Abstract
Arsenic trioxide (ATO) is a well-known carcinogen but also an effective cancer therapeutic drug for acute promyelocytic leukemia. Despite intensive research efforts, the molecular mechanisms underlying antileukemic effect of ATO as well as resistance to arsenic therapy appearing during treatment are not well understood. There are data showing that dysregulation of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway, a central integrating point of survival signals, may be the reason of apoptosis resistance in leukemic cells.
The aim of the present study was to assess expression of 84 genes involved in PI3K/Akt signaling pathway in Jurkat cells exposed to ATO at 1, 2.5 and 5 μM for 16 hrs as well as in ATO resistant clones derived from the cells. First screening of genes was performed using the Human PI3K-AKT Signaling Pathway RT2 ProfilerTM PCR Array (Superarray) and then selected genes were verified in a standard real-time PCR.
Results of our study showed that ATO induced more intensive changes in expression of PI3K/Akt pathway genes in ATO resistant clones than in Jurkat cells exposed to arsenic. Among genes differently regulated in both cell types were these playing a key role in regulating cell growth e.g. GRB10 (growth factor receptor-bound protein 10), FASLG (Fas ligand), CCND1 (cyclin D1). Interestingly, the level of FASLG mRNA was strongly down-regulated in ATO treated Jurkat cells and up-regulated in ATO resistant clones. Expression of CCND1 and GRB10 varied between resistant clones in a concentration-dependent manner. Moreover, concentration-dependent up-regulation of JUN (jun oncogene) was the most characteristic effect induced by ATO in Jurkat cells. Comparing to untreated Jurkat cells, we identified several genes differently regulated in ATO resistant clones (but not in Jurkat ATO exposed cells) that were mainly involved in anti-apoptotic pathways (e.g. IRS1 (Insulin receptor substrate 1), MAP2K1 (Mitogen-activated protein kinase kinase 1), MAPK3 (Mitogen-activated protein kinase 3), RPS6KA1 (Ribosomal protein S6 kinase, 90kDa, polypeptide 1), PRKCB (Protein kinase C, beta 1), PRKCZ (Protein kinase C, zeta) or Akt activation and growth regulation (e.g. PDK1 (Pyruvate dehydrogenase kinase, isozyme 1), MTOR (Mechanistic target of rapamycin), MTCP1 (Mature T-cell proliferation 1)).
In conclusion, our in vitro study identified several targets of ATO that may mediate cytotoxic effects in Jurkat cells. Moreover, the data suggest that the PI3K/Akt signaling pathway plays an important role in the ATO resistance in Jurkat leukemic cells. The work was supported by the Polish State Committee for Scientific Research (grant No PB 2806/B/PO1/2007/33).
Citation Information: Clin Cancer Res 2010;16(7 Suppl):B16
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