Article

Knocking-Down Cyclin A2 by siRNA Suppresses Apoptosis and Switches Differentiation Pathways in K562 Cells upon Administration with Doxorubicin

Cairo University, Egypt
PLoS ONE (Impact Factor: 3.53). 02/2009; 4(8):e6665. DOI: 10.1371/journal.pone.0006665
Source: PubMed

ABSTRACT Cyclin A(2) is critical for the initiation of DNA replication, transcription and cell cycle regulation. Cumulative evidences indicate that the deregulation of cyclin A(2) is tightly linked to the chromosomal instability, neoplastic transformation and tumor proliferation. Here we report that treatment of chronic myelogenous leukaemia K562 cells with doxorubicin results in an accumulation of cyclin A(2) and follows by induction of apoptotic cell death. To investigate the potential preclinical relevance, K562 cells were transiently transfected with the siRNA targeting cyclin A(2) by functionalized single wall carbon nanotubes. Knocking down the expression of cyclin A(2) in K562 cells suppressed doxorubicin-induced growth arrest and cell apoptosis. Upon administration with doxorubicin, K562 cells with reduced cyclin A(2) showed a significant decrease in erythroid differentiation, and a small fraction of cells were differentiated along megakaryocytic and monocyte-macrophage pathways. The results demonstrate the pro-apoptotic role of cyclin A(2) and suggest that cyclin A(2) is a key regulator of cell differentiation. To the best of our knowledge, this is the first report that knocking down expression of one gene switches differentiation pathways of human myeloid leukemia K562 cells.

0 Followers
 · 
105 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Leukemias arise from genetic alterations in normal hematopoietic stem or progenitor cells, leading to impaired regulation of proliferation, differentiation, apoptosis, and survival of the transformed cells. With the advent of RNA interference (RNAi) and the short interfering RNA (siRNA) as its pharmacological mediator, it is becoming possible to modulate specific targets at will. This article summarizes current attempts to utilize RNAi reagents for therapy of leukemias, focusing on acute and chronic myeloid leukemia. We first present unique aspects of RNAi-mediated therapy, followed by a brief background on the delivery technology of RNAi reagents. The need for leukemia-specific delivery of siRNA is discussed by describing approaches that targeted agents to leukemic cells. Pharmacokinetics and biodistribution of RNAi agents are then presented, highlighting the critical issues pertinent to emerging siRNA therapy. Efforts to deliver specific RNAi therapies are then summarized in the context of expected clinical outcomes, focusing on limiting leukemic cell survival, sensitizing malignant cells to chemotherapy, mobilization of leukemic cells, and eradication of leukemic stem cells. We conclude with a perspective on the future of RNAi therapy, emphasizing the technological requirements and mechanistic challenges for clinical entry.
    05/2015; 4(5):e240. DOI:10.1038/mtna.2015.13
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sonodynamic therapy (SDT) with 5‑aminolevulinic acid (5‑ALA) can effectively inhibit various types of tumor in vitro and in vivo. However, the association between the efficacy of SDT and the phase of the cell cycle remains to be elucidated. 5‑ALA may generate different quantities of sonosensitizer, protoporphyrin IX (PpIX), in different phases of the cell cycle, which may result in differences in sensitivity to 5‑ALA‑induced SDT. The present study aimed to investigate the effect of the cell cycle on the susceptibility of SAS cells to SDT following synchronization to different cell cycle phases. These results indicates that the rates of cell death and apoptosis of the SAS cells in the S and G2/M phases were significantly higher following SDT, compared with those in the G1‑phase cells and unsynchronized cells, with a corresponding increase in PpIX in the S and G2/M cells. In addition, the expression of caspase‑3 increased, while that of B‑cell lymphoma (Bcl)‑2 decreased markedly in theS and G2/M cells following SDT. Cyclin A was also expressed at higher levels in the S and G2/M cells, compared with the G1‑phase cells. SDT also caused a significant upregulation of cyclin A in all phases of the cell cycle, however this was most marked in the S and G2/M cells. It was hypothesized that high expression levels of cyclin A in the S and G2/M cells may promote the induction of caspase‑3 and reduce the induction of Bcl‑2 by SDT and, therefore, enhance apoptosis. Taken together, these data demonstrated that cells in The S and G2/M phases generate more intracellular PpIX, have higher levels of cyclin A and are, therefore, more sensitive to SDT‑induced cytotoxicity. These findings indicate the potential novel approach to preventing the onset of cancer by combining cell‑cycle regulators with SDT. This sequential combination therapy may be a simple and cost‑effective way of enhancing the effects of SDT in clinical settings.
    Molecular Medicine Reports 05/2015; DOI:10.3892/mmr.2015.3747 · 1.48 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mir-29 microRNA families are involved in regulation of various types of cancers. Although Mir-29 was shown to play an inhibitory role in tumorigenesis, the role of Mir-29 in breast cancer still remains obscure. In this study, we showed that Mir-29a is the dominant isoform in its family in mammary cells and expression of Mir-29a was down-regulated in different types of breast cancers. Furthermore, over-expression of Mir-29a resulted in significant slower growth of breast cancer cells and caused higher percentage of cells at G0/G1 phase. Consistent with this over-expression data, knockdown of Mir-29a in normal mammary cells lead to higher cell growth rate, and higher percentage of cells entering S phase. We further found that Mir-29a negatively regulated expression of B-Myb, which is a transcription factor associated with tumorigenesis. The protein levels of Cyclin A2 and D1 are consistent with the protein level of B-Myb. Taken together, our data suggests Mir-29a plays an important role in inhibiting growth of breast cancer cells and arresting cells at G0/G1 phase. Our data also suggests that Mir-29a may suppress tumor growth through down-regulating B-Myb.
    Journal of Experimental & Clinical Cancer Research 12/2013; 32(1):98. DOI:10.1186/1756-9966-32-98 · 3.27 Impact Factor