Epigenetic Reprogramming and Emerging Epigenetic Therapies in CML

Clinical pharmacokinetics and drug-drug interactions of tyrosine-kinase inhibitors in chronic myeloid leukemia: A clinical perspective

In the past decade, numerous tyrosine kinase inhibitors (TKIs) have been introduced in the treatment of chronic myeloid leukemia. Given the significant interpatient variability in TKIs pharmacokinetics, potential drug-drug interactions (DDIs) can greatly impact patient therapy. This review aims to discuss the pharmacokinetic characteristics of TKIs, specifically focusing on their absorption, distribution, metabolism, and excretion profiles. Additionally, it provides a comprehensive overview of the utilization of TKIs in special populations such as the elderly, children, and patients with liver or kidney dysfunction. We also highlight known or suspected DDIs between TKIs and other drugs, highlighting various clinically relevant interactions. Moreover, specific recommendations are provided to guide haemato-oncologists, oncologists, and clinical pharmacists in managing DDIs during TKI treatment in daily clinical practice.

Induction of DNMT1-dependent demethylation of SHP-1 by the natural flavonoid compound Baicalein overcame Imatinib-resistance in CML CD34+ cells

BACKGROUND

The most significant cause of treatment failure in chronic myeloid leukemia (CML) is a persistent population of minimal residual cells. Emerging evidences showed that methylation of SHP-1 contributed to Imatinib (IM) resistance. Baicalein was reported to have an effect on reversal of chemotherapeutic agents resistance. However, the molecular mechanism of Baicalein on JAK2/STAT5 signaling inhibition against drug resistance in bone marrow (BM) microenvironment that had not been clearly revealed.

METHODS

We co-cultured hBMSCs and CML CD34⁺ cells as a model of SFM-DR. Further researches were performed to clarify the reverse mechanisms of Baicalein on SFM-DR model and engraftment model. The apoptosis, cytotoxicity, proliferation, GM-CSF secretion, JAK2/STAT5 activity, the expression of SHP-1 and DNMT1 were analyzed. To validate the role of SHP-1 on the reversal effect of Baicalein, the SHP-1 gene was over-expressed by pCMV6-entry shp-1 and silenced by SHP-1 shRNA, respectively. Meanwhile, the DNMT1 inhibitor decitabine was used. The methylation extent of SHP-1 was evaluated using MSP and BSP. The molecular docking was replenished to further explore the binding possibility of Baicalein and DNMT1.

RESULTS

BCR/ABL-independent activation of JAK2/STAT5 signaling was involved in IM resistance in CML CD34⁺ subpopulation. Baicalein significantly reversed BM microenvironment-induced IM resistance not through reducing GM-CSF secretion, but interfering DNMT1 expression and activity. Baicalein induced DNMT1-mediated demethylation of the SHP-1 promoter region, and subsequently activated SHP-1 re-expression, which resulted in an inhibition of JAK2/STAT5 signaling in resistant CML CD34⁺ cells. Molecular docking model indicated that DNMT1 and Baicalein had binding pockets in 3D structures, which further supported Baicalein might be a small-molecule inhibitor targeting DNMT1.

CONCLUSIONS

The mechanism of Baicalein on improving the sensitivity of CD34⁺ cells to IM might be correlated with SHP-1 demethylation by inhibition of DNMT1 expression. These findings suggested that Baicalein could be a promising candidate by targeting DNMT1 to eradicate minimal residual disease in CML patients. Video Abstract.

ACY-1215 suppresses the proliferation and induces apoptosis of chronic myeloid leukemia cells via the ROS/PTEN/Akt pathway

Chronic myeloid leukemia (CML) is a hematological tumor marked by the bcr-abl fusion gene formed by t (9;22) (q34; q11), which translated into the BCR-ABL protein. Tyrosine kinase inhibitors (TKIs) have been widely used to cure CML patients. Nevertheless, the emergence of TKI resistance has become the problem to the outcome of CML patients. Histone deacetylase 6 (HDAC6), a kind of Hsp90α deacetylase, was detected to be overexpressed in chronic myeloid leukemia stem cells. Besides, the loss of HDAC6 enzymatic activity can result in the degradation of Hsp90α's client proteins, such as BCR-ABL, the oncoprotein of CML. Here, we explored the expression of HDAC6 and discovered that it was upregulated compared with control in CML. Then we explored the effect of Rocilinostat (ACY-1215), a specific HDAC6 inhibitor, on CML cells. Our results proved that ACY-1215 could induce apoptosis and cell cycle arrest in a ROS-dependent manner. Moreover, we detected a downregulation of the BCR-ABL signaling pathway in the ACY-1215 treatment group. Mechanistically, we noted that the upregulation of PTEN was induced after being treated by ACY-1215 and its downstream protein p-Akt was decreased. The Akt activator SC79 can partially reverse the influence of ACY-1215 on CML cells. Besides, our results also proved that ACY-1215 can synergize with imatinib to suppress chronic myeloid leukemia in vitro and in vivo. On the whole, our study revealed that HDAC6 is a possible therapeutic target in CML, and the combination therapy of TKI and HDAC6 inhibitor may improve the outcome of CML patients.

Targeting DNMT1 by demethylating agent OR-2100 increases tyrosine kinase inhibitors-sensitivity and depletes leukemic stem cells in chronic myeloid leukemia

ABL1 tyrosine kinase inhibitors (TKIs) dramatically improve the prognosis of chronic myeloid leukemia (CML), but 10-20% of patients achieve suboptimal responses with low TKIs sensitivity. Furthermore, residual leukemic stem cells (LSCs) are involved in the molecular relapse after TKIs discontinuation. Aberrant DNA hypermethylation contributes to low TKIs sensitivity and the persistence of LSCs in CML. DNMT1 is a key regulator of hematopoietic stem cells, suggesting that aberrant DNA hypermethylation targeting DNMT1 represents a potential therapeutic target for CML. We investigated the efficacy of OR-2100 (OR21), the first orally available single-compound prodrug of decitabine. OR21 exhibited anti-tumor effects as a monotherapy, and in combination therapy it increased TKI-induced apoptosis and induction of tumor suppressor genes including PTPN6 encoding SHP-1 in CML cells. OR21 in combination with imatinib significantly suppressed tumor growth in a xenotransplant model. OR21 and combination therapy decreased the abundance of LSCs and inhibited engraftment in a BCR-ABL1-transduced mouse model. These results demonstrate that targeting DNMT1 using OR21 exerts anti-tumor effects and impairs LSCs in CML. Therefore, combination treatment of TKIs and OR21 represents a promising treatment strategy in CML.

A Review on the Therapeutic Role of TKIs in Case of CML in Combination With Epigenetic Drugs

Chronic myeloid leukemia is a malignancy of bone marrow that affects white blood cells. There is strong evidence that disease progression, treatment responses, and overall clinical outcomes of CML patients are influenced by the accumulation of other genetic and epigenetic abnormalities, rather than only the BCR/ABL1 oncoprotein. Both genetic and epigenetic factors influence the efficacy of CML treatment strategies. Targeted medicines known as tyrosine-kinase inhibitors have dramatically improved long-term survival rates in CML patients during the previous 2 decades. When compared to earlier chemotherapy treatments, these drugs have revolutionized CML treatment and allowed most people to live longer lives. Although epigenetic inhibitors' activity is disrupted in many cancers, including CML, but when combined with TKI, they may offer potential therapeutic strategies for the treatment of CML cells. The epigenetics of tyrosine kinase inhibitors and resistance to them is being studied, with a particular focus on imatinib, which is used to treat CML. In addition, the use of epigenetic drugs in conjunction with TKIs has been discussed. Resistance to TKIs is still a problem in curing the disease, necessitating the development of new therapies. This study focused on epigenetic pathways involved in CML pathogenesis and tumor cell resistance to TKIs, both of which contribute to leukemic clone breakout and proliferation.

DNA Methylation and Intra-Clonal Heterogeneity: The Chronic Myeloid Leukemia Model

Chronic Myeloid Leukemia (CML) is a model to investigate the impact of tumor intra-clonal heterogeneity in personalized medicine. Indeed, tyrosine kinase inhibitors (TKIs) target the BCR-ABL fusion protein, which is considered the major CML driver. TKI use has highlighted the existence of intra-clonal heterogeneity, as indicated by the persistence of a minority subclone for several years despite the presence of the target fusion protein in all cells. Epigenetic modifications could partly explain this heterogeneity. This review summarizes the results of DNA methylation studies in CML. Next-generation sequencing technologies allowed for moving from single-gene to genome-wide analyses showing that methylation abnormalities are much more widespread in CML cells. These data showed that global hypomethylation is associated with hypermethylation of specific sites already at diagnosis in the early phase of CML. The BCR-ABL-independence of some methylation profile alterations and the recent demonstration of the initial intra-clonal DNA methylation heterogeneity suggests that some DNA methylation alterations may be biomarkers of TKI sensitivity/resistance and of disease progression risk. These results also open perspectives for understanding the epigenetic/genetic background of CML predisposition and for developing new therapeutic strategies.

ND‑09 inhibits chronic myeloid leukemia K562 cell growth by regulating BCR‑ABL signaling

Chronic myeloid leukemia (CML) accounts for approximately 15% of new adult leukemia cases. The fusion gene BCR‑ABL is an important biological basis and target for CML. In the present study, a novel compound, ND‑09, was developed and its inhibitory effect and mechanism of action on CML growth were evaluated using RT‑PCR and western blot analysis. The results showed that ND‑09 demonstrated a high level of inhibitory action toward CML cells overexpressing BCR‑ABL and induced K562 cell apoptosis through the mitochondrial pathway. Notably, combined ND‑09 and BCR‑ABL siRNA treatment could better inhibit cell proliferation and induce apoptosis in K562 cells. Furthermore, this growth effect of BCR‑ABL siRNA could be fully rescued by transfection with BCR‑ABL. ND‑09 exhibited a good fit within BCR‑ABL and occupied its ATP‑binding pocket, thus altering BCR‑ABL kinase activity. Therefore, ND‑09 downregulated the phosphorylation of BCR‑ABL and ABL, ultimately inhibiting the downstream signaling pathways in K562 cells. These findings suggest that ND‑09 induces growth arrest in CML cells by targeting BCR‑ABL.

CNS Involvement in a Patient with Chronic Myeloid Leukemia

Inspite of medication compliance, some chronic myeloid leukemia (CML) patients will relapse/progress into an accelerated phase or blast crisis. Central nervous system (CNS) involvement is a rare manifestation of such a relapse. Here, we report a case of 23-year-old female who was diagnosed with CML in the accelerated phase and subsequently treated with imatinib. She developed early relapse in her CNS, and her treatment was switched to dasatinib and intrathecal chemotherapy with cytarabine and methotrexate. Her CNS disease went into remission, and she underwent matched unrelated donor (MUD) hematopoietic stem cell transplant (HSCT). We discuss various mechanisms of treatment failure, importance of vigilance for symptoms and signs of treatment failure/relapse, indications for use of different tyrosine kinase inhibitors (TKIs), and management of blast crises in CML.

Abrogation of histone deacetylases (HDACs) decreases survival of chronic myeloid leukemia cells: New insight into attenuating effects of the PI3K/c-Myc axis on panobinostat cytotoxicity

Although the identification of tyrosine kinase inhibitors (TKIs) has changed the treatment paradigm of many cancer types including chronic myeloid leukemia (CML), still adjustment of neoplastic cells to cytotoxic effects of anticancer drugs is a serious challenge. In the area of drug resistance, epigenetic alterations are at the center of attention and the present study aimed to evaluate whether blockage of epigenetics mechanisms using a pan-histone deacetylase (HDAC) inhibitor induces cell death in CML-derived K562 cells. We found that the abrogation of HDACs using panobinostat resulted in a reduction in survival of the K562 cell line through p27-mediated cell cycle arrest. Noteworthy, the results of the synergistic experiments revealed that HDAC suppression could be recruited as a way to potentiate cytotoxicity of Imatinib and to enhance the therapeutic efficacy of CML. Here, we proposed for the first time that the inhibitory effect of panobinostat was overshadowed, at least partially, through the aberrant activation of the phosphoinositide 3-kinase (PI3K)/c-Myc axis. Meanwhile, we found that upon blockage of autophagy and the proteasome pathway, as the main axis involved in the activation of autophagy, the anti-leukemic property of the HDAC inhibitor was potentiated. Taken together, our study suggests the beneficial application of HDAC inhibition in the treatment strategies of CML; however, further in vivo studies are needed to determine the efficacy of this inhibitor, either as a single agent or in combination with small molecule inhibitors of PI3K and/or c-Myc in this malignancy.

Análise de mutações do domínio BCR-ABL quinase em pacientes com leucemia mielóide crônica refratários ao tratamento com mesilato de imatinibe

Objetivo: A Leucemia Mielóide Crônica (LMC) é um distúrbio clonal de células progenitoras hematopoiéticas, caracterizada por uma translocação recíproca entre os cromossomos 9 e 22, que resulta no gene híbrido BCR-ABL1.Mesmo com o progresso no tratamento da doença permitido pelos inibidores de tirosina quinase, mutações pontuais no domínio desse gene são as principais causas de resistência terapêutica, principalmente ao mesilato de imatinibe. O objetivo desse estudo foi analisar as mutações pontuais de alta resistência em paciente com LMC e sua possível correlação com a resposta ao tratamento. Métodos: Estudo transversal com 58 pacientes com LMC em tratamento com imatinibe e com resposta subótima à terapia. As amostras de sangue foram analisadas por PCR em tempo real usando a química TaqMan® para avaliar as seguintes mutações pontuais: T315I, E255V e Y253H. Resultados: Nenhum dos 58 pacientes apresentou alguma das mutações investigadas. Houve uso irregular da medicação em 16% (n = 9), dos quais 44% (n = 4) relataram uso descontínuo e interrupção por conta própria, e 56% (n = 5) apresentaram intolerância ao tratamento e trocaram de fármaco. Conclusão: A ausência das mutações pontuais nos pacientes portadores de LMC analisados neste estudo demonstrou que a falha na terapia não tem correlação molecular com as mutações analisadas e pode estar relacionada à menores taxas de adesão ao tratamento. Estes achados foram demonstrados em um número considerável de pacientes avaliados, apontando a necessidade da edução sobre a importância de seguir as recomendações sobre seu tratamento para evitar complicações futuras.

Regulating Methylation at H3K27: A Trick or Treat for Cancer Cell Plasticity

Properly timed addition and removal of histone 3 lysine 27 tri-methylation (H3K27me3) is critical for enabling proper differentiation throughout all stages of development and, likewise, can guide carcinoma cells into altered differentiation states which correspond to poor prognoses and treatment evasion. In early embryonic stages, H3K27me3 is invoked to silence genes and restrict cell fate. Not surprisingly, mutation or altered functionality in the enzymes that regulate this pathway results in aberrant methylation or demethylation that can lead to malignancy. Likewise, changes in expression or activity of these enzymes impact cellular plasticity, metastasis, and treatment evasion. This review focuses on current knowledge regarding methylation and de-methylation of H3K27 in cancer initiation and cancer cell plasticity.

Histone lysine demethylase KDM5B maintains chronic myeloid leukemia via multiple epigenetic actions

The histone lysine demethylase KDM5 family is implicated in normal development and stem cell maintenance by epigenetic modulation of histone methylation status. Deregulation of the KDM5 family has been reported in various types of cancers, including hematological malignancies. However, their transcriptional regulatory roles in the context of leukemia remain unclear. Here, we find that KDM5B is strongly expressed in normal CD34⁺ hematopoietic stem/progenitor cells and chronic myeloid leukemia (CML) cells. Knockdown of KDM5B in K562 CML cells reduced leukemia colony-forming potential. Transcriptome profiling of KDM5B knockdown K562 cells revealed the deregulation of genes involved in myeloid differentiation and Toll-like receptor signaling. Through the integration of transcriptome and ChIP-seq profiling data, we show that KDM5B is enriched at the binding sites of the GATA and AP-1 transcription factor families, suggesting their collaborations in the regulation of transcription. Even though the binding of KDM5B substantially overlapped with H3K4me1 or H3K4me3 mark at gene promoters, only a small subset of the KDM5B targets showed differential expression in association with the histone demethylation activity. By characterizing the interacting proteins in K562 cells, we discovered that KDM5B recruits protein complexes involved in the mRNA processing machinery, implying an alternative epigenetic action mediated by KDM5B in gene regulation. Our study highlights the oncogenic functions of KDM5B in CML cells and suggests that KDM5B is vital to the transcriptional regulation via multiple epigenetic mechanisms.