult to manage. Thus, new therapeutic approaches are needed. Based on in silico-generated preliminary data and the literature, the role of the prolactin (PRL)-mediated signaling was interrogated in AML.

METHODS

Protein expression and cell viability were determined by flow cytometry. Repopulation capacity was studied in murine xenotransplantation assays. Gene expression was measured by qPCR and luciferase-reporters. SA-β-Gal staining was used as a senescence marker.

RESULTS

The prolactin receptor (PRLR) was upregulated in AML cells, as compared to their healthy counterpart. The genetic and molecular inhibition of this receptor reduced the colony-forming potential. Disruption of the PRLR signaling, either using a mutant PRL or a dominant-negative isoform of PRLR, reduced the leukemia burden in vivo, in xenotransplantation assays. The expression levels of PRLR directly correlated with resistance to cytarabine. Indeed, acquired cytarabine resistance was accompanied with the induction of PRLR surface expression. The signaling associated to PRLR in AML was mainly mediated by Stat5, in contrast to the residual function of Stat3. In concordance, Stat5 mRNA was significantly overexpressed at mRNA levels in relapse AML samples. A senescence-like phenotype, measured by SA-β-gal staining, was induced upon enforced expression of PRLR in AML cells, partially dependent on ATR. Similar to the previously described chemoresistance-induced senescence in AML, no cell cycle arrest was observed. Additionally, the therapeutic potential of PRLR in AML was genetically validated.

CONCLUSIONS

These results support the role of PRLR as a therapeutic target for AML and the further development of drug discovery programs searching for specific PRLR inhibitors.

Anti-Leukemic Activity of Brassica-Derived Bioactive Compounds in HL-60 Myeloid Leukemia Cells

Acute myeloid leukemia (AML) is a cancer of the myeloid blood cells mainly treated with chemotherapy for cancer remission, but this non-selective treatment also induces numerous side effects. Investigations with bioactive compounds from plant-derived foods against cancer have increased in the last years because there is an urgent need to search for new anti-leukemic agents possessing higher efficacy and selectivity for AML cells and fewer negative side effects. In this study, we analyzed the anti-leukemic activity of several phytochemicals that are representative of the major classes of compounds present in cruciferous foods (glucosinolates, isothiocyanates, hydroxycinnamic acids, flavonols, and anthocyanins) in the human acute myeloid leukemia cell line HL-60. Our results revealed that among the different Brassica-derived compounds assayed, sulforaphane (SFN) (an aliphatic isothiocyanate) showed the most potent anti-leukemic activity with an IC50 value of 6 µM in dose-response MTT assays after 48 h of treatment. On the other hand, chlorogenic acid (a hydroxycinnamic acid) and cyanidin-3-glucoside (an anthocyanin) also displayed anti-leukemic potential, with IC50 values of 7 µM and 17 µM after 48 h of incubation, respectively. Importantly, these compounds did not show significant cell toxicity in macrophages-like differentiated cells at 10 and 25 µM, indicating that their cytotoxic effects were specific to AML cancer cells. Finally, we found that these three compounds were able to induce the NRF2/KEAP1 signaling pathway in a dose-dependent manner, highlighting SFN as the most potent NRF2 activator. Overall, the present evidence shed light on the potential for using foods and ingredients rich in anticancer bioactive phytochemicals from Brassica spp.

5-Demethylnobiletin Inhibits Cell Proliferation, Downregulates ID1 Expression, Modulates the NF-κB/TNF-α Pathway and Exerts Antileukemic Effects in AML Cells

Acute myeloid leukemia (AML) is characterized by the dysregulation of hematopoietic cell proliferation, resulting in the accumulation of immature myeloid cells in bone marrow. 5-Demethylnobiletin (5-demethyl NOB), a citrus 5-hydroxylated polymethoxyflavone, has been reported to exhibit various bioactivities, such as antioxidant, anti-inflammatory and anticancer properties. In this study, we investigated the antileukemic effects of 5-demethyl NOB and its underlying molecular mechanisms in human AML cells. We found that 5-demethyl NOB (20−80 μM) significantly reduced human leukemia cell viability, and the following trend of effectiveness was observed: THP-1 ≈ U-937 > HEL > HL-60 > K562 cells. 5-Demethyl NOB (20 and 40 μM) modulated the cell cycle through the regulation of p21, cyclin E1 and cyclin A1 expression and induced S phase arrest. 5-Demethyl NOB also promoted leukemia cell apoptosis and differentiation. Microarray-based transcriptome, Gene Ontology (GO) and Gene Set Enrichment Analysis (GSEA) of differentially expressed genes (DEGs) analysis showed that the expression of inhibitor of differentiation/DNA binding 1 (ID1), a gene associated with the GO biological process (BP) cell population proliferation (GO: 0008283), was most strongly suppressed by 5-demethyl NOB (40 μM) in THP-1 cells. We further demonstrated that 5-demethyl NOB-induced ID1 reduction was associated with the inhibition of leukemia cell growth. Moreover, DEGs involved in the hallmark gene set NF-κB/TNF-α signaling pathway were markedly enriched and downregulated by 5-demethyl NOB. Finally, we demonstrated that 5-demethyl NOB (20 and 40 μM), combined with cytarabine, synergistically reduced THP-1 and U-937 cell viability. Our current findings support that 5-demethyl NOB dramatically suppresses leukemia cell proliferation and may serve as a potential phytochemical for human AML chemotherapy.

Transfer of IGF2BP3 Through Ara-C-Induced Apoptotic Bodies Promotes Survival of Recipient Cells

Cytosine arabinoside (Ara-C) has been the standard therapeutic agent for myelodysplastic syndromes (MDS) and adult acute myeloid leukemia (AML) patients for decades. Considerable progress has been made in development of new treatments for MDS/AML patients, but drug resistance remains a major clinical problem. Apoptotic bodies (ABs), produced by late apoptotic cells, can enclose bioactive components that affect cell-cell interactions and disease progression. We isolated and identified drug-induced ABs from Ara-C-tolerance cells. Treatment of sensitive cells with Ara-C-induced ABs resulted in Ara-C-resistant phenotype. We further investigated components and functions of Ara-C-induced ABs. Proteomics analysis in combination with mass spectrometry revealed that Ara-C-induced ABs carried numerous RNA-binding proteins, notably including insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3). Delivery of AB-encapsulated IGF2BP3 promoted survival of recipient cells by activating PI3K-AKT and p42-44 MAPK pathways. High IGF2BP3 level in ABs from MDS/AML patient plasma was correlated with poor overall survival. Our findings demonstrate that AB-derived IGF2BP3 plays an essential role in acquired Ara-C resistance in MDS/AML patients, and is a potential therapeutic target for suppression of Ara-C resistance.

Lysosome-mediated chemoresistance in acute myeloid leukemia

Despite the outstanding advances in understanding the biology underlying the pathophysiology of acute myeloid leukemia (AML) and the promising preclinical data published lastly, AML treatment still relies on a classic chemotherapy regimen largely unchanged for the past five decades. Recently, new drugs have been approved for AML, but the real clinical benefit is still under evaluation. Nevertheless, primary refractory and relapse AML continue to represent the main clinical challenge, as the majority of AML patients will succumb to the disease despite achieving a complete remission during the induction phase. As such, treatments for chemoresistant AML represent an unmet need in this disease. Although great efforts have been made to decipher the biological basis for leukemogenesis, the mechanism by which AML cells become resistant to chemotherapy is largely unknown. The identification of the signaling pathways involved in resistance may lead to new combinatory therapies or new therapeutic approaches suitable for this subset of patients. Several mechanisms of chemoresistance have been identified, including drug transporters, key secondary messengers, and metabolic regulators. However, no therapeutic approach targeting chemoresistance has succeeded in clinical trials, especially due to broad secondary effects in healthy cells. Recent research has highlighted the importance of lysosomes in this phenomenon. Lysosomes' key role in resistance to chemotherapy includes the potential to sequester drugs, central metabolic signaling role, and gene expression regulation. These results provide further evidence to support the development of new therapeutic approaches that target lysosomes in AML.

Loss of the redox mitochondrial protein mitoNEET leads to mitochondrial dysfunction in B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (ALL) affects both pediatric and adult patients. Chemotherapy resistant tumor cells that contribute to minimal residual disease (MRD) underlie relapse and poor clinical outcomes in a sub-set of patients. Targeting mitochondrial oxidative phosphorylation (OXPHOS) in the treatment of refractory leukemic cells is a potential novel approach to sensitizing tumor cells to existing standard of care therapeutic agents. In the current study, we have expanded our previous investigation of the mitoNEET ligand NL-1 in the treatment of ALL to interrogate the functional role of the mitochondrial outer membrane protein mitoNEET in B-cell ALL. Knockout (KO) of mitoNEET (gene: CISD1) in REH leukemic cells led to changes in mitochondrial ultra-structure and function. REH cells have significantly reduced OXPHOS capacity in the KO cells coincident with reduction in electron flow and increased reactive oxygen species. In addition, we found a decrease in lipid content in KO cells, as compared to the vector control cells was observed. Lastly, the KO of mitoNEET was associated with decreased proliferation as compared to control cells when exposed to the standard of care agent cytarabine (Ara-C). Taken together, these observations suggest that mitoNEET is essential for optimal function of mitochondria in B-cell ALL and may represent a novel anti-leukemic drug target for treatment of minimal residual disease.