The synergistic antileukemic effects of eltrombopag and decitabine in myeloid leukemia cells

Exploring the Potential of Eltrombopag: Room for More?

Since its introduction in clinical practice, eltrombopag (ELT) has demonstrated efficacy in heterogeneous clinical contexts, encompassing both benign and malignant diseases, thus leading researchers to make a more in-depth study of its mechanism of action. As a result, a growing body of evidence demonstrates that ELT displays many effects ranging from native thrombopoietin agonism to immunomodulation, anti-inflammatory, and metabolic properties. These features collectively explain ELT effectiveness in a broad spectrum of indications; moreover, they suggest that ELT could be effective in different, challenging clinical scenarios. We reviewed the extended ELT mechanism of action in various diseases, with the aim of further exploring its full potential and hypothesize new, fascinating indications.

Deferasirox combination with eltrombopag shows anti-myelodysplastic syndrome effects by enhancing iron deprivation-related apoptosis

Iron overload (IO) affected the survival of patients with myelodysplastic syndrome (MDS). Deferasirox (DFX) is widely used in patients with MDS for iron chelation therapy, but is not suitable for MDS patients with severe thrombocytopenia. Eltrombopag (ELT) is a type of thrombopoietin receptor (TPOR) analog used in the treatment of thrombocytopenia. Therefore, we sought to explore the synergistic effects and possible mechanisms of DFX combination with ELT in MDS cells. In our study, the combination of DFX with ELT synergistically inhibited proliferation, induced apoptosis and arrested cell cycle of MDS cells. Through the RNA-sequence and gene set enrichment analysis (GSEA), iron metabolism-related pathway played important roles in apoptosis of SKM-1 cells treated with DFX plus ELT. Transferrin receptor (TFRC) was significantly highly expressed in combination group than that in single agent groups, without affecting TPOR. Furthermore, the apoptosis of the combination group MDS cells could be partially reversed by ferric ammonium citrate (FAC), accompanied with decreased expression of TFRC. These results suggested that the combination of DFX and ELT synergistically induced apoptosis of MDS cells by enhancing iron deprivation-related pathway.

Clinical Trials Assessing Hypomethylating Agents Combined with Other Therapies: Causes for Failure and Potential Solutions

PURPOSE

Azacitidine and decitabine are hypomethylating agents (HMA), that is, both inhibit and deplete DNA methyltransferase 1 (DNMT1). HMAs are standard single-agent therapies for myelodysplastic syndromes and acute myelogenous leukemias. Several attempts to improve outcomes by combining HMAs with investigational agents, excepting with the BCL2-inhibitor venetoclax, have failed in randomized clinical trial (RCT) evaluations. We extract lessons from decades of clinical trials to thereby inform future work.

EXPERIMENTAL DESIGN

Serial single-agent clinical trials were analyzed for mechanism and pathway properties of HMAs underpinning their success, and for rules for dose and schedule selection. RCTs were studied for principles, dos and don'ts for productive combination therapy.

RESULTS

Single-agent HMA trial results encourage dose and schedule selection to increase S-phase-dependent DNMT1 targeting, and discourage doses that cause indiscriminate antimetabolite effects/cytotoxicity, because these attrit myelopoiesis reserves needed for clinical response. Treatment-related myelosuppression should prompt dose/frequency reductions of less active investigational agents rather than more active HMA. Administering cytostatic agents concurrently with HMA can antagonize S-phase-dependent DNMT1 targeting. Supportive care that enables on-time administration of S-phase (exposure-time)-dependent HMA could be useful. Agents that manipulate pyrimidine metabolism to increase HMA pro-drug processing into DNMT1-depleting nucleotide, and/or inhibit other epigenetic enzymes implicated in oncogenic silencing of lineage differentiation, could be productive, but doses and schedules should adhere to therapeutic index/molecular-targeted principles already learned.

CONCLUSIONS

More than 40 years of clinical trial history indicates mechanism, pathway, and therapeutic index properties of HMAs that underpin their almost exclusive success and teaches lessons for selection and design of combinations aiming to build on this treatment foundation.

Osteosarcoma in Children: Not Only Chemotherapy

Osteosarcoma (OS) is the most severe bone malignant tumor, responsible for altered osteoid deposition and with a high rate of metastasis. It is characterized by heterogeneity, chemoresistance and its interaction with bone microenvironment. The 5-year survival rate is about 67% for patients with localized OS, while it remains at 20% in case of metastases. The standard therapy for OS patients is represented by neoadjuvant chemotherapy, surgical resection, and adjuvant chemotherapy. The most used chemotherapy regimen for children is the combination of high-dose methotrexate, doxorubicin, and cisplatin. Considered that the necessary administration of high-dose chemotherapy is responsible for a lot of acute and chronic side effects, the identification of novel therapeutic strategies to ameliorate OS outcome and the patients' life expectancy is necessary. In this review we provide an overview on new possible innovative therapeutic strategies in OS.

Eltrombopag and its iron chelating properties in pediatric acute myeloid leukemia

Pediatric acute myeloid leukemia (AML) represents 20% of total childhood leukemia diagnoses and is characterized by poor prognosis with a long-term survival rate around the 50%, when patients are properly treated. The standard treatment for pediatric AML currently consists in a combination of cytarabine (Ara-C) and antracycline. Iron plays an important role in cancer development and progression. Targeting iron and its metabolism mediators could be a novel therapeutic strategy in cancer.Deferasirox (DFX) inhibits cancer cell proliferation and its use as an antiblastic drug could be suggested. Eltrombopag (ELT), a thrombopoietin receptor agonist used in immunethrombocytopenia, shows anticancer properties related to its emerging iron chelating properties. We compare the anticancer effect of classically used cytarabine with DFX and ELT effects in a pediatric AML cell line, THP-1, in order to identify innovative and more effective therapeutic strategies. ELT and DFX reduce intracellular iron concentration by inhibiting its uptake and by promoting its release. In particular, even though further investigations are needed to better understand the extact underlying action mechanisms, we demonstrated that ELT improves cytarabine antineoplastic activity in pediatric AML cell line.

Eltrombopag Effectiveness and Tolerability in Chronic Immune Thrombocytopenia: A Meta-Analysis

Eltrombopag is an orally administered, non-peptide, thrombopoietin receptor agonist which initiates thrombopoietin signaling and stimulates the production of normally functioning platelet. We aimed to do a systematic review and meta-analysis of currently available published data to verify whether eltrombopag treatment in patients with chronic immune-mediated thrombocytopenia can prolong survival. We searched for published, randomized, controlled trials in PubMed, Cochrane and Scopus databases using the following search strategy (“Eltrombopag” OR “Benzoates” OR “Hydrazines”) AND (“Idiopathic Thrombocytopenic Purpura” OR “immune thrombocytopenia” OR “Idiopathic Thrombocytopenic Purpuras” OR “Immune Thrombocytopenia” OR “Autoimmune Thrombocytopenia” OR “Werlhof”). The pooled relative risk (RR) showed that eltrombopag group has significantly higher overall platelet response than placebo group (MD = 3.42, 95% CI [2.51, 4.65], P > .0001); pooled results were homogenous (P = .27, I² = 22%). The pooled relative risk showed that eltrombopag group has lower incidence of any bleeding than placebo group (MD = 0.65, 95% CI [0.48, 0.87], P = .003); pooled results were heterogenous (P = .001, I² = 75%) and the detected heterogeneity was best resolved after excluding Bussel et al (P = .10). Homogeneous results were still favored eltrombopag group (MD = 0.75, 95% CI [0.60, 0.93], P = .008).

Effects of Iron Chelation in Osteosarcoma

BACKGROUND

Osteosarcoma is an aggressive bone tumor. It represents the principal cause of cancer-associated death in children. Considering the recent findings on the role of iron in cancer, iron chelation has been investigated for its antineoplastic properties in many tumors. Deferasirox is the most used iron chelator compound and in previous studies showed an anticancer effect in hematologic and solid malignancies. Eltrombopag is a Thrombopoietin receptor used in thrombocytopenia that also binds and mobilize iron. It demonstrated an effect on iron overload conditions and also in contrasting cancer cell proliferation.

OBJECTIVE

We analyzed the effects of deferasirox and eltrombopag in human osteosarcoma cells in an attempt to identify other therapeutic approaches for this tumor.

METHODS

We cultured and treated with deferasirox and Eltrombopag, alone and in combination, two human osteosarcoma cell lines, MG63 and 143B. After 72h exposure, we performed RTqPCR, Western Blotting, Iron Assay and cytofluorimetric assays to evaluate the effect on viability, apoptosis, cell cycle progression and ROS production.

RESULTS

The iron-chelating properties of the two compounds are also confirmed in osteosarcoma, but we did not observe any direct effect on tumor progression.

DISCUSSION

We tested deferasirox and eltrombopag, alone and in combination, in human osteosarcoma cells for the first time and demonstrated that their iron-chelating activity does not influence biochemical pathways related to cancer progression and maintenance.

CONCLUSION

Although further investigations on possible effects mediated by cells of the tumor microenvironment could be of great interest, in vitro iron chelation in osteosarcoma does not impair tumor progression.

Eltrombopag inhibits the proliferation of Ewing sarcoma cells via iron chelation and impaired DNA replication

Background

The treatment of Ewing sarcoma, an aggressive bone and soft tissue sarcoma, is associated with suboptimal outcomes and significant side-effects. Consequently, there is an urgent need to identify novel therapies that will improve outcomes for children and adults with Ewing sarcoma tumors while also decreasing treatment-related toxicities.

Methods

We analyzed data from the PRISM drug repurposing screen, which tested the activity of 4518 drugs across 578 cancer cell lines, to identify drugs that selectively inhibit the growth of Ewing sarcoma cell lines. We then tested the effects of a top hit from the screen on cell proliferation, cell cycle progression, and activation of the DNA damage pathway using Ewing sarcoma cell lines. We also used a CRISPR/Cas9 gene knockout approach to investigate the role of Schlafen 11 (SLFN11), a restriction factor for DNA replication stress that is overexpressed in Ewing sarcoma tumors, in mediating the sensitivity of Ewing sarcoma cells to the drug.

Results

We found that eltrombopag, an FDA-approved thrombopoietin-receptor agonist (TPO-RA) that is currently being evaluated as a treatment for chemotherapy-induced thrombocytopenia, inhibits the growth of Ewing sarcoma cell lines in vitro in proliferation and colony formation assays. However, from a mechanistic standpoint, the thrombopoietin receptor is not expressed in Ewing sarcoma cells and we show that eltrombopag impairs DNA replication and causes DNA damage in Ewing sarcoma cells by chelating iron, a known “off-target” effect of the drug. We also found that the sensitivity of Ewing sarcoma cells to eltrombopag is mediated, in part, by SLFN11, which regulates the cellular response to DNA replication stress.

Conclusions

Ewing sarcoma cell lines are sensitive to eltrombopag and this drug could improve outcomes for patients with Ewing sarcoma tumors by both targeting the tumor, via chelation of iron and inhibition of DNA replication, and reducing chemotherapy-induced thrombocytopenia, via stimulation of the thrombopoietin receptor.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12885-020-07668-6.

Decitabine and all-trans retinoic acid synergistically exhibit cytotoxicity against elderly AML patients via miR-34a/MYCN axis

This study aimed to investigate the efficacy and mechanism of decitabine (DAC) and all-trans retinoic acid (ATRA) in elderly acute myeloid leukemia (AML) patients and cultured cells. Our clinical trial enrolled 36 elderly patients who were judged ineligible for conventional chemotherapy, receiving DAC and ATRA regimen (DAC 20 mg/m² days 1-5; ATRA 20 mg/m² days 4-28 in the first cycle and days 1-28 in the subsequent cycle). Treated with a median of 3 cycles (range 1-6), 44.4 % of patients achieved complete remission (CR), 11.1 % achieved CR with incomplete peripheral count recovery (CRi) and 13.9 % achieved partial remission (PR). The median overall survival (OS) was 12.1 months; the 1-year and 2-year OS rates were 49.6 % and 17.2 %. In addition, our in vitro studies indicated that the antineoplastic activities of DAC and ATRA mutually reinforced, which induced growth inhibition, cell cycle arrest and apoptosis of AML cells. Meanwhile, we found DAC and ATRA inhibited DNMT1, activated miR-34a via promoter hypomethylation, down-regulated its target MYCN and thus exerted a synergistic antineoplastic effect. In conclusion, DAC plus ATRA regimen might be effective and well-tolerated for elderly patients partially through modulating miR-34a/MYCN axis.