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  • 1
    ISSN: 1432-0843
    Keywords: Key words SN-38 ; CPT-11 ; Camptothecin ; Radiation ; p53
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: Topoisomerase inhibitors including camptothecin are being studied as potential radiosensitizers. CPT-11 is a derivative of camptothecin and is clinically available. In this study, we investigated the effects of SN-38 (an active metabolite of CPT-11) on four nonirradiated and irradiated murine fibroblast cell lines with different p53 statuses to clarify the role of p53 in the radiosensitizing activity of SN-38. Materials and methods: Four fibroblast cell lines, MT158, MT158/neo, MT158/wtp53 and MT158/mp53 with the same genetic background but with different p53 statuses, were used. Exponentially growing cells were treated with SN-38 (200 nM) and incubated with the drug for 30 min. Cells were then irradiated (0 to 12 Gy) and further incubated with the drug for 2 h. The cell survival rate was determined using a conventional clonogenic assay. The effects of the treatments on the cell cycle were analyzed with a flow cytometric assay. Apoptosis after these treatments was also detected by an annexin V assay. Results: There were no significant differences in sensitivity to radiation or SN-38 treatment among these cell lines. The combined treatment of irradiation and SN-38 showed supraadditive effects in all four cell lines independent of their p53 status. Transient arrest in G2 with a decreased percentage of cells in both the S and G1 phases was observed 8 h after treatment with either SN-38 alone, radiation or their combination, regardless of the p53 status. No significant differences in frequency of apoptosis were observed between treatment and control groups in two cell lines with or without wild-type p53. Conclusion: The combination of irradiation and SN-38 treatment showed supraadditive effects in all four cell lines tested, and the p53 status did not play a role in the combination effect.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4919
    Keywords: hsp72 ; HSF ; phosphorylation ; H-7 ; protein kinase inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We investigated the effects of a protein kinase (PK) inhibitor, H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride), on the regulation of heat shock protein (hsp)72 gene expression in a human glioblastoma cell line (A-172) using a gel mobility-shift assay and Western blot analysis. Heat shock transcription factor 1 (HSF1) was phosphorylated immediately after heat treatment (44°C, 30 min) and the phosphorylation of HSF1 was suppressed by H-7. The increase in DNA binding ability of HSF1 to heat shock element (HSE) by heat shock was significantly suppressed by the addition of H-7 in a dose-dependent manner. Similarly, the accumulation of hsp72 by heat shock was suppressed by the addition of H-7 in a dose-dependent manner. Since H-7 is known to be a potent inhibitor of some PKs, especially calcium-dependent PK (PKC), cyclicAMP-dependent PK (PKA) and cyclicGMP-dependent PK (PKG), it is possible that the activation of HSF1 by phosphorylation and subsequent hsp72 gene expression are dependent on some of those PKs. The nature of H-7 as a non-specific inhibitor for PKs is discussed in relation to its availability for regulation of heat sensitivity of cells depending on cellular level of hsp72.
    Type of Medium: Electronic Resource
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