PU.1 affects proliferation of the human acute myeloid leukemia U937 cell line by directly regulating MEIS1

Circular RNAs: pivotal role in the leukemogenesis and novel indicators for the diagnosis and prognosis of acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy and affected patients have poor overall survival (OS) rates. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) with a unique loop structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been identified exhibiting either up-regulation or down-regulation in AML patients compared with healthy controls. Recent studies have reported that circRNAs regulate leukemia cell proliferation, stemness, and apoptosis, both positively and negatively. Additionally, circRNAs could be promising biomarkers and therapeutic targets in AML. In this study, we present a comprehensive review of the regulatory roles and potentials of a number of dysregulated circRNAs in AML.

Deregulation of the HOXA9/MEIS1 axis in acute leukemia

PURPOSE OF REVIEW

HOXA9 is a homeodomain transcription factor that plays an essential role in normal hematopoiesis and acute leukemia, in which its overexpression is strongly correlated with poor prognosis. The present review highlights recent advances in the understanding of genetic alterations leading to deregulation of HOXA9 and the downstream mechanisms of HOXA9-mediated transformation.

RECENT FINDINGS

A variety of genetic alterations including MLL translocations, NUP98-fusions, NPM1 mutations, CDX deregulation, and MOZ-fusions lead to high-level HOXA9 expression in acute leukemias. The mechanisms resulting in HOXA9 overexpression are beginning to be defined and represent attractive therapeutic targets. Small molecules targeting MLL-fusion protein complex members, such as DOT1L and menin, have shown promising results in animal models, and a DOT1L inhibitor is currently being tested in clinical trials. Essential HOXA9 cofactors and collaborators are also being identified, including transcription factors PU.1 and C/EBPα, which are required for HOXA9-driven leukemia. HOXA9 targets including IGF1, CDX4, INK4A/INK4B/ARF, mir-21, and mir-196b and many others provide another avenue for potential drug development.

SUMMARY

HOXA9 deregulation underlies a large subset of aggressive acute leukemias. Understanding the mechanisms regulating the expression and activity of HOXA9, along with its critical downstream targets, shows promise for the development of more selective and effective leukemia therapies.

High expression of PU.1 is associated with Her-2 and shorter survival in patients with breast cancer

The transcription factor PU.1 was previously identified as an oncogene or a tumor suppressor in different types of leukemia. The aim of the present study was to investigate the expression of PU.1 in breast cancer and to analyze its association with clinical features and prognosis. Immunohistochemistry was used to determine PU.1 expression in breast cancer tissue microarrays and paraffin-embedded sections. The association between PU.1 expression and clinicopathological factors was assessed by using chi-square test. The survival analysis of patients was conducted by using Kaplan-Meier analysis and log-rank tests. Cox regression was utilized for univariate and multivariate analyses of prognostic factors. The results indicated that the expression level of PU.1 protein in breast cancer samples was significantly higher compared with normal breast tissues (P=2.63×10^-8). Furthermore, the level of PU.1 expression was detected to be positively associated with androgen receptor (P=0.027) and human epidermal growth factor receptor 2 status (P=2.03×10^-21) as well as molecular subtype (P=3.51×10^-11). Furthermore, patients with negative PU.1 expression had longer OR compared with those with positive PU.1 expression (P=3.67×10^-4). Multivariate Cox regression analysis revealed that PU.1 expression level and tumor-node-metastasis stage were independent prognostic factors for overall survival (P=0.034 and P=0.018, respectively). Therefore, PU.1 protein expression may contribute to breast cancer progression and may be a valuable molecular marker to predict the prognosis of patients with breast cancer.

Hsp90 inhibitor induces KG-1a cell differentiation and apoptosis via Akt/NF-κB signaling

Heat-shock protein 90 (Hsp 90) acts as a molecular chaperone that maintains protein stability and regulates cell proliferation, survival, differentiation and apoptosis. The present study investigated the effect of Hsp90 inhibition on human acute myeloid leukemia (AML) cells using the novel small-molecule inhibitor SNX-2112. We found that SNX-2112 more potently inhibited KG-1a cell growth than the classical Hsp90 inhibitor 17-(2-dimethylaminoethyl)amino‑17-demethoxygeldanamycin as determined by CCK-8 assay. Flow cytometry was used to examine the cell cycle, differentiation, and apoptosis, and western blotting and qRT-PCR were used to analyze the underlying mechanism. The results revealed that low concentrations of SNX-2112 arrested the cells in the G2/M phase and induced their differentiation and apoptosis, possibly by suppressing Akt and inhibitor of κB kinase, a component of the nuclear factor (NF)-κB signaling pathway. We also found that SNX-2112 increased the expression of the differentiation transcription factors PU.1 and CCAAT‑enhancer-binding protein-α. Thus, SNX-2112 induced KG-1a cell differentiation, cell cycle arrest and apoptosis via modulation of Akt and NF-κB signaling, suggesting that it is a promising therapeutic agent for the treatment of AML.