Hsp70- and p53-reponses after heat treatment and/or X-irradiation mediate the susceptibility of hematopoietic cells to undergo apoptosis.
OBJECTIVE
The effect of heat treatment in combination with X-irradiation was examined with regard to expression of p53, a tumor suppressor gene product, and Hsp70, a heat-shock protein, in association with the occurrence of programmed cell death (apoptosis).


METHODS
Three hematopoietic cell lines (HSB2, HL60 and Kasumi-1), which differ in p53 status, were exposed to 42.5 degrees C during one hour and/or X-radiation (total dose 8 Gy). After exposure, both mRNA and protein expression levels of Hsp70 and p53 were investigated by real-time PCR (polymerase chain reaction) and Western blotting. Apoptosis was simultaneously analyzed by observation of cell morphology as well as flowcytometric determination of Annexin V binding to phosphatidylserine and propidium iodide exclusion.


RESULTS
Both HL60 and HSB2 cell lines with a low p53 status and a quick response to heat treatment with Hsp70 over-expression are less susceptible to heat-induced apoptosis compared to Kasumi-1 cells with wild-type p53 protein and no Hsp70 response. The combination of first applying X-irradiation followed by heat treatment resulted in the most effective induction of apoptosis due to impairment of the Hsp70 response in all three cell lines.


CONCLUSIONS
These results indicate that the Hsp70 response and p53 status mediate the susceptibility of hematopoietic cells to undergo heat-induced apoptosis. Therefore, these parameters can be used as markers to predict the effectiveness of hyperthermia in cancer treatment.
Nijhuis
E H A
EH
University of Twente, Faculty of Science and Technology, Department of Polymer Chemistry and Biomaterials, Institute of Biomedical Technology (BMTI), The Netherlands.
Poot
A A
AA
Feijen
J
J
Vermes
I
I
D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D005786:Gene Expression Regulation / Q000502:physiology / Q000528:radiation effects*; D016158:Genes, p53 / Q000502:physiology / Q000528:radiation effects*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism / Q000528:radiation effects*; D006413:Hematopoietic System / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D006358:Hot Temperature; D006801:Humans; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014965:X-Rays
D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger