Analysis of microRNA and gene networks in human chronic myelogenous leukemia

Aberrantly reduced expression of miR-342-5p contributes to CCND1-associated chronic myeloid leukemia progression and imatinib resistance

Chronic myeloid leukemia (CML) is a myeloproliferative disorder associated with the Philadelphia chromosome, and the current standard of care is the use of tyrosine kinase inhibitors (TKI). However, some patients will not achieve a molecular response and may progress to blast crisis, and the underlying mechanisms remain to be clarified. In this study, next-generation sequencing was used to explore endogenous miRNAs in CML patients versus healthy volunteers, and miR-342-5p was identified as the primary target. We found that miR-342-5p was downregulated in CML patients and had a significant inhibitory effect on cell proliferation in CML. Through a luciferase reporter system, miR-342-5p was reported to target the 3'-UTR domain of CCND1 and downregulated its expression. Furthermore, overexpression of miR-342-5p enhanced imatinib-induced DNA double-strand breaks and apoptosis. Finally, by analyzing clinical databases, we further confirmed that miR-342-5p was associated with predicted molecular responses in CML patients. In conclusion, we found that both in vivo and in vitro experiments and database cohorts showed that miR-342-5p plays a key role in CML patients, indicating that miR-342-5p may be a potential target for future CML treatment or prognostic evaluation.

Comparison of microRNA Expression Profile in Chronic Myeloid Leukemia Patients Newly Diagnosed and Treated by Allogeneic Hematopoietic Stem Cell Transplantation

Chronic myeloid leukemia (CML) results from a translocation between chromosomes 9 and 22, which generates the Philadelphia chromosome. This forms BCR/ABL1, an active tyrosine kinase protein that promotes cell growth and replication. Despite great progress in CML treatment in the form of tyrosine kinase inhibitors, allogeneic-hematopoietic stem cell transplantation (allo-HSCT) is currently used as an important treatment alternative for patients resistant to these inhibitors. Studies have shown that unregulated expression of microRNAs, which act as oncogenes or tumor suppressors, is associated with human cancers. This contributes to tumor formation and development by stimulating proliferation, angiogenesis, and invasion. Research has demonstrated the potential of microRNAs as biomarkers for cancer diagnosis, prognosis, and therapeutic targets. In the present study, we compared the circulating microRNA expression profiles of 14 newly diagnosed patients with chronic phase-CML and 14 Philadelphia chromosome-negative patients after allo-HSCT. For each patient, we tested 758 microRNAs by reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis. The global expression profile of microRNAs revealed 16 upregulated and 30 downregulated microRNAs. Target genes were analyzed, and key pathways were extracted and compared. Bioinformatics tools were used to analyze data. Among the downregulated miRNA target genes, some genes related to cell proliferation pathways were identified. These results reveal the comprehensive microRNA profile of CML patients and the main pathways related to the target genes of these miRNAs in cytogenetic remission after allo-HSCT. These results provide new resources for exploring stem cell transplantation-based CML treatment strategies.

Strategies For Targeting Chronic Myeloid Leukaemia Stem Cells

Chronic Myeloid Leukaemia is a myeloproliferative disorder driven by the t(9;22) chromosomal translocation coding for the chimeric protein BCR-ABL. CML treatment represents the paradigm of molecular therapy of cancer. Since the development of the tyrosine kinase inhibitor of the BCR-ABL kinase, the clinical approach to CML has dramatically changed, with a stunning improvement in the quality of life and response rates of patients. However, it remains clear that tyrosine kinase inhibitors (TKIs) are unable to target the most immature cellular component of CML, the CML stem cell. This review summarizes new insights into the mechanisms of resistance to TKIs.

The downregulation of putative anticancer target BORIS/CTCFL in an addicted myeloid cancer cell line modulates the expression of multiple protein coding and ncRNA genes

The BORIS/CTCFL gene, is a testis-specific CTCF paralog frequently erroneously activated in cancer, although its exact role in cancer remains unclear. BORIS is both a transcription factor and an architectural chromatin protein. BORIS' normal role is to establish a germline-like gene expression and remodel the epigenetic landscape in testis; it similarly remodels chromatin when activated in human cancer. Critically, at least one cancer cell line, K562, is dependent on BORIS for its self-renewal and survival. Here, we downregulate BORIS expression in the K562 cancer cell line to investigate downstream pathways regulated by BORIS. RNA-seq analyses of both mRNA and small ncRNAs, including miRNA and piRNA, in the knock-down cells revealed a set of differentially expressed genes and pathways, including both testis-specific and general proliferation factors, as well as proteins involved in transcription regulation and cell physiology. The differentially expressed genes included important transcriptional regulators such as SOX6 and LIN28A. Data indicate that both direct binding of BORIS to promoter regions and locus-control activity via long-distance chromatin domain regulation are involved. The sum of findings suggests that BORIS activation in leukemia does not just recapitulate the germline, but creates a unique regulatory network.

Epigenetic dysregulation in chronic myeloid leukaemia: A myriad of mechanisms and therapeutic options

The onset of global epigenetic changes in chromatin that drive tumor proliferation and heterogeneity is a hallmark of many forms of cancer. Identifying the epigenetic mechanisms that govern these changes and developing therapeutic approaches to modulate them, is a well-established avenue pursued in translational cancer medicine. Chronic myeloid leukemia (CML) arises clonally when a hematopoietic stem cell (HSC) acquires the capacity to produce the constitutively active tyrosine kinase BCR-ABL1 fusion protein which drives tumor development. Treatment with tyrosine kinase inhibitors (TKI) that target BCR-ABL1 has been transformative in CML management but it does not lead to cure in the vast majority of patients. Thus novel therapeutic approaches are required and these must target changes to biological pathways that are aberrant in CML - including those that occur when epigenetic mechanisms are altered. These changes may be due to alterations in DNA or histones, their biochemical modifications and requisite 'writer' proteins, or to dysregulation of various types of non-coding RNAs that collectively function as modulators of transcriptional control and DNA integrity. Here, we review the evidence for subverted epigenetic mechanisms in CML and how these impact on a diverse set of biological pathways, on disease progression, prognosis and drug resistance. We will also discuss recent progress towards developing epigenetic therapies that show promise to improve CML patient care and may lead to improved cure rates.

Mechanical stretch regulates microRNA expression profile via NF-κB activation in C2C12 myoblasts

MicroRNAs (miRNAs/miRs) and nuclear factor (NF)-κB activation are involved in mechanical stretch-induced skeletal muscle regeneration. However, there are a small number of miRNAs that have been reported to be associated with NF‑κB activation during mechanical stretch-induced myogenesis. In the present study, C2C12 myoblasts underwent cyclic mechanical stretch in vitro, to explore the relationship between miRNA expression and NF‑κB activation during stretch-mediated myoblast proliferation. The results revealed that 10% deformation, 0.125 Hz cyclic mechanical stretch could promote myoblast proliferation. The miRNA expression profile was subsequently altered; miR‑500, ‑1934, ‑31, ‑378, ‑331 and ‑5097 were downregulated, whereas miR‑1941 was upregulated. These miRNAs were all involved in stretch‑mediated myoblast proliferation. Notably, the expression of these miRNAs was reversed following treatment of 0.125 Hz mechanically stretched C2C12 cells with NF‑κB inhibitors, which was accompanied by C2C12 cell growth suppression. Therefore, the present study is the first, to the best of our knowledge, to demonstrate that the NF‑κB‑dependent miRNA profile is associated with mechanical stretch-induced myoblast proliferation.