Inducible heat-shock protein 70 is involved in the radioadaptive response

Sang Hee Park, Su Jae Lee, Hee Yong Chung, Tae Hwan Kim, Chul Koo Cho, Seong Yul Yoo, Yun Sil Lee

Research output: Contribution to journalArticlepeer-review

87 Scopus citations

Abstract

The thermoresistant (TR) clone of radiation-induced fibrosarcoma (RIF) cells showed an adaptive response, i.e. a reduced effect, after exposure to a higher challenging dose (4 Gy) when the priming dose (1 cGy) was given 4 or 7 h earlier, but RIF cells did not. Since inducible Hsp70 expression was different in cells of these two cell lines, the role of inducible Hsp70 in the adaptive response was examined. When inducible Hsp70 was transfected into RIF cells, the adaptive response was acquired. Transfection of inducible Hsp70 to NIH 3T3 mouse embryo cells also conferred radioresistance to the cells as assayed by clonogenic survival, [3H]thymidine incorporation, and an ELISA cell death detection kit. An increased tendency for the induction of an adaptive response was also observed. Interestingly, basal levels of Ca2+- dependent and independent Pkc activities were increased by transfection with inducible Hsp70 compared to those of control vector cells. Irradiation with γ rays induced activation of Pkc within minutes in control vector cells, while transfection with inducible Hsp70 did not. Cellular redistribution to particulate fractions of Pkca, d and z after exposure γ rays also was not detected. Furthermore, radioresistance by transfection with inducible Hsp70, as tested by clonogenic survival, disappeared after pretreatment with Pkc inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), prolonged treatment with 12-O-tetra-decanoylphorbol-13-acetate (TPA), and GF109203X. Taken together, these data suggest that radioresistance inducible by Hsp70 is associated with an elevated level of Pkc activity. (C) 2000 by Radiation Research Society.

Original languageEnglish
Pages (from-to)318-326
Number of pages9
JournalRadiation Research
Volume153
Issue number3
DOIs
StatePublished - Mar 2000

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