Bortezomib induces apoptosis by interacting with JAK/STAT pathway in K562 leukemic cells

Leucine-Rich Alpha-2-Glycoprotein1 Gene Interferes with Regulation of Apoptosis in Leukemia KASUMI-1 Cells

Background

Leukemia cells have strong proliferation and anti-apoptosis capabilities. The purpose of this study was to investigate the effect of silencing the leucine-rich alpha-2-glycoprotein1 (LRG1) gene, which was found to regulate tumor proliferation and apoptosis in acute myeloid leukemia (AML) cell lines.

Material/Methods

Plasmid interference technique was used to silence the LRG1 gene in the KASUMI-1 cell line. The cell counting kit-8 (CCK-8) assay was used to test the effect of transduction on cell viability. Cell cycle and apoptosis were detected by flow cytometry. Western blot and quantitative real-time polymerase chain reaction (RT-qPCR) were applied to detect the expression levels of proteins and mRNA, respectively.

Results

KASUMI-1 cells with the CD34⁺CD38⁻ phenotype were sorted by flow cytometry. After transfection of the siLRG1 plasmid, the level of LRG1 expression was downregulated and cell viability was reduced. Silencing of LRG1 gene blocked KASUMI-1 cells in G0/G1 phase and promoted apoptosis. Further experiments found that LRG1 gene silencing significantly downregulated cell cycle-associated proteins and anti-apoptotic proteins, while upregulating pro-apoptotic proteins. Downregulation of LRG1 gene expression also inhibits signal transduction of the JAK-STAT pathway.

Conclusions

LRG1 gene silencing regulates the expression of cyclin and apoptosis-related proteins to reduce cell viability and promote apoptosis, probably through inhibition of the JAK-STAT pathway.

Overexpression of miR-574-3p suppresses proliferation and induces apoptosis of chronic myeloid leukemia cells via targeting IL6/JAK/STAT3 pathway

The present study aimed to elucidate the potential roles and regulatory mechanism of microRNA (miR)-574-3p in the development of chronic myeloid leukemia (CML). The expression of miR-574-3p in peripheral blood obtained from patients with CML was examined. Subsequently, miR-574-3p was overexpressed and suppressed in CML K562 cells to further investigate the effects of miR-574-3p on cell proliferation, and apoptosis. Furthermore, a luciferase reporter assay was performed to investigate whether interleukin-6 (IL-6) was a target of miR-574-3p. In addition, the regulatory association between miR-574-3p and the IL-6/Janus kinase (JNK)/signal transducer and activator of transcription-3 (STAT3) signaling pathway was explored. The expression of miR-574-3p in the peripheral blood obtained from patients with CML was significantly lower compared with that in healthy controls. Overexpression of miR-574-3p significantly inhibited the proliferation and induced the apoptosis of K562 cells, whereas suppression of miR-574-3p exhibited opposite effects. In addition, IL-6 was identified to be a direct target of miR-574-3p. Overexpression of IL-6 significantly promoted the proliferation and inhibited the apoptosis of K562 cells. Furthermore, overexpression of miR-574-3p inhibited the activation of the JAK/STAT3 signaling pathway, which was rescued by overexpression of IL-6. The results of the current study indicate that miR-574-3p overexpression may serve an important role in inhibiting proliferation and inducing apoptosis of K562 cells via suppression of IL-6/JAK/STAT3 signaling pathway activation. miR-574-3p may serve as a potential therapeutic target for CML.

Roles of STAT3 in leukemia (Review)

Leukemia is a type of hematopoietic malignancy, and the incidence rate in the United States and European Union increases by an average of 0.6 to 0.7% annually. The incidence rate in China is approximately 5.17/100,000 individuals, and the mortality rate is 3.94/100,000 individuals. Leukemia is the most common tumor affecting children and adults under 35 years of age, and is one of the major diseases leading to the death of adolescents. Signal transducer and activator of transcription 3 (STAT3) is a vital regulatory factor of signal transduction and transcriptional activation, and once activated, the phosphorylated form of STAT3 (p-STAT3) is transferred into the nucleus to regulate the transcription of target genes, and plays important roles in cell proliferation, differentiation, apoptosis and other physiological processes. An increasing number of studies have confirmed that the abnormal activation of STAT3 is involved in the development of tumors. In this review, the roles of STAT3 in the pathogenesis, diagnosis, treatment and prognosis of leukemia are discussed in the aspects of cell proliferation, differentiation and apoptosis, with the aim to further clarify the roles of STAT3 in leukemia, and shed light into possible novel targets and strategies for clinical diagnosis and treatment.

Antiproliferative and proapoptotic effects of a pyrrole containing arylthioindole in human Jurkat leukemia cell line and multidrug-resistant Jurkat/A4 cells

Recently, a series of novel arylthioindole compounds, potent inhibitors of tubulin polymerization and cancer cell growth, were synthesized. In the present study the effects of 2-(1H-pyrrol-3-yl)-3-((3,4,5-trimethoxyphenyl)thio)-1H-indole (ATI5 compound) on cell proliferation, cell cycle progression, and induction of apoptosis in human T-cell acute leukemia Jurkat cells and their multidrug resistant Jurkat/A4 subline were investigated. Treatment of the Jurkat cells with the ATI5 compound for 48 hrs resulted in a strong G2/M cell cycle arrest and p53-independent apoptotic cell death accompanied by the induction of the active form of caspase-3 and poly(ADP-ribose) polymerase-1 (PARP-1) cleavage. ATI5 treatment also caused non-cell death related mitotic arrest in multidrug resistant Jurkat/A4 cells after 48 hrs of treatment suggesting promising opportunities for the further design of pyrrole-containing ATI compounds as anticancer agents. Cell death resistance of Jurkat/A4 cells to ATI5 compound was associated with alterations in the expression of pro-survival and anti-apoptotic protein-coding and microRNA genes. More importantly, findings showing that ATI5 treatment induced p53-independent apoptosis are of great importance from a therapeutic point of view since p53 mutations are common genetic alterations in human neoplasms.

Down-regulation of superoxide dismutase 1 by PMA is involved in cell fate determination and mediated via protein kinase D2 in myeloid leukemia cells

Myeloid leukemia cells maintain a high intracellular ROS level and use redox signals for survival. The metabolism of ROS also affects cell fate, including cell death and differentiation. Superoxide dismutases (SODs) are major antioxidant enzymes that have high levels of expression in myeloid leukemia cells. However, the role of SODs in the regulation of myeloid leukemia cells' biological function is still unclear. To investigate the function of SODs in myeloid leukemia cell death and differentiation, we used myeloid leukemia cell lines K562, MEG-01, TF-1, and HEL cells for this study. We found that PMA-induced megakaryocytic differentiation in myeloid leukemia cells is accompanied by cell death and SOD1 down-regulation, while SOD2 expression is not affected. The role of SOD1 is verified when ATN-224, a SOD1 specific inhibitor, inhibits cell proliferation and promotes cell death in myeloid leukemia cells without PMA treatment. Moreover, inhibition or silencing of SODs further increases cell death and decreases polyploidization induced by PMA while they were partially reversed by SOD1 overexpression. Thus, SOD1 expression is required for myeloid leukemia cell fate determination. In addition, the knockdown of PKD2 reduces cell death and promotes polyploidization induced by PMA. PMA/PKD2-mediated necrosis via PARP cleavage involves both SOD1-dependent and -independent pathways. Finally, ATN-224 enhanced the inhibition of cell proliferation by Ara-C. Taken together, the results demonstrate that SOD1 regulates cell death and differentiation in myeloid leukemia cells. ATN-224 may be beneficial for myeloid leukemia therapy.